Interdisciplinary Research for Printing and Packaging (Lecture Notes in Electrical Engineering, 896) 9811916721, 9789811916724

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Lecture Notes in Electrical Engineering 896

Pengfei Zhao · Zhuangzhi Ye · Min Xu · Li Yang · Linghao Zhang · Shu Yan   Editors

Interdisciplinary Research for Printing and Packaging

Lecture Notes in Electrical Engineering Volume 896

Series Editors Leopoldo Angrisani, Department of Electrical and Information Technologies Engineering, University of Napoli Federico II, Naples, Italy Marco Arteaga, Departament de Control y Robótica, Universidad Nacional Autónoma de México, Coyoacán, Mexico Bijaya Ketan Panigrahi, Electrical Engineering, Indian Institute of Technology Delhi, New Delhi, Delhi, India Samarjit Chakraborty, Fakultät für Elektrotechnik und Informationstechnik, TU München, Munich, Germany Jiming Chen, Zhejiang University, Hangzhou, Zhejiang, China Shanben Chen, Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, China Tan Kay Chen, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore Rüdiger Dillmann, Humanoids and Intelligent Systems Laboratory, Karlsruhe Institute for Technology, Karlsruhe, Germany Haibin Duan, Beijing University of Aeronautics and Astronautics, Beijing, China Gianluigi Ferrari, Università di Parma, Parma, Italy Manuel Ferre, Centre for Automation and Robotics CAR (UPM-CSIC), Universidad Politécnica de Madrid, Madrid, Spain Sandra Hirche, Department of Electrical Engineering and Information Science, Technische Universität München, Munich, Germany Faryar Jabbari, Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA Limin Jia, State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing, China Janusz Kacprzyk, Systems Research Institute, Polish Academy of Sciences, Warsaw, Poland Alaa Khamis, German University in Egypt El Tagamoa El Khames, New Cairo City, Egypt Torsten Kroeger, Stanford University, Stanford, CA, USA Yong Li, Hunan University, Changsha, Hunan, China Qilian Liang, Department of Electrical Engineering, University of Texas at Arlington, Arlington, TX, USA Ferran Martín, Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain Tan Cher Ming, College of Engineering, Nanyang Technological University, Singapore, Singapore Wolfgang Minker, Institute of Information Technology, University of Ulm, Ulm, Germany Pradeep Misra, Department of Electrical Engineering, Wright State University, Dayton, OH, USA Sebastian Möller, Quality and Usability Laboratory, TU Berlin, Berlin, Germany Subhas Mukhopadhyay, School of Engineering & Advanced Technology, Massey University, Palmerston North, Manawatu-Wanganui, New Zealand Cun-Zheng Ning, Electrical Engineering, Arizona State University, Tempe, AZ, USA Toyoaki Nishida, Graduate School of Informatics, Kyoto University, Kyoto, Japan Luca Oneto, Dept. of Informatics, Bioengg., Robotics, University of Genova, Genova, Genova, Italy Federica Pascucci, Dipartimento di Ingegneria, Università degli Studi “Roma Tre”, Rome, Italy Yong Qin, State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing, China Gan Woon Seng, School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore, Singapore Joachim Speidel, Institute of Telecommunications, Universität Stuttgart, Stuttgart, Germany Germano Veiga, Campus da FEUP, INESC Porto, Porto, Portugal Haitao Wu, Academy of Opto-electronics, Chinese Academy of Sciences, Beijing, China Walter Zamboni, DIEM - Università degli studi di Salerno, Fisciano, Salerno, Italy Junjie James Zhang, Charlotte, NC, USA

The book series Lecture Notes in Electrical Engineering (LNEE) publishes the latest developments in Electrical Engineering - quickly, informally and in high quality. While original research reported in proceedings and monographs has traditionally formed the core of LNEE, we also encourage authors to submit books devoted to supporting student education and professional training in the various fields and applications areas of electrical engineering. The series cover classical and emerging topics concerning:

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Pengfei Zhao Zhuangzhi Ye Min Xu Li Yang Linghao Zhang Shu Yan •

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Editors

Interdisciplinary Research for Printing and Packaging

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Editors Pengfei Zhao China Academy of Printing Technology Beijing, Beijing, China

Zhuangzhi Ye China Academy of Printing Technology Beijing, Beijing, China

Min Xu China Academy of Printing Technology Beijing, Beijing, China

Li Yang China Academy of Printing Technology Beijing, Beijing, China

Linghao Zhang China Academy of Printing Technology Beijing, Beijing, China

Shu Yan China Academy of Printing Technology Beijing, Beijing, China

ISSN 1876-1100 ISSN 1876-1119 (electronic) Lecture Notes in Electrical Engineering ISBN 978-981-19-1672-4 ISBN 978-981-19-1673-1 (eBook) https://doi.org/10.1007/978-981-19-1673-1 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

“2021 12th China Academic Conference on Printing and Packaging & Forum of Technology Integration Innovation Development”, one of the series “China Academic Conference on Printing and Packaging” which is mainly hosted by China Academy of Printing Technology, was held on December 11–12, 2021, in Beijing, China. The conference was co-hosted by China Academy of Printing Technology and Beijing Institute of Graphic Communication, and was organized by School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing Key Laboratory of New Technology of Packaging & Printing, Key Laboratory of Environmental Protection, Intelligence Technology for Printing Industry, Editorial Department of Digital Printing, and Printing Technology Professional Committee of Chinese Society for Imaging Science and Technology. By far, “China Academic Conference on Printing and Packaging (CACPP)” and its series of events have been held for twelve sessions and have already become the most influential academic exchange activities in printing and packaging fields in China. In the past five years, the printing industry adheres to the “green, digital, intelligent, integrated” development direction, and the industry continues to expand. In 2020, there were 5,708 enterprises above the scale of the printing industry involved in statistics, and their total revenue was 647.2 billion yuan, accounting for more than 60% of the total output value; the total profit accounted for more than 75%, with a significant increase in the level of intensification; the pace of change in digital integration accelerated, and the new industry showed strong leading vitality. Among them, scientific research and innovation played a leading role, and the industry has formed a multi-level scientific research force consisting of universities, research institutions, listed companies, innovative enterprises, etc., committed to the research of new technologies, new materials, new equipment, and new processes, and many scientific research achievements have emerged. These achievements will be reported and exchanged at the 2021 12th China Academic Conference on Printing and Packaging & Forum of Technology Integration Innovation Development.

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For this academic conference, we specially invited Professor Bowen Cheng, Vice President of Tianjin University of Science and Technology, Professor Linsen Chen of Soochow University, Professor Ningfang Liao of Beijing Institute of Technology and Ph.D. Lihui Wang, Professor and Chair of Sustainable Manufacturing of KTH Royal Institute of Technology to make keynote speeches on topics of high-performance nano-microfiber medical packaging materials and systematic innovation of three-dimensional nanoprinting, faithful color communication form imaging to display, human–robot collaboration for intelligent manufacturing, etc. We also invited Professor Wei Zhao of Shaanxi University of Science & Technology, Associate Professor Bangyong Sun of Xi’an University of Technology, Associate Professor Lijuan Liang of Beijing Institute of Graphic Communication, Associate Professor Zizhao Wu of Hangzhou Dianzi University, and Associate Professor Defu Lu of Hunan University of Technology respectively to give the main speeches as outstanding young scholars. At the same time, three panel discussion meetings were organized to conduct oral reports and academic exchanges on topics such as color science and image processing technology, digital media technology, mechatronics and information engineering technology, printing innovative materials, packaging innovative materials and testing technology. The conference received 190 papers this year, among which about 80 papers were selected to be published on Lecture Notes in Electrical Engineering (LNEE) (ISSN: 1876-1100) by Springer. Here we greatly acknowledge all the co-sponsors that offered great support for the conference, and they are the Printing Technology Association of China, Chinese Society for Imaging Science and Technology, School of Light Industry and Engineering of South China University of Technology, School of Printing and Packaging of Wuhan University, Faculty of Printing, Packaging Engineering and Digital Media Technology of Xi’an University of Technology, School of Light Industry Science and Engineering of Qilu University of Technology (Shandong Academy of Science), School of Media and Design of Hangzhou Dianzi University, College of Light Industry Science and Engineering of Tianjin University of Science and Technology, College of Communication and Art Design of University of Shanghai for Science and Technology, Light Industry College of Harbin University of Commerce, School of Mechanical Engineering of Jiangnan University, School of Light Industry & Chemical Engineering of Dalian Polytechnic University, School of Packaging & Material Engineering of Hunan University of Technology, College of Engineering of Qufu Normal University, College of Light Industry and Food Engineering of Nanjing Forestry University, College of Materials Science and Engineering of Beijing University of Chemical Technology, School of Material Science & Engineering of Zhengzhou University, School of Light Industry of Beijing Technology and Business University, School of Media and Communication of Shenzhen Polytechnic, Shanghai Publishing and Printing College, and College of Communications of Taiwan University of Arts.

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We would like to express our gratitude to the 54 experts from the fields of color, image, computer, material, machinery, and information for their strict reviewing and recommending papers for the conference with strict standards. We also thank Springer for offering us an international platform for publishing. We look forward to our reunion at 2022 13th China Academic Conference on Printing and Packaging. October 2021

Organization

2021 12th China Academic Conference on Printing and Packaging & Forum of Technology Integration Innovation Development Date December 11–12, 2021 Location Beijing, China

Sponsors China Academy of Printing Technology Beijing Institute of Graphic Communication

Support The Printing Technology Association of China Chinese Society for Imaging Science and Technology

Organizers School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication Beijing Key Laboratory of New Technology of Packaging & Printing Key Laboratory of Environmental Protection and Intelligence Technology for Printing Industry Editorial Department of Digital Printing Printing Technology Professional Committee, Chinese Society for Imaging Science and Technology

Supporters National Technical Committee 192 on Printing Machinery of Standardization Administration of China

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Co-sponsors College of Light Industry Science and Engineering, Tianjin University of Science and Technology Faculty of Printing, Packaging Engineering and Digital Media Technology, Xi’an University of Technology School of Light Industry Science and Engineering, Qilu University of Technology (Shandong Academy of Science) School of Light Industry and Engineering, South China University of Technology School of Media and Design, Hangzhou Dianzi University School of Printing and Packaging, Wuhan University State Key Laboratory of Modern Optical Instrumentation, Zhejiang University College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science & Technology Light Industry College, Harbin University of Commerce School of Light Industry & Chemical Engineering, Dalian Polytechnic University School of Packaging & Material Engineering, Hunan University of Technology College of Materials Science and Engineering, Beijing University of Chemical Technology School of Mechanical Engineering, Tianjin University of Commerce School of Light Industry, Beijing Technology and Business University School of Materials and Chemical Engineering, Henan University of Engineering College of Communication and Art Design, University of Shanghai for Science and Technology School of Material Science & Engineering, Zhengzhou University College of Engineering, Qufu Normal University College of Light Industry and Food Engineering, Nanjing Forestry University School of Mechanical Engineering, Jiangnan University Shanghai Publishing and Printing College School of Media and Communication, Shenzhen Polytechnic College of Communications, National Taiwan University of Arts

Conference Executive Committee Chairman Xueke Luo (President of Beijing Institute of Graphic Communication) Jinhong Gao (Secretary of the Party Committee of Beijing Institute of Graphic Communication) Pengfei Zhao (President of China Academy of Printing Technology)

Vice Chairman Zhongli Tian (Vice President of Beijing Institute of Graphic Communication) Zhuangzhi Ye (Vice President of China Academy of Printing Technology)

Organization

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Honorary Chairman Desen Qu (Former President of Beijing Institute of Graphic Communication) Tingliang Chu (Former President of China Academy of Printing Technology, Executive Vice Chairman of the Printing Technology Association of China) Wencai Xu (Former Vice President of Beijing Institute of Graphic Communication, Vice Chairman of the Printing Technology Association of China) Jialing Pu (Former Vice President of Beijing Institute of Graphic Communication, and Chairman of Chinese Society for Imaging Science and Technology)

Secretary-General Yuansheng Qi (Dean of School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication) Min Xu (Director of Industry Development Research Department, China Academy of Printing Technology)

Conference Academic Committee Chairman Deren Li (Academician of Chinese Academy of Sciences, Academician of Chinese Academy of Engineering, Academician of International Eurasian Academy of Sciences, Academician of New York Academy of Sciences, Academician of International Academy of Astronautics, Professor of Wuhan University, Director of State Key Laboratory of Information Engineering in Surveying, Mapping and Remote)

Vice Chairman Kefu Chen (Academician of Chinese Academy of Engineering, Professor of South China University of Technology, Director of Academic Committee of State Key Laboratory of Pulp and Paper Engineering) Jinping Qu (Academician of Chinese Academy of Engineering, Professor of South China University of Technology, Director of National Engineering Research Center of Novel Equipment for Polymer Processing, Director of the Key Laboratory for Polymer Processing Engineering of Ministry of Education) Guangnan Ni (Academician of Chinese Academy of Engineering, Researcher of Institute of Computing Technology Chinese Academy of Sciences, Board Chairperson of Chinese Information Processing Society of China) Songlin Zhuang (Academician of Chinese Academy of Engineering, Director and Professor of School of Optical-Electrical and Computer Engineering of University of Shanghai for Science and Technology, Optical Expert)

Commissioners Alexander Roos (Professor of Stuttgart Media University) Alexander Tsyganenko (Professor of Media Industry Academy)

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Organization

Anita Teleman (Doctor, Research Manager of Printing Solutions at the Research Institute Innventia, Sweden) Aran Hansuebsai (Doctor, Associate Professor of Chulalongkorn University) Bangyong Sun (Doctor, Associate Professor of Xi’an University of Technology) Benjamin Lee (Professor, Director of Department of Technology, California State University) Changqing Fang (Doctor, Professor of Xi’an University of Technology) Congjun Cao (Doctor, Professor of Xi’an University of Technology) Dongming Lu (Doctor, Professor of Zhejiang University) Eduard Neufeld (Doctor, Managing Director of Fogra Research Institute for Media Technologies) Fude Lu (Doctor, Lecturer of Hunan University of technology) Fuqiang Chu (Doctor, Professor of Qilu University of Technology (Shandong Academy of Science)) Guangxue Chen (Doctor, Professor of South China University of Technology) Guodong Liu (Doctor, Associate Professor of Shaanxi University of Science and Technology) Guorong Cao (Doctor, Professor of Beijing Institute of Graphic Communication) Haigen Yao (Professor of Shanghai Publishing and Printing College) Haiqiao Wang (Doctor, Professor of Beijing University of Chemical Technology) Haiyan Zhang (Professor of Xi’an University of Technology) Haoxue Liu (Doctor, Professor of Beijing Institute of Graphic Communication) Houbin Li (Doctor, Professor of Wuhan University) Howard E. Vogl (Visiting Professor of Rochester Institute of Technology) Jeroen Guinée (Doctor, Associate Professor of Leiden University) Jialing Pu (Doctor, Professor of Beijing Institute of Graphic Communication) Jimei Wu (Doctor, Professor of Xi’an University of Technology) Jinda Cai (Doctor, Professor of University of Shanghai for Science and Technology) Jinlin Xu (Professor of Xi’an University of Technology) Jinzhou Chen (Professor of Zhengzhou University) Jon Yngve Hardeberg (Doctor, Professor of Norwegian University of Science and Technology) Jose Maria Lagaron (Doctor, Professor, Leader and Founder of the Group Novel Materials and Nanotechnology for Food Related Applications at the Institute of Agrochemistry and Food Technology of the Spanish Council for Scientific Research) Junfei Tian (Doctor, Professor of South China University of Technology) Kaida Xiao (Doctor, Academic Fellow of University of Leeds) Kamal Chopra (Professor, President of All India Federation of Master Printers) Lihui Wang (Doctor, Professor of KTH Royal Institute of Technology) Lijie Wang (Professor of Shenzhen Polytechnic) Lijuan Liang (Doctor, Associate Professor of Beijing Institute of Graphic Communication) Linsen Chen (Professor of Suzhou University)

Organization

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Lixin Lu (Doctor, Professor of Jiangnan University) Luciano Piergiovanni (Professor of the Department of Food, Environmental and Nutritional Sciences, Faculty of Agricultural and Food Sciences, University of Milan) Luhai Li (Doctor, Professor of Beijing Institute of Graphic Communication) M. Ronnier Luo (Doctor, Professor of University of Leeds, Director of Color and Image Science Center) Maohai Lin (Doctor, Associate Professor of Qilu University of Technology (Shandong Academy of Science)) Martin Dreher (Doctor, Director and General Manager of DFTA Technology Center, Professor of the Hochschule der Medien (HdM)) Martti Toivakka (Doctor, Professor and Head of the Laboratory of Paper Coating and Converting at Åbo Akademi University) Mathias Hinkelmann (Doctor, Professor of Stuttgart Media University) Min Huang (Doctor, Professor of Beijing Institute of Graphic Communication) Ngamtip Poovarodom (Doctor, Associate Professor of Department of Packaging and Materials Technology of Faculty of Agro-Industry, Kasetart University) Ningfang Liao (Doctor, Professor of Beijing Institute of Technology) Patrick Gane (Doctor, Professor of Printing Technology at the School of Chemical Technology, Aalto University) Pengfei Zhao (Senior Engineer of China Academy of Printing Technology) Phil Green (Professor of Color Imaging, London College of Communication) Philipp Urban (Head of Emmy-Noether Research Group, Institute of Printing Science and Technology, Technische Universität Darmstadt) Pierre Pienaar (Professor, President of the World Packaging Organization) Punan Xie (Professor of Beijing Institute of Graphic Communication) Qiang Wang (Doctor, Professor of Hangzhou Dianzi University) Roger D. Hersch (Doctor, Professor of Computer Science and Head of the Peripheral Systems Laboratory at the Ecole Polytechnique Fédérale de Lausanne (EPFL)) Ruping Liu (Doctor, Professor of Beijing Institute of Graphic Communication) Shaozhong Cao (Doctor, Professor of Beijing Institute of Graphic Communication) Shijun Kuang (Consultant Engineer of China National Pulp and Paper Research Institute, Chief Engineer) Shisheng Zhou (Doctor, Professor of Xi’an University of Technology) Songhua He (Doctor, Professor of Shenzhen Polytechnic) Stephen W. Bigger (Doctor, Professor, Vice President of Faculty of Engineering and Science of Victoria University) Takashi Kitamura (Doctor, Professor of Graduate School of Advanced Integration Science, Chiba University) Thomas Hoffmann-Walbeck (Professor of the Faculty of Print and Media Technology, Stuttgart University of Media) Tingliang Chu (Professorial Senior Engineer of China Academy of Printing Technology) Wanbin Pan (Doctor, Associate Professor of Hangzhou Dianzi University)

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Organization

Wei Wang (Doctor, Professor of Beijing Institute of Graphic Communication) Wei Wu (Doctor, Professor of Wuhan University) Wei Zhao (Doctor, Professor of Shaanxi University of Science & Technology) Wencai Xu (Professor of Beijing Institute of Graphic Communication) Xianfu Wei (Doctor, Professor of Beijing Institute of Graphic Communication) Xiaochun Li (Doctor, Professor of Henan University of Engineering) Xiaohui Wang (Doctor, Professor, Deputy Director of State Key Laboratory of Pulp and Paper Engineering, South China University of Technology) Xiaoxia Wan (Doctor, Professor of Wuhan University) Xiufeng Ma (Professor of Qufu Normal University) Xiulan Xin (Doctor, Professor of Beijing Technology and Business University) Xiuping Zhao (Professor of Tianjin University of Science and Technology) Xuesong Mei (Doctor, Professor from Xi’an Jiaotong University) Yadong Yin (Doctor, Professor of University of California, Riverside) Yan Wei (Doctor, Professor of Tsinghua University, Beijing Institute of Graphic Communication) Yanlin Song (Doctor, Professor of Institute of Chemistry, Chinese Academy of Sciences) Yingquan Zou (Doctor, Professor of Beijing Normal University) Yuansheng Qi (Doctor, Professor of Beijing Institute of Graphic Communication) Yuemin Teng (Professor of Shanghai Publishing and Printing College) Yunfei Zhong (Professor of Hunan University of Technology) Yungcheng Hsieh (Doctor, Professor of National Taiwan University of Arts) Yunzhi Chen (Doctor, Professor of Tianjin University of Science and Technology) Yuri Andreev (Head of Moscow State University of Printing Arts) Zhen Liu (Professor of University of Shanghai for Science and Technology) Zhengning Tang (Doctor, Professor of Jiangnan University) Zhicheng Sun (Doctor, Professor of Beijing Institute of Graphic Communication) Zhihui Sun (Professor of Harbin University of Commerce) Zhijian Li (Doctor, Professor of Shaanxi University of Science and Technology) Zhijiang Li (Doctor, Associate Professor of Wuhan University) Zizhao Wu (Doctor, Associate Professor of Hangzhou Dianzi University)

Reviewers Bangyong Sun (Doctor, Associate Professor of Xi’an University of Technology) Chen Chen (Doctor, Postdoctoral of South China University of Technology) Congjun Cao (Doctor, Professor of Xi’an University of Technology) Erhu Zhang (Doctor, Professor of Xi’an University of Technology) Fazhong Zhang (Doctor, Engineer of China Academy of Printing Technology) Fuqiang Chu (Doctor, Professor of Qilu University of Technology (Shandong Academy of Science)) Gaimei Zhang (Doctor, Professor of Beijing Institute of Graphic Communication) Guangxue Chen (Doctor, Professor of South China University of Technology)

Organization

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Haihua Zhou (Doctor, Associate Researcher of Institute of Chemistry, Chinese Academy of Sciences) Haiqiao Wang (Doctor, Professor of Beijing University of Chemical Technology) Hongwei Xu (Doctor, Associate Professor of Xi’an University of Technology) Jinda Zhu (Doctor, Teacher of Hebei University of Science & Technology) Jing Liang (Lecturer of Dalian Polytechnic University) Junfei Tian (Doctor, Professor of South China University of Technology) Junyan Huang (Master, Professor of Dalian Polytechnic University) Li An (Doctor, Teacher of Beijing Institute of Graphic Communication) Lijiang Huo (Doctor, Professor of Dalian Polytechnic University) Linghua Guo (Doctor, Professor of Shaanxi University of Science & Technology) Liqiang Huang (Doctor, Professor of Tianjin University of Science and Technology) Maohai Lin (Doctor, Associate Professor of Qilu University of Technology (Shandong Academy of Science)) Mengmeng Wang (Doctor, Associate Professor of Jiangnan University) Min Huang (Doctor, Professor of Beijing Institute of Graphic Communication) Minchen Wei (Doctor, Associate Professor of the Hong Kong Polytechnic University) Ming Zhu (Doctor, Associate Professor of Henan Institute of Engineering) Minghui He (Doctor, Associate researcher of South China University of Technology) Na Wei (Doctor, Professor of Tianjin Vocational Institute) Qiang Liu (Doctor, Associate Professor of Wuhan University) Qiang Wang (Doctor, Professor of Hangzhou Dianzi University) Shaozhong Cao (Doctor, Professor of Beijing Institute of Graphic Communication) Shi Li (Doctor, Teacher of Hangzhou Dianzi University) Shibao Wen (Doctor, Associate Professor of Qingdao University of Science and Technology) Shuangyang Li (Doctor, Associate Professor of Beijing Technology and Business University) Wei Wu (Doctor, Professor of Wuhan University) Weibing Gu (Doctor, Senior Engineer of Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Science) Xianfu Wei (Doctor, Professor of Beijing Institute of Graphic Communication) Xiaozhou Li (Doctor, Associate Professor of Qilu University of Technology (Shandong Academy of Science)) Xinghai Liu (Doctor, Associate Professor of Wuhan University) Xiulan Xin (Doctor, Professor of Beijing Technology and Business University) Xue Gong (Doctor, Associate Professor of Harbin University of Commerce) Xuying Liu (Doctor, Professor of Zhengzhou University) Yalin Miu (Doctor, Associate Professor of Xi’an University of Technology) Yanan Liu (Doctor, Engineer of Beijing Senior Expert Technology Center Chinese Academy of Sciences) Yaohua Yi (Doctor, Professor of Wuhan University)

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Organization

Yi Fang (Doctor, Teacher of Beijing Institute of Graphic Communication) Yuanlin Zheng (Doctor, Associate Professor of Xi’an University of Technology) Yufeng Wang (Doctor, Senior Engineer of Tianjin University of Science and Technology) Yunzhi Chen (Doctor, Professor of Tianjin University of Science and Technology) Zhanjun Si (Professor of Tianjin University of Science and Technology) Zhen Huang (Doctor, Professor of Tianjin University of Commerce) Zhengjian Zhang (Doctor, Associate Professor of Tianjin University of Science and Technology) Zhicheng Sun (Doctor, Associate Professor of Beijing Institute of Graphic Communication) Zhijiang Li (Doctor, Associate Professor of Wuhan University) Zhuang Liu (Doctor, Professor of Harbin University of Commerce) Zhuofei Xu (Doctor, Teacher of Xi’an University of Technology)

Contents

White Balance Conversion Method of Different Camera Based on Triangle Affine Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hao Huang, Ningfang Liao, Changming Zhao, and Qiumei Fan Study of Color Reproduction Based on Different Scanners . . . . . . . . . . Juan Bai and Maohai Lin

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The Impact of Color Matching Functions on the Observer Metamerism and a Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyu Shi and Ming Ronnier Luo

14

Influences of Reference Colors on Cluster Analysis of Color Matching Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yu Wang, Chunjie Shi, Yu Li, Yu Liu, and Min Huang

20

Evaluation of Color Matching Functions with Neutral Metamerism Printed Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yu Li, Yu Wang, Yuxin Chen, Yu Liu, and Min Huang

25

Multispectral Data Optimization Using Loop Algorithm to Remove Redundant Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Qian Cao, Junfeng Li, Xiaozhou Li, and Jun Liu

30

How Much Time is Required to Achieve a Stable Chromatic Adaptation? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hui Fan, Ming Ronnier Luo, and Yuechen Zhu

36

Effects of Ambient Illuminance and Luminance Contrast on Visual Comfort for Reading on a Mobile Device . . . . . . . . . . . . . . . . . . . . . . . . Yu Liu and Ming Ronnier Luo

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Evaluation of Primaries for Display Colourimetry . . . . . . . . . . . . . . . . . Lihao Xu and Ming Ronnier Luo

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Contents

Color Reproduction Analysis for 3D Printing Based on Photosensitive Resin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Xiaomeng Han, Yijie Ren, Yibo Wang, Jinze Wang, Yifan Xiong, Guangyuan Wu, and Xiaozhou Li Optical Properties of Periodic Columnar Structures with Structural Colors Using Pattern Transfer Technology . . . . . . . . . . . . . . . . . . . . . . Xiaoxue Hu, Yeqi Wang, Min Huang, Yu Li, Yu Wang, Junxiao Lu, and Xiu Li

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Study on Color Consistency Reproduction Method of Decorative Material Surface Based on UV Inkjet Printing . . . . . . . . . . . . . . . . . . . Yan Liu and Quanhui Tian

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Mural Inpainting Method Based on Deep Convolutional Generative Adversarial Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wenqian Yu, Zhibo Hu, Liqin Cao, and Zhijiang Li

71

Pencil Sketch Generation Based on Stroke Density and Texture . . . . . . Debiao Yang and Aibin Huang

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Analysis and Optimization of the Point Cloud Accuracy of the 3D Laser Scanner Based on the Surface Characteristics of the Object . . . . Yaoshun Yue and Maohai Lin

86

Medical Image Denoising Method Based on Total Variational Model and Adaptive Wavelet Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Saqing Wang, Aibin Huang, Mengmeng Zhang, and Caifeng Liu

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Image Contrast Enhancement Algorithm Based on PSO for Batch Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mihang Wang, Aibin Huang, and Caifeng Liu

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Adaptive Partition Total Variation Algorithm for Medical Ultrasound Image Denoising . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Mengmeng Zhang, Aibin Huang, Ruyu Zhai, and Saqing Wang Study on Sharpness Evaluation Method of Vehicle Imaging System . . . 113 Chunzhi Xu, Jing Cao, Anda Yong, Zhuoran Zhang, and Hongli Liu Study on the Evaluation Method of the Clarity of Critical Areas of Digital Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Hangning Wang, Qiang Wang, Chen Shao, and Ruze Zhuang Scanned Document Image Enhancement Method Based on Lightweight Convolutional Neural Networks . . . . . . . . . . . . . . . . . . . 128 Kuang Yin, Hongbin Wang, Lianhong Zhong, Jianbin Ye, Yuan La, and Zhijiang Li

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A Halftone Blind Watermark to Resist Print-and-Scan and Be Detected by BP Neural Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Yehong Chen, Qing Wang, Yunhui Luo, and Chaojun Wu Fire Detection Based on YOLOv4 Baseline . . . . . . . . . . . . . . . . . . . . . . 143 Wanting Wang, Qing Wang, and Yehong Chen Computational Holographic Displays and Their Application in the Printing Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Congcong Jiang and Qing Wang Screw Missing Detection Based on MSER Algorithm . . . . . . . . . . . . . . . 155 Jian Fang, Kuang Yin, Hongbin Wang, Wenxiong Mo, Yu Qin, and Zhijiang Li Making of Children’s Bed Brochure Based on Augmented Reality . . . . 163 Xuezhao Zhang, Zhanjun Si, and Yuanxin Li Study on the Development of Inkjet Imaging Digital Printing Technology Based on Patent Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Gaosheng He and Yan Li Research on the Hi-Fi Reproduction Method of Oil Painting . . . . . . . . . 180 Liang Zheng, Chunmei Li, and Zhangying Jin Influence of Inkjet Printing Process on Printing Quality . . . . . . . . . . . . 186 Linhong Huang, Beiqing Huang, and Xianfu Wei Research on Preparation of Microstructure Surface Ultrasensitive Pressure Sensor Electrode Based on Inkjet Printing . . . . . . . . . . . . . . . 194 Yang Zhang, Fuqiang Chu, and Chen Chen Study on Process Parameters of Ink-Jet Printing Perovskite Solar Cell Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 Lei Wang, Beiqing Huang, Yingqun Qi, Ding Jia, Xianfu Wei, Hui Wang, and Weimin Zhang Application Research of 3D Printing Technology in Braille . . . . . . . . . . 207 Chunmei Li, Liang Zheng, and Ying Xiao Creative Lock Design Research Based on 3D Printing Technology . . . . 214 Yingmei Zhou and Junwei Qiao Study on Exposure Characteristics of Ultraviolet (UV) Light-Emitting Diode (LED) for Platemaking of Flexopress . . . . . . . . . . . . . . . . . . . . . . 220 Quanhui Tian, Yan Liu, and Huaiming Wang Effect of Paper Properties on Ink Transfer Properties . . . . . . . . . . . . . . 228 Yongjian Wu, Beiqing Huang, Xianfu Wei, and Hui Wang

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Application of Printed Electronic Technology in Flexible Tactile Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 Yingying Xiao, Mengzhu Wang, Huiling Zhang, Huiqing Zhao, Dan Zhao, and Ruping Liu Fabrication of 3D Supercapacitors Based on Direct-Write Printing Graphene Oxide/Carbon Nanotube Composite Ink . . . . . . . . . . . . . . . . 243 Chen Chen, Fuqiang Chu, and Yang Zhang Study on Preparation and Property of Inorganic Alternating Current Electroluminescence Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Yibin Liu, Zhicheng Sun, Hengyuan Zhang, Jiangsen Hu, and Furong Li Preparation of PEDOT:PSS Film-Forming and Electrochromic Devices Based on Flexography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 Zijian Wang, Guodong Liu, and Ling Zheng Sealing Optimization of Food Pillow Packaging with Instant Noodles as a Typical Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 Ruizhe Wang, Yuansheng Qi, Xin Pei, Qiaole Song, Zhaoyan Li, and Zhihan Zhang Optimization of Preparation Process of Paper-Based Colorimetric Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 Furong Wu, Yuan Zhang, Shaoyun Huang, Jinli Li, Rongrong Zhang, and Qingping Yi Research of Structural Parameters on Mechanical Properties of Honeycomb Paperboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Jingjing Hu, Xiaoli Song, Fayi Hao, Zhengyi Li, Gaimei Zhang, Zhiqi Zhu, and Jing Cheng Structural Parameters Design and Study on the Static Cushioning Performance of the Porous Materials Made of Paper with Diamond Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 Xiaoli Song, Gaimei Zhang, Han Xiang, Jingjing Hu, and Hao Yu Inactivation Efficacy and Applications of Gliding Arc Discharge Plasma in Fresh Pork Meat Preservation . . . . . . . . . . . . . . . . . . . . . . . . 291 Yidan Wang, Xueying Wang, Lubin Cui, Yunjin Sun, Jun Wu, and Fuqiang Qiao Design of a Single Chip HF-UHF Dual-Band RFID Tag Antenna . . . . . 301 Zhao Yang, Yuan Zhang, Lei Zhu, Lin Shen, Yanping Du, and Chaohui Yu Structure and Control Strategy Design of Wide-Format Ink-Jet Printing Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 Taotao Chen, Yuansheng Qi, Libo Dong, Su Gao, Taifen Bao, and Rui Zhu

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Study on Influence of Four Various Structure Static Mixers on Mixing Effect During Solvent-Less Compound Mixing . . . . . . . . . . . . . . . . . . . . 316 Hongwei Xu, Zhaohua Ma, Luofan Liu, Xiao Xu, Zhicheng Xue, and Darun Xi Kinematics Simulation and Material Delivery Trajectory Planning of Industrial Robot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 Guirong Dong, Pihong Hou, Ling Wu, Jijun Luo, and Shisheng Zhou A Screening Method for Dangerous Models of 3D Printed Bionic Artificial Vertebral Bodies - Finite Element Analysis . . . . . . . . . . . . . . . 332 Peng Li, Bowen Ren, Kun Hu, Zongwen Yang, Zhenchuan Han, Guifeng Zhang, and Bo Zhao Design of Interactive Customization System for Plastic Packaging Printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 Wenjie Yang and Xiujie Chen Research on Simulation Method of Typical Parts Production Line of Printing Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 Lirong Shao, Yuansheng Qi, Yanqiang Ma, Su Gao, Ximu Make, and Shunsheng Guo Study of Smart Storage Location Optimization Algorithm with Recommendation Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358 Ruyu Zhai, Aibin Huang, Mengmeng Zhang, and Caifeng Liu An Express Transportation Monitoring System Based on S-CNN . . . . . 364 Lei Huang, Yuan Zhang, Lei Zhu, Yanping Du, and Ao Ding Research on Suitability and Material Characteristics of Inkjet Printing Based on Xuan Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 Jinglin Ma, Qi Zeng, and Rui Kong Preparation and Regulation Mechanism of Rape Straw Nano Cellulose Based on Ozone Pretreatment . . . . . . . . . . . . . . . . . . . . . . . . . 376 Yong Lv, Linna Shao, Ci Song, and Jie Gao Cyan Cationic-Initiated Photocurable Material with High Curing Rate for UV-LED Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 Qi Lu, Xianfu Wei, Ting Zhu, Beiqing Huang, and Hui Wang Preparation of Highly Hydrophilic Aluminum Pigment by DoubleLayer Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 Liuxin Zhang, Beiqing Huang, Xianfu Wei, and Hui Wang Preparation and Properties of High Coating Rate Phase Change Microcapsules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 Qingqing Zhang, Zhicheng Sun, Xiaoyang Du, Gongming Li, and Zhitong Yang

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Preparation and Particle-Size Analysis of Small-Scale Thermal Expansion Microcapsules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 Zhenzhen Li, Zhicheng Sun, Gongming Li, and Zhitong Yang Design of Chlorophyll Ink and Its 2D Printing Applications . . . . . . . . . 406 Hongxia Wang, Ludan Hu, Liang Ma, and Yuhao Zhang Study on Preparation and Performance of Thermal Expansion Fluorescent Ink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 Zhitong Yang, Zhich eng Sun, Zhenzhen Li, and Gongming Li Preparation and Printing Application of Sound-Absorbing Ink . . . . . . . 416 Gongming Li, Zhicheng Sun, Xiaoyang Du, and Qingqing Zhang Preparation and Conductive Properties of Thiophene Inks . . . . . . . . . . 421 Xu Li, Lulu Xue, Shuping Gao, Xiangjun Guo, Hao Qi, Luhai Li, Meijuan Cao, Qinshuang Fang, Zhicheng Sun, Yonggang Yang, Lixin Mo, and Ruping Liu Research on Adhesion of UV Gravure Ink on PET Film . . . . . . . . . . . . 427 Chen Zhang, Beiqing Huang, Xianfu Wei, and Hui Wang Effect of Kaolinite’s Addition to Inking Oil on Printability of Water-Based Inks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435 Tao Hu, Zehui Zhong, Jiaying Zhong, Peng Gao, Fanqi Zeng, and Zijun Yuan Comparative Study on the Retort Resistance and Color Reproduction of Water-Based Ink on Paper and Plastic Film . . . . . . . . 443 Tao Hu, Zehui Zhong, Jiaying Zhong, Peng Gao, Fanqi Zeng, and Zijun Yuan Preparation and Research Progress of Cellulose-Based Transparent Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 Xin Li, Ling Cai, and Guangxue Chen Biocomposites Based on Spent Coffee Grounds and Application in Packaging: Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 Yiyu Chen, Qiongyang Li, Cheng Feng, Yuwei Hu, Yutao Liu, and Junfei Tian Preparation of Polymer Latex Containing Infrared Dye and Its Application to the Preparation of Computer to Plate Precursors . . . . . . 462 Li An, Hongli Zhang, Kunbi Qin, Chunxing Ren, and Zhongxiao Li Development of Solution-Processed Organic Semiconductor Thin Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 Wenjuan He, Suyun Wang, Beiqing Hang, Xianfu Wei, and Lijuan Liang

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Preparation of a Fluorinated Latex via RAFT Surfactant-Free Emulsion Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480 Zhongxiao Li, Hongli Zhang, Hanyu Cai, and Li An Study on Doping Modification of Pyrrole by Electrochemical Polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487 Huiqing Zhao, Yue Shi, Huiling Zhang, Mengzhu Wang, Yingying Xiao, and Ruping Liu Synthesis of a Novel Donor-Acceptor Dimer Discotic Liquid Crystal and Its Liquid Crystal Properties . . . . . . . . . . . . . . . . . . . . . . . 493 Xinran Zhang, Ruijuan Liao, Yi Fang, Chunxiu Zhang, Xinyue Zhao, Chenhui Wei, Mengfei Wang, Zhengran Wang, Lina Zhang, and Ao Zhang Preparation of Patterned Stretchable Conductor with High Performance Based on LMNPs and Silver Flakes . . . . . . . . . . . . . . . . . 498 Qingfang Zhang, Zhiqing Xin, Meijia Yan, Min Huang, Xiu Li, Yi Fang, Yaling Li, Lixin Mo, Jinzhao Yue, Cheng Xu, Ruoyin Ren, Linxinzheng Guo, and Luhai Li Application of Gel Electrolyte Based on PEDOT:PSS for Printable Dye-Sensitized Solar Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506 Jinyue Wen, Yibin Liu, Haoyu Tao, Yaling Li, and Zhicheng Sun High-Performance Flexible Photodetector with Two-Dimensional Graphene Heterostructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 Mengzhu Wang, Yingying Xiao, Huiqing Zhao, Huiling Zhang, Dan Zhao, and Ruping Liu Research Progress on Novel Structures of Flexible Memristor Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518 Huiling Zhang, Huiqing Zhao, Mengzhu Wang, Yingying Xiao, Dan Zhao, and Ruping Liu Research Progress of Glucose Sensor Suitable for 3D Printing . . . . . . . 523 Kun Hu, Linxinzheng Guo, Haibo Wang, Jundong Wang, Weiwei Sun, and Kunlan Wang Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531

White Balance Conversion Method of Different Camera Based on Triangle Affine Transform Hao Huang(B) , Ningfang Liao, Changming Zhao, and Qiumei Fan State Key Discipline Laboratory of Color Science and Engineering, School of Optics and Photonics, Beijing Institute of Technology, Beijing, China [email protected]

Abstract. Multi-camera imaging system, with its unique advantages, is widely used in smart phones, vehicles, drones and other systems. However, there will be significant differences in white balance when imaging the same scene due to the different optical characteristics and field of view between different cameras. In this paper, a camera white balance conversion method based on triangle affine transformation is proposed. Two different cameras are used to image the same Digital SG ColorChecker. The triangle affine transformation method is used to convert the white balance decision point of one camera to the other camera using the color information after imaging. The results show that using the method in this paper can improve the consistency of the white balance in the multi-camera imaging systems and improve the user experience. Keywords: Camera · White balance · Triangle affine transformation

1 Introduction Image contains rich information. With the development of imaging technology, the way people obtain images is changing. Various image devices are gradually applied. From the perspective of the color of the resulting image, digital cameras can be divided into true-color digital camera, pseudo-color digital camera, false-color digital camera, and black-and-white camera. Among them, true color digital cameras are most widely used, and are generally called digital color cameras [1]. In the imaging process of a color camera, the important role of white balance is to restore the images taken in different color temperature scenes as much as possible to the colors that the human eyes feel when they are directly perceived [2]. The white balance algorithm is a key technology in the digital color camera imaging process and is used differently depending on the environment. Commonly used white balance algorithms are the gray world method [3] using the gray world model and the perfect reflection method [4] using the white point hypothetical model. In order to reduce the influence of color blocks on white balance gain, standard weighting method [5] and edge white point method [6] using edge detection model are proposed.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 1–7, 2022. https://doi.org/10.1007/978-981-19-1673-1_1

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Existing multi-camera imaging systems mostly use the same white balance algorithm for different cameras. However, due to the differences in spectral transmittance, focal length and field of view of different cameras, the statistical points used for the correction of white balance algorithm are significantly different when shooting the same scene. In order to ensure that there is no obvious change in the white balance when switching cameras, one solution is to provide the white balance calculation result of one camera to other cameras through calculation. For this reason, it is necessary to find the conversion relationship of white balance decision points between the cameras according to the hardware characteristics of the cameras. This paper starts from the camera hardware and uses different cameras to image the same Digital SG ColorChecker whose color distribution is uniform and includes most of the colors in the color gamut. The triangle affine transform is used to transform the white balance decision point of one camera to the other camera in the two-dimensional color space based on the chromaticity information after imaging. The experimental results show that the white balance correction using the white balance decision points calculated by the conversion method in this paper can improve the consistency of the white balance and avoid obvious color sudden changes.

2 Method 2.1 Typical White Balance Algorithm The typical white balance algorithm is based on the gray world hypothesis which assumes that the average values of the three channels R, G and B tend to be the same gray value for an image with normal illumination, good noise control and rich colors. As shown in Eq. (1), R, G and B represent the channel mean value of the final output image. K is the mean value of the channel. For the white balance algorithm, the three channels are adjusted independently. Currently CCD and CMOS sensors usually use Bayer filter to obtain color information in the scene. Due to the special structure of Bayer filter, the green information in the scene is more sensitive, which is similar to the photosensitive characteristics of human eyes. Therefore, the value of channel G is generally used as a reference for white balance correction. The gain of G channel is often maintained as 1. And the relationship of Eq. (1) is satisfied by adjusting the white balance gain of R channel and B channel. Rout = G out = Bout = K So, the gain of the three channels is calculated as follows:  ⎧ ⎨ GainR = K R GainG = K G = 1 ⎩ GainB = K B

(1)

(2)

When the color distribution of the scene is not all gray, the image is divided into several sub blocks, and the average value of R/G and B/G in each block is calculated, and then marked out in the coordinate system. The weighted algorithm is used to find the value of R/G and B/G at the final decision point of white balance. Finally, the reciprocal

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of the decision point is used as the final white balance gain. The final output of each pixel of the image is shown in Eq. (3). ⎧ ⎪ ⎨ Rout = GainR · R(i, j) Gout = GainG · G(i, j) (3) ⎪ ⎩ Bout = GainB · B(i, j) 2.2 Affine Transformation of White Balance Decision Point The conversion method uses the Digital SG ColorChecker to calibrate the color data. The Digital SG ColorChecker target includes the colors from the standard ColorChecker target, many of which represent natural objects. And gray scale steps provide accurate control of camera balance to maintain a neutral aspect, regardless of light source. Figure 1 shows the data on RAW after the camera shoots the Digital SG ColorChecker. The chromaticity information of the 140 color patches is plotted in the [R/G, B/G] color space.

Fig. 1. Camera RAW data and distribution in the [R/G, B/G] color space

In Euclidean geometry, affine transformation is a geometric transformation that preserves lines and parallelism (but not necessarily distances and angles). More generally, affine transformation is an automorphism of an affine space, that is, a function which maps an affine space onto itself while preserving both the dimension of any affine subspaces and the ratios of the lengths of parallel line segments. Consequently, sets of parallel affine subspaces remain parallel after an affine transformation. Affine transformation does not necessarily preserve angles between lines or distances between points, though it does preserve ratios of distances between points lying on a straight line. All triangles and parallelograms can be affine transformed to other triangles and parallelograms. The affine transformations without translation or with a translation of zero can be described by the following transformation matrix.      ab x x = (4) y cd y

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The constraints of a, b, c and d correspond to different transformations, and all affine transformations excluding translation are linear transformations. The characteristic is that the position of the origin remains unchanged and the result of multiple linear transformations is still a linear transformation. In order to cover translation, homogeneous coordinates are introduced, and one dimension is added on the basis of the original two-dimensional coordinates, as shown in Eq. (5). ⎡ ⎤ ⎡ ⎤⎡ ⎤ ⎡ ⎤ abc x x abc ⎣ y ⎦ = ⎣ d e f ⎦⎣ y ⎦, M = ⎣ d e f ⎦ (5) 1 001 1 001 All affine transformations can be described by the matrix M, and the different fundamental transformations correspond to different constraints of a, b, c, d, e and f. Therefore, the transformation matrix of affine transformation has 6 degrees of freedom. In this paper, the least square method is used to calculate the matrix M.

Fig. 2. Typical 24 color patches color distribution of the two cameras under A light

Figure 2 shows the color distribution of the typical 24 color patches after the two cameras shoot the Digital SG ColorChecker under A light. It can be seen that because the characteristics of the two cameras are significantly different, the landing points when shooting the same color patch are different. After the two cameras image the same SG ColorChecker, the chromaticity information coordinates of each camera for 140 color patches in the chart can be obtained. From this, the position relationship of two cameras on each color patch can be established. In the shooting process, one camera’s white balance decision point can be obtained in the [R/G, B/G] color space. And the three color patches closest to the decision point can be found according to the chromaticity information of 140 color patches. Thus, we can get the position of another camera about the three color patches. Thus, the correspondence between two triangles can be established. Using the six points, the white balance decision point of one camera can be converted to another camera by triangular affine transformation. As shown in Fig. 3, if the white balance decision point D of camera1 falls in the triangle formed by ABC, the triangle formed by the corresponding three color patches of

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A B C in camera 2 can be found. Knowing the coordinates of the ABCA B C points, the affine transformation matrix M can be calculated using Eq. (5), and thus the coordinates of the white balance decision point D corresponding to camera 2 can be calculated.

Fig. 3. Camera RAW data and distribution in the [R/G, B/G] color space

3 Experiment and Results The camera used in the experiment are Samsung HMX and Canon 5DM4. From Fig. 4, it can be seen that the camera spectral sensitivities response of the two cameras is quite different. During the experiment, Digital SG Colorchecker was shot under different light sources (D65, TL84, A, H, from high color temperature coverage to low color temperature) in SpectralLight QC. Then the distribution of color patches in the [R/G, B/G] color space under different light sources were established.

Fig. 4. Spectral sensitivities of the camera

During the experiment, the conversion matrix was calculated using the data under the corresponding color temperature above according to the actual color temperature of

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the shooting environment. The experiment includes objective tests and subjective tests in the laboratory. Canon 5DM4 was selected as the target camera and Samsung HMX as the verification camera. The calibration results were evaluated by measuring the difference of white balance between Samsung HMX and Canon 5DM4. The correction results were evaluated using Eq. (6).

       r g HMX b g HMX ,   (6) [a, b]=    r g 5DM 4 b g 5DM 4 Since the 21st color block is neutral gray, it can be used to evaluate the white balance result. Where (r/g)5DM4 and (b/g)5DM4 are the color ratios of the 21st color patch on the ColorChecker Classic when the Canon 5DM4 actually shoots the scene, (r/g)HMX and (b/g)HMX are the ratios of the corresponding 21st color patch on the ColorChecker of the pictures taken by Samsung HMX using the white balance results calculated by the conversion matrix. The closer the values of a and b are to 1, the better the consistency of the white balance. In the experiment, the subjective scenes were shot in laboratory, indoors and outdoors. And then the consistency of the white balance can be analyzed. The 16 test scenes are shown in Fig. 5. Since the optical characteristics of the two cameras are different, color characterization was done for both cameras at different color temperatures to obtain the

Fig. 5. The 16 different test images

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CCM (Color correction matrix) before the experiment to ensure the accuracy of color reproduction. In the experiment, the corresponding CCM is used based on the color temperature calculated from the final white balance. The ratios of a and b calculated from 16 test images are shown in Table 1. From the table, it can be seen that the maximum and minimum ratios of a and b in are 1.122 and 0.969. The values are acceptable. Subjectively, the color consistency of images is not significantly different. There is no obvious difference from subjective observation, and it is within the acceptable range. Table 1. The result of 20 different test images Image 1

2

3

4

5

6

7

8

a

0.989 0.984 1.101 1.120 0.972 1.068 1.116 1.047

b

1.011 0.989 1.002 0.986 0.982 1.121 0.972 0.987

Image 9

10

11

12

13

14

15

16

a

0.975 1.014 1.036 1.095 1.071 0.972 1.098 1.122

b

1.017 1.051 1.108 0.969 1.081 1.103 0.998 1.001

4 Conclusions White balance algorithm plays an important role in digital cameras. In order to ensure the consistency of white balance of multi camera, a camera white balance conversion method based on triangle affine transformation is proposed. Objective scenes are set to verify the conversion results of the algorithm. And there is no obvious difference subjectively. The results show the method this paper proposed can improve the white balance consistency of different cameras. It can improve image quality and user experience. Acknowledgements. This work is supported by National Natural Science Foundation of China (Grant number: 61975012).

References 1. Zhang, Z., Zhang, J.: Digital Photogrammetry. Wuhan University Press, Wuhan (2012) 2. Fairchild, M.D.: Color Appearance Models. Wiley, Hoboken (2013) 3. Liu, Y.C., Chan, W.H., Chen, Y.Q.: Automatic white balance for digital still camera. IEEE Trans. Consum. Electron. 41(3), 460–466 (1995) 4. Kim, S., Kim, W., Kim, S.D.: Automatic white balance based on adaptive feature selection with standard illuminants. In: 2008 15th IEEE International Conference on Image Processing, pp. 485–488. IEEE (2008) 5. Gijsenij, A., Lu, R., Gevers, T.: Color constancy for multiple light sources. IEEE Trans. Image Process. 21(2), 697–707 (2011) 6. Lin, J.: An automatic white balance method based on edge detection. In: 2006 IEEE International Symposium on Consumer Electronics, pp. 1–4. IEEE (2006)

Study of Color Reproduction Based on Different Scanners Juan Bai1,2 and Maohai Lin1,2(B) 1 Key Laboratory of Green Printing & Packaging Materials and Technology in Universities

of Shandong, Qilu University of Technology, Jinan, China [email protected] 2 School of Light Industry Science and Engineering, Qilu University of Technology, Jinan, China

Abstract. To study the differences in color reproduction of color image after scanning by two different color scanners. The printed color blocks were scanned by using two different color scanners to obtain image information and printed. And the printed color blocks before and after scanning were measured using a UV spectrophotometer and then programmed using Matlab software to calculate their color gamuts, volumes, and color differences from the color blocks before scanning. We got that the large format scanner ROWE Scan 850i has better image color reproduction than Fujitsu Fi-760LA image scanner by comparison. This facilitates us to choose the right scanner when scanning color images. Keywords: Scanner · Color reproduction · Color gamut

1 Introduction Of all human senses, the sense of vision and color is feared to be the most exciting, and color information brings much more information than black and white information. With the development of digital technology, color information capture tools with CCD as the light sensitive element have become useful in the fields of color reproduction and machine vision [1], especially color scanners that are mostly used in the field of color reproduction have become common equipment. In the printing industry, the scanner is a very important image input device, an important source of information acquisition of the original, and the accuracy of color reproduction is essential for high-quality, highquality color reproduction of printed images [2, 3]. There are many types of scanners and many indicators to evaluate them. Among them, color characteristics are one of its most important indicators. The accuracy of the color obtained by the scanner has a great impact on the quality of the display and output that follows. XIN Huajun [4] studied the analysis of the influence of color input target on the color characteristics of a scanner, and concluded that when selecting a scanner color target, factors such as manuscript, color gamut, accuracy and cost effectiveness should be taken into account to finally obtain satisfactory scanning results. Bin Li, Yi-xin Zhang [5] analyzed the feasibility of

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 8–13, 2022. https://doi.org/10.1007/978-981-19-1673-1_2

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a new characterization model based on support vector regression for nonlinear conversion of scanner RGB color space to CIELAB color space by studying the colorimetric characterization method and the principle of Support Vector Regression (SVR). The feasibility of nonlinear conversion of the scanner RGB color space to CIELAB color space based on support vector regression is analyzed and a new characterization model is established. Prarthana Shrestha [6] focuses on the color analysis of WSI scanners and plots the scanned colors into the standard sRGB color space of the display device. M. J. Vrhel [7] studied the calibration of color scanners based on neural networks and gave a mathematical formulation for color scanner calibration. Li Xinwu [8] studied the color control of color scanners and proposed a new color control model based on segment fitting based on the analysis of color scanner rendering principles. Wei-Chung Cheng, Tyler Keay [9] introduced a new method for accessing color reproducibility of whole-slide image systems. The above studies are based on one scanner for its color characterization, but they do not compare the differences in color characteristics of two scanners, which will be discussed in this paper for the color characteristics of two different scanners. In this paper, we will discuss the color characteristics of two different scanners.

2 Experimental Materials and Equipment Experimental equipment: Konica Minolta color digital printing machine AccurioPress C6100, large-format scanner ROWE Scan 850i, Fujitsu Fi-760LA image scanner Experimental material: coated paper Measurement equipment: UV spectrophotometer Data processing software: Matlab, Microsoft Excel

3 Experimental Procedure First, prepare the color card file to be printed, for this experiment, I select the IT8.73 CMYK color card, which has 1120 color patches with 56 rows and 20 columns. This color card as the research object is representative. Next, the prepared color card file is printed using the laboratory printer as the experimental comparison diagram, as shown in Fig. 1. After completing the above work, the printed experimental comparison diagram is scanned using the ROWE Scan 850i scanner and the Fujitsu Fi-760LA image scanner to form the graphic file. And the resolution of the scanners is 300 dpi. Next, the scanned color blocks are printed with the same printer as before, and these figures are used as the experimental diagrams, as shown in Fig. 2 and Fig. 3. Finally, the L*a*b* values of the comparison diagram and experimental diagrams are measured using a UV spectrophotometer with a D50 standard light source and a measurement angle of 2. After that, the color gamut, color gamut volume and color difference of the comparison diagram and experimental diagrams are calculated by using Matlab program. The entire experimental flow is shown in Fig. 4.

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J. Bai and M. Lin

Fig. 1. Comparison diagram

Fig. 2. Experimental diagram - ROWE Scan 850i scanner

Fig. 3. Experimental diagram - Fi-760LA image scanner

Prepare the printing color cards

Print the color cards

Scanning of printed color cards

Print the scanned color cards

Measure the color block a value of L*a* b*

Calculation of color gamut, color gamut volume, color difference

Fig. 4. Experimental flow

4 Experimental Data Analysis 4.1 Color Gamut The color gamut of the comparison diagram and the experimental diagrams obtained by using Matlab programming are shown in Fig. 5, Fig. 6 and Fig. 7, where Fig. 5 is the color gamut of comparison chart, Fig. 6 is the color gamut of the experimental chart

Study of Color Reproduction Based on Different Scanners

11

scanned by using ROWE Scan 850i, and Fig. 7 is the color gamut of the experimental chart scanned by using Fi-760LA image scanner.

Fig. 5. Comparison diagram color gamut

Fig. 6. ROWE Scan 850i color gamut

Fig. 7. Fi-760LA image scanner color gamut

By comparing Fig. 6 and Fig. 7 with Fig. 5, we can see that the color gamut of the experimental image is much smaller than that of the comparison image, which means that a large part of the color information is lost during the scanning process. By comparing Fig. 6 and Fig. 7, we can get that the color gamut of the ROWE Scan 850i scanner is larger than that of the Fi-760LA scanner, so we conclude that the ROWE Scan 850i scanner has higher color reproduction accuracy than the Fi-760LA scanner. 4.2 Volume In order to compare the size of these three color gamut more precisely, the volume size of these three color gamut were calculated separately using Matlab programming, and the following results were obtained. dela_volume_1 = 4.1090e+05 dela_volume_2 = 3.1034e+05 dela_volume_3 = 2.1931e+05 dela_volume_1 represents the volume size of the color gamut of the comparison diagram in Fig. 5, dela_volume_2 represents the volume size of the color gamut of ROWE Scan 850i in Fig. 6, and dela_volume_3 represents the volume size of the color gamut of Fi-760LA image scanner in Fig. 7.

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J. Bai and M. Lin

According to the specific values of the obtained volumes, the volume of the color gamut of the comparison diagram is 1.32 times larger than the volume of the color gamut of ROWE Scan 850i and 1.87 times larger than the volume of the color gamut of Fi-760LA. And the volume of the color gamut of ROWE Scan 850i is 1.41 times larger than the volume of the color gamut of Fi-760LA. Therefore, it is concluded that the ROWE Scan 850i scanner has much higher color reproduction accuracy than the Fi-760LA scanner. 4.3 Color Difference The color difference method is the main method for objective evaluation of scanner profiles, also known as the E method. There are various methods for calculating the color difference, such as E* Lab, ECMC, E*94, E2000, etc. In this experiment, color difference calculation formula of E2000 is used: The color differences between the ROWE Scan 850i scanner and Fi-760LA image scanner with the comparison diagram are shown in Fig. 8 and Fig. 9.

Fig. 8. ROWE Scan 850i scanner

Fig. 9. Fi-760LA image scanner

The average values of the color difference between the comparison diagram and experimental diagram programmed using Matlab are a = 7.496 and b = 12.432, respectively, where a represents the color difference between the comparison diagram and the large-format scanner ROWE Scan 850i, and b represents the color difference between the comparison diagram and the Fi-760LA scanner. Comparing the two color differences, the color difference of the ROWE Scan 850i is much smaller than the color difference of the Fi-760LA. This means that the image after scanning by ROWE Scan 850i is closer to the original image.

5 Conclusions Through the above experiments, we studied and analyzed the color image reproduction capability of the large format scanner ROWE Scan 850i and Fi-760LA image scanner. And we found that the color gamut volume of the large format scanner ROWE Scan 850i is larger than that of the Fi-760LA image scanner from experimental data. The color difference of the large format scanner ROWE Scan 850i has a smaller value than the Fi-760LA image scanner, which is consistent with the color gamut volume. Therefore, we should use the large format scanner ROWE Scan 850i for scanning color images.

Study of Color Reproduction Based on Different Scanners

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References 1. Yu, Q.Y.: CCD, ICCD and IRCCD as image sensors. Opt. Precis. Eng. 2(5), 8–16 (1994) 2. Xu, Y., Liu, W., Zuo, K., et al.: Characterization of color scanners. Opt. Precis. Eng. 12(l), 15–20 (2004) 3. Xu, Y., Huang, M., Jin, Y.: Characterization of monitors based on colorimetric ratios. Chin. J. Liq. Cryst. Displ. 23(6), 771–777 (2008) 4. Xin, H.J., Liu, Y.: Influence analysis of color input target to the scanner color characteristic. Appl. Mech. Mater. 262, 123–126 (2012) 5. Li, B., Zhang, Y.-X.: Characterization of color scanners based on SVR. In: Color Imaging XVII: Displaying, Processing, Hardcopy, and Applications (2012) 6. Gurcan, M.N., Madabhushi, A., Shrestha, P., Hulsken, B.: Color accuracy and reproducibility in whole slide imaging scanners. In: Medical Imaging 2014: Digital Pathology (2014) 7. Vrhel, M.J., Trussell, H.J.: Color scanner calibration via a neural network. In: 1999 IEEE International Conference on Acoustics, Speech, and Signal Processing Proceedings. ICASSP99 (Cat. No. 99CH36258) 8. Li, X.W.: Research on color control for color scanner. Adv. Mater. Res. 121–122, 797–800 (2010) 9. Gurcan, M.N., et al.: Assessing color reproducibility of whole-slide imaging scanners. In: Medical Imaging 2013: Digital Pathology (2013)

The Impact of Color Matching Functions on the Observer Metamerism and a Solution Keyu Shi and Ming Ronnier Luo(B) State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Zhejiang, China [email protected]

Abstract. When viewing two displays, a pair of stimuli may match perfectly for one observer, the other observer may perceive as a mismatch. This phenomenon is caused by so called observer metamerism. An experiment was carried out to perform color matching of color stimuli with a field-of-view of 4° between three displays. A matrix-based color correction metric was developed which was used to overcome observer metamerism for displays. The impact of color matching functions on the observer metamerism was investigated as well. The results showed that the color correction metric was effective, and the use of 2006 2° color matching function outperformed the other CMFs. Keywords: Observer metamerism · Color matching functions · Correction metric

1 Introduction Color matching function is an important part of color science, which defines the average human perception to match stimuli across the visible spectrum. The data were obtained by performing color matching experiment by a group of observers. CIE standardized two sets of standard colorimetric observers, CIE 1931 and 1964 standard colorimetric observers, or 2o and 10° observers [1, 2]. The data were published in CIE 15:2018 [3]. When viewing two displays, a pair of stimuli may match perfectly for one observer, the other observer may perceive as a mismatch. This phenomenon is called the Observer Metamerism [4]. The observer metamerism is caused by the different visual response of individual observers, and different spectral functions of the two stimuli. In 2006, CIE [5] also published a 2° CMF based on individual optical densities of macular pigment, visual pigment, and lens density. The procedure can be applied to compute CMF by considering varying viewing fields from 2° to 10° at different ages. The problem encountered by the display industry is the mismatch [6–9] between a pair of stimuli on different displays having same XYZ values. The phenomenon can be explained by math expression in Eqs. (1) and (2).

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 14–19, 2022. https://doi.org/10.1007/978-981-19-1673-1_3

The Impact of Color Matching Functions

⎤ ⎡ ⎤ ⎡ ⎤ X1 SR1 R1 ⎣ Y1 ⎦ = CMF1 ∗ ⎣ SG1 ⎦ ∗ ⎣ G1 ⎦ Z1 SB1 B1 ⎡ ⎤ ⎡ ⎤ ⎡ ⎤ X2 SR2 R2 ⎣ Y2 ⎦ = CMF2 ∗ ⎣ SG2 ⎦ ∗ ⎣ G2 ⎦ Z2 SB2 B2

15

⎡

(1)

(2)

where [X 1 Y 1 Z 1 ] and [X 2 Y 2 Z 2 ] express the tristimulus values of colors on two displays; CMF1 and CMF2 are the CMFs of two observers; [S R1 S G1 S B1 ] and [S R2 S G2 S B2 ] are the spectral power distributions (SPDs) of the RGB primaries of the two displays considered; [R G B] are the signal for RGB channels. For observer metamerism, XYZ values in Eqs. (1) and (2) are equal, meaning a color match under one condition, but a mismatch under the other conditions [7–10]. This paper was aimed to derive a color correction (CC) model to reduce the observer metamerism, and to verify from different CMFs [11].

2 Experimental Three displays were used in the present study, including 2 LCD and 1 OLED displays, for which one of the LCD displays was used as reference in this study. They were first characterized using the GOG (gain-offset-gamma) model [13]. At a later stage, it was found that GOG model’s performance was worse than the 9 × 9 × 9 Look-Up-Table [14] for the OLED displays. Their performance of characterization model was calculated in CIEDE2000 (E 00 ) in predicting the 24 colors on the X-Rite Macbeth ColorChecker chart (MCCC). For reference display, its model performance in E 00 was 0.3, for the other two displays, named A and B, the E 00 values were 0.38 and 0.69, respectively. The results indicate a reasonable accuracy of the characterization models for all displays. The color matching experiment was carried out in a dark environment with 20 observers (8 males, 12 females), with an average age of 25 and a standard deviation of 2.25. The filed size of each color patch was 4° against a black background, which was a black paper. The two patches had a 10 cm apart. Observers were asked to first adapt in the dark environment for 2 min before the experiment. They were then to perform matching task for 4 stimuli in the experiment. Each observer adjusted color via arrow keys on the keyboard using two CIELAB attributes, a* and b* . The observer metamerism was quantified by CIEDE2000 formula [15, 16] between the SPDs of reference and matched stimuli. The experiment used 4 stimuli from MCCC, including blue sky, moderate red, yellow green, and neutral 5. They were named B, R, G and N respectively. The results were also used to investigate the number of minimum colors required to develop CC model.

3 Data Analysis As mentioned before, the color difference between observers matched and the reference colors was used to quantify observer metamerism. By using different CMFs when transfer

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K. Shi and M. R. Luo

SPDs to XYZ values, XYZ values of matching results and reference colors under a CMF were recorded, as shown in Eqs. (1) and (2). A CC model as given in Eq. (3) was developed by simply applying a 3 × 3 correction matrix between the reference and matched colors between the reference and each of the 2 testing displays, for which, the 1964 10° CMF was used. The calculation from SPDs to XYZ values were calculated using Eqs. (1) and (2) for the reference and test displays, respectively. ⎤ ⎡ ⎤⎡ ⎤ C1 C2 C3 X2 X 2 ⎣ Y  2 ⎦ = ⎣ C4 C5 C6 ⎦⎣ Y2 ⎦ Z 2 C7 C8 C9 Z2 ⎡

(3)

where the 9 matrix coefficients form the CC model were used to correct from [X 2 Y 2 Z 2 ] to [X2 Y2 Z2 ]. The coefficients were optimized via the minimize function of MATLAB program to minimize E 00 between the optimized [X2 Y2 Z2 ] and target [X 1 Y 1 Z 1 ]. In this study, two CC models were derived by using the data of all colors or only a neutral color. The results from the CC model are also given in Fig. 1.

4 Result The Mean of Color Differences from the Mean (MCDM) was used to represent the disagreement between observers’ matching results. The column named ‘Inter’ represents inter-observer variation in E 00 unit. The mean MCDM values of inter-observer variation for Displays A, B were 2.52, 2.31E 00 units, respectively. Figure 1 results showed that the mean observer metamerism values for 1931 2°, 1964 10°, 2006 2°, and 2006 10° CMFs were 5.06, 25, 4.04, 4.31E 00 units, respectively. This indicates that to quantify observer metamerism using 1931 2° CMF will always produce poorer results, larger errors, while very similar results were found between the other three CMFs. However, the results of 2006 2° CMF was markedly better than CIE 2° CMF, which confirms Wei et al.’s finding [11].

Fig. 1. Observer metamerism calculated by different CMFs (E 00 ) and CC model together with the inter-observer variation.

Figure 2 show the 95% confidence tolerance ellipses in a* b* plane for Displays A (top) and B (bottom) respectively. It can be seen that all ellipses for each centre are similar

The Impact of Color Matching Functions

17

Fig. 2. 95% confidence tolerance ellipses in a*b* plane for 2 displays (top for Display A, bottom for Display B). The red, green, blue, purple, cyan, grey ellipses represent 1931 2°, 1964 10o , 2006 2o , 2006 10o , model (all colors), model (only neutral) respectively.

except the modeled ellipse to be the smallest, or the most consistent by observers. Also, the ellipses are not equal sized circles indicate CIELAB is a poor uniform space. Figure 3 and Fig. 4 show results plotted in bar chart for easily to compare the ellipse size and distance between the ellipse centre and target, respectively.

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K. Shi and M. R. Luo

From Fig. 3, it can be seen the CC model’s (using all colors) predictions were always more consistent than those calculated using different CMFs. Also, using different CMFs made little difference to the areas of the ellipse (observer consistency), together with the CC matrix reduced the inter-observer variation of observers’ data. When considering color shift between the centre of ellipses and reference colors (see Fig. 4), the CC model gave the overall best performance for both displays. In addition, 2006 2° CMF results gave the smallest mean distance between those of all CMFs. This is particularly marked for Display A, as agree with Wei et al.’s finding, i.e. comparing an OLED (Display A) and LCD (reference) displays, 2006 2° CMF outperformed 1931 2° CMF by large margin.

Fig. 3. Area of ellipses of observers’ matching results on a* b* plane (*10ˆ2).

Fig. 4. Distance between the centre of ellipses of observers’ matching results and reference colors on the a* b* plane.

5 Conclusions This paper describes a color matching experiment to overcome the problem of observer metamerism between displays. The results showed that the chosen of CMF do have a great impact on the observer metamerism between the two displays. The 2006 2° CMF outperformed 1931 2° CMF, especially between OLED and LCD displays. The CC model derived from the visual matching results can effectively reduce the value of the observer metamerism, however, model derived from data of only a single neutral color could not achieve good performance.

The Impact of Color Matching Functions

19

References 1. Guil, J.: The colorimetric properties of the spectrum. Phil. Trans. R. Soc. Lond. A 230(681– 693), 149–187 (1931) 2. Speranskaya, N.I.: Determination of spectral color co-ordinates for twenty-seven normal observers. Optics Spectrosc. 7, 424–428 (1959) 3. CIE 015:2018: Colorimetry, 4th edn. (2018) 4. Fairchild, M.D.: Color Appearance Models. Wiley, Hoboken (2013) 5. CIE. 170:2006: Fundamental Chromaticity Diagram with Physiological Axes—Part 1, CIE Publication (2006) 6. Li, J., Hanselaer, P., Smet, K.A.G.: Impact of color matching primaries on observer matching: Part I –Accuracy. Leukos, Published online (2020). https://doi.org/10.1080/15502724.186 4395 7. Li, J., Hanselaer, P., Smet, K.A.G.: Impact of Color Matching Primaries on Observer Matching: Part II – Observer Variability. Leukos, Published online (2020). https://doi.org/10.1080/ 15502724.1864396 8. Oicherman, B., Luo, M.R., Rigg, B., Robertson, A.R.: Adaptation and color matching of display and surface colors. Color Res. Appl. 34(3), 182–193 (2009) 9. Sarkar, A., Blonde, L., Callet, P.L., Autrusseau, F., Morvan, P., Stauder, J.: A color matching experiment using two displays: design considerations and pilot test results. In: Proceedings of the 5th European Conference on Color in Graphics, Imaging and Vision Optics. McGraw Hill (2010) 10. Hu, Y., Wei, M., Luo, M.R.: Observer metamerism to display white point using different primary set. Opt. Express 28(14), 20305–20323 (2020) 11. Wu, J., Wei, M.: Color mismatch and observer metamerism between Conventional Liquid Crystal Displays and Organic Light Emitting Diode Displays. Optics Express (2021) 12. Fang, J., Kim, Y.J.: A matrix-based method of color correction for metamerism failure between LCD and OLED. In: SID International Symposium Digest of Technical Papers, vol. 49, no. 1, pp. 1044–1047 (2018) 13. Wei, M., Chen, S.: Effects of adapting luminance and CCT on appearance of white and degree of chromatic adaptation. Opt. Express 27(6), 9276–9286 (2019) 14. Zhu, Y., Wei, M., Luo, M.R.: Investigation of effects on adapting chromaticities and luminance on color appearance on computer displays using memory colors. Color Res. Appl. 45, 612–621 (2020) 15. Johnson, G.M., Fairchild, M.D.: A top down description of S-CIELAB and CIEDE2000. Color. Res. Appl. 28(6), 425–435 (2003) 16. Wyszecki, G., Stiles, W.S.: Color Science: Concepts and Methods, Quantitative Data and Formulae, 2nd edn. Wiley, Hoboken (1982)

Influences of Reference Colors on Cluster Analysis of Color Matching Functions Yu Wang1 , Chunjie Shi2 , Yu Li1 , Yu Liu1 , and Min Huang1(B) 1 School of Printing and Packing Engineering, Beijing Institute of Graphic Communication,

Beijing, China [email protected] 2 College of Network Communication, Zhejiang Yuexiu University of Foreign Languages, Shaoxing, China

Abstract. In order to study the effect of the selection of different reference colors on observer categorical results, 108 color matching functions (CMFs) were clustered into 5 categories in x(λ), y(λ) and z(λ) channels by the cluster analysis method, and then 125 CMFs were generated. CIE recommended 5(/17) colors were presented on the LED-Panel with different red, green and blue primaries as reference colors, 17 observer categories were selected from the 17 reference colors, where the 14 observer categories from 5 reference colors were included in the 17 observer categories. The 17 observer categories were tested by the visual results from the paired-comparison color matching experiments from young and aged observers in our previous study. The results indicated that the categorized observers are less affected by the 5 or 17 reference colors, the CIE recommended 5 colors are proper for observer categories. Keywords: Color matching functions · Cluster analysis · Observer categories

1 Introduction The existing color matching functions for calculating the chromaticity value are CIE1931 [1] and CIE1964 [2] recommended by Commission International de l Eclairage (CIE), which represent the average spectral response of cones of observers at small viewing angle (2°) and large viewing angle (10°). Considering the visual differences between individual observers, CIETC1-36 introduced the CIE2006 observer physiology model [3] in 2006, which takes into account the age (20–80 years) and the field of view (1°– 10°) of individual observer CMFs, but it was not convenient for practical use. Sarkar [4] proposed eight observer categories using the method of cluster analysis with the reference color of 240 Color Check illuminated by D65 illumination, named Sarkar 1 - Sarkar 8 (hereinafter referred to as S1–S8) based on 10° field of view. In 2020, we proposed [5] four BIGC CMFs using the method of cluster analysis with CIE 17 color centers [6] and either presented on five different displays with red, green and blue primaries or printed and illuminated by different light sources as the reference color stimuli. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 20–24, 2022. https://doi.org/10.1007/978-981-19-1673-1_4

Influences of Reference Colors on Cluster Analysis

21

In order to compare the effect of reference colors, such as the sample numbers, the primaries of reference colors on clustering of observer categories. We selected CIE recommended 5 and 17 colors as the reference colors respectively, which were displayed on LED-Panel [7] with red, green and blue primaries. The categorized observers were tested by previous visual results from metamerism reflective color sample pairs [8], and then the proper sample numbers were determined by STRESS values [9].

2 Observer Categories with Different Reference Colors 2.1 Individual and Categorical Observers 108 CMFs generated by 47 real observers from Stiles & Burch [10] in 1959 and 61 simulated observers with different ages ranging from 20 to 80 calculated by the CIE2006 model in 10° field size were regarded as different individual observer. The spectral response of the 108 color matching functions are shown in Fig. 1(a), with 47 real observers and 61 simulated observers marked with red and blue lines, respectively. In the calculation, the k-medoids algorithm was used in the cluster analysis, the central object in the cluster was taken as the reference point, the 108 CMFs were clustered into 5 categories in x(λ), y(λ) and z(λ) channels, as shown in Fig. 1(b) and then a total of 5 × 5 × 5 = 125 color matching functions are generated. (b)

Spectral tristimulus Values

(a)

2.5

x_bar y_bar z_bar

2 1.5 1 0.5 0 -0.5

390

465

540

615

690

765

Wavelength/nm

Fig. 1. (a) The spectral response of 108 CMFs; (b) Five categories in different channels

2.2 Reference Colors In order to generate different primary sets to produce the reference colors on LED-Panel, we combine the six primaries, such as R1 (636 nm) - R2 (672 nm) - G1 (−508 nm) G2 (524 nm) - B1 (452 nm) - B2 (472 nm) with seven primary sets, as shown in Table 1. The CIE recommended 5 and 17 colors were simulated on the LED-Panel as the reference colors in turn. The spectral energies of the 17 colors produced by primary set were measured by PR655 spectral radiometer and then the colorimetric values were calculated by CIE1964 CMFs, as shown in Table 2, the bold font indicated the 5 reference colors from the 17 colors.

22

Y. Wang et al. Table 1. Seven primary sets of the LED-Panel

Combinations L1 Primary sets

L2

L3

L4

L5

L6

L7

R1G2B1 R2G2B1 R1G1B1 R1G2B2 R1G1B2 R2G2B2 R2G1B1

Table 2. Colorimetric values of the reference colors by CIE1964 Color

L* 10

a* 10

b* 10

C* 10

h* 10

Grey

62.1

−0.1

−0.4

0.4

258.5

Red

44.3

36.3

23.2

43.1

32.6

Red high

43.9

58.0

36.6

68.6

32.2

Orange

63.1

12.3

21.5

24.8

60.2

Orange high

62.9

35.8

62.7

72.2

60.3

Yellow

87.1

−7.4

47.7

48.3

98.8

Yellow high

86.9

−10.2

75.8

76.5

97.7

Yellow-green

65.1

−9.8

12.8

16.1

127.4

Yellow-green high

64.9

−29.3

38.9

48.7

127.0

Green

55.9

−31.3

−0.7

31.4

181.3

Green high

56.0

−45.3

−0.8

45.3

181.0

Blue-green

50.1

−16.2

−11.2

19.7

214.5

Blue-green high

49.9

−31.2

−22.4

38.4

215.7

Blue

35.9

5.0

−31.7

32.1

279.0

Blue high

34.1

6.3

−44.6

45.1

278.1

Purple

45.9

12.5

−13.1

18.1

313.6

Purple high

45.8

26.0

−26.3

37.0

314.6

2.3 Clustering Analysis Method The cluster analysis method used in this study is similar with those in our previous study, each of the 108 individual observers was used to calculate CIEDE2000 color difference with the 125 CMFs in turn, and the CMF from the 125 CMFs corresponding to the minimum CIEDE2000 value will be assigned for the individual observer. In order to accumulate as many observers as possible in a limited category, the criteria for Accumulative Probabilities (AP%) of the observers assigned to the top observer categories is no less than 75%. The different combinations from seven primary sets were gathered in sequence (italics font and filled in gray background), and then 14 (or 17) unique combinations were selected considering all the combinations based on the seven primary sets from 5 (or 17) reference colors, named BF-1, BF-2, … , BF-14 and BS-1, BS-2, … , BS-17.

Influences of Reference Colors on Cluster Analysis

23

3 Results and Discussions Since the 14 observer categories selected from the 5 reference colors are contained within the 17 observer categories, the performance of the 17 observer categories were tested in the further study. The visual results from the paired-comparison experiments conducted by Ruili He [8] with metamerism reflective sample pairs in our previous study were used. The 20 metamerism sample pairs were assessed by 30 young and 26 aged observers, the computed CIEDE2000 color difference (E) and the visual results (V) were evaluated by STRESS value and the results are shown in Table 3. In previous study, S2 and B5 are recommended for young and aged observers, the STRESS values were also given in Table 3 as comparison. Table 3. STRESS values between visual results from young and aged observers by different CMFs CMFs

BS-1

BS-2

BS-3

BS-4

BS-5

BS-6

BS-7

BS-8

BS-9

Young

32.7

35.1

62.9

40.2

37.4

38.5

40.3

38.8

39.2

Aged

58.2

54.8

32.0

65.4

55.8

64.2

65.2

64.6

64.8

BS-10

BS-11

BS-12

BS-13

BS-14

BS-15

BS-16

BS-17

S2

B5

61.6

40.6

46.8

34.4

45.4

32.2

43.4

41.5

34.6

63.3

32.6

65.4

69.4

54.6

69.0

57.4

65.3

65.9

49.3

32.2

In Table 3, for young observers, BS-15 had the best performance, with the smallest STRESS value of 32.2, followed by BS-1. For aged observers, BS-3 had the best performance, with the smallest STRESS value of 32.0. The smaller values for young observers, the larger for aged observers will be. It should be noted that, observer category BS-15 for young observers were selected from 17 reference colors, which was a little bit better than that of BS-1. As for the aged observers, observer categories BS-3 were selected from the 5 reference colors. The results indicated that whether 5 or 17 reference colors were used in the process of observer categories clustering, the results are quite similar, they have no obvious influences on the categorical results.

4 Conclusions In this study, in order to categorize observer functions, 108 individual observers were clustered into 125 categorized observers by the method of cluster analysis. CIE recommended 5 and 17 colors for uniform color space and color difference evaluation were used for reference colors, which were presented on a LED display with six-channels produced by ThousLite, and then 14 and 17 CMFs were selected out from the 125 observer observers. Especially, the 14 CMFs from the 5 reference colors were all included in the 17 CMFs from the 17 reference colors. The performance of the categorical observers were tested by the visual results from the paired-comparison experiments, the results indicated that the 5 or 17 reference colors have no obvious influences on the categorical results.

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Acknowledgements. This research is supported by Funding National Natural Science Foundation of China (NNSFC) (61675029); Beijing Municipal youth talent support program (2018). Disclosures The authors declare no conflicts of interest.

Informed Consent. Informed consent was obtained from all individual participants included in the study.

References 1. Wright, W.D.: A re-determination of the trichromatic coefficients of the spectral colours. Trans. Opt. Soc. 30, 141–164 (1929) 2. Stiles, W.S., Burch, J.M.: N.P.L. colormatching investigation: final report. Optica Acta Int. J. Opt., 1–26 (1959) 3. CIE: Fundamental chromaticity diagram with physiological axes–Part I, CIE Technical report, pp. 170–171 (2006) 4. Sarkar, A.: Identification and Assignment of Colorimetric Observer Categories and Their Applications in Color Vision Science. France Universite De Nantes, Rennes (2011) 5. Huang, M., Xi, Y.H., et al.: Colorimetric observer categories for young and aged using pairedcomparison experiments. IEEE Access 8, 219473–219482 (2020) 6. Witt, K.: CIE guidelines for coordinated future work on industrial colour-difference evaluation. Color Res. Appl. 20, 399–403 (1995) 7. HOUSLIFE. http://www.thouslite.cn/PRODUCTS/17.html. Accessed 01 Feb 2021 8. He, R., Huang, M., Guo, C., et al.: Color Difference discrimination between young and old observers. Las. Opt. Prog. 55, 1–8 (2018) 9. CIE 217: 2016, Recommended method for evaluating the performance of colour-difference formulae, CIE Central Bureau, Vienna (2016) 10. Stiles, W.S., Burch, J.M.: J. Modern Optics (1959)

Evaluation of Color Matching Functions with Neutral Metamerism Printed Samples Yu Li, Yu Wang, Yuxin Chen, Yu Liu, and Min Huang(B) School of Printing and Packing Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. In order to test the performances of different color matching functions (CMFs), a total of 80 pairs of neutral metamerism printed samples based on five lightness levels were prepared. 26 observers with normal color vision were organized to carry out the visual experiments with the gray scale method. Four CMFs, including CIE1964, CIE2006, Sarkar 2 and BIGC 17 were compared with the calculated color difference (E) and the visual color differences (V) by the Standardized Residual Sum of Squares (STRESS) values. The results indicated that amongst the four CMFs, Sarkar 2 with the smallest STRESS value of 26.8 and the maximum number (equal to 46) of observers from 52 judgements, it’s outperformed others and secondly by BIGC17 CMFs. CIE recommended CMFs, CIE1964 and CIE2006 have no advantages over Sarkar 2 and BIGC17 CMFs when viewing printed materials illuminated by the fluorescent light sources in the field size larger than 10°. Keywords: Color matching functions · Gray scale method · Metamerism neutral printed samples · STRESS

1 Introduction The color perception of human eyes can be quantified by spectral responses of cone fundamentals, also named color matching functions. The CIE recommended CIE1931 [1], CIE1964 [2] and CIE2006 [3]. In recent years, the performances of the CIE CMFs were tested by metamerism sample pairs with different primaries. All the existing CIE CMF sets were not strongly predictive for visual matches. New CMFs is needed to improve the calculations. In 2010, Sarkar et al. [4] proposed the observers’ categories of Sarkar 1-Sarkar 8 (hereafter named S1–S8) on the base of 108 CMFs. In 2020 [5], we performed a cluster analysis method on seven devices with different primary sets and 19 sets of BIGC1BIGC19 (hereafter named B1–B19) were proposed. Then S2 and B17 were selected out for young observers [5]. In order to test the performances of the CMFs, including CIE1964, CIE2006, S2 and B17 for neutral metamerism sample pairs, we prepared 80 pairs of printed samples to carry out the color difference experiment with the method of gray scale. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 25–29, 2022. https://doi.org/10.1007/978-981-19-1673-1_5

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2 Experimental 2.1 Sample Preparation and Selection Five neutral colors with different lightness (hereafter named NL1-NL5) in RAL K5 color card were selected as the target colors. Table 1 showed the chromaticity values of the target samples measured by X-Rite e-Xact with the conditions of D65/10°. The compared samples were produced by an Epson Stylus Pro7908 inkjet printer on the paper of Premium Semimatte Photo Paper 260, sixteen printed samples with the CIELAB color difference ranging from 0.54–5.15, and the C∗ab < 10. The size of all samples was both 5 cm × 5 cm. The spectral curves of the 85 samples measured by X-Rite e-Xact were illustrated in Fig. 1. Table 1. Chromaticity values of the five target colors Target color

NL1

NL2

NL3

NL4

NL5

L∗10 a∗10 b∗10

34.36

45.38

54.48

62.65

71.61

−2.42

−1.82

−2.19

0.15

0.04

−2.82

1.14

−3.27

−0.58

5.72

2.2 Lighting Source A GretagMacbeth Judge II viewing cabinet fitted with a D65 simulator was used in the visual experiment, which had the illuminances of 779.1 lx, the Correlated Color Temperature (CCT) of 6434K and the CIE Color Rendering index (Ra) of 92.1 by MK350S Spectrophotometer. The spectral power distribution of the light source measured by Photo-Research PR655 spectral radiometer is shown in Fig. 2. 0.6

Target

0.008

Compared

S(λ)/(W/Sr/m2)

0.5

ρ(λ)

0.4 0.3 0.2

0.006 0.004 0.002

0.1 0.0 400

500

600

λ/nm

Fig. 1. Spectral reflectance of five target colors and 80 compared samples

700

0 380

480

580

680

780

λ/nm

Fig. 2. Spectral power distribution of light source

Evaluation of Color Matching Functions

27

2.3 Visual Experiments The experiment was carried out in a dark room with the method of gray scale, which was made with the same material of the compared samples. The CIELAB color difference of the gray scale grade (GS) is ranging from 1.0–8.0 with the interval of 1.0 and meet the requirement of L* /E∗ab ≈ 1.0. The linear relationship between the grade and CIELAB ∗ = 0.8967 × GS + 0.3399. The visual color difference (V) color difference is Eab can be obtained by substituting the GS into the formula. Twenty-six observers aged from 19 to 24 (22 females and 4 males) participated in the experiment, each observer about 30 cm in visual distance. Gender has no significant effect on experimental differences [6], the effect of gender on the experiment is ignored here. During the experiment, the sample pair and the gray scale samples were placed in the central part of the cabinet’s floor, and the left-right position and sequence of sample pair to be presented to the observers were randomly selected. The gray scale grade (GS) given by the observers for each color-difference pair were collected. All observers are students from Beijing Institute of Graphic Communication (BIGC), with normal color vision and certain theoretical knowledge of color science, all of them repeated the experiment twice for investigating the observer repeatability. In total, there were 4160 sets of data were obtained (=16 judgments × 5 color centers × 2 replicates × 26 observers).

3 Analysis and Discussions 3.1 Observer Accuracy Observer accuracy includes observer repeatability (Intra-observer) and observer accuracy (Inter-observer). STRESS was used to calculate the observer accuracy [7]. The range of STRESS is 0–100, the smaller the STRESS value is, the better the correlation between the two sets of data. In our experiment, each observer assessed each pair twice in different times. The STRESS value was calculated between each individual observer’s two repeated sessions to represent the observer’s intra-observer variability. The values were ranged from 12.7 to 24.9 STRESS units, with the mean value of 17.1. The STRESS measure was also calculated between each individual observer’s and the mean visual results (V) to represent one observer’s inter-observer variability, the inter-observer variability was ranging from 17.1 to 44.4, with the average of 27.3. The results are accorded with those in the previous studies [8]. 3.2 Performances of Different CMFs Four CMFs, including CIE1964, CIE2006, S2, and B17 were used to calculate the CIEDE2000 color differences of the target and the compared samples. Among the four-CMFs, the STRESS value between V and E00 from 80 samples is 29.6, 30.6, 26.8 and 28.4, respectively. S2 outperformed others with the minimum STRESS value of 26.8, secondly by B17, with the value of 28.4. The two CIE recommended CMFs are inferior to S2 and B17 in this study.

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For a given observer, the minimum STRESS value from the four STRESS values was selected out, and the observer categories corresponding to the minimum value will be counted as the observer’s functions. The number of the observers contributed to the minimum STRESS values from the 52 judgements is 2, 4, 46 and 0, respectively. Therefore S2 are recommended for young observers for neutral metamerism printed samples in 10° viewing fields. The CIEDE2000 of the 80 sample pairs calculated from CIE1964 were used to divide the samples into different magnitudes, as shown in Table 2, the number in the brackets means the number of sample pairs to the magnitude, the bold font indicated the best performances in different magnitudes. Table 2. Performances of four CMFs in different magnitude by CIEDE2000 values CIEDE2000

CIE1964CMFs

CIE2006

S2

B17 CMFs

0–1.0(10)

21.4

23.5

23.9

21.7

1.0–2.0(23)

24.6

31.9

17.1

19.1

2.0–3.0(20)

23.3

25.4

22.2

23.4

>3.0(27)

13.2

16.2

12.3

12.9

In Table 2, when the color difference is larger than 3.0, the STRESS values decreasing gradually. The results are in agreements with those in the previous study [9]. Meanwhile, the STRESS values were calculated by 16 sample pairs in different lightness levels. The results were shown in Table 3. In Table 3, in NL4 lightness, with the L∗10 value of 62.65, the four CMFs are all performed the best amongst the five lightness levels. It means with the lower lightness, the predictions of the four CMFs are worse than those of the sample pairs with medium lightness. Table 3. Performances of four CMFs in different lightness levels Lightness levels

CIE1964 CMFs

CIE2006

S2

B17 CMFs

NL1

34.3

39.4

26.6

31.5

NL2

28.2

28.4

24.4

26.1

NL3

26.2

23.6

27.7

27.3

NL4

24.1

22.6

23.3

23.8

NL5

26.8

26.4

25.0

26.0

Evaluation of Color Matching Functions

29

4 Conclusions In order to test the performances of CIE1964, CIE2006, S2 and B17 for neutral printed matemariam samples. We designed 80 pairs of metamerism samples with five lightness levels. Twenty-six observers were organized to carry out the color difference experiments with the gray scale method and the visual results were used to test the performance of the four CMFs with the index of STRESS values. The results indicated that S2 outperformed others with the smallest STRESS value of 26.8 and the maximum number (equal to 46) of observers from 52 judgements. CIE recommended CIE1964 and CIE2006 CMFs are inferior to the two categorical observers (S2 and B17), the results are also accorded with those from the previous study by the self- illuminous colors. Acknowledgements. This research was supported by Beijing Municipal youth talent support program (2018); College’s Scientific Research Project (BIGC Ec202003, BIGC Eb202102). Thanks for all participants in our study.

Informed Consent. Informed consent was obtained from all individual participants included in the study.

References 1. Wright, W.D.: A re-determination of the trichromatic coefficients of the spectral colours. Trans. Opt. Soc. 30(4), 141–164 (1929) 2. Stiles, W.S., Burch, J.M.: N.P.L. colormatching investigation: final report (1958). Optica Acta Int. J. Opt., 1–26 (1959). https://doi.org/10.1080/713826267 3. CIE: Fundamental Chromaticity Diagram with Physiological Axes–Part I. CIE Technical report, pp. 170–171 (2006) 4. Sarkar, A., Autrusseau, F., Viénot, F., et al.: From CIE 2006 physiological model to improved age-dependent and average colorimetric observers. JOSA A 28(10), 2033–2048 (2011) 5. Huang, M., Xi, Y., Pan, J., et al.: Colorimetric observer categories for young and aged using paired-comparison experiments. IEEE Access (2020). https://doi.org/10.1109/ACCESS.2020. 3042817,219473-219482 6. Li, J., Hanselaer, P., Smet, K.A.G.: Impact of color-matching primaries on observer matching: Part I–accuracy. LEUKOS, 1–23 (2021) 7. CIE 217: 2016: Recommended method for evaluating the performance of colour-difference formulae. CIE Central Bureau, Vienna (2016) 8. Kulappurath, S.K., Shamey, R.: The effect of luminance on the perception of small color differences. Color. Res. Appl. (2021). https://doi.org/10.1002/col.22637 9. Huang, M., Cui, G., Melgosa, M., et al.: Power functions improving the performance of colordifference formulas. Opt. Express 23(1), 597–610 (2015)

Multispectral Data Optimization Using Loop Algorithm to Remove Redundant Points Qian Cao1(B) , Junfeng Li2 , Xiaozhou Li3 , and Jun Liu4 1 Department of Printing and Packaging Engineering, Shanghai Publishing

and Printing College, Shanghai, China [email protected] 2 School of Packaging and Printing Engineering, Henan University of Animal Husbandry and Economy, Zhengzhou, Henan, China 3 School of Light Industry Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan, Shandong, China 4 Beijing Handpic Image Equipment Co., Ltd, Beijing, China

Abstract. There is a great limitation that there is limited color gamut and large number of redundant points in testing samples for evaluating multispectral data compression algorithms. This study proposes a method of optimizing the testing samples. First, multispectral images and the multispectral datasets were merged into a mixed multispectral dataset in which there exist 55,324,506 spectra. Then by deleting the spectral data whose color difference is less than 0.38 and removing 97.11% of the redundant points in the mixed spectral dataset, an optimized spectral dataset, which contains spectra of 1,596,839, is obtained, but the color gamut volume is almost unchanged. The optimized spectral dataset has wide representativeness as testing samples, because it has no redundant points and large color gamut. Keywords: Spectral data compression · Spectral dimensionality reduction · Spectral data optimization

1 Introduction Multispectral data compression technology becomes a key technology in the field of multispectral color reproduction. Many different algorithms have been applied to multispectral data compression, such as principal component analysis (PCA) [1], independent component analysis (ICA) [2] and so on. A large number of studies about multispectral data compression at home and abroad have been carried out, and a wealth of research results has been obtained. However, the research on the selection and optimization of training samples and testing samples has not received enough attention. Currently, because the color appearance system has the advantages of larger color gamut and good uniform distribution, such as Munsell glossy, Munsell matte, NCS, Pantone, etc., many researchers choose these spectral datasets as training samples or testing samples. In addition, multispectral images with different scenes have also been selected as testing samples due to their huge amount of data. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 30–35, 2022. https://doi.org/10.1007/978-981-19-1673-1_6

Multispectral Data Optimization

31

However, there are two major problems with testing samples such as Munsell glossy, Munsell matte, NCS, Pantone Agfa IT8.7/2, ColorChecker SG and multispectral images. First, the color gamut of spectral dataset of common standard color cards is limited, far less than the color gamut which the human eye can see. Second, common spectral datasets or multispectral images contain a large number of identical or similar color points.

2 Method Luo et al. [3] found that the human eye can distinguish two color points when CIEDE2000 color difference is greater than or equal to 0.38. That is, when CIEDE2000 color difference between two color points is less than 0.38, the human eye can’t distinguish the two color points. According to the human eye’s color difference threshold, redundant point is defined, that is, if CIEDE2000 color difference between two color points is less than 0.38, the color point closer to the center point of CIELAB color space is taken as the redundant color point. The process of spectral data optimization is as follows: (1) Merge spectral datasets and multispectral images to expand the color gamut: the representative spectral datasets and the multispectral images with different scenes are combined into the mixed spectral dataset. (2) The mixed multispectral dataset is converted to the mixed color dataset under illuminant D65 and the CIE 1931 standard colorimetric observers, and the loop algorithm based on human eye’ color difference threshold to remove redundant points in the mixed color dataset is adopted here. First, select the farthest point to the center point of the CIELAB color space, and delete any color point if the CIEDE2000 color difference between the color point and the farthest point is less than 0.38. Then, select the second farthest point among all the remaining color points to the center point of the CIELAB color space, and delete any color point if the CIEDE2000 color difference between the color point and the second farthest point is less than 0.38. Third, select the third farthest point among all the remaining color points to the center point of the CIELAB color space, and delete any color point if the CIEDE2000 color difference between the color point and the third farthest point is less than 0.38. In the same way we choose the fourth color point, the fifth color point, …, and so on. Finally, optimized color dataset, where the CIEDE2000 color difference between any two color points is greater than or equal to 0.38, is obtained. The optimized spectral dataset corresponding to the optimized color dataset is obtained.

3 Experiments and Process Seven spectral datasets of standard color cards are used, which are Munsell glossy [4], Munsell matte [4], NCS, ISO SOCS [5], Pantone, Color Checker SG and Agfa IT8.7/2 [4]. Table 1 lists the more details of 7 multispectral datasets.

32

Q. Cao et al. Table 1. Details of 7 multispectral datasets

Multispectral datasets

The number of samples

Multispectral datasets

The number of samples

Munsell glossy

1600

Pantone

Munsell matte

1269

Color checker SG

140

NCS

1950

Agfa IT8.7/2

289

ISO SOCS

53486

Total

1137

59871

99 multispectral images from five different main sources are used. The first group includes 32 multispectral images from Columbia University [6]. In the second group there are 30 multispectral images from Minho University [7]. In the third group there are 22 multispectral images from University of East Anglia [8]. The fourth group is composed of 6 multispectral images from University of Eastern Finland [4]. The fifth group includes 9 multispectral images from the Norwegian University of Science and Technology [9]. The more details of the 99 spectral images are displayed in Table 2. Table 2. Details of 99 multispectral images Spectral image datasets Sources

Number of images Number of spectra

The first group

Columbia University

32

8,126,464

The second group

Minho University

30

41,119,199

The third group

University of East Anglia

22

2,254,992

The fourth group

University of Eastern Finland

6

1,513,980

The fifth group

The Norwegian University of Science and Technology

9

2,250,000

99

55,264,635

Total

4 Results and Discussion 99 multispectral images and the spectral datasets, which contain NCS, Munsell matte, Munsell glossy, Pantone, ColorChecker SG, Agfa IT8.7/2,ISO SOCS and so on, are combined into a mixed spectral set named the mixed spectral dataset. The mixed spectral dataset has 55,324,506 sample points, but many of which are redundant points. Redundant points are deleted by using the method of removing redundant points described in Sect. 2. The samples after removing the redundant points are named the optimized spectral dataset. The comparison of mixed spectral dataset, optimization spectral dataset and other seven spectral datasets is listed in Table 3.

Multispectral Data Optimization

33

Table 3. Comparison of spectral datasets Samples

Mixed spectral dataset

Optimized spectral dataset

NCS

Munsell glossy

Pantone

ISO SOCS

Gamut volumea

1.6244 × 106

1.6242 × 106

3.4882 × 105

3.9881 × 105

7.8034 × 105

9.3705 × 105

The number of samples

55,324,506

1,596,839

1,950

1,600

1,137

53,486

Percentage 97.11% of redundant points

0

0

0.13%

0.18%

22.6%

File size

265 MB

262 KB

365 KB

149 KB

7.42 MB

10.3 GB

a The gamut volume refers to the volume of the color point sets converted from multispectral

datasets is calculated by using the convex hull algorithm [10].

It can be seen from Table 3 that optimized spectral dataset is obtained by removing 97.11% of the redundant points of mixed spectral dataset, but the color gamut volume almost does not change. The CIEDE2000 color difference between any two points in optimized mixed spectral dataset is larger than or equal to 0.38, that is to say, the human eye can distinguish all the colors in optimized spectral dataset. To better demonstrate the optimized spectral dataset, color gamut boundary of optimized spectral dataset in CIE1931xy chromaticity diagram is compared with those of NCS, Munsell glossy, Pantone, ISO SOCS, as shown in Fig. 1. It is obvious that the color gamut of the optimized spectral dataset is far greater than those of other spectral datasets. In addition, the distribution of L*a*b* chromaticity value converted from optimized spectral dataset and other spectral datasets are shown in Figs. 2, 3 and 4. It can be also indicated easily that the color gamut of the optimized spectral dataset is far greater than those of other spectral datasets.

Fig. 1. Comparison of color gamut boundaries of 5 spectral datasets.

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Fig. 2. Comparison of the distribution of L*a*b* chromaticity between the optimized spectral dataset and NCS. (a) L*a* diagram; (b) L*b* diagram; (c) a*b* diagram.

Fig. 3. Comparison of the distribution of L*a*b* chromaticity between the optimized spectral dataset and Munsell glossy. (a) L*a* diagram; (b) L*b* diagram; (c) a*b* diagram.

Fig. 4. Comparison of the distribution of L*a*b* chromaticity between the optimized spectral dataset and ISO SOCS. (a) L*a* diagram; (b) L*b* diagram; (c) a*b* diagram.

5 Conclusions In this paper 99 multispectral images and the multispectral datasets were combined into a mixed spectral dataset containing 55,324,506 color points. By deleting the spectral data whose color difference is less than 0.38 and removing 97.11% of the redundant points in the mixed spectral dataset, an optimized spectral dataset, which contains spectra of 1,596,839, is obtained, but the color gamut volume is almost unchanged. The optimized spectral dataset has wide representativeness as testing samples, because it has no redundant points and large color gamut. Acknowledgments. This study is funded by Key Lab of Intelligent and Green Flexographic Printing (No. ZBKT201905, No. ZBKT202001). This work is also supported by Key Research and Development Program of Shandong Province (No. 2019GGX105016).

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References 1. Tzeng, D.Y., Berns, R.S.: A review of principal component analysis and its applications to color technology. Color Res. Appl. 30, 84–98 (2005) 2. Laamanen, H.T., Jaeaeskelaeinen, T., Parkkinen, J.P.S.: Comparison of PCA and ICA in color recognition. In: Proceedings of SPIE - The International Society for Optical Engineering, vol. 4137 (2000) 3. Luo, M.R., Minchew, C., Kenyon, P., Cui, G.: In Verification of CIEDE2000 using industrial data. In: AIC 2004 Interim Meeting (2004) 4. Spectral Database, University of Joensuu Color Group. http://spectral.joensuu.fi/ 5. T. R. ISO: 16066-2003: Graphic technology—Standard object colour spectra database for colour reproduction evaluation (2003) 6. Yasuma, F., Mitsunaga, T., Iso, D., Nayar, S.K.: Generalized assorted pixel camera: postcapture control of resolution, dynamic range, and spectrum. IEEE Trans. Image Process. 19, 2241–2253 (2010) 7. Nascimento, S.M., Amano, K., Foster, D.H.: Spatial distributions of local illumination color in natural scenes. Vision Res. 120, 39 (2016) 8. Hordley, S., Finalyson, G., Morovic, P.: In a multi-spectral image database and its application to image rendering across illumination, multi-agent security and survivability. In: 2004 IEEE First Symposium on, pp. 394–397 (2004) 9. George, S.T., Pedersen, M., Hardeberg, J.Y.: A database for spectral image quality. In: Proceedings of SPIE - The International Society for Optical Engineering, vol. 9396 (2015) 10. Barber, C.B., Dobkin, D.P., Huhdanpaa, H.: The quickhull algorithm for convex hulls. ACM Trans. Math. Softw. 22(469–483), 469–483 (1996)

How Much Time is Required to Achieve a Stable Chromatic Adaptation? Hui Fan, Ming Ronnier Luo(B) , and Yuechen Zhu State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, China [email protected]

Abstract. The frequent question asked to design a psychophysical experiment is the time required for adaptation. Time course is a key parameter to obtain reliable colour appearance data. In this study, a neutral white matching experiment was conducted on a mobile display at two luminance levels under highly saturated adapting illuminants. The results showed that lower display luminance led to higher degree and faster speed of chromatic adaptation. Models to predict the degree of chromatic adaptation over time were derived using a proportional rate growth function. Keywords: Chromatic adaptation · Time course · Highly saturated illuminant

1 Introduction Chromatic adaptation refers to the human visual system’s capability to adjust to the change of colour of illuminants in order to maintain the consistency of perceived colour appearance [1–5]. Generally, it takes a period of time to achieve a stable chromatic adaptation. Various studies have investigated its time-course characteristics. Fairchild and Reniff [6] studied the time course of colour-appearance changes during chromatic adaptation at constant luminance. Three observers tracked achromatic appearance on a CRT display between D65 and 3 illuminants (A, D90, GRN). They concluded that chromatic adaptation at constant luminance was 90% complete after approximately 60 s. Rinner and Gegenfurtner [7] studied the three phases of chromatic adaptation. Observers performed achromatic matching for colour appearance and forced choice for colour discrimination on display along the red–green and blue–yellow axes. They found that the slow phase had a half-life of about 20 s and adaptation had reached steady state within 2 min. Gupta et al. [8] selected 14 test illuminants both on and off the daylight locus and performed achromatic adjustment experiments in immersive illuminants to study time course chromatic adaptation. They found that typically more than 5 min were required for the colour constancy index to stabilize. Nevertheless, the chromaticity of the test illuminants used in the previous studies was rather limited. Chromatic adaptation under highly saturated illuminants and its timecourse effect has not been well studied. So, this study intended to extend the gamut of © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 36–42, 2022. https://doi.org/10.1007/978-981-19-1673-1_7

How Much Time is Required to Achieve a Stable Chromatic Adaptation?

37

the test illuminants for further research. Highly saturated illuminants, especially those close to the boundary of colour gamut were adopted. In this study, a psychophysical experiment was carried out to study the time course chromatic adaptation under different highly saturated illuminants using a neutral white matching method. The effect of test stimuli with different luminance levels was studied. The experimental results revealed the degree of chromatic adaptation in a range of adaptation duration.

2 Experimental 2.1 Test Illuminants and Stimuli The experiment was carried out in a Thouslite viewing cabinet with an 18-channal spectrum tunable LED illumination system. Four highly saturated illuminants close to the spectrum locus were selected as test adapting illuminants, named red, yellow, green and blue. A D65 illuminant was used as baseline illuminant. The illuminance in the center of cabinet was set to about 140 lx, and its mean luminance level was about 44 cd/m2 using CIE 1931 colour matching function (CMF). Table 1 summarizes the chromaticity and luminance of the illuminants used in the experiment. Figure 1 shows the chromaticity coordinates of the 5 illuminants in CIE u’v’ plane and Fig. 2 shows the spectral power distributions (SPD). The measurements were made using a JETI-Specbos 1211 spectroradiometer.

Fig. 1. Illuminants chromaticity on CIE 1976 u’v’ plane

Fig. 2. Spectral power distribution of the adapting illuminants

The experimental apparatus was a calibrated Huawei P20 Pro mobile phone. It was placed vertically in the viewing cabinet. A colour patch was presented on the display by using a 4 cm × 4 cm black mask. The luminance of display was set to two fixed levels: high and low luminance levels at 90 and 9 cd/m2 , respectively. The luminance of display was set at 2 different levels in order to study the effect on the process of chromatic adaptation.

38

H. Fan et al. Table 1. Parameters of ambient illuminants u’

v’

L (cd/m2 )

Red

0.579

0.512

44.5

Yellow

0.188

0.566

43.3

Green

0.037

0.553

44.4

Blue

0.206

0.133

46.1

D65

0.199

0.463

44.1

2.2 Observers and Experimental Procedure Totally 20 observers (7 males and 13 females) participated in the experiment, with ages between 20 and 28 (mean = 24.2, std. dev. = 2.1). Eleven observers each participated in the experiments of low and high display luminance, while two of them participated in both. All the observers passed Ishihara colour vision test. During the experiment, observers sat on a chair and kept their eyes 50 cm from the display screen. They were asked to use a keyboard to control CIELAB a* and b* to adjust the colour on display and match neutral white, i.e. the colour does not possess of hue. The prior training session ensured that observers could finish one match within 1 min. Figure 3 shows the experimental situation.

Fig. 3. Experimental situation

In the real experiment, after 1-min adaptation under D65, observers matched neutral white under D65 twice. Then the illuminant was switched to a saturated one and observers started to match neutral white at once. The average time of one match was about 1 min. After finishing one match, the display screen became dark, during which observers continued to adapt to the illuminant. The total time of one match and adaptation was controlled at 2 min. Hence, the adaptation time was also about 1 min. This cycle (1min match and 1-min adaptation) was repeated 6 times. After finishing the last match, experiment under this test illuminant was completed. So, in the sixth cycle, the adaptation was not needed. Therefore, about 11–12 min were needed to finish under a test illuminant. This procedure was also applied to other test illuminants. The sequence of test illuminants

How Much Time is Required to Achieve a Stable Chromatic Adaptation?

39

was random. Between experiments of 2 test illuminants, observers took a 5-min break and adaptation under D65. Totally 528 matches were made, i.e. 11 observers × 4 illuminants × 2 display luminance levels × 6 repeats.

3 Results and Discussion 3.1 Chromaticity of Matching End Points Figure 4 shows the matching end points under different test illuminants and display luminance levels. It can be seen that matching results with low display luminance were much closer to the chromaticity of test illuminants, which indicates more complete chromatic adaptation.

Fig. 4. Matching results under 4 test illuminants and 2 display luminance levels in CIE1976 u’v’ colour space. (a) high display luminance, (b) low display luminance. ‘×’ represents the chromaticity of test illuminants

3.2 Degree of Chromatic Adaptation by Using CAT16 The degree of chromatic adaptation (D) was calculated using CAT16 [9], and D65 was used as the baseline illuminant. First, use CAT16 to transform matched results under coloured illuminants to the corresponding chromaticity under D65, then optimize D values by minimizing the colour difference CIEDE2000 between transformed results and matched results under D65. D values were calculated for each observer and test illuminant individually. A proportional rate growth function was used to develop the D model, as given in Eq. (1), where t is the adaptation time, and a and b are parameters to be optimized, representing the upper limit and speed of chromatic adaptation respectively. D(t) = a(1 − e−bt )

(1)

Figure 5 shows the fitted time-course D curves of different test illuminants and display luminance levels. Solid curves and dashed curves represent low and high display luminance levels, respectively. It can be found that D values of low display luminance were obviously higher than that of high display luminance, suggesting more complete chromatic adaptation under lower display luminance. For both display luminance levels,

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D values were highest for the blue illuminant, followed by the red, yellow and green illuminants. The phenomenon of high colour constancy of blue illuminant was also found in the previous studies [4, 10]. Note that considering the insufficient energy in blue region of CIE 1931 (2°) CMF, the luminance of the blue illuminant used in this study would be much higher than others when calculated using CIE 1964 (10°) CMF. The present results seem to indicate the higher luminance level of the blue illuminant leads to its higher degree of chromatic adaptation than others.

Fig. 5. Fitted time-course D curves of different test illuminants. Solid curves: low display luminance; dashed curves: high display luminance. Vertical lines: the time reached 90% adaptation upper limit. Solid and circle dots represent the individual D values for low and high display luminance levels, respectively

The speed of chromatic adaptation process can be expressed using the time required to achieve 90% upper limit of chromatic adaptation degree. Table 2 lists the 90% adaptation time for different test illuminants and display luminance levels, and it was also plotted as vertical lines in Fig. 5. It can be seen that higher display luminance corresponds to longer adaptation time, i.e. slower adaptation speed. It could be due to the mix adaptation between test illuminants and the display screen. And the red illuminant required much longer adaptation time than others. Overall, the following conclusions can be drawn from the present study: It took about 1–2.5 min for low display luminance to achieve 90% upper limit of chromatic adaptation degree. For high display luminance, about 1.5–6 min were need. Moreover, the process of chromatic adaptation can be affected by both the chromaticity of ambient illuminants and the luminance of display. When determining the adaptation time in visual experiments, all these factors should be considered in order to achieve more complete chromatic adaptation for observers.

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41

Table 2. Time required to achieve 90% upper limit of D values for different test illuminants and 2 display luminance levels Illuminant

Low display luminance

High display luminance

Red

151 s

369 s

Yellow

45 s

176 s

Green

68 s

184 s

Blue

55 s

81 s

4 Conclusions A psychophysical experiment of neutral white matching was carried out to study the time course of chromatic adaptation under highly saturated adapting illuminants. Models of chromatic adaptation degree against time duration were fitted. It was found that lower display luminance can result in more complete and faster speed of chromatic adaptation. Approximately 1–2.5 min and 1.5–6 min were needed to complete 90% degree of chromatic adaptation for low and high display luminance levels, respectively. Further experiments will be carried out to test more illuminants with more luminance levels and chromaticity distributions. Compliance with Ethical Standards Conflict of Interest. The authors declared that they have no conflict of interest. Ethical Approval. All the procedures performed in the research involving human participants were in accordance with the Academic Rules of Engineering Graduates of Zhejiang University and 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed Consent. Informed consent was obtained from all individual participants included in the study. The image used in the paper was given permission by the participant.

References 1. CIE 160-2004: A review of chromatic adaptation transforms. CIE, Vienna (2004) 2. Wei, M., Chen, S.: Effects of adapting luminance and CCT on appearance of white and degree of chromatic adaptation. Opt. Exp. 27(6), 9276–9286 (2019) 3. Peng, R., Cao, M., Zhai, Q., Luo, M.R.: White appearance and chromatic adaptation on a display under different ambient lighting conditions. Color Res. Appl. 46, 1034–1045 (2021). https://doi.org/10.1002/col.22656 4. Smet, K.A., Zhai, Q., Luo, M.R., Hanselaer, P.: Study of chromatic adaptation using memory color matches, Part II: colored illuminants. Opt. Exp. 25(7), 8350–8365 (2017) 5. Zhai, Q., Luo, M.R.: Study of chromatic adaptation via neutral white matches on different viewing media. Opt. Exp. 26(6), 7724–7739 (2018)

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6. Fairchild, M.D., Reniff, L.: Time course of chromatic adaptation for color-appearance judgments. J. Opt. Soc. Am. A Opt. Image Sci. 12(5), 824–833 (1995) 7. Rinner, O., Gegenfurtner, K.R.: Time course of chromatic adaptation for color appearance and discrimination. Vis. Res. 40(14), 1813–1826 (2000) 8. Gupta, G., Gross, N., Pastilha, R., Hurlbert, A.: The time course of color constancy by achromatic adjustment in immersive illumination: what looks white under coloured lights? bioRxiv (2020) 9. Li, C., et al.: Comprehensive color solutions: CAM16, CAT16, and CAM16-UCS. Color Res. Appl. 42(6), 703–718 (2017) 10. Pearce, B., Crichton, S., Mackiewicz, M., et al.: Chromatic illumination discrimination ability reveals that human colour constancy is optimised for blue daylight illuminations. PLoS ONE 9, e87989 (2014)

Effects of Ambient Illuminance and Luminance Contrast on Visual Comfort for Reading on a Mobile Device Yu Liu and Ming Ronnier Luo(B) State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, China [email protected]

Abstract. Mobile phone reading is becoming increasingly popular. An experiment with twenty young observers was conducted to investigate visual comfort when reading on mobile phones at five different illuminance levels (0, 10, 100, 500, and 1000 lx). The text and background are available in seven achromatic colours of different lightness levels from 0–500 cd/m2 , making up 42 combinations. Each observer evaluated the visual comfort of 50 combinations when reading text using the 6-category points method. It was discovered that observers preferred a grey background to a white or black background. And a lower lightness contrast produces the least visual comfort. Positive lightness contrast around 50 to consistently give visual comfort. When the ambient illuminance reaches 1000 lx, observers feel most visual comfort. Keywords: Visual comfort · Mobile device · Ambient illuminance · Luminance contrast

1 Introduction Nowadays, people are accustomed to reading the news, doing e-shopping on their mobile phones at any time and from any location. To provide visual comfort in diverse ambient lighting circumstances, it is critical to understand the ideal display conditions (such as display brightness, text, and background colour). The contrast between the text and the background had an effect on visual comfort. Greys were discovered to be better background colors than white and black by researchers [1, 2]. It was more comfortable to have a medium or light grey background with a positive polarity arrangement (i.e., light text on a dark background). Lin and Huang [3] investigated visual perception, which was defined as the time it took observers to recognize a stimulus on a TFT-LCD panel with a peak white luminance of 210 cd/m2 . At perception time, they discovered that background luminance of 80 cd/m2 and text luminance of 5 cd/m2 performed well. Several earlier investigations looked into various lighting situations. At a fixed CCT of 6500K, Ou et al. [4] chose four ambient illuminance values (50, 200, 600, and 1200 lx). The findings revealed that reduced illuminance causes more visual discomfort. They [5] also used character identification to explore the effects of ambient lighting conditions © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 43–48, 2022. https://doi.org/10.1007/978-981-19-1673-1_8

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and backdrop color on visual performance with TFT-LCD panels. The best mean character identification performance was 500 lx, followed by 250 and 1000 lx in terms of illuminance intensity. A psychophysical experiment was conducted utilizing mobile phones to investigate the impact of ambient illuminance, as well as the contrast between text and background luminance, on visual comfort.

2 Experimental 2.1 Display Five OPPO Find X3 mobile phones were used in the experiment. They had a peak white luminance of 495 cd/m2 with white point chromaticity (0.3117, 0.3277) (i.e., CCT = 6715K) was used to evaluate the visual comfort. A Konica Minolta CS-2000 spectroradiometer was used to measure all colours in the experiment. As listed in Table 1, seven achromatic colours of different lightness levels were set to evaluate the visual comfort of different text-background combinations. All the combinations of seven achromatic colours produced 42 text-background combinations. Observers evaluated their visual comfort when reading text using a 6-category point scale. 1 - very uncomfortable, 2 - uncomfortable, 3 - a little uncomfortable, 4 - a little comfortable, 5 - comfortable, 6 - very comfortable. Each observer made 50 judgments, including 8 random repetitions under each condition. Table 1. Colourimetric characteristics of the seven colours that were used for the text and background combinations for evaluating the visual comfort of text-background lightness combinations Colour

Luminance (cd/m2 )

CIELAB lightness L*

a

B

white

495

100

0.89

−2.23

grey80

277

80

0.65

−2.46

grey60

137

60

0.67

−2.09

grey50

89

50

0.66

−1.86

grey40

54

40

0.25

−1.20

grey20

14

20

1.35

−0.57

black

0

0.6

0.07

−0.04

2.2 Ambient Illuminance The experiment was carried out in an office. The window was blocked by thick curtains. A Thouslite® spectral tunable LED lighting system installed in the ceiling was used in the experiment. The illuminance levels were 10, 100, 500, 1000 lx with a CCT close to 6500K. Table 2 lists the measured desktop illuminance, CCT, Duv and colour rendering index (Ra) of the ambient lighting conditions. The measurements were made using a JETI-Specbos 1211 spectroradiometer.

Effects of Ambient Illuminance and Luminance Contrast

45

Table 2. Chromaticity characteristics of 4 lighting conditions No.

Illuminance(lx)

CCT(K)

Duv

Ra

1

11

6580

−0.0045

90

2

100

6524

−0.0004

95

3

498

6507

−0.0022

92

4

1010

6507

−0.0039

90

2.3 Observers and Experimental Procedures Totally 20 young Chinese observers (16 males and 4 females) participated in the experiment with ages between 18 and 24 (mean = 19.5, std. dev. = 1.6). All the observers passed the Ishihara colour vision test. The observer read the experiment instructions, filled out a general information survey, and took the Ishihara Color Vision Test when they arrived. The height of each observer’s seat was modified so that their eyes were perpendicular to the phone’s screen. The viewing/illuminating geometry was 0°/45°. During the experiment, observers sat on a chair and kept their eyes 40 cm from the display screen. Observers were asked to look at the screen for 2 min for adaptation. Each observer evaluated the visual comfort of 50 combinations when reading text. The 50 combinations were presented in random order. After evaluating 50 combinations, the observer experienced another 2-min washout period. The same procedure was repeated 5 times. The order of ambient illuminance levels was random. A total of 250 evaluations were made, i.e. 50 combinations (42 combinations + 8 repeats) × 5 ambient illuminance levels. The whole study took about 30 min for each observer.

3 Results and Discussion 3.1 Inter- and Intra-observer Variations The standardized residual sum of squares (STRESS) is shown in Eq. 1 that was used to measure variations of the intra-observer and inter-observer.   n 2 1/2 i=1 (Ai − FBi ) STRESS = × 100 (1) n 2 2 i=1 F Bi   Where F = ni=1 A2i / ni=1 Ai Bi . When the intra-observer variations were calculated, the A and B data were the evaluation of visual comfort obtained from two sets of repeated judgments under the same condition. When the inter-observer variations were calculated, the A and B data were mean and individual observer’s results, respectively. A higher STRESS value indicates a poorer agreement between the two variables. The average intra-observer variations ranged from 6 to 26 (mean = 13, SD = 4) and inter-observer variations ranged from 16 to 49 (mean = 26, SD = 7). IBM SPSS 22® software was used to analyze the data. ANOVA of ‘ambient illuminance’ (0, 10, 100, 500, 1000 lx) were applied.

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(a)

(b)

(c)

(d)

(e) Fig. 1. Average visual comfort plotted against lightness difference between text and background on the screen of display luminance of 500 cd/m2 under each ambient illuminance: (a) 0, (b) 10 lx, (c) 100 lx, (d) 500 lx, (e) 1000 lx; The coloured lines of black, grey, blue, magenta, cyan, green and yellow represent the background L* values of 0.6, 20, 40, 50, 60, 80, 100, respectively; Error bars show the 95% confidence intervals

3.2 Effect of Background Colour and Contrast on Visual Comfort The lightness contrast is defined by the lightness of text (L* Text ) minus the lightness of the background (L* Background ). As shown in Fig. 1(a)–(e) from dark 0 to bright 1000 lx levels, the visual comfort for each background colour were plotted against lightness difference. All figures are similar in shape. As the absolute value of contrast increases, the score rises then it falls. And a lower lightness contrast produces the least visual comfort. Positive lightness contrast around 50 to consistently give visual comfort. As the ambient illuminance grows, the white background score rose as well. The black background score falls below that of the grey background as the ambient illuminance raises.

Effects of Ambient Illuminance and Luminance Contrast

47

3.3 Effect of Ambient Illuminance on Visual Comfort Figure 2 shows the mean visual comfort results plotted against ambient illuminance. The 1000 lx visual comfort score is higher than in other settings. And visual comfort score of darkness is lower than other circumstances (p < 0.001). It is clear that the higher the illuminance level, the greater the visual comfort. As mentioned before, there was a trend that visual comfort of 600 lx was a little higher than 1200 lx, 200 lx and 50 lx according to Ou et al.’s [1] experiment. Our experiment had a much clearer trend that visual comfort of 1000 lx was significantly higher than other conditions, as shown in Fig. 2.

Fig. 2. Visual comfort plotted against ambient illuminance. *** Showing visual comfort score of 1000 lx is higher than other conditions and visual comfort score of darkness is lower than other conditions (p < 0.001). Error bars show the 95% confidence intervals.

4 Conclusions A psychophysical experiment was carried out to study the visual comfort of 20 young observers when reading on OPPO Find X3 under various illuminance levels (0, 10, 100, 500 and 1000 lx). It was found that the observers feel more comfortable reading documents that had a grey background than reading those with a background colour of either white or black. Observers feel most comfortable when ambient illuminance reached 1000 lx when display luminance reached 500 cd/m2 . Acknowledgements. The authors like to thank the support of OPPO Guangdong Mobile Telecommunications Co., Ltd.

References 1. Ou, L.C., Sun, P.L., Huang, H.P., Luo, M.R.: Visual comfort as a function of lightness difference between text and background: a cross-age study using an LCD and a tablet computer. Color. Res. Appl. 40(2), 125–134 (2015). https://doi.org/10.1002/col.21873

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2. Huang, H.P., Wei, M., Ou, L.C.: Effect of text-background lightness combination on visual comfort for reading on a tablet display under different surrounds. Color Res. Appl. 44, 54–64 (2018). https://doi.org/10.1002/col.22259 3. Lin, C.C., Huang, K.C.: Effects of color combination and ambient illumination on visual perception time with TFT-LCD. Percept. Mot. Skills 109(2), 607–625 (2009). https://doi.org/ 10.2466/pms.109.2.607-625 4. Huang, H.-P., Yuan, Y., Ou, L.-C.: Effects of age and ambient illuminance on visual comfort for reading on a mobile device. Color Res. Appl. 42, 352–361 (2017). https://doi.org/10.1002/ col.22089 5. Shen, Y., Shuguang, K., Zhou, W., Peng, S., Tian, M., Liu, K.: Study of preferred background luminance in watching computer screen in children. Chin. Med. J. 127(011), 2073–2077 (2014). https://doi.org/10.3760/cma.j.issn.0366-6999.20133232

Evaluation of Primaries for Display Colourimetry Lihao Xu1(B) and Ming Ronnier Luo2 1 School of Digital Media and Art Design, Hangzhou Dianzi University, Hangzhou, China

[email protected] 2 State Key Laboratory of Modern Optical Instrumentation, Zhejiang University,

Zhejiang, China

Abstract. In this paper, a workflow was proposed for rendering images from standard signals using various sets of primary combinations and various tests were devised to fully investigate a display’s color rendering capability. The current results show that three testing metrics, namely color fidelity, color gamut, and real surface color coverage, can be effectively used to predict a display’s color performance. Keywords: Display primary · Colourimetric performance

1 Introduction The selection of primaries is critical for a display to deliver good color image quality. Following the de facto standard, i.e., sRGB [1], is a common way to select the primaries. However, various technologies, such as OLED, QD-LED, and laser displays, are emerging, and each one results in a distinct primary combination. This results in color distortions such as oversaturation, hue shift, and a lack of naturalness [2]. To address this issue, an increasing number of standards or recommendations, such as DCI-P3 [3], were proposed. All of them had fixed RGB primary color combinations. Although they can help to reduce color distortions, actual products may not achieve the same primaries as described due to economic considerations. Hence, it is critical to evaluate the displays with various primaries. In this study, we proposed a systematic methodology for evaluating the color rendering performance of a display. This strategy was divided into three parts. To begin, a display characterization model was developed by combining the primary display combination with an Electro-Optical Transfer Function (EOTF) from the sRGB standard. Afterwards, seven tests were carried out to fully validate a display’s color rendering capability. Finally, testing results were analyzed to determine the dominant factors influencing overall display performance. The current results supported the efficacy of this method, and four testing metrics, namely color fidelity, color gamut, and real surface color coverage, were discovered to be critical in evaluating the color rendering performance of a display. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 49–53, 2022. https://doi.org/10.1007/978-981-19-1673-1_9

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2 Method 2.1 Display Characterization RGB primaries and an EOTF comprise a full display characterization model. The same EOTF was used as the sRGB standard in this study. This research includes 30 RGB primary color combinations, each of which can be thought of as an imagery LCD display. They were all provided by a display manufacturer and are all ready for mass production. Their location was near the sRGB and DCI-P3 primaries. All of these primaries are clearly centered on these two criteria. The white of all of the displays studied was set to D75 and 480 cd/m2 to match the real-world conditions for mobile phone screens. 2.2 Testing Metrics Two types of testing metrics were developed in this study: gamut metrics and color related metrics. The former was to investigate the color rendering capability of the display, i.e., the number of colors that the display can reproduce, and the latter was to investigate the color fidelity associated with a given display. Gamut metrics are divided into four categories: gamut area ratio, NTSC gamut coverage, gamut volume ratio, and actual surface color coverage. The gamut area is a commonly used metric for determining a display’s color rendering capability. It is defined as the area of the RGB main triangle in the CIE 1976 u’v’ chromaticity diagram, which is more uniform than the CIE 1931 xy diagram. However, a volumetric difference produced by a change in luminance level does not appear in a chromaticity diagram. Hence, another often used metric, i.e., the gamut volume ratio, was also included. Since the CIELAB is most widely used in the imaging industry, it was finally selected to make a better communication. NTSC is a widely used metric to describe a display’s colour rendering capability by the market. The NTSC coverage was obtained by dividing the overlapping area by the NTSC gamut area. A new metric, i.e., coverage of real surface colors, was also included. Real surface colours refer to the colours from the surface of real objects [5]. The dataset used in this study is consisting of 102,801 colours and each of them is expressed as a spectrum function. It was calculated as the overlapping volume divided by the real surface colour gamut. Three types of tests were developed for color-related metrics including color compatibility, color deviation, and hue linearity. Color compatibility is measured as the color difference between a standard and a test display when identical signals are presented. Two test datasets were used including a Machbetch ColorChecker Chart (MCCC), and an 18 * 18 * 18 evenly spaced RGB cube. In addition, a psychophysical dataset, namely memory colours [6] was also included. Memory colours can be defined as a phenomenon in which we link a specific colour with a specific thing in our thoughts. Figure 1 depicts all of the test objects. A blackwhite image was presented here since readers can easily recognize all the objects and related them with certain memory colours. One thing should be noted is that, although the memory colours were illustrated using images, they were calculated using a fixed colour in the test.

Evaluation of Primaries for Display Colourimetry

51

Fig. 1. Memory colours tested

Fig. 2. Datasets to test the hue shift. The white dashed lines represent the const hue loci and the dots represent the unique hue data

The const hue loci [7] was used to test the hue change. The distance from the constant hue loci to the new primary was used as a metric to represent the hue shift. A larger distance indicates poor performance. Another test, namely the unique hue data [8], was also included. It is consisting of four unitary colours, i.e., pure red, pure green, pure yellow and pure blue. These two sets of data are different since the primaries from sRGB are not unitary colours and they are shown in Fig. 2.

3 Results and Discussion All the imagery displays were tested using these metrics. The results were ranked to show the merit of all the displays. Further, all the ranks were summed up to represent the overall performance. A higher sum means a worse performance and it was illustrated in Fig. 3. As is shown, the first two displays had a better performance in colour fidelity, followed by another two displays having a larger gamut. And it should be noted that, the results of gamut metrics and colour related metrics were not bad, indicating it is possible for a display to have a high colour fidelity while to give a large colour gamut.

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Fig. 3. The testing results for all the 30 displays. The bar in black represents the result for gamut metrics and the bar in white represent the result for gamut related metrics

Table 1. Rotated component matrix of PCA. Total variance explained of each factor is shown in the bracket. RSCC means real surface colour coverage. Group

Test

Colour-related

MCCC

0.99

−0.03

RGB cube

0.98

0.05

Gamut

Factor 1 (61%)

Factor 2 (31%)

Const hue loci

0.94

−0.02

Unique hue data

0.92

−0.29

Memory colour

0.90

0.13

−0.68

0.62

GA ratio

0.10

0.97

GV ratio

0.18

0.97

−0.53

0.81

NTSC coverage%

RSCC

Principle component analysis (PCA) was used to further analyze the data. The underlying components are shown in Table 1. The first factor was obviously linked to the concept of “colour accuracy,” implying that a display should render colours as closely as possible to a standard display. The second factor was strongly linked to “gamut volume,” meaning that a wider gamut was preferred. These two factors were clearly mutually exclusive, and one must strike a decent balance between them. Further, while real surface color coverage showed a somewhat high correlation with the second factor, its connection with the first factor was not trivial, indicating that it cannot be easily classified into any category. As a result, it was presented as a separate factor to consider when designing a display.

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53

As a result, it’s proposed to evaluate a display’s performance in three areas, i.e., colour fidelity (Factor 1), gamut volume (Factor 2), and real surface color coverage. The result of the NTSC Coverage test is considerably different from the results of the other tests, so it is not recommended at this time.

4 Conclusions In this paper, the performance of displays was studied in terms of its RGB primaries. Seven test metrics were implemented and they can be divided into 2 groups, i.e., gamut metrics and colour related metrics. According to our findings, three primary attributes, namely colour fidelity, colour gamut, and real surface colour coverage, were the most important aspects influencing display performance. Acknowledgements. This study is supported by the Fundamental Research Funds for the Provincial Universities of Zhejiang (GK219909299001-019).

Statement of Ethical Approval. The authors declare that they have no conflict of interest. This article does not contain any studies with human participants or animals performed by any of the authors. Informed consent was obtained from all individual participants included in the study.

References 1. Stokes, M., Anderson, M., Chandrasekar, S., Motta, R.: A standard default color space for the internet—sRGB. Intl. Color Consortium (1996) 2. Trémeau, A., Charrier, C.: Influence of chromatic changes on the perception of color image quality. Color Res. Appl. 25, 200–213 (2000) 3. RP 431-2:2011 - SMPTE recommended practice - D-cinema quality—reference projector and environment (2011). https://doi.org/10.5594/SMPTE.RP431-2.2011 4. Li, C., Luo, M.R., Pointer, M.R., et al.: Comparison of real colour gamuts using a new reflectance database. Color Res. Appl. 39, 442–451 (2014) 5. Zhu, Y., Luo, M. R., Xu, L., et al.: Investigation of memory colours across cultures. In: 23rd Color and Imaging Conference, pp. 133–137 (2015) 6. Masaoka, K., Nishida, Y., Sugawara, M., et al.: Design of primaries for a wide-gamut television colorimetry. IEEE Trans. Broadcast 56, 452–457 (2010) 7. Zhao, B., Luo, M.R.: Hue linearity of color spaces for wide color gamut and high dynamic range media. J. Opt. Soc. Am. A 37, 865–875 (2020)

Color Reproduction Analysis for 3D Printing Based on Photosensitive Resin Xiaomeng Han, Yijie Ren, Yibo Wang, Jinze Wang, Yifan Xiong, Guangyuan Wu, and Xiaozhou Li(B) School of Light Industry Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China [email protected]

Abstract. With the continuous innovation and development of printing technology, full-color 3D printing has gradually become the development trend of the industry. Although full-color 3D printing has been realized, there is still a lack of technology to accurately evaluate color reproduction for 3D printing objects. In this paper, the common color properties, i.e., color gamut, spectral reflectance and chromaticity were chosen to analyze color reproduction for 3D printing of photosensitive resin and digital printing of inkjet and electrostatic methods. It shows that the color reproduction of 3D printing based on photosensitive resins has a good performance. It is helpful to develop the color management for 3D color printing. Keywords: 3D color printing · Color reproduction · Color evaluation · Photosensitive resin

1 Introduction 3D printing technology is a kind of material adding manufacturing technology integrating intelligence, industrialization and diversification. Because of its advantages of strong practicability, low energy consumption and simple operation, 3D printing technology has been widely used in medical, educational, construction and other industries [1]. With the rapid development of the material adding manufacturing industry, full color and highprecision 3D printing technology has become the trend of industry development [2]. CIE listed accurate measurement and real reproduction of 3D object appearance as one of the ten research hotspots in 2016. And CIE TC8-17 Technical Committee was established to conduct standardization research [3]. Carina Parraman evaluated the color of the powderbased printing products [4]. Yuan, J, P. used a specific three-dimensional color standard model to calculate the main visual image [3]. However, the average structure similarity, feature similarity and visual difference are relatively independent in color reproduction evaluation. In this paper, J750 3D printer was used to output the full color 3D image. The common color evaluation parameters, i.e., color gamut, chromaticity and spectral reflectance were chosen to analyze the color reproduction for 3D printing based on photosensitive resin. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 54–58, 2022. https://doi.org/10.1007/978-981-19-1673-1_10

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55

2 Experiment 2.1 Equipment IT8.7/3 test chart was used to describe the color reproduction of 3D printing, digital inkjet printing and digital electrostatic printing. Equipments used in this paper were shown in Table 1. Table 1. Experimental equipment Equipment

Model

Manufacturer

3D printer

PolyJet J750

STRATASYS

Digital inkjet printer

iPF8300

Canon

Digital Accurio Press Konica Minolta electrostatic printer C6100 Spectrophotometer eXact

X-Rite

Digital Microscope BL-SC1600

BELONA

2.2 3D Color Blocks Acquisition The 3D model for IT8.7/3 is designed with C4D software, and the graphics are exported to WRL format. Then the model is imported into the Grab CAD slicing software, and the color configuration file used in the slicing software is Natural shells (Vero materials). Finally, the samples are transferred to J750 printer for printing. The output completed by 3D printing is shown in Fig. 1.

Fig. 1. 3D printer working process

2.3 Test-Chart Output Inkjet printing paper with 100 g/m2 , electrostatic printing paper with 160 g/m2 were selected to work as the references for 3D printing. For 3D printing, the size of color

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block was set as 0.6 cm × 0.6 cm × 0.2 cm. Spectrophotometer was used to measure the spectral reflectance and color chromatic coordinates. The test charts outputted by 3D printing was shown in Fig. 2.

Fig. 2. Outputted test chart for 3D printing of photosensitive resin

3 Data Analysis and Discussion 3.1 Color Gamut The pairwise comparisons of color gamut are shown in Fig. 3. The color gamut of 3D printing based on photosensitive resin is similar to the gamut of inkjet printing and electrostatic printing. However, it is easy to find the gamut of 3D printing based on photosensitive is smaller.

Fig. 3. Gamut comparison diagram

3.2 Chromaticity The chromaticity coordinate charts show the different a* b* range in Fig. 4. The chromatic distribution of 3D printing based on photosensitive resin in a* b* plane is similar to common digital printing methods but smaller. It shows the possibility to use similar color management method to manage color transfer process and color reproduction.

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Fig. 4. Chromaticity chart

3.3 Spectral Reflectance The spectral reflectance is shown in Fig. 5. It shows that it is different for the three output methods. The reflectance is similar for the common digital printing methods. However, it has an obvious difference for the 3D printing based on photosensitive resin. The experimental result shows the paper reflectance is affected by the fluorescence, which has some reflectance higher than 1. It is caused by the adding fluorescent materials into the paper making process which can improve the paper optical properties. The normalized experimental data are shown in Fig. 5.

Fig. 5. Spectral reflectance: (a) 3D printing; (b)inkjet printing; (c)electrostatic printing

3.4 Microstructure of Surface For 3D printing, the substrate is different from the common digital printing materials. The color 3D printed object is formed by the photosensitive resin. We can find the color reproduction is different from the common color reproduction in the object surface, as shown in Fig. 6. These pictures of micro-surface were captured by the digital microscope, BL-SC1600, BELONA. The paper surface has more pores between the fibers while the resin surface has no pores and has a smoother surface. When the ink meets the paper surface, the ink will spread on the paper surface, be absorbed by the fibers and penetrate into the pores. The color reproduction is affected by the paper and ink simultaneously. For 3D printing of photosensitive resin, the surface has no pores and is smoother than the paper surface. So, the inks only spread on the surface of resin. The color reproduction is affected by the reflectance of resin and the pigment or ink adhered on the surface.

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Fig. 6. Microstructure: (a) is Photosensitive resin, (b) is electrostatic printing paper, (c) is inkjet printing paper, (d) is 3D printed surface, (e) is electrostatic printed surface, and (f) is Inkjet printing surface

4 Conclusions We all know full color 3D printing technology has been widely used in creative fields. In this paper, spectrophotometer is used to measure color properties of photosensitive resin, and color reproduction of 3D printing is compared with common digital printing methods. The results show that although the color gamut, a*b* chroma and spectral reflectance of 3D printed samples are different from digital printing, they can also play a role similar to common printing. We can use test diagrams to build 3D printing representations based on photosensitive resins to help manage the color reproduction of 3D printing. Acknowledgements. This work was supported by the project of Key Research and Development Program of Shandong Province (No. 2019GGX105016), Shandong Provincial Natural Science Foundation (No. ZR2020MF091), and Undergraduates’ Innovation and Entrepreneurship Training Program of Qilu University of Technology (No. xj202010431073), Foundation (No. ZZ20210108) of State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences.

References 1. Liu, C.X., Kang, H.J.: 3D printing technology and its application in medical field. J. Materials Eng. 06, 66–67 (2021) 2. Chen, G.X., Chen, C., Yu, Z.H.: Color 3D printing: Theory, Method and Application. M. 26–50 (2016) 3. Yuan, J.P.: Color reproduction evaluation of paper based full color 3D printing based on image quality measurement. J. Digital Printing 05, 26–34 (2020) 4. Parraman, C., Walters, P., Reid, B.: Specifying colour and maintaining colour accuracy for 3D printing. In: Proceedings of SPIE the International Society for Optical Engineering, 6805(68050L-68050L-68058) (2008)

Optical Properties of Periodic Columnar Structures with Structural Colors Using Pattern Transfer Technology Xiaoxue Hu, Yeqi Wang, Min Huang, Yu Li, Yu Wang, Junxiao Lu, and Xiu Li(B) School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. Structural colors generated by photonic crystals have become the focus of research in recent years due to its promising advantages of long-term stability and environmentally friendly properties compared with conventional pigments and dyes. The band gap range of photonic crystals can be controlled by changing the structure parameters of photonic crystals, and then the color of photonic crystals can be modulated. In order to study the influence of different structures on the color of photonic crystals, this study obtains periodically arranged cylindrical photonic crystals by copying the pore structures. In addition, the reflection spectra and microstructure were analyzed. The results show that the spectral half-width of the cylindrical photonic crystal is somewhat wider than that of the master plate, and the spectral reflectivity is reduced. When the incident angle increased from 15° to 45°, the wavelengths of structural colors move to longer wavelength at different viewing angles after duplicate process. The project introduces a fabrication method of two-dimensional photonic crystals, which has broad application prospects in green printing, imaging, security and other fields. Keywords: Photonic crystal · Structural color · Periodic structure · Nanophotonic structures

1 Introduction Recently, plasmonic nanostructures have been very actively researched for structural color generation, which was earlier realized by photonic crystals [1–6]. Nanostructural coloration, especially photonic crystals color generation, has received increasing attention in recent years due to its potentially environmental friendly colors [7–10]. Such artificially designed nanophotonic structures are useful for controlling the spectral properties of transmission, reflection, and absorption in the visible spectral regime by modifing their design parameters. Therefore, the photonic crystal structure that constitutes the structural color must have an accurate size to achieve high optical performance [5, 6]. Therefore, the fabrication and control of the photonic crystal structure is required strictly. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 59–63, 2022. https://doi.org/10.1007/978-981-19-1673-1_11

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The preparation methods of photonic crystals mainly include bottom-up preparation, top-down preparation, template-assisted preparation and inkjet printing [2]. At present, the most mainstream methods are electron beam etching and nano-imprint, but these methods have disadvantages such as high cost of equipment, low production efficiency and high requirements for experimental design. Wen hong Yang [7] et al. used electron beam lithography to generate structural color on silicon surface, and added a refractive index matching layer to increase the color gamut area of the sample. The obtained color has high reflectivity and high saturation; Takeda [5] et al. used UV nanoimprint technology to prepare a micro-nano structure, which can adjust the color by changing the size of the structure, and achieve a wide range of adjustment of reflected color. However, the above two methods have strict requirements on equipment and high production cost, so they are not suitable for mass production. In this paper, two-dimensional photonic crystals with columnar structure are obtained by using the method of repeated fabrication of the periodic arrangement of holes. The method is easy to operate, high repeatability and suitable for flexible substrates. The two-dimensional structure exhibited brilliant and vivid colors, and various structural colors could be adjusted by controlling the viewing angles.

2 Experimental Sets Up The structural color master plate used in this experiment is provided by Shanghai Na teng Instrument Co., Ltd. Silicon is used as the substrate, as shown in Fig. 1(a), and the schematic of the periodic nanostructure we designed is shown in Fig. 1(b), where the periodicity is 460 nm, the depth of the holes is 200 nm and the diameter of the holes is 230 nm.

Fig. 1. Structure color master appearance. (a) appearance diagram of structural color master with 460nm period; (b) 3D structure of structural color master

The experimental process is shown in Fig. 2. Firstly, the silicon mold with periodic holes is placed in a container, then a certain amount of Polydimethyllsiloxane (PDMS) is coated on the master plate, and then cured by high temperature heating. After curing, the PDMS is separated from the silicon mold, and the inverse patterns can be transferred to the PDMS, that is, the two-dimensional columnar photonic crystals with a height of 200 nm and a period of 460 nm can be obtained. Finally, a sputtering meter (SBC-12, Beijing Zhong ke Instrument Co., Ltd.) was used to gild the duplicated sample, and the sputtering time was 10S, 20S, 30S, respectively. The five samples are named from sample 1 to sample 5 for master, unprocessed copy, sputtering time of 10S, 20S and 30S, respectively.

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Fig. 2. Schematic diagram of the fabrication process of structural color; photographs taken with a mobile phone: (e) the silicion mold; (f) inverse patterns by PDMS; (g) 10S sputtered sample; (h) 20S sputtered sample; (i) 30S sputtered sample

3 Results and Discussion The angle-resolved spectrum system with the light source of deuterium/halogen from Shanghai Fuxiang Co. Ltd was adopted in the reflectance measurement at fixed and different viewing angles, as shown in Fig. 3.

Fig. 3. Reflectance spectra of the 5 samples at different viewing angles: (a) the silica mold; (b) the peak position of the master spectrum changing with viewing angle; the reflection spectrum of five replicas under (c) 15°, (d) 30°, and (e) 45° specular reflection angles

Figure 3(a) shows the spectrum of the silicion mold with periodically arranged holes. In the specular reflection direction, the spectral waveform is roughly the same, but the peak position changes with different viewing angles. When the incident angle increases from 15° to 30°, the peak values of reflectance spectra decrease continuously from 566.5 nm to 515.4 nm (showing a blue shift), corresponding to the colors of yellowish green and green, respectively. Figure 4(b) shows a line chart of spectral peak changes with various incident angles, the peak value decreases firstly and then increases along with increasing incident angles. Figure 3(c), (d), and (e) show the reflectance spectra of the 5 samples mentioned above at three angles of 15°, 30°and 45° specular reflection direction, respectively. The peak positions of the samples without and with gold sputtering remain unchanged at all angles, while the spectral energies are different. When the incident angles are 15°, 30° and 45°, the peak positions of the four samples sputtered by gold are 559.4 nm,

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558.6 nm, and 559.4 nm, respectively. It can be inferred that the reflectance spectra of the replicas didn’t change with the viewing angles. Compared with the silica mold, the FWHM (full width at half maximum) of the reflection spectrum of the duplicated plate is greater at all angles. Figure 4 shows the SEM images ((SU8020, HITACHI)) of the structural color master and the duplicated samples, having diameters of D = 230 nm for a period of P = 460 nm. The depth of the holes were measured to be H = 200 nm, as intended. In Fig. 4(a) and (b), it is observed from the top view of the fabricated samples that well-defined circular patterns are periodically arranged in a hexagonal lattice, and the fine columnar patterns are successfully fabricated, exhibiting a high fidelity to the design.

Fig. 4. SEM images: (a) the structural color master plate; (b) the copy of a structural master plate of a gold-plate sample

4 Conclusions In this paper, the periodic arrangement of cylindrical photonic crystals was obtained by copying the pore structure on silicon surface and the spectral reflectance and microstructure at different angles were measured respectively by using angular resolution spectrophotometer and scanning electron microscope. The results showed that the spectral half-width of the duplicated version was wider than that of the master version, and the spectral reflectivity was reduced, the maximum spectral reflectance of master version is 663.57, the maximum spectral reflectance of the four copies is 342.02, 264, 307.26 and 262.44 respectively. By scanning electron microscopy we can see that there are obvious structural defects in parts of the copy. Although the periodicity of the duplicated plate is obvious, the structure size is small, and defects are likely to appear in the replication process, which will affect the optical properties of the duplicated plate, leading to problems such as half-height width expansion of the reflection spectrum or peak deviation. Secondly, because PDMS is a high transmittance material, and the master plate is made of a material with high reflection, the spectral response sensitivity of the copied plate is not obvious, resulting in a low spectral reflectivity of the copied plate. In summary, a simple method to produce two-dimensional photonic crystal is proposed in our research by using PDMS to obtain the cylindrical photonic crystals. While, this project still needs to be further improved and has great development prospects in green printing, image, anti-counterfeiting and other fields.

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Acknowledgements. This work was supported by the National Science Foundation of China (No. 61805018), College’s Scientific Research Project (BIGC Ec202003, BIGC Eb202102), and General program of science and technology development project of Beijing Municipal Commission (KM20190015008).

References 1. Rezaei, S.D., et al.: Nanophotonic Structural Colors. ACS Photonics 8(1), 18–33 (2020). https://doi.org/10.1021/acsphotonics.0c00947 2. Yang, B., Cheng, H., Chen, S., et al.: Structural colors in metasurfaces: principle, design and applications. Mater. Chem. Front. 3(5), 750–761 (2019). https://doi.org/10.1039/c9qm00 043g 3. Yang, B., Liu, W., Li, Z., et al.: Ultrahighly saturated structural colors enhanced by multipolarmodulated metasurfaces. Nano Letter 19(7), 4221–4228 (2019). https://doi.org/10.1021/acs. nanolett.8b04923 4. Kristensen, A., Yang, J., Bozhevolnyi, S.I., et al.: Plasmonic colour generation. Nat. Rev. Mater. 2(1), 1–14 (2016). https://doi.org/10.1038/natrevmats.2016.88 5. Takeda, M., Takahara, R., Hasuike, N.: Plasmonic color pixels fabricated by nanoimprint process. Opt. Rev. 27(5), 427–431 (2020). https://doi.org/10.1007/s10043-020-00610-y 6. Xuan, Z., Li, J., Liu, Q., et al.: Artificial structural colors and applications. The Innovation (2021). https://doi.org/10.1016/J.XINN.2021.100081 7. Yang, W., et al.: All-dielectric metasurface for high-performance structural color. Nat. Commun. (2020). https://doi.org/10.1038/s41467-020-15773-0 8. Sun, S., et al. All-Dielectric Full-Color Printing with TiO2 Metasurfaces. ACS nano, (5) (2017). https://doi.org/10.1021/acsnano.7b00415 9. Zhu, X., Vannahme, C., Hjlund-Nielsen, E., et al.: Plasmonic colour laser printing. Nature Nanotechnology 11(4), 325–329 (2016). https://doi.org/10.1038/NNANO.2015.285 10. Zhu, X., et al.: Resonant laser printing of structural colors on high-index dielectric metasurfaces. Sci. Adv. (5) (2017). https://doi.org/10.1126/sciadv.1602487

Study on Color Consistency Reproduction Method of Decorative Material Surface Based on UV Inkjet Printing Yan Liu1(B) and Quanhui Tian2 1 Printing and Packaging Engineering Department, Shanghai Publishing and Printing College,

Shanghai, China [email protected] 2 Intelligence and Information Engineering Department, Shanghai Publishing and Printing College, Shanghai, China

Abstract. This paper studies a method of using an improved color management process to achieve the consistent color reproduction of decorative materials based on UV inkjet printing. Due to the difference in surface characteristics of different decorative materials, it is difficult to reproduce the color with the original decorative materials by using the conventional color management technology. Based on the decorative material reproduction process, this paper first establishes the scanner calibration profile SP Profile through a specific color table file, then builds the device-associated profile file Device Link, and finally uses the device-associated profile file to control the print output, so as to achieve the purpose of the decorative material surface color consistent reproduction. Keywords: Decorative material · Color management · UV inkjet printing

1 Introduction UV inkjet printing technology refers to the digital processing of the images needed to be printed through digital cameras, scanners and other input devices, and then store them in the computer. Or use computer-aided technology (Photoshop, Painter, etc. software) to directly design patterns After grating treatment, input the pattern into the inkjet printing system to start printing. And use the ultraviolet radiation of the UV lamp to quickly cure the UV ink on the surface of the substrate [1–3]. As the application of UV digital inkjet printing technology in furniture, floors, doors and windows continues to expand, the requirements for color management and optimization in the inkjet process are also increasing, with the goal of ensuring the image accuracy and color quality of the inkjet printing patterns [4, 5]. This article is based on the basic process of UV inkjet printing. On the basis of the conventional digital printing pattern color management process, an improved color management scheme is developed to improve the accuracy and printing efficiency of image color reproduction on the surface of different decorative materials. The color management process first establishes the © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 64–70, 2022. https://doi.org/10.1007/978-981-19-1673-1_12

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scanner calibration profile SP profile through a specific color table file, and then builds the device-linked profile. Finally, the device-linked profile is used to control the print output to achieve consistent color reproduction on the surface of the decorative material. The purpose is to solve the existing problem of inconsistent image color reproduction caused by different decorative materials.

2 Process and Method Research 2.1 Process Analysis of UV Inkjet Printing The general workflow of UV inkjet printing is: (1) Preparation and treatment of substrate. Including selecting the base material. Cutting into regular size, coating the back cover putty, cleaning the dust and special treatment; (2) Making digital printing decoration pictures. Including determining the style according to the product effect; scanning, photographing, and software digitization processing; image processing to make a print image format; color management confirmation; (3) Digital printing UV decorative layer. Including RIP software input picture, printing mode selection, workpiece positioning, UV inkjet printing equipment output; (4) post-process. Refers to special finished products that need to be processed by manual techniques or reprocessed with other equipment; (5) Surface treatment. Including standing in a ventilated place, spraying primer, topcoat or spraying other protective layers; (6) Finished product processing. Refers to the addition of other parts, accessories, etc. [6]. In the UV inkjet printing process, the input, display and output devices (scanners, monitors, digital inkjet printers, etc.). The colors space and color performance capabilities of these devices are different. So, it is necessary to formulate a reasonable color management process to scan and collect the surface patterns of decorative materials and intervene and process the colors of digital inkjet printing in order to achieve consistent color reproduction of the surface images of decorative materials [6, 7]. 2.2 Conventional Color Management Process First, use the conventional color management process to simulate the reproduction of the surface pattern of the decorative material. The main steps are: (1) Calibrate input devices, displays, and output devices, including calibration of brightness, saturation, black and white levels, etc.; (2) Establish characteristic files for each device; scan standard charts, and perform color values and values according to the standards. Standard color contrast, establish the ICC profile of the scanner. Calibrate the display, adjust its color to be consistent with the output requirements, establish a color description file for the display; characterize the output device inkjet printer, and establish a color description file. (3) Color conversion between equipment and printing substrate. Select a standard characteristic file equivalent to the actual printing substrate, perform image color separation and conversion, and complete the printing output.

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2.3 Improved Color Management Process The improved color management process proposed in this study is to construct a Device Link Profile in the process of conventional color management, and use the Device Link Profile to control the print output to achieve the purpose of consistent color reproduction on the surface of the decorative material. Specific steps are as follows: 1.

Adjust the scanner to the regular scanning state, and adjust the inkjet printer to the actual production printing state; 2. Use the color table image (a total of 3024 color blocks) that comes with the scanner to create the original color table image file 1; 3. Use inkjet printer conventional printing materials and actual printing methods to realize the print output of original color mark image file 1; 4. Scan and print the original color table 1. And save the file format as *.tif; 5. Measure the printed color table 1. And obtain the printed LAB data of the color; 6. Create the scanner calibration ICC 1 file, named SP profile based on the scanned and measured database of color table 1; 7. Print the standard color table image file 2 (ISO standard eciRGB_v2 color table) by using UV inkjet printer; 8. Scan the printed standard color table image file 2 eciRGB_v2 color table, use the scanner, load SP profile for scanning input; 9. Create a Device Link Profile based on the scanned standard color table image file 2 eciRGB_v2 and the ISO standard data of the standard color table file 2; 10. Scan an original decorative material with a high-precision scanner; 11. Convert the scanned image profile into eciRGB_v2.icc in Photoshop. Then choose the created Device Link Profile in the advanced setting option Device Link of the converted profile; 12. Use an inkjet printer to output the original image on the corresponding printing material according to the actual printing method. Figure 1 is the workflow of the improved color management process. 2.4 Characteristics and Advantage of the Improved Process Most of traditional decoration processes have long cycles, high costs, and low efficiency, and cannot meet the needs of individualized markets, green environmental protection, and rapid production [8, 9]. Compared with the traditional decoration technology, UV inkjet printing technology has the characteristics of adapting to a wide range of materials, no plate- making, direct printing, good quality of inkjet patterns, and strong performance of details [6, 10]. It has great advantages in the application of furniture and wood products [11]. Compared with the conventional color management process, the improved process carries out accurate color matching between scanner and printer to protect the color saturation, controls of K channel independently, saving ink consumption, and achieves better reproduction effect of layer group section. Improved color reproduction and visual matching [12].

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Fig. 1. Workflow of the improved color management process

3 Results In order to compare the effects of two different color management processes on the color reproduction of decorative material surface patterns, this paper uses these two process schemes to use paper to simulate the surface pattern of decorative materials and output the color table. A comparative study is made on the color difference and visual effects. For ease of presentation, the conventional color management process is referred to as process A in this paper. The improved color management process is referred to as process B. The input device used in this paper is Metis DRS 2020 DCS platform scanner, and the inkjet printer is Canon Pro-540. 3.1 Color Difference Comparison In order to compare the results of two different replication schemes, this paper uses two methods to output the test color table that comes with the scanner [13]. The color values on the color table are measured separately. The color table output in different ways is calculated between the color table and the standard color table. Color difference, analyze the influence of different color management processes on color consistency reproduction through the distribution of color difference.

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It can be seen from Fig. 2 that the color difference of process A is mainly distributed around 3E00 , and the color difference of process B is mainly distributed around 2E00 . The proportion of the color difference E00 of the measurement sample in the process A that is less than 6 is 70%, and the color difference E00 of the 93% of the measurement samples in the process B is less than 6. It can also be seen from the histogram of the frequency distribution that the maximum color difference in conventional color management copying has reached 15E00 , and the quality of the copying process is also less stable than the improved color management process [14, 15].

Fig. 2. Histogram of color difference frequency distribution of two different color management processes

3.2 Visual Effect Comparison Use two different color management processes to scan and output the original, compare the color difference between the output image and the original, and compare the image levels and color effects as shown in Fig. 3. Carefully observe the images output by the two different color management processes in Fig. 3, we can expect. Compared with the original, the main color of the image copied using the conventional color management process is basically the same, and the color in the highlights and shadows is darker; The image output by the improved color management process is closer to the original visual experience.

Fig. 3. Visual effect comparison of two processes (the middle is the original, the left is the output of process A, and the right is the output of process B)

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4 Conclusions This paper starts with UV digital inkjet printing to realize the process of copying decorative materials, discusses the important role of color management technology in the consistent reproduction of the surface color of decorative materials, and proposes an improved color management process plan, and from both visual effects and color difference data. It is demonstrated that the process scheme is superior to the traditional color management process for the consistency and reproduction of the surface color of the decorative materials. With the continuous improvement of people’s requirements for the color quality of color reproductions, in order to ensure the consistent reproduction of the surface colors of different decorative materials and improve product quality, the color management process introduced in the article is worthy of trial and application in the industry. Acknowledgments. This study is funded by Green Platemaking and Standardization laboratory for Flexographic Printing (ZBKT201904).

References 1. Wu, Z.: Wood Furniture Manufacturing Technology. China Forestry Publishing House (2005) 2. Singh, M., Haverinen, H.M., Dhagat, P., et al.: Inkjet printing-process and its application. Adv. Mater. 22(6), 673–685 (2010) 3. Wilhelm, H., Stahl, B.C., Armah, K., et al.: Test methods for the Long-term permanence behavior of photographs and fine art prints made with large-format flatbed printers using UV-curable pigment inks. Soc. Imaging Sci. Technol. 1, 84–85 (2014) 4. Sang, R., Wu, Z.: Application of UV inkjet printing technology in the surface decoration of furniture. Packag. Eng. 32(6), 29–32, 39 (2011) 5. Sang, R.: Development and prospects of 3D wood texture manufactured by UV inkjet printing. J. Forest. Eng. 5(6), 20–28 (2020) 6. Wang, F.: Research on Decorative Patterns of Furniture and Wood Products based on UV Digital Inkjet Printing Technology, Nanjing Forestry University (2017) 7. Tian, Q.: Printing Color Management. Cultural Development Press (2015) 8. Li, J.: Market scale and industry trend analysis of inkjet printing equipment industry. Chinese Packag. 1, 82–84 (2015) 9. Guan, Y., Gao, Y., Yuan, J.: Application of UV flat plate inkjet printing technology in packaging and printing field. Print Today 8, 52–54 (2015) 10. Wang, J., Li, Z., Ni, C.: Machine vision algorithms of online color recognition and classification for solid wood flooring products. J. Forest. Eng. https://doi.org/10.13360/j.issn.20961359.202012012 11. Long, L.: Wood floor surface decoration innovation progress. Res. Dev. 6, 50–53 (2020) 12. Liu, Y., Mou, X., Cheng, P.: Study on effect of device link profile in color management. In: Zhao, P., Ye, Z., Xu, M., Yang, L. (eds.) Advanced Graphic Communication, Printing and Packaging Technology. LNEE, vol. 600, pp. 113–119. Springer, Singapore (2020). https:// doi.org/10.1007/978-981-15-1864-5_16 13. Tian, Q.: Unconventional spot color reproduction decorative images. Print Mag. 04, 44–47 (2015)

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14. Liu, Y., Chung, R.: Quantifying reproducible brand colors in four-color printing. Packag. Eng. 17, 223–227 (2018) 15. Cheng, J., Zheng, L., Liu, Y.: Color Principle and Application. Culture Development Press 51

Mural Inpainting Method Based on Deep Convolutional Generative Adversarial Networks Wenqian Yu(B) , Zhibo Hu, Liqin Cao, and Zhijiang Li School of Printing and Packaging, Wuhan University, Wuhan, China [email protected]

Abstract. As an ancient art form, mural painting is very significant in terms of culture and history and the inpainting of murals is of great significance. The digital mural restoration takes a short time and is highly adaptable, which makes up for many shortcomings of manual restoration. In this paper, we introduced a DCGANbased mural restoration method using weight matrix in the loss function calculation to focus the attention of the network, and built a dataset of Tang Dynasty clothing murals. Based on the built dataset, the proposed method with weight matrix has achieved better results and performs well in terms of color and detail. Keywords: GAN · DCGAN · Mural restoration · Convolutional Neural Network

1 Introduction As an ancient and mysterious form of painting, murals have extremely high artistic value. However, due to natural and man-made reasons, many murals have been damaged or even destroyed. The traditional manual mural restoration process has many disadvantages such as high labor cost and difficult working environment. Digital image inpainting overcomes the above shortcomings and can save a lot of manpower and time resources. The existing digital image inpainting methods can be divided into two categories: traditional model-driven methods and deep learning methods. Traditional image inpainting methods usually establish a geometric model or use texture synthesis to complete restoration of the small damaged area. However, traditional methods can only extract the shallow features, leading to problems such as blurred content and lack of semantics. In contrast, deep learning methods can extract the deep semantic features of images through a large amount of data. The mainstream deep learning image inpainting model includes two categories: Auto Encoder (AE) and Generative Adversarial Networks (GANs). In 2016, Pathak et al. proposed Context-Encoder (CE) based on the structure of AE, which applied deep learning to the field of image inpainting for the first time [5]. In order to solve the problem of CE in resolution and consistency, in 2017, Chao et al. proposed a High-Resolution Image Inpainting method [9], which divides the network into two parts: content generator and texture generator. Aiming at the inpainting of irregular areas, Liu et al. proposed Partial Convolutions in 2018, which only convolves the effective pixels in the undamaged area and ignores the pixels in the missing area. Yu et al. [10] used Gated Convolutions to optimize Partial Convolutions, updating the masks through automatic © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 71–77, 2022. https://doi.org/10.1007/978-981-19-1673-1_13

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learning, which makes the inpainting process more flexible. But it costs a lot of time and computing resources. As the methods based on AE are not good enough in terms of performance and time cost, more researchers turn their attention to GAN models. In 2017, Yeh et al. [11] proposed an image inpainting method based on Deep Convolution Generative Adversarial Networks (DCGAN). Compared with CE, it does not need to use the corresponding mask during training, so it is more suitable for the inpainting of irregular damaged regions. However, DCGAN only performs well on data sets with simple structure and obvious features, such as face data sets, and the inpainting results of complex scenes are not ideal. For the restoration of complex scenes, in 2017 Iizuka et al. [1] proposed Globally and locally consistent image completion method (GL). Based on GL, Dolhansky et al. [2] introduced dilated convolution in the generator to turn the closed human eyes to the open state. In order to further expand the receptive field of the computer, Yu et al. [3] proposed the Coarse-to-fine model based on GL. Although the deep learning methods have been widely used in the field of image inpainting, there are still many problems to be solved due to the characteristics of murals. In terms of data, we lack datasets with clear and uniform mural images. Besides, it is common to use the structure of AE in mural inpainting, but the methods do not perform well in details and resolution. In order to solve the above problems, this paper constructs an image inpainting model based on DCGAN. The weight matrix is used in the loss function calculation to focus the attention of the network to improve the quality of the details of the image reconstruction. We also construct a dataset of Tang Dynasty clothing murals and use artificial masks to simulate the damaged regions. The remaining of this paper is organized as follows. Section 2 describes principles and the model of mural inpainting. Experimental results and analysis are shown in Sect. 3. Conclusions are given in Sect. 4.

2 Model of Mural Image Inpainting 2.1 DCGAN GAN was first proposed by Goodfellow et al. [4] in 2014, the central idea of which is from game theory. In the network, two models are trained at the same time: a generator and a discriminator. The generator and the discriminator form an adversarial relationship and both of them are continuously improved. The principle of GAN network is expressed by mathematical formula as follows:     (1) minmaxV (D, G) = Ex∼pdata (x) logD(x) + Ez∼pz (z) log(1 − D(G(z))) G

D

In 2016, Radford et al. first proposed DCGAN for unsupervised feature learning [6]. The overall architecture of the model is similar to GAN, and the generator and discriminator structures are based on CNN with some improvements. DCGAN uses convolutional layers instead of pooling layers, cancels the fully connected layer and uses batch normalization. The structure of the generator is shown in Fig. 1, and the discriminator is basically symmetrical.

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Fig. 1. Structure of the generator of DCGAN

2.2 Mural Image Inpainting Based on DCGAN In this paper, we firstly train DCGAN with intact and consistent mural images and the training process does not need masks. The model parameters are saved until it can generate mural images which are close to the real ones. By calculating a new loss function, the parameters of the generator are updated iteratively in the previous step, and then the repaired image will be generated. The overall process of image inpainting is shown in Fig. 2.

Fig. 2. Inpainting process

The loss function of image inpainting consists of two parts: prior loss Lossp and context loss Lossc . The aim of the prior loss is to make the results as close to the real mural images as possible. The calculation formula is as follows: Lossp = ln(1 − D(G(z)))

(2)

Among them, z is the input 100-dimensional noise vector, D is the discriminator, G is the generator, and G(z) is the generated image. The context loss aims to bring the result closer to the damaged image, rather than generating an image which is close to the real data but has nothing to do with the original damaged image. Its formula is as follows: Lossc = ||W  (G(z) − y)||

(3)

W is a weight matrix with the same size as the input image, and y represents the damaged image. To achieve more detail texture, the weight matrix W is calculated from the mask image M in our work. For the damaged area, the difference between the

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generated image and the damaged image is not included in the loss function, that is, the weight is 0. For the pixels close to the damaged area, we take a 3 * 3 window with the pixel as the center. If there are more damaged pixels in the window, the weight value will be greater. Except for damaged pixels, all pixels with a weight value lower than 0.1 are assigned a weight value of 0.1. The calculation formula is as (4):  i+1 j+1  p=i−1 q=j−1 1 − Mij weightij = 9 ⎧ , if Mij = 0 ⎨0 Wij = weightij , if Mij = 0 and weightij > 0.1 (4) ⎩ 0.1 , if Mij = 0 and weightij > 0.1 Where, Mij is the pixel value of the mask at row i and column j. If the pixel is a damaged one, then Mij equals to 0, otherwise it is 1. The purpose of the weight matrix is to focus the attention of the network on the damaged area.

3 Experiments and Analysis 3.1 Datasets For DCGAN-based image inpainting method, the model uses the complete mural image for training, and no mask is required in the training set. Since DCGAN is only suitable for data sets with obvious features, we chose the clothing murals from the Tang Dynasty when constructing the train set. After selection, the images are overlapped and cropped into 64 * 64 blocks, because the input of DCGAN must be the same size. Finally, 9299 images are obtained. The number of images in the test set is 950, accounting for 10.2% of the training set. For the test set, masks are necessary to simulate the damaged part of the murals. 3.2 Evaluation Methods In this paper, Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity (SSIM) are taken as the objective evaluation criteria [7, 8]. 3.3 Inpainting Results and Analysis Part of inpainting results is shown in Fig. 3. From the subjective view, the model performs well in terms of color tone, resolution and consistency. For details, there is no large-area blurring that affects the visual experience. In terms of tone, the color of inpainting images is close to the original ones. For consistency, the inpainting part can be well integrated with other surrounding pixels. It can be seen from the results that DCGAN successfully completed the inpainting task and in terms of tone and details. In addition to subjective evaluation, we also use the objective methods to evaluate the inpainting results. PSNR and SSIM values are calculated for the example images and the test set, which are shown in Table 1 and Table 2. The PSNR value of all images

Mural Inpainting Method

1

2

3

4

5

6

(a) Origin imges

(b) Damaged images

(c) Results with weight matrix

(d) Results without weight matrix

Fig. 3. Inpainting results of DCGAN Table 1. Objective evaluation of the example images Number

PSNR

SSIM

1

36.9902

0.9666

2

34.1481

0.9682

3

32.0755

0.9771

4

30.4908

0.9751

5

31.1020

0.9506

6

33.8676

0.9732

75

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Average of PSNR

Average of SSIM

950/10.2%

30.4144

0.9637

is greater than 30, and the SSIM value is greater than 0.95. The results illustrate that the restored images and the real results are close in color and the texture. During the inpainting process, the weight matrix is utilized in the process of calculating the context loss, the purpose of which is to focus the attention of network. The comparison of the results with and without weight matrix are shown in Fig. 3. From subjective view, the details of the result with the weight matrix are clearer and the overall is smoother. The comparison of objective evaluation is shown in Table 3 and Table 4. The PSNR and SSIM values of results with weight matrix are greater for example images and the test set. Table 3. Contrast of results with and without weight matrix in objective view (example images) Number

PSNR (without matrix)

PSNR (with matrix)

SSIM (without matrix)

SSIM (with matrix)

1

33.5369

36.9902

0.9397

0.9666

2

32.0923

34.1481

0.9537

0.9682

3

30.1967

32.0755

0.9636

0.9771

4

29.0764

30.4908

0.9673

0.9751

5

28.8604

31.1020

0.9233

0.9506

6

30.7479

33.8676

0.9492

0.9732

Table 4. Contrast of results with and without weight matrix in objective view (the test set) Number of images /Percentage

Number of images

PSNR (without matrix)

PSNR (with matrix)

SSIM (without matrix)

SSIM (with matrix)

950/10.2%

950

28.9608

30.4144

0.9505

0.9637

4 Conclusions In this paper, we built a clear collection of Tang Dynasty costume murals with similar styles. In addition, masks were used to simulated the damaged area of murals and the

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test set was established. In terms of inpainting model, unsupervised DCGAN was used to complete the training task. The loss function includes a prior loss and the context loss, and the weight matrix was utilized in the context loss to focus the attention of the network. The results showed that the restoration results obtained by using the weight matrix method had good performance in both visual results and quantitative evaluation. In the future, we will consider to enhance the versatility of the network, because DCGAN is not suitable for the complex scene. In addition, the input size of the network can be further considered and we can try the input of any size. Also, the real damaged mural images should be tried if the proposed method will be applied to actual scene. Acknowledgements. This work was supported by Fundamental Research Funds for National Key Research and Development Program of China, Grant/Award Numbers: 2020YFC1522703; National Natural Science Foundation of China, Grant/Award Number: 41671441.

References 1. Iizuka, S., Simo-Serra, E., Ishikawa, H.: Globally and locally consistent image completion. ACM Trans. Graph. 36(4), 1–14 (2017). https://doi.org/10.1145/3072959.3073659 2. Brian, D., Ferrer, C.-C.: Eye In-Painting with Exemplar Generative Adversarial Networks. In: 2018 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pp. 7902– 7911 (2018) 3. Yu, J., Lin, Z., Yang, J., et al.: Generative Image Inpainting with Contextual Attention, pp. 5505–5514 (2018) 4. Goodfellow, I., Jean, P.-A., Mehdi, M., et al.: Generative adversarial networks. Commun. ACM 63(11), 139–144 (2020) 5. Deepak, P., Krahenbuhl, P., Donahue, J., et al.: Context encoders: feature learning by inpainting. In: 2016 IEEE Conference on Computer Vision and Pattern Recognition (CVPR), pp. 2536–2544 (2016) 6. Alec, R., Metz, L., Chintala, S.: Unsupervised representation learning with deep convolutional generative adversarial networks. arXiv e-prints, 1511–6434 (2015) 7. Horé A., Ziou, D.: Image Quality Metrics: PSNR vs. SSIM. pp. 2366–2369 (2010) 8. Al-Najjar, Y.: Comparison of Image Quality Assessment: PSNR, HVS, SSIM, UIQI. Int. J. Sci. Eng. Res. 3 (2012) 9. Yang, C., Lu, X., Lin, Z., et al.: High-Resolution Image Inpainting Using Multi-scale Neural Patch Synthesis, pp. 4076–4084 (2017) 10. Jiahui, Y., Lin, Z., Yang, J., et al.: Free-form image inpainting with gated convolution.In: 2019 IEEE/CVF International Conference On Computer Vision (ICCV 2019), pp. 4470–4479 (2019) 11. Raymond-A, Y., Chen, C., Teck-Yian, L., et al.: Semantic image inpainting with deep generative models. In: 30th IEEE Conference on Computer Vision and Pattern Recognition (CVPR 2017), pp. 6882–6890 (2017)

Pencil Sketch Generation Based on Stroke Density and Texture Debiao Yang(B) and Aibin Huang School of Media and Design, Hangzhou Dianzi University, Zhejiang, China [email protected]

Abstract. It was funny and essential that an image was converted to sketch style in computer graphics fields. Sketch style contains the structural information of the image because of its simple outline and shadow. It has always been the hot topic of image processing and computer graphics with significant research value. Contour, texture, and shadow are important features for a sketch. This paper suggested a method that an image can be converted to sketch style. Firstly, the convex hull of RGB color space and its geometric centre of gravity is calculated to construct the mesh and ray. Secondly, the mesh and ray intersection is calculated to estimate the stroke density, and post-processing is carried out. Instead of the dark layer tone mapping in the histogram matching, the texture tone map is generated by matching with other tones. Finally, it is combined with a stroke line to achieve a more hierarchical texture shadow effect. The result shows that it’s an effective method to show a more realistic pencil sketch structure. Keywords: Pencil sketch · Texture · Stroke density

1 Introduction Non-photorealistic rendering (NPR) has great research value to simulate the artistic effects in the computer. Pencil sketch aims to simulate the characteristics of artists’ sketch to transform the style of images, including pencil line, shadow drawing, and texture [1]. In recent years, some methods have been proposed for the conversion of sketch style. With the rise of deep learning, many neural network methods have been proposed to achieve style transfer. MSG-NET [2] proposes an Inspiration layer to match the characteristic statistical information (Gram matrix) of style pictures and retain the content of origin images. Xiang et al. [3] propose open-domain sampling and optimization strategies to confuse the generator, using edge instead of sketch to convert sketch into photos, and extended it to Anime2Sketch to implement sketch style. Cewu Lu et al. [4] proposed a traditional pencil drawing generation method divided into two steps, line generation and texture matching. This method is based on the artist’s painting order, like drawing image contour, global light shadow and local structure shadow. However, when this method is used to transform the illustration, the tone part will be consistent with the original image, leading to some details in the background being blurred or © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 78–85, 2022. https://doi.org/10.1007/978-981-19-1673-1_14

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removed. This paper proposes an algorithm that uses the stroke density adapting to the image structure to reflect the hue texture of the image. The method is as followed, the histogram matching method is used for the bright and mild layers, and the stroke density method is used for the dark layers. After post-processing, the new texture map is obtained and combined with the original stroke line to get the sketch effect map. The results show that the shadow structure of the image is reflected by this method.

2 Our Approach The proposed method in this paper consists of two parts: stroke line & tone mapping generation and stroke density generation. The stroke line aims to express image contour features in sketch, while tone matching focuses on the performance of shapes and shading, and stroke density is used to perform shadow [5]. The framework is illustrated in Fig. 1.

Fig. 1. Overview of the proposed framework

2.1 Line Extraction and Tone Mapping Firstly, the original input illustration is transformed into grayscale image, and the gradient of the image is calculated to extract the image boundary. Generally, the gradient image is sensitive to noise, and the generated edge is long and continuous, which is not consistent with the characteristics of sketch lines [6]. Thus, the maximum response map in the line direction is calculated to generate short lines as Gi = G ⊗ Li , Li = {0◦ , · · · , 315◦ }, i = {0, · · · , 7}

(1)

where ⊗ is convolution operator, Li is a line segment that is convoluted with gradient image G to obtain the response map Gi in the i-th direction. Then the maximum value

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of every pixel in each response map is selected to get the maximum response set Mi . It is expressed as  Gi (n) if arg max{Gi (n)} = i Mi (n) = (2) 0 other Then, according to the maximum response map M i , short lines in each direction can be obtained and connected by Eq. 3. It is shown in Fig. 2. 8 (Mi ⊗ Li ) (3) S= n=1

where Mi is the maximum response set, Li is a line segment, ⊗ is convolution operator, S is the final pencil stroke map. The final result is required to invert the pixel values and map them into [0, 1] to express the effect of white paper and black lines.

Fig. 2. Stroke lines in each direction. Eight directions are computed to get response map

Secondly, histogram matching is used in tone mapping. Different from the original input image, histogram of sketch usually follows certain patterns. Laplacian distribution is used for bright regions to model the tone distribution with its peak because pixels concentrate at the peak, and the number decreases sharply. It is defined as  1−v 1 − σb e if v ≤ 1 σ b (4) h1 (v) = 0 other where v is tone value, σb is the scale of the distribution. Artists usually express depth and details with different pressure of many strokes in the mild layer. Thus, uniform distribution is used to enrich pencil drawing. It is expressed as  1 if ua ≤ v ≤ ub (5) h2 (v) = ub −ua 0 other where ua and ub are two controlling parameters defining the range of the distribution. Tone map H can be obtained by combining histogram distribution with weights. It is represented as 1 2 H= ωi hi (v) (6) i=1 N where N is the normalization factor, ωi is the weights of each layer, hi is the histogram of each distribution.

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2.2 Stroke Density Two strokes will produce a translucent superimposed fusion effect after using two different color brushes to color. The blending of different stroke colors can be defined as the following c=

n 

αi ci s.t.

i=1

n 

αi = 1 αi > 0

(7)

i=1

where n is the number of colors participating in the blending, ci is stroke colors, ai is blending weights, c is the generated final color. The total number of strokes involved in color blending is called Stroke Density; the higher value of stroke density on canvas means more different color strokes pass through the pixel in the whole painting procedure. It can be regarded as many times stroke drawing with different pressure for pencil sketch. And the stroke density value of n different colors is defined as  n 2 1− i=1 αi (8) k= 1 − √1n where k is the stroke density, n is the number of different colors. It is necessary to estimate the stroke density. Zhang et al. [7] calculated the RGB convex hull of the image as a palette to estimate the stroke density. The palette based on convex hull has dense and continuous geometric meshes. Therefore, RGB convex hull of observed pixel colors are computed with quick hull algorithm [8] to get the mesh-like palette M = D3 ({ci |i = 1, . . . , W × H })

(9)

where D3 is the function to compute 3D convex hull, W × H is the total number of image pixels, ci is observed pixel colors, M is mesh of convex hull. Convex hull is considered a set of colors, so the surface color of the convex hull can be regarded as palette. The possible color combinations of each color can be deduced after getting the palette, and stroke density is computed according to blending weights of each combination. Firstly, the color {c1 , · · · , cn } of n different sampling points are selected in palette, and the barycentre g of all random sampling points can be calculated as 1 ci n n

g=

(10)

i=1

Secondly, for color of each pixel position cp , a ray is casted from g to cp and will intersect with the surface of the palette at a hitpoint hp , at this time, {cp, g, hp} are collinear, the illustration of color space is shown as Fig. 3, then color of pixel position cp can be represented as     n  cp − hp  1  cp − hp   h +  c (11) cp = 1−  g − hp  p n g − hp  i i=1

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where |·| is the Euclidean distance. Finally, stroke density can be computed according to the blending weights of pixel colors with Eq. 8. It is written as

 n  |cp −hp | 2  |cp −hp | 2 1− 1− |g−h + |g−hp |n p| i=1 kp = (12) 1 1 − √n+1 where k p is the stroke density at the point. It can be seen that the calculation is more accurate with more sampling points. When n → + ∞, the final stroke density K can be expressed as   cp − hp    (13) K= g − hp  The algorithm is content-aware. Thus stroke density can adapt to image structures.

Fig. 3. Visualization of color space. The color point, barycentre and hitpoint are collinear

2.3 Post-processing and Sketch Generation Retinex algorithm enhances the stroke density map to filter the pixels of the bright and mild layer. Like the stroke density, sketch texture is also achieved using texture map P to draw for β times, as Fig. 4 shows.

Fig. 4. Tonal pattern. P is hand-drawn map, β is times of mapping.

T = Pβ

(14)

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Line stroke map S, tone map T and stroke density map K are combined to generate the final result by the following formula as R=S ·T ·K

(15)

3 Result and Comparison The results show that it retains the lines and textures of original illustrations and enhances the background details by the proposed method in Fig. 5. Cewu et al. method reflects the line and texture features of the sketch style, but the structure and information of the background are not obvious. Anime2Sketch also uses thin and light lines to reflect the features of the artist’s hand-drawn, but this method pays more attention to the sketch line, details of the background and tone is reduced. Multi-Style-Transfer (MST) uses the styletransfer method to retain a large amount of original image information. But the texture is similar to the style image, which cannot fully reflect the hand-drawn characteristics. The shadow intensity of region where pixel values vary greatly is enhanced with our method. The background hierarchy is complete and has short and straight lines to perform the feature of the pencil sketch, which has good feasibility and practicability.

Fig. 5. Experimental results. (a) is original illustrations, (b) is Cewu et al. [3] results, (c) is proposed results, (d) is Anime2Sketch results, (e) is the result of multi-style-transfer method.

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Fig. 6. Quantitative experiments. ω1 is bright layer weight, ω2 is mild layer weight, K is the stroke density weight.

We also implement quantitative experiments to evaluate the experimental results by changing different weights. It can be seen from Fig. 6 that the transformation efficiency gradually increases as the bright layer decreases, and the background details become richer as the mild layer increases. The image structure is more obvious with the increase in stroke density, but some information is also covered. We find that setting K = 1 produces a better result in practice.

4 Conclusions This paper proposes the transformation from illustration to pencil sketch, which retains the advantages of global lines and textures in the original illustration and enhances the details of background and tone. The experimental results hint that the proposed method can enhance the details and structure of the local shadow of the image.

Statement of Ethical Approval. I certify that this manuscript is original and has not been published and will not be submitted elsewhere for publication while being considered by Debiao Yang. And the study is not split up into several parts to increase the quantity of submissions and submitted to various journals or to one journal over time. No data have been fabricated or manipulated (including images) to support your conclusions. No data, text, or theories by others are presented as if they were our own. The images were entitled to be applied in the manuscript. The submission has been received explicitly from all co-authors. And authors whose names appear on the submission have contributed sufficiently to the scientific work and therefore share collective responsibility and accountability for the results. Conflict of Interest. The authors declare that they have no conflict of interest. This article does not contain any studies with human participants or animals performed by any of the authors. Informed consent was obtained from all individual participants included in the study.

References 1. Qian, W., Cao, J., Xu, D., Wu, H.: Research status and Prospect of non- photorealistic rendering technology. J. Image Graph. (7), 1283–1295 (2020)

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2. Zhang, H., Dana, K.: Multi-style generative network for real-time transfer. arXiv preprint arXiv:1703.06953 (2017) 3. Xiang, X., Liu, D., Yang, X., Zhu, Y., Shen, X., Allebach, J.P.: Adversarial open domain adaption for sketch-to-photo synthesis.: arXiv preprint arXiv:2104.05703 (2021) 4. Lu, C., Xu, L., Jia, J.: Combining sketch and tone for pencil drawing production. In: Proceedings of the Symposium on Non-Photorealistic Animation and Rendering (NPAR 2012), pp. 65–73. Eurographics Association, Goslar, DEU (2012) 5. Cabral, B., Leedom, C.: Imaging vector field using line integral convolution. In: Proceedings of the ACM SIGGRAPH Conference, pp. 263–270 (1993) 6. Kang, H., Lee, S., Chui, C.K.: Coherent line drawing. In: Proceedings of the 5th International Symposium on Non-Photorealistic Animation and Rendering (NPAR 2007), pp. 43–50 (2007) 7. Zhang, L., Simo-Serra, E., Ji, Y., Liu, C.: Generating digital painting lighting effects via RGB-space geometry. ACM Trans. Graph. 39(2), Article no. 13, 13 p. (2020) 8. Tan, J., Lien, J.-M., Gingold, Y.: Decomposing images into layers via RGB-space geometry. ACM Trans. Graph., 14 p. (2016)

Analysis and Optimization of the Point Cloud Accuracy of the 3D Laser Scanner Based on the Surface Characteristics of the Object Yaoshun Yue and Maohai Lin(B) Key Laboratory of Green Printing and Packaging Materials and Technology in Universities of Shandong, School of Light Industry Science and Engineering, Qilu University of Technology), Qilu University of Technology (Shandong Academy of Sciences), Jinan, China [email protected]

Abstract. As a high-precision, high-efficiency, non-contact target scanning technology, 3D laser scanning breaks the barriers of two-dimensional points and surfaces and is a key technology in 3D printing. However, in its application process, due to the influence of the scanning system of 3D laser scanner and the surface characteristics of the scanned object, the scanning effect of 3D laser scanner is difficult to completely reproduce the real data of the scanned object. According to the above problems, based on the surface characteristics of objects, this paper designs experiments studies the influence of different surface characteristics on the scanning effect of 3D laser scanner, and analyzes the reasons of the influence. At the same time, through experimental analysis, it is innovatively proposed that the scanning effect can be optimized and controlled by spraying powder for objects with absolutely smooth surfaces, and that the scanning effect can be optimized and controlled by adjusting the brightness of the scanning light source for objects with different surfaces. The paper designs relevant experiments to verify the feasibility of the method and to proves that the method can greatly improve the scanning efficiency of 3D laser scanner. Keywords: 3D reconstruction · 3D laser scanner · Accuracy analysis control · Point cloud data

1 Introduction The 3D laser scanning system is also called 3D real scene copy system The instrument obtains the point cloud data of the three-dimensional object in a non-contact mode through the high-speed flash laser, and then reproduces the point cloud model information of the scanned object on the computer. It breaks the barriers of two-dimensional points and surfaces, and has been successfully applied to high-tech fields such as three-dimensional modeling and 3D printing [1]. In the actual application process of the 3D laser scanner, the scanning effect of the 3D laser scanner often deviates from the actual object value due to errors caused by the 3D scanner’s own system, the characteristics of the surface of the object being scanned, © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 86–92, 2022. https://doi.org/10.1007/978-981-19-1673-1_15

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external ambient light and other factors. Therefore, the point cloud data accuracy analysis and error optimization control of its 3D laser scanner have become a very important step in the measurement process [2]. The article mainly focuses on the characteristics of the surface of the scanned object to study the point cloud data accuracy of the 3D laser scanner and further propose optimization and processing methods.

2 ReeyeeProX2 3D Laser Scanner The forensic and verification work in this article is based on the ReeyeeProX2 threedimensional laser scanner as shown in Fig. 1. Its working principle belongs to the structured light method, as shown in Fig. 2 [3]. The laser irradiates the surface of the object through specular reflection and diffuse reflection on the surface of the object, and then forms an image on the CCD photosensitive receiver and converts it into digital information. Finally, it passes through the three-sided geometry of a geometric triangle. The relationship calculates the three-dimensional information it carries, and finally the three-dimensional information of the object is aggregated by integrating the point cloud data, and then processed and optimized by the software system, and then packaged into a three-dimensional quantitative model [4].

Fig. 1. ReeyeeProX2 3D laser scanner

Fig. 2. Structure principle

3 Error Analysis of Point Cloud Data of 3D Laser Scanner According to the error source analysis, the scanning error of 3D laser scanner is mainly composed of systematic error caused by the optical system of the instrument itself, accident error caused by the operation process and controllable error caused by the scanning environment light. The optical system error of the instrument itself is very small and uncontrollable, and the accidental error and scanning ring light can be manually controlled or eliminated, therefore, this article mainly focuses on the characteristics of the surface of the scanned object to study the point cloud data accuracy of the 3D laser scanner and further propose optimization and processing methods [5]. 3.1 Surface Roughness of Scanned Object The acquisition of three-dimensional data of the scanned object is affected by the reflected light data acquired by the CCD, and the reflected light data comes from diffuse reflection. For the reflective surface of the scanned object, the higher the smoothness of

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the reflective surface, the more diffuse the less the data of the reflected light, the more unstable the data obtained by the scanned object. Intuitively speaking, it will cause the loss of the scanned data on the smoother reflective surface of the scanned object. However, as a comparison, it is not right that the rougher the reflective surface of the scanned object, the better. When the reflective surface of the scanned object is very rough, the laser spot will be deformed. Intuitively, the scanning result will be quite different from the actual data of the object [6]. 3.2 Surface Color of the Scanned Object Different colors will selectively absorb laser light and reflect other light. Therefore, when the color of the reflective surface of the scanned object is special, it will also affect the scanned data. For example, if part of the color of the scanned object is completely black, it will cause the effect of fully absorbing the irradiated laser, making it difficult for the CCD photoreceptor to receive the data reflected by the black color surface, resulting in the loss of the scanned image of the object.

4 Analysis Experiment and Optimization Control Mode 4.1 System Error Stability The instrument used in this experiment is: ReeyeeProX2 three-dimensional laser scanner. Before the object surface specific point cloud data analysis experiment, due to the uncontrollable system error, this experiment will explore the stability of the point cloud data accuracy of the instrument. In this experiment, the standard test block is a 15 * 15 * 15 cm yellow cube. Use a three-dimensional laser scanner to scan the standard test block three times, record the point cloud data obtained during each scanning process, and measure the data of the generated three-dimensional package model. The scan data is shown in Table 1. Table 1. Standard test block scan data

Scanning effect

Packaging model

D

Volume (cm3)

V

14.94

0.06

3374.87

0.13

215783

15.11

0.11

3374.89c

0.11

215237

15.09

0.01

3375.01c

0.01

Point cloud

Side length (cm)

214967

a

b

c

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From the data shown in Table 1, it can be seen that the measured side lengths of the standard test block three scan results are not more than 0.20 cm from the standard value, and the volume of the scanned standard test block also has a small difference from the standard value. It is inferred that the 3D laser scanner used in this experimentReeyeeProX2, has high scanning performance and good stability. 4.2 Analysis and Optimization Control of Point Cloud Data by Roughness and Smoothness This experiment chooses a piece of paper with a glass cover in A4 format as the absolutely smooth test object called ‘a’, and a piece of coated paper as the smoother test object called ‘b’ and one Lead drawing paper is a rougher experimental object called ‘c’. In order to eliminate the influence of other printing on the experiment, the color of the experimental object is controlled to be white, the scanning ambient light is controlled to indoor no light, and the scanning brightness is controlled at the lowest brightness. The scanning time is fixed at 10s, and the point cloud data of the 3D laser scanner is recorded. The experimental data is shown in Table 2. Table 2. Experimental data of different rough papers

Object

a

b

c

Scanning effect

Point cloud model

Time 10s

10s

10s

Ranging

Number of point clouds

40cm

48494

40cm

71334

40cm

71497

According to the above analysis of Table 2, it can be seen that when the roughness of the object is not much different, it has little effect on the scanning effect of the 3D laser scanner and the amount of point cloud data. However, when the surface roughness and smoothness of the object approaches to absolute smoothness, the less the data of the diffuse reflection light on the reflective surface, the point cloud data acquired by the scanned object will be unstable or some piece of data will be lost [7]. In order to further study the influence of the absolute smoothness of the surface of the object on the point cloud data of the 3D laser scanner and the control and optimization methods, this experiment uses a glass water cup as the object of absolute smoothness,

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and controls the scanning ambient light to indoor no light, and the scanning brightness is controlled at the lowest. The number of marking points is randomly distributed. The scanning result is shown in Table 3-a. The main reason for this phenomenon is that the specific surface of the glass cup tends to be absolutely smooth. When the laser of the 3D laser scanner irradiates its surface, it is more likely to have specular reflection, and the relative proportion of diffuse reflection will be reduced, so that the relative proportion of useful diffuse reflection information received by CCD photoreceptors on the surface of objects will also be reduced. According to the above reasons and based on the principle that 3D laser scanner is monochromatic imaging technology, this paper proposes that the proportion of diffuse reflection can be increased by changing the surface smoothness of absolutely smooth objects, so as to scan 3D data on the surface of absolutely smooth objects and optimize their point cloud data. In this experiment, the surface of an absolutely smooth object is treated by powder spraying, as shown in Table 3-b. Table 3. Scanning renderings of untreated and treated glass cups

Object

Scanning effect

Point cloud model

Side length (cm)

a

26.3cm

b

26.4cm

Number

1427

97456

According to the comparison of the above experimental results, it can be concluded that: the different roughness and smoothness of the surface of the scanned object have different reflection characteristics to the laser. In practical application, the surface of the object must be rougher, and the shorter the time to complete the entire scanning process, and the better the scanning effect. In order to control and optimize the specular reflection effect on the surface of the absolutely smooth object, which results in the poor scanning effect, the surface of the absolutely smooth object can be sprayed and painted to change the surface roughness of the absolutely smooth object. 4.3 Analysis and Optimization Control of Surface Color This experiment chose to use color blocks with different colors to be pasted on the same A4 paper as the experimental object. To ensure that other factors remain unchanged, the scanning ambient light is controlled as indoors. Light, the scanning brightness is controlled to the lowest, the scanning time is controlled to 10s, and the number of marking points is randomly distributed.

Analysis and Optimization of the Point Cloud Accuracy

Fig. 3. Object (six color)

Fig. 4. Effect (7s)

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Fig. 5. Effect (45s)

The scanning object and scanning effect are shown in Fig. 3, 4 and 5. Observing the scanning process and the scanning effect diagram, it can be clearly observed that the imaging speed of the yellow block is the fastest, and the imaging speed of the black block is the slowest, and the imaging has not been completed after finishing scanning. The main reason for this phenomenon is that the black block has strong light absorption capacity and weak reflection effect, so the useful light signal that can be received by the CCD photoreceptor of the three-dimensional laser scanner will be reduced. Based on the contrast light effect between the external ambient light and the scanner’s own measurement light, this article proposes to increase the scanning brightness of the 3D laser scanner to increase the brightness of the black block itself, so as to achieve the increase of 3D scanning effect. In order to truly reproduce the actual 3D scanning environment, the subjects choose irregular objects with black and other colors. The experimental design is: measure the same black block when the scanning brightness is 30%, 60%, and 90%, and record the time required for the completion of the scan. The scanning data are shown in Table 4. Table 4. ScaPoint cloud scan data of different measuring lights Measuring light

measure time(s)

Number of points

30%

256s

9315

60%

240s

45148

90%

65S

74257

Object

Scanning effect

Point cloud model

According to the above experimental data, it can be clearly observed that when the scanning light source is very low, the 3D laser scanner can only scan the light color of the surface of the experimental object. With the increase of the scanning light source of 3D laser scanner, the dark area on the surface of the scanned object can be scanned

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gradually, and the scanning effect is getting better. The number of point clouds that can be scanned also increases gradually, and the scanning time starts to shorten with the increase of scanning light source. Therefore, it can be concluded that by improving the scanning brightness of the 3D laser scanner, the 3D laser scanning effect and efficiency of dark objects can be improved.

5 Conclusions Firstly, this paper classifies the possible errors in the working process of 3D laser scanner, and analyzes the possible causes. Furthermore, based on the surface characteristics of the object, that is, mainly aiming at the surface roughness and color of the object, the paper studies the influence on the point cloud accuracy of the 3D laser scanner and the error analysis. Then, through designing experiments to simulate the influence in actual operation, aiming at different surface characteristics, this paper puts forward methods such as spraying powder, painting color or changing the brightness of scanning light source to further optimize the scanning effect and the quality accuracy of point cloud data, and designs related experiments to verify the feasibility of the methods proposed in this paper, which optimizes the scanning quality effect to a certain extent and increases the scanning efficiency of 3D laser scanner.

References 1. Liu, C., Zhang, Y.L., Wu, H.: Calibration and accuracy evaluation of terrestrial 3D laser scanner. Eng. Invest. 37(11), 56–60 (2009) 2. Pu, S., Voss, E.G.: Knowledge based reconstruction of building models from terrestrial laser scanning data. J. Photogram. Remote Sens. 64(6), 575–584 (2009) 3. Hu, Q.: Three-dimensional laser scanner and its measurement error influencing factors. Archit. Eng. Technol. Des. (4) (2017) 4. Lichti, D.: Terrestrial laser scanner self-calibration: correlation sources and their mitigation. J. Photogram. Remote Sens. 65(1), 93–102 (2010) 5. Peng, Y., Wang, Z., Cui L., et al.: Scanning method optimization of handheld 3D laser scanner. Cryog. Build. Technol. (2), 1–4 (2016) 6. Gao, W.: Accuracy analysis and evaluation of ground laser point cloud measurement. Beijing University of Civil Engineering and Architecture (2016) 7. Tian, L.: Research on Evaluation Method of Measurement Accuracy of Hand-Held Laser Scanner. Wuhan University, Wuhan (2020)

Medical Image Denoising Method Based on Total Variational Model and Adaptive Wavelet Threshold Saqing Wang(B) , Aibin Huang, Mengmeng Zhang, and Caifeng Liu School of Media and Design, Hangzhou Dianzi University, Zhejiang, China [email protected]

Abstract. Wavelet threshold denoising can easily cause edge blur, while total variational denoising is insufficient to achieve image smooth area denoising. Therefore, this paper proposes a new denoising method combining the total variational model and the adaptive wavelet threshold. Firstly, the original noisy image is processed by the total variational model, the improved Prewitt operator is used to extract the edge of the processed image, and the edge denoising image is obtained. Then, the original noisy image is divided into edge and non-edge images by the improved Prewitt operator, and the non-edge image is de-noised by the adaptive wavelet threshold method to obtain the non-edge denoising image. Finally, after denoising, the edge image and non-edge image are superimposed to achieve high-definition restoration of medical images. Experimental results show that the proposed method can effectively denoise medical images and preserve the original edges and details in the images. Keywords: Image denoising · Total variational model · Prewitt operator · Wavelet transform

1 Introduction Many kinds of noise often accompany medical images due to imaging instruments, external interference and other factors in the imaging process. Images with noise will affect doctors’ diagnosis of the disease. To remove the noise in medical images, scholars have done extensive research. Traditional image denoising is divided into spatial domain denoising and transformation domain denoising [1]. Spatial domain denoising methods are intuitive and easy to operate, but such methods easily cause the loss of image details. To retain the image details in denoising, Rudin, Oster and Fatemi [2] proposed a total variation image restoration model, which can protect the image edges and remove noise, but is susceptible to noise and produces a ladder effect. Denoising in the transform domain mainly separates useful signals from interference signals through Fourier transform, wavelet transform [3]. The wavelet threshold denoising method can remove part of the image noise, and the effect is very good. However, © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 93–98, 2022. https://doi.org/10.1007/978-981-19-1673-1_16

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the threshold function and the threshold selection method make it easy to cause image distortion and blurred edges. With the enhancement of GPU computing power, scholars have widely used and studied image denoising methods based on deep learning. For example, Chen uses the CNN network for low-dose CT image denoising [4]. To reduce noise and retain more edge details, Won proposed to use Octave convolution to simultaneously extract the high frequency and low-frequency features of images [5]. Although the denoising method based on deep learning is significantly better than the traditional image denoising method, it has higher requirements on computer hardware and takes a long time to run. A medical image denoising method was proposed based on the total variational (TV) model and adaptive wavelet threshold to solve these problems. The method utilizes the edge retention of total variational denoising and the sufficiency of wavelet denoising. The two denoising models are combined with the Prewitt operator respectively to obtain the final denoising effect.

2 Method of Medical Image Denoising 2.1 Image Edge Detection Based on Improved Prewitt Operator The traditional Prewitt edge detection operator is a first-order differential operator, which realizes the effective detection of edge contour information in the image through the horizontal (0°) and vertical (90°) directions of the template [6]. However, for medical images, the information of the edge is essential. If only the horizontal and vertical directions of the edge detection, it is easy to cause the loss of the edge. Therefore, this paper increases the traditional Prewitt operator template from the original horizontal and vertical directions to eight directions: 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315°, to make up for the shortcomings of the traditional Prewitt operator and make the edge structure more complete. The improved directional template is shown in Fig. 1.

Fig. 1. Improved directional template

Multidirectional Prewitt operator is used for edge detection of medical images, and the results of each edge detection are organically fused by the method of equal weight addition, to obtain the final edge detection results.

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2.2 Total Variational Denoising The total variational denoising model is a method to establish the corresponding energy functional from the whole image. In practical application, since the total variation of the noise-containing image is much larger than that of the noise-free image, image denoising can be achieved by minimizing the global variation. The total variational model defines the minimum energy functional form as    λ |f − f0 |dxdy (1) |∇f |2 dxdy + min TV (f ) = 2   The formula is divided into two terms. The regular term can suppress noise in the optimization process, and the fidelity term is used to maintain the similarity between the de-noised image and the original image. In the formula, f0 represents the image with noise, F represents the image without noise, λ is the relaxation factor that adjusts the proportion of the fidelity term and gradient, and ω represents the whole image area. The Euler-Lagrange equation derived from Eq. (1) is −∇ · (

∇f ) + λ(f − f0 ) = 0 |∇f |

(2)

According to the gradient descent method, the TV smoothing model is ∂u ∇f =∇ ·( )−λ(f − f0 ) ∂t |∇f |

(3)

2.3 Adaptive Wavelet Threshold Denoising Wavelet threshold denoising in image signals is mainly divided into three steps: wavelet decomposition of two-dimensional signals, threshold quantization of high frequency coefficients and two-dimensional wavelet reconstruction [7]. Adaptive wavelet threshold is adopted in this paper, and the formula of noise threshold is as follows: √ ∂ 2 ln N (4) λ= j Where α is the standard noise error, N is the image scale, and j is the decomposition scale. The threshold selection method realizes different processing for different decomposition layers through the newly added decomposition scale J, making the threshold formula conform that the proportional distribution of signal and noise at different decomposition layers is different after wavelet decomposition. In the actual environment, it is impossible to know the standard noise variance of the image, so the estimation method should be used to determine the standard noise variance when selecting the value. In this paper, a simple and effective threshold estimation method is adopted: in the first stage of orthogonal wavelet decomposition of images, the HH part of the wavelet coefficient is taken as the estimation value with its standard variance.

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2.4 Denoising Process of TV and Adaptive Wavelet Threshold TV denoising model can preserve the edge of the image and remove noise. Taking of this advantage, our method firstly uses the TV model to de-noise the image, and then uses the Prewitt operator extended to 8 directions to extract the edge of the de-noised image, to extract the edge information of the image while removing the noise as much as possible. Then, the original noisy image is divided into edge and non-edge images by the extended Prewitt operator. The non-edge image is de-noised by the adaptive wavelet threshold method to obtain the non-edge denoising image. Finally, the two de-noised areas are fused by addition operation to get the final de-noised image.

3 Results and Discussion We select CT images to verify the effectiveness of the algorithm proposed in this paper. At the same time, the denoising effect of the proposed algorithm is compared horizontally with similar algorithms, such as median filtering algorithm, adaptive wavelet denoising algorithm and TV image denoising model. During the experiment, Gaussian noise with the mean value of 1 and variance of 0.8 was first added to the original CT image. Secondly, the parameters of various denoising algorithms are set. The window size of the median filtering algorithm is 5 × 5. In the TV image denoising model, R = I (unit operator), λ = 0.01, t = 5, and the number of iterations is 50. The simulation results corresponding to the four denoising methods are shown in Fig. 2. Compared with the above three algorithms, the algorithm presented in this paper has a better effect in terms of denoising and preserving image edge details and has an ideal visual effect.

Fig. 2. Comparative images: (a) the original image (b) the image with Gaussian noise (c) the image after median filtering (d) the image after wavelet filtering (e) the image after total variation denoising (f) our method

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To objectively evaluate the quality of image denoising, PSNR (Peak Signal to Noise Ration) and SSIM (Structural SIMilarity) are used in the experiment to assess the quality of denoising effect of different algorithms.The PSNR and SSIM comparison results corresponding to the four algorithms are shown in Table 1 and Table 2. Table 1. PSNR comparison results corresponding to the four algorithms Gaussian noise variance

PSNR/dB Gaussian noise Median image filtering

Adaptive wavelet threshold

Total variational model

Our method

0.4

14.978

14.991

15.121

15.351

20.213

0.6

14.382

14.889

14.537

15.238

20.094

0.8

13.638

14.779

13.792

15.028

18.488

Table 2. SSIM comparison results corresponding to the four algorithms Gaussian noise variance

SSIM Gaussian noise Median image filtering

Adaptive wavelet threshold

Total variational model

Our method

0.4

0.535

0.694

0.567

0.737

0.746

0.6

0.437

0.660

0.464

0.662

0.686

0.8

0.357

0.625

0.388

0.570

0.584

It is not difficult to see from Table 1 and Table 2 that, compared with the traditional denoising algorithm, the algorithm in this paper has outstanding performance in both PSNR and SSIM evaluation algorithms, which fully reflects the superiority of our method.

4 Conclusions Aiming at the problem of medical image denoising, a medical image denoising method based on total variational model and adaptive wavelet threshold is proposed. This method combines the advantages of the two image denoising methods, inhibits the disadvantages of the two methods to a certain extent, and effectively preserves the edge information of the image while denoising. By comparing the proposed method with the other three common denoising methods, it is found that the proposed method has good effects on both visual data and objective data, thus verifying the feasibility of the proposed method. Acknowledgements. This work was supported by Zhejiang Provincial Science and Technology Program in China (2021C03137).

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References 1. Hu, Y., Kong, W., Li, M., Huang, C.: Image denoising method based on edge detection total variation model. Mod. Electron. Tech. 44(05), 52–56 (2021) 2. Rudin, L.I., Osher, S., Fatemi, E.: Nonlinear total variation based noise removal algorithms. Physica D Nonlinear Phenom. 60(1–4), 259–268 (1992) 3. Li, X.: Image Denoising Algorithm Based on Non-Local Self-similarity. South China University of Technology (2020) 4. Chen, H., et al.: Low-dose CT via convolutional neural network. Biomed. Opt. Express 8(2), 679–694 (2017) 5. Won, D.K., An, S., Park, S.H., Ye, D.H.: Low-dose CT denoising using octave convolution with high and low frequency bands. In: Rekik, I., Adeli, E., Park, S.H., Valdés Hernández, M.D.C. (eds.) PRIME 2020. LNCS, vol. 12329, pp. 68–78. Springer, Cham (2020). https:// doi.org/10.1007/978-3-030-59354-4_7 6. Wang, X.: Mining remote sensing image denoising by fusing lifting wavelet threshold and multi-direction edge detection. Remote Sens. Land Resour. 32(04), 46–52 (2020) 7. Wang, F., Zhao, B.T., Jia, X.F.: Wavelet variable threshold denoising method for image. J. Optoelectron. Laser 30(08), 858–866 (2019)

Image Contrast Enhancement Algorithm Based on PSO for Batch Processing Mihang Wang(B) , Aibin Huang, and Caifeng Liu School of Media and Design, Hangzhou Dianzi University, Zhejiang, China [email protected]

Abstract. In many cases, large amounts of images need to be enhanced automatically to get better contrast effects, in other words, need an image contrast enhancement algorithm that can be used for batch processing. Many existed image contrast enhancement algorithms can obtain good enhancement effect under manual intervention, but the need for manual intervention is not suitable for image batch processing. To solve this problem, PSO-UM model was proposed in the paper. In this paper, two parameters were set for the linear unsharp masking (UM) algorithm, and particle swarm optimization (PSO) algorithm was used to dynamically select the best parameters. The best parameters of PSO-UM model were measured through experiments. The proposed algorithm is compared with four algorithms commonly used in batch processing. The experimental results show that proposed algorithm is significantly better than other algorithms in both subjective evaluation and objective indicators, therefore the proposed algorithm is more suitable for batch processing than other algorithms. Keywords: Contrast enhancement · PSO-UM model · Image batch processing

1 Introduction Image contrast enhancement is vital for the comfort and recognition of the human eye. The appropriate image should have adequate details and distinguishable edges. Many image enhancement methods have been proposed, such as unsharp masking (UM), histogram equalization (HE), Wiener filter, image enhancement algorithm based on Retinex model [1]. And unsharp masking algorithm has simplicity and implement easily, which is suitable for image batch processing. Some methods have been proposed to improve UM algorithm to expand its scope of application. Andrea [2] proposed dividing the enhance details into x and y directions and adjust the model’s parameters though the image gradient to achieve better image enhancement. But the algorithm needs to set contrast boundary artificially. Vikrant [3] combining Non-Linear Polynomial Filters (NPF) and UM algorithm for human breast image enhancement, but the algorithm needs to set parameters according to medical prior knowledge. Deng [4] proposed the image enhancement algorithm based on generalized linear system and unsharp masking. The algorithm also requires adjust two parameters artificially to control the contrast and sharpness of the enhancement. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 99–104, 2022. https://doi.org/10.1007/978-981-19-1673-1_17

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These proposed algorithms truly can make a better image enhancement with controlling parameters artificially. However, these algorithms controlling parameters artificially also make algorithm cannot apply for batch processing. Particle swarm optimization (PSO) algorithm [5] is a swarm intelligence optimization algorithm which was first proposed by Kennedy and Eberhart in 1995. PSO algorithm has advantages of few parameters, easy implementation and simple operation [6]. Inspired by the image enhancement algorithm based on improved PSO proposed by Gao [7], this paper further simplifies its algorithm model and proposes the PSO-UM model suitable for batch processing. After the subsequent experimental demonstration, the proposed algorithm can enhance the image better than other algorithms without human intervention, achieving the purpose of batch processing application.

2 PSO-UM Model 2.1 Parameter of UM The proposed algorithm adds two parameters to UM algorithm: B = A − xA + Ay 0.7 < x < 1.3 0 < y < 2

(1)

B is the output image, A is the original image, A is the original image after mean filtering, x, y are the parameters. x can determine the ratio of the high-frequency part of the image, and y can determine the brightness and darkness of the image. 2.2 Modification of PSO For the initialization of PSO, this paper uses a fixed sequence to initialize. Fixed sequence initialization has two advantages: one is the simplicity and efficiency, the other is the consistency of running results. As for the effectiveness of the fixed sequence initialization PSO algorithm, Han [8] has demonstrated the effectiveness of the pseudo-random number generator (PRNG) through experiments in his paper. The fixed sequence used in this paper is the PRNG with uniform distribution. The specific initialization method of PSO is shown in Formula (2): xk = a + b ∗ ((k%num)/num) yk = c + d ∗ k/swarmsize

(2)

xk ,yk represents x, y of the k th particle in Formula (1). And a, b, c, d are the parameters of the Formula (2). swarmsize is the size of the particle swarm, and num is the size of the particle in parameter x. In this algorithm, image entropy is used as the evaluation function: S=E S is the score of images; E is image information entropy.

(3)

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The evaluation function scores the enhanced result of each particle, and records the best particle’s position in global array to update the position of subsequent particles. In order to decrease the running time of the program to faster batch processing, the algorithm only uses global array information to update the position of each particle. As shown in Formula (4): (x, y)i = (x, y)i−1 + w ∗ [(xmax , ymax ) − (x, y)i−1 ]

(4)

(x, y)i is the position of the output when iterating i times, (x, y)i−1 represents the position of the input when iterating i-1 times, w represents the weight, (xmax , ymax ) represents the position of the best particle when iterating i − 1 times. We use linear update strategy [9] update W, use Formula (4) to ensure the uniqueness of the algorithm results. The specific updating formula of W is shown in Formula (5): wi = 0.5 + 0.5 ∗ i/maxIter

(5)

wi is the weight of the ith iteration, and maxIter is the total number of iterations. The experimental results show that when the number of iterations set 15, the number of particle swarm set 12, a set 0.7, b set 0.6, c set 0, d set 2, num set 6 (num is half of the number of particle swarm), and the model can find the solution quickly. 2.3 PSO-UM Model The algorithm flow chart of PSO-UM model proposed in this paper as follows (Fig. 1):

Fig. 1. Flow chart of the proposed method.

First, the PSO particle swarm is initialized with Formula (2), and each particle carries two parameters x and y in Formula (1). Then, the original image is enhanced by Formula (1), and the enhancement result B is obtained. Next, each particle passes its enhancement result B to the evaluation function, which scores the enhancement result according to Formula (3). Meanwhile, the algorithm records the best particle’s location in global array. Then, each particle updates the current position according to Formula (4). Finally, repeat until the number of iterations is reached.

3 Result and Discussion This section mainly compares the proposed algorithm with other algorithms from two aspects: subjective evaluation and objective indicators. The result of proposed algorithm in this section are obtained by using the optimal parameters in Sect. 2.2.

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3.1 Subjective Evaluation In this section, the proposed algorithm is compared with four algorithms commonly used in batch processing. The experimental results are shown as follows:

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 2. Lena image. (a) Original image. (b) histogram equalization. (c) unsharped masking. (d) Retinex. (e) wavelet transform. (f) Proposed method.

Histogram equalization algorithm, the algorithm based on Retinex, the algorithm based on wavelet transform truly can increase the image contrast, but the pattern details of hat also lost as the same time. Unsharped masking algorithm can improve the details perfectly, but cannot increase the image contrast. The proposed algorithm can increase the contrast while preserving the pattern details. It supported that the proposed algorithm has better result of enhancement than other algorithms. 3.2 Objective Indicators In this section, image information entropy was used to compare the proposed algorithm with other algorithms. The experimental data are obtained by measuring each image in Fig. 2. The experimental results are shown as follows. The maximum value has been bolded (Table 1). It supported that the proposed algorithm has the better result of enhancement than other algorithms, which further suggested the proposed algorithm is suitable for batch processing.

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Table 1. Image entropy of each image Various enhancement results of lena

Entropy

Original image

7.4451

Histogram equalization

5.9749

Unsharped masking

7.4966

Retinex

7.7641

Wavelet transform

7.4344

Proposed method

7.7923

4 Conclusions The PSO-UM model is proposed in this paper. In this paper, it was shown that the proposed algorithm is superior to other algorithms in both subjective evaluation and objective indicators. The results hint that the PSO-UM model is more suitable for batch processing than other algorithms. Acknowledgements. This research is supported by Zhejiang Provincial Science and Technology Program in China (2021C03137).

Statement of Ethical Approval. I certify that this paper is original and has not been published and will not be submitted elsewhere for publication while being considered by Mihang Wang. And the study is not split up into several parts to increase the quantity of submissions and submitted to various journals or to one journal over time. No data, text, or theories by others are presented as if they were our own. The image of Lina was entitled to be applied in this paper. The submission has been received explicitly from all co-authors. And authors whose names appear on the submission have contributed sufficiently to the scientific work and therefore share collective responsibility and accountability for the results. Conflict of Interest. The authors declare that they have no conflict of interest.

References 1. Wang, H., Zhang, Y., Shen, H., Zhang, J.: Review of image enhancement algorithms. Chin. Opt. 10(04), 438–448 (2017) 2. Polesel, A., Ramponi, G., Mathews, V.J.: Image enhancement via adaptive unsharp masking. IEEE Trans. Image Process. 9(3), 505–510 (2000) 3. Bhateja, V., Mukul, M., Shabana, U.: Human visual system based unsharp masking for enhancement of mammographic images. J. Comput. Sci. 21, 387–393 (2017) 4. Deng, G.: A generalized unsharp masking algorithm. IEEE Trans. Image Process. 20(5), 1249– 1261 (2011) 5. Kennedy, J., Eberhart, R.C.: Particle swarm optimization. In: IEEE International Conference on Neural Network, Perth, Australia, pp. 1942–1948 (1995)

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6. Bowen, Y., Weiyi, Q.: Summary on improved inertia weight strategies for particle swarm optimization algorithm. J. Bohai Univ. (Nat. Sci. Ed.) 40(03), 274–288 (2019) 7. Qinqing, G., Zeng, G., Chen, D., et al.: Image enhancement technique based on improved PSO algorithm, pp. 234–238. IEEE (2011) 8. Han, W.: Research and Implementation of GPU-Based Swarm Intelligence Algorithm. Xi’an University of Technology (2019) 9. Song, M., Mo, L., Zhou, K.: Influence of inertia weight and learning factor on performance of standard PSO algorithm. J. Jishou Univ. (Nat. Sci. Ed.) 40(04), 24–32 (2019)

Adaptive Partition Total Variation Algorithm for Medical Ultrasound Image Denoising Mengmeng Zhang(B) , Aibin Huang, Ruyu Zhai, and Saqing Wang School of Media and Design, Hangzhou Dianzi University, Zhejiang, China [email protected]

Abstract. Medical ultrasound images are affected by multiplicative speckle noise in the process of imaging. It causes the quality and readability of the image to decrease. An adaptive partition total variation algorithm to denoise images is proposed by the noise characteristic of ultrasound images. Firstly, the image is divided into texture region and flat region by the Wa-Harris algorithm. Then the multiplicative noise is transformed into additive noise by logarithmic transformation. For the texture region, the anisotropic L1 norm total variation (AL1-TV) denoising model is used. For the flat region, the isotropic L2 norm total variation (IL2-TV) noise denoising model is used. Additionally, the split Bregman iterative algorithm is used to solve the total variation (TV) model quickly. Finally, the image is reconstructed by exponential transformation to achieve the ideal denoising effect. The experimental results show that it’s a significant model based on the Wa-Harris algorithm to remove the speckle noise of medical ultrasound images. Keywords: Multiplicative speckle noise · TV model · Split Bregman · Image segmentation

1 Introduction Ultrasound imaging technology has widespread applications in the field of medical diagnosis due to low cost, convenient use, real-time imaging, and non-destructive testing [1, 2]. In the process of ultrasonic imaging, particles with different brightness and darkness will be generated in the image, that is, speckle noise. It is generally considered that speckle noise conforms to Rayleigh distribution [3]. Removing the multiplicative speckle noise in ultrasound images can not only enormously improve the readability of images but also speed up the diagnostic efficiency of doctors. It is easy to blur the edge and texture of images by the classical TV model based on the isotropic L2 norm, although it is effective to remove noise. The ROF model was proposed by Rudin, Osher, Fatemi [4] to overcome the defect. It could remove noise by the ROF model. Meanwhile, it retained the edge and texture of the image by the model. However, the step effect in the flat region of the image appears by the model. For the sake of addressing the step effect, some improvements based on the TV algorithm are proposed. Song proposed a generalized TV denoising model based on L1+P , 0 < p < 1 norm [5]. Zhang proposed a model of choosing L1+P norm according to the © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 105–112, 2022. https://doi.org/10.1007/978-981-19-1673-1_18

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characteristics of each pixel [6]. They are effective in denoising additive noise. The noise of ultrasound images is multiplicative speckle noise that obeys Rayleigh distribution, which is different from the traditional additive noise. Shi derived the log-TV model, which converted the multiplicative problem into an additive one [7]. Chen proposed a non-local adaptive dictionary, based on the Bioucas Figueiredo (BF) model and the non-local sparse model, for multiplicative noise removal [8]. Nevertheless, all the above mentioned methods can not perfectly preserve vital information such as the edge and detail of the ultrasound images. In this paper, an adaptive partition TV algorithm is proposed to remove the multiplicative speckle noise of ultrasound images. The experimental results hint that it is an effective method by this algorithm.

2 Our Method The processing process of ultrasound images is as follows. Firstly, combining the advantages of the Watershed algorithm (Wa) and Harris corner detection algorithm, the WaHarris algorithm is presented to segment ultrasound images into texture and flat regions. Secondly, the ultrasound image is processed in a logarithmic domain to transform multiplicative noise into additive noise. Finally, the AL1-TV model is used to denoise the texture region, and the IL2-TV is used to denoise the flat region. The split Bregman iterative method [9] is used to solve the TV model. 2.1 Wa-Harris The noise of ultrasound images has its peculiar character. The noise is not easily treated for it hardly regarded as corner points which are unlike traditional Gaussian noise or salt and pepper noise. As shown in Fig. 1, the Wa-Harris algorithm divides the ultrasound image into several regions by the watershed algorithm. According to the number of corners and edge points detected by the Harris corner detection algorithm, it can judge whether the region is a texture region or a flat region. Firstly, an ultrasound image I is divided into n blocks by watershed algorithm. I=

n−1 0

Ii , n > 1.

(1)

I i is the sub-image after segmentation. A corner detection algorithm is determined the number of corner and edge points in each block   u Ei (u, v) = [u, v]Mi , (2) v    (Ii )2x (Ii )x (Ii )y w(x, y) . (3) Mi = x,y (Ii )x (Ii )y (Ii )2y

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Ei (u, v) represents the grayscale change within the window. w(x, y) is a function of the Gauss window. (I i )x , (I i )y are the partial derivative of the image function in x, y directions, and M i is the covariance matrix of the gradient. The value of the corner response function Ri determines whether the pixels are corners and edges Ri = det Mi − k(trace Mi )2 ,

(4)

⎧ Ii ∈ I0 ⎨ Ri < 0, 0 ≤ Ri ≤ t, Ii ∈ I1 . ⎩ |Ri | > t, Ii ∈ I0

(5)

detM i is the product of the M i eigenvalues of the matrix, and traceM i is the sum of the M i eigenvalues. t is the threshold, I 0 is the texture region, I 1 is the flat region. In the end, the ultrasound image is divided into texture region and flat region.

Fig. 1. Wa-Harris algorithm flow chart

2.2 Lp-Norm Total Variation The multiplicative speckle noise model of the ultrasound image is as follows. y = n · u.

(6)

u is the original image. y is the noise image. n is the multiplicative speckle noise with Rayleigh distribution mean 0, variance σ 2 , and noise density function is. p(x) =

x2 x exp(− ). σ2 2σ 2

(7)

Convert the logarithm of (6) to log y = log u + log n.

(8)

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Transforming multiplicative noise into additive noise. Make f = log y, g = log u, combined with the TV model for image denoising. The traditional TV model only abides by one normal form, so that it has limitations in detail processing. The L1 norm TV model only preserves texture information, while the L2 norm TV model just smooths noise in flat region. Combination with the above two models, the Lp norm TV models for multiplicative speckle noise reduction are proposed. g = arg min∇gp + g

λ g − f 22 . 2

(9)

The former is a regular term and the latter is a fidelity term. λ is a constant that control the ratio of them. The value of p is adjusted to adapt to denoising of different regions. In this paper, the split Bregman iterative algorithm is selected to improve the time efficiency of the model. When p = 1 in (9), the AL1-TV model has an anisotropic advantage. When the TV is minimized, there is no diffusion in the normal direction of the edge, and the diffusion only exists in the tangent direction. Thus, the AL1-TV model preserves the image details, which is suitable for dealing with the noise in the texture region. The formula is as follows: g = arg min∇g1 + g

λ g − f 22 , 2

(10)

 such that ∇g1 = i,j (|(∇ x g)i,j | + |(∇ y g)i,j |). To apply Bregman, ∇g is replaced by d to solve the problem. Then, a penalty function entry is added to weakly execute the constraint in the formulation (g k+1 , d k+1 ) = mind 1 + d ,g

λ μ g − f 22 + d − ∇g − bk 22 , 2 2

bk+1 = bk + ∇g k+1 − d k+1 .

(11) (12)

The generalized split Bregman algorithm is applied to solve the minimization problem. (11) is divided into two parts, g and d, which are iteratively minimized. Due to the system is strictly diagonally dominant, the Gauss-Seidel method is selected. There is no coupling between the d elements, and the contraction operator can be used to calculate the optimal value of d. It’s available by arranging. ⎧

2 ⎪ g k+1 = min λ2 g − f22 + μ2 d − ∇g − bk 2 ⎪ ⎨ g   k+1 = shrink ∇g k+1 + bk , 1 , (13) d ⎪ μ ⎪ ⎩ k+1 = bk + ∇g k+1 − d k+1 b where shrink(x, γ ) =

x |x|

∗ max(|x| − γ , 0).

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When p = 2 in (9), the IL2-TV model is isotropic. It ensures that the gradient variation is minimized when the image is restored. The IL2-TV performs the same processing in the normal and tangential directions. Therefore, it tends to handle the noise in the flat region. IL2-TV follows the formula: g = arg min∇g2 + g

λ g − f 22 , 2

(14)

  such that ∇g2 = i,j (∇x g)2i,j + (∇y g)2i,j . Similar to solving the AL1-TV. Note that the d variables do not decouple as they did in the anisotropic case. The generalized shrinkage formula is still used to solve the minimization problem. It’s available by arranging: ⎧

2 ⎪ g k+1 = min λ2 g − f 22 + μ2 d − ∇g − bk 2 ⎪ ⎨ g   k k k+1 = max sk − 1 , 0 ∇g +b , (15) d ⎪ μ sk ⎪ ⎩ k+1 b = bk + ∇g k+1 − d k+1  where sk = (|∇x g k + bkx |)2 + (|∇y g k + bky |)2 . It is more effective by the split Bregman algorithm because that turns the problem into a minimization problem, which reduces the computational difficulty and converges to the final result more quickly.

3 Results and Discussion Three sets of images were selected to evaluate and test this article, including ultrasound images of the ovary and fetal legs and arms. The test images were all 512 * 512. Multiplicative speckle noise with noise intensity of 0.05, 0.1 and 0.15 was added to each ultrasound image. In order to make the image meaningful in the logarithmic domain, the gray value is adjusted to [1,256]. In the final exponential transformation step, the gray value is normalized to [0,255]. The algorithm is compared with L2TV and L1TV, which are solved by the split Bregman iteration. To objectively estimate the quality of the denoised image, the Peak Signal to Noise Ratio (PSNR) and Structural Similarity (SSIM) is used to evaluate the results. In this paper, the parameters needed to be set manually, λ = 0.05, μ = 0.1, and the maximum iteration times are 100 or to l = 0.001. It is not difficult to see in Fig. 2 that the L2TV-SB algorithm produces serious smoothing to the image, blurring the image details. This is attributable to the fact that the square of L2 norm erases the noise while also blurring the details of the images. L1TV-SB algorithm is prone to step effect. The generation of the step effect is that the L1 norm changes the continuous smooth signal into segmented equivalent signal, which causes discontinuous gray jump on the image. Comparatively speaking, it exhibits the best visual appearance by our proposed method from Fig. 2. It shows that our model reduces much more multiplicative noise and preserves textures better. Additionally, Table 1 lists the PSNR and SSIM values to measure the denoising performance of different TV-based models. It is apparent that the

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a.original

b.noise

c.L2TV-SB

d.L1TV-SB

e.Ours

Fig. 2. Column a is the original image. Column b is the noise image with a noise intensity of 0.1. Column c is the L2TV-SB denoising result image. Column d is the L1TV-SB denoising result image. Column e is our method denoising result image. The first row is ultrasound images of the fetal leg. The second row is images of the fetal arm. The third row is images of the ovary

model proposed in this paper attains the highest values among all the TV-based noise removal models. It indicates that the image constructed by our method is closer to the original image than other methods. The running time in Fig. 3 shows the algorithm efficiency of the TV model based on split Bregman has been improved by nearly 30% than the traditional gradient descent method. The split Bregman algorithm is easily parallelizable, since it makes extensive use of Gauss-Seidel and shrinkage formula. Moreover, compared to gradient descent, it also has a relatively small memory footprint.

Fig. 3. Compare the time efficiency of the split Bregman with the traditional gradient descent algorithm under the same number of iterations. The horizontal axis is the number of iteration times, and the vertical axis is the running time

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Table 1. Comparisons of the results using different models based on various images (The second column is noise intensity. Italics indicates the best result) Image

σ

L2TV-SB PSNR

SIMM

PSNR

SIMM

PSNR

SIMM

Leg

0.05

32.1376

0.7089

32.1805

0.7744

32.6396

0.7987

0.10

30.1233

0.7063

31.9400

0.7700

32.3181

0.7820

Arm

Ovary

L1TV-SB

Ours

0.15

31.6900

0.7037

31.7115

0.7470

31.9027

0.7724

0.05

32.8616

0.7397

32.6536

0.8098

33.3837

0.8128

0.10

32.8300

0.7384

32.5717

0.8044

33.2869

0.8110

0.15

32.8006

0.7372

32.5272

0.7980

33.2458

0.8250

0.05

31.8511

0.6379

31.7759

0.7250

32.5261

0.7699

0.10

31.8481

0.6396

31.7567

0.7194

32.4960

0.7680

0.15

31.8382

0.6365

31.7428

0.7148

32.4189

0.7636

4 Conclusions In this paper, an adaptive partition total variation algorithm is proposed by the noise characteristics of ultrasound images. Combining the Watershed and Harris algorithm, the Wa-Harris algorithm is proposed to divide ultrasound images into texture and flat regions. The noise of ultrasound images is multiplicative speckle noise that obeys Rayleigh distribution. The multiplicative noise is converted to additive noise by log-domain processing. The total variation model of the LP norm is proposed. AL1-TV algorithm is applied to remove noise in the texture region, IL2-TV is used to remove noise in the flat region. The split Bregman iteration algorithm is applied to the Lp-TV denoising model. It hints that the adaptive partition TV algorithm suggested by us might be a more effective method to denoise medical ultrasound images according to the experimental results.

Statement of Ethical Approval. I certify that this manuscript is original and has not been published and will not be submitted elsewhere for publication while being considered by Mengmeng Zhang. The images are captured by ultrasound imaging systems from Women’s hospital School of Medicine Zhejiang University. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. Conflict of Interest: The authors declare that they have no conflict of interest. This article does not contain any studies with human participants or animals performed by any of the authors. Informed consent was obtained from all individual participants included in the study.

References 1. Baun, J., Jedrezejewicz, T., et al.: Advances in ultrasound imaging architecture: the future is now. J. Diagn. Med. Sonogr. (2021). https://doi.org/10.1177/8756479321996274

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2. Tilakraj, N., Ravikumar, K.M.: Analysis of speckle diminution in ultrasound images—a review. In: Sridhar, V., Padma, M.C., Rao, K.A.R. (eds.) Emerging Research in Electronics, Computer Science and Technology. LNEE, vol. 545, pp. 937–947. Springer, Singapore (2019). https:// doi.org/10.1007/978-981-13-5802-9_82 3. Bian, H.: Analysis of speckle distribution and denoising in medical ultrasound. Zhejiang University, R318.6, TP391.41 (2013) 4. Rudin, L.I., Osher, S., Fatemi, E.: Nonlinear total variation based noise removal algorithms. Physica D Nonlinear Phenom. 60(5), 259–268 (1992) 5. Song, B.: Topics in Variational PDE Image Segmentation, Inpainting and Denoising. University of California Los Angeles, USA (2003) 6. Ying, H., Peng, Q.: Total variation adaptive image denoising model. Optoelectronics 33(3), 50–53 (2006) 7. Shi, J., Osher, S.: A nonlinear inverse scale space method for a convex multiplicative noise model. SIAM J. Imaging Sci. 1(3), 294–321 (2008) 8. Chen, L., He, C., Wang, X.: Multiplicative noise removal via non-local adaptive dictionary (2017). https://doi.org/10.16208/j.issn1000-7024.2017.09.029 9. Goldstein, T., Osher, S.: The split Bregman method for L1-regularized problem. Image Sci. (2009). https://doi.org/10.1137/080725891

Study on Sharpness Evaluation Method of Vehicle Imaging System Chunzhi Xu1(B) , Jing Cao1,2 , Anda Yong1 , Zhuoran Zhang1 , and Hongli Liu1 1 College of Media and Design, Hangzhou Dianzi University, Zhejiang, China

[email protected] 2 Graduate School of Creative Industry Design, National Taiwan University of Arts,

Taiwan, China

Abstract. A vehicle camera represents the “eyes” of vehicle intelligence and is the core of the driving visual assistance system. Its image quality directly determines a driver’s early-warning and driving safety. This study aims at the essential technical requirements for the vehicle imaging equipment’s output image quality evaluation, and devises a method for data collection, processing, and analysis of sharpness for vehicle imaging quality evaluation. It also establishes a vehicle-imaging quality assessment process to sharpness. The results have a great actual application value for vehicle intelligence. Keywords: Vehicle imaging · Image quality evaluation · Sharpness · MTF

1 Introduction In recent years, as an essential visual assistance tool to reduce traffic safety hazards and ensure driving safety, vehicle cameras have gradually become a hot spot in the automotive imaging market [1]. Scientifically evaluating the sharpness of vehicle imaging systems is the critical research content of experts in automatic driving. In a review of relevant research results, foreign research focuses on driving visual assistance systems. In 2017, Young-Jun Ko and others proposed the image acquisition model for the hyperbolic reflector imaging system and an image reconstruction algorithm for a horizontal panoramic and vertical aerial view of ground scenes, realizing the vehicle’s panoramic and aerial view observation [2]. Meanwhile, domestic research focuses on the application and development of vehicle imaging systems. In 2019, Jia Huizhen and others put forward a multi-feature fusion-image quality evaluation method to solve prediction problems of human visual characteristics and pooling strategies [3]. In this case, this study intends to apply the test charts to express image sharpness by Modulation Transfer Function (MTF), and to obtain the quality variations of the vehicle imaging system in various scenarios, thus providing solutions for the scientific evaluation of the vehicle imaging system, and for the adaptation to actual situations.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 113–120, 2022. https://doi.org/10.1007/978-981-19-1673-1_19

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2 Related Techniques and Principles 2.1 Composition of the Vehicle Imaging System The vehicle imaging system is a vehicle driving recording device used for driving assistance and intelligent driving [4]. It is primarily composed of three parts: vehicle camera module, transmission line, and vehicle monitor. The composition of a vehicle camera is shown in Fig. 1.

Fig. 1. Composition of a vehicle camera

When a vehicle camera module shoots the object, the latter forms a digital signal on the image sensor through the lens, and the digital signal processor processes the digital signal to extract the target features. In this case, sharpness is the most vital feature to realize object classification and recognition in an image. 2.2 Sharpness and MTF Sharpness is a significant image quality parameter to reflect the detail clarity of images [5]. MTF can evaluate an optical system’s abilities in contrast transfer and detail resolution [6]. Therefore, the sharpness of an image obtained by the imaging system can be evaluated scientifically by analyzing the MTF curve. (1) Point Spread Function (PSF) PSF is the impulse response function of pointing the light source imaging in an optical system, as shown in Fig. 2. Set h(x, y) as the light intensity distribution function. The light intensity distribution of PSF is shown in Eq. (1), where “*” represents convolution calculation. g(x, y) = f (x, y) ∗ h(x, y)

(1)

The complex variable function of OTF is the two-dimensional Fourier transform of the following function:        OTF fx , fy = H fx , fy exp∅ fx , fy (2)

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     Where, H fx , fy  is the MTF, and ∅ fx , fy is the phase transfer function. If the phase transfer function is not considered, PSF(x, y) can obtain MTF through two-dimensional Fourier transform, as shown in Eq. (3). ¨ +∞ PSF(x, y)dxdy (3) MTF(u, v) = −∞

(2) Line Spread Function (LSF) LSF is the superposition of PSF in one direction, as expressed in Eq. (4). It can also be regarded as a two-dimensional convolution between the impulse response of the optical system and a linear light source, as indicated in Eq. (5). g(x, y) = LSF

(4)

g(x, y) = LSF(x) = f (x, y) ∗ h(x, y)

(5)

The integral representation of LSF is as follows:  +∞ LSF(x) = PSF(x, y)dy

(6)

MTF is the Fourier transform module of LSF(x), as expressed in Eq. (7):  +∞    MTF(u) =  LSF(x)e−i2π ux dx

(7)

−∞

−∞

(3) Edge Spread Function (ESF) ESF is the convolution of PSF and step(x)l(y) response function of the imaging system, as presented in Eq. (8). g(x, y) = ESF(x) = PSF(x, y) ∗ step(x)l(y)

(8)

It can be obtained by overlapping LSF in the horizontal direction after displacement, based on Eq. (9). Thus, it is the cumulative result of LSF.  x   ESF(x) = LSF x dx (9) −∞

LSF can be obtained as the derivative of ESF, as shown in Eq. (10). d ESF(x) = LSF(x) dx

(10)

Hence, MTF can be obtained by the Fourier transform of LSF. The relationship among PSF, LSF, ESF, and MTF is illustrated in Fig. 3.

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Fig. 2. PSF formation

Fig. 3. Relationship between PSF, LSF, ESF, and MTF

3 Evaluation Process and Algorithm Design of Vehicle Imaging Sharpness 3.1 Sharpness Evaluation Process of Vehicle Imaging This study takes the digital vehicle imaging system as its research objective, aiming at the system’s principles and characteristics based on the analysis of the imaging quality evaluation’s attributes and parameters. It then constructs a vehicle-imaging quality evaluation process based on an improved sharpness evaluation algorithm, as indicated in Fig. 4.

Fig. 4. Design process of the vehicle-imaging sharpness evaluation.

3.2 Sharpness Evaluation Algorithm of Vehicle Imaging When the traditional slant edge method measures the MTF, it is vital to project along the edge direction to obtain multiple sampling points and fit the ESF and the LSF.

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However, it is challenging to strictly align the rows or columns of the edge and the array surface during a test, and the accuracy of the ESF may not be sufficient, leading to the low accuracy and poor repeatability of the system’s MTF test. Thus, this study applies the inter-class variance-maximization threshold segmentation algorithm (Otsu) [7] to obtain the optimal threshold, utilizing it as the high threshold of the Canny operator to obtain a segmented image with a target edge region illustrated in Fig. 5. To obtain more sampling points and make the ESF curve more accurate, bilinear interpolation is applied to resample the pixels on both sides of the vertical edge direction. The gray values on both sides of the vertical slant edge are obtained, the edge image of the slant edge into the ESF curve and LSF of the vertical edge are converted, and then Hanning window filtering processing and Fourier transforms are performed on the LSF to obtain the MTF curve of the vehicle camera module.

Fig. 5. (from left to right) The actual edge graph, the edge image of the traditional doublethreshold Canny operator, and the Otsu threshold Canny operator graph

4 Implementation of Sharpness Evaluation Algorithm for Vehicle Imaging 4.1 Experimental Environment Construction To obtain MTF more accurately, this study constructed a test scene in conformance with ISO 12233:2014 standard. It set the geometric positions of the plate and the device under test according to QC/T1128-2019 standard, as presented in Fig. 6.

Fig. 6. MTF test scene

4.2 Algorithm Implementation After resampling the vertical slant edge pixels, bilinear interpolation was used to calculate the gray values on both sides of the vertical slant edge and obtain the adjusted

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vertical edge figure, as illustrated in Fig. 7. After screening the optimal resampling step T and the deviation, when the resampling step is 1/5, the difference with the ideal MTF is the smallest, as tabulated in Table 1. The least-squares method is applied to find the optimal model and fit the observation data to obtain the final edge fitting line.

Fig. 7. The ideal vertical edge sampling graph (left) and the ideal vertical edge non-vertical sampling graph (right)

Table 1. Sampling step and deviation Step T

1/2

1/3

1/4

1/5

1/6

1/7

1/8

1/9

1/10

1/11

Deviation

0.012

0.013

0.015

0.010

0.014

0.015

0.016

0.015

0.016

0.016

The ESF curves are obtained by geometric projection of each row of pixel data in the processed vertical edge image. If the image has m-row pixels in the longitudinal direction, m ESF and LSF curves can be obtained. The LSF curves can be divided into the central peak area and the smooth area on both sides, with only the former representing the information points on both sides of the edge as the valuable data of MTF. By processing LSF using the Hanning Windows function, the data values in the smooth area on both sides gradually approaches 0, eliminating redundant data and noise. 4.3 Results Comparison Figure 8 presents the MTF curve comparison of the algorithm proposed in this study and that of the Imatest software. The MTF value of the proposed algorithm is consistent with that of Imatest in the high-frequency and middle-frequency bands; meanwhile, that in the low-frequency band is lower, which has better noise suppression. Moreover, the comparison of MTFA , MTF20 , and MTF50 indicates that the results in this study have relatively high robustness. MTF20 is applied to evaluate the visual limiting resolution of the imaging equipment, while MTF50 has a a high correlation with the image contour. Basing on Table 2, the K3U module has a relatively high imaging quality and can present more image details, while the AR023 module has the worst imaging quality and detail performance, which is consistent with reality.

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Fig. 8. A comparison diagram of the Imatest test results and those of the proposed algorithm.

Table 2. MTF20 , MTF50 , and MTFA test results of the four vehicle imaging modules Vehicle camera module

MTF20

MTF50

MTFA

K3U module

0.711

0.462

0.473

OV10635 module

0.421

0.219

0.288

AR023 module

0.522

0.183

0.275

LS29-USB module

0.688

0.312

0.389

5 Conclusions This study clarifies the sharpness evaluation of the vehicle imaging system, establishes the sharpness evaluation process and algorithm of the vehicle imaging system, and emphatically analyzes the factors influencing the calculation accuracy of the slant edge method. The optimal threshold determined by the inter-class variance-maximization threshold segmentation algorithm is applied as the high threshold of the Canny operator to obtain the segmented image containing the target edge and determine the edge-fitting line. The optimal resampling step size and its accurate edge curve are determined by bilinear interpolation and simulation experiments. The Hanning window function is utilized to eliminate noise and obtain more accurate MTF test results. Overall, the sharpness evaluation method proposed in this study provides a practical method for applying the vehicle imaging system in future automatic driving. Acknowledgment. This work is funded by Digital Imaging Theory-GK188800299016-054.

References 1. Wang, R.: Multi-camera Joint Calibration Based on Vehicle. Xidian University (2017) 2. Ko, Y.J., Yi, S.Y.: Catadioptric imaging system with a hybrid hyperbolic reflector for vehicle around-view monitoring. J. Math. Imaging Vis. 60(1), 1–9 (2017)

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3. Jia, H.Z., Wang, T.H., Fu, P.: Multi-feature fusion based image quality assessment method. Pattern Recognit. Artif. Intell. 32(07), 669–675 (2019) 4. Su, W.X.: Design of high frame frequency CMOS image sensor system. Chin. J. Liq. Cryst. Displ. 28(06), 955–962 (2013) 5. Giger, M.L., Doi, K: Investigation of basic imaging properties in digital radiography. I. Modulation transfer function. Med. Phys. 11(3), 287–295 (1984) 6. Yu, Q.: Research on MTF Testing Methods of Optical Inspection Lenses. Zhejiang University, Hangzhou (2010) 7. Sun, W.S., Tien, C.L., Tsuei, C.H., Pan, J.W.: Simulation and comparison of the illuminance, uniformity, and efficiency of different forms of lighting used in basketball court illumination. Appl. Opt. 53(29), 186–194 (2014)

Study on the Evaluation Method of the Clarity of Critical Areas of Digital Images Hangning Wang(B) , Qiang Wang, Chen Shao, and Ruze Zhuang College of Media and Design, Hangzhou Dianzi University, Zhejiang, China [email protected]

Abstract. In response to the current needs of machine vision systems for digital image clarity evaluation methods, this paper proposes a scientific and objective image critical area clarity evaluation method, focusing on the critical areas of the image, fusing the edge features and texture features of the critical areas of the image, and Using the machine learning method of Support Vector Regression (SVR), and established an accurate evaluation model for the clarity of critical areas of digital images from the feature information to the clarity score. The evaluation result of the definition of the critical area of the image is consistent with the subjective image quality of the database. Keywords: Clarity · Critical area · SVR

1 Introduction Clarity is an important index of digital image information recognition in machine vision, and the clarity of digital image critical areas is priority among priorities to classification and evaluation of image flow in production and life, which directly restricts the reliability and recognition accuracy of digital image application, and it is also a bottleneck problem that the industry needs to break through. Many scholars domestic and international have put forward the methods of digital image clarity evaluation from different perspectives, such as Marziliano [1] put forward a method to estimate the blur degree of image by calculating the average width of image edge in 2002. In 2006, combining edge width and contrast, Rony Ferzli [2] proposed a method of image blurness quality evaluation based on human visual characteristics (JNB). In 2015, Huang Xiaomei introduced wavelet transform to propose a model for blurness evaluation of non-reference image based on CPDB algorithm. In 2018, Rezaie [4] proposed a model that counts local binary features and evaluates image clarity through machine learning. However, their method lacked further study on the clarity which might affect image recognition and processing, of critical and non-critical areas in digital images. Aiming at the shortcomings of the existing image clarity evaluation methods, this paper uses the number of feature points as the critical area and area weight of the digital image, and combines the two features of the digital image edge and texture, proposes a support vector regression machine-based critical area clarity. The evaluation model significantly improves the accuracy of clarity evaluation. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 121–127, 2022. https://doi.org/10.1007/978-981-19-1673-1_20

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2 Related Techniques and Principles 2.1 Critical Regions and Their Feature Extraction The critical area of an image refers to the part of the major body information in an image, which has the characteristics of non-transformation of scale, dense feature points, and complex texture. The sharpness of the critical area of the image is the key to the judgment of the image sharpness, and the use of SURF (Speeded Up Robust Features) feature point detection method image feature point detection is the focus of the feature extraction of the critical area of the image. The edge feature extraction is usually through the HOG (Histogram Of Gradient). HOG is usually used in computer vision and pattern recognition. The histogram is obtained by accumulating the gradient values of a particular block in different directions in the statistical image, and the histogram represents the gradient characteristics of the image block. Images with low clarity will lose details and texture. The Local Binary Pattern (LBP) with invariable gray level can express the local texture characteristics of the image. The gray value of the central pixel is used as the threshold. Among the adjacent 8 pixels, the point greater than the central gray value is recorded as 1, and vice versa, it is recorded as 0, and an eight-bit binary number is obtained, and then mapped to the gray value of the point. 2.2 Support Vector Regression Machine SVR can be used to fuse two different characteristics of the image, evaluation image clarity by machine learning from texture and edge information for critical areas of the image. Figure 1 shows a variety of segmentation methods for training samples, and the ideal optimal segmentation method. The SVR machine can fit and approximate nonlinear continuous functions well, obtain the results of complex nonlinear problems, realize the optimal solution in a limited sample, and solve the local extremum problem.

Fig. 1. Variety of segmentation methods and the optimal segmentation method

2.3 Standard Database The training and verification of the SVR machine needs to select a standard database. LIVE and CSIQ are representative databases for image quality evaluation. They contain source images and distorted images. The DMOS quality index is used. The larger the value, the worse image quality (Table 1).

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Table 1. Image quality evaluation database characteristics Database

Number of source images

Number of distorted images

Index

LIVE

29

779

DMOS (0–100)

CISQ

30

866

DMOS (0–1)

3 Design and Implementation of the Digital Image Clarity Evaluation Model 3.1 Design of Clarity Evaluation Algorithm Firstly, this paper determines and extracts the critical area of the image, and assigns different weight values according to their feature points. Then respectively use HOG and LBP to extract the edge and texture features of the image. Finally, these features are weighted and fused according to the weights of the critical regions and used as the input of the SVR machine to construct the image clarity evaluation model. The specific flow of the algorithm is shown in Fig. 2.

Fig. 2. Critical area clarity assessment method process

3.2 Image Critical Region Extraction Divide the image into size of 16 × 16 pixel blocks, and detect SURF feature detection. Then determine the weight of the image block according to the number of feature points detected by SURF in each image block, the formula is in Eq. (1). ω=

num(SURF mn ) num(SURF 0 )

(1)

Among them SURF mn indicates the number of feature points detected in the image block, SURF 0 indicates the number of SURF detection features in the overall image. Results is shown in Fig. 3.

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Fig. 3. Critical area determine

3.3 Image Feature Extraction In this paper, the image clarity is judged by feature fusion of the two features of contour and texture. Since color and clarity are not very relevant, in order to reduce the amount of calculation, grayscale processing performs on color images. Then use [−1, 0, 1] and [−1, 0, 1]T as the first-order differential template to approximate the gradient. The vertical and horizontal gradients calculated by this method are in Eq. (2) and (3): Gh (x, y) = f (x + 1, y) − f (x − 1, y) ∀x, y

(2)

Gv (x, y) = f (x, y + 1) − f (x, y − 1) ∀x, y

(3)

The calculation method of the direction angle θ of the gradient is as follows in Eq. (4): θ (x, y) = arctan(

Gh (x, y) ) Gv (x, y)

(4)

Each 16 × 16 pixel block is further refined into 4 8 × 8 pixel cells, and then each cell is divided into 9 directions of 20°/ bin. First, perform gradient direction statistics independently in each cell to obtain 9 gradient histograms in different directions, and then normalize within the block to minimize errors caused by environmental factors such as uneven lighting. For extracting texture features, the image is also divided into cells of 8 × 8 pixels, then calculate the LBP feature value of the point in the 8 neighborhood pixels for each pixel, and the LBP feature in the cell is calculated to get the gray value. For edge pixels, their gray values are calculated by the bilinear difference method. Finally, the statistical results in each cell are normalized and then concatenated to obtain the LBP regional texture feature of the image. 3.4 Construction of Clarity Evaluation Algorithm Model In this paper, the process of preprocessing the experimental samples is mainly to normalize the evaluation scores in different image quality evaluation databases, where 80% of the images are used as the data set for model training, and the rest are used as the test set for model performance verification.

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This paper uses Gaussian Radial Basis Function (RBF) as the kernel function of the support vector regression machine to map the training data set to a high-dimensional space to achieve linear segmentation. At this time, the regression function can be expressed in Eq. (5). n (αi − αi ∗ )(φ(x) · φ(xi )) + b f (x) = (5) i=1

4 Comparison of Experimental Results 4.1 Comparison of Critical Region Extraction This paper uses the Mask R-CNN algorithm as a comparison. Extract a picture with 0 DMOS in the LIVE graphics library and perform Gaussian blur processing. Then use the critical region identification method proposed in this paper and the Mask R-CNN algorithm for identification, and the results are shown in Table 2. Table 2. Image critical area recognition rate with different degrees blurness Gaussian blur radius σ

Original image

0.5

2.5

Comprehensive recognition rate of this article (%)

95.4

85.7

67.5

Mask R-CNN (%)

100

89.8

60.9

4.2 Comparison of Clarity Evaluation Results Using this paper’s model to assess the LIVE image database in three different resolution images, it can be seen from Table 3, the algorithm resulting image quality assessment database and predictions given in image quality score has a good consistency, with consistent transformation trend. Table 3. Different blurred degree image score comparison results Image

Image1

Image26

Image107

DMOS

0.3263

0

0.60102

Score

2.73869

6.62923

0.92333

4.3 Comparison of Clarity Evaluation Methods In order to express the performance of the image clarity evaluation model greatly, this paper’s model is compared with the JNB, CPBD, S3 algorithm from the four evaluation data correlations of PLCC, KROCC, SROCC, RMSE. The results are shown in Table 4.

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Database

Index

JNB

CPBD

S3

LIVE

PLCC

0.8162

0.8956

0.9436

KROCC

0.6071

0.7652

0.8004

SROCC

0.7877

0.919

0.9441

RMSE

9.0843

6.9929

5.2058

PLCC

0.8061

0.8818

0.9107

KROCC

0.5976

0.7079

0.7294

SROCC

0.7624

0.8847

0.9059

CSIQ

This paper’s algorithms average score

RMSE

0.1696

0.1351

0.1184

PLCC

0.7895

0.8680

0.9019

KROCC

0.5865

0.6944

0.7051

SROCC

0.7673

0.8780

0.8934

RMSE

2.9209

2.2724

1.7449

5 Conclusions Through the recognition of SURF feature points, this paper realizes rapid identification of critical areas in images. By calculating the image feature information of the critical area of the image, using SVR to get fusion of edge features and texture features. Then compared with other image quality evaluation methods, it is verified that the method in this paper can correctly discriminate critical areas of the image and merge two features, quickly and accurately evaluate the definition of critical areas of digital images without reference. It provides new ideas and methods for the field of image quality evaluation. Acknowledgements. This work was supported by Zhejiang Provincial Science and Technology Program in China (2021C03137).

Statement of Ethical Approval. I certify that this manuscript is original and has not been published and will not be submitted elsewhere for publication while being considered by Hangning Wang. And the study is not split up into several parts to increase the quantity of submissions and submitted to various journals or to one journal over time. No data have been fabricated or manipulated (including images) to support your conclusions. No data, text, or theories by others are presented as if they were our own. The images of Usain Bolt and others were entitled to be applied in the manuscript. The submission has been received explicitly from all co-authors. And authors whose names appear on the submission have contributed sufficiently to the scientific work and therefore share collective responsibility and accountability for the results. Conflict of Interest: The authors declare that they have no conflict of interest. This article does not contain any studies with human participants or animals performed by any of the authors. Informed consent was obtained from all individual participants included in the study.

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References 1. Marziliano, P., Dufaux, F., Winkler, S., Ebrahimi, T.: A no-reference perceptual blur metric. In: Proceedings of the 2002 International Conference on Image Processing, New York, USA, pp. III-57–III-60. IEEE (2002) 2. Ferzli, R., Karam, L.J.: Human visual system based no-reference objective image sharpness metric. In: 2006 IEEE International Conference on Image Processing (2006) 3. Huang, X., Tian, X.: No-reference sharpness assessment for blurred image. J. Chin. Comput. Syst. 36(5), 1117–1121 (2015) 4. Rezaie, F., Helfroush, M.S., Danyali, H.: No-reference image quality assessment using local binary pattern in the wavelet domain. Multimedia Tools Appl. (2017) 5. Zhou, W., Bovik, A.C., Sheikh, H.R., et al.: Image quality assessment: from error visibility to structural similarity. IEEE Trans. Image Process. 13(4) (2004) 6. Narvekar, N.D., Karam, L.J.: A no-reference perceptual image sharpness metric based on a cumulative probability of blur detection. In: Proceedings of International Workshop on Quality of Multimedia Experience (2009) 7. Bare, B., Ke, L., Bo, Y.: An accurate deep convolutional neural networks model for no-reference image quality assessment. In: 2017 IEEE International Conference on Multimedia and Expo (ICME). IEEE (2017)

Scanned Document Image Enhancement Method Based on Lightweight Convolutional Neural Networks Kuang Yin1 , Hongbin Wang2 , Lianhong Zhong2 , Jianbin Ye2 , Yuan La2 , and Zhijiang Li3(B) 1 Electric Power Test and Research Institute, Guangdong Grid Co., Guangdong, China 2 Key Laboratory for Quality Inspection and Testing of Medium and Low Voltage Electrical

Equipment, Guangdong Grid Co., Guangdong, China 3 School of Printing and Packaging, Wuhan University, Hubei, China

[email protected]

Abstract. Aiming at the problem of image degradation in the process of digitization of traditional paper documents, an enhancement method for document image resampling by scanning or photographing is proposed to improve the subjective clarity of document image and character recognition. In order to meet the requirements of readability and OCR accuracy of scanned document images, a lightweight convolutional neural network model is proposed firstly. Secondly, by analyzing the degradation of a large number of actual samples, a combined random degradation model is proposed to simulate the real degradation process, and a small sample data set is generated by the degradation model to train the model. The results show that the recall rate of the processed image is 91.5%, which is 18.3% and 12% higher than that of Laplace and Roberts operators, and the recognition accuracy is 89.0%, which is 43.3% and 30.2% higher than that of Laplace and Sobel operators. Keywords: Image enhancement · Convolutional neural network · Text images · Image super-resolution · Optical character recognition

1 Introduction In the process of digitization of traditional paper documents, it is necessary to resampling the paper documents by scanning, photographing and optical character recognition, etc. The resampling process is affected by factors such as paper breakage and creasing, as well as fading ink colors, which often leads to poor resampling results, poor visual results, and the inability to perform optical character recognition. In order to solve the problems mentioned above, the resample results need to be enhanced and repaired, and the degradation results can be repaired by building a model with good performance and adaptability, which will greatly improve the subjective readability of the documents and provide clear feature input for OCR work.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 128–136, 2022. https://doi.org/10.1007/978-981-19-1673-1_21

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2 Related Work 2.1 Traditional Image Enhancement The traditional image enhancement algorithm originates from the enhancement of high frequency information of two-dimensional signals, so the spatial image enhancement technology based on differentiation can enhance the sharpening degree of the image to some extent. 2.2 Document Image Enhancement for OCR This paper uses a lightweight network model and improves the generalization capability of the model based on feature migration and sample migration methods, making it more focused on the subjective visibility of scanned documents and OCR results.

3 Methodology of This Paper This paper uses deep learning methods to construct feature mapping models, with the using of data-driven approaches, enables the models to adaptively mine image invariant features and gain the ability to potentially degrade the inverse process. 3.1 The Network Structure The model proposed in this paper is inspired by the classical super-resolution convolutional neural network SRCNN (Dong et al., 2015 [8]). SRCNN network is composed of three convolutional layers, which respectively correspond to the process of image feature extraction, nonlinear mapping and image reconstruction process. Convolution kernels for convolutional layers’ size respectively f 1 = 9, f 2 = 1, f 3 = 5. The enhancement of scanned document images can also be divided into three processes: document feature extraction, feature mapping and image reconstruction. The depth model proposed in this paper adopts a seven-layer network structure, and the model structure is shown in Fig. 1.

Fig. 1. Model structure of deep learning proposed in this paper

The first four layers of the network are used to extract text image feature information, the fifth layer is used for feature non-linear mapping, and the sixth and seventh layers of the network complete the reconstruction of the image, and the parameters of the network are set as shown in Table 1.

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Construction

Layer

Number of channels

Kernel size

Step-size

Feature extraction module

1

128

3

1

2

128

3

1

3

64

3

1

4

64

3

1

5

2

1

1

Image reconstruction module 6

1

3

1

7

1

3

1

Feature nonlinear mapping module

Activation Function. In order to achieve a non-linear mapping of image features, t this paper uses a Leaky Rectified Linear Unit (Leaky Rectified Linear Unit, Leaky ReLU) activation after each convolutional layer which can reduce the presence of silent neurons, and supporting backward propagation of shallow feature information. Receptive Field Analysis. Instead of using a large convolution kernel, the network proposed in this paper uses four convolution layers in size of 3 × 3 in the feature extraction process and two convolution layers of the same size in the image reconstruction. Take the two convolution layers of image reconstruction as an example, as shown in Fig. 2, the receptive field of f6 is 3 × 3, the receptive field of f7 is 5 × 5. The receptive field obtained by its superposition is the same as that obtained by using a single convolutional layer whose receptive field size is 5 × 5. A total of 20 parameters need to be calculated, while 26 parameters need to be calculated for the convolutional layer whose receptive field size is 5 × 5. Through this network structure, large receptive fields can be achieved. In the meaning time, the model parameters can be reduced, the model volume can be reduced, the model training can be accelerated, and the model migration and visualization can be facilitated.

Fig. 2. Superimposed convolution layer receptive field analysis

3.2 Loss Function Make the method in this paper generate training sample pairs, i.e., degraded image x and original (HD) image y, by using a combined random degradation model and use

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the squared error (L 2 distance) of the final generated result of the model, f (x), from the original image as a loss function, as shown in Eq. (1): L=

N 

(yi − f (xi )2 )

(1)

i=1

In this equation, N represents the total number of image pixels.

4 Experiments and Analysis of Results 4.1 Generation of Training Samples This paper proposes a combined random degradation model to simulate the real degradation process by analyzing the degradation of a large number of actual samples, as shown in Fig. 3. Used to generate training data sets.

(a)

(b)

(c)

(d)

(a) The original image (b) The bicubic degradation results (c) The gaussian filter degradation results (d) The combined random degradation results

Fig. 3. Combined degradation process proposed in this paper

In the resolution degradation process, bicubic interpolation [9] algorithm (Keys, 1981) is used to obtain low-resolution images by down-sampling three times, and then bicubic algorithm is used to up-sampling three times to obtain images with resolution degradation. A finite Gaussian filter is used to blur the degraded image. Limited gaussian filter is adopted to process the writing blur and degradation process to gain the illegible degraded images. This paper randomly generates degradation models by combining random weighting method, and the generation process of degradation images is shown in Eq. (2): Z(x) = αB(x) + βGθ (x) + γ x

(2)

Where, Z(x) is the degradation sample generated by using the combined random degradation method in this paper; B(x) is the resolution degradation image; βGθ (x) is the degradation image obtained by gaussian blur processing with the kernel size of θ; x

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is the original input image. θ , β, γ is the weighting coefficient and satisfies θ + β + γ = 1. In practice, this paper limits the size of randomly selected Gaussian kernel, that is θ ∈ {3,5,7}. For each generation of each sample, θ, β, γ is randomly selected within a limited range. 4.2 Training Details Image Preprocessing 1) Color space converting First, color space conversion is carried out for all input images, transforming the image from RGB color space to YCbCr color space, and only the brightness information of Y channel is retained. The conversion process is shown in Eq. (3): T (x) = 0.257 × R + 0.564 × G + 0.098 × B + 16

(3)

In this formula, x is the input image, R, G, B respectively correspond to the red, green and blue channel pixel value, and T (x) is the output pixel value. 2) Normalization To normalize the converted gray image, as shown in Eq. (4): ⎧ ⎨ 1 x > 255 x N (x) = 255 (4) 0 < x < 255 ⎩ 0 x2 × 2 cm2 ) perovskite film, and optimized the annealing conditions (90 °C, 50 Pa, 2 min), so that the device showed better stability and scalability. In 2020, Li et al. [9] designed a new mixed ink system to control the crystallization rate of perovskite during ink jet printing. The printed film had good continuity and large grain size, and the optimal annealing temperature at 120 °C was determined. Compared with traditional preparation technologies, ink jet printing has significant advantages in the preparation of perovskite films: It can greatly reduce the production cost and achieve large-scale preparation of film, so it has been widely used in the preparation of optoelectronic devices. The change of printing parameters has a great influence on perovskite materials. Therefore, how to improve the preparation process of ink jet printing perovskite film and make it suitable for industrial production becomes very important. Due to the characteristics above, in this study, the influence on the film-forming properties of perovskite film was studied by changing the printing voltage, droplet spacing, ink droplet size, substrate temperature, annealing temperature and other ink jet printing parameters, and a set of optimal parameters were determined. As a result, a film with uniform orientation and moderate thickness was prepared.

2 Preparation of Thin Film by Ink-Jet Printing In this study, the photoactive layer was prepared by IJP printing of two-dimensional perovskite materials, and the effect of parameters on the apparent morphology of the film was studied. 2.1 Experimental Materials and Instruments Experimental materials: N, N-dimethylformamide (DMF, ≥99.5%), dimethyl sulfoxide (DMSO, Analytically pure), methyl ammonium iodide (MAI, ≥99.5%), butyl ammonium iodide (BAI, ≥99.5%), lead iodide (PbI2 , >99.99%), acetone (≥99.5%), anhydrous ethanol (AR), and FTO conductive glass. Experimental instruments: Fuji Group DMP-2800 ink jet printer, Dimatix DMC11610 (10pl) nozzle and cartridge, ultrasonic cleaner, drying oven, and Hande REVIEW series portable digital measuring instrument.

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2.2 Experimental Process Substrates also have an impact on crystal growth. After ultrasonic cleaning with deionized water, acetone and anhydrous ethanol in turn, dried at 120 °C in the oven for further use. Then BAI, MAI and PbI2 were dissolved in solvent mixed with DMF and DMSO at 60 °C, and configured into 1M as ink-jet printing ink. In this study, the key parameters were adjusted at room temperature firstly. The initial parameters were set at 35 µm spacing and 35 µm droplet size. The printing voltage (20 v, 25 v, 30 v, 35 v), ink droplet size (25 µm, 35 µm, 45 µm, 55 µm) and ink droplet spacing (25 µm, 35 µm, 45 µm, 55 µm) were adjusted uniformly to print, and the substrate temperature (30 °C, 40 °C, 50 °C, 60 °C) and annealing temperature (60 °C, 80 °C, 100 °C, 120 °C, 140 °C) were adjusted under the optimal parameters.

3 Result and Discussion The growth of perovskite crystals was controlled by a lot of factors jointly. It was related to the spread of the thin film on the substrate which ultimately affected the efficiency of devices. 3.1 Influence of Printing Voltage As showed in Fig. 1, ink volume increases with the increase of printing voltage, and meanwhile the perovskite crystals grow causing a small amount of accumulation. Ink droplet spread unevenly with holes and gaps. Through the conversion of printing voltage, piezoelectric ink jet produces the required pressure for the piezoelectric sheet mechanical deformation, so as to form droplets. The change of printing voltage can cause a slight difference in the droplet ejection. Ink droplet spreading and crystal growth are welldistributed, but the connection between them is poor at 25 V.

Fig. 1. Effect of different printing voltages on film-forming (a:15 V; b:20 V; c:25 V; d:30 V)

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3.2 Effect of Ink Drop Size As shown in Fig. 2, As the ink drops grew, the amount of ink per unit area increased, the crystal growth sped up, the crystal nucleus increased, and the disorder enhanced. We can observe that the crystal is obviously unconnected and accumulates. Droplet size affects the diffusion and evaporation of ink and droplet on the substrate surface. The film showed an observable homogeneous phase and was more complete when its diameter reached 35 µm.

Fig. 2. Effect diagram of ink droplet size on film formation(a:25 µm; b:35 µm; c:45 µm; d:55 µm)

3.3 Impact of Printing Spacing Printing spacing affects the wetting and spreading of ink droplets on the substrate and the thickness of the liquid film. The increase in spacing can be regarded as a decrease in the amount of ink per unit area. As shown in Fig. 3, As the printing spacing decreased, the amount of ink increased, the crystal volume increased, the apparent accumulation phenomenon appeared, the pinhole frequency increased, and the gap increased. While the spacing became larger, the ink per unit area decreased, and it starts getting suitable for crystal growth, but the connection between crystals is not obvious.

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Fig. 3. Effect of printing spacing on film formation (a:25 µm; b:35 µm; c:45 µm; d:55 µm)

3.4 Effect of Substrate Temperature With the increase of substrate temperature, we can observe that the solvent evaporation speeds up, crystal does not grow completely, the amount of ink has reduced, and an obvious phenomenon of reunion occurs. The crystal is too dense even overlapped as shown in Fig. 4. The film is most uniform and orderly at 40 °C, and the connections between crystals are close for which the conductive glass belongs to the thermal conductive body. When the substrate temperature increases, the droplet evaporation speeds up, resulting in the mass loss and the gradual decrease of the ink per unit area.

Fig. 4. Effect of substrate temperature on film formation (a:30 °C; b:40 °C; c:50 °C; d:60 °C)

3.5 Effect of Annealing Temperature As shown in Fig. 5, We can note that temperature increases as it speeds the crystal growth rate up. But, when the temperature is very high, the solvent volatilizes fast as

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well; Droplets are not fully spread, and the amount of ink per unit area is too large, resulting in excessive crystal density, and we can recognize even multilayer stacking. At 100 °C, the volatilization rate is appropriate, and a complete and continuous film is obtained. Ink-jet printing perovskite film has many solvents in the printing process. The volatilization of solvents in wet film is crucial, and the annealing temperature is closely related to volatilization rate and solution-to-dense crystal conversion.

Fig. 5. Effect of annealing temperature on film formation (a:60 °C; b:80 °C; c:100 °C; d:120 °C; e:140 °C)

The last film is as shown in the following Fig. 6. There are no gaps and faults in the film, with the moderate crystal volume and the tight crystal connection, showing uniform and no interface defects.

Fig. 6. Morphology of perovskite film printed by optimal parameters

4 Conclusion In the experimental conditions of this study, the influence of IJP printing parameters on the film growth and morphology was explored by changing the parameters, and a set of optimal parameters was obtained: The printing voltage of 35 V, ink droplet spacing of 45 µm, ink droplet size of 45 µm, substrate temperature of 40 °C, annealing

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temperature of 100 °C. Simultaneously, it was concluded that room temperature and external conditions had a certain impact on the growth and crystallization of perovskite thin film. In the future, the repeatability and stability of thin film preparation can be improved by reducing the influence of external conditions. Acknowledgement. We gratefully acknowledge support from BIGC Project and Institute of Advanced Ink, Beijing Institute of Graphic Communication.

References 1. Xing, G.C., et al.: Long-range balanced electron- and hole-transport lengths in organicinorganic CH3 NH3 PbI3 . Science 342, 344–347 (2013) 2. Im, J.-H., Lee, C.-R., Lee, J.-W., Park, S.-W., Park, N.-G.: 6.5% efficient perovskite quantumdot-sensitized solar cell. Nanoscale 3(10), 4088 (2011) 3. Burschka, J., et al.: Sequential deposition as a route to high-performance perovskite-sensitized solar cells. Nat. Int. Wkly. J. Sci. 499(7458), 316–319 (2013) 4. Liu, M., Johnston, M.B., Snaith, H.J.: Efficient planar heterojunction perovskite solar cells by vapour deposition. Nature 501(7467), 395–398 (2013) 5. Wei, Z., Chen, H., Yan, K., Yang, S.: Inkjet printing and instant chemical transformation of a CH3 NH3 PbI3 /nanocarbon electrode and interface for planar perovskite solar cells. Angewandte Chemie Int. Edn. 53(48), 13239–13243 (2014) 6. Li, S.-G., et al.: Inkjet printing of CH3 NH3 PbI3 on a mesoscopic TiO2 film for highly efficient perovskite solar cells. J. Mater. Chem. A 3(17), 9092–9097 (2015) 7. Hashmi, S.G., et al.: Air processed inkjet infiltrated carbon based printed perovskite solar cells with high stability and reproducibility. Adv. Mater. Technol. 2(1), 1600183 (2017) 8. Liang, C., et al.: One-step inkjet printed perovskite in air for efficient light harvesting. Solar RRL 2(2), 1700217 (2018) 9. Li, Z., et al.: Ink engineering of inkjet printing Perovskite. ACS Appl. Mater. Interfaces. 12, 39082–39091 (2020)

Application Research of 3D Printing Technology in Braille Chunmei Li(B) , Liang Zheng, and Ying Xiao Department of Graphic Communication, Shanghai Publishing and Printing College, Shanghai, China [email protected]

Abstract. Compared with traditional printing technologies, the greatest advantage of 3D printing technology is that the tridimensional characters can be printed. And the requirement of Braille printing fits this characteristic perfectly. In this paper the effects and costs of Braille printing plates which were manufactured by different 3D printing technologies were studied. Firstly, FDM, DLP and PolyJet technologies were used to print Braille plates. Then the precision and effect of different printing technologies were compared. Finally, a suitable method of printing braille can be selected according to the user’s requirements and budget. At the same time a new method to study Braille by 3D printing puzzle is approached. The 3D printing puzzles are convenient for the beginners to learn Braille writing and can be used repeatedly. This study will provide a new method for personalized printing of Braille, and can spell repeatedly to meet the requirements of environmental protection. Keywords: 3D printing · Braille · Recyclable

1 Introduction China has more blind people than any other country in the world. Braille is an important tool for the exchange of information between the visually impaired people and the outside world. Traditional printing methods of braille in the market mainly include die embossing, embossing, screen printing, stamping and so on. Nowadays 3D printing technology is well developed and the requirement of Braille printing fits the characteristics of 3D printing perfectly. 3D printing technology has brought great convenience to the blind people. For example, Braille maps [1], medical tablets [2], Braille-encoded Intraoral Films [3], keyboards, books, labels, etc. can be printed by 3D printer. Most researches have focused on how to print [4, 5] or recognize [6] or display [7, 8] Braille. But there is little attention has been paid to the difficulties of learning and writing Braille for the visually impaired people. In traditional handwritten braille, a pen with an iron point is used to make dots in the grooves of the braille plate. According to the rules of braille writing, a dent is left on the blind paper clamped between the plates. So that there are many defects of the traditional handwritten braille: (1) the rules of reading and writing are not consistent, © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 207–213, 2022. https://doi.org/10.1007/978-981-19-1673-1_32

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that is to say, the blind person should write on one side of the paper then read on the other side of the paper, so the corresponding conversion between reading and writing is required; (2) the order of reading and writing is not consistent, that is, when the order of writing should be from right to left, but the order of touch reading is from left to right; (3) Reading and writing cannot be done at the same time. This kind of braille design brings inconvenience to the users, especially to the people who just begin to learn Braille, and also caused a lot of troubles to the teacher. In this paper FDM, DLP and Polyjet technologies were used to print Braille plates in Chinese braille rules. Then the results of different printing technologies were compared. Finally, a suitable method of printing braille can be selected according to the user’s requirements and budget. At the same time a new design to study Braille by 3D printing puzzle is approached. The 3D printing puzzles are convenient for the beginners to learn how to write and read Braille. Moreover the puzzles can be used repeatedly to save resources and protect the environment.

2 Methods 2.1 Comparison of Different 3D Printing Technologies Based on the different printing principles there are several kinds of 3D printing technologies on the market. Considering of the material, cost, tactile sensing and accuracy, FDM (Fused Deposition Modeling), DLP(Digital Light Processing), Polyjet 3D Printing are used to print braille in this research. 2.1.1 Parameters of 3D Printing Braille The braille system was invented by Louis Braille in 1852. It uses six raised dots in a systematic arrangement with two columns of three dots, known as a braille cell. It is shown in Fig. 1. The dimensions of braille are not consistent from country to country. The diameter of the dot is 1.0 mm in Italian but it is 1.6 mm in America. The size of diameter of the dot determines the other parameters of the dot. The larger the diameter of the dot, the longer the intra-cell and inter-cell distance between cells. There are also large differences in the recommended height of the dots. Normally the height of the dot is 0.5 mm, however, it is 0.6–0.9 mm in France, 0.25 mm in Sweden [4].

Fig. 1. Six-dot cell

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The standard parameters of Chinese Braille [9] are shown in Table 1. The dimensions of braille printed in this paper are shown in Fig. 2. The height of the dot is 0.5 mm. Table 1. Standard parameters of Chinese Braille Parameters

Dimensions (mm)

Dot height

0.2–0.5

Diameter of dot

1–1.6

Dot spacing

2.2–2.8

Cell spacing

3.5–4.0

Row spacing

5–6

Fig. 2. The parameters of test Braille

2.1.2 Results of Different 3D Printing Methods The 3D model of Chinese Braille “serve the people” is designed in AutoCAD as shown in Fig. 3. The size of the base is 85.6 * 6.6 * 0.5 mm. The file of 3D model should be saved as STL or OBJ file firstly. Then the model will be sliced into a succession of thin layers by the program build-in different 3D printers. Finally a file including instructions that could be read by a specified 3D printer is generated.

Fig. 3. 3D model of Chinese Braille “serve the people” in AutoCAD

The parameters of three 3D printers are listed in Table 2. Layer thickness, materials, building time and the cost of the same model are compared in Table 2.

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DLP

PolyJet

3D Printer

3dpro X3

L120

Stratasys J750

Layer thickness

0.1 mm

0.05 mm

0.014 mm

Model material

PLA

Photosensitive resin

Vero™

Build time

6 min

14 min

21 min

Cost

0.1YUAN

0.3 YUAN

36 YUAN

Tactile sensing

Bad

Good

Excellent

The products that printed by different 3D printing technology are shown in Fig. 4. The original size error of dots which printed by FDM is very large and the surface is rough too. These dots are too bad to be recognized by touching. Although the braille of twice the size printed by FDM can be recognized by finger sensing, the top of the dot is not smooth yet. So the tactile sensing is still not good.

Fig. 4. Products printed by different 3D printing technology

The original size of braille printed by DLP is smooth and it has high dimensional accuracy and the tactile feeling is good. However it is bent out of shape because the base is too thin. Now the thickness of the base has been increased to 1mm with the cost of 1YUAN and it is still acceptable. The product printed by PolyJet is smooth, flat, accurate and the tactile feeling is excellent. But the cost is too high to be used as shown in Table 2. Based on the comparison of the products of different 3D printer the DLP technology is the best choice to print braille for now. 2.2 Repeatable 3D Braille Puzzles Base on the characteristics of Chinese syllabic structure, the phonetic and rhyme system is adopted in Chinese Braille. The initials should write first, and then the finals. Except for the special characters, the vowels are generally not appended. There are 21 initials and 34 finals. So generally a Chinese character without tone has two cells or three cells with one tone at most. Each cell can be divided into six parts with raised dot or not and the six parts can be used repeatedly. Then 3D printing puzzles are approached.

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2.2.1 Design the 3D Braille Puzzles Each cell is composed with six parts which has raised dot or not. The part with raised dot is designed as Fig. 5 and the part without raised dot is designed as Fig. 6. A cell box is designed as Fig. 7 and the allowance is taken into account.

Fig. 5. A part with raised dot

Fig. 6. A flat part

Fig. 7. A cell box

2.2.2 Printing the 3D Braille Puzzles Each Chinese character can be composed by three cells. Each cell can be spelled with six parts which have raised dot or not. So it is highly repeatable. When we teach the visually impaired people or the visually impaired people learn to write the 3D Braille puzzles are useful, convenient and repeated. Because the parts and the cells should be move by hands so the parts with original size are too small to be picked up. Finally the parts with four times the size are more comfortable to move and spell. The Chinese Braille “serve the people” is puzzled as Fig. 8.

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Fig. 8. The combination of braille puzzles

3 Conclusions In this paper 3 types of 3D printing technologies are used to print Braille. The size error of dots printed by FDM is very large and the surface is rough too. The product with thick base printed by DLP is smooth and has high dimensional accuracy and the tactile feeling is good. The product printed by PolyJet is smooth, flat, accurately and the tactile feeling is excellent but with high cost. In conclusion the DLP technology is the best choice to print Braille for now. Furthermore, 3D printing Braille puzzles are approached which are convenient for teaching and learning Braille writing then the defects of the traditional handwritten braille can be avoided. Especially in environmental protection, the puzzles can be used repeatedly. Acknowledgements. This study is funded by Key Lab of Intelligent and Green Flexographic Printing, which is belonged to State Administration of Press, Publication, Radio, Film and Television of the People’s Republic of China.

References 1. Holloway, L., Marriott, K., Butler, M., et al.: Accessible maps for the blind: comparing 3D printed models with tactile graphics. In: Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems, vol. 198 (2018) 2. Awad, A., Yao, A., Trenfield, S.J., et al.: 3D printed tablets (printlets) with Braille and moon patterns for visually impaired patients. Pharmaceutics 12, 172 (2020). https://doi.org/10.3390/ pharmaceutics12020172 3. Eleftheriadis, G.K., Fatouros, D.G.: Haptic evaluation of 3D-printed Braille-encoded intraoral films. Eur. J. Pharm. Sci. 157, 105605 (2021) 4. Loconsole, C., Leonardis, D., Bergamasco, M., Frisoli, A.: An experimental study on fuseddeposition-modeling technology as an alternative method for low-cost braille printing. In: Di Bucchianico, G., Kercher, P. (eds.) Advances in Design for Inclusion. Advances in Intelligent Systems and Computing, vol. 500. Springer, Cham (2016). https://doi.org/10.1007/978-3-31941962-6_18 5. Jo, W., Kim, D.H., Lee, J.S., Lee, H.J., Moon, M.-W.: 3D printed tactile pattern formation on paper with thermal reflow method. R. Soc. Chem. 4, 31764–31770 (2014)

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6. Samonte, M.J., Laurente, E.D., Magno, K.M., Perez, C.: Braille3D: using haptic and voice feedback for braille recognition and 3D printing for the blind. IOP Conf. Ser. Mater. Sci. Eng. 482(1), 012027 (2019). https://doi.org/10.1088/1757-899x/482/1/012027 7. Yang, W., Huang, J., Wang, R., Zhang, W., Liu, H., Xiao, J.: A survey on tactile displays for visually impaired people. IEEE Trans. Haptics 14(4), 712–721 (2021). https://doi.org/10.1109/ TOH.2021.3085915 8. Aryan, R.E., Doshi, S.: Refreshable Braille module using CAM actuated mechanism. In: International Conference on Design, Automation, and Control (ICDAC 2020) (2020). https://doi. org/10.1088/1757-899X/1123/1/012028 9. Chinese Braille. GB/T 15720-2008. National Standards of the People’s Republic of China (2008)

Creative Lock Design Research Based on 3D Printing Technology Yingmei Zhou(B) and Junwei Qiao Printing and Packaging Department, Shanghai Publishing and Printing College, Shanghai, China [email protected]

Abstract. This topic mainly uses the software SolidWorks for three-dimensional design modeling. In order to achieve the process of children’s safety lock with 3D printing technology, the article tried a creative product idea, scheme demonstration design, three-dimensional modeling, 3D printing material selection and printer use, etc., the application of 3D printing technology in product design is described. Keywords: 3D printing · Children’s safety lock · Scheme demonstration

1 Introduction 3D printing is a kind of rapid prototyping technology, which is based on digital model file, and uses adhesive materials such as plastic or metal powder to construct objects through layer by layer printing [1]. With the continuous breakthrough in the field of materials and the continuous improvement of digital control accuracy, at present, 3D printing technology has been widely used in industrial design, food processing, medical equipment, advanced manufacturing and other fields, with the characteristics of automatic, fast, accurate, and can be used to make complex structural parts products, which has the trend of gradually replacing the traditional processing and manufacturing [2]. At present, it is especially suitable for the first piece production in industrial design and creative product design [3]. Based on 3D printing technology, it is found that there are many hidden problems in lockers in modern families [4]. For example, when children are crawling and playing at home, they often open the refrigerator door and cabinet door without the attention of adults, which may cause accidental injury to children; when kids are opening and closing some cupboard doors and drawers, because of their lack of knowledge of things, they can often cause hand clamping and other injuries. Therefore, design and make the corresponding safety lock through 3D printing technology not only have the locking function but also achieve the purpose of anti-pinch, so as to effectively reduce the potential safety problems in the family.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 214–219, 2022. https://doi.org/10.1007/978-981-19-1673-1_33

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2 Design of the Project 2.1 Design Ideas The function of safety locks is to lock all household items that may cause potential safety hazards, and most of these household items are usually used, such as refrigerators, cabinets, drawers and so on. Therefore, in the design of creative locks, it is not complicated to operate, but to achieve the purpose of locking function and anti-clamping, and can be used conveniently, which is the important point of this design. There are many similar products on sale in the market, which are as follows: (1) Double button multifunctional lock This kind of multi-function lock is made of ABS material. The button is pasted on the furniture; the two buttons are connected through the connecting belt. If the door should be open, it needs to press hard and push backward to keep unlock (Fig. 1). In case of this situation, it is difficult to lock indeed and it is not practical.

Fig. 1. Double button multifunction lock

(2) Window safety lock The window safety lock adopts a sucker structure, which can be adsorbed on the glass of the window when necessary, or can be directly removed, so as to effectively prevent children from falling from the height (Fig. 2).

Fig. 2. Window safety lock

(3) Child safety card The function of the child safety door card is just opposite to the function of the safety lock. It is mainly used to prevent the occurrence of accidental hand clamping when children open or close doors or pull drawers (Fig. 3).

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Fig. 3. Child safety card

2.2 Scheme After compare the above several similar products, combined with the characteristics of 3D printing technology and materials, the following scheme is determined to be designed: (1) Adopt the appearance design of Cartoon Bear Considering the anti-pinch function of safety lockin appearance, the dimension can ensure the realization of anti-pinch function. (2) Similar structure with ring lock Bicycle lock is a common lock in daily life, which has the characteristics of simple structure and reliable locking, so it has been widely used in bicycles. This design uses the similar structure. The lock is composed of upper and lower shell, lock inner and lock button in Fig. 4.

Fig. 4. Outline design sketch

3 3D Modeling and Material (1) Preparation Three dimensional printing technology also known as “3D” printing, which make computers design the ideas to achieve the computer-aided products and form graphics. Generated 3D models can be recognized, read and checked. Through the printer control and drive system, the print material is stacked layer by layer, and the image on the computer will change into a real object finally. At present, there are many kinds of CAD software, such as SolidWorks, UG, Proengineer and so on.

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(2) Material Selection ABS, formerly known as acrylonitrile butadiene styrene copolymer, is the ancestor of household Fused Deposition Modelling (FDM) technology. Due to its low equipment development cost, side selection of consumables, and open source control technology, it is used in various industries. In terms of material properties, ABS plastic is quite easy to print from the perspective of hot end. No matter what kind of extruder is used, the material will be extruded smoothly without worrying about blockage or solidification. Therefore, when printing with ABS material, heating plate is essential. ABS is suitable for making articles, which is used in high temperature environment, such as car mobile phone rack, mobile phone protective case, toys, etc. The printed products have a wide range of applications. However, because ABS material has a certain pungent smell during printing, it is not suitable for occasions with high environmental requirements. PLA usually refers to polylactic acid ester, which is a biodegradable plastic [5]. When printing, there is smell, similar to candy. The glass transition temperature of PLA is also the biggest disadvantage of the material. It can be used only at a temperature of about 60 °C, so its application range is limited. Although PLA can print objects with high strength, it is slightly weaker than other plastics. If you drop or hit something, it will most likely produce a gap or damage instead of bouncing back. Thin places are easy to break before bending. It can not only be recycled, but also decay and disappear [6]. It is suitable for making boxes, gifts, models and prototype parts. In addition, the texture of this material is relatively fragile and is not suitable for frequent stressed occasions such as tool handles. Through the understanding and cognition of the above two materials, ABS material is more suitable for the production of children’s safety lock in the selection of 3D printing materials.

4 Modeling Process (1) Design of internal structure The hollow structure is designed in the entity to facilitate the installation and sliding of the lock tongue. In the sketch, the solid ring is drawn. The inner and outer rings have a wall thickness of 2.5 mm respectively, and a notch is left on one side of the

Fig. 5. Effect graphic

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outer ring for the lock tongue to push the button. Through the cutting tool in the software, the entity is cut to get the effect as shown in the figure below in Fig. 5. (2) Design of lock tongue The lock tongue is used for the locking function of the safety lock. The structure is designed as an open solid ring. On the outer side of the ring, a push button is designed to push the lock tongue in Fig. 6.

Fig. 6. Lock Tongue

(3) Design of fixed lock tongue A structure used to fix the lock tongue will prevent children from unlocking after the lock tongue slides in place. The design adopts a wedge-shaped structure, and the thickness direction of the long groove is inclined to one side. When the stop button is pushed, the button can move downward along the inclined direction to achieve the purpose of compressing the lock tongue in Figs. 7 and 8.

Fig. 7. Stop button

Fig. 8. Preview of stop button

(4) Modelling and Output According to the 3D modeling parts, the 3D effect of the safety lock is simulated by using the assembly function of the software, as shown in Fig. 9. The connecting belt and the fixed plate under the lock are glued on both ends of the locked object door or drawer with double-sided adhesive tape, one end of the connecting belt plate is put into the fixed plate, after inserting the lock, the lock tongue is slid, and the pressing button is pushed to complete the work. If you want to realize the anti-pinch function, you just need to remove the ring lock, align the “C” opening with the door or drawer, insert it and adjust the opening and closing degree of the lock tongue in Fig. 10.

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Fig. 9. Effect of simulated assembly

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Fig. 10. Output object

5 Conclusion Through the experiment of the simulate on 3D printing, the research gets the output real creative locker. Many tests focus on the support on the base. Due to the complex of the locker, the printing process uses the additional support to help printing, which causes the fail rate rise. So it is important to reduce the need of additional support. The second important point lies in each layer height, which influence the resolution of printing and time. Thinking of the requirements of customers, 0.1 mm each layer height is tested best. The third key point is the filling, density, which affects the material usage in the model. The higher the filling rate is, the stronger and heavier the model is. Generally, 10–30% filling rate is enough for the model with low strength requirement. High strength model is needed, and the filling rate can be higher. After trying to use 100% filling rate, it is found that the overall weight after assembly is too large, so the density of the finished product should be controlled at about 50%. Last, there are linear shape, honeycomb shape, triangle fill, different fill patterns will affect the strength of the final product, printing speed, material consumption. Different model parts are suitable for different filling patterns, such as honeycomb filling in the base part and linear filling in the latch slider. In a word, with the development of technology, there are still some problems such as price, personalization, material, and so on. Hope this study could push more business products into the market application. Acknowledgements. The paper is supported by Key Lab of Intelligent and Green Flexographic Printing.

References 1. Cai, Z.: Principle and Application of 3D Printing and Additive Manufacturing. National Defense Industry Press, Beijing (2017) 2. Yao, J.: Theory and Application of 3D Printing. Science Press, Beijing (2017) 3. Chen, P.: Product Innovation Design and Development Based on 3D Printing Technology. Electronic Industry Press, Beijing (2016) 4. Qi, X.: Printed Materials and Suitability. Printing Industry Press, Beijing (2008) 5. Oliver, B.: 3D Printers: A Beginner’s Guide, 1 January 2015 6. Endo, H., Umeno, T.: Study on the influence of temperature of extruder head on the strength of the FDM 3D printing mode. J. Robot. Mechatron. 29(4), 761–771 (2017)

Study on Exposure Characteristics of Ultraviolet (UV) Light-Emitting Diode (LED) for Platemaking of Flexopress Quanhui Tian1(B) , Yan Liu2 , and Huaiming Wang3 1 Department of Information and Intelligent Engineering, Shanghai Publishing and Printing

College, Shanghai 200093, China [email protected] 2 Department of Printing and Package Engineering, Shanghai Publishing and Printing College, Shanghai 200093, China 3 Technical Department, Shanghai Yingyao Laser Digital Edition Co., Ltd., Shanghai 200000, China

Abstract. Ultraviolet (UV) light-emitting diode (LED) curing technology offers lower operating costs, long lifetime, enhanced system capabilities due to being a solid-state device, and environmental benefits associated with safer workplace environments. UV LED curing technology has been adopted for coating processes in factory assembly lines throughout the world, especially ink curing of press. The paper studies the characteristics of UV-LED applied to the exposure unit and the influence on the quality of flexo-platemaking, through a large number of comparative experiments and data analysis, the correlation between of the energy of UV-LED exposure and the flatness of plate and forming of dot on the plate with exposure of UV-LED, the relationship of exposure time and support and relief on the plate substrate, and the influence on the characteristics of microhole and flat top branches of flexo-plate. Keywords: Ultraviolet light-emitting diode · Light source characteristics · Platemaking of flexopress · Flexopress

1 Introduction The printing and packaging industry are continually upgrading. The demands of customers keep continuously changing as well. The printers must standardize and optimize the various parameters involved in the print process to produce consistent results with good quality. The good quality of the plate is highly critical of flexopress. Exposure directly affects the quality of the flexopress plate and printing product ulteriorly. The traditional flexopress uses UV light source to solidify the flexible edition polymer resin to form the graphic and text part, and get the printing area after treatment [1–4]. In recent years, with the development of LED technology, specific ultraviolet light generated by UV-LED light sources causes flexible photosensitive resin to produce photochemical reaction, and forming printing units on the substrate surface became the © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 220–227, 2022. https://doi.org/10.1007/978-981-19-1673-1_34

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focus of research [5], especially in high-definition flexopress exposure technology [6– 10]. Most of the current research focuses on the research of UV-LED light source design and the corresponding light initiator agent, and the results continuously optimize the use of UV-LED light source [9]. However, UV-LED exposure is very different from the traditional UVA exposure for flexo-platemaking, and there is little research of the flexo-platemaking exposure with UV-LED. This paper used digital UV-LED exposure system for flexo-platemaking, and analyzes the base of plate, plate relief layer, branch forming, and plate flatness.

2 Method In order to test the characteristics of the UV-LED exposure, the model of the material tested is determined and operated using the method as shown in Fig. 1.

Fig. 1. The procedure of workflow

1) Engraving: design and make the test file, then engrave and measure the dot size on the carved black diaphragm to ensure that the dots image process as 1: 1 replication; 2) Back exposure test: expose the back of the plate through the LED lamp to obtain the appropriate base thickness, and record the back exposure time and other parameters;

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3) Main exposure: make the main exposure of the front of the plate through one quick exposure and multiple slow exposure, and record the times and speed of the exposure respectively; 4) Developing-process: completes the washing version, drying and post-treatment; 5) Measurement: records different dot shapes and measures the foot diameter and head diameter of dots with measuring instruments, as high-factor magnifier, FAG instrument; 6) Get parameters: determines the best parameters of exposure according to the printing requirements, and records the combined exposure method as the application value.

3 Result and Discussion 3.1 Main and Back Interval Exposure Time Test To test the impact of positive back exposure on the print quality, two different types of plate were used to compare the traditional UVA and UV-LED. The test uses a test gradient chart as Fig. 2.

Fig. 2. Test chart.

At the same time, test the influence of the positive back exposure on the outlets on the plate, and set different intervals respectively. Record the morphological changes of each step and analyze the influence of positive back exposure interval on the imaging quality.

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From the test dot form in Table 1, the two test types of plate, FTF45 and ESEQ35, use traditional UVA and UV-LED exposure, with 3 min, 120 min and no interval main back exposure intervals respectively. After the same post-processing method, the morphological characteristics of the dot found that more than 10% of the outlets did not change much; UVA traditional exposure printing, 1.2% or less is lost after 120 min, and the printing effect of UV-LED exposure is the same. Table 1. The test dot form

FTF45 Time dot 1.6%

UVA 3m

120m

UV-LED 0(at same time)

120m

2%

5%

10%

(continued)

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ESEQ45 Time dot 1.6%

UVA 3m

UV-LED 120m

0(at same time)

120m

2%

5%

10%

Table 2 is the effect analysis of 2%. Shown as Table 2, the traditional UVA 0.01 mm line is OK in exposure interval 3 min, but curved in exposure interval 120 min, 0.04mm line is OK. With UV-LED main back exposure at same time, 0.01 mm line is OK, while 0.01 mm line is missing, 0.04 mm line is curved and 0.06 mm is OK. For independent dot, traditional UVA exposure with 3 min interval, in the second row of test chart,16 can be seen, 9 is all missing.In the third row of test chart, 20 is visible, 16is all missing. In the second row of test chart, 16 is ok with exposure of 120 min interval, 9 is all dropped,and in the third row of test chart 64, 56 have been occasional dropped, 49 is partly dropped, 42 Most is dropped. UV-LED exposure main and back exposure at same time, in the second row of test chart, 16 is visible, 9 all dropped, in the third row of test chart, 36 is visible, 30 partially dropped, 25 is all dropped. With the exposure of 120 min interval, in the second row of

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test chart, 36 is ok, 30/25/20 is partial dropped, 16 is all dropped, the third row, All is dropped. Table 2. The effect analysis of 2%

Time

UVA 3m

UV-LED 120m

0

120m

2% dot

line

0.01mmok

0.01mm curl 0.04mm ok

0.01mmok

0.01mmmissing,0.0 4curl, 0.06mm ok

Independ ent Dot

the second row: 16 can be seen, 9 is all missing. the third row: 20 is visible, 16 is all missing.

the second row: 16 is ok ,9 is all dropped, the third row:64,56 have been occasional dropped, 49 is partly dropped, 42 Most is dropped. points.

the second row: 16 is visible, 9 all dropped the third row: 36 is visible, 30 partial drop, 25 is all dropped

The second row: 36 is ok, 30 / 25 / 20 is partial dropped, 16 is all dropped, The third row: All is dropped.

3.2 Dot Forming Comparison Analysis the state of dot formation with different exposure methods, Table 3 shows the area rate of different outlets, the dot form formed by traditional UVA exposure and UV-LED exposure.

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dot 15-4.56%

UVA

UV-LED

20-7.36%

60-45%

85-77%

95-92%

4 Conclusion In the same energy exposure, the longer the interval of main and back exposure, the more not conducive to small dot standing, showing a drop, bending or small diameter. UV-LED exposure formation is flat dot, the traditional UVA is a round head dot, two kinds of dot shape have advantages in printing, but the micro influence of UV-LED exposure on dot foot support has not been valued and developed. After the combination of UV-LED exposure, formed the rapid exposure of UV-LED, due to the slow reaction of material head, exposure, the dot slope has expanded, resulting in the foot support become fat and strong. Therefore, by adjusting the exposure speed of the UV-LED, you can effectively change the sufficient size of the dot, and the dot support form also changes accordingly.

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Acknowledgments. This study is funded by Green Platemaking and Standardization laboratory for Flexographic Printing (ZBKT201904).

References 1. Hu, C.: UV-LED research and design of lighting integrated lighting. Light. Eng. 32(2), 58–62 (2021) 2. Pang, Y., Zhao, L., Gao, M., Zou, Y.: Synthesis and performance of new photoinitiators for UV-LED sources. Imaging Sci. Photochem. 37(5), 438–444 (2019) 3. Wei, B., Lin, L.: Application status and trend of UV-LED in optical curing field. China High-Tech Enterp. (11), 92–93 (2017) 4. Xue, P., Xiansheng, C., Jingwen, C., et al.: Component study of LED photocuring ink and selection of suitable light sources. Screen Print. (1), 31–33 (2016) 5. Mahajan, M.P., Bandyopadhyay, S.: Characterization and optimization of color attributes chroma (C*) and lightness (L*) in offset lithography halftone print on packaging boards. Color Res. Appl. 45, 325–335 (2020) 6. Yushan, L., Wenyan, S.: Fullint flexible flat top outlets technical solution. CIFlexo (12), 33–38 (2018) 7. Song, Z.: Flat top dot technology in soft packaging high-definition soft printing application exploration. CIFlexo Silk Ai Soft Print. (12), 25–39 (2017) 8. Li, S.: Study on the influence of platform UV-LED exposure parameters on dot concave (Cupping). CIFlexo (10), 36–40 (2017) 9. Chen, Y.: Pure UVA-LED. Print. Mag. (01), 28–33 (2017) 10. He, H.: Effect of the interval between back and main exposure on the revision results. CIFlexo (12), 35–40 (2018)

Effect of Paper Properties on Ink Transfer Properties Yongjian Wu, Beiqing Huang(B) , Xianfu Wei, and Hui Wang School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected] Abstract. The ink transfer rate has an important influence on the printing quality. The primary aim of the printing process is always to achieve a high ink transfer rate. This paper used a printability tester to test three different types of paper: coated paper, offset paper, and newsprint, and adopted an approximate method to calculate the ink transfer equation to test the absorbency, surface smoothness, and elasticity of the papers. Furthermore, we developed a linear regression model based on the measured values. Analyzed and explored the influence of paper properties on the parameters of the ink transfer equation. The experimental results show that the maximum ink transfer rate of a newsprint paper is higher than that of an offset paper and coated paper under the same ink and printing conditions, with the optimal ink supply to the coated paper being the smallest. The ink absorption and smoothness of a paper were found to significantly influence the ink transfer parameters. Keywords: Ink transfer equation · Ink transfer rate · Paper performance test

1 Introduction Ink transfer is the process of transferring the ink on the printing plate to the substrate. Effective ink transfer is the key to printing high-quality prints. An in-depth discussion of the law of ink transfer can not only ensure the stability, uniformity, and appropriate amount of ink transfer, but also improve the ink transfer rate by controlling and adjusting printing conditions to obtain the best printing effects with the smallest possible quantity of ink, which could effectively prevent the excessive consumption of ink and save costs [1]. The ink transfer rate directly affects the reproduction effect of the image, the clarity of the printed material, and the saturation of the ink color. During the printing process, it is always aimed that a high ink transfer rate is achieved, however, the ink transfer process is very complicated. There are many factors affecting the rate of ink transfer, such as ink performance, paper performance, type of printing machine, and environmental factors, etc., with varying degrees of impact. During the process of ink transfer, paper properties have a great influence on the ink transfer rate. In this study, three different types of paper were used in ink transfer experiments. The WF ink transfer equations of the various papers were established by approximation method, and the various papers were tested, and a performance parameter to study the influence of the performance of the different papers on the three parameters b, f  , and k of the ink transfer equation was investigated. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 228–235, 2022. https://doi.org/10.1007/978-981-19-1673-1_35

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2 Experiment 2.1 Experimental Equipment and Materials AIC2–5 printability tester, Three-roll grinding machine, Paper KN ink tester, Bekk smoothness tester, squeegee, ink injector, Self-made Laboratory UV offset printing ink, coated paper 100 g/m2 , coated paper 120 g/m2 , offset paper 80 g/m2 , offset paper 90 g/m2 , newsprint 60 g/m2 , and newsprint 80 g/m2 . 2.2 Experimental Method Ink Transfer. Under a temperature of 25 °C and a humidity of 55%, we set the printing speed to 0.2 m/s, the printing pressure to 625 N/m, changed the ink supply, and use the printing suitability meter to test the offset and coated papers respectively. The newsprint is proofed, and the ink transfer amount is calculated using the weight difference method. Ink Absorption. Take a paper sample and use a spectrophotometer to measure the reflection factor R0 before applying the absorbent ink to the surface of the sample. The sample under test should be lined with several layers of the same sample until it becomes opaque. Evenly smear the absorbent ink on the sample and wait for 2 min. Wipe off the unabsorbed ink with ink-wiping paper, to leave a uniform ink mark on the sample. Subsequently, a spectrophotometer is used to measure the reflection factor R1 at the original detection point, (R0–R1)/R0 is the absorbency value of the ink. Paper Smoothness. Take a paper sample and place the sample between the upper and lower pressure plates of the Buick smoothness meter, lower the upper-pressure plate, select the appropriate gear according to the paper, press the start button, and the vacuum pump will automatically start. When there is no change in the smoothness of the display, the test ends, and the smoothness value of the paper is noted.

2.3 Calculation Method of Ink Transfer Rate The calculation of the ink transfer rate adopts the differential weight method. x=

m1 − m . s

(1)

y=

m1 − m2 s

(2)

f =

m1 − m2 m1 − m

(3)

where m is the net mass of the printing disc;m1 is the mass of the printing disc after the distribution of the ink;m2 is the mass of the printing disc after printing; s. is the area of the printed image and text. Next, e calculate the ink transfer rate f according to formulas (1) and (2).

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2.4 Ink Transfer Equation Fetsko and Walker proposed the W.F ink transfer equation (Fetsko-Walker), which is a mathematical model for studying the process of ink transfer [2].        x x (4) y = 1 − e−kx {b 1 − e− b + f  x − b 1 − e− b In the formula above, y is the amount of ink transferred, x is the ink supply by the printing plate, parameter b is the maximum amount of ink that may be filled in the depression on the surface of the paper at the moment of printing, parameter f  is the split rate of free ink, and parameter k is the proportional coefficient, under the condition of a certain amount of printing plate ink to determine the area of the paper surface in contact with the ink per unit printing area.

3 Consequence and Analysis 3.1 Analysis of Ink Transfer Experiment Approximate Method

y/(g.m-2)

Using three different papers, the ink type and printing conditions remain unchanged, the ink supply is changed, and ten replications of the experiments are performed on each paper. The amount of ink transferred to the paper is weighed to obtain the ink transfer volume curve of each paper, as shown in Fig. 1.

20 18 16 14 12 10 8 6 4 2 0

Ink transfer curve Ink transfer volume curve of coated paper Offset paper ink transfer curve Newsprint ink transfer curve 0

10

20 -2) x/(g.m

30

40

Fig. 1. Ink transfer curve of different types of paper

Figure 1 shows that the amount of ink transfer increases with an increase in the amount of ink supply. When the amount of ink supply is relatively small, the amount of ink transfer increases rapidly. When the ink supply is sufficient, the amount of transferred ink basically increases in a linear relationship with the amount of ink on the printing plate [3]. In combination with the ink transfer equation, when the ink supply is large

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enough, sine b and k in the ink transfer equation are both finite values, the e−kx and e−x/b items in the ink transfer equation can be ignored to obtain a simplified linearized ink transfer equation as follows:   (5) y =f+b 1−f The approximation method is used to obtain the b, f , and k values in the ink transfer equations for different papers, and corresponding ink transfer equations for the three types of papers are established as shown below: Coated paper:        x x (6) y = 1 − e−5.57x 2.56 1 − e− 2.56 + 0.41 x − 2.56 1 − e− 2.56 Offset paper:        x x y = 1 − e−0.84 5.56 1 − e− 5.56 + 0.29 x − 5.56 1 − e− 5.56

(7)

Newsprint:        x x y = 1 − e−0.37x 6.81 1 − e− 6.81 + 0.32 x − 6.81 1 − e− 6.81

(8)

The ink transfer rate is calculated and the ink supply is plotted on the x-axis to draw the relationship curve between the ink transfer rate and the ink supply, as shown in Fig. 2.

Ink transfer rate curve

0.8 0.7 0.6

Ink transfer rate of coated paper Offset paper ink transfer rate Newsprint ink transfer rate

f/㸣

0.5 0.4 0.3 0.2 0.1 0

0

10

20

x/(g.m-2)

30

40

Fig. 2. Ink transfer rate curves of different paper types

Figure 2 shows that the ink transfer rates of the three papers all increased first, then decreased, and subsequently remained stable. The coated paper had the highest initial

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ink transfer rate, followed by the offset paper and lastly the newsprint paper, however, the maximum ink transfer rate of the coated paper is close to that of the offset paper, but the newsprint has a slightly higher ink transfer rate. For the same paper, the higher the ink transfer rate, the better the quality of the printed material. To find the maximum ink transfer rate of the paper and the corresponding ink supply, it is paramount to print high-quality prints. Figure 2 indicates that the ink supply to the coated paper is the lowest, followed by the offset paper, with the newsprint having the highest ink supply. This indicates that newsprint needs more ink supply to get the best printing effects. The best printing effect can be exerted with very little ink supply. 3.2 Influence of Paper Properties on Ink Transfer Parameters Based on the ink supply and ink transfer volume curve, and by using the approximation method, the values of the parameters b, f , and k of the ink transfer equation corresponding to the three different types of paper are calculated. Using the same experimental method to test the three different brands of coated paper, offset paper, and the newsprint again, the values of b, f , and k are calculated to list the measured paper properties as depicted in Table 1. Table 1. The performance parameters, b, f , and k values of different types of paper Type of paper

Smoothness/s

Ink absorption %

b

f

k

Coated paper 1

1056

16

2.56

0.41

5.57

Offset paper 1

457

51

5.56

0.38

2.84

58

58

6.81

0.32

0.87

Coated paper 2

619

15

3.72

0.39

3.57

Offset paper 2

51

52

6.09

0.42

0.84

Newsprint2

47

52

6.14

0.39

1.14

Newsprint 1

Table 1 indicates that the greater the smoothness of the paper, the less ink the surface of the paper accepts at the moment of printing, the smaller the b value, and vice versa, the larger the b value [4]. Also, the ink absorbency of the paper has an effect on the b value. Paper with a good ink absorbency has a larger b value. The f  value of the various f papers differs slightly and the f  value is not significantly affected by the performance of the paper. The k value is significantly affected by the smoothness of the printing, the greater the smoothness of printing, the greater the k value. However, the smoothness of newsprint 2 in Table 1 is slightly higher than that of newsprint 1 and offset 2, which are similar in smoothness. This is because newsprint 2 has better elasticity, and the smoothness of newsprint 2 is higher when printed under the effect of printing pressure than the smoothness when measured.

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Input the data obtained into SPSS software, take paper smoothness, ink absorbability as the independent variables, respectively, and set x 1 , x 2 , b, f  , k as the dependent variables to perform a multiple linear regression analysis to obtain the detailed analysis of paper performance on variables b, f  , and k. The first is the regression analysis of the b value, the test results showed that the correlation coefficient (R2 ) value is 0.965, the model interpretation degree is very high. The Durbin-Watson value is used to detect the autocorrelation between the independent variables. Generally speaking, the closer the value is to 2, the better. The Durbin-Watson value obtained is 1.133, showing that there is no significant correlation between the two independent variables. Further analysis may be performed. The analysis results are shown in Table 2. Table 2. Linear regression analysis of paper properties on b values Paper parameters Constant Smoothness Ink absorption

Unnormalized coefficient B

Significance

4.214

0.015

−0.002

0.054

0.043

0.059

The linear regression model of the effect of paper properties on b value is obtained as: b = −0.002x1 + 0.043x2 + 4.214

(9)

Significance indicates the degree of influence of the independent variable on the dependent variable; 50%, the cushioning coefficient of the porous materials with weight of 100 g/m2 is smallest. Then the porous materials have the superior cushioning performance at this time. The cushioning coefficient is 1.17. With the increase of the core paper’s weight, the minimum cushioning coefficient of the cushioning materials increases. The core paper’s weight is proportional to the minimum cushioning coefficient. 3.2 Impact of the Side Length of the Diamond on the Static Cushioning Performance There are many kinds of side length for this experiment. However, due to the limitation of experimental time, we only choose 5 mm, 11 mm, 13 mm and 15 mm in this experiment when θ = 60º. Then the stress-strain curves are gained in Fig. 6.

Fig. 6. The stress-strain curve of side length’s effect on stress

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Figure 6 shows that the curve shape of the porous materials with different side length has the same tendency. But the yield value is different. The yield values are 0.46 MPa, 0.22 MPa, 0.14 MPa and 0.09 MPa respectively. When L = 15 mm, the yield value of the materials is the minimum. The yield value increases with the decrease of the side length of the diamond, and the rigidity of the materials increases. The static cushioning coefficient-strain (C-ε) curves are shown in Fig. 7 according to the results in Fig. 6.

Fig. 7. The cushioning coefficient-strain curve of the cushioning materials with different side length of the diamond

When ε ≤ 40%, the cushioning coefficient of the porous materials with the side length of 13 mm is smallest in Fig. 7. It shows that its absorption is more, and its cushioning performance is best. When ε > 40%, the cushioning coefficient of the materials with the side length of 15 mm is the smallest. Its cushioning performance is best. With the increase of side length, the minimum cushioning coefficient of the cushioning material decreases. 3.3 Impact of the Intersection Angle of the Diamond on the Static Cushioning Performance When L = 11 mm, the intersection angle of the diamond take respectively 30º, 60º and 90º in the experiment. Finally the stress-strain curves are shown in Fig. 8.

Fig. 8. The stress-strain curve of intersection angle’s effect on stress

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The curve shape of porous materials with different intersection angle of the diamond has almost the same tendency in Fig. 8. But the yield value is different. The yield values are 0.26 MPa, 0.12 MPa and 0.13 MPa respectively. When θ = 60º, the yield value of the materials is the minimum. The yield value increases with the decrease of θ. The static cushioning coefficient-strain curve is drawn according to the test results in Fig. 8, which is shown in Fig. 9.

Fig. 9. The cushioning coefficient-strain curve of the cushioning materials with different intersection angle of the diamond

When ε = 30%, three curves coincide briefly in Fig. 9. At this moment the cushioning performance is same. When ε > 30% and ε = 10%, the cushioning coefficient of the porous materials with the intersection angle of 30° is biggest and the other two curves coincide. So the porous materials with the intersection angle of 60° and 90° have the best cushioning performance comparing with 30°. When 10% < ε < 30%, the cushioning coefficient of the porous materials with the intersection angle of 90° is lowest. So its absorption is more. Its cushioning performance is best. When ε < 10% and the intersection angle is 60°, its cushioning coefficient is smallest. So its cushioning performance is best. The cushioning coefficient is 1.61. The intersection angle is not proportional to the cushioning coefficient.

4 Conclusions Some conclusions are drawn from these discussions. The static cushioning performance varies with structural parameters of the materials. The intersection angle is not proportional to the minimum cushioning coefficient of the cushioning materials. When intersection angle is 60°, the minimum cushioning coefficient of the samples is the least comparing with 30°and 90°. So its cushioning performance was the best. With the increase of the weight of the core paper, the minimum cushioning coefficient of the cushioning materials increases. The side length of the diamond is inversely proportional to the minimum cushioning coefficient of the cushioning materials. Acknowledgement. This work was supported by the Research Project of Beijing Institute of Graphic and Communication (No. Ea201002 and Eb202201).

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References 1. Wang, Z., Peng, G.: Ecological Design of Military Logistics Packaging System. Eng. Packing 35(9), 140–146 (2014) 2. Tian, J., Qian, Y.: Finite element modeling and dynamic performance study of a packaging. Packag. Food Mach. 32(4), 1–4 (2014) 3. Ding, Y., Qian, Y.: Simulation analysis of dynamic cushioning characteristics of integral packaging based on Ansys workbench. Packag. Food Mach. 35(11), 18–22 (2014) 4. Zhong, C., Yang, Y., Zhou, L.: Research status and prospect of e-commerce logistics packaging. J. Packag. 12(05), 27–34 (2020) 5. Xi, B.: Characteristic analysis of porous materials. Sci. Technol. Inf. (Sci. Teach. Res.) 23, 316+329 (2007) 6. Li, Q., Chen, L., Shen, J., Wang, J.: The application and development of porous materials. Mater. Rep. 6, 10–13 (1995) 7. Yang, Y., Wang, Z.: Research progress on cushioning packaging materials and their properties. Packag. Eng. 4, 96–99+105 (2002) 8. Measures for the management of mail express packaging. Gazette of the State Council of the People’s Republic of China, vol. 12, pp. 22–25 (2021) 9. Wang, F., Bian, B., Yang, C., Chen, H., Zhang, X.: Study of paper cushion and its molding process. Packag. Eng. 233(19), 67–71 (2012) 10. Zheng, X., Cao, G.: Present situation and thinking of packaging reduction. J. Beijing Inst. Printing 20(02), 19–25 (2012) 11. Tsiapouris, A., Linke, L.: Water vapor sorption determination of starch based porous packaging materials. Starch-Stärke 52, 2–3 (2000)

Inactivation Efficacy and Applications of Gliding Arc Discharge Plasma in Fresh Pork Meat Preservation Yidan Wang1 , Xueying Wang1 , Lubin Cui1 , Yunjin Sun1,2 , Jun Wu1(B) , and Fuqiang Qiao3(B) 1 Beijing Laboratory of Food Quality and Safety, Food Science and Engineering College,

Beijing University of Agriculture, Beijing, China [email protected] 2 Plasma Engineering Center, Capital Agricultural Product Safety Industrial Technology Institute, Beijing University of Agriculture, Beijing, China 3 School-Run Industry Office, Beijing University of Agriculture, Beijing, China [email protected]

Abstract. This study aimed to explore an inactivation efficacy of microorganisms on fresh pork meat treated by gliding arc discharge plasma. By using Escherichia coli (E. coli) as a model microorganism, bactericidal efficacy was evaluated and indicated that more than 6.0 log (CFU·mL−1 ) values reduction was achieved within plasma exposure duration of 300 s. In addition, the concentration of extracellular protein of E. coli was increased significantly under gliding arc discharge plasma treatment, in comparison with the increasing concentration of reactive oxygen species passed through infiltration and diffusion of bacterial membrane, which provided evidence that the inactivation mechanism was attributed to the combination effect of membrane integrity and synergistic oxidation in vivo. The fresh pork meat pre-coated with E. coli was used to further verified the sterile effect of gliding arc discharge plasma treatment. The results indicated that surface clearance and preservation of the pre-coated meat was much better than control ones, which showed a potential application of gliding arc discharge plasma in extending shield life and improving the health level of fresh pork meat product. Keywords: Gliding arc discharge · Escherichia coli · Inactivation efficacy · Pork preservation

1 Introduction Fresh pork meat rich in a large amount of water and sufficient nutrients, is easy to be polluted by all kinds of food-borne microorganisms, especially in the process of production and sales, which both significantly decreases the food quality and safety and limits the development of fresh pork meat [1]. Therefore, how to effectively solve the technical safety and health problems of fresh pork meat in storage and preservation is the key point to its application and development. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 291–300, 2022. https://doi.org/10.1007/978-981-19-1673-1_44

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Gliding arc discharge plasma technology is a relatively novel non thermal sterilization technology in recent years. Compared with sterilization modes (such as thermal and ultra-high-pressure sterilization), it has more advantages in operation flexibility, processing ability, and energy utilization [2]. At the same time, it has a high sterilization efficient of viruses and bacteria whether from the surface of samples or environment [3]. To a certain extent, it has potential applications in the sterilization of fresh food to replace the traditional sterilization methods. At the same time, different from the results of cell wall destruction, RNA and DNA decomposition and protein solidification caused by various charged particles [4], active free radicals [5] and ultraviolet photons [6] from plasma gas could pose a detrimental and synergistic effect against all kinds of bacteria. Until now, most of the related researchers have focused on the preliminary exploration applications of atmospheric plasma technology. However, the inactivation kinetics of atmospheric cold plasma sterilization is not fully known. To supplement the inactivation mechanism and theory of atmospheric pressure discharge plasma, in this study, E. coli was used as a model microorganism to explore the inactivation metabolism of gliding arc discharge on foodborne pathogenic bacteria and its application in cold fresh meat preservation.

2 Materials and Methods 2.1 Experimental Set-Up The plasma discharge processor is mainly composed of high-voltage power supply (Voltage of 50.0 kV and frequency of 10 kHz), pilot lamp, air compressor, reaction chamber, and gas flow controller as shown in Fig. 1(a). Pressured and filtered air is passed through the ceramic chamber. A sterile glass slide coated with inoculated bacteria pellet or pork meat sample is located on the object table under the lower end of the ceramic reactor port, as shown in Fig. 1(b). Once the gas passes through the reactor, it is ionized by gliding arc discharge between the two copper electrodes to form a plasma plume. The processing parameters of plasma discharge include power input, gas flow rate, and exposure time.

Fig. 1. Atmospheric plasma discharge equipment in the study. (a) experimental set-up for gliding arc discharge experiments. (b) structural model of gliding arc discharge generation and treatment system

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2.2 Inoculation and Treatment of Bacterial Suspensions E. coli (ATCC 8099), provided by the China Center of Industrial Culture Collection were inoculated and cultured in a thermostatic oscillator at 37 °C and 180 r·min−1 for 12–16 h. Then, the bacterial pellet was obtained by centrifuging the E. coli suspensions in 5000 r·min−1 for 10 min. The precipitated bacterial pellet was homogeneously coated onto the surface of a sterile glass slide with a coating rod. Finally, the prepared slides were treated under atmospheric gliding arc discharge of 300 W, 400 W, and 500 W, and exposure duration time of 30 s, 60 s, 120 s, 180 s, and 300 s, respectively. The discharge distance between the sample and discharge plasma was set as 20 mm with a gas flow of 40 L·min−1 . 2.3 Microbiological Analysis of Treated Pork Meat The pork meat (No. 5 meat processing plant, Beijing, China) was irradiated by ultraviolet light for 15min, and was cut into pork pieces (5 g) in Vertical Flow Clean Bench. The 1 mL of activated bacteria solution (3–4 log CFU·mL−1 ) was inoculated on the surface of each pork meat piece, which treated under atmospheric gliding arc discharge of 500 W and exposure duration time of 0 s, 10 s, 30 s, and 60 s. The bacterial counts were monitored overtime at predetermined storage time intervals (0, 1, 2, 3, 4, and 5 d). 2.4 Determination of Extracellular Protein Concentration In the post-treatment process, all the bacterial pellet was washed with Phosphate Buffer Saline Buffer (PBS) and re-centrifuged in 10000 r·min−1 for 10 min. The extracellular protein concentration of the supernatant was measured by a visible light spectrophotometer (TU-1810, Beijing Purkinje General Instrument co. LTD. China) at the absorbance of 595 nm according to Coomassie bright blue method [7]. 2.5 Reactive Oxygen Species Measurement According to the method of active oxygen detection kits (Beyotime, Co. China), the treated E. coli samples were collected by serum-free culture medium into the centrifugal tube and were placed in the diluted 2’,7’-Dichlorofluorescin diacetate (DCFH-DA) (10 µmol·L−1 ). The fluorescence intensity of DCFH-DA-stained bacterial suspension was measured by a fluorescence spectrophotometer (F93, Shanghai Lengguang Tech., China), the exciting wavelength was 488 nm and the emission wavelength was 525 nm. 2.6 Surface Morphology Analysis Bacterial morphology was examined by scanning electron microscopy (SEM) [8]. E. coli samples treated with/without gliding arc discharge were fixed using 2–5% glutaraldehyde at 4 °C for 24 h and dehydrated in ethanol series (25, 50, 70 and 95%) for 15 min at each treatment. Finally, the samples were sprayed with gold and observed with Scanning Electron Microscope (SEM, JSM-6700f, Japanese electronics, Japan) at 30000 magnifications.

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2.7 Membrane Integrity Analysis Annexin V-FITC apoptosis kit was used for membrane integrity measurement (Shanghai Yeasen limited Co., China). The treated and untreated samples were centrifuged at 4000 r·min−1 for 3 min, then washed with PBS solution three times to discard the supernatant and stained with 20 µL binding buffer, 10 µL of Propidium Iodide (PI), and 5 µL of Annexin V (Yeasen, Shanghai, China) in a dark environment, respectively and observed under Laser Scanning Confocal Microscope (LSCM, FV1000MPE, Olympus, Japan) [9]. 2.8 Analysis of Pork Quality Attributes The total volatile basic nitrogen (TVB-N) content and redness (a*) were used to judge the freshness of pork samples with time after gliding arc discharge treatment. The TVB-N was monitored over time at predetermined time intervals (0, 1, 2, 3, 4, and 5 d) by Semi micro Kjeldahl method [10]. The redness was monitored over time at predetermined time intervals (0, 1, 2, 3, 4, and 5 d) by Chroma Meter (CM-700d, Konica Minolta Co., Ltd., Tokyo, Japan). 2.9 Statistical Analysis All experiments were repeated three times and all results are expressed as mean values ± standard deviation (SD). Data were evaluated by one-way analysis of variance (ANOVA) with the Tukey HSD post-hoc test for comparisons between groups using Statistical Package for the Social Sciences ver. 19 software (SPSS Inc, Chicago, IL). Probability values of less than 5% were significant and all data are plotted by OriginPro 9.1 (OriginLab Inc, USA).

3 Results and Discussion 3.1 Bactericidal Effects of Gliding Arc Discharge Under Different Discharge Powers Before the treatment process of gliding arc discharge plasma exposures, the initial concentration of E. coli was calculated to be 6.0 log values and decreased in different degrees with treatment time, as shown in Fig. 2(a). At low discharge power of 300 W, the reduction number of E. coli colonies was small, reaching 3.0 log values at 300 s. With the increment of discharge power up to 500 W, the colony number decreased significantly, reaching 6.0 log value in 120 s, and did not vary with the extension of treatment time. In addition, the number of colonies on the surface of pork samples treated by gliding arc discharge plasma increased with the storage time, as shown in Fig. 2(b). For the untreated group, the number of colonies on the surface of pork increased from 3.70 log to 7.49 log within 5 days, which could be identified as rotten cold meat [11]. On the contrary, the growth of colony number on the surface of samples in the treated group was inhibited. Thus, it can be inferred that gliding arc discharge plasma has higher antibacterial efficacy and can be a potential alternative to nonthermally inactivate the food-borne pathogens existing whether on the surface of fresh produce or circulation environment [12–14].

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Fig. 2. (a)Populations of E. coli inactivated by gliding arc discharge plasma at different powers. dot and  (300 W), dash and ◯ (400 W), solid and  (500 W). (b) The number of colonies on the surface of pork samples treated by gliding arc discharge plasma. dot and  (0 s), dash and ◯ (10 s), solid and  (30 s), dash dot and ▽ (60 s)

3.2 Extracellular Protein Concentration and Measurements of ROS of E. coli Under Gliding Arc Discharge Plasma Treatment With the extension of treatment time, the extracellular protein of the cell membrane was firstly oxidized or etched by reactive radicals with the corresponding concentration increased from the original 34.2 µg·mL−1 to 89.7 µg·mL−1 , as shown in Fig. 3(a). With lower discharge power of 300 W, the concentration of extracellular protein varied linearly with the discharge time until it reached a constant maximum level. When the discharge power increased to 500 W, the concentration of extracellular protein reached its maximum within 120 s.

Fig. 3. (a) Oxidized effect of glide arc discharge power on extracellular protein concentration of E. coli in different treatment times. (b) Effect of glide arc discharge power on ROS concentration of E. coli in different treatment times. dot and  (300 W), dash and ◯ (400 W), solid and  (500 W).

A high-intensity level of DCF-DA fluorescence was also observed in E. coli treated with gliding arc discharge, indicating that it had a higher level of ROS concentration than those of control ones, as shown in Fig. 3(b). In general, ROS generated by plasma discharge can penetrate the membrane, trigger redox-signaling pathways, and lead to

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apoptosis. Ahn et al. [15] found that the ROS and RNS can trigger signaling pathways and promote mitochondrial perturbation. Dezest et al. [16] investigated that the oxidative modification of E. coli inactivated by atmospheric pressure plasma exposure and found that oxidative damage and protein oxidation during plasma treatment are the essential factors leading to cell death. 3.3 Surface Morphology and Membrane Integrity of E. Coli Under Gliding Arc Discharge Treatment The morphology changes of E. coli before and after different plasma treatment durations were observed by SEM as shown in Fig. 4. Compared with the control group as shown in Fig. 4(a), the surface of E. coli membrane treated by plasma discharge was damaged in varying degrees, and the degree of damage was different with different treatment time. After air treatment for 300 s min, as shown in Fig. 4(c), the depression and shrinkage of the cell surface deepened, the cilia and flagella structure disappeared, and even lost the original shape of the cell.

Fig. 4. Surface morphology changes of E. coli under gliding arc discharge treatment: no treated samples (a) and treated samples for 60 s (b) and 300 s (c)

Based on the variation trend of extracellular protein concentration results as shown in Fig. 3(a), the variation of surface morphology of E. coli inactivated by gliding arc discharge plasma further verified the oxidized effects and posed certain damage to the cell membrane or lipid oxidation [17]. Combined with experimental results of the membrane morphology, it could be speculated that the inactivation kinetics of E. coli induced by gliding arc discharge might be through a membrane-mediated apoptosis pathway [18, 19]. Therefore, it can be inferred that the active components of plasma have strong oxidation on cell membrane, destroy the integrity and permeability of cell membrane, and inactivate bacteria. Annexin V-FITC/PI double-stained LSCM images of samples under gliding arc discharge treatment at time intervals of 60 s and 180 s of control, as shown in Fig. 5. Before the plasma treatment, the black ground in the fluorescence field in Fig. 5 (a) and 5 (b) and average contribution of cell bodies in the bright field in Fig. 5 (c) verified the good membrane integrity. After gliding arc discharge exposure for 60 s, the cells showed early apoptosis. This was further enhanced by prolonging the treatment time for 180 s in Fig. 5 (d) and 5 (g). Meanwhile, propidium iodide (PI) could stain the necrotic cells or the late apoptotic cells, which lost the integrity of the cell membrane, and make them

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present red fluorescence in Fig. 5 (e) and 5 (h). In conclusion, with the extension of an exposure duration time, the number of apoptosis and necrosis increased significantly.

Fig. 5. LSCM images of Annexin V-FITC/PI double-stained E. coli in fluorescence and bright field: (a)–(c) control samples, (d)–(f)/(g)–(i) treated samples under plasma exposure duration of 60 s and 180 s

3.4 Impact on Quality Attributes of Fresh Pork Meat To study the effect of gliding arc discharge on fresh pork meat quality, the samples were stored at 4 ± 1 °C for 5 days, and the changes of redness and total volatile basic nitrogen (TVB-N) were determined, as shown in Table 1. When the exposure duration time was 10 s and 60 s, the redness value decreased faster than that of the untreated group. When the exposure duration time was 30 s, the redness value was the slowest and the difference was significant (P < 0.05). With the extension of storage time, the content of TVB-N in each group increased continuously while the content of TVB-N in the untreated group increased the fastest. When the exposure duration time was 30 s, the increase of VBN content was the slowest, and significant compared with the untreated group (P < 0.05). Therefore, the preservation effect was optimized with the gliding arc discharge exposure time of 30 s, which can protect the color of pork and improve the freshness of pork to a certain extent.

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Table 1. The changes of redness and total volatile basic nitrogen (TVB-N) of treated pork samples Properties

A * Redness

TNB-N (mg/100 g)

Days after Plasma treatment

Plasma treatment time (s) 0

10

30

60

0

16.56 ± 0.18a

16.54 ± 0.13a

16.52 ± 0.12a

16.58 ± 0.23a

1

14.03 ± 0.09a

14.01 ± 0.17a

14.57 ± 0.14b

14.00 ± 0.14a

2

12.51 ± 0.09a

13.06 ± 0.18b

13.25 ± 0.09b

13.30 ± 0.19b

3

11.56 ± 0.25a

12.66 ± 0.10c

12.79 ± 0.09c

12.24 ± 0.15b

4

11.00 ± 0.19a

11.35 ± 0.12b

12.66 ± 0.20c

11.26 ± 0.12bc

5

9.99 ± 0.18a

11.20 ± 0.08b

12.50 ± 0.17c

11.00 ± 0.09b

0

5.27 ± 0.50a

5.30 ± 0.33a

5.31 ± 0.37a

5.31 ± 0.30a

1

12.00 ± 0.29c

11.00 ± 0.21c

6.90 ± 0.24a

9.50 ± 0.23b

2

16.99 ± 0.32d

15.03 ± 0.15b

12.51 ± 0.51a

15.86 ± 0.33c

3

23.33 ± 0.25d

22.66 ± 0.44c

16.87 ± 0.39a

21.90 ± 0.19b

4

25.76 ± 0.41c

25.54 ± 0.39c

22.00 ± 0.42a

25.01 ± 0.20b

5

27.99 ± 0.28d

26.97 ± 0.22c

15.06 ± 0.22a

25.86 ± 0.12b

a–d indicated significant difference (P < 0.05).

4 Conclusions In this study, a gliding arc discharge plasma method was built to inactivate E. coli, a very important food-borne harmful microorganisms. The mechanism of inactivation was revealed by extracellular protein concentration and surface morphology, indicating that the intensified physic-chemical interaction between ionized species and bacteria membrane through oxidized effects. In addition, the bactericidal effect of this method on the surface of fresh pork meat samples was performed, and the results showed E. coli on the surface of pork could be effectively removed by gliding arc discharge plasma treatment. What’s more, the treatment will not damage the quality of fresh pork meat while show a better cold sterilizing efficacy. This work is a step towards the practical and effective use of gliding arc discharge plasma in the application of fresh food preservation. Acknowledgements. This work was funded by the General Project of Science and Technology Program of Beijing Education Commission (KM201610020014).

References 1. He, Z.Y., Wang, Z., Yang, K., et al.: Research progress on microbial control measures in the preservation of cold fresh meat. Breeding Feed 20, 63–65 (2021). https://doi.org/10.13300/j. cnki.cn42-1648/s.2021.05.025 2. Experimental study on pyrolysis of domestic waste gasification tar by magnetic rotating sliding arc plasma. Zhejiang University (2018). CNKI:CDMD:2.1018.024374

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3. Bermúdez-Aguirre, D., Wemlinger, E., Pedrow, P., et al.: Effect of atmospheric pressure cold plasma (APCP) on the inactivation of Escherichia coli in fresh produce. Food Control 34, 149–157 (2013). https://doi.org/10.1016/j.foodcont.2013.04.022 4. Roth, J.R., Sherman, I.M., Gadri, R.B., et al.: A remote exposure reactor (RER) for plasma processing and sterilization by plasma active species as one atmosphere. IEEE Trans. Plasma Sci. 28, 5663 (2000). https://doi.org/10.1109/27.842864 5. Zhang, Y., Wei, C., Cao, W., et al.: A plasma-activated Ni/a-A1203 catalyst for the conversion of CH4 to syngas. Plasma Chem. Plasma Process. 20, 137–144 (2000). https://doi.org/10. 1023/A:1006978012228 6. Sugiarto, A.T., Masayuki, S.: Pulsed plasma processing of organic compounds in aqueous solution, aqueous solution. Thin Solid Films 396, 295–299 (2001). https://doi.org/10.1016/ S0040-6090(00)01669-2 7. Ma, Y., Zhang, G.J., Shi, X.M., et al.: Bacteria inactivation mechanisms by dielectric barrier discharge. High Voltage Eng. 2, 363–367 (2008). https://doi.org/10.13336/j.1003-6520.hve. 2008.02.017 8. Yahyazadeh, M., Omidbaigi, R., Zare, R., Taheri, H.: Effect of some essential oils on mycelial growth of Penicillium digitatum Sacc. World J. Microbiol. Biotechnol. 24, 1445–1450 (2008). https://doi.org/10.1007/s11274-007-9636-8 9. Liao, X.Y., Li, J., Muhammad, A.I., et al.: Preceding treatment of non-thermal plasma (NTP) assisted the bactericidal effect of ultrasound on Staphylococcus aureus. Food Control 90, 241–248 (2018). https://doi.org/10.1016/j.foodcont.2018.03.008 10. Fang, J., Xu, Q.X., Xian, C.B.: Determination of volatile basic nitrogen by semi-automatic Kjeldahl nitrogen analyzer. Guangzhou Chem. Ind. 47, 108–109+156 (2019). https://doi.org/ 10.3969/j.issn.1001-9677.2019.07.041 11. Fresh and frozen pork lean, cuts. https://kns.cnki.net/kcms/detail/detail.aspx?FileName=SJP DD3ED6EAE43A83E6D86F1672374D475AF&DbName=SJPD2019. Accessed 31 May 2021 12. Hertwig, C., Leslie, A., Meneses, N., et al.: Inactivation of Salmonella Enteritidis PT30 on the surface of unpeeled almonds by cold plasma. Innov. Food Sci. Emerg. Technol. 44, 242–248 (2017). https://doi.org/10.1016/j.ifset.2017.02.007 13. Kilonzo, N.A., Liu, S., Yannam, S., Patras, A.: Atmospheric cold plasma inactivation of salmonella and Escherichia coli on the surface of golden delicious apples. Front. Nutr. 5, 120 (2018). https://doi.org/10.3389/FNUT.2018.00120 14. Kim, S.Y., Bang, I.H., Min, S.C.: Effects of packaging parameters on the inactivation of Salmonella contaminating mixed vegetables in plastic packages using atmospheric dielectric barrier discharge cold plasma treatment. J. Food Eng. 242, 55–67 (2019). https://doi.org/10. 1016/j.jfoodeng.2018.08.020 15. Ahn, H.J., Kim, K.I., Hoan, N.N., et al.: Targeting cancer cells with reactive oxygen and nitrogen species generated by atmospheric-pressure air plasma. PLoS ONE 9, e86173 (2014). https://doi.org/10.1371/journal.pone.0086173 16. Dezest, M., Bulteau, A.L., Quinton, D., et al.: Oxidative modification and electrochemical inactivation of Escherichia coli upon cold atmospheric pressure plasma exposure. PLoS ONE 12(3), e0173618 (2017). https://doi.org/10.1371/journal.pone.0173618 17. Surowsky, B., Froehling, A., Gottschalk, N., et al.: Impact of cold plasma on Citrobacter freundii in apple juice: inactivation kinetics and mechanisms. Int. J. Food Microbiol. 174, 63–71 (2014). https://doi.org/10.1016/j.ijfoodmicro.2013.12.031

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18. Gao, W.X.: Research advances in the interaction between microbial infection and apoptosis. Biol. Teach. 43, 4–6 (2018). CNKI:SUN:SWJX.0.2018-11-002 19. Zhang, L.L., Zhang, L.F., Hu, Q.P., et al.: Chemical composition, antibacterial activity of Cyperus rotundus rhizomes essential oil against Staphylococcus aureus via membrane disruption and apoptosis pathway. Food Control 80, 290–296 (2017). https://doi.org/10.1016/j. foodcont.2017.05.016

Design of a Single Chip HF-UHF Dual-Band RFID Tag Antenna Zhao Yang1 , Yuan Zhang1 , Lei Zhu2(B) , Lin Shen3 , Yanping Du1 , and Chaohui Yu4 1 School of Mechanical and Electrical Engineering, Beijing Institution of Graphic

Communication, Beijing, China 2 Postal Technology R&D Center, Beijing Institution of Graphic Communication, Beijing, China

[email protected]

3 Beijing Urbane Culture Communication Co. Ltd., Beijing, China 4 School of Printing and Packing Engineering, Beijing Institution of Graphic Communication,

Beijing, China

Abstract. To improve the working performance of radio frequency identification (RFID) tags and reduce the size of the tags, a compact dual-band high-frequency (HF) and ultrahigh-frequency (UHF) passive RFID tag antenna is designed that works in the 13.56 MHz band as well as in the 915 MHz band in this paper. For the chip used (EM4423), the dual-band antenna is composed of an 11-turn spiral coil calculated by the modified Wheeler formula and a symmetrical dipole antenna with a matching ring. The designed dual-band antenna has a good impedance match with the chip used and it operates frequency from 849 MHz to 939 MHz covering the UHF operating band of China, the United States, Europe, and so on. The experimental results reveal that the maximum gain of UHF-RFID tag antenna is 1.3 dB. In addition, the size of the antenna is 46.4 × 41 × 0.03 mm3 , realizing the design goal of dual-band RFID tag antenna miniaturization. Keywords: Dual-band RFID tag antenna · Single chip · Impedance matching · Miniaturized tag antenna

1 Introduction Radio frequency identification (RFID) technology has been widely used in the field of Internet of Things. High frequency (HF)-ultra-high frequency (UHF) dual-band RFID tags due to the characteristics of both HF and UHF are increasingly in demand. Therefore, the study of integrated HF-UHF dual-band RFID tags has important practical significance. The antenna is an essential factor in determining the performance and cost of the tag. Many scholars have done a lot of research on the design and application of dual-band RFID tag antennas. The existing research results focus on two aspects: one is the dual chips dual-band RFID tag antenna [1–3], and the other is the single chip dual-band RFID tag antenna [4, 5]. In terms of dual chips dual-band tag antennas: due to the use of dual chips, this type of tag is inconvenient for the compact design of the antenna structure. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 301–305, 2022. https://doi.org/10.1007/978-981-19-1673-1_45

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Although literature [4] and [5] designed single chip dual-band antennas, neither of them paid much attention to the miniaturization of antennas. This paper studies and designs a HF-UHF dual-band RFID tag antenna and conducts simulation experiments. The design of a dual-band antenna achieves good impedance matching between the tag antenna and chip, and realizes the purpose of miniaturization.

2 Antenna Goal The RFID tag chip used in this article is the EM4423 chip. According to the theory of maximum power transmission, the designed antenna impedance needs to be conjugate matched with the impedance of the dual-band chip. The input capacitance of the EM4423 chip at 13.56 MHz is 50PF, corresponding to its capacitive reactance of 234.73 . To achieve impedance conjugate matching, the inductive reactance of the HF RFID antenna should be designed as 237.74 . The input impedance of EM4423 chip is 22.5 − j349  at 915 MHz, so the design target of UHF RFID tag antenna impedance is 22.5 + j349 . Another research purpose of this paper is to realize the miniaturization of HF-UHF dual-band RFID tag antenna.

3 Dual-Band HF-UHF Antenna Design Considering that the coupling between the HF antenna and the UHF antenna will affect the radiation performance of each other, the design idea of the dual-band RFID tag antenna proposed in this paper is to design the HF antenna first, then design the UHF antenna on the basis of the HF antenna, and finally determine the structure and size of the antenna. The substrate of the antenna is PET (εr = 3, tan δ = 0.02), which is flexible and stickable. The HF antenna adopts the design of a square coil. According to the expression proposed by Sunderarajan S. Mohan [6], which is suitable for calculating the plane spiral integral inductance the modified Wheeler formula. Based on the current RFID tag antenna production process this article sets the spacing and turn width of the coil antenna to be fixed at 0.5 mm. After calculation, in terms of the resonant frequency of the HF antenna and the realization of the HF RFID tag miniaturized, the structure and size of the coil with 11 turns and the outer diameter of 29.8 mm are more in line with our expectations. The structure of the UHF antenna proposed in this paper is designed on the basis of the existing HF antenna. In order to achieve the conjugate matching between the antenna and the chip, this paper adopts a matching ring structure. Figure 1 illustrates the structure of HF-UHF dual-band RFID tag antenna.

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Fig. 1. Proposed HF-UHF dual-band RFID tag antenna structure

The HF antenna is a eleven-turn spiral coil with dout = 29.8 mm, din = 8.8 mm, w = 0.5 mm, s = 0.5 mm, c = 3.4 mm. The dipole UHF antenna structure parameters are L1 = 10 mm, L2 = 12 mm, L3 = 8 mm, H1 = 3 mm, H2 = 4 mm, H3 = 3 mm, H4 = 2 mm, H5 = 29.5 mm, H6 = 10.1 mm, W1 = W4 = 1 mm, W2 = W3 = 2 mm.

4 Simulation Experiment and Results The antenna proposed in this paper is simulated and optimized in ANSYS HFSS. The configuration of the computer used is CPU: E5-2603 v3 @1.60 GHz, RAM: 24.0 GB. This paper uses the S11 (represents the return loss characteristic) to describe the degree of impedance matching between the antenna and the chip. Figure 2(a) shows the S11 of the HF antenna reaches the lowest at 14.9 MHz, and the S11 at 13.56 MHz is −24.43 dB.

Fig. 2. The simulated S11 of the dual-band antenna: (a) HF. (b) UHF.

The resonant frequency of the designed HF antenna is 14.9 MHz, which is slightly higher than 13.56 MHz. This is to consider that in the actual application of the RFID tag antenna, the capacitance of the chip and the inductance of the antenna will increase, resulting in a decrease in the resonant frequency of the antenna. From Fig. 2(b) we can see the simulated S11 of the designed HF-UHF dual-band RFID tag antenna at 915 MHz is −46.16 dB. And the −10 dB bandwidth for the UHF band frequency covers 849 MHz to 939 MHz which proves that the impedance of the antenna and the chip achieve a good

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conjugate match. HF antenna has a great influence on the S11 of UHF antenna, when there is no HF coil antenna case, the design of the UHF antenna S11 at 915 MHz up to −16.64 dB, but as shown in Fig. 2(a) UHF antenna smaller effects on the resonance frequency of the HF antenna, the existence of the UHF antenna only offset it by 0.1 MHz. This indicates that it is feasible to design the HF coil antenna first and then design the UHF antenna. It can be seen from Fig. 3(a) that the designed HF antenna increases the reactance value of the UHF antenna, reduces the resistance value of the UHF antenna, and makes the UHF antenna reach the ideal impedance value. As shown in Fig. 3(a), the impedance of the UHF antenna designed in this paper at 915 MHz is 25.49 + 347.3 , which is close to the conjugate impedance value of the chip (22.5 + 349 ).

Fig. 3. Impedance and gain of UHF antenna: (a) impedance (b) gain

Figure 3(b) shows the xz plane gain pattern, xy plane gain pattern of the designed UHF antenna simulation. The maximum gain of the designed UHF antenna is 1.3 dB. Table 1. Antenna performance comparison Ref.

[2]

[3]

[4]

[5]

This work

Dimension

52 × 83 × 0.8

95 × 95 × 0.8

84 × 54 × 0.8

80 × 40 × 0.8

46.4 × 41 × 0.03

Max Gain

−1.89

2.08

0.5

1

1.3

Table 1 shows that the size of the designed antenna is significantly smaller than that of the current same type of antenna. And the gain performance of the UHF antenna is also relatively good. Based on the current simulation results and considering the practical application scenarios, we suggest that copper foil materials be used to manufacture antennas.

5 Conclusion This paper designs a single chip compact HF-UHF dual-band RFID tag antenna. The S11 of the HF antenna is −24.43 dB at 13.56 MHz, and reaches −58.68 dB at the resonant

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frequency of 14.9 MHz. The S11 of the UHF antenna is −46.16 dB at the resonant point of 915 MHz, and its working bandwidth is 90 MHz, which meets the requirements of impedance matching with the EM4423 chip used. The maximum gain of UHF antenna is 1.3 dB. Compared with the previous research work of dual-band RFID tag antenna of the same type, the design of this paper has achieved remarkable effect in miniaturization, and the size of the antenna is only 46.4 × 41 × 0.03 mm3 . The designed dual-band tag antenna can carry out near-field and far-field communication, which can be used in fields such as circulating packaging boxes. In order to make the production of RFID tag antennas more flexible and environmentally friendly, we will study printed dual-band RFID tag antennas using conductive ink as the antenna material. Acknowledgements. This research is supported by Funding information: Research and Application of Flexible RFID Printing Technology for Publication Internet of Things (Ec201807); Research and Innovation Team Project of Beijing Institution of Graphic Communication (Ed202001); General Project of Basic Research of Beijing Institution of Graphic Communication (Eb202001).

References 1. Iliev, P., Le Thuc, P., Luxey, C., et al.: Dual-band HF-UHF RFID tag antenna. Electron. Lett. 45(9), 439–440 (2009) 2. Zi Long, M., Li Jun, J., Jingtian, X., et al.: A single-layer compact HF-UHF dual-band RFID tag antenna. IEEE Anten. Wirel. Propagat. Lett. 11, 1257–1260 (2012) 3. Sakonkanapong, A., Phongcharoenpanich, C.: Near-field HF-RFID and CMA-based circularly polarized far-field UHF-RFID integrated tag antenna. Int. J. Anten. Propagat. 2020, 1–15 (2020) 4. Deleruyelle, T., Pannier, P., Egels, M.: Dual Band Mono-Chip HF-UHF Tag Antenna. IEEE (2010). 978-1-4244-4968-2/10 5. Ha-Van, N., Seo, C.: A single-feeding port HF-UHF dual-band RFID tag antenna. J. Electromagnet. Eng. Sci. 17(4), 233–237 (2017) 6. Mohan, S.S., del Mar Hershenson, M., Boyd, S.P.: Simple accurate expressions for planar spiral inductances. IEEE J. Solid-State Circuits 34(10) (1999)

Structure and Control Strategy Design of Wide-Format Ink-Jet Printing Machine Taotao Chen1 , Yuansheng Qi2(B) , Libo Dong1 , Su Gao1 , Taifen Bao1 , and Rui Zhu1 1 School of Mechanical and Electrical Engineering, Beijing Institute of Graphic

Communication, Beijing, China 2 School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication,

Beijing, China [email protected]

Abstract. Ink-jet printing machine is a kind of precision equipment for precise graphic printing. In addition to its printing accuracy and speed are closely related to the performance of ink-jet print heads, it is also closely related to its control system and working mode. This article focuses on current ink-jet printing machines. Research on the problems of printing quality and speed. Among them, the quality problems are mainly manifested in the printing accuracy and resolution are not high enough, and the speed problems mainly include the overall printing speed is not high. This paper proposes a method of fine-tuning the position of the substrate, and superimposing the pattern to improve the resolution. The plan mainly includes the overall structure of the ink-jet printing machine, motor control strategy and so on. Keywords: Ink-jetprintin · Print head · Printing accuracy · Resolution · Linear motor

1 Introduction This article analyzes the composition, working principle and existing problems of wideformat ink-jet printers, and proposes optimization schemes in terms of structure or control methods for existing problems. Optimization design of the overall structure of the wideformat ink-jet printing machine, including the frame, the nozzle trolley, and the cloth feeding mechanism is completed by using the three-dimensional software Solid-works to establish a solid model of the machine and test its mechanical properties. Moreover, the nozzle motion control system is optimized by designing the nozzle arrangement method and motor control strategy to ensure the stability of printing.

2 Overall Structure of Ink-Jet Printing Machine This section mainly introduces the overall composition of wide-format ink-jet printers, expounds the working process and working principle of ink-jet printing machines, plans and designs the machine composition of ink-jet printing [1], and formulates the design parameters of ink-jet printing machines. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 306–315, 2022. https://doi.org/10.1007/978-981-19-1673-1_46

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2.1 Overall Structure Figure 1 shows the overall structure with main components of this design. The functions and principles of each part are as follows:

Fig. 1. Schematic diagram of overall structure

1-Frame: carrying and guiding belt feeding mechanism, control board, linear motor, nozzle trolley, etc.; 2-Guide belt drive motor: The guide belt drive motor is a servo motor, which is connected to the main control board to accurately locate the position of the guide belt; 3-Guide belt: The guide belt is the carrier of the substrate, which can carry the substrate to move, and cooperate with the movement of the nozzle trolley for printing. 4-High-speed camera: Capture the position of the substrate and graphic information, and transmit the data to the main control board and computer in real time to ensure accurate printing. 5-Linear motor: The stator end of the linear motor is installed on the frame, the nozzle trolley is installed at the rotor end, and the grating sensor is installed inside, which achieves repeated positioning accuracy, which plays a key role in printing quality. 6-Nozzle trolley: The nozzle trolley is the carrier of the print head and the high-speed camera. The four color print heads of CMYK are evenly arranged according to a certain distance and order. 2.2 Rack Design The printing accuracy of the ink-jet printing machine depends on the ink-jet print head. Performance and control system are also closely related to frame structure and material performance as shown in Fig. 2, it is the theme framework of the ink-jet printing machine. With reference to the human body’s best operating height in the upright state, the overall height of the frame is set to 1.5 m, and the height of the substrate and the control panel are also about 1.5 m, so as to observe the working status of the print head and operate the operation panel during the production process. The rack is 2.96 m long, and the installation positions of the ink supply system and control box are reserved in advance, and its overall length exceeds the length of the linear motor to ensure lateral stability. This design uses 4040 aluminum profile with lighter weight and better performance, which reduces the cost of production, assembly and transportation.

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Fig. 2. Three-dimensional model of the bracket

2.3 Design of the Carriage Mechanism 2.3.1 Nozzle Car Design As shown in Fig. 3, it is the structure diagram of the three-dimensional model of the nozzle trolley. This structure is the direct carrier of the nozzle head, the nozzle control card and the camera. The carriage is designed according to the size of the nozzle head and consists of two parts, including the motor connection bracket and the nozzle installation. The motor connection bracket and the nozzle mounting frame are fixed by five screws, and the screws can be removed later to adjust the two. The relative height between them is easy to adjust the best printing height and adapt to different thickness substrates. The motor connection bracket is set with the camera and the board mounting holes.

 1.Nozzle 2. Nozzle mounting bracket 3. Motor connection bracket 4. Linear motor mover 5 Linear motor body 6. Drag chain 7. Frame Fig. 3. 3D model of the nozzle trolley

2.4 Modal Analysis of Ink-Jet Printing Machine Structure 2.4.1 Basic Vibration Equation of Ink-Jet Printing Machine Structure The overall structure of the ink-jet printing machine is a time-invariant, nonlinear multi-degree-of-freedom system [2]. According to Hamilton’s principle, the differential equation of motion of the system can be obtained as:     (2.1) [M ] X¨ + [C] X˙ = {F(t)}

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In the above formula, [M ], [C] and [K] respectively refer to the inertial   mass, viscous damping, and stiffness matrix of the system, {X } is the displacement, X˙ is the velocity,   X¨ is the acceleration, and {F(t)} is the shock force vector. ⎧ ⎧ ⎫ ⎫ f1 ⎪ X1 ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎨ f2 ⎪ ⎨ X1 ⎪ ⎬ ⎬ .. , {F(x)} = .. {M } = . ⎪ . ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ fn−1 ⎪ ⎪ X1 ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎩ ⎩ ⎭ ⎭ Xn fn

(2.2)

The ink-jet printing mechanism itself does not work to the outside world, and there is no force between ink-jet printing mechanism and the external environment. Since, the movement resistance of the ink-jet head is negligible, therefore {F(x)} = 0, simultaneously an ideal un-damped multi-degree-of-freedom vibration movement can be obtained by;   (2.3) [M ] X¨ + [K]{X } = {0} The free vibration of the structure can be considered as the superposition of a series of simple harmonic vibrations, assuming that the solution of Eq. (2.4) is: {X} = {∅}ejωt

(2.4)

Where ω is the simple harmonic vibration frequency, {φ} is the amplitude array. Combine (2.3) and (2.4) to get:  (2.5) [K] − ω2 [M ] {∅} = {0} The conditions for this formula to be solved are:  det [K] − ω2 [M ] {∅} = {0}

(2.6)

Solving the Eq. (2.6), we can get ω12 , ω22 , ω32 , . . . . . . ωn2 , n eigenvalues. It is also possible to obtain n linearly independent dimensional feature vectors ∅1 , ∅2 , ∅3 . . . . . . ∅n corresponding to each feature value. In the modal analysis calculation, the square root of the eigenvalue is taken as the i − th order mode shape  structure, and each order

of the mode shape forms an n × n order square matrix, and ∅n×n = [∅1 , ∅2 . . . . . . ∅n ] is the mode matrix. 2.4.2 Finite Element Modal Calculation of Ink-Jet Printing Machine Structure In order to make the analyzed modes with higher accuracy, we appropriately widen the frequency band of modal calculation and set the number of extracted modes to 8th order. Figure 4 show the 1–8 order seismic patterns of the main structure of the ink-jet printing machine. The results of the first 1–8th order resonance frequency data of this mechanism are shown in Table 1.

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Order

1

2

3

4

5

6

7

8

Frequency

7.98

14.0

18.7

19.5

20.7

21.6

23.8

24.5

Fig. 4. Eighth-order vibration shape of printer

For the ink-jet printer of this structure, the moving parts are divided into two parts. Only the movement of the word carriage is a reciprocating linear motion. During the printing process, the carriage is from start to uniform speed and from when the uniform speed is decelerated to zero, there is a process of acceleration and deceleration. This process will produce a periodic shock force of F = Ma for the overall structure. The limit working state of the linear motor is that the maximum acceleration is 0.99 G and the maximum operating speed is 1.8 m/s. At this time, the corresponding The highest shock frequency is T1 f = 0.96 HZ. Through modal analysis, it can be seen that the first 8 order frequency of the system is 7.98 Hz − 24.5 Hz. It can be seen that when the motor running speed reaches the highest, the shock frequency is only 0.96 HZ, so the design of this mechanism will not resonate with the movement of the sprinkler carriage. Ensure the stability of the entire organization and meet the design requirements.

3 Nozzle Head Motion Control 3.1 Array of Nozzle Head The design of the arrangement of the nozzle head should consider two factors: The number and relative position of the nozzle head. In general, the scanning ink-jet printing machine often adopts the method of setting multiple groups of nozzles in the scanning direction to improve the printing area of each scan. To scanning ink-jet printing machine, it was just a matter of several group of nozzle, the nozzle spray car reciprocating motion with moving substrates can complete printing work, reduce the manufacturing cost, and can move through the adjustment of substrates and nozzle mobile speed, to realize the

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control of the resolution, and scanning the ink-jet printing technology for fault has a better tolerance of the nozzle. The ink-jet printing machine designed in this paper is a scanning type, and four monochromatic nozzles [3] of C, M, Y and K are selected as one group in color. In scanning direction, two sets of nozzles are used to increase the printing width of a single scan. The arrangement is shown in Fig. 5.

Fig. 5. Nozzle head arrangement

Nozzle color arrangement order [4]. In the actual printing process, the black obtained from the three-color mixture of C cyan + M magenta + Y yellow is not as good as the simple black in color expression, and the superposition of three colors to form black needs to be printed three times at the same point, resulting in Slow process. So the ink-jet printing machine is equipped with a black nozzle. Based on the superposition principle of colors, when colors are superimposed, the proportion of different primary colors can be adjusted [5], so that infinite colors can be formed theoretically. The ink-jet printing machine restores the image based on the principle of color superposition, which can be considered from the perspective of ink transparency. The order of ink transparency is yellow, magenta, cyan, and black. Therefore, the arrangement order of the nozzles can be arranged as Y, M, C, K in the scanning and printing direction, with black printing first, and yellow printing last. 3.2 Motion Pattern Analysis of Nozzle Head 3.2.1 Linear Motor Acceleration and Deceleration Control Curve There are three commonly used acceleration and deceleration control curves for motors: ➀ linear type, ➁ exponential type, and ➂ S type. Compared with the first two methods, the S-shaped speed change curve has good smoothness and is very suitable for the carriage motion system with high stability requirements. According to the calculation results in the previous section, the motion speed of the character car in 360 dpi mode is VL = 536 mm/s, and the motion speed of character car in 720 dpi mode: VH =

VL = 268 mm/s 2

(3.1)

In the actual working process of the ink-jet printing machine, the maximum speed of the carriage movement is generally lower than the theoretical design speed to prevent

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the nozzle from overloading. Therefore, in the 360 dpi printing mode VL = 500 mm/s, VH = 250 mm/s, the effective stroke of the linear motor is set to 2200 mm, and the effective printing width of the ink-jet printer is set to 1800 mm. The acceleration and deceleration strokes are 200 mm respectively.

Fig. 6. Type acceleration and deceleration motion control curve

Establish the relationship between acceleration, speed, and time as shown in Fig. 6. t 0 , t 1 , t 2 , t 3 , correspond to the start time of acceleration, uniform acceleration, deceleration, and uniform motion state respectively. According to the movement characteristics of the nozzle, the acceleration process and the deceleration process are symmetrical about space. According to the S-shaped motion graph, the relationship between motion speed, displacement and time can be established as: ⎧1 2 At , 0 < t < t1 ⎪ ⎪ ⎨ 21 2 At + (t − t1 )At, t 1 < t < t2 (3.2) Vt = 2 t ⎪ 1 2 ⎪ ⎩ 2 At + (t2 − t1 )At1 + ∫ a(t)d (t), t2 < t < t3 t2

S(t)

⎧t ⎪ ⎪ ∫ V (t)d (t), 0 < t < t1 ⎪ ⎪ ⎪ 0 ⎪ ⎨ t1 t t 1 < t < t2 = ∫ V (t)d (t) + ∫ V (t)d (t), t1 ⎪ 0 ⎪ ⎪ t1 ⎪ t2 t ⎪ ⎪ ⎩ ∫ V (t)d (t) + ∫ V (t)d (t) + ∫ V (t)d (t), t2 < t < t3 0

t1

(3.3)

t2

The acceleration and deceleration take the same time t1 − t0 = t3 − t2 , and the maximum acceleration of the linear motor is 9.9 m2 /s. Combining the above two formulas, there are: t3 =

2V A

(3.4)

A is the acceleration of the linear motor, and 3t is the end time of the acceleration process. V is the speed of the uniform ink-jet printing state. Therefore, in order to reduce

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the time consumed in the acceleration and deceleration process [6], the acceleration time 3t should be as small as possible. The maximum acceleration of the linear motor used here is 9.9 m2 /s, and in order to prevent the motor from being overloaded, the acceleration is set to 9.9 m2 /s. The effective running length of the linear motor is 2200 mm, and the data is substituted into the formula (3.4 can obtain the relevant motion parameters, the motion parameters are shown in Table 2). Table 2. Operating parameter table Performance parameter

Normal mode

High precision mode

Resolution

360 * 360 dpi

720 * 720 dpi

Printing speed Acceleration phase Deceleration phase Uniform phase Uniform motion time Acceleration(deceleration) time Total exercise time

0.5 m/s 25 mm 25 mm 2150 mm 4.3 s 0.1 s 4.5 s

0.25 m/s 12.5 mm 12.5 mm 2175 mm 8.7 s 0.05 s 8.8 s

3.3 Linear Motor Control Strategy In this paper, a three - loop control system with current inner loop, velocity inner loop and position outer loop is used to control the system. Speed loop proportional integral control (PI) is a single feedback controller without pre-filtering [7]. The PI 8 control method is used to adjust the internal current of the motor, and the PID control method is used to adjust the positioning of the linear motor subunit. The motion speed of the actuator seat is also controlled by P method. The control scheme of linear motor is shown in Fig. 7.

Fig. 7. Control scheme diagram of linear motor

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The linear motor realizes the positioning of the ink-jet head through the PID control method adjustment, PID is the control is an automatic control output type, its basic principle is shown in Fig. 8. PID control involves three laws: proportional control, integral control and differential control.

Fig. 8. Principle of PID control system

PID control strategy is the most ideal control mode in automatic control output type, with the function of timely and rapid adjustment, eliminate margin and advance control. The parameters of the three functions are properly selected and can give full play to the advantages of these three functions and achieve a good control effect. r(t) is the input value, actual output is y(t) and control deviation e(t) is: e(t) = r(t) − y(t)

(3.5)

  1 t de u(t) = Kp e(t) + ∫ e(t)dt + TD T 0 dt

(3.6)

PID Delivery function:

KP is the proportional constant, KI is the integral constant, KD is the differential constant.

4 Conclusions The design was established into a three-dimensional model using three-dimensional modeling technology. The shock frequency of the moving structure is calculated, and the finite element analysis software is used to perform a modal analysis on the assembly structure. The analysis result is compared with the shock frequency of the moving mechanism to verify the rationality of the mechanism design. Research and analysis of the working principles of various types of nozzles. Aiming at the principle and working characteristics of the nozzles, with the goal of improving the printing speed and printing quality, the layout of the nozzles is designed to ensure the stability and speed of printing. The movement of the motor is designed with a suitable movement curve, and combined with the design goals, the work efficiency under different printing modes is calculated. A PID control strategy is set for the control of the linear motor, so that the nozzle positioning is more accurate and the movement state is more stable. Acknowledgments. This study is supported by the Printing intelligent ink-jet printing equipment R&D project (04190118002/085) which is School-level Foundation of Beijing Institute of Graphic Communication.

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References 1. Xin, Z.: Structure and working principle of ink-jet printer. Comput. Self-Made 2, 111–112 (2001) 2. Li, J.: Structure Design and Motion Simulation of Wide-Format Ink-Jet Printer. Chongqing University (2011) 3. Kyocera developed ink-jet printing head with CMYK4 color printing simultaneously. China Printing 2015(12), 103 (2015) 4. Wang, Y., Tang, W.: Determination of color sequence of offset printing. Mech. Electric. Inf. 2, 45–47 (2005) 5. Lina, C., Zhen, L.: Research on ink quantity control of ink-jet printed output equipment. Packag. Eng. 32(19), 11–17 (2011) 6. Jin, S., Chu, J.: Methods to improve the efficiency of digital printing machines. Shandong Indust. Technol. 2018(1), 33+6 (2018) 7. Gao, F., Si, Y.: Design of servo parameter and control parameter of linear motor feed system. Shanxi Electron. Technol. 2018(3): 34-3 (2018)

Study on Influence of Four Various Structure Static Mixers on Mixing Effect During Solvent-Less Compound Mixing Hongwei Xu1(B) , Zhaohua Ma1 , Luofan Liu1 , Xiao Xu1 , Zhicheng Xue2 , and Darun Xi2 1 Faculty of Printing, Packaging, and Digital Medal Technology, Xi’an University of

Technology, Shaanxi 710054, China [email protected] 2 Shaanxi Beiren Printing Machinery Co., Ltd., Shaanxi 714000, China

Abstract. The mixing effect of solvent-free composite adhesive glue has a great impact on the compound performance of solvent-free laminating products. This paper uses the theory of liquid-liquid two-phase flow to carry out mathematical modeling and analyze the diffusion theory modeling between two-phase mixing. Fluent software is used to conduct 3d model of solvent-free materials A and B mixing process in four various static mixers. Through the simulation calculation of the flow field of solvent-free material A and B in the mixer, the influence of the mixer’s internal structure on the mixing effect at the mixer’s outlet was analyzed. By analyzing and comparing four mixers with different mixing units, the mixing effect of TCCA type of static mixer is best. And through the analysis, the large pressure loss can be solved through decreasing the number of the units in the TCCA type of static mixer. Keywords: Solvent-less compound · Mixing effect · Static mixer · Simulation · Pressure loss

1 Introduction Many countries in the world have widely used the solvent-free laminating method to produce soft package. In contrast, most domestic soft package manufacturers still use solvent-based adhesives to produce products. Although this dry laminating method is simple and mature, due to the use of intermediate layer adhesive, there will be a small amount of solvent residues in the laminating process, which will make the packaged products have odor and poor sanitary performance. In order to solve this problem fundamentally, it is necessary to change the type of solvent and compound way to reduce the residual solvent amount. The comparison between solvent-free compounding and dry compounding shows that solvent-free compounding has great advantages in the use of glue amount, environmental performance, product quality, production speed and energy consumption, which will be the development trend of future compounding technology. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 316–322, 2022. https://doi.org/10.1007/978-981-19-1673-1_47

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Indeed, there are many factors which have effects on the performance of solventless laminating. Some experiments shows that the proportion of A and B solvent-less laminating adhesive glues has effect on the folding endurance, laminating adhesive effect, and peel strength of solvent-less laminating adhesive [1]. Solvent-free laminating mixing machine is the key equipment in the solvent-free laminating process, its role is to mix A and B two kinds of solvent-less laminating adhesive glues in certain proportion evenly. For this machine, static mixer is widely used because of its advantages of energy saving and structure simple [2]. There are various structure static mixer. Noraphon Bunkluarb et al. [3] proposed six structure static mixers and checked the mixing effect under the various structure static mixers. A comparative analysis of mixing effect of Kenics and LPD mixers was made by Filipp Göbel et al. [4]. The results showed that the structure parameters of static mixer have a great influence on the mixing effect. In this paper, the mixing process of four structures of static mixers is modeled and analyzed, from which the better static mixer is determined.

2 Governing Equations To study liquid flow in static mixers containing blades, liquid is assumed to a laminar flow because it creates a small pressure loss in the pipe. This paper studies the two liquids flow in a static mixers with four various structures of blade row type. The liquids flow in the static mixer is described by the continuity equation and the Navier-Stokes equations: ∂ρm + ∇ · (ρm υ m ) = 0 ∂t n 

υm =

φi ρi υ i

i=1

ρm =

(1)

ρm n 

φi ρi

(2)

(3)

i=1

     ∂ (ρm υ m ) + ∇ · ρm υ 2m = ∇p + ∇ · μm ∇υ m + ∇υ Tm + ρmg + F ∂t

(4)

Where ρi and υ i represent the fluid density and average velocity of phase i, φi is the volume fraction, n is the phase number. μm is the viscosity coefficient, g is the gravity acceleration, F is the volume force. For the studying of two phase flow of liquid-liquid, the spread of liquid into each other must be considered. Therefore the spread equation of liquids is follow:  2 ∂ c ∂ 2c ∂ 2c ∂ ∂c ∂ ∂ + Fc + (cu) + (cv) + (cw) = Dm + + (5) ∂t ∂x ∂y ∂z ∂x2 ∂y2 ∂z 2 Where, c represents diffusible matter concentration, u, v and w are the components of diffusible mass velocity in three directions, Dm is the diffusion coefficient, F c is the Source term of diffusible matter.

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3 Numerical Models Now, there are lots methods of studying two phase flow of liquid-liquid in static mixer. James J. Feng et al. [5] studied two phase complex flow under microstructure. PiankoOprych [6] used computational fluid dynamics on prediction of two phase flow in SMX static mixer. In this paper, fluent software are used to model the various structure static mixers to analyze the mixing effect of solvent-less compound glue of A and B. For the static mixer, two types of stationary blades including 180° twisted blade in con-rotating (T), and 180° twisted blade in counter rotating (C). There are four types of static mixers are used in solvent-less laminating mixing machine. The problem of which of the four static mixers has the best mixing effect puzzles the technicians in the industry. There are no good method to check it out, but only computer simulation can solve it. We investigate the effects of mixing performance using four blade-pattern static mixers of circular cross section with the radius of 12 mm and the length of 168 mm. The structure of the first type of static mixer is made with ten twisted blades which arrayed by these two types of twist blade in 90° connection (TCCA), as shown in Fig. 1(a). The second type of static mixer is made with ten twisted blades which arrayed with the two types of blade in 0° connection (TCIA), as shown in Fig. 1(b). The third static mixer is made with ten twisted blades which array with one type of twisted blades in 90° connection (TTCA), as shown in Fig. 1(c). The fourth type of static mixer is made with ten twisted blades which arrayed with one type of twisted blade in in 0° connection (TTIA), as shown in Fig. 1(d).

Fig. 1. Four static mixers

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After the model was established, the pre-processing software FLUENT was imported to calculate the fluid domain using Boolean operation. Imported into ICEM, unstructured tetrahedral mesh was used for grid division. The material is defined as material A and material B, the corresponding parameters is presented in Table 1. Table 1. Solvent-less laminating adhesive and physical properties of air Item

Material A

Material B

Viscosity 23° (Pa·s)

1–1.2

0.6–0.7

Density (Kg/m3 )

1120

980

The inlet 1 flows into material A at a speed of 0.3 m/s, and the inlet 2 flows into material B at a speed of 0.24 m/s. The outlet is the pressure outlet, and the wall is set as the non-slip wall. The residual convergence values are less than 10–5 . After initialization, the iterative calculation is started.

4 Simulation Results In this study, we concentrate on the mixing effect in the outlet. After simulation computing, the colored images are generated to simulate the volume fraction of material A in the outlet of the static mixers. The ideal volume fraction of material A is 55%. Figure 2(a)– (d) presents the result of the materials flow through the static mixer of TCCA, TCIA, TTCA, TTIA.

Fig. 2. The volume fraction cloud image of material A on the section of outlet

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Fig. 3. The scatter diagram of the volume fraction of A on the section in the outlet

As shown in Fig. 2(a)–(d), the color of cloud image of Fig. 2(a) is uniform. In order to illustrate the mixing effect more clearly, the grid data on the cloud images are extracted and draw by the scatter plots, as shown in Fig. 3. There are 580 grid particles on the section in the outlet. The mixing effect control lines are decided as 50% and 60%. Figure 3 shows that the scatter diagram of TCCA has basically gathered between 54% and 57%, and the proportion of qualified mixing effect particles are 100%. Therefore, the mixing effect is best among these static mixers. The mixing effect of each mixer is discussed from the aspect of mixing nonuniformity coefficient. The volume fraction of material A in the circumferential section at the end of each mixing unit on the four mixers is intercepted. The mixing non-uniformity coefficient is calculated, and the line chart is drawn by using Origin software, as shown in Fig. 4.

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Fig. 4. Mixing non-uniformity coefficient of A and B through four static mixers

It can be seen from Fig. 4 that the mixing non-uniformity coefficient of material A on the circumferential section after material A and B pass through each mixing unit of the four types of mixers, only the mixing non-uniformity coefficient of the TCCA static mixer decreases fast. It can reach the 0.003, and the other three mixing non-uniformity coefficients only reach about 0.1. Therefore, in this respect, the structure of TCCA static mixer is the best. In terms of pressure field, the pressure drop of each static mixer can be obtained through data processing of the model after calculation, as shown in Table 2. Table 2. Pressure drop of four types of mixer Item

TCCA

TCIA

TTCA

TTIA

P (MPa)

0.357

0.307

0.329

0.334

Although the mixing effect of the 10 unit static mixer of TCCA can reach 0.003, the pressure drop has exceeded 0.35 Mpa. The pressure loss is large, therefore the structure of TCCA static mixer should be optimized. However, it can be seen from Fig. 4 that the number of non-uniform coefficient of material A and B begins to tend to the level after passing through the fifth unit. Therefore, in order to reduce the pressure loss, the number of mixing units of the mixer must to be optimized to 6 units.

5 Conclusion In this paper, three-dimensional modeling, mesh generation and solution setting of four different static mixers are carried out, and then material A and material B are input into the mixer according to the given proportion for fluid numerical simulation. Through the analysis of the simulation results, it is shown that the mixing effect of solvent-less material A and B through the static mixer TCCA structure is better than the mixing effect of the other three types of mixers. The qualified mixing particles on the circumferential

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section in the outlet of the static mixer of TCCA structure can reach 100%, and the proportion of the qualified mixing particles of the other three types of mixers is less than 40%. From the inspect of mixing non-uniformity coefficient and pressure loss, it is found that the pressure loss of material A and B entering the four types of mixers is more than 0.3 MPa, but the mixing speed of the first few units of the static mixer is relatively fast, and can quickly achieve the required mixing effect. That is to say, the mixer with fewer mixing units can achieve the mixing effect, and the pressure loss of the short pipe will be smaller. Therefore, to optimize the mixing unit number of the TCCA is feasible. Acknowledgements. This research project is supported by the Key R&D Plan of Shaanxi Province (approve number: 2021GY-262).

References 1. Xu, H., Wang, X., Lei, R., et al.: Experimental analysis of the effect of vacuum degassing technology on the solventless laminating adhesive performance. In: 2016 China Academic Conference on Printing & Packaging and Media Technology (2016) 2. Wei, Y., Xu, H., Han, Y., Feng, S.: Tooth profile optimization for mixing proportional pump of solvent-free laminating mixer. In: Advanced Graphic Communication, Printing and Packaging Technology - Proceedings of 2019 10th China Academic Conference on Printing and Packaging (2019) 3. Bunkluarb, N., Sawangtong, W., Khajohnsaksumeth, N., Wiwatanapataphee, B.: Numerical simulation of granular mixing in static mixers with different geometries. Adv. Differ. Equ. 2019(1) (2019) 4. Göbel, F., Golshan, S., Norouzi, H.R., Zarghami, R., Mostoufi, N.: Simulation of granular mixing in a static mixer by the discrete element method. Powder Technol. 346, 171–179 (2019) 5. Yue, P., Feng, J.J., Liu, C., Shen, J.: A diffuse-interface method for simulating two-phase flows of complex fluids. Fluid Mech. 515, 293–317 (2004) 6. Pianko-Oprych, P., Jaworski, Z.: CFD modelling of two-phase liquid-liquid flow in a SMX static mixer. Pol. J. Chem. Technol. 11(3), 41–49 (2009)

Kinematics Simulation and Material Delivery Trajectory Planning of Industrial Robot Guirong Dong(B) , Pihong Hou, Ling Wu, Jijun Luo, and Shisheng Zhou Faculty of Printing, Packaging Engineering and Digital Media Technology, Xi’an University of Technology, Shaanxi, China [email protected]

Abstract. Research on KUKA KR10 industrial robot, the kinematic model is established by D-H parameter method. The forward and the inverse kinematics were analyzed based on the kinematic modal. Monte Carlo method is used to simulate its workspace based on its model and Joint range of motion (JRM). Correctness and rationality of the kinematic model were analyzed using different methods of the manipulator path planning, which provides a reference for the trajectory planning of the industrial robot in the complex environment. Keywords: Industrial robots · Kinemeatics · Working space · Trajectory planning

1 Introduction The development of industrial robots has been advanced in recent years. Industrial robots are used more and more widely in modern manufacturing industry with its advantages of high precision and high efficiency. Taking the feeding and unloading production line as an example, unmanned, intelligent and flexible production lines can reduce production costs and improve transportation efficiency [1, 2]. Research on KUKA KR10, the link coordinate system of the robot was established by DH method, and the DH parameters table was obtained [3]; Then, Forward kinematics equation of manipulator with 6DOFs based on the Denavit-Hartenberg coordinate was set up through homogeneous transformation. The numerical solutions of its inverse kinematics equation were solved using the Levenberg-Marquardt method [4]. At the same time, based on the joint range of motion and the Forward kinematics equation, the Monte Carlo method [5–7] was used to simulate the workspace of the robot end effector. Finally, on the basis of the obtained inverse solution, the fifth degree polynomial interpolation and the seventh degree polynomial interpolation [8] were applied to simulate the loading and unloading process on the platform in joint space [9]. Through a series of simulation analyses, the accuracy of kinematics model was verified and the application ability of industrial robots was enhanced.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 323–331, 2022. https://doi.org/10.1007/978-981-19-1673-1_48

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2 Kinematic Modeling of KUKA KR10 Robot Manipulator could be regarded as a series of links connected by joints, as shown in Fig. 1(a), and the link coordinate system was used to describe the position relationship between the adjacent links, as shown in Fig. 1(b). Kinematics of the robot model was established before further analyses. The relative position of links were expressed by four kinematic parameters: Joint angle (θ ): The angle between two adjacent connecting rods rotating around the common axis; Offset (d): The distance in the direction of the common axis of two adjacent connecting links; Link length (a): The length of the common vertical line between two adjacent joint axes; Connecting links angle (α): The angle between two adjacent joint axes. The DH parameters of the KUKA KR10 robot and its Joint range of motion, Rated load speed were shown in Table 1. Rated load speed was the maximum speed of end effector of industrial robot in the process of rated load and uniform motion.

Fig. 1. KUKA KR10 Robot with six axes and link coordinate systems (a) KUKA KR10 Robot (b) Robot link coordinate systems

3 Kinematics Analysis Robot kinematics analyses mainly include forward kinematics analysis and Inverse kinematics analysis. The solution of Forward kinematics and the pose state of end effector is unique because each joint angle of the robot was known. However, when the pose of end effector was known, the possible solutions of each joint angle can be obtained by Inverse kinematics analysis, so the solutions of Inverse kinematics are not unique: The several different joints configurations can reach the same end effector position. The transformation between Cartesian space and joint space can be realized by kinematics analyses of robot. The specific relationship between Forward kinematics and Inverse kinematics was shown in Fig. 2.

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Fig. 2. Forward and Inverse kinematics diagram

3.1 The Forward Kinematics The forward kinematics is used to find the position of the manipulator after the joint positions were given. It is easy to solve forward kinematics solutions once the DH parameters of the robot were known. DH parameters used in this study were listed in Table 1. Table 1. DH parameters of KUKA KR10 Robot Linki

ai−1 (mm)

α i−1 (°)

di (mm)

θi

JRM (°)

RLS (°/s)

1

150

90

450

θ1

−170–170

220

2

610

180

0

θ2

−185–65

210

3

20

−90

0

θ3

−137–163

270

4

0

90

660

θ4

−185–185

381

5

0

−90

0

θ5

−120–120

311

6

0

0

80

θ6

−350–350

492

The Cartesian position and orientation of the end effector were defined as: ⎤ ⎡ T11 T12 T13 px ⎢ T21 T22 T23 py ⎥ ⎥ T60 = T10 T21 T32 T43 T54 T65 = ⎢ ⎣ T31 T32 T33 pz ⎦ 0

0

(1)

0 1

Where: Px , Py , Pz are the position of the wrist center. The transformation matrix of n−1 axis and n-axis were expressed as: ⎤⎡ ⎤ ⎡ 1 0 0 an cosθn −sinθn 0 0 ⎢ sinθn cosθn 0 0 ⎥⎢ 0 cosαn −sinαn 0 ⎥ ⎥⎢ ⎥ Tnn0 =⎢ Tnn−1 = Tnn−1 0 ⎣ 0 0 1 dn ⎦⎣ 0 sinαn cosαn 0 ⎦ 0 0 0 1 0 0 0 1 ⎡ ⎤ cosθn −sinθn cosαn sinθn sinαn an cosθn ⎢ sinθn cosθn cosαn −cosθn sinαn an sinθn ⎥ ⎥ =⎢ ⎣ 0 sinαn cosαn dn ⎦ 0 0 0 1

(2)

Substituting Eq. (2) into Eq. (1) and combining with DH parameters, the Forward kinematics solution of the robot will be obtained.

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3.2 The Inverse Kinematics The Levenberg-Marquardt (LM) method was used to solve the inverse problem, LM method can avoid the phenomenon of iterative divergence effectively and ensure JT J is a positive definite matrix. The Forward kinematics is: x = f (θ )

(3)

Jacobian of the Forward kinematics is [10]: J (θ )=

∂x ∂f (x) = ∂θ ∂θ

(4)

The standard equation of LM algorithm is: q = q0 + dq −1  dq = J T ∗ J + μ*IJ T ∗J ∗ J T *e

(5)

Where: q is the joint angle, μ is the damping coefficient; I is the identity matrix, e is the adjacent pose difference. In order to obtain the minimum norm solution, the iteration conditions is: enew 2 < elast 2 ≤ tol

(6)

The value of tol is 1 * 10−5 . In this paper, Matlab was used for calculation. The comparison of the calculated position and the actual position were as follow (Table 2): Table 2. End effector position comparison Point/m

1

2

3

4

Expected

[0 0 0]

[0.14837 −0.25813 −0.15765]

[0.3012 0 0]

[0.46588 0.25933 −0.14824]

Calculation

[0 0 0]

[0.14838 −0.25811 −0.15764]

[0.3011 0 0]

[0.46588 0.25931 −0.14823]

4 Workspace Simulation The set of all the manipulator positions of the end effector reached by different joint movements was called the industrial robot reachable workspace, which was an important kinematic index to measure the working ability of industrial robot. The main tasks of space robot are capturing and releasing the target within the workspace is essential to accomplish the task. In this paper, Monte Carlo method was used to simulate the workspace of the ground fixed base industrial robot. The principle formula is as follows: W = {ω(q) : q ∈ Q} ⊂ R3 qi,min ≤ qi ≤ qimax

(7)

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Where: W is the working space; q is the generalized joint variable; ω(q) is a generalized joint variable function; Q is the joint space; R3 is three-dimensional space; i is the ith generalized joint. A probability model was established to simulate the working area of the robot by grasping the geometric quantity and geometric characteristics of the robot motion based on the model established by the manipulator and the range of joint motion. The schematic diagram was shown in Fig. 3. The brief steps of obtaining the workspace of the manipulator by Monte Carlo method in MATLAB were as follows: Writing the Forward kinematics equation function and extracting the position vector(Px ,Py ,Pz ); The random values of joints were generated by random function R and θ i = θ imin + (θ imax − θ imin ) × R and (n,1), where i is the number of joints, imin ~ imax is the range of joint angle, n is the particle quantity; Combining the generated random joint angle value with the position vector and generating point cloud map of workspace using MATLAB.

Fig. 3. The principle of workspace simulation

The workspace of the manipulator with the capacity of 10 W and 50 W points were shown in Fig. 4. Figure 4(a) showed that the distribution of random points in manipulator workspace simulation was uneven, especially the boundary points were sparse because of the nonlinear mapping from joint space to workspace with the capacity of random points of 10 W. Figure 4(b) showed that the density of random points on the boundary of workspace was increased, and the boundary of simulation was closer to the real boundary of workspace by increasing the capacity of random points to 50 W. Figure 4(c) showed that the distribution of the particle density. The first diagram showed that points were extremely dense in the green region along the XY axis (−0.5, 0.5), the red region was sparse around it. The second diagram had a good representation of the boundary working region points. The uneven distribution of random points would cause large local errors in workspace simulation. Therefore, it was very important to improve the boundary distribution of random points. By improving the distribution of random points and changing the boundary distribution probability of random points, the working domain of simulation could be improved. In this paper, the number of points was increased to restore the real working domain. This method was more direct and effective under the condition of ensuring computing power. The simulation of robot workspace was mostly used for the reference of structure analysis, which was helpful to the robot design.

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Fig. 4. The manipulator workspace of KUKA KR10 (a) 10 W points. (b) 50 W points (c) Comparison of XOY view

5 Trajectory Planning 5.1 Introduction to Worktable The platform is mainly composed of KUKA KR10 and the worktable, which mainly includes the feeding platform, feeding well, unloading platform, transmission equipment, stamping equipment, quality testing equipment, various sensors control units and driving units, as shown in Fig. 5. The worktable can complete the simulation of the whole material delivery process. This paper mainly carried on the trajectory planning to the feeding and unloading parts.

Fig. 5. Worktable overview

5.2 Trajectory Planning Process In this paper, feeding and unloading trajectory planning was carried out in joint space. The main process was shown in Fig. 6. The first step was to set the starting point, via point and end point position parameters of the robot movement, and then the position parameters of the moving point were converted into joint angle through IK. Finally, the

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motion trajectory was generated by interpolation processing of each point. The actual control point and simulated trajectory were shown in Fig. 7.

Fig. 6. Trajectory planning in joint space

Fig. 7. Feeding and unloading Trajectory (a) worktable (b) Simulated trajectory

The inverse solutions in Sect. 3.2 were applied to the trajectory planning of loading and unloading process. The seventh degree polynomial and five term polynomial interpolation method were used to plan the feeding and unloading trajectory respectively. At last, the angular position, angular velocity and angular acceleration of six joint angles were obtained. The results were shown in Fig. 8. Compared to position parameters, there were significant differences between the speed parameters analyzed by two methods, showed in (a), (b), (d), (e) and this differences could be seen more intuitively in the acceleration diagram (c) and (f).

Fig. 8. Joint angle state with polynomial of degree seven and five (a) (d) angular position, (b) (e) angular velocity, (c) (f) angular acceleration

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As shown in Fig. 9. The angular acceleration of the robot first joint processed by different interpolation were compared. In this sketch, Runge phenomenon occurs in interpolation curve. Fifth polynomial interpolation trajectory was smoother than the seventh polynomial interpolation trajectory [11].

Fig. 9. Comparison of angular acceleration between two interpolation methods (taking joint angle 1 as an example)

6 Conclusions Kinematics simulation and trajectory planning based on KUKA KR10 6-DOF industrial robot were researched in this article. The accuracy of the model was verified by the kinematics simulation. The workspace was drawn based on Monte Carlo method, which effectively proved the rationality of the structure. The trajectory planning of different algorithms were carried out, and the effectiveness of the inverse solution was verified. All these results provided a basic study to the subsequent motion control research of industrial robot. Future research would expand the application range of the manipulator, such as using robots for gluing and welding, which means higher requirements for the control accuracy of the manipulator. With the increasing of computer computing power, it is possible to achieve higher accuracy and faster IK on trajectory planning, such as swarm intelligence algorithms, artificial neural networks, etc.

References 1. Ji, S.J., Liu, Z.Y., Zhang, L., et al.: Research status and development trends of industrial robot. Int. Core J. Eng. 7(4), 373–376 (2021) 2. Gao, H.: Development status and trend of industrial robot in China. Appl. Sci. Innov. Res. 5(2), 49–54 (2021) 3. Denavit, J., Hartenberg, R.S.: A kinematic notation for lower-pair mechanisms based on matrices. ASME J. Appl. Mech 22(2), 215–221 (1955) 4. Kivelä, T., Mattila, J., Puura, J.: A generic method to optimize a redundant serial robotic. Autom. Construct. Manipulat. Struct. 81, 172–179 (2017)

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5. Peidró, A., Reinoso, O., Gil, A., et al.: An improved Monte Carlo method based on Gaussian growth to calculate the workspace of robots. Eng. Appl. Artif. Intell. 64, 197–207 (2017) 6. Rastegarl, J., Perel, D.: Generation of manipulator workspace boundary geometry using the Monte Carlo method and interactive computer graphics. ASME J. Mech. Des. 112(3), 452–454 (1990) 7. Zhang, Q.S., Duan, S.C., Xia, R.: Workspace analysis and simulation of humanoid manipulator based on MATLAB. Mech. Drive 44(12), 99–105 (2020) 8. Biagiotti, L., Melchiorri, C.: Trajectory Planning for Automatic Machines and Robots. Springer, Heidelberg (2008). https://doi.org/10.1007/978-3-540-85629-0 9. Li, G., Zhu, W., Dong, H., Ke, Y.: A method for robot placement optimization based on twodimensional manifold in joint space. Robot. Comput. Integrat. Manufact. 67, 102002 (2021). https://doi.org/10.1016/j.rcim.2020.102002 10. Somasundar, A., Yedukondalu, G.: Robotic path planning and simulation by Jacobian inverse for industrial applications. Procedia Comput. Sci. 133, 338–347 (2018) 11. Fornberg, B., Zuev, J.: The Runge phenomenon and spatially variable shape parameters in RBF interpolation. Comput. Math. Appl. 54, 379–398 (2007)

A Screening Method for Dangerous Models of 3D Printed Bionic Artificial Vertebral Bodies Finite Element Analysis Peng Li1 , Bowen Ren2 , Kun Hu3 , Zongwen Yang3 , Zhenchuan Han4 , Guifeng Zhang1(B) , and Bo Zhao5(B) 1 State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, CAS,

Beijing, China [email protected] 2 Department of Orthopaedics, Chinese PLA General Hospital, Beijing, China 3 School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China 4 Department of Orthopedics, The Fourth Medical Center, Chinese PLA General Hospital, Beijing, China 5 Beijing Biosis Healing Biological Technology Co., Ltd., Beijing, China [email protected]

Abstract. Spinal tumors can occur in or around the spine and may cause defects in the anterior column of the vertebral body, spinal instability, nerve and spinal cord damage, and other symptoms. Benefiting from the rapid development of spinal internal fixation and reconstruction instruments, total spine en bloc resection is gradually being accepted by more and more spinal surgeons. In recent years, with the increasing maturity of 3D printing technology, 3D printing artificial vertebral bodies have been used clinically to reconstruct the spine. In this study, a reliable 3D printed artificial vertebral body screening program is provided, and the finite element analysis results are used to improve the artificial vertebral body design to save expensive economic and time costs. Keywords: Finite element analysis · Bionic artificial vertebral body · Spinal tumors · 3D printed · Cervical body prosthesis

1 Introduction Spinal tumors can occur in the internal or surrounding tissues of the spine, or they can spread to the vertebral body or paravertebral tissues due to the metastasis of malignant tumors. They can be divided into primary spinal tumors and spinal metastases according to their tumor sources. Primary spinal tumors account for approximately 6.6%–8.8% of bone tumors in the body, and more than 90% of spinal tumors are of metastatic origin [1]. Spinal tumors may lead to anterior vertebral column defects, spinal instability, nerve and spinal cord damage, and other symptoms [2], which not only bring physical and mental damage to the patient, but also bring huge economic burden and psychological pressure © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 332–346, 2022. https://doi.org/10.1007/978-981-19-1673-1_49

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to the patient’s family. Although the non-surgical treatment of spinal tumors has made considerable progress, the vast majority of spinal tumors currently advocate surgical treatment has reached a basic consensus [3]. Early surgical treatment can effectively improve the quality of life of patients and prolong the survival time of patients [4–6]. Benefiting from the rapid development of spinal internal fixation and reconstruction instruments, TOTAL ENBLOC SPONDYLECTOMY is gradually accepted by more and more spine surgeons-that is, the entire vertebral body and the rear appendages are removed to achieve complete removal of the tumor purpose. At present, TES surgery is mainly suitable for benign aggressive and malignant primary spinal tumors and solitary metastases with well-controlled lesions [1, 7, 8]. Although studies have shown that en bloc resection is associated with a low recurrence rate and longer survival time [9, 10], TES surgery will cause the continuity of the spine to be interrupted, and restoring the height and mechanical stability of the vertebral body is still a clinical problem. In 1969, Hamid [11] first reported the use of artificial vertebral bodies to fill the defects after resection of diseased vertebral bodies, and good clinical results were obtained. Since then, artificial vertebral body technology has developed rapidly, and it has been favored by clinicians because of its excellent filling and supporting functions. In 1986, Harms first used titanium mesh to reconstruct the anterior spine structure to avoid complications such as fractures and collapses after transplantation of the ilium, fibula, and tibia. However, follow-up of a large number of cases showed that due to the cutting effect of the titanium mesh, the sinking rate is high, and long-term use will result in loss of intervertebral space height and recurrence of neurological symptoms [12–15]. In recent years, with the increasing maturity of 3D printing technology, successful cases of 3D printing artificial vertebral bodies used in clinics to reconstruct the stability of the spine have been reported from time to time [16, 17]. Compared with the traditional titanium mesh, 3D printing artificial vertebral body helps to restore the anatomical position of the spine, has better biocompatibility, larger contact area and other advantages. Because of its unique advantages, it can effectively solve the problems caused by traditional materials, and its innovative potential and application prospects are generally favored by people in the industry. This article mainly uses medical grade titanium alloy powder that meets FDA standards, and uses electron beam melting technology to manufacture a fusion device with a bionic human cancellous bone trabecular structure. The device is topologically formed by a dodecahedral unit cell structure. There are two main advantages: one is that osteoblasts are easily anchored on the titanium alloy metal surface for osseo integration; on the other hand, the bionic porous provides a scaffold, which is conducive to osteogenesis and deep bone fusion. Finite element analysis can simulate the structure of the human spine with computer assistance, and calculate the pressure and stress of each element [18, 19]. Finite element analysis has unparalleled superiority in the research of spinal diseases and implant biomechanics [20], but its application in perfecting the design of 3D printed artificial vertebral body products has not yet been explored. This article intends to propose a finite element analysis-based screening plan for dangerous models of artificial vertebrae, and to judge the rationality of the design of 3D printed bionic artificial vertebrae. According to the finite element analysis results, the artificial vertebral body design is optimized

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to ensure the matching degree of the artificial vertebral body, shorten the development cycle, and reduce the research cost.

2 Methods and Materials 2.1 Selection Scheme Refer to YY/T0959-2014 “Test Method for Mechanical Performance of Spinal Implants Interbody Fusion Cage”, the 3D printed titanium alloy cervical vertebra prosthesis and thoracolumbar vertebra prosthesis were respectively subjected to compression, compression-shear and torsion under three loads Static analysis. By comparing the von Mises stress of each model of cervical vertebra prosthesis and thoracolumbar vertebra prosthesis, it is determined that the model with the largest von Mises stress is the dangerous model. 2.2 Initial Screening Programme According to the theory of material mechanics, when objects of different cross-sections are compressed by the same axial force, the smaller the cross-sectional area of the object perpendicular to the axis, the greater the stress on the object, so that the 240 ZTC cervical vertebra prosthesis specifications and models and 600 One ZTTL thoracolumbar vertebral body prosthesis specification model completed the preliminary screening of dangerous models. 2.3 Secondary Screening Programme For the pre-screened vertebral prosthesis with the smallest section length L and width W, the finite element method is used to simulate the stress of the vertebral prosthesis with the same section size and different heights under compression, compression-shear and torsion loads. Distribution, to investigate the influence of the height of the vertebral body H on the maximum stress of the vertebral body prosthesis when subjected to compression, compression-shear and torsion loads. By examining the relationship between the maximum von Mises stress and height on the vertebral body prosthesis, the dangerous models of the ZTC cervical vertebra prosthesis and ZTTL thoracolumbar vertebral prosthesis were secondly screened, and finally the most dangerous vertebral body was found by finite element analysis model. 2.4 Geometric Model Three geometric models of vertebral body prostheses with the same cross-sectional size, different heights (H = 25 mm, H = 50 mm, H = 80 mm), and d = 8° were selected to implement the secondary screening program. The vertebral body prosthesis is formed by 3D printing of titanium alloy. The top ring, the bottom ring and the vertebral body frame are 3D printed titanium alloy, and the vertebral body filling part is a titanium alloy 3D printed mesh structure, as shown in Fig. 1.

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Fig. 1. Geometric model of vertebral body prosthesis (same interface size, d = 8°)

2.5 Material Properties The top and bottom rings of the vertebral body and the vertebral body frame are solid structures formed by 3D printing titanium alloy materials, and the filling part of the vertebral body is composed of 3D printed titanium alloy mesh porous structures (Fig. 2(a)). The smallest repeatable structure is called the equivalent volume element (Representative Volume Element, RVE), as shown in Fig. 2(b) and 2(c). The shape of the RVE in the three axial directions is exactly the same. Size = 2 mm. The equivalent material parameters of the 3D printed mesh porous structure, including the equivalent elastic modulus and equivalent Poisson’s ratio, use the Material Designer module in ANSYS Workbench to import the RVE structure of the 3D printed titanium alloy mesh porous structure, and impose periodic boundaries Under the conditions, the equivalent material parameters of the reticulated porous structure formed by the repeated arrangement of the RVE structure are obtained.

Fig. 2. 3D printing mesh porous structure

Before performing the finite element calculation of the equivalent material parameters of the RVE structure, it is necessary to conduct a convergence analysis of the meshing quality, and use three meshing methods (Table 1) to mesh the model. The equivalent elastic modulus E, shear modulus G and Poisson’s ratio nu of the network porous structure composed of the repeated arrangement of RVE structures under the three grid division methods. If the difference of the equivalent material parameter results is less than or equal to 3%, the mesh will converge. In order to verify the effectiveness of the equivalent material parameters of the net-like porous structure formed by the repeated

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arrangement of RVE structures, 2 * 2 * 2 RVE structures and 3 * 3 * 3 RVE structures are used as the new RVE structures, and the repeated arrangements form two new RVE structures. The net-like porous structure is applied with periodic boundary conditions, and the equivalent material parameters of the two net-like porous materials composed of 2 * 2 * 2 RVE structure and 3 * 3 * 3 RVE structure are obtained. Table 1. Unit size of different meshing methods Meshing method

Unit size, mm

Coarse grid

0.08

Medium grid

0.05

Fine mesh

0.03

2.6 Grid Division and Convergence Analysis Since the meshing method affects the computational accuracy of the finite element method, a convergence analysis of the meshing method is necessary, followed by finite element analysis of the compression, compression-shear, and torsion forces applied to the vertebral prosthesis. Considering that the volume of the upper and lower sample fixtures is relatively large compared to the top and bottom rings and the cone frame, and considering the balance of calculation accuracy and calculation time, when dividing the grid, the top and bottom circles The mesh size of the ring, the vertebral body frame, and the vertebral body filling part is set to be smaller than the mesh size of the specimen fixture. Three meshing methods (Table 2) are used to mesh the model, and calculations are performed according to the applied loads and constraints. If the difference between the maximum displacement of the model and the maximum von Mises stress is less than or equal to 5%, the mesh converges. Table 2. Dimensions of each part of the model with different meshing methods Meshing method

Unit size, mm Top ring

Bottom ring

Vertebral frame

Vertebral body filler

Upper and lower samples furniture

Coarse grid

1.2

1.2

1.2

1.2

2.4

Medium grid

0.75

0.75

0.75

0.75

1.5

0.5

0.5

0.5

1.0

Fine mesh 0.5

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2.7 Load and Boundary Conditions Refer to YY/T 0959-2014 “Test Method for Mechanical Properties of Spinal Implant Interbody Fusion Cage” to simulate the load loading of vertebral body prosthesis under compression, compression-shear and torsion. When simulating compression, a fixed constraint is imposed on the lower surface of the lower sample holder, and the center of the upper surface of the upper sample holder applies a compressive load of 100 N in the direction of the axis of the vertebral body; The body frame and the filling part of the vertebral body are set as binding contact, and the vertebral body and the upper and lower sample holders are set as sliding friction contact, and the friction coefficient is 0.2. When simulating compression-shearing, a fixed constraint is applied to the lower surface of the lower sample holder, and the center of the upper surface of the upper sample holder applies a compressive shear load of 141.42 N at an angle of 45° to the axis of the vertebral body; round the top and bottom ring and the vertebral body filling part, and between the vertebral body frame and the vertebral body filling part are set as binding contact, and the vertebral body and the upper and lower sample clamps are set as non-separable sliding contact. When simulating torsion analysis, a fixed constraint is applied to the lower surface of the lower sample holder, and a torque of 1000 N is applied to the upper sample holder of the model; between the top and bottom rings and the filling part of the vertebral body, as well as the vertebral body frame and the vertebral body filling The parts are set to bind contact, the upper and lower contact surfaces of the vertebral body and the upper and lower sample holders are set to bind contact, and the vertebral body and the side surfaces of the upper and lower sample holders are set as non-separable sliding contact.

3 Results 3.1 Initial Screening Programme From the cross-sectional dimensions of 240 ZTC cervical vertebra prosthesis specifications and 600 ZTTL thoracolumbar vertebra prosthesis specifications, the 120 ZTC cervical prostheses and 60 ZTTLs with the smallest cross-sectional length L and width W were preliminarily screened out. Dangerous model of thoracolumbar vertebral body prosthesis. 3.2 Validation of Material Parameters The top and bottom rings of the vertebral body and the vertebral body frame are solid structures formed by 3D printing of titanium alloy materials. Therefore, the parameters of the three parts of the vertebral body can adopt the material parameters of titanium alloy. The filling part of the vertebral body is composed of 3D printed titanium alloy mesh porous structure, which is composed of RVE arrangement. The shape of the RVE in the three axial directions is exactly the same, and the side length dimension = 2 mm. Therefore, the material parameters of the filling part of the vertebral body cannot directly adopt the material parameters of titanium alloy. Since the shape of the RVE structure in the three axial directions is exactly the same, it is calculated that the equivalent material

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parameters of the reticulated porous structure composed of the RVE structure have a very small difference in the three directions. However, due to the elastic modulus E, The shear modulus and Poisson’s ratio nu do not satisfy the relationship between the three isotropic materials (Eq. 1), so in the subsequent finite element calculations, the network porous structure composed of the repeated arrangement of the RVE structure is regarded as Orthotropic materials. G = E/[2 ∗ (I + nu)]

(1)

The parameters and results of the grid convergence analysis are shown in Table 3. The errors of the equivalent elastic modulus and equivalent shear modulus calculated by the medium meshing method and the coarse meshing method are both greater than 3%, indicating that the coarse meshing method does not converge. The errors of the equivalent elastic modulus and equivalent shear modulus calculated by the fine meshing method and the medium meshing method are both less than 2%, and the equivalent Poisson’s ratio errors are both less than 1%, indicating the medium meshing method It is convergent. Table 3. Parameters for mesh convergence analysis of RVE structures Meshing method

Coarse grid

Medium grid

Fine mesh

Number of nodes

17240

45986

169711

Number of units

8257

25357

125495

Unit type

Tetrahedron

Tetrahedron

Tetrahedron

38.651

37.397

36.753

Equivalent

E1

Elastic modulus

E2

38.68

37.415

36.752

MPa

E3

39.696

37.429

36.754

Elastic modulus

E1

/

3.244

1.722

Error

E2

/

3.270

1.772

(%)

E3

/

3.274

1.803

Equivalent

G12

36.644

35.524

34.941

Shear modulus

G23

36.581

35.474

34.928

MPa

G31

36.619

35.521

34.935

Shear modulus

G12

/

3.056

0.01641144

Error

G23

/

3.0262

0.015391554

(%)

G31

/

2.9984

0.016497283

Equivalent Poisson’s ratio

Poisson’s ratio error

nu12

0.48755

0.48798

0.48804

nu13

0.48711

0.48148

0.48766

nu23

0.48674

0.48713

0.48769

nu12

/

0.0882

−0.000123

nu13

/

0.0766

−0.0003692

nu23

/

0.0802

−0.0011496

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By calculating RVE, 2 * 2 * 2 RVE and 3 * 3 * 3 RVE, the equivalent elastic modulus of the three network porous structures formed by repeated arrangement, as shown in Table 4, equivalent shear modulus and equivalent Poisson The ratio difference is very small, and the errors are all less than 0.06%. Therefore, the material parameters of the filling part of the vertebral body can adopt the equivalent material parameters of the mesh porous structure formed by the repeated arrangement of the RVE structure. Table 4. Material parameters Part name

Vertebral body filling part

Material name 0.08

Titanium alloy 3D printing mesh structure

Equivalent

E1

36.735

Elastic Modulus

E2

36.752

MPa

E3

36.754

Equivalent

G12

34.941

Shear modulus

G23

34.928

MPa

G31

34.935

Equivalent Poisson’s ratio

nu12

0.48804

nu13

0.48766

nu23

0.48769

3.3 Grid Division and Convergence Analysis The displacement error calculated by the medium meshing method and the coarse meshing method is 26.86%, and the stress error is 19.19%, indicating that the coarse meshing method does not converge, as shown in Table 5. The displacement error calculated by the fine meshing method and the medium meshing method is 4.33%, and the stress error is 1.90%, indicating that the medium meshing method is convergent. However, considering that there are some small surfaces on the cone, in order to obtain a more accurate stress distribution, it is necessary to set a smaller mesh size when meshing these small surfaces. Therefore, the mesh is divided in the subsequent calculations. The method uses a finer meshing method than the medium meshing method that has been verified to be convergent, that is, the unit size of the top and bottom ring, the cone frame, and the cone filling part is 0.5 mm, and the unit size of the upper and lower sample holders is 1.0 mm.

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Table 5. Parameters for mesh convergence analysis of 3D printed mesh structures of titanium alloys Meshing method

Number of units

Number of nodes

Grid type

Maximum displace-ment, mm

Displac-ement error (%)

Maximum von Mises stress, MPa

Stress error (%)

Coarse grid

28343

106514

Hexa-hedron

0.0024216

\

11.462

\

Medium grid

88554

341290

Hexa-hedro

0.0017711

26.86

9.2623

19.19

Fine mesh

258844

992257

Hexa-hedro

0.0016944

4.33

9.4382

1.90

3.4 Secondary Screening Programme The von Mises stress distribution of three different heights of vertebral body prosthesis under compression, compression-shear and torsion is shown in the Figs. 3, 4 and 5. The maximum von Mises stress of the vertebral body under compression hardly changes with the increase of the height of the vertebral body; as the height of the vertebral body increases, the maximum value of the von Mises stress of the vertebral body under compression-shear and torsion also changes. Increase accordingly. The von Mises stress calculation results of three heights of vertebral bodies under compression, compressionshear and torsion. Among them, the vertebral body with H = 80 mm has the largest von Mises stress when subjected to compression-shearing, which is 85.476 MPa. From the distribution of the maximum value of von Mises stress in Table 6, the results of the secondary screening can be seen in Tables 7 and 8.

Fig. 3. Von Mises stress distribution when the vertebral body is compressed

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Fig. 4. Von Mises stress distribution of the vertebral body under compression-shear

Fig. 5. Von Mises stress distribution when the vertebral body is twisted

Table 6. Calculated results of von Mises stress for three heights of vertebral bodies Height, von Mises maximum stress, MPa mm Compression Compression-shear Twist 25

9.4382

62.001

9.5139

50

9.9561

59.88

19.288

80

9.5521

85.476

38.256

Table 7. ZTC type cervical vertebra body prosthesis dangerous model (secondary screening) Specification model

W mm/L mm/d° (W 1mm/L1mm)

H mm

ZTC-040

12/10/0° (9/7)

90

ZTC-120

12/10/8° (9/7)

90

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W mm/L mm/d° (W 1mm/L1mm)

H mm

ZTTL-020

18/12/0° (14.4/8.4)

120

ZTTL-060

18/12/8° (14.4/8.4)

120

3.5 Dangerous Model Selection The von Mises stress distribution results of the four types of vertebral prostheses under compression, compression-shear and torsion are shown in Figs. 3, 4 and 5. It can be seen from Table 9 that for cervical vertebral body prostheses, the vertebral body of model ZTC-120 has the largest von Mises stress when subjected to a compression load of 4000 N, which is 987.15 MPa, which is judged as a dangerous model of cervical vertebral body prosthesis. For thoracolumbar vertebral body prostheses, the vertebral body of model ZTTL-060 has the highest von Mises stress when subjected to a 4000 N compression load, which is 597.65 MPa, which is judged to be a dangerous model of thoracolumbar vertebral body prosthesis. Table 9. Selection results Model

von Mises Maximum stress, MPa

Remark

Compression

Compression-shear

Twist

ZTC-040

962.29

761.13

685.09

ZTC-120

987.15

807.87

674.89

ZTTL-020

543.69

542.84

297.59

ZTTL-060

597.65

502.18

282.84

Dangerous model Dangerous model

3.6 Discussion TOTAL ENBLOC SPONDYLECTOMY is currently mainly used for benign aggressive and malignant primary spinal tumors and solitary metastases with well-controlled lesions [7, 8]. Therefore, various types of artificial vertebral body prostheses continue to appear and are gradually used in clinical work. Among them, titanium mesh cage (TMC) and artificial vertebral body (AVB) have become two types of prostheses commonly used clinically due to their good filling and supporting effects. However, as the number of patients increases and the follow-up time increases, more and more implant-related complications appear. In order to overcome the shortcomings of these intervertebral prostheses, we developed a 3D printed bionic artificial vertebral body made of Ti-6Al-4V

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alloy powder. The details of the design process were reported in our previous study [21]. However, due to lack of sufficient evidence, we did not fully discuss its biomechanical effectiveness in this article. Finite element analysis is a method of finding approximate values based on computer technology, which was originally used in engineering mechanics. Finite element analysis can automatically provide three-dimensional images through a computer, and at the same time, different experimental conditions can be given, repeated simulation experiment analysis, and complete and diverse result data can be quickly obtained, so as to discover potential problems before surgery and study the stress of the model surface and internal area - Changes in strain state. All of these can reduce deviations in selecting suitable implants, thereby saving part of the operation time due to problems such as implant selection during the operation, and at the same time, the postoperative effects can be effectively evaluated after the operation. With the continuous development of computer and imaging technology, finite element analysis can not only be used well in orthopedic biomechanics research, but also can become the most effective tool for simulating spinal pathology with the aid of computers [22, 23]. Due to the complexity of object geometry and mechanical actions, finite element analysis can predict mechanical parameters that cannot be measured by mechanical experiments [24]. In this study, we will use finite element research to analyze the biomechanics of artificial vertebral bodies and provide model mechanics experiments basis. Discover the weak points of the artificial vertebral body and optimize the product design to ensure the matching degree of the artificial vertebral body, shorten the development cycle, and reduce the research cost. As shown in Table 6, the maximum von Mises stress of the vertebral body under compression hardly changes with the increase of the height of the vertebral body. As the height of the vertebral body increases, the maximum von Mises stress of the vertebral body when subjected to compression-shear and torsion also increases. Among them, the vertebral body with H = 80 mm has the largest von Mises stress when subjected to compressionshearing, which is 85.476 MPa. In the preliminary screening, four geometric models of ZTC-040, ZTC-120, ZTTL-020 and ZTTL-060 were selected for secondary screening. It can be seen from Table 9 that for cervical vertebral body prostheses, the vertebral body of model ZTC-120 has the largest von Mises stress when subjected to a compression load of 4000 N, which is 987.15 MPa, which is judged as a dangerous model for cervical vertebral body prostheses. For thoracolumbar vertebral body prostheses, the vertebral body of model ZTTL-060 has the highest von Mises stress when subjected to a 4000 N compression load, which is 597.65 MPa, which is judged as a dangerous model of thoracolumbar vertebral body prosthesis. The emergence of electron beam melting technology and laser melting technology created a precedent for 3D printing with metal powder. 3D printing technology is more suitable than traditional manufacturing methods for the production of products with complex shapes and structures and small batches of customized products. It has great potential in the reconstruction of self-stabilizing prostheses after total spine resection of spinal tumors. Benazzo et al. [25] demonstrated that porous titanium alloy implants can induce osteogenic differentiation of mesenchymal stem cells without additional osteogenic factors as a medium. Li P et al. [21] first designed and manufactured a new type of 3D printed titanium alloy bionic cone with internal porous. This kind of prosthetic

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implant combined with porous bionic technology enables the design of the internal microporous structure of the implant, which has good biocompatibility, is conducive to cell adhesion and proliferation, and promotes the firm combination of living bone and implanted prosthesis Together. In the spine, the non-uniformity of the prosthesis material and geometry will affect the finite element prediction results, and the mesh convergence is particularly important. The calculation accuracy of the finite element method is related to the grid division method. The artificial vertebral body filling part is a mesh porous structure composed of repeated arrangements of RVE. Therefore, the quality of the grid division should be checked before the finite element calculation of the equivalent material parameters of the RVE structure. Convergence analysis. Since the shape of the RVE structure in the three axial directions is exactly the same, it is calculated that the equivalent material parameters of the reticulated porous structure composed of the RVE structure have a very small difference in the three directions. However, due to the elastic modulus E, The shear modulus and Poisson’s ratio nu do not satisfy the relationship between the three isotropic materials (Eq. 1), so in the subsequent finite element calculations, the network porous structure composed of the repeated arrangement of the RVE structure is regarded as Orthotropic materials. Considering that there are some small surfaces on the RVE structure, when meshing these small surfaces, it is necessary to set a finer mesh size to obtain a more accurate stress distribution. Using 2 * 2 * 2 RVE structure and 3 * 3 * 3 RVE structure as the new RVE structure (Fig. 6), two new network porous structures are formed by repeated arrangement, and periodic boundary conditions are applied to them, verifying that the RVE The effectiveness of the equivalent material parameters of the net-like porous structure formed by the repeated arrangement of the structure.

Fig. 6. Two new RVE structures

Limitations: The current finite element research is still limited to the effect of a single load, especially the vertical load, and the spine conditions are mostly dynamic, so it is impossible to fully simulate the force of the artificial prosthesis between the spine. The follow-up needs to develop dynamic finite element analysis technology. In addition, there is still a lack of unified specifications for the finite element material properties, loads, and models of the spine, so there are still defects in the finite element analysis. Due to the above factors, there are still some differences between the finite element analysis simulation research and the actual biomechanics experiment. There are still

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many research improvements in the finite element analysis in the field of optimizing the artificial vertebral body design.

4 Conclusion This study provides a reliable 3D printed artificial vertebral body screening program. Using finite element analysis, the 240 ZTC cervical vertebra prosthesis specifications and 600 ZTTL thoracolumbar vertebra prosthesis specifications were screened twice to obtain the dangerous models of this batch of vertebral prostheses and their von Mises stress distribution. Based on the results of finite element analysis, the artificial vertebral body design is improved to save expensive economic and time costs. It is worth noting that although finite element analysis has outstanding advantages over traditional mechanical experiments in terms of optimization design, it still cannot completely replace traditional biomechanical research. In the future, in vivo and in vitro experiments are still needed to verify our findings and conclusions.

References 1. Harrop, J.S., Schmidt, M.H., Boriani, S., Shaffrey, C.I.: Aggressive “benign” primary spine neoplasms: osteoblastoma, aneurysmal bone cyst, and giant cell tumor. Spine 34, S39-47 (2009) 2. Dreimann, M., Viezens, L., Hoffmann, M., Eicker, S.O.: Retrospective feasibility analysis of modified posterior partial vertebrectomy with 360-degree decompression in destructive thoracic spondylodiscitis. Acta Neurochir. 157(9), 1611–1618 (2015). https://doi.org/10.1007/ s00701-015-2507-4 3. Dea, N., Gokaslan, Z., Choi, D., Fisher, C.: Spine Oncology - primary spine tumors. Neurosurgery 80, S124–S130 (2017) 4. Mukherjee, D., Chaichana, K.L., Parker, S.L., Gokaslan, Z.L., Mcgirt, M.J.: Association of surgical resection and survival in patients with malignant primary osseous spinal neoplasms from the Surveillance, Epidemiology, and End Results (SEER) database. Eur. Spine J. 22, 1375–1382 (2013) 5. Boriani, S., Gasbarrini, A., Bandiera, S., Ghermandi, R., Ran, L.: En bloc resections in the spine: the experience of 220 patients during 25 years. World Neurosurg. 98, 217–229 (2017) 6. Boriani, S.: En bloc resection in the spine: a procedure of surgical oncology. J. Spine Surg. 4, 668–676 (2018) 7. Sciubba, D.M., et al.: Total en bloc spondylectomy for locally aggressive and primary malignant tumors of the lumbar spine. Eur. Spine J. 25(12), 4080–4087 (2016). https://doi.org/10. 1007/s00586-016-4641-y 8. Luzzati, A.D., Shah, S., Gagliano, F., Perrucchini, G., Scotto, G., Alloisio, M.: Multilevel en bloc spondylectomy for tumors of the thoracic and lumbar spine is challenging but rewarding. Clin. Orthop. Relat. Res. 473, 858–867 (2015) 9. Kato, S., Murakami, H., Demura, S., et al.: Patient-reported outcome and quality of life after total en bloc spondylectomy for a primary spinal tumour. Bone Joint J. 96(b), 1693–1698 (2014) 10. Amendola, L., Cappuccio, M., De Iure, F., Bandiera, S., Gasbarrini, A., Boriani, S.: En bloc resections for primary spinal tumors in 20 years of experience: effectiveness and safety. Spine J. Official J. North Am. Spine Soc. 14, 2608–2617 (2014)

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11. Hamdi, F.A.: Prosthesis for an excised lumbar vertebra: a preliminary report. Can. Med. Assoc. J. 100, 576–580 (1969) 12. Grob, D., Daehn, S., Mannion, A.F.: Titanium mesh cages (TMC) in spine surgery. Eur. Spine J. 14, 211–221 (2005) 13. Darryl, L., Song, Y., Guan, Z., La Marca, F., Park, P.: Radiological outcomes of static vs expandable titanium cages after corpectomy: a retrospective cohort analysis of subsidence. Neurosurgery 72(4), 529–539 (2013) 14. Chen, Y., Chen, D., Guo, Y., et al.: Subsidence of titanium mesh cage: a study based on 300 cases. J. Spinal Disord. Tech. 21, 489–492 (2008) 15. Yoshioka, K., Murakami, H., Demura, S., et al.: Clinical outcome of spinal reconstruction after total en bloc spondylectomy at 3 or more levels. Spine 38, 1511–1516 (2013) 16. Da, I.K.R., Yan, M.N., Zhu, Z.A., Sun, Y.H.: Computer-aided custom-made Hemipelvic prosthesis used in extensive pelvic lesions. J. Arthroplasty 22, 981–986 (2007) 17. Hollander, D.A., Walter, M.V., Wirtz, T., et al.: Structural, mechanical and in vitro characterization of individually structured Ti-6Al-4V produced by direct laser forming. Biomaterials 27, 955–963 (2006) 18. Nikkhoo, M., Hsu, Y.C., Haghpanahi, M., Parnianpour, M., Wang, J.L.: A meta-model analysis of a finite element simulation for defining poroelastic properties of intervertebral discs. Proc. Inst. Mech. Eng. [H] 227, 672 (2013) 19. Schmidt, H., Galbusera, F., Rohlmann, A., Shirazi-Adl, A.: What have we learned from finite element model studies of lumbar intervertebral discs in the past four decades? J. Biomech. 46, 2342–2355 (2013) 20. Kulduk, A., Altun, N.S., Senkoylu, A.: Biomechanical comparison of effects of the Dynesys and Coflex dynamic stabilization systems on range of motion and loading characteristics in the lumbar spine: a finite element study. Int. J. Med. Robot. + Comput. Assist. Surgery Mrcas 11, 400-5 (2016) 21. Li, P., Jiang, W., Yan, J., et al.: A novel 3D printed cage with microporous structure and in vivo fusion function. J. Biomed. Mater. Res. Part A 107(7), 1386–1392 (2019) 22. Shirazi-Adl, S.A., Shrivastava, S.C., Ahmed, A.M.: Stress analysis of the lumbar disc-body unit in compression. A three-dimensional nonlinear finite element study. Spine 9, 120–134 (1984) 23. Biswas, J., Karmakar, S., Majumder, S., Banerjee, P.S., Roychowdhury, A.: Optimization of spinal implant screw for lower vertebra through finite element studies. J. Long Term Eff. Med. Implants 24, 99–108 (2014) 24. Ugur, M.A.: Parametric convergence sensitivity and validation of a finite element model of the human lumbar spine. Comput. Methods Biomech. Biomed. Eng. 14(8), 695–705 (2011) 25. Benazzo, F., Botta, L., Scaffino, M.F., et al.: Trabecular titanium can induce in vitro osteogenic differentiation of human adipose derived stem cells without osteogenic factors. J. Biomed. Mater. Res. Part A 102, 2061–2071 (2014)

Design of Interactive Customization System for Plastic Packaging Printing Wenjie Yang(B) and Xiujie Chen Printing and Packaging Engineering School, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. According to the characteristics of multi variety and small batch production of plastic packaging and printing enterprises, a personalized customer interactive customization system is designed by using a series of Java technology and based on the system architecture of browser/server mode. The workflow of personalized interactive customization is given, the bill of material (BOM) of plastic packaging printing product is defined, the coding mode of product attributes is set, the price of materials in BOM is taken as the objective function, and an optimized enterprise production scheme is given by using genetic algorithm according to the needs of customers. Keywords: Packaging printing · Interactive customization · Genetic algorithm · Java

1 Introduction The main characteristics of packaging printing enterprises are the personalization, multi variety and small batch. Customer customization requires enterprises to be customeroriented, produce on demand, and build a new mode of customer service based on Internet. The application of the interaction concept in food packaging design is analyzed from usability and user experience and emphasizes the “human-centered” design principle [1]. The application of “multi-sensory” concept in packaging design is studied in terms of visual, auditory and tactile senses to make consumers have a satisfactory user experience [2]. The original user willingness data is obtained, and the initial product suitability value is used as the satisfaction index to get the target product using genetic algorithm (GA) [3]. GA is used to realize the personalization of sofa products [4]. The optimal configuration that meets the customer’s personalized demands and relevance of customized product attributes is obtained by using the simulated annealing algorithm [5]. Here the key technologies on the interactive design system for packaging printing enterprise are investigated, in which customer’s demand for interactive customization, enterprise production characteristics and cost factors are considered, and the optimization scheme of interaction customization is calculated by using GA. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 347–351, 2022. https://doi.org/10.1007/978-981-19-1673-1_50

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2 Interaction Customization System Work Flowchart First of all, as shown in Fig. 1,we have established product database, product attribute structure database, BOM, materials database and other enterprise resource databases to support customers to customize their products according to personalized demands,. Product Customization Option

Demand Information Demand Information Database

Product Attribute Database

Product Database

Material Database

BOM Database

Process Database

Genetic Algorithm

Customer

Personalized Order Generation

Enterprise Design And Production Specifications And Standards

Personalized Order

Fig. 1. Work flowchart of interaction customization system

Secondly, the customer logs in to the system and fills in the personalized product requirements. Then the initial BOM and processing route are generated according to the information in the databases, the optimized scheme is obtained by GA, the personalized order is generated and returned to the customer. During the production process, the customer can query the production progress and maintain communication with the enterprise by the system. After production, the personalized order is stored in the database as enterprise resource.

3 Architecture of the Interactive Customization System Implementation As shown in Fig. 2, the architecture of interactive customization system is divided into four layers: client layer, WEB service layer, business logic layer and data layer.

Client layer WEB service layer Business logic layer Data layer

Demand definition

Demand browse

Demand feedback

Manufacturing program evaluation

Order tracking

WEB server Product structure definition Manufacturing resource database

Manufacturing task definition Process database

Manufacturing solution Consultation optimization strategy Production database

Fig. 2. System architecture of user-customized interactive system

The client layer is mainly the working interface for the customers customizing products. The business logic layer consists of a series of modules required to realize personalized interactive customization. These modules collect and analyze customers’ personalized demands, match manufacturing resources, realize optimization calculation, generate optimized production schemes, and feed back the final results to customers.

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The software used to develop the system is as follows: • Java runtime environment: J2SDK, Tomcat. • Development language: Java, HTML, JavaScript, JSP. • Database: MySQL.

4 Product Structure Packaging bag product structure includes product BOM and the product attribute structure. The BOM is shown in Fig. 3. Product attribute structure includes style, function, bagged material form, bagged performance, bag shape, packaging method, sterilization method, circulation method, etc. [6]. Product structure is the main information that customers and company rely on for product design. According to the product structure, the optional product parts are configured to realize product diversification and individual requirements. Outer layer Packaging bag

PET,Nylon,Paper,

Middle layer

Al,PET,

Inner layer

CPP,PE,

Ink layer

Ink,Water-based ink,

Adhesive layer

Bonding agent,Resin binder,

Fig. 3. Packing bag product bill of materials

In multi variety and small batch production, different packaging products have difference in function, shape, size, material and other attributes. Different product attributes correspond to different processing technology and raw material selection. For example, vacuum packaging requires packaging materials to have better gas barrier effect and more three-sided seal bag shape. Packaging with acid and alkali contents requires better corrosion resistance of packaging materials and adhesives. Some professional structure selection needs to be realized by the enterprise designers. The product attributes can be selected by customers according to their demands and then confirmed by the designers. By establishing the corresponding database and product information database, it is convenient for customers and designers to choose when designing products interactively.

5 Genetic Algorithm (GA) GA encodes the calculated individual by simulating the natural selection and genetic laws in the biological world. After multiple selection, crossover and mutation calculation iterations, the optimal individual meeting the requirements of the objective function is found from many possible solutions. The product attribute code of packaging bag is shown in Table 1. The coding method should ensure that the mutation or crossover calculation corresponds to an attribute value. So the product code is a complete binary value string.

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Properties

Attribute values

Codes

Styles

Flatbag, self-adhesive bag,……

000,001,……

Functions

General bag, food bag, ……

00,01,……

Bagged material forms

Solid, powdery,liquid

00,01,10

Bagging properties

Photosensitive, grease,……

000,001,……

Bag-shaped

Straight bags, sealing bag, ……

00,01,……

Packaging methods

Vacuum, inflation, barrier

00,01,10

Sterilization methods

Heating, microwave, radiation, ……

00,01,10,……

Circulation method

Room temperature, freezer, ……

00,01,……

Printing surface

Surface, inside, both sides

00,01,10

Printing colors

Single-color, two-color,……

000,001,……

The next step is to determine the objective function in GA. After the product attribute structure is clarified, the available materials are analyzed, the product BOM is determined, and the materials price is accounted for. The total materials price in BOM are taken as the objective function, and the BOM with the minimum price is wanted.

6 An Example A food bag with middle seal needs product quantity is one million, product size is 50 mm * 80 mm, and 20 bags are arranged on each printing plate. So the need material are 16 km. If material extra lost rate is 8% during processing, real needed material are 16 * (1 + 8%) = 17.28 km. Then the main materials by GA calculation are as follows (Table 2). Table 2. Quantity and price of main materials Layer

Materials

Specification (mm * µm)

Density (g/cm3 )

Weight (kg)

Unit price (Yuan/kg)

Price (Yuan)

Out layer (Print layer)

PET

510 * 12

1.4

148.06

21

3109.26

Middle layer

AL

515 * 9

2.71

217.06

30

6511.80

Inner layer

CPP

520 * 50

0.92

413.34

15

6200.10

7 Conclusions Combined with the production characteristics and customer demands, the interactive design system of plastic packaging printing is developed, a database of product attribute

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structure and product resources is established, and a series of standard structures, optional structures, materials and production processes are provided to allow customers to participate in the product design. The BOM of plastic packaging printing product is defined, the coding method of product attributes is set, the price of materials in BOM is taken as the objective function, and an optimized enterprise production scheme is given by using GA according to the needs of customers. The interactive customization system fully reflects the customer’s personalized demand, helps enterprises realize on-demand production, and make the customization needs seamlessly connected with enterprises. Acknowledgement. This research is supported by the National Key Research and Development Program of China (No. 2019YFB1707202).

References 1. Luo, X., Hao, Y.: Exploration of food packaging design based on interaction concept. Packag. Eng. 40(16), 67–70 (2019) 2. Wang, Y., Zhou, F.: Research on multi-sensory interactive packaging design forms. J. Packag. 12(3), 88–92 (2020) 3. Hu, D., Wu, P.: Personalized service-oriented product design based on genetic algorithm. Comput. Integrat. Manuf. Syst. 25(8), 2036–2044 (2019) 4. Dong, X.: Research on user personalized customization platform based on genetic algorithm. School of Mechanical Engineering, Tianjin University (2011) 5. Wang, H., et al.: Variant configuration design method supporting personalized product customization. J. Mech. Eng. 42(1), 90–97 (2006) 6. Wu, Q., Lin, W.: Practical Flexible Packaging Production Technology Manual, pp. 19–23. Cultural Development Press (2015)

Research on Simulation Method of Typical Parts Production Line of Printing Machinery Lirong Shao1 , Yuansheng Qi2(B) , Yanqiang Ma1 , Su Gao1 , Ximu Make1 , and Shunsheng Guo3 1 School of Mechanical and Electrical Engineering, Beijing Institute of Graphic

Communication, Beijing, China 2 School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication,

Beijing, China [email protected] 3 School of Mechanical and Electrical Engineering, Wuhan University of Technology, Wuhan, China Abstract. At present, when processing typical parts of printing machinery, it is difficult to debug the production line on site and slow market response. Taking the typical parts processing production line of printing machinery as the research object, the process simulation method of welding and processing production line of typical mechanical parts is proposed. By setting tasks for the corresponding components in the Works Library, the simulation modeling of the processing process production line of printing mechanical parts is completed, which provides a reference for enterprises to improve the degree of automation and realize intelligent manufacturing. Keywords: Printing machinery · Visual components · Production line · Simulation method

1 Introduction With the rapid change of market environment and the need of production mode, it is necessary to transform the production line into a flexible machining simulation production line [1]. Especially in printing enterprises, the parts involved are special, such as parts that need welding processing, In the production process, a large amount of digital information can not be integrated with physical real-time information. Therefore, using a virtual way to simulate the processing production line of typical parts of printing machinery can more intuitively reflect the working process of production, and it is also convenient to evaluate the production efficiency and whether the installation position of each equipment is reasonable.

2 Research on Simulation Method of Production Line 2.1 Processing Characteristics of Typical Parts of Printing Machinery In the production process of parts, the requirements and matching of machines are relatively high. Printing machinery parts involving welding process in printing enterprises, © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 352–357, 2022. https://doi.org/10.1007/978-981-19-1673-1_51

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Printer frame is the basic component of printing machinery and equipment, which is formed by multi-channel welding process. The frame should meet the characteristics of easy disassembly, so it also needs to be able to produce in real time and flexibly, as shown in Fig. 1. For this kind of printing machinery with large consumption, the welding process of typical parts is combined welding and post welding treatment of structural parts. It is necessary to match appropriate machines and production lines, and it is difficult to match in reality. Therefore, building an appropriate simulation production line can help realize the requirements of virtual production and solve the problems of matching difficulties and flexibility requirements.

Fig. 1. Printer frame

2.2 Preliminary Design of Simulation Production Line Aiming at a series of problems such as low intelligent level and weak market competition in the processing production line of typical parts of printing machinery, an intelligent production line is designed based on the processing technology of parts. Based on the process of feeding, welding, post welding treatment and warehousing of a weldment, five modules are designed, the connection relationship between modules is shown in Fig. 2 below. Industrial robot module

Processing module

Storage module

Works Process

Logiscs transfer module

Transport module

Fig. 2. Module diagram of simulation production line

3 Specific Design and Function of Simulation Production Line According to the composition design of the above production line simulation system, the geometric model of each module of the production line is constructed, and the simulation

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production line layout of parts is built by using visual component software, as shown in Fig. 3 below, It can realize the welding of the bottom surface and bottom plate of parts, processing and storage of parts.

Fig. 3. Digital twin simulation model

3.1 Process Simulation of Production Line The overall layout is shown in the Fig. 4 above. The production line is built with works library, that is, the works process component is used to control this production process. Nine works processes are set in the whole process, as shown in Fig. 4 below. More than two tasks are set in each works process, and the whole production line can operate normally through task interaction.

Fig. 4. Works process setting area

3.2 Three Dimensional Storage Module The three-dimensional storage module can improve the access efficiency of goods and realize the automatic access of goods. Compared with intelligent warehousing, the traditional warehouse lags behind in that it can not realize the intelligent control of goods location, so the application of intelligent warehousing came into being [2]. The problem of unique correspondence between goods code and warehouse location code is solved. 3.3 Logistics Transfer Module AGV is selected as the logistics transfer module of the simulation production line. In the process of parts transportation, it liberates manpower and meets the requirements of machining simulation production line.

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3.4 Industrial Robot Module In this simulation system, the lower end of the robot is connected with a robot controller, so as to realize the connection with works process tasks. Three robots are installed in the production line. The end actuator of the first robot is equipped with a welding gun for welding the bottom plate and part bottom, the second robot can grasp the welded parts and put them into the CNC machine. The third robot realizes palletizing function. 3.5 Processing Module The processing module of the production line processes parts, which is completed by the NC machine tool. The machine tool is equipped with works process. By adding tasks to the works process, the machine tool and robot can operate coordinately according to the process flow. 3.6 Transport Module The conveying module is mainly composed of conveyor belt, pulley, drum and sensor, the conveyor belt realizes the connection and sorting of feeding mechanism, processing unit and production line.

4 Simulation Process of Part Production Line 4.1 Simulation Operation The operation of the production line is driven by task. The simulation path diagram of the production line is shown in Fig. 5 below. The bottom plate is loaded and transported to the welding robot, as shown in Fig. 5(a). After the parts are placed on the bottom plate, the robot can weld, as shown in Fig. 5(b). After welding, the robot grabs the assembly and puts it into the NC machine tool for processing, as shown in Fig. 5(c). The robot takes out the processed (components turn white) components and puts them on the conveyor belt, as shown in Fig. 5(d). The robot grabs the components onto the palletized pallet. As shown in Fig. 5(e), after that, the AGV trolley will transport the stacked parts to the three-dimensional storage, as shown in Fig. 5(f).

Fig. 5. Schematic diagram of simulation production path

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4.2 Efficiency Analysis of Simulation Production Line Another advantage of visual component software is that it has statistical function, which can analyze the work efficiency of a component of the built production line. as shown in Fig. 6 below. It can be seen from the curve that the utilization rate of the machine tool in the initial stage is zero because the machine tool is in the post welding treatment stage of the production line. After the welding of the parts and the base plate is completed, the robot puts the workpiece into the machine tool, and the machine tool starts to work, and the utilization rate rises to about 37%. Then, with the stabilization of the discharging and feeding process, the utilization rate of the machine tool fluctuates up and down at 57.86%. Therefore, it can be seen that the utilization rate of the machine tool is also an important index for us to evaluate the advantages and disadvantages of this production line.

Fig. 6. Utilization curve analysis of CNC machine tool

4.3 Challenges of Simulation Production Line The simulation design process of the part production line in this paper is more comprehensive and meets the actual operation requirements. The construction and layout of the production line should be more optimized to save space. In addition, on the road of exploring intelligent manufacturing, there are still great technical bottlenecks for real-time mapping of simulation models [3].

5 Conclusions In order to solve the problems of difficult on-site debugging and slow market response of mechanical parts processing production line, this paper studies the simulation method of production line, designs the simulation system of production line based on the five modules mentioned above, and designs the virtual simulation layout and the whole process flow of production line through visual component software, The efficiency curve analysis is also carried out on some structure of the production line. With the rapid change of market demand, enterprises need to respond in time according to demand.

References 1. Zhao, D., Deng, S., Qi, Y., Zheng, C., Han, H.: Research on optimization method of flexible cellular production line based on digital twin. Robot. Technol. Appl. 6, 42–45 (2020)

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2. Lu, Y.: Construction method and application of digital twin factory for intelligent manufacturing. Dalian University of Technology (2020) 3. Xiong, J., Chen, Y., Chen, L.: simulation design of simulation production line based on multi robot. Mach. Tools Hydraul. 48(15), 66–71 (2020)

Study of Smart Storage Location Optimization Algorithm with Recommendation Technology Ruyu Zhai(B) , Aibin Huang, Mengmeng Zhang, and Caifeng Liu School of Media and Design, Hangzhou Dianzi University, Zhejiang, China [email protected]

Abstract. The development of intelligent manufacturing has promoted the progress of the Chinese storage industry. It has become a hot topic in modern economic development research to improve the efficiency of storage management. An optimal storage location recommendation algorithm was proposed for the existing slow order processing procedure and low efficiency in storage management. The collaborative filtering recommendation algorithm and K - means algorithm was applied to analyze this manuscript’s inbound and outbound orders history. Then determine the similarity of the goods by calculating the cosine similarity value. After that, an appropriate storage location can be selected according to the optimal principle to realize the recommendation of the storage location. In this way, the storage location can be optimized constantly. The application of recommendation technology in warehouse management can improve the efficiency of warehouse operation and allocation management, shorten the time of order processing, and promote the development of the warehouse industry. Keywords: Intelligent storage · Collaborative filtering · K-means · Location optimization

1 Introduction Intelligent warehousing technology has been used widely in warehouse management with the development of smart manufacturing in China. The intelligent storage system has the advantages of automation, information, intelligence and high efficiency compared with the traditional storage system. But most of the existing warehouse management systems only use simple information recording, statistical management and other functions and do not apply the location optimization method and software. About 80% of distribution centres or warehouses do not fully use location optimization in warehousing management [1]. It caused the low efficiency in warehouse management without considering the dynamic demand of goods. The traditional storage location optimization mainly places popular goods at a location that is easy to access based on their own experience. This method does save time on some scenarios, but it is highly time-consuming and laborious [2]. Then a technique based on mathematical statistics analysis was proposed to solve this problem. Heskett [3] optimized the goods location according to the turnover rate. The goods that have a © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 358–363, 2022. https://doi.org/10.1007/978-981-19-1673-1_52

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higher turnover rate will be located closer to the entrance and exit. Similarly, Yan [4] organized the goods location basing on different products’ size, quantity, structure and other attributes. However, this method needs to collect a huge amount of global data, and the entire process needs to be redone over time. Hence the optimization automated warehouse system has been introduced. The system optimizes the goods position basing on their dynamic status in the database, and then the system will continuously communicate with the optimization algorithm until the new location is found, which increases the warehouse efficiency [5, 6]. The rapid development of artificial intelligence has promoted the development of intelligent warehousing, and a goods location optimization method based on intelligent warehousing has emerged. Tao [7] presents a mathematical model of cargo space allocation, which considers both cargo turnover rate and correlations. This approach uses a self-learning particle swarm optimization algorithm to optimize goods location. Yan [8] uses the initial solution of the Genetic Algorithm to change the initial pheromone distribution of the Ant Colony Algorithm and other parameters to iterate and finally obtained a cargo location plan with shelf stability and storage efficiency as the goal. Although these methods are highly efficient, they are difficult to implement in many applications, due to they require a lot of historical data. In order to solve the problem of the existing storage location optimization, a new optimal storage location recommendation algorithm based on big data analysis, collaborative filtering algorithm, and K-means clustering algorithm is proposed in this research. The warehouse inbound and outbound historical order records are cleaned up and preprocessed by cluster analysis before passing through the algorithm. The collaborative filtering algorithm is used to analyze the correlation of goods. It can improve the reliability of location recommendations. The appropriate position was selected according to the optimal principle after obtaining the collection of the goods with high similarity to realize the recommendation of the location of goods. The algorithm is evaluated with real warehouse data. After the storage location optimization, the average processing time of each order is reduced by 49% comparing to the original goods locations.

2 Algorithm Design Optimal storage location recommendation is based on the idea of putting the items with a high correlation index together. First, the historical order information needs to be collected and preprocessed, and then K-means clustering is performed basing on the extracted product features to obtain the optimal position of the goods. Next, the collaborative filtering algorithm establishes the frequency matrix between the goods to find the interests similar to the current goods. In addition, the product with the highest similarity is obtained, the location of the adjacent product is found, and the site is recommended to the current product to realize the optimal location recommendation. The general flow of the algorithm is shown in Fig. 1. The specific process of the algorithm is as follows: the order information and goods information were obtained firstly, then the invalid data and dirty data in the original data were eliminated, the different goods in the same order were given the same number, and the data preprocessing was completed. After that, the order model, goods model and goods frequency matrix are established. The order model includes order number, goods

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Fig. 1. Flow chart of optimal storage location recommendation algorithm

name, goods number, goods specification, goods type, goods quantity, processor and time. The goods model consists of the information of the goods number, goods name, goods specification, goods type and location. The goods frequency matrix (Table 1) is calculated by the number of times the goods appears in the order. After the model is established, the order number, goods number and goods type in the order model were input as the sample set to the K-means algorithm for clustering operation. The Euclidean distance between the samples is calculated, and the sample set is divided into different clusters. Finally, five clustering results are obtained. Then according to the clustering results, the goods in the same group are placed in adjacent positions. Thus the first optimization part is completed. Table 1. The goods frequency matrix. N ij denotes the frequency of goods i and j belonging to the same order The goods 1

…

The goods j

…

The goods n

The goods 1

0

…

N 1j

…

N 1n

…

…

…

…

…

…

The goods i

N i1

…

Nij

…

Nin

…

…

…

…

…

…

The goods n

N n1

…

Nnj

…

0

Next, the location was further optimized based on the first optimization. The history records of the goods were contained in the historical order record constitute a historical recordset. Then each record and goods in the set, item by item, were processed. If goods i and j appear simultaneously for each order record, find the corresponding goods in the goods frequency matrix and increase its frequency value by 1 to modify the goods frequency matrix. After all the goods are processed, the final goods frequency matrix is obtained. Next, the cosine similarity is calculated according to the goods frequency matrix after processing:   |N (i) ∩ N (j)| (1) sim(i, j) = cos →, → =  i j |N (i)| ∗ |N (j)| − → − → where sim(i,j) denotes similarity between item i and j, i and j represent the scoring vectors of items i and j. The higher the value of sim(i,j) is, the higher the similarity between item i and item j is. The result is a similar set of goods. The similar goods in the

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set are sorted from large to small according to the similarity value to get the goods with the highest similarity. The location information of the goods is obtained, and the nearest neighbour of the location is selected as a result of the recommendation to optimize the position further. In summary, the whole storage location optimization recommendation algorithm is over.

3 Experimental Results and Evaluation To evaluate our work, we design a set of evaluation experiments by using the data from a real hydropower station’s tool warehouse management system. 3.1 Dataset 113565 real historical outbound records from October to November 2015 in the tool warehouse management system were extracted to verify the effectiveness of the algorithm. There are 47623 valid data after the data preprocessing operation. For each delivery order, the order content is a sequence containing several tools. 3.2 Indicators for Algorithm Evaluation The main indexes used to evaluate the performance of warehouse management are warehousing time and order processing time. This experiment aims to optimize the storage location to improve the efficiency of a storage operation and shorten the order processing time. Therefore, the algorithm’s performance can be evaluated from two aspects: distance and time costs. 3.3 Algorithm Results Three cases are used to test the algorithm proposed in this paper, and the results are shown in Table 2. The first column denotes the cargo to be recommended. The second column represents the similar goods set of the goods to be recommended. The third column means the goods with the highest similarity. The fourth column indicates the new location of the goods finally recommended by the algorithm. Table 2. Recommended results of optimal position Item ID

Similar collection

Max_similarity

Recommend position

6900804

{6905367, 6900845, 6900789, 6904245, 6902937}

6905367

2003-5-8

6902518

{6901218, 6905484, 6905101, 6905367, 6900845}

6901218

2001-9-3

6904251

{6901184, 6901409, 6903072, 6901477, 6901321}

6901184

2001-3-6

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3.4 Efficiency Comparison The distance cost and time cost of order processing can be obtained for a randomly acquired order by recording the total distance and time spent. Figure 2 shows the space and time cost of order processing in the initial location, optimization based on collaborative filtering algorithm, optimization based on clustering algorithm and optimization based on our algorithm of three different orders.

Fig. 2. Results of distance cost (a) and time cost (b)

The Fig. 2 shows that the operation efficiency is improved after location optimization with our algorithm. For example, it takes 18 m and 160 s to process the order 1444871760 with the initial position. In comparison, the distance is reduced to 8 m, and the time is reduced to 70 s after optimizing by our algorithm, which reduces the cost by about 56%. ((Initialcost − Optimizedcost)/Initialcost × 100%) In general, the average order processing cost is reduced by 49% compared with the cost in their initial states. The cost is reduced by 21% compared with the single algorithm optimization. The algorithm achieves good results after comprehensively considering the properties and characteristics of goods and their correlation. In some cases, using only the collaborative filtering algorithm is even less efficient than not using any algorithm at all, as we can see the order 1444871760 in Fig. 2. This result is caused by the relatively simple similarity calculation model leading to inaccurate recommendation results, and the error is within an acceptable range. In summary, the evaluation experiment results show that the algorithm proposed in this paper could effectively improve warehouse operation efficiency.

4 Conclusions An optimal storage location recommendation algorithm was proposed to solve location optimization in warehouse management and improve the efficiency of intelligent warehouse management. The K-means algorithm and collaborative filtering algorithm are used to analyze the historical orders. The high-similar items obtained by the algorithm were placed in the nearby location to optimize the storage location. This algorithm

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reduced the average cost of processing orders by 49%, improving the processing efficiency. In addition, the experimental results of this paper have a certain guiding role in the management of drug storage in hospital pharmacies, the management of book borrowing and returning in the library, and the optimization of commodity location in the supermarket. Acknowledgements. This work was supported by Zhejiang Provincial Science and Technology Program in China (2021C03137).

References 1. Dong, X.: Research on Optimization Model and Algorithm of Storage Location. Harbin Institute of Technology (2006) 2. He, F.: Design and Implementation of Intelligent Warehouse Management System. Xidian University (2019) 3. Heskett, J.L.: Cube-per-order index a key to warehouse stock location. Transp. Distrib. Manag. 3(1), 27–31 (1963) 4. Yan, B., Yan, C., Long, F., Tan, X.-C.: Multi-objective optimization of electronic product goods location assignment in stereoscopic warehouse based on adaptive genetic algorithm. J. Intell. Manuf. 29(6), 73–85 (2018) 5. Wu, T.: Research on Multi-objective Location Optimization of Storage System Based on Genetic Algorithm. Wuhan University of Technology (2011) 6. Mbalib Slotting Optimization. https://wiki.mbalib.com/wiki/Slotting_Optimization. Accessed 2 June 2021 7. Tao, Q.: Optimization and Simulation of Dynamic Location-Allocation in an Automated Warehouse. Kunming University of Technology (2016) 8. Yan, T.: Research on Warehouse Space Allocation Model and Algorithm Based on Fishbone Layout. Beijing Jiaotong University (2018)

An Express Transportation Monitoring System Based on S-CNN Lei Huang1 , Yuan Zhang1 , Lei Zhu2(B) , Yanping Du1 , and Ao Ding3 1 School of Mechanical and Electrical Engineering, Beijing Institution of Graphic

Communication, Beijing, China 2 Postal Technology R&D Center, Beijing, China

[email protected] 3 School of Transportation, Beijing Jiaotong University, Beijing, China

Abstract. Rough Handling of Express Parcels (RHEP) means that express parcels are not handled as required, which is one of the increasingly prominent problems in the express industry. It not only brings bad effects to the industry but also causes serious social problems such as resource waste and environmental pollution. Based on S-CNN, for three typical types of RHEP (dropping, throwing, and kicking), an express transportation monitoring system is proposed in this paper. The system is mainly composed of terminals, servers, and client. The system can collect acceleration data of parcels, process data, extract features and recognize RHEP of express transportation. Simulation experiment of RHEP in the laboratory, the recognition accuracy of S-CNN is up to 95.3%. Compared with SVM, BP, and S-CNN, more than 99% of samples of express transportation have a predicted probability of RHEP more than 0.95, which verifies the effectiveness of the intelligent recognition method in express transportation. Keywords: S-CNN · RHEP · Intelligent recognition · Features of acceleration

1 Introduction With the rapid development of e-commerce, the express industry plays an important role in the national economy. According to the latest data released by the State Post Bureau, the express quantity in China reached 83.36 billion. With the rapid development of the industry, it also faces many challenges, among which RHEP is one of the most concerning problems in the industry. At present, the judgment of RHEP in China is based on “The distance between express sorting and the contact surface where the express is placed should not exceed 30 cm, and the express parts should not exceed 10 cm” [1]. How to quickly and accurately recognize the type of RHEP is one of the main ways to solve the problem according to the existing definition and judgment basis of RHEP. The research related to express monitoring is generally divided into the following three aspects: hardware development [2], data acquisition [3, 4], and intelligent recognition methods [5]. Based on existing research, the monitoring system is proposed to © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 364–368, 2022. https://doi.org/10.1007/978-981-19-1673-1_53

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complete real-time monitoring RHEP in express transportation. The combination of recognition results and time, place, and other information can reduce the occurrence of RHEP.

2 Structure of Monitoring System The system is mainly composed of terminals, servers, and client. The terminal collects and intercepts potential abnormal data, sending it to the server to complete recognition of RHEP and timely feedback to the client. As shown in Fig. 1, the terminal is mainly composed of a data acquisition module, microprocessor module, a data storage module, communication module, and power module. Choosing enterprise-class computing C6 series server, which can complete recognition of RHEP, here is not to do a detailed description. The client realizes the terminal management, trip management, data download, and so on, as shown in Fig. 2.

Fig. 1. Terminal of the system

Fig. 2. Client of the system

3 RHEP Identification Method CNN is used to recognize the RHEP, a simplified CNN model(S-CNN) by simplifying Alex Net network structure in this paper, and the S-CNN network structure is shown in Fig. 3. RHEP recognition includes data acquisition, data interception, feature extraction, and pattern recognition. The terminal mainly collects acceleration data, the sampling frequency is set to 6400 Hz, and the threshold is set to 5 g (g = 9.8 m/s2 ) to reduce the amount of data. The customized wooden frame fixed terminal (as shown in Fig. 4) to avoid the negative impact of relative movement. In addition to the necessary data preprocessing, intercepting data that exceeds the threshold, obtaining a 3 × 32000 matrix where the absolute value data of the 50th sampling point on any axis is more than or equal to 5 g. Extracting features can compress data volume and improve model recognition performance [6]. The recognition results of simulation experiments of RHEP have verified that mean, variance, kurtosis, skewness, dynamic range, short-term energy, and zero-crossing rate are good characteristics [6]. After windowing, obtaining a 3 × 50 × 7 matrix.

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Fig. 3. Structure of S-CNN

Fig. 4. Terminal fixation method

As shown in Fig. 3, the input layer is connected to two convolutional layers which use 60 and 132 convolution kernels with a size of 3 × 3, Relu as the activation function. The pooling filter size is 3 × 3, the step size is equal to 3, Tanh as the activation function. Two fully connected layers containing 120 and 48 neurons. LRN layer Dropout layer to avoid over-fitting and the probability of the Dropout layer is set to 0.5. The final output layer is also a fully connected layer in essence, which contains 4 neurons and uses the Softmax function.

4 Experiments and Results 4.1 Simulation Experiment Simulating RHEP in a laboratory that simulates a logistics transfer center environment. A total of 2535 simulation experiments were conducted, including 557 times normal, 663 times dropping, 698 times throwing, and 617 times kicking. The prediction results of S-CNN are as follows. The average correct rate of the training set, verification set, and test set was 99.82%, 94.54%, and 95.36% respectively. In contrast, the recognition accuracy of the test set BP network fluctuates between 85% and 95%, which is very unstable. 4.2 Delivery Experiment Seven domestic companies were selected and the delivery experiments included 6 times in the same city, 6 times in short distance, and 2 times in medium distance. At present, there are still some defects in the delivery experiment, such as the general performance of terminals and insufficient transmitting times. At the same time, SCNN, SVM, and BP networks recognize the existing data. The statistical content of the recognition results are as follows: Statistics of the prediction results of RHEP are shown in Table 1, statistics of the maximum recognition probability interval are shown in Table 2, and statistics of the maximum absolute value interval of acceleration are shown in Table 3. It is found in Table 1 that the proportion of RHEP in the three methods recognition results is 93.79%, 94.35%, and 93.79% respectively, indicating that the method of intercepting data is effective. Throwing often occurs in the transportation of express parcels, in Table 1, throwing accounts for more than 85%, kicking and dropping are both less than 3%, but still there. It can be seen from Table 2 that the prediction probability of RHEP is higher than 0.95, accounting for more than 94%. Comparing the prediction

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results of the three methods, it can be found that S-CNN can also be used to recognize RHEP in express transportation. Express parcels will be sorted several times in the transportation, in order to achieve sorting effect or improve efficiency, the height and distance of throwing will be different in different environments. Table 3 can directly reflect the impact of different degrees of throwing on express parcels. More than 70% of the maximum acceleration of throwing is distributed at 5–15 g, concentrated at a specific height. The maximum acceleration of throwing more than 10% exceeds 30 g, which will cause damage to the contents and the packages. The maximum acceleration of kicking exceeds 25 g, will produce a destructive impact on express packages. The maximum acceleration of dropping distribution at 10–20 g, which may occur in the process of loading, unloading,and handling, and the fall height is relatively fixed. Table 1. Statistics of prediction results of RHEP Method

Percentage of throwing

Percentage of fast kicking

Percentage of dropping

SVM

89.27%

1.69%

2.82%

BP

88.70%

2.82%

2.82%

S-CNN

88.70%

2.26%

2.82%

Table 2. Statistics of maximum recognition probability interval Recognition probability SVM

BP

S-CNN

>=0.95

94.35% 95.48% 95.48%

>=0.85

99.44% 100%

99.44%

>=0.75

100%

100%

100%

Table 3. Statistics of acceleration absolute maximum interval Interval (g)

Percentage of throwing

Percentage of fast kicking

Percentage of dropping

[5,10)

56.55%

0.00%

40.00%

[10,15)

17.86%

0.00%

60.00%

[15,20)

8.93%

0.00%

0.00%

[20,25)

4.17%

50.00%

0.00%

[25,30)

1.19%

25.00%

0.00%

>=30

11.31%

25.00%

0.00%

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5 Conclusion Through a large number of surveys and practical operations in the express industry, it is found that although the degree of automation is getting higher and higher, RHEP is always one of the biggest obstacles to the development of the industry. After a large number of investigations, summarized three typical types of RHEP. Based on the data of the simulation experiment, the S-CNN model is proposed, which shows good recognition accuracy and efficiency. In the delivery experiment, comparing the recognition results of the three methods, verified that S-CNN can also be used in the complex delivery environment. Acknowledgements. This work is supported by the Key Project of Basic Research of Beijing Institute of Graphic Communication(Ea202001); Research and Innovation Team Project of Beijing Institution of Graphic Communication(Ed202001); General Project of Basic Research of Beijing Institution of Graphic Communication(Eb202001).

References 1. GB/T27917-2011: National Standard of Express Service. Standards Press of China, Beijing (2012) 2. Zhang, Y., Huang, L., Ding, A., et al.: An express service process monitoring system based on multi-sensor fusion. In: 2021 IEEE 4th International Conference on Electronics Technology (ICET), pp. 89–94 (2021). https://doi.org/10.1109/icet51757.2021.9451066 3. Ruiz-Garcia, L., Barreiro, P., Robla, J.I.: Performance of ZigBee-based wireless sensor nodes for real-time monitoring of fruit logistics. J. Food Eng. 87, 405–415 (2008) 4. Li, C., Nien, C., Liao, J., Tseng, Y.: Development of wireless sensor module and network for temperature monitoring in cold chain logistics. In: 2012 IEEE International Conference on Wireless Information Technology and Systems (ICWITS), pp. 1–4 (2012) 5. Ding, A., Zhang, Y., Zhu, L., Yanping, D., Ma, L.: Recognition method research on rough handling of express parcels a study on acceleration features and CNN. IEEE Trans. Geosci. Remote Sens. 20(2), 143–152 (2017) 6. Xiao, J., Luo, X.P., Feng, Z.F., Zhang, J.X.: Using artificial intelligence to improve identification of nanofluid gas-liquid two-phase flow pattern in mini-channel, AIP Adv. 8 (2018)

Research on Suitability and Material Characteristics of Inkjet Printing Based on Xuan Paper Jinglin Ma1(B) , Qi Zeng2 , and Rui Kong1 1 Art Design Department, Shandong Communication and Media College, Jinan, China

[email protected] 2 Information Engineering Department, Shandong Communication and Media College,

Jinan, China

Abstract. The purpose of this paper is to study the suitability and material properties of ink jet printing of Chinese Xuan paper through experiments. As an important material to show Chinese calligraphy and painting art, xuanpaper has a gap with the traditional methods of Chinese calligraphy and painting art when it is reproduced in the form of digital micro spray, including color reduction and color density. This paper, through experimental research, uses alum solution and silica solution to coating and print traditional raw xuan paper twice and print test, analyzes the dot characteristics and color density of three materials printed samples, compares with the works created by traditional ink, and determines the reasonable way to copy traditional calligraphy and painting works. The influence of coating technology on the material properties of raw xuan paper and coated paper was determined by testing the whiteness, folding resistance and tensile strength of the raw xuan paper and coated paper. The results of this paper are that the two coated xuan paper has the greatest advantage in color reduction, and basically retains the visual characteristics of conventional xuan paper, and the folding resistance and tensile strength have increased. It is of great significance to the inkjet printing technology based on xuan paper. Keywords: Color density · Whiteness · Tensile strength

1 Introduction As one of the four treasures of Chinese traditional study, paper is also one of the four great inventions of ancient China. Xuan paper originated in Xuanzhou more than 1000 years ago, accompanied by Chinese classical painting and calligraphy, Chinese painting and calligraphy works created with xuan paper have made an important contribution to the continuation and spread of Chinese culture. Xuan paper is made of wingceltis and straw. The xuan paper has long fiber and high toughness, The surface of xuan paper has the texture formed by production tools during production and processing. These are the important characteristics of Chinese xuan paper which are different from other paper. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 369–375, 2022. https://doi.org/10.1007/978-981-19-1673-1_54

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The paper without any surface treatment is called raw xuan paper, Raw xuan paper has large gap between plant fibers and rough surface. When it is used, it is very easy to form ink halo and diffusion phenomenon. Of course, this is the artistic feature of Chinese calligraphy and painting. Freehand painting and calligraphy often use this kind of xuan paper. Sometimes, in order to create fine lines of patterns, artists use plant glue and alum to characterize the surface of raw xuan paper to prevent ink from bleeding and diffusion, so that the ink can be fixed on the surface of the paper instead of penetrating into the inside of the paper, so as to achieve the purpose of fine painting, and the color of painting is more full and gorgeous than that of raw xuan paper [1]. This kind of xuan paper treated with plant glue and alum is called pimade xuan paper. Raw xuan paper and pimade xuan paper are important materials for creating Chinese calligraphy and painting, However, when ink-jet printers are used for printing on these two materials, the ink will infiltrate into the inside of the paper in varying degrees, resulting in the decrease of saturation, and the details of the picture will become blurred, forming a gap compared with the original. In order to improve the printing quality, porous mineral materials are used to form a layer of coating on the surface of xuan paper, so that the tiny ink droplets from the printer can be fixed on the coating surface, and will not penetrate into the inside of the paper, so as to improve the printing quality. This kind of xuan paper is specially used for ink-jet printersr [2]. Due to the existence of coating, there is a big gap between this kind of xuan paper and traditional xuan paper in appearance and handle, which widens the similarity gap between the copy and the original. In the current research on inkjet printing raw paper, researchers and producers tend to use high-density mineral pigments coated on the paper surface in order to better realize the high reduction performance of color, mainly composed of silica, calcined kaolin, light calcium, titanium dioxide, silicate and so on [3]. This makes the coating on the surface of rice paper cover up the natural texture of the surface of rice paper while obtaining a high degree of color restoration, and lose the unique artistic characteristics of Chinese calligraphy and painting. In this paper, based on the raw xuan paper, the alum mixed solution was coated to getthe first time coated xuan paper, and then the silica mixed solution was coated to get the second time coated xuan paper. The ink spot shape of the printer on raw xuan paper and two kinds of coated xuan paper was observed, and the color density were tested, and the color reduction performance of the three materials was analyzed. The bending strength and tensile strength of the three materials were tested and their physical properties were analyzed, so as to determine the printability of the three materials, and achieve a balance between color restoration and preserving the physical properties of rice paper surface.

2 Coating Experiment of Raw Xuan Paper 2.1 Experimental Materials “Red Star” 70g/m2 raw xuan paper; Deionized water; Gelatin; Alum; Silicon dioxide; Polyvinyl alcohol; Waterborne polyurethane; “Yongchun” 3dzbj mounting machine.

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2.2 Preparation of Coating Solution According to the Chinese ancient book Mustard garden painting manual of the Qing Dynasty, “when alum is used to treat rice paper, 7% gelatin and 3% alum should be used in summer, 10% gelatin and 3% alum should be used in winter.” in this experiment, 1# coating solution composition ratio uses the summer formula ratio recorded in Mustard garden painting manual. Determine the formula proportion of 2# coating solution by integrating relevant literature in the industry [2] (Table 1). Table 1. 1# Coating solution composition Deionized water

Gelatin

Alum

90%

7%

3%

Gelatin and alum were dissolved in deionized water at 90°C and then mixed and cooled at room temperature (Table 2). Table 2. 2# Coating solution composition Deionized water

Silicon dioxide

Polyvinyl alcohol

Waterborne polyurethane

80%

10%

8%

2%

At room temperature, the deionized water and waterborne polyurethane were fully stirred and fused, silica was added to form a stable suspension solution, and then heated to 50 °C, polyvinyl alcohol was added to form a stable mixed solution, which was stored at constant temperature. 2.3 Coating Process Use a palm brush at the surface of 50 cm × 50 cm format raw xuan paper was evenly coated with 1# coating solution. When it was cooled to 50% water content at room temperature, it was put into the mounting machine. The heating temperature was set at 80°C and the pressure was increased for 30 s. Then 10 pieces of 1# coated xuan paper were prepared. After the 1# coated xuan paper is completely dried, evenly coat 2# coating solution on its surface, cool it to 50% water content at room temperature, put it into mounting machine, set the heating temperature at 80°C, and take it out after 30 s to prepare 5 pieces of 2# coated xuan paper.

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3 Color Restoration Experiment 3.1 Experimental Materials and Equipment Raw xuan paper; 1# coated xuan paper; 2# coated xuan paper; Epson9908 printer; K3 pigment ink; ZCF electron microscope; Optical microscope; Kemei FD-5BT spectrodensitometer. 3.2 Printing Dot Observation Use Epson 9908 printer and K3 pigment ink, set to 720 dpi × 720 dpi printing density, respectively print K50 color blocks on raw xuan paper, 1# coated xuan paper and 2# coated xuan paper. Observe the printing dot shape at different magnification, as shown in Fig. 1 and Fig. 2.

Fig. 1. 1,000 times magnification dot

Fig. 2. 10,000 times magnification dot

On raw xuan paper, the ink diffused seriously, the dot outline was fuzzy, and there was no obvious boundary; On 1# coated xuan paper, the ink diffusion is light, and the dot has a rough outline; On 2# coated xuan paper, the dot is basically formed and has a clear outline. 3.3 Color Density Detection Use Epson 9908 printer and K3 pigment ink, set the printing density to 720 dpi × 1440 dpi, Print k100 color blocks on raw xuan paper, 1# coated xuan paper and 2# coated

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xuan paper respectively, and measure the color density of each color block. The results are shown in Table 3. Table 3. Color density test results Material type

Raw xuan paper

1# coated xuan paper

2# coated xuan paper

K100 Color density

1.12

1.33

1.57

Because the ink diffuses into the paper, the color density of raw xuan paper is low; After using 1# coating solution, part of the ink can be retained on the surface of xuan paper, and the color density is significantly improved; After two times of coating, in using 2# coating solution, the color reduction ability is greatly improved, most of the ink pigment particles remain on the surface of xuan paper, and the color density is greatly improved.

4 Physical Property Experiment 4.1 Whiteness Test Whiteness testing materials and equipment: raw xuan paper sample; 1# coated xuan paper sample; 2# coated xuan paper sample; WSB-1 whiteness meter. The whiteness test results are shown in Table 4. Table 4. Whiteness test results Material type

Raw xuan paper

1# coated xuan paper

2# coated xuan paper

Whiteness/%

67

69

75

The results showed that the whiteness of raw xuan paper was slightly improved by 1# coating solution, and the whiteness was greatly improved by 2# coating solution. 4.2 Folding Endurance Test Folding endurance testing materials and equipment: raw xuan paper sample (15 mm × 200 mm); 1# coated xuan paper sample(15 mm × 200 mm); 2# coated xuan paper sample(15 mm × 200 mm); MIT Paper folding endurance tester. Set the tension of the folding tester to 4.9N, The folding endurance test results are shown in Table 5. The results showed that 1# coating solution significantly improved the folding resistance of raw xuan paper, and 2# coating solution slightly improved the folding resistance compared with 1# coated rice paper due to repeated coating.

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Raw xuan paper

1# coated xuan paper

2# coated xuan paper

Folding endurance (transverse)

18

34

36

Folding endurance (portrait)

37

51

55

4.3 Tensile Strength Test Tensile strength testing materials and equipment: raw xuan paper sample(15 mm × 150 mm); 1# coated xuan paper sample(15 mm × 150 mm); 2# coated xuan paper sample(15 mm × 150 mm); WDZ-100 Paper tensile strength meter. The tensile strength test results are shown in Table 6. Table 6. Tensile strength test results Test type(N/mm)

Raw xuan paper

1# coated xuan paper

2# coated xuan paper

Tensile strength (transverse)

0.62

0.81

0.93

Tensile strength (portrait)

0.94

1.57

1.61

The results showed that the tensile strength of 1# coating solution was significantly improved, and that of 2# coating solution was slightly improved compared with 1# coating paper due to repeated coating. 4.4 Summary of Physical Characteristics The whiteness, folding strength and tensile strength of three kinds of xuan paper samples were tested, and their physical properties were shown in Fig. 3. After one and two times of coating, the surface whiteness of xuan paper increased slightly under the influence of alum and silica. Because the coating solution contains glue, increase the degree of adhesion between the paper fibers, paper folding strength and tensile strength have been improved, one time coating compared with raw xuan paper

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Fig. 3. Comparison of physical properties of three xuan paper samples

changes more, two times coating compared with one time coating increase is relatively small. Alum and silicon dioxide are mineral materials. After being processed into small particles, they are fixed on the paper surface by adhesive. Because the whiteness of alum and silica particles is greater than that of xuan paper, the surface whiteness of paper will also increase after coating. If the alum and silica content of the coating solution is too high, the whiteness of the surface of rice paper will be much greater than the original whiteness of xuan paper, forming a large color difference. The surface of alum and silica particles is porous structure, which can store printing pigments and fix the printing pigments on the paper surface, which is an important reason for improving the color reduction performance of coated xuan paper.

5 Conclusion After the raw xuan paper was treated with 1# coating solution using gelatin and alum as raw materials, the pimade xuan paper (1# xuan paper) was very similar to the raw xuan paper in physical properties such as whiteness and surface texture, the color restoration degree increased to a certain extent, and the physical properties of the paper were significantly improved. Compared with raw xuan paper, the whiteness of 2# xuan paper re coated with 1# xuan paper increased observably, resulting in a slight appearance difference. The degree of color restoration has been greatly increased to meet the requirements of art reproduction. Using 1# coating solution and 2# coating solution to coat raw xuan paper twice can improve its ink-jet printability, greatly improve the material properties, and is suitable for the reproduction of calligraphy and painting works of art.

References 1. Huanhuan, W.: Effect of gelled alum water on properties of traditional Chinese handmade paper. In: Proceedings of the 17th Annual Conference of China papermaking society, pp. 538–539 (2016) 2. Zhenjuan, W.: Effect of fixing agent on color reducibility of ink jet rice paper. Imaging Technol. 28(4), 57–58 (2016) 3. Hongjun, W.: Preparation and application of coating for color ink jet printing paper. China Pulp Paper Ind. 42(16), 18–21 (2021)

Preparation and Regulation Mechanism of Rape Straw Nano Cellulose Based on Ozone Pretreatment Yong Lv1,2(B) , Linna Shao1 , Ci Song1 , and Jie Gao1,3 1 School of Engineering and Information, Yiwu Industrial and Commercial College, Yiwu,

Zhejiang, China [email protected] 2 Key Laboratory of Eco-Textile, Ministry of Education, Jiangnan University, Wuxi, China 3 Yiwu Wuxin Packing and Printing Co., Ltd., Yiwu, China

Abstract. Nano cellulose has the dual characteristics of nano materials and biomass materials. It presents broad application prospects in biodegradable packaging materials and agricultural film materials. The natural anti degradation barrier in rape straw and the supra molecular structure of cellulose with ordered crystalline structure could lead to the low enzymolysis efficiency and long treatment time. Based on the preparation of biological enzyme and mechanical method, ozone pretreatment process was used to degrade lignin in lignocellulosic fibers. It could improve the accessibility of cellulose. For the rape straw with the size of −300 mesh, the delignification rate reaches its maximum when the water content reached 60%. When the moisture content of the material continued to increase to 75%.The ozone consumption and delignification rate decreased significantly. Ozone pretreatment can effectively degrade lignin and a small amount of hemicellulose inrape straw. Meanwhile, it has little effect on cellulose. Ozone pretreatment can promote the application of nano cellulose in degradable packaging materials and agricultural film materials. Keywords: Nano cellulose · Ozone · Rape straw · Preparation · Lignin

1 Introduction Due to the unique physicochemical properties of nano materials and the biomass properties, nano cellulose has abundant, renewable, biodegradable and other excellent green environmental protection characteristics in nature [1]. Cellulose Nanofibers (CNF) has attracted great attention in the material field among academics, such as aerospace, national defense, biomedicine, new energy, barrier materials, green packaging, agricultural film and so on [2]. Rape straw is an important biomass. It is mainly abandoned or burned in the field [3]. It has not been effectively utilized. Compared with rice straw, rape straw has higher cellulose content. Meantime, the outer surface of straw is compact and smooth. It contains

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 376–380, 2022. https://doi.org/10.1007/978-981-19-1673-1_55

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weak medium layer such as fat and wax, which can improve the water resistance properties. However, due to the tight entanglement in the supra molecular structure of raw materials, natural anti degradation barrier is presented. Moreover, the supra molecular structure of straw has ordered crystalline structure, which makes it difficult for enzymes to easily reach the glycosidic bonds between cellulose and glucose monomers. It resulted in low enzymatic hydrolysis efficiency and long treatment time. Ozone pretreatment is an oxidation pretreatment method. It can effectively degrade lignin and a small amount of hemicellulose in rape straw. However, it has little effect on cellulose [4]. The advantage of ozone pretreatment is that the reaction can be carried out at room temperature and atmospheric pressure, which can effectively remove lignin from lignocellulosic fibers without producing toxic compounds for subsequent enzymatic fermentation [5]. Carboxyl and aldehyde groups were introduced into natural cellulose. However, the influence of ozone pretreatment system on rape straw has not been reported. The mechanism of ozone pretreatment needs to be further studied. This study focuses on the mechanism of ozone pretreatment method. It could provide theoretical basis and guidance for the controllable preparation and performance improvement of CNF products.

2 Experimental 2.1 Materials and Methods Rape straw was provided by Zhejiang Jinchang Special Paper Co., Ltd; Cellulase was purchased from Shandong Taian XINDELI Biotechnology Co., Ltd. General oxygen was from Wuxi Xinnan Chemical Gas Co., Ltd. Citric acid (analytical purity), sodium citrate (analytical purity) and other conventional reagents are purchased from Sinopharm Chemical Reagent Co., Ltd. 2.2 Preparation of CNF Based on Ozone Pretreatment In order to study the effect of water content on ozone pretreatment, deionized water was added to the material to make it reach the water content required by the experiment. The rape straw was kept at 4 °C for 12 h to make the water balanced. Adjust the pressure valve to make the pressure of the ozone generator reach 0.1 MPa. The main pipe flow is controlled to 1.0 L/min through the valve. The concentration of ozone in the inlet flow of the reactor was controlled to 60 mg/L. The ozone concentration at the outlet of the reactor was detected every 5 min. When ozone pretreatment was finished, the pipeline air flow and condensate water are closed. The reaction products are collected for testing. 2.3 Determination of Component Analysis of Rape Straw The watercontent of the sample is measured by the water meter to calculate the dry weight of the sample. 0.5 ± 0.01 g of sample was added into a 100 ml beaker. The deionized water was added into the mass of sample. To calculate the water-soluble content of the sample. Cellulose, xylan, acid insoluble lignin (AIL) and acid soluble lignin (ASL) in samples were determined according to the method of Sluiter et al. [6].

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3 Results and Discussions 3.1 Effect on Ozone Consumption of Rape Straw with Different Water Content In order to study the ozone treatment effect ofrape straw powder with different water content. In the experiment, rape straw powder samples with particle size of −300 mesh were selected. The water content of samples was adjusted to be 30%, 45%, 60% and 75%. The samples were put into the reaction vessel for ozone treatment. The parameters of ozone treatment in the experiment were as follows: ozone concentration is 60 mg/L, gas flow rate is 1 L/min. By analyzing the reaction kinetics curve, ozone consumption of each group of ozone treatment, the optimal water content in the ozone pretreatment was determined. The effects of material particle size and water content on the ozone treatment process were also studied. The relationship between ozone consumption and rape straw with different water content is shown in Fig. 1. From the curve, it is found that each stage corresponds to the different reaction stages of the raw materials in the reaction vessel. when the water content increases from 30% to 60%, the ozone consumption increases in the initial stationary period. When the water content reaches 75%, the ozone consumption decreases significantly.The mechanism of water in ozone treatment are complex. The water in the raw material also participates in the formation of hydroxyl radicals and acts as the reaction medium. The water content of materials have important effects on the ozone consumption and reaction kinetics.

Fig. 1. The relationship between ozone consumption and rape straw with different water content

3.2 Effect on Ozone Consumption of Rape Straw with Different Particle Size The decrease of the particle size can increase the surface contact area between the particle and ozone gas. It is found that the reduction of particle size can improve the reaction rate and degree. The water in the raw material can participate in the ozone reaction and promote the reaction. However, the water in the raw material will hinder the mass transfer of ozone.

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As shown in Fig. 2, For the same particle size materials, when the water content increases from 30% to 60%, the ozone consumption and delignification rate could reach its maximum. When the water content of the rape straw continued to increase to 75%, the ozone consumption and lignin removal rate decreased significantly. For different particle size materials, the water content of the maximum delignification rate is also different.

Fig. 2. Ozone consumption (OC) and delignification rate (DLR) of ozone treated rape straw with different particle size and water content

3.3 Linear Fitting between Lignin Degradation and Ozone Consumption In the reaction process, the ozone consumption (OC) is calculated by the ozone consumption per unit mass of rape.The delignification rate (DLR) is usually the ratio of the reduced lignin content of the sample after ozone treatment to that of the original sample. As is shown in Fig. 3, there was a significant linear correlation between ozone consumption and delignification rate.

Fig. 3. Linear fitting between delignification rate and ozone consumption

4 Conclusions In the process of ozone pretreatment, the particle size and water content of materials have an important influence on lignin dissolution. When the water content reaches 60%,

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the delignification ratereaches its maxium for the rape straw of the particle size with −300 mesh materials. For the samples with different particle size, the optimal water content of ozone treatment is different. There is interaction between particle size and water content.There was a significant linear correlation between ozone consumption and delignification rate. The ozone pretreatment could provide theoretical basis and guidance for the controllable preparation and performance improvement of CNF products. Acknowledgments. This research was financially supported by Jinhua Science and Technology Key Project (No.2020-2-005); the 2021 Visiting Engineer Program of Colleges of Universities in Zhejiang (NO. FG2021195)–Reduction structure design of special-shaped box and development of key barrier technology of packaging materials; University Students’ Science and Technology Innovation Program in Zhejiang (new talent plan) (No. 2021R475002); 2022 Public welfare Technology Application Research Program in Zhejiang province (Grant NO. LGG22C160003)– Construction and absorption capacity of the nanocellulosic hydrogel and the key technique in its graphitized electrode materials.

References 1. Thomas, B., Raj, M.C., Joy, J., Moores, A., Drisko, G.L., Sanchez, C.: Nanocellulose, a versatile green platform: from biosources to materials and their applications. Chem. Rev. 118(24), 11575–11625 (2018) 2. Zinge, C., Kandasubramanian, B.: Nanocellulose based biodegradable polymers. Europ. Poly. J. 133, 109758 (2020) 3. Xu, L., Jiang, Y., Wang, L.: Thermal decomposition of rape straw: pyrolysis modeling and kinetic study via particle swarm optimization. Energy Convers. Manage. 146, 124–133 (2017) 4. Maqsood, H.S., Bashir, U., Wiener, J., Puchalski, M., Sztajnowski, S., Militky, J.: Ozone treatment of jute fibers. Cellulose 24(3), 1543–1553 (2017). https://doi.org/10.1007/s10570016-1164-y 5. Liu, M., Chen, X., Tian, X.: Ozone oxidation of kraft bamboo pulp for preparation of nanofibrillated cellulose. Int. J. Poly. Sci. 2018, 1–7 (2018). https://doi.org/10.1155/2018/345 2586 6. Sluiter, A., et al.: Determination of structural carbohydrates and lignin in biomass. Labor. Anal. Proc. 1617(1), 1–16 (2008)

Cyan Cationic-Initiated Photocurable Material with High Curing Rate for UV-LED Curing Qi Lu, Xianfu Wei, Ting Zhu, Beiqing Huang(B) , and Hui Wang(B) School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing 102600, China [email protected], [email protected]

Abstract. With the development of photocuring technology, cationic-initiated photocurable material has been widely used due to low volume shrinkage and the absence of oxygen inhibition during polymerization. However, spectral absorption characteristics of most commercial cationic photoinitiators are incompatible with emission from UV-LED radiation, which causes the curing rate to decrease. In this study, a cyan photocurable material was prepared for UV-LED curing based on cationic photo-initiating. Photosensitizer was added to improve the absorption characteristic of cationic photoinitiator and a high curing rate was obtained. First, several appropriate types of photosensitizers were determined by characterizing UV-Vis absorption spectra. Then the influence of different types of monomers and photosensitizers on the curing rate were tested, and the basic composition of the cyan photocurable material was determined. Finally, the concentration effect of photoinitiator and photosensitizer on the curing rate was studied. The results indicated that the optimal curing performance was obtained in the cyan UV-LED curable material formulation with dye 727 as colorant, IK-1 as cationic photoinitiator, ITX as photosensitizer, GR43 as monomer and E44 as prepolymer. Keywords: Cationic-initiated photocuring · UV-LED curing · Curing rate

1 Introduction Photocuring technology is summarized as an industrial technology with “5E” characteristics: efficient, enabling, economical, energy saving and environment friendly. In recent years, as UV-LED light sources have been widely applicated due to the advantages of energy saving, high luminous efficiency and less heat generation, UV-LED curing materials have attracted much attentions, which has been widely promoted and applied in decoration [1], textile processing [2], printing [3], additive manufacturing [4, 5], coating and other fields. Attributed to different active centers for polymerization initiating, photocuring can be divided into two kinds of mechanisms: free radical photocuring and cationic photocuring. Compared with free radical photocuring, cationic photocuring has attracted more attention due to the advantages such as good adhesion, low volume shrinkage and the absence of oxygen inhibition during polymerization [6–8]. However, there are © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 381–387, 2022. https://doi.org/10.1007/978-981-19-1673-1_56

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still some challenges in the formulation of cationic photocuring materials for UV-LED curing. Being different from traditional UV radiation from mercury lamp, the emission of LED light source exhibits a single peak, and the energy is concentrated in a narrow ultraviolet or visible spectrum, for instance, 365 nm, 385 nm, 395 nm and 405 nm. At present, most commercial cationic photoinitiators exhibit absorption characteristics at a wavelength range of 220–300 nm, which do not match with the emission of UV-LED light source, thus reducing the photocuring rate of UV-LED curable materials. In order to solve this problem, various efforts have been made to red-shift the absorption range of cationic photoinitiator to match the wavelength of UV radiation [9–16]. In addition, the use of photosensitizer in combination with cationic photoinitiator is another effective strategy to accelerate the photopolymerization rate of epoxy photocurable systems [12]. Benzophenone [13], anthracene [14] and thioxanthone [15] are commonly used as photosensitizers. Among them, the spectral absorption of thioxanthone photosensitizer is highly compatible with the emission of UV-LED light source, which makes it an effective photosensitizer in cationic-initiated UV-LED photocuring materials [16]. In this research, a cyan cationic-initiated UV-LED photocuring material was prepared and a fairly high curing rate was obtained by adding photosensitizer to combine with cationic photoinitiator, and the influences of photoinitiator, photosensitizer and monomers on curing rate were demonstrated. The present work provides potential prospects for the development of photocurable color materials in UV-LED curing applications such as printing, coating and additive manufacturing.

2 Experimental 2.1 Material Epoxy resin E-44 was purchased from Shandong Tianmao New Material Technology Co., Ltd and used as prepolymer. Cyan dye 727 were purchased from Wenzhou Aotelai Chemical Co., Ltd. Cationic photoinitiator IK-1 was purchased from Nanjing Hengqiao Chemical Material Co., Ltd. Monomers involved in this research are listed below. 3-allyloxymethyl-3 -ethyloxetane (GR101), 3-ethyl-3-hydroxymethyl oxocyclobutane (GR41) and bis(1ethyl(3-oxetanil)methyl)ether (GR43) were purchased from Hubei Gurun Technology Co., Ltd. 1,2-epoxy-4-epoxyethylcyclohexane (TTA22), 3,4-epoxycyclohexylmethyl3, 4-epoxycyclohexanecarboxylate (TTA21) and bis (3,4-epoxycyclohexylmethyl) adipate (TTA26) were purchased from Jiangsu Tetra New Material Technology Co., Ltd. Hydroxybutyl vinyl ether (HBVE) was purchased from Shanghai Macklin Biochemical Co., Ltd. Tri(ethylene glycol) divinyl ether (DVE) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

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Photosensitizer involved in this research are listed below. 1-hydroxycyclohexyl phenyl ketone (184), 2-methyl-4’-(methylthio)-2-morpholino-propiopheno (907), phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide (819), isopropyl thioxanthone (ITX), 2,4-diethyl-9H-thioxanthen-9-one (DETX), macromolecular thioxanthone compound (1508) and 4,4’-bis(diethylamino)benzophenone (EMK) were purchased from Tianjin Jiuri New Materials Co., Ltd. 2.2 Preparation of Photocurable Material Cyan dye 727 was dissolved in monomer and stirred evenly to form a transparent solution. Then the solution was mixed with prepolymer in an appropriate mass ratio, and photoinitiator and photosensitizer were added and stirred evenly in dark. 2.3 Characterization UV-Vis Absorption Spectra of Photosensitizers. Photosensitizers were separately diluted in ethanol to prepare solutions with a concentration of 0.001% and ultravioletvisible (UV-Vis) absorption spectra were recorded using a UV-2700 spectrophotometer (Shimadzu, Japan) in 10 mm matched quartz cells at room temperature. Curing Rate of Photocurable Material. Curing rate of photocurable material was tested on Semray UV4003 belt conveyor UV-LED curing system (Heraeus, Germany). Photocurable material was coated on a PET film with a 4 µm wire rod and placed on the belt conveyor to pass through a UV-LED light source with a wavelength of 395 nm. The photocuring performance was determined by touching the surface of coating film, and the highest speed of the belt conveyor that realize complete solidification of the coating film was taken as the curing rate of the photocurable material.

3 Results and Discussion 3.1 UV-Vis Absorption Spectra of Photosensitizers In this work, cyan photocurable material is designed as a dye-doped epoxy-based cationic photopolymerization system using the iodonium salt IK-1 as photoinitiator, and photosensitizer is introduced to absorb UV-LED radiation then produces radical intermediate, which may react with iodonium reagent to generate active radical cations for initiating photopolymerization [17, 18]. Accordingly, several kinds of commercial photosensitive compounds were chosen as candidates to improve the initiation efficiency and the spectral absorption characteristics were characterized by UV-Vis spectra, as illustrated in Fig. 1. At the wavelength of 395 nm, which is the wavelength of UV-LED radiation, ITX, DETX, 1508 and EMK strongly absorb while the absorbance of 184, 819 and 907 is relatively weak. Therefore, ITX, DETX, 1508 and EMK were selected as photosensitizers and the performance in photocuring was further studied.

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Fig. 1. UV-Vis absorption spectra of photosensitizers

3.2 Effect of Types of Photosensitizers on Photocuring Rate Photocuring rate was tested using samples prepared with different species of photosensitizers. According to Fig. 2, thioxanthone compounds ITX, DETX and 1508 can significantly produce higher curing rate than EMK, which could be explained by the inhibition originated from amine groups in EMK on cationic polymerization. In order to avoid the problems of both yellowing brought by DETX and poor solubility of macromolecule 1508, ITX was selected as the optimal photosensitizer for the further experiments.

Fig. 2. Curing rate with different kinds of photosensitizers in UV-LED radiation with a power density of 2.8 W/cm2 at 395 nm

3.3 Effect of Proportion of Photoinitiator and Photosensitizer on Curing Rate Figure 3 illustrates the curing rate measurement results of samples with different ratios of photoinitiator IK-1 and photosensitizer ITX. The curing rate accelerates when the ratio of photoinitiator and photosensitizer is regulated from 1:1 to 2:1 or 3:1, which could be attributed to the quantitative growth of active center of cationic photopolymerization. As the ratio of photoinitiator to photosensitizer continues to increase, the sensitization efficiency for the photoinitiator tends to decrease and the curing rate slows down. In order to minimize the interference of yellowing caused by photosensitizer ITX on the cyan hue of photocurable material, the photoinitiator/photosensitizer ratio of 3:1 is considered to be the best proportion.

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Fig. 3. Curing rate with different proportion of photoinitiator and photosensitizer in UV-LED radiation with a power density of 2.8 W/cm2 at 395 nm

3.4 Effect of Concentration of Photoinitiator on Curing Rate Concentration of photoinitiator is one of the most important factors that affects the rate of photopolymerization reaction, samples containing different concentrations of photoinitiator were thus prepared for testing. According to Fig. 4, when the concentration of photoinitiator increases from 1% to 3%, more active centers are generated and the curing rate increases accordingly. As the concentration of photoinitiator further increases, the promotion of photocuring slows down. Nevertheless, in UV-LED radiation with a power density of 2.8 W/cm2 , a curing rate of up to 57 m/min can still be achieved, and the photoinitiator concentration of 4% is a recommendable condition.

Fig. 4. Curing rate with different concentrations of photoinitiator in UV-LED radiation with a power density of 2.8 W/cm2 at 395 nm

3.5 Effect of Species of Monomers on Photocuring Rate As one of the main components in photocuring materials, monomer plays a role in dissolving solid substance (photoinitiator, photosensitizer, colorant, etc.), diluting oligomers and adjusting viscosity of the formulation, which has an important effect on photocuring. Accordingly, curing rate was tested using samples prepared with different kinds of polymerizable compounds as monomer. As shown in Fig. 5, compared

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with GR41 with only one oxacyclobutane ring, GR43 with two oxacyclobutane ring produces an extraordinary photocuring performance, and a curing rate of 76 m/min is obtained, which is the maximum speed of belt conveyer attached to the UV-LED light source. In addition, curing rate of samples prepared with epoxy or vinyl ether compound as monomer is not ideal. Therefore, GR43 is chosen to serve as monomer in the formulation of UV-LED curable material.

Fig. 5. Curing rate with different kinds of monomers in UV-LED radiation with a power density of 14 W/cm2 at 395 nm

4 Conclusions In this study, we have demonstrated a facile approach for the preparation of fast curing UV-LED curable material with cyan color. The key feature is the use of thioxanthone compounds to coordinate with a commercially available cationic photoinitiator IK-1 in photopolymerization via photosensitization process. The optimal photocuring performance, which reaches 76 m/min, is obtained from a formulation using IK-1 as cationic photoinitiator, ITX as photosensitizer and GR43 as monomer in 395 nm UV-LED irradiation. Therefore, the present work solves the problem of low curing rate in cationicinitiated UV-LED photopolymerization, and provides an efficient strategy in designing color materials for the purpose of promising applications in UV-LED curing. Acknowledgements. This study is funded by BIGC Project (No. Eb202002) and High-Level Talent Training Program of Beijing Municipal Education Commission (No. 22150121003/063). We gratefully acknowledge the support from Institute of Advanced Ink, Beijing Institute of Graphic Communication.

References 1. Sang, R., Manley, A.J., Wu, Z., et al.: Digital 3D wood texture: UV-curable inkjet printing on board surface. Coatings 10(12), 1144 (2020) 2. Seipel, S., Yu, J., Periyasamy, A.P., et al.: Inkjet printing and UV-LED curing of photochromic dyes for functional and smart textile applications. RSC Adv. 8(50), 28395–28404 (2018)

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3. Urbas, R., Rotar, B., Hajdu, P., et al.: Evaluation of the modified braille dots printed with the UV ink-jet technique. J. Graph. Eng. Des. 7(2), 15–24 (2016) 4. Wang, X., Jiang, M., Zhou, Z., et al.: 3D printing of polymer matrix composites: a review and prospective. Compos. B Eng. 110, 442–458 (2017) 5. Park, H.K., Shin, M., Kim, B., et al.: A visible light-curable yet visible wavelength-transparent resin for stereolithography 3D printing. NPG Asia Mater. 10(4), 82–89 (2018) 6. Lee, S.H., Kim, H.G., Kim, S.S.: Organic-inorganic hard coating layer formation on plastic substrate by UV curing process. Macromol. Res. 18(1), 40–46 (2010) 7. Sun, X., Jin, M., Wu, X., et al.: Bis-substituted thiophene-containing oxime sulfonates photoacid generators for cationic polymerization under UV–visible LED irradiation. J. Polym. Sci., Part A: Polym. Chem. 56(7), 776–782 (2018) 8. Schissel, S.M., Jessop, J.L.P.: Controlling shadow cure in cationic photopolymerizations using physical cues and processing variables. J. Appl. Polym. Sci. 137(5), 48290 (2020) 9. Hou, W., Sun, J., et al.: Tunable functionalization of graphene oxide sheets through surfaceinitiated cationic polymerization. Macromolecules 48(4), 994–1001 (2015) 10. Crivello, J.V., Lam, J.H.W.: Photoinitiated cationic polymerization with triarylsulfonium salts. J. Poly. Sci. Poly. Chem. Edit. 17(4), 977–999 (1979) 11. Crivello, J.V., Lam, J.H.W.: Photoinitiated cationic polymerization by dialkylphenacylsulfonium salts. J. Poly. Sci. Poly. Chem. Edit. 17(9), 2877–2892 (1979) 12. Shi, S., Croutxe-Barghorn, C., Allonas, X.: Photoinitiating systems for cationic photopolymerization: ongoing push toward long wavelengths and low light intensities. Prog. Polym. Sci. 65, 1–41 (2017) 13. Kahveci, M.U., Tasdelen, M.A., Yagci, Y.: Photochemically initiated free radical promoted living cationic polymerization of isobutyl vinyl ether. Polymer 48(8), 2199–2202 (2007) 14. Cho, J.D., Kim, E.O., Kim, H.K., et al.: An investigation of the surface properties and curing behavior of photocurable cationic films photosensitized by anthracene. Polym. Testing 21(7), 781–791 (2002) 15. Cho, J.D., Hong, J.W.: Photo-curing kinetics for the UV-initiated cationic polymerization of a cycloaliphatic diepoxide system photosensitized by thioxanthone. Eur. Polymer J. 41(2), 367–374 (2005) 16. Karaca, N., Ocal, N., Arsu, N., et al.: Thioxanthone-benzothiophenes as photoinitiator for free radical polymerization. J. Photochem. Photobiol. A 331, 22–28 (2016) 17. Bagheri, A., Jin, J.: Photopolymerization in 3D printing. ACS Appl. Poly. Mater. 1(4), 593– 611 (2019) 18. Ligon, S.C., Liska, R., Stampfl, J., et al.: Polymers for 3D printing and customized additive manufacturing. Chem. Rev. 117(15), 10212–10290 (2017)

Preparation of Highly Hydrophilic Aluminum Pigment by Double-Layer Coating Liuxin Zhang, Beiqing Huang(B) , Xianfu Wei, and Hui Wang School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. Aluminum powder pigments are favored by coatings and ink industries due to their excellent properties, but there are problems of poor dispersibility and compatibility in the application of waterborne systems. In order to improve these performance defects, SiO2 is coated on the external of the metal aluminum powder by the gel sol method. Then coated polymer layer by free radical solution polymerization to achieve double-layer coating of aluminum powder and improve its hydrophilicity. The chemical composition and external structure of the modified aluminum powder were characterized by FT-IR, SEM and EDS. Microscope and contact angle tests can verify that the hydrophilicity of the modified aluminum powder pigment has been greatly improved. Modified aluminum pigments can be used in water-based inks and the gloss of the ink film can be well maintained. This research lays a foundation for the future production of aluminum pigments for waterborne inks and paintings. Keywords: Aluminum pigments · Surface modification · Inorganic-organic hybrid encapsulation · Glossiness · Hydrophilicity

1 Introduction As an important metallic pigment, aluminum powder has excellent covering properties and metallic flashing effect, and is widely used in paintings and inks [1]. With the improvement of volatile organic compounds (VOCs) emission standards, environmentally friendly products such as water-based inks and water-based coatings have become mainstream products in the future market. In the production process of aluminum powder pigments, fatty acids are generally added as lubricants. Fatty acids can protect aluminum powder to a certain extent, but the surface of aluminum powder is hydrophobic, which leads to poor dispersion of commercial aluminum powder in water-based inks. In practical applications, the phenomenon of pigment particles agglomerates easily. In order to ameliorate the hydrophilicity of aluminum powder pigments and ameliorate the compatibility of aluminum powder with water-based systems, the research on the external modification of aluminum powder pigments to make aluminum powder suitable for water-based systems has made great progress.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 388–395, 2022. https://doi.org/10.1007/978-981-19-1673-1_57

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Common inorganic layer coating methods mostly use SiO2 or TiO2 , and aluminum powder coating modification is carried out by the sol/gel method [2, 3]. However, the presence of the inorganic coating layer reduces the gloss of the aluminum powder external, and further treatment is needed to not affect the application of aluminum powder in water-based systems [4]. The presence of the organic polymer layer can improve the external properties of the aluminum powder pigment, such as improving the dispersibility and hydrophilicity of the aluminum powder in the system. But the organic layer is easy to peel off [5]. At present, inorganic-organic hybrid coating modification to overcome the defects of inorganic layer coating or organic layer has become a research hotspot [6–9]. The presence of the hybrid coating layer can greatly improve the hydrophilicity of the aluminum powder pigment and improve the dispersibility of the aluminum powder pigment in the aqueous system. The film has good mechanical strength and is not easy to fall off. In this paper, ethyl orthosilicate (TEOS) and vinyl triethoxy silane (KH-151) are used as precursors. Under alkaline conditions, they synergistically hydrolyze to form a Silica coating on the surface of aluminum powder, and then use free radical solution polymerization. Coating the polymer layer to prepare inorganic-organic hybrid coating type water-based aluminum pigment.

2 Experimental 2.1 Materials Aluminum powder PHY20 was purchased from Jinjiang Yakun Pigment Co., Ltd. Tetraethyl orthosilicate (TEOS), Silane coupling agent KH-151 (97%), ammonia (25– 28%), hydroxyethyl methacrylate (96%, containing 250 ppm MEHQ stabilizer) (POLYMER), divinylbenzene (containing stabilizer) (DVB) Purchased from Shanghai Macklin Biochemical Co., Ltd. Azobisisobutyronitrile (AIBN) was purchased from Shisihewei Chemical Co., Ltd. Anhydrous ethanol was purchased from Beijing Chemical Plant.

3 Preparation Methods Preparation of SiO2 Layer Coated Aluminum Powder. Commercially available aluminum powder is dispersed in a certain amount of absolute ethanol, washed by ultrasonic, filtered and dried for later use. Take 2 g of the cleaned aluminum powder and place it in a 250 mL three-necked flask, with 50 mL of absolute ethanol as the solvent, place it in a water bath and stir thoroughly for 1 h, and then raise the temperature to 40 °C. At the same time, TEOS, KH-151 diluted with ethanol and ammonia and water diluted with ethanol are added dropwise, and the constant pressure dropping funnel controlled the dropping rate to 1 drop/s. After the addition is complete, react at a stable temperature of 40 °C for 6 h, then suction filter, wash and vacuum dry. Preparation of Polymer Layer Coated Aluminum Powder. 2 g SiO2 coated aluminum flakes was placed in a 250 ml three-necked flask, with 120 mL of absolute ethanol as the solvent, and place it in a water bath and fully stir for 1 h. The reaction

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system was heated to 80 °C, and after constant temperature, ethanol-diluted POLYMER, DVB and ethanol-diluted AIBN are added dropwise, and the constant-pressure dropping funnel controlled the dropping rate to 1 drop/s. After the addition is complete, react at a constant temperature for 6 h, filter, wash and vacuum dry to obtain hybrid coated aluminum powder.

3.1 Characterization and Measuring Method The Nicolet iS50 FTIR spectrometer from Thermo Scientific was used to collect infrared spectra, and the integrated ATR accessory was used. The test wavelength range was 650– 4000 cm−1 , and the number of scans was 32. The SU8020 scanning electron microscope (SEM) of Hitachi, was used to observe the surface mophology of aluminum pigment samples. The elemental analyzer (EDS) of Japan JEOL company was used to characterize the type and content of the micro-zone elements of the material. A NETZSCH STA 449 F5 Jupiter thermogravimetric analyzer was used for the thermogravimetry test, and heat to 500 °C under N2 atmosphere, heating rate 10 per min. The dispersibility performance of aluminum pigments in deionized water was observed through Hande wireless portable digital microscope ReView-Wifi. The KRUSS DSA30R interface rheometer was used to measure the contact angle of aluminum powder with deionized water. 3.2 Coating Film Gloss Test The silver ink used for proofing was carried out with a KPP type gravure proofing machine of British RK Company, and the sample ink film was tested with a TC-108DPA type gloss meter.

4 Results and discussion 4.1 Reaction Mechanism and Structural Characterization Figure 1 shows the synthesis route and mechanism of the SiO2 layer and the polymer layer in the modification of hybrid coated aluminum powder. The coating involves twostep reaction. At first, TEOS and KH-151 are synergistically hydrolyzed under alkaline conditions to form a silica layer on the surface of the aluminum powder. The second step is to use AIBN as the initiator, DVB as the cross-linking agent, and POLYMER as the monomer to coat polymer layer on the aluminum powder. The hybrid coating layer improves the hydrophilicity of the aluminum powder pigment.

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Fig. 1. Aluminum powder hybrid layer coating diagram

Figure 2 shows the infrared spectra before and after coating. Because there is a large amount of -OH on the surface of the aluminum powder pigment, a strong vibration peak near 3400 cm−1 , compared with uncoated aluminum powder, SiO2 coated aluminum the powder has a Si-O-Si vibration peak at 1065 cm−1 , a Si-OH characteristic peak at 875 cm−1 , and a C = C characteristic peak at 1631 cm−1 , Prove that TEOS and KH-151 are polymerized on the surface of aluminum powder pigment. On the inorganic-organic modification aluminum powder, the C = C characteristic peak at 1631 cm−1 disappeared, and a clear C = O characteristic vibration peak appeared near 1732 cm−1 , which confirmed that the methyl group was disappear by free radical solution polymerization. The organic polymer is successfully polymerized on the surface of SiO2 modified aluminum pigment.

Fig. 2. FT-IR spectrum of aluminum powder pigment

The SEM image of the aluminum flakes are shown in Fig. 3. The external of the original aluminum flakes pigment is relatively smooth with only a few small particles, which may be small-sized fragments of aluminum powder. Comparing SiO2 coated aluminum powder with uncoated aluminum powder, it can be clearly seen that there are numerous of particles on the external of SiO2 modification aluminum powder, which are the hydrolysis products of TEOS and KH-151. It can be seen from Fig. 3c that there is a large amount of polymer on the external of the aluminum flakes coated with the organic layer, which indicates that polymer has formed a coating layer of organic polymer on the external of the aluminum flask pigment.

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Fig. 3. SEM and EDS image of aluminum powder (a) Uncoated aluminum flakes (b) Silica coated modified aluminum flakes (c) Hybrid coated modified aluminum flakes

The relative element percentage on the external of aluminum powder is tested and analyzed by EDS. It can be seen from Fig. 3a and 3b that compared to the uncoated aluminum powder, the EDS diagram of the SiO2 coated aluminum powder clearly shows the characteristic peaks of C, O, Al and Si. The appearance of the Si peak indicates that there is a SiO2 coating layer on the external of the aluminum flakes pigment. And in Fig. 3c, it can be found that the polymer layer coated aluminum flakes and the SiO2 coated aluminum flakes have the same elemental signal, but the peak intensity of C and O increases, and the peak intensity of Si element decreases. It is worth noting that the content percentage of Al element is relatively reduced. This change indicates that the polymer layer and the SiO2 layer have been modified on the aluminum powder. TGA results are shown in Fig. 4. The aluminum powder degrades before 400 °C. The weight loss is owing to the evaporation of moisture on the external of the aluminum flakes and the thermal decomposition of the coating layer. When the temperature continues to rise, the weight of the aluminum powder gradually rises. The reason is that N2 easily penetrates the coating layer on the external of the flake aluminum and reacts with the aluminum powder to form AlN. This leads to an increase in the weight of the flake aluminum pigment. Since the heat resistance of the SiO2 layer is better than that of the organic coating, the slope of the thermal decomposition curve of the inorganic layer is

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smaller than that of the organic layer. In addition, the weight loss difference before and after the organic layer coating can also verify the existence of the organic coating layer.

a

b

Fig. 4. TG curve of aluminum powder pigment

4.2 Dispersion Characterization The dispersion of aluminum powder in water was observed by microscope. The magnification is 40 times, and get microscopic image is shown in Fig. 6. It can be seen from Fig. 6a that the aluminum powder agglomerates seriously in water indicating that the dispersion of original aluminum powder in water is extremely poor due to its hydrophobicity. But the modified aluminum pigment dispersed into smaller particles in water. This is due to the hydrophilic polymer existing in the organic coating (Fig. 5).

Fig. 5. Microscopic image (×40) of (a) original aluminum powder and (b) hybrid layer coated aluminum powder

The contact angle test result of aluminum powder is shown in Fig. 6. Figure 6a is the original aluminum powder, which exhibits hydrophobicity due to the presence of the fatty acid layer. Figure 6b shows the SiO2 layer coated with aluminum powder, and its surface contact angle is 41°, showing hydrophilicity. Figure 6c shows the hybrid coated aluminum powder. The test result is 22°, indicating that the hybrid coated aluminum powder exhibits excellent hydrophilicity. These results are also the same as the results of the dispersion of aluminum powder in water under a microscope.

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Fig. 6. Contact angle of (a) Aluminum powder (b) SiO2 layer coated aluminum powder (c) Hybrid layer coated aluminum powder

4.3 Application Performance Aluminum pigment is tested through gloss meter at 60°, the test results show that the gloss of the original aluminum powder ink film is 42.30, and the gloss of the ink film decreases by 7% after the inorganic layer is coated. The gloss of the hybrid coated modified aluminum powder ink is 42.86, indicating that the gloss of the modified aluminum powder ink can be better maintained (Table 1). Table 1. Aluminum powder gloss Sample

Raw aluminum powder

Inorganic coated aluminum powder

Hybrid coated aluminum powder

Gloss

42.30

38.27

42.86

5 Conclusions Using tetraethyl orthosilicate (TEOS) and vinyl triethoxy silane (KH-151) as precursors, synergistic hydrolysis under alkaline conditions produces a SiO2 coating film on the external of the aluminum flakes pigment. Then, a free radical solution polymerization method is used to prepare inorganic-organic double-layer coated water-based aluminum flakes pigments. The obtained water-based aluminum powder pigment has excellent hydrophilicity and can be well dispersed in an aqueous system. The ink film formulated with modified aluminum powder pigment can maintain good gloss. Acknowledgements. We gratefully acknowledge the funded from BIGC Project (No. Eb202002) and Advanced Ink Laboratory, Beijing Institute of Graphic Communication.

References 1. Karbasi, A., Moradian, S., Tahmassebi, N., et al.: Achievement of optimal aluminum flake orientation by the use of special cubic experimental design. Prog. Org. Coat. 57(3), 175–182 (2006)

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2. Zhou, L., Huang, S.L., Kong, J.R., et al.: Characterization of flaky aluminum pigments multicoated by TiO2 and SiO2 . Powder Technol. 237, 514–519 (2013) 3. Wang, H., Huang, S.L., Zuo, Y.J., et al.: Corrosion resistance of lamellar aluminium pigments coated by SiO2 by sol–gel method. Corros. Sci. 53(1), 161–167 (2011) 4. Amirshaqaqi, N., Salami-Kalajahi, M., Mahdavian, M.: Investigation of corrosion behavior of aluminum flakes coated by polymeric nanolayer: effect of polymer type. Corros. Sci. 87(oct.), 392–396 (2014) 5. Balaji, J., Sethuraman, M.G.: Chitosan-doped-hybrid/TiO2 nanocomposite based sol-gel coating for the corrosion resistance of aluminum metal in 3.5% NaCl medium. Int. J. Biol. Macromol. 104, 1730–1739 (2017). https://doi.org/10.1016/j.ijbiomac.2017.03.115 6. He, Y., Li, H., Liguo, O., Ding, F., Zhan, Z., Zhong, Y.: Preparation and characterisation of water-based aluminium pigments modified with SiO2 and polymer brushes. Corros. Sci. 111, 802–810 (2016). https://doi.org/10.1016/j.corsci.2016.06.014 7. Pi, P.H., Liu, C., Wen, X.F., et al.: Aluminum pigments encapsulated with hybrid silica film with carboxyl groups and their stability and dispersibility in aqueous media. Canad. J. Chem. Eng. 93(6), 1102–1106 (2015) 8. Liang, J., Azhar, U., Men, P., et al.: Fluoropolymer/SiO2 encapsulated aluminum pigments for enhanced corrosion protection. Appl. Surf. Sci. 487(SEP.1), 1000–1007 (2019) 9. Cz, A., Ran, H.A., Xw, B., et al.: In-situ encapsulation of flaky aluminum pigment with poly(methylhydrosiloxane) anti-corrosion film for high-performance waterborne coatings. J. Ind. Eng. Chem. 89, 239–249 (2020)

Preparation and Properties of High Coating Rate Phase Change Microcapsules Qingqing Zhang, Zhicheng Sun(B) , Xiaoyang Du, Gongming Li, and Zhitong Yang Beijing Engineering Research Center of Printed Electronics, School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. Phase change materials can store and release energy according to the temperature changes of the surrounding environment, thereby improving energy utilization efficiency. Phase change microcapsules refer to tiny “containers” with a core-shell structure formed by high molecular polymers encapsulating phase change materials, which can effectively prevent leakage and volatilization of phase change materials while protecting the core material. In this study, a water/oil emulsification system was constructed, and phase change microcapsules with paraffin as the core material and silicon dioxide as the wall material were prepared by in-situ polymerization. Differential scanning calorimeter (DSC), scanning electron microscope (SEM) and Fourier infrared spectroscopy (FTIR) were used to characterize the structure and performance of phase change microcapsules. In addition, the influences of different drop accelerations of tetraethyl orthosilicate on the surface morphology and phase change performance of microcapsules were investigated. Moreover, the preparation process of inorganic wall materials-phase change microcapsules was optimized, providing a new method for the application of energy storage technology. Keywords: Phase change microcapsule · Morphology · encapsulation · Dropping acceleration

1 Introduction Phase change materials (PCMs) are high-efficiency heat storage materials, which are accompanied by a large amount of energy storage and release during their phase transition, and can be used in the fields of energy storage and temperature regulation [1]. However, the traditional phase change materials have defects such as easy leakage, easy corrosion, phase separation and volume change in practical application. Microencapsulation technology can embed the phase change material and prevent it from interacting with the surrounding environment [2]. In contrast, the use of microencapsulation technology has obvious advantages. Phase change microcapsules refer to tiny “containers” with a core-shell structure that encapsulate phase change materials [3]. The most common preparation methods include interfacial polymerization, in-situ polymerization, and suspension polymerization [4]. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 396–400, 2022. https://doi.org/10.1007/978-981-19-1673-1_58

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The wall materials of phase change microcapsules can be divided into organic shell materials and inorganic shell materials. However, organic shell materials have defects such as low mechanical strength, poor flame retardancy, and low thermal conductivity [5]. Therefore, in order to make up for the shortcomings of organic shell materials, many scholars use inorganic materials as wall materials. At present, phase change microcapsules prepared by inorganic wall materials generally have problems such as low embedding rate and poor heat storage performance. Therefore, it is necessary to optimize the preparation method of microcapsules in order to obtain phase change microcapsules with higher coating performance. In this study, an in-situ polymerization method was used to prepare phase change microcapsules with paraffin as the core material and silica as the wall material. Tetraethyl orthosilicate (TEOS) was added dropwise at different speeds to investigate the morphology, structure and composition of the microcapsules. Thermophysical parameters such as phase transition temperature and latent heat were analyzed, and the embedding rate of microcapsules was calculated. At the same time, the phase change microcapsule ink is prepared in a certain ratio with the color paste, printing stock, and binder to obtain a phase change microcapsule ink, which is coated on a paper cup to test the heat preservation performance of the phase change microcapsule.

2 Experiment 2.1 Materials and Instruments Main materials: Paraffin wax (melting point 50–52 °C, Sinopharm Chemical Reagent Co., Ltd.); tetraethyl orthosilicate(TEOS) (AR), Tween 80 (AR), polyvinyl alcohol (AR), acetic acid (AR), Shanghai Aladdin Biochemical Technology Co., Ltd. Main instrument: Scanning Electron Microscope, SU8020, Japan HITACHI Company; Fourier Transform Infrared Spectrometer, NICOLET IS10, Thermo Fisher Scientific Company; Differential Scanning Calorimeter, DSC214, NETZSCH Scientific Instruments Co., Ltd., Germany. 2.2 Preparation of Phase Change Microcapsules and Functional Ink Weigh a certain amount of paraffin and Tween 80 into a 250 ml three-necked flask and stir at 70 °C for 1 h. Then add 100 g of PVA aqueous solution with a mass fraction of 1.5%. Continue stirring for 1 h, then drop 15 mL of tetraethyl orthosilicate solution and 0.02 g of acetic acid solution with mass fraction of 10% successively, and stir at heat preservation for 1 h. After the reaction was completed, the microcapsules were obtained by filtration, washed thoroughly with petroleum ether and distilled water, and dried at 55 °C for 24 h to obtain microcapsule samples. The phase change microcapsule ink was prepared with printing transparent paste, resin and color paste in a certain proportion.

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3 Results and Discussion 3.1 Surface Morphology of Phase Change Microcapsules Figure 1 shows the SEM pictures of phase change microcapsules synthesized by TEOS at different dropping accelerations. It can be seen that under different dropping accelerations, the microcapsules are all quasi-spherical, and there are obvious clusters of nanoparticles on the spherical surface. When the TEOS dropping rate is 22.4 ml/min, the particle size of the microcapsules is smaller than the phase change microcapsules synthesized under the condition that the dropping rate is 16.8 ml/min. 3.2 Thermal Performance Analysis of Phase Change Microcapsules According to the DSC curve (Fig. 2), it can be seen that the latent heat of phase change of the coated microcapsules is lower than that of the uncoated pure phase change material. E=

Hm + Hf × 100% Hm0 + Hf 0

(1)

Among them, Hm and Hf are the melting and solidification enthalpies of the phase change microcapsules; E is the encapsulation efficiency of the microcapsules; Hm0 and Hf 0 are the melting and solidification enthalpies of paraffin wax. According to formula (1) and the values in Table 1, it can be calculated that the coating rate of the phase change microcapsules at the dropping rate of 16.8 ml/min and 22.4 ml/min are 45.53% and 57.5%, respectively.

Fig. 1. SEM photos of microcapsules with different dropping acceleration rates: (A) dropping acceleration is 16.8 ml/min; (B) dropping acceleration is 22.4 ml/min

Fig. 2. DSC curve of phase change microcapsules: (a) Heating curve; (b) Cooling curve. Note: A: paraffin, B: dropping acceleration is 16.8 ml/min, C: dropping acceleration is 22.4 ml/min

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Table 1. Coating rate of phase change microcapsules Sample

Tm /°C

Tf /°C

Hm /J · g−1

Hf /J · g−1

Paraffin

50.11

53.22

128.83

121.72

16.8 ml/min

50.85

54.28

62.47

51.63

45.53%

22.4 ml/min

47.26

51.88

71.21

72.87

57.5%

E

3.3 Analysis of Thermal Insulation Performance of Phase Change Microcapsule Ink Table 2. Adhesion levels of phase change microcapsule inks on different substrates Substrate

Offset paper Non-woven cotton Coated paper Kraft paper Aluminum foil

Adhesion 0

0

0

1

1

3

The test of adhesion in Table 2 adopts the grid method. Grade according to ISO 12944 international standard. In domestic standards, identified as adhesion to 1–2 level is qualified, so phase change microcapsule ink can be applied to most of the substrate surface. 3.4 Analysis of Thermal Insulation Performance of Phase Change Microcapsule Ink For paper cups coated with common ink, the temperature of the surrounding environment is much lower than the temperature of the hot water, so the temperature of the hot water gradually decreases with the passage of time. In order to alleviate the speed at which the temperature of hot water decreases, the surface of the paper cup is printed with ink with phase change microcapsules. It can be seen from Fig. 3 that the starting temperature of the hot water is 68 °C, and the core material paraffin in the phase change microcapsules is liquid at this temperature. When the temperature is lower than about 55 °C, the paraffin

Fig. 3. Insulation performance test curve of phase change microcapsule ink

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in the phase change microcapsule undergoes a phase change to release heat, which slows down the rate of decrease in hot water, indicating that the phase change microcapsule ink has a certain heat preservation ability within the phase change temperature range.

4 Conclusion In this work, the non-polluting paraffin wax is used as the core material, and silica is used as the wall material. The microcapsules in which the inorganic substance encapsulates the organic phase change material have stable thermal and mechanical properties. The changes of the morphology and phase change enthalpy of the phase change microcapsules under different dropping accelerations of TEOS are studied. The phase change microcapsule was prepared into phase change heat preservation ink, and it was found that the microcapsule ink had good heat preservation performance. In the future, combining phase change energy storage materials with microcapsule technology and ink technology can greatly expand the application fields of novel materials and functional inks. Acknowledgements. This work was supported by the Key Scientific Research Project of Beijing Municipal commission of Education (KZ201910015016), the National Natural Science Foundation of China (21776021), the BIGC Key Project (Ec202004), and the Cross training Plan for High Level Talents in Beijing.

References 1. Fan, X., Qiu, X., Lu, L., et al.: Full-spectrum light-driven phase change microcapsules modified by CuS-GO nanoconverter for enhancing solar energy conversion and storage capability. Solar Energy Mater. Solar Cells 223, 110937 (2021) 2. Xw, A., Cz, A., Kai, W.B., et al.: Highly efficient photothermal conversion capric acid phase change microcapsule: silicon carbide modified melamine urea formaldehyde. J. Colloid Interface Sci. 582, 30–40 (2021) 3. Li, F., Jiao, S., Sun, Z., et al.: Self-repairing microcapsules with aqueous solutions as core materials for conductive applications. Green Chem. 23(2), 927–934 (2021) 4. Chen, S.-Y., Sun, Z.-C., Li, L.-H., et al.: Preparation and characterization of conducting polymer-coated thermally expandable microsphere. Chin. Chem. Lett. 28(3), 658–662 (2017) 5. Wang, G.X., Xu, W.B., Hou, Q., et al.: Microwave-assisted synthesis of poly (ureaformaldehyde)/lauryl alcohol phase change energy storage microcapsules. Polym. Sci. Ser. B 58(3), 321–328 (2016)

Preparation and Particle-Size Analysis of Small-Scale Thermal Expansion Microcapsules Zhenzhen Li, Zhicheng Sun(B) , Gongming Li, and Zhitong Yang Beijing Engineering Research Center of Printed Electronics, School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. The wall material of thermally expandable microcapsules (TEMs) is a thermoplastic polymer, and the core material is the low boiling-point alkane. When the microcapsule is heated to a certain temperature, the core material vaporizes to produce internal pressure, and the microsphere shell begins to soften and expand after reaching the wall material transition temperature, thus obtaining the three-dimensional effects. This article with n-hexane as the core material, acrylonitrile, methyl methacrylate, methyl methacrylate as monomer polymerization of wall materials, thermal expansion can be synthesized by suspension polymerization method microcapsules. The structure and performance of the prepared thermally expanded microcapsules were characterized by scanning electron microscope (SEM), laser particle size analyzer (PSDA), thermal dilatometer (DIL), and thermogravimetric analyzer (TG), etc. Furthermore, the performance of thermal expansion microcapsules with different sizes was compared so as to optimize the synthesis process, and then the specific practical applications of thermal expansion microcapsules were developed. Keywords: Thermal expansion microcapsules · Small particle size · Physical foaming · Suspension polymerization

1 Introduction Thermal expansion microcapsule is a core-shell microcapsule prepared by wrapping low boiling point physical foaming agent alkanes with thermoplastic shell [1]. In the current preparation methods, the suspension polymerization is widely used, and the monomers are often nitrile-containing substances with gas barrier properties [2–4]. Generally, as the intermolecular force of the monomer becomes the larger, the wall material transformation temperature and microcapsule expansion temperature will be higher [2]. The thermal expansion microcapsule has a simple preparation method, low raw materials and superior expansion performance. In recent decades, microcapsules have been widely used in medicine [2, 3], of aeronautics and astronautics [5], food, cosmetics and textiles [1], and other fields. Nowadays, there are more and more applications for thermally expanding microcapsules, such as wallpaper [5, 6], Braille, paper cups, clothing and so on. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 401–405, 2022. https://doi.org/10.1007/978-981-19-1673-1_59

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How to reduce the particle size and broaden the application range of thermal expansion microcapsules has become a difficult problem for everyone to study. This article mainly reduces the particle size of the microcapsules by changing the agitator speed and time of water-oil mixing during the preparation of the microcapsules to a smaller micron level.

2 Experiment 2.1 Materials and Instruments Sodium hydroxide, magnesium chloride hexahydrate, sodium chloride, n-hexane, sodium lauryl sulfate, 1,4-butanediol dimethacrylate, Shanghai Aladdin Biotechnology Co., Ltd. Acrylonitrile 99+%, Beijing Inno Chemical Technology Co., Ltd. Methyl methacrylate (stabilized with 6-tert-butyl-2,4-xylenol), methyl acrylate (stabilized with MEHQ), 2,2 -Azobis(isobutyronitrile), Tokyo Chemical Industry Co., Ltd. Laser particle size analyzer, Mastersizer 2000, UK; scanning electron microscope, Gemini 300, Germany; thermogravimetric analyzer, NETZSCH STA 449 F5/F3 Juipter, Germany; thermal dilatometer, NETZSCH DIL 402 PC, Germany. 2.2 Preparation Preparation of the oil phase: Add acrylonitrile, methyl methacrylate, methyl acrylate, azobisisobutyronitrile and n-hexane in a beaker in a mass ratio of 7:2:1, 2,2 Azobis(isobutyronitrile), 1,4-butanediol dimethacrylate, stir evenly with a magnetic stirrer. Preparation of the water phase: Sequentially add magnesium hydroxide, sodium lauryl sulfate, sodium hydroxide, sodium chloride, and a certain amount of deionized water into a three-necked flask and stir uniformly to obtain a reaction water phase. Make the oil phase fully and evenly dispersed in the water phase. Heat to 65 °C, stir mechanically at 700–1000 r/min, react for 15–20 h, cool, discharge, repeatedly wash and filter, and blast dry Bake in an oven at 50 °C to gain powder microcapsules.

3 Results and Discussion 3.1 Particle Size Distribution According to particle size distribution (Fig. 1 and Table 1), the average particle size (D50) is 12 µm, and D90 is 24 µm, that is, 90% of microcapsules have particle size

Fig. 1. Particle size distribution of microcapsules

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less than 24 µm. According to the analysis of the microcapsules particle size is small, the average particle size between 8–20 µm, microcapsules particle size distribution is mainly concentrated on a small scale. Table 1. Particle size characteristics parameters of microcapsules Diameter

D10

D50

D90

µm

2

12

24

3.2 Surface Topography From Fig. 2 above, it can be seen from the SEM photos that there is no obvious agglomeration of the microcapsules, and the core material is completely wrapped by the shell. The average particle size of the microcapsules is about 12 µm. The structure of the thermally expanded microcapsules after foaming is spherical and has a perfect appearance. Therefore, the SEM photos can prove that the thermally expandable microcapsules were successfully prepared, and the shape of the microcapsules was spherical.

Fig. 2. SEM pictures of thermal expansion microcapsules

3.3 Thermal Analysis The TG curve in Fig. 3 shows the content of foaming agent after decomposition and monitors the polymer. The dried samples were raised from room temperature to 600 °C at a rate of 10 °C/min in N2 atmosphere. At 80 °C to 200 °C, the weight loss rate is about 28%, indicating that the content of medium foaming agent in microcapsules accounts for about 28%. When the temperature exceeds the transition temperature (Tg) of the wall material of the microsphere, the microsphere begins to expand. The n-hexane gas of the gasification core material is released rapidly and weightlessness is rapid. The initial temperature of weight loss is about 80 °C, close to the boiling point of n-hexane 69 °C.

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Fig. 3. TG curves of microspheres

It can be concluded that the starting point of T is determined by the boiling point of the enveloped foaming agent. The fastest weight loss rate occurs at 170 °C. After 200 °C shell began to burst, microcapsule decomposition. As shown in Fig. 4, the ordinate dL/L0 represents the ratio of the volume of the microcapsules after heating expansion to the original volume, the thermal expansion curve shows the specific expansion ratio of the microcapsules, and the microcapsules rupture when heated from room temperature to 300 °C. During the heating process, the wall material of the microcapsule softens and the overall volume decreases. Then reaches the boiling point of the core material n-hexane, and the microcapsule begins to expand to its maximum volume. As the heating continues, if the temperature is too high, the microcapsules will begin to rupture, releasing the n-hexane contained in the inside and reducing the volume instantly. When the temperature is increased to 300 °C, the wall materials of the microcapsules are decomposed completely. It can be from Fig. 4 knows that the wall material of the microcapsule begins to soften at 70 °C, and decreases in volume after being squeezed. It expands rapidly at 170 °C and reaches the peak value, and the expansion ratio is about 2 times.

Fig. 4. Thermal expansion curves of microspheres

4 Conclusions In summary, thermal expansion microspheres were synthesized by suspension polymerization applying acrylonitrile-methyl methacrylate (MMA) and methyl methacrylate as

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wall materials and n-hexane as core materials. Its structure and properties were characterized by scanning electron microscopy (SEM) and thermal analysis (TG). SEM images show spherical shape and uniform particle size distribution. Through thermal analysis, 80 °C is the initial expansion temperature, and 170 °C reaches the maximum expansion temperature. The laser particle size analyzer showed that 8–20 µm was the average particle size of microcapsules, and the particle size of microspheres was distributed in a small range. Acknowledgements. This work was supported by the Key Scientific Research Project of Beijing Municipal commission of Education (KZ201910015016), the National Natural Science Foundation of China (21776021), the BIGC Key Project (Ec202004), and the Cross training Plan for High Level Talents in Beijing.

References 1. Hai, F., et al.: Influence of electrolytes on thermal expansion microcapsules. J. Macromol. Sci. A 56(1), 104–114 (2019) 2. Yasuhiro, K., Yosuke, I., Kenjiro, O.: Effects of the chemical structure on the heat resistance of thermoplastic expandable microspheres. J. Appl. Polym. Sci. 96, 1306–1312 (2005) 3. Jonsson, M., Nordin, O., Kron, A.L., Malmstrom, E.: Influence of crosslinking on the characteristics of thermally expandable microspheres expanding at high temperature. J. Appl. Polym. Sci. 118, 1219–1229 (2010) 4. Jonsson, M., Nordin, O., Malmstrom, E., Hammer, C.: Suspension polymerization of thermally expandable core/shell particles. Polymer 47, 3315–3324 (2006). https://doi.org/10.1016/j.pol ymer.2006.03.013 5. Chen, S.Y., Sun, Z.C., Li, L.H.: Preparation and characterization of thermally expandable microspheres. Mater. Sci. Forum 852, 596–600 (2016) 6. Hu, J., Zheng, Z., Wang, F., Tu, W., Lin, L.: Synthesis and characterisation of thermally expandable microcapsules by suspension polymerisation. Pigm. Resin Technol. 38(5), 280–284 (2009)

Design of Chlorophyll Ink and Its 2D Printing Applications Hongxia Wang(B) , Ludan Hu, Liang Ma, and Yuhao Zhang(B) College of Food Science, Southwest University, Chongqing, China [email protected], [email protected]

Abstract. In this study, chitosan was used to stabilize chlorophyll for preparing edible inks for 2D printing. The suitable ink is selected for screen printing onto substrates and the quality of the printed product is outstanding with high definition. The design of edible inks based on chlorophyll and chitosan provides a new direction for the functional inks. Keywords: Chlorophyll · Chitosan · 2D printing

1 Introduction Ink is of vital importance for current modern life, which can be used for decorating products, delivering information and broadening visibility, but traditional ink has unsafe factors as being applied directly on to food. Edible ink is drawing attention from researchers and enterprises. However, the application of edible inks on the market at present is in a small amount with the limited fields. We have researched and prepared edible inks based on chitosan and edible pigments that are especially aimed at inorganic pigments, and found that edible inks have excellent printability. However, chitosan stabilizing natural green pigments is rarely investigated. The development of green inks based on chitosan would be promising in significantly promoting the evolving of ink industry.

2 Materials and Methods 2.1 Materials Chitosan (90%; 5 kDa, LWCOS; 10 kDa, MWCOS; 100 kDa, HWCOS) was purchased from Solarbio (China), chlorophyll (85%) and cyclic oligosaccharides (90%) was supplied from Aladdin (China).

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 406–410, 2022. https://doi.org/10.1007/978-981-19-1673-1_60

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2.2 Preparation of Edible Inks Chitosan was added into acetic solution (2 wt%) by blending for developing chitosan solutions (7 wt%). Cyclic oligosaccharide (3 wt%) was dispersed into glycerol solution (0.5 wt%). Chlorophyll (CH, 10 wt%) was then dispersed in cyclic oligosaccharideglycerol solution, which were then added into chitosan solutions by stirring to obtain edible inks. Inks with LWCOS (2.4%, 2.9% and 3.4%), MWCOS (2.4%, 2.9% and 3.4%) and HWCOS (2.4%, 2.9% and 3.4%) were coded as CH-LWCOS1, CH-LWCOS2 and CH-LWCOS3; CH-MWCOS1, CH-MWCOS2 and CH-MWCOS3; CH-HWCOS1, CH-HWCOS2 and CH-HWCOS3, respectively. 2.3 Precipitation Rate and Scanning Electron Microscopy (SEM) The precipitation rate of CH is calculated via dividing the mass of the precipitated CH by the total mass of CH. SEM were recorded by Phenom Pro (Phenom World, Netherlands). 2.4 Rheological Analysis As for 3 Interval Thixotropy Test (3ITT) [1, 2], three test phases of 0.1 s−1 (lasting 60 s), 300 s−1 (lasting 5 s) and 0.1 s−1 (lasting 120 s) cloud emulate screen printing process. Recovery rate is calculated by dividing viscosity at the third phase by viscosity at the first phase. Yield stress was measured by shear stress-shear rate test. Hershel-Bulkley (Eq. (1)) model was calculate yield stress [3, 4]. τ = τ0 + k1 · (γ )n1

(1)

Where (τ , τ0 , γ , k 1 and n1 ) = (shear stress, yield stress, represents shear rate, material coefficient and flow index). 2.5 2D Printing The optimized edible ink was printed onto substrate by screen printing machine (Shenzhen Jin Ruixin Machinery Plant).

3 Results and Discussion There is severe precipitation in edible ink CH-LWCOS1, CH-LWCOS2, CH-LWCOS3, CH-MWCOS1, CH-MWCOS2, CH-MWCOS3, and even CH-HWCOS1 after 2 months of storage (Fig. 1A). Therefore, CH-HWCOS2 and CH-HWCOS3 were chosen for 3ITT test. They had shear thinning properties with little difference in shear ramp test. Figure 1B shows 3ITT results reaching the different stable viscosities at three shear rates. As the inks were firstly subjected to a low shear rate 0.01 s−1 , viscosities were high, emulating the status of inks on the mesh at the initial of screen printing. Subsequently, shear rate rose to 300 s−1 , the viscosity of edible inks decreased greatly due to break-up of the internal structure in the ink matrix [5], modeling screen-printing process in which inks

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flowed through mesh and were printed onto substrates. Finally, shear rate was reduced to 0.01 s−1 , the viscosities almost recovered to the original values and the ink structure was recovered to a new state, emulating the post-printing condition. Liu et al. believed that hydrogen bonding presents a high viscosity at low shear rates, and the structures are disrupted rapidly with the application of high shear rates, but upon the removal of shear stress the viscosity recovered rapidly [6], which explained the recovery phenomenon of inks. The recovery rates are 90% and 79% for CH-HWCOS2 and CH-HWCOS3 (Fig. 1C), respectively, illustrating the high percentage of CH-HWCOS2 to reconstruct the internal network. Therefore, CH-HWCOS2 possesses excellent thixotropy, confirming the high potential for practical screen printing.

Fig. 1. Precipitation of edible inks (A); 3ITT tests (B) and recovery rates (C) of CH-HWCOS2 and CH-HWCOS3

SEM images of CH-LWCOS2, CH-LWCOS3, CH-MWCOS2, CH-MWCOS3, CHHWCOS2, and CH-HWCOS3 were investigated to study their micro morphology, for providing insights of micro dispersion status of CH in ink matrix. Figure 2A–D shows SEM images of LWCOS with crack particles, MWCOS with entire sphere shapes, HWCOS with flat flakes and CH with particle shapes, respectively, indicating the obvious differences among COS with different molecular weights and the characteristics of CH. CH-LWCOS2 shows incomplete fixation of CH (Fig. 2E) and CH-LWCOS3 (Fig. 2F) shows partial fixation of CH, due to the high content of LWCOS; CH-MWCOS2 displays partial fixation of CH (Fig. 2G) and CH-MWCOS3 displays fixation with uneven appearance (Fig. 2H). In comparison, CH-HWCOS2 (Fig. 2I) exhibits well fixation and dispersion of CH, while CH-HWCOS3 (Fig. 2J) exhibit well dispersion with small flakes, which was due to high content of HWCOS leading to ununiform surface. Proper content HWCOS promotes the fixation of CH and help form the structured ink matrix, especially for CH-HWCOS2. Based on the above analysis, CH-HWCOS2 was further investigated in terms of yield stress. The yield stress reflects the minimum pressure required to initiate the flow of inks, below which the inks show more solid-like behaviour rather than liquid-like behaviour, which cannot be printed out unless driving pressure > yield stress [6, 7]. Shear stressshear rate curve of CH-HWCOS2 is illustrated in Fig. 3A. After being fitted by the Hershel-Bulkley equation, the yield stress is calculated as τ0 0.17782 Pa (Fig. 3B), which is relatively satisfactory for screen printing. Moreover, flow index parameter (n1 ) further defines the shear-thinning behavior (n1 < 1) (Fig. 3B).

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A

Entire

E

D

C

B

Particles

sphere Flat flakes

Incomplete fixation

Crack particles 10 µm

H

G

F

10 µm

10 µm

409

I

Fixation of CH

10 µm

10 µm

J Well fixation Well fixation

Partial fixation Partial fixation 10 µm

10 µm

10 µm

10 µm

10 µm

Fig. 2. SEM of inks COS1 (A), COS2 (B), COS3 (C), CH (D), CH-LWCOS2 (E), CH-LWCOS3 (F), CH-MWCOS2 (G), CH-MWCOS3 (H), CH-HWCOS2 (I) and CH-HWCOS3 (J)

A

B

Fig. 3. Shear stress-shear rate curve (A) and fitting results (B) of CH-HWCOS2

CH-HWCOS2 (200 Pa s in viscosity, 300 nm in diameter, and pH 6.0) was subsequently screen-printed onto paper (Fig. 4A). The mesh was designed with special logos for exploring printing possibility. After printing, the printed products were dried at 25 °C with 50% RH, with high drying speed. The prints are recorded after 6 months. Figure 4B shows the clear logos of “Southwest University” and even the small logo possesses the clean edge. The small-sized words and patterns illustrate visible outlines, with high definition.

A

B

Clear edge and high definition

Small logo

Large logo

Fig. 4. Screen printing illustration (A) and screen printing of edible ink CH-HWCOS2 (B)

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4 Conclusion Edible inks were prepared based on HWCOS and cyclic oligosaccharide for practical screen-printing application. The obtained ink possessed high storage stability, great 3ITT thixotropy, (recovery rate up to 90%), and uniform SEM morphology, with yield stress 0.17782 Pa (Hershel-Bulkley equation). The printed products have clear edge and high definition, proving the printability of CH-HWCOS2. Edible inks based on HWCOS enrich the ink types and have potential in food printing. Acknowledgements. The authors acknowledge the support from Natural Science Foundation of Chongqing (cstc2020jcyj-msxmX0995), Fundamental Research Funds for the Central Universities of China (SWU119069), National Natural Science Foundation of China (31671881; 31972102), and Chongqing Research Program of Basic Research and Frontier Technology (cstc2018jcyjA0939).

Notes. The authors declare that they have no conflicts of interest to this work.

References 1. Montoya, J., Medina, J., Molina, A., Gutiérrez, J., Rodríguez, B., Marín, R.: Impact of viscoelastic and structural properties from starch-mango and starch-arabinoxylans hydrocolloids in 3D food printing. Addit. Manuf. 39, 101891 (2021) 2. Amorim, P.A., d’Ávila, M.A., Anand, R., Moldenaers, P., Van Puyvelde, P., Bloemen, V.: Insights on shear rheology of inks for extrusion-based 3D bioprinting. Bioprinting 22, e00129 (2021) 3. Kamali, F., Saboori, R., Sabbaghi, S.: Fe3O4-CMC nanocomposite performance evaluation as rheology modifier and fluid loss control characteristic additives in water-based drilling fluid. J. Petrol. Sci. Eng. 205, 108912 (2021) 4. Mohamed, A., Salehi, S., Ahmed, R.: Significance and complications of drilling fluid rheology in geothermal drilling: a review. Geothermics 93, 102066 (2021) 5. Man, L., Song, C., Wan, B.: Influence of prepolymer molecular weight on the rheology and kinetics of HEUR-thickened Latex Suspensions. Progr. Organ. Coat. 156, 106223 (2021) 6. Liu, Z., et al.: Linking rheology and printability of a multicomponent gel system of carrageenanxanthan-starch in extrusion based additive manufacturing. Food Hydrocol. 87, 413–424 (2019) 7. Hamilton, C.A., Alici, G., Andin Het Panhuis, G.: 3D printing vegemite and marmite: redefining “breadboards.” J. Food Eng. 220, 83–88 (2018)

Study on Preparation and Performance of Thermal Expansion Fluorescent Ink Zhitong Yang, Zhich eng Sun(B) , Zhenzhen Li, and Gongming Li Beijing Engineering Research Center of Printed Electronics, School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing 102600, China [email protected]

Abstract. Thermal Expansion fluorescent ink has the advantages of strong adhesion, easy processing, low cost, etc., and can be used in securities anticounterfeiting, functional clothing and other fields. In this study, an in-situ polymerization method was used to synthesize thermally expandable microcapsules (TEMs) with n-hexane as the core material and acrylonitrile (AN), methyl methacrylate (MMA) and methyl acrylate (MA) monomers as the wall material. Thermally expandable microcapsules, binders, color paste and fluorescent materials are mixed in a certain proportion to prepare an ink with three-dimensional and fluorescent functions. The ink is transferred to different substrates by screen printing, meanwhile, the surface morphology, adhesion and other properties of the fluorescent ink are tested with laser confocal microscope, ISO 12944 international standard cross-cut method and other instruments. The research results show that the ink is evenly distributed on different substrates, has good film-forming properties and strong adhesion. Therefore, the foaming fluorescent ink can beautify the product and has an anti-counterfeiting effect, which develop the application of functional ink. Keywords: Thermal expansion microcapsules · Screen printing · Fluorescent ink

1 Introduction Fluorescent ink [1] is a kind of functional ink with fluorescent pigment widely used in ticket printing, banknotes, and other security counterfeiting fields. Fluorescent pigments are functional luminescent pigments. The difference from general pigments is that when ultraviolet light is irradiated, they can absorb a certain form of energy, and excite photons to release the absorbed energy in the form of low visible light, thereby producing different hues of fluorescence [2, 3]. However, the single type and monotonous functions of fluorescent inks currently on the market hinder the further development of fluorescent inks. Microencapsulation is a technology that wraps solids, liquids, and gases in a polymer film to form a core-shell structure [4]. Thermal expansion microcapsules are a kind of polymer particles made by using microcapsule technology. The shell is composed of air-tight thermoplastic polymer, and the core material is an organic solvent with © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 411–415, 2022. https://doi.org/10.1007/978-981-19-1673-1_61

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a low boiling point. The boiling point of the organic solvent is lower than the glass transition temperature of the polymer shell [5]. After heating to a certain temperature, the polymer shell softens, and the low-boiling organic solvent acts as a foaming agent. The internal vapor pressure generated by gasification makes the microcapsules expand and enlarge. After the thermally expandable microcapsules are foamed, they will have a stable shape within a certain temperature range, and if they continue to be heated, the size of the microcapsules will instantly shrink due to the bursting and escape of the internal foaming agent. In this work, the thermally expandable microcapsules and fluorescent ink are combined to prepare a thermally expandable fluorescent anti-counterfeiting ink that can be used for fine screen printing, which gives the fluorescent ink a three-dimensional function. Through characterization, it is found that the prepared foaming fluorescent ink has strong adhesion, uniform film formation, high cost performance and significant anti-counterfeiting effects.

2 Experiments 2.1 Materials and Instruments Main reagents: Acrylonitrile, absolute ethanol, Beijing Yinuokai Technology Co., Ltd.; phosphor, Qingdao Uso Chemical Technology Co., Ltd.; n-hexane, methyl methacrylate, methyl acrylate, sodium lauryl sulfate, hydrogen Sodium oxide (AR), magnesium chloride hexahydrate, Shanghai Aladdin Biochemical Technology Co., Ltd.; acrylic acid filmforming resin, Qingdao Linke Industry and Trade Co., Ltd.; transparent paste, Jiangshan Well Fine Chemical Co., Ltd. Main instruments: Constant speed automatic stirrer, D2004, Shanghai Zhiwei Electric Co., Ltd.; screen plate, 100 mesh, Beijing Ingram Printing Machinery Co., Ltd.; screen printing machine, OS-300FV, Ou Laite Printing Machinery Co., Ltd.; vacuum Drying box, DZF-6020, Shanghai Boxun Co., Ltd.; Confocal laser microscope, VKX200, Keyence Co., Ltd.; Scanning electron microscope, SU8020, HITACHI, Japan; Electronic balance, PX224ZH, Ohaus Instrument Co., Ltd.; magnetic stirring Device, DF-101S, Gongyi City Yuhua Instrument Co., Ltd. 2.2 Preparation of Thermal Expansion Fluorescent Ink Preparation of Thermal Expansion Microcapsules Preparation of Physical Foaming Microcapsules. Step 1: Add magnesium hydroxide to a three-necked flask, then add sodium nitrite (0.02 g), sodium chloride (1 g) and absolute ethanol (0.5 g) in sequence, and let them homogenize for a period of time. Step 2: Add the monomers acrylonitrile (14 g), methyl methacrylate (4 g), methyl acrylate (2 g), initiator azobisisobutyronitrile AIBN (0.43 g), crosslinking agent to the beaker in turn Dimethacrylic acid-1,4-butanediol (0.04 g) and foaming agent n-hexane (8.77 g), fully stirred with a magnet (300 rpm, 1 h) to form a uniformly mixed oil phase. Step 3: Mix the water and oil phase, and use a magnetic stirrer to make the oil phase fully dispersed in the water phase (1000 rpm, 1 h). Step 4: Pour the homogeneously stirred oilin-water droplets into a three-necked flask, heat in a water bath and adjust the temperature

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to 65 °C. After about 8 h of reaction, preliminary physical foaming microcapsules can be obtained. The preparation process of heat-expandable microcapsules is shown in Fig. 1.

Fig. 1. Preparation process of thermal expansion microcapsules

Preparation of Thermal Expansion Fluorescent Ink. Thermal Expansion fluorescent ink was prepared by mixing transparent paste (50%), polyvinyl alcohol (25%), phosphor powder (5%), thermal expansion microcapsule (10%), defoaming agent (0.2%) and leveling agent (0.8%) according to a certain mass ratio. By post-processing the printed sample, a final product with special effects can be obtained. For example, after the thermally-expandable microcapsule ink to be printed is cured, it is heated at 120 °C for 1min on a heating plate to obtain a sample with three-dimensional fluorescence effect.

3 Results and Discussion 3.1 Anti-counterfeiting Effect of Phase Change Microcapsule Ink As shown in the Fig. 2, after heating, the microcapsules begin to expand, the diameter becomes significantly larger, and the thickness of the ink layer increases accordingly, resulting in a three-dimensional print. The ink distribution is more uniform, and the pattern appears soap bubble type, with a sense of fluffing embroidery. It can be seen from figure a that the fluorescent anti-counterfeiting ink before foaming is difficult to see with the naked eye, and the milky white protrusions can be clearly seen after the ink is heated and expanded. Under the irradiation of ultraviolet rays, the ink appears sky blue, and it has a fleece embroidery feeling when touched by hand, which has a significant anti-counterfeiting effect. The ink has an obvious fluorescence emission peak on the fluorescence spectrum, indicating that the ink has a good fluorescence effect (a is unfoamed, b is foamed, and c is the luminous effect of the ink after being irradiated by the ultravioletlamp.).

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Fig. 2. Thermal expansion type fluorescent ink printing effect picture and fluorescence spectrum

3.2 Performance Analysis of Thermal Expansion Fluorescent Ink The film-forming properties of microcapsule inks were analyzed by laser confocal microscope. The following Fig. 3 shows the laser confocal microscope before and after the expansion of various substrates such as paper jam, cotton cloth and non-woven fabric.

Fig. 3. Comparison before and after the expansion effect of fluorescent microcapsule ink on different substrates

3.3 Analysis of Adhesion Force of Thermal Expansion Fluorescent Ink According to the ISO 12944 international standard classification, the adhesion test adopts the cross-cut method with a spacing of 2 mm. Apply the ink to the substrate, pull 3–4 cm in parallel with the scratcher, there are six cut marks; then use the same method to be perpendicular to the former, and the cut marks are the same six times. In this way, many small squares are formed. Finally, use a soft brush to gently sweep forward and backward several times to assess the level. The specific results are shown in Table 1. In the domestic standard, it is deemed qualified if the adhesion reaches 1–2 level [6]. There are many small pores on the surface of non-woven fabric, cotton cloth and cardboard. When the ink is coated on the porous substrate, a part of it will penetrate into the pores, so that the ink and the substrate are tightly combined to form a mechanical bond. Therefore, the adhesion level on these substrates can reach 0, which is suitable for most printing substrates.

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Table 1. Adhesion of fluorescent microcapsule ink on different substrates Substrate

Non-woven fabric

Cotton

Paper jam

Kraft paper

Adhesion

0

0

0

1

4 Conclusions In this study, a thermal expansion microcapsule with n-hexane as the core material and acrylonitrile (AN), methyl methacrylate (MMA) and methyl acrylate (MA) monomers as the wall material was prepared by the suspension polymerization method. The heatexpandable microcapsules, binders, and fluorescent materials are mixed in a certain proportion to prepare an ink with dual functions of three-dimensional and fluorescent effects. Moreover, it is found that the fluorescent ink has good printability. It shows adhesion levels higher than domestic standards on cotton, cardboard, non-woven fabrics and other substrates, and the ink distribution is more uniform after heating. Under the irradiation of ultraviolet rays, the ink appears sky blue, and it has a frictional feeling when touched by hand, which has a significant anti-counterfeiting effect. In summary, the ink prepared in this study has excellent performance in adhesion and anti-counterfeiting performance. Meanwhile, the application of novel materials and fluorescent inks has been greatly expanded through the inking and printing applications of thermally expandable microcapsules. Acknowledgements. This work was supported by the Key Scientific Research Project of Beijing Municipal commission of Education (KZ201910015016), the National Natural Science Foundation of China (21776021), the BIGC Key Project (Ec202004), and the Cross training Plan for High Level Talents in Beijing.

References 1. Zhao, S., Gao, M., Li, J.: Lanthanides-based luminescent hydrogels applied as luminescent inks for anti-counterfeiting. J. Luminescence 236, 118128 (2021) 2. Dung Cao, T.M., Le Giang, T.T., Turrell, S., Ferrari, M., Van Lam Quang Vinh, T.T.T.: Luminescent ink based on upconversion of NaYF4:Er,Yb@MA nanoparticles: environmental friendly synthesis and structural and spectroscopic assessment. Molecules 26(4), 1041 (2021) 3. Wang, X., Tang, D., Wang, W.: Characterization of Pseudomonas protegens SN15-2 microcapsule encapsulated with oxidized alginate and starch. Int. J. Polym. Mater. Polym. Biomater. 70(10), 684–692 (2021) 4. Abdelhameed, M.M., Attia, Y.A., Abdelrahman, M.S., Khattab, T.A.: Photochromic and fluorescent ink using photoluminescent strontium aluminate pigment and screen printing towards anticounterfeiting documents. Luminescence 36(4), 865–874 (2020) 5. Hai, F., et al.: Influence of electrolytes on thermal expansion microcapsules. J. Macromolecul. Sci. A 56(1), 104–114 (2019) 6. Xu, W., Liu, X.: On-site inspection of the adhesion of anticorrosive coatings. In: International Seminar on Marine and Heavy Anticorrosion Coatings and Coating Technology. China Coatings Industry Association (2008)

Preparation and Printing Application of Sound-Absorbing Ink Gongming Li, Zhicheng Sun(B) , Xiaoyang Du, and Qingqing Zhang Beijing Engineering Research Center of Printed Electronics, School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing 102600, China [email protected]

Abstract. Noise pollution is everywhere in modern life, seriously affecting people’s quality of life, and causing serious harm to people’s physical and mental health. Therefore, the elimination and isolation of noise is an urgent problem to be solved. Traditional sound insulation engineering materials have high cost, large volume, and serious pollution, which bring a lot of inconvenience to actual production and application. Sound-absorbing inks as a kind of novel functional materials may help solve this problem. In this study, the foamed microspheres, crosslinking agents, binders, and pigments were formulated into the sound-absorbing ink in a certain proportion. Furthermore, the surface morphology and foaming height of the sound-absorbing ink was characterized before and after foaming. Moreover, the sound absorption performance and printability of the ink are also systematically studied. The results show that the sound-absorbing ink has a good sound-absorbing effect. Finally, the screen-printing process is used to transfer the sound-absorbing ink to the surface of different materials to obtain a functional printed product with a stable performance and good sound-insulating effects. Keywords: Sound-absorbing ink · Foamed microspheres · Noise reduction effect · Screen printing

1 Introduction As the population grows, population density increases, and per capita space decreases, noise pollution is seriously affecting people’s quality of life. Continuous noise pollution can also cause damage to people’s hearing and cause various diseases and accidents [1]. The main component of physical expansion microcapsules is thermal expansion microcapsules, which are spherical microcapsules composed of a low boiling point organic solvent as the core material and a thermoplastic polymer as the wall material [2, 3]. When the thermoplasticity of the microcapsule wall material polymer matches the pressure generated by the organic solvent vaporization of the core material, the microcapsule exhibits good thermal expansion performance. A large number of adjacent microcapsules will form a rougher surface and internal space, causing the energy of the sound wave to gradually weaken, so it can effectively absorb the energy of the sound wave. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 416–420, 2022. https://doi.org/10.1007/978-981-19-1673-1_62

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In this paper, the microcapsules, binders and pigment are mixed to form ink, which is printed on the surface of the substrate by means of screen printing. This investigation systematically analyzes the structure characteristics of thermally expandable microcapsule inks to improve the foaming performance on decorations and the sound absorption effect on different decorations [4]. Finally, the sound absorption performances of thermally expandable microcapsule inks printed on substrates were mainly researched and then the decorative materials with good sound absorption effects were obtained.

2 Experiments 2.1 Experimental Materials Thermal expansion microcapsules; color paste; transparent paste; solid wood board, Wall Cloth; Wallpaper; Polyester Fiberboard. 2.2 Instruments Scanning Electron Microscope, SU8020, HITACHI, Japan; Electric Heating Plate, PB3, Changzhou Guohua Electric Co., Ltd.; Silk screen, 100 mesh, Beijing Ingram Micro Printing Machinery Co., Ltd. 2.3 Preparation of Thermal Expansion Microcapsules Add monomer, initiator, crosslinking agent, foaming agent in turn to the beaker. Add Mg(OH)2 ·6H2 O and deionized water to the beaker, after both are completely dissolved, add NaOH and Sodium Dodecyl Sulfate (SDS) to the flask. Finally, Sodium Chloride, Sodium Nitrite, and Anhydrous Ethanol were added to get the aqueous phase. The oil phase was fully dispersed in the water phase by stirring and emulsifying. After heating and reacting for 8 h, the finished product is obtained. 2.4 Sound-Absorbing Ink Performance Test The thermal expansion sound-absorbing ink is printed on wallpaper, wall covering, solid wood board, polyester fiberboard by screen printing, then heated to 130 °C with an electric heating plate for 1 min. Fixing a closed wall panel model. Fix the foamed decorative material on the inner side of the wallboard model, putting in a constant and stable sound signal source, and leave a blank control group [4]. Using decibel meter to test the influence of foaming inks on the sound signals of four kinds of decorative materials.

3 Results and Discussion 3.1 Adhesion of Ink to Different Decorative Materials According to ISO 2409 crosscutting test, we divided the four decorative materials with the same spacing, pressure and speed drew the same grid again. After selecting the

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appropriate area, paste and remove the tape within 1.0 s. Keep the tape for reference and check the condition of the crosscut section [2]. We found that the surface of the grid wallpaper is completely smooth after pasting with single-blade adhesive tape, and there is no phenomenon of grid stratification. According to the judgment method of adhesion grade, its surface adhesion grade is 1. Three other substrate materials were also tested under the same conditions and a small portion of the ink was found to have been stripped by tape at the intersection of the surface. Vision is affected about 5% of the area. According to the adhesion criterion, the surface adhesion rate was judged to be level 1. ISO 12944 stipulates that adhesion must reach 1 level is qualified; In GB, when the adhesion reaches 1–2, it is qualified. Through experimental analysis, we can find that the adhesion level of sound-absorbing ink on four kinds of printing materials is qualified (Table 1). Table 1. Adhesion grade of samples on different substrates Printing materials

Wall covering

Wallpaper

Wood board

Polyester fiberboard

Adhesion grade

1

1

1

1

3.2 Morphology Analysis of Thermal Expansion Microcapsules Figure 1 is the SEM image of the antistatic physical expansion microcapsules. From the above Fig. 1a and c, we can observe the physical expansion microcapsules are in a collapsed state at room temperature. As shown in Fig. 1b and d above, we observed that the heated microcapsules have a uniform particle size, a smooth spherical appearance, and a hollow interior. When a large number of expanded microcapsules form a rough surface, it can effectively eliminate noise.

Fig. 1. SEM image of physical thermal expansion microcapsules

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3.3 Foaming Height of Sound-Absorbing Ink on Different Decorative Materials We can be found that due to the substrate surface roughness and absorbability is different, there will be different printing material surfaces of the ink foaming phenomenon. It can be seen from Table 2 that the foaming thickness of the other three materials is significantly higher than that of solid wood. Through the analysis, it is found that this is because the solid wood surface is smooth and dense, which contains less ink, resulting in a lower height after foaming. According to the above data, the foaming height of microcapsules on the substrate mainly depends on the nature of the substrate, and the commonly used decorative materials have a certain height, and the foaming height can give the decorative materials a certain beauty. Table 2. Changes in the foaming height of inks on different substrates Printing materials

Wall covering

Wallpaper

Wood board

Polyester fiberboard

Before foamed

0.35 mm

0.32 mm

1.50 mm

1.79 mm

After foamed

0.55 mm

0.48 mm

1.62 mm

1.96 mm

Foam height

0.20 mm

0.16 mm

0.12 mm

0.17 mm

3.4 Analysis of Sound Absorption Performance of Sound-Absorbing Ink It can be seen from the above Table 3 that after using the sound-absorbing ink, the four decorative materials all have a good attenuation effect on sound waves. Among them, the sound-absorbing ink absorbs sound waves most obviously in polyester fiberboard and wall coverings. The normal environment value of the experiment is 39.5 dB. The ambient noise is around 70 dB, the sound-absorbing ink can absorb 18 dB of ambient noise after being matched with the printing material, which can effectively reduce the noisy environment to a normal environment. Table 3. Test of noise cancellation ability of different materials Printing materials

Wall covering

Wood board

Wallpaper

Polyester fiberboard

Before foamed

65.4 dB

66.6 dB

72.5 dB

64.2 dB

After foamed

46.5 dB

49.3 dB

56.8 dB

45.8 dB

Absorbed difference

18.9 dB

17.3 dB

15.7 dB

18.4 dB

4 Conclusion In this paper, the thermal expansion microcapsules are prepared, and the morphology of the microcapsules is analyzed. Firstly, the microcapsules are formulated into soundabsorbing ink in a certain proportion, and then the ink prepared above is transferred to

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the surface of the four decorative materials by screen printing and foamed by heating. The results show that more ink can be accommodated because of the rough surface of wall coating and polyester fiberboard. The sound-absorbing ink has good adhesion on the surface of the substrate, and the overall foaming height is higher. The final soundabsorbing test also shows that the sound-absorbing ink is matched with the substates after printing and it has a better noise cancellation ability. Through the above analysis, it is found that the sound-absorbing ink can greatly eliminate the noise after matching with different decoration materials. Therefore, the sound-absorbing ink has a broad application prospect in indoor sound insulation decoration materials. Acknowledgements. This work was supported by the National Natural Science Foundation of China (21776021), the Key Scientific Research Project of Beijing Municipal commission of Education (KZ201910015016), the BIGC Key Project (Ec202004), and the Cross training Plan for High Level Talents in Beijing.

References 1. Luo, D.: Research on the Application Measures of Sound Insulation and Vibration Isolation Technology in Buildings. Qingdao Technological University (2018) 2. Zhang, W.: Research on the Structure and Performance of High-Efficiency Sound-Absorbing Fiber Materials. South China University of Technology (2017) 3. Junfeng, S., Li, R., Wang, L.: Microencapsulation technology and its latest research progress. Mater. Guide S1, 141–144 (2003) 4. Chen, S., Sun, Z., Li, L.: Preparation and characterization of thermal expansion microcapsules. Inf. Record. Mater. 16(06), 3–6 (2015)

Preparation and Conductive Properties of Thiophene Inks Xu Li1 , Lulu Xue1 , Shuping Gao1 , Xiangjun Guo1 , Hao Qi1 , Luhai Li1 , Meijuan Cao1(B) , Qinshuang Fang2(B) , Zhicheng Sun1 , Yonggang Yang1 , Lixin Mo1 , and Ruping Liu1 1 Beijing Engineering Research Center of Printed Electronics, Beijing Institute of Graphic

Communication, Beijing, China [email protected] 2 Wenzhou Globo Electronics Co., Ltd., Wenzhou, China [email protected]

Abstract. Thiophene polymers have attracted extensive attention due to their good solubility, conductivity and stability, as well as the changeable properties of α and β positions where various groups can be connected. In this paper, poly (5,5’-dibromo-2,2’-bithiophene) conductive ink was prepareed through UV polymerization, and the conductivity was studied by adjusting the dopant content. The results indicated that when I2 is 75 wt%, PSS is 15 wt% and MXene is 10 wt%, the minimum resistance of polythiophene ink was obtained. Keywords: Thiophene · Dopants · Conductivity ink · Photopolymerization

1 Introduction Conducting polymer is a kind of material that can be doped to make the electrical conductivity of polymer between semiconductor and conductor. In 1977, Heeger and MacDiarmid et al. [1] discovered polyacetylene for the first time, which exhibited high conductivity after doping. Subsequently, a series of heterocyclic compounds such as thiophene, carbazole, benzene and fluorene have also been successfully synthesized into polymers. These conductive polymers are used in the study of organic electronic devices, such as polymer light-emitting devices [2] and solar cells [3]. This paper introduces the preparation of a thiophene polymer conductive ink. Conductive ink was prepared with 5,5’-dibromo-2,2’-bithiophene as the reactive monomer, plus photoinitiator, various dopants and solvent DMSO. In the experiment, by adjusting the proportion of dopants several times, to seek the best ink formula. Then, the excellent conductive ink film was prepared by plasma treatment of substrate and UV induced treatment of ink. The photoinduced synthesis method [4] uses ultraviolet light, consumes less energy, is environmentally friendly, the polymerization speed is fast, and the reaction conditions are mild.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 421–426, 2022. https://doi.org/10.1007/978-981-19-1673-1_63

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2 Experimental Section In the experiment part, the conductive ink was first configured, the conductive film is then prepared by plasma treatment of the substrate and UV induced treatment of the ink, and the resistance value was measured. Conductive inks were prepared with 5,5’dibromo-2,2’-bithiophene (Macklin, 99%) as solute, I2 (Macklin, 99.8%), polystyrene sulfonate (PSS) (Macklin, 98%) and MXene (Sigma-Aldrich, ≥ 80%) as dopants, ultraviolet absorbent (Macklin, 98%) as initiator, and DMSO (Sigma-Aldrich, ≥ 99.5%) as solvent. Among them, thiophene solute is 100 mg, solvent DMSO is 2 ml, photosensitizer 10mg, optimates the ink formulation by adjusting dopant weight percentage. The configured ink is stirred for 8 h to ensure that the solution dissolves evenly. PET substrate will be treated with a plasma processor [5] to change the surface energy of the film to promote the spread of ink on the PET substrate. The supernatant was selected, rotated and coated on PET substrate, and then treated with ultraviolet light [6]. The purpose is to initiate polymerization of 5,5’-dibromo-2,2’-bithiophene monomers, generate and grow chains, and improve conductivity. After UV treatment, an ohmmeter was used to measure the resistance at a 1 cm interval. The size of the resistance data is the key to choosing the best ink formula. Table 1. The weight ratio of different dopants (1). Dopant

MXene (wt%)

PSS (wt%)

I2 (wt%)

TC-Ink01

0

0

100

TC-Ink02

0

20

80

TC-Ink03

0

40

60

TC-Ink04

0

60

40

TC-Ink05

0

80

20

TC-Ink06

0

100

0

Table 2. The weight ratio of different dopants (2). Dopant

MXene (wt%)

PSS(wt%)

I2 (wt%)

TC-Ink07

20

0

80

TC-Ink08

10

10

80

TC-Ink09

10

20

70

TC-Ink10

10

30

60

TC-Ink11

20

20

60

TC-Ink12

30

10

60

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Table 3. The weight ratio of different dopants (3). Dopant

MXene (wt%)

PSS (wt%)

I2 (wt%)

TC-Ink13

5

15

80

TC-Ink14

10

15

75

TC-Ink15

15

15

70

TC-Ink16

20

10

70

3 Results and Discussion There are two types of C atoms on the ringof monomer: α-C and β-C, of which Br atoms are attached to α-C. In the polymerization reaction, thiophene rings in the action of photosensitizer and various dopants, will be stripped of the Br atoms, and then the α-C atoms are linked together to form a polymer. In this way, the torsion Angle between the thiophene rings is lowest and the structure is more stable. The structural formula and polymerization reaction of 5,5’-dibromo-2,2’-bithiophene are shown in Fig. 1.

Fig. 1. Structural formula and polymerization reaction of 5,5’-dibromo-2,2’-bithiophene.

In the polymerization reaction, I2 atomic energy is widely distributed in the polymer gap, can improve the conductive ability of ink greatly [7]. According to the study, the polystyrene sulfonate (PSS) can play a combing role on system, improve the electrical conductivity by stretching the polymer chain, and disperse the aggregates of molecule [8]. MXene can increase the orbital of ions and accelerate the movement of ions, thus facilitating polymer formation [9]. In Table 1, the dopants are not added with MXene, in order to determine the better range of weight ratio of I2 and PSS doping. From Fig. 2a, the resistance value is smaller near TC-Ink 2 and TC-Ink 3. At this point, the weight ratio of I2 is between 60 wt% and 80 wt%, and the weight ratio of PSS is between 20 wt% and 40 wt%. Table 2 shows that after determining the range of weight ratio of I2 and PSS doping, MXene was added to seek the appropriate weight ratio of the three dopants. As shown in Fig. 2b, the resistance value is smaller near TC-Ink 8 and TC-Ink 9. At this time, the weight ratio of I2 was between 70 wt% and 80 wt%, the weight weight of PSS was around 20 wt%, and the weight ratio of MXene was around 10 wt%. Table 3 and Fig. 3 confirm that TC-Ink 14 is the formula for the optimal dopants weight ratio. At this point, I2 is 75 wt%, PSS is 15 wt% and MXene is 10 wt%, the minimum resistance of polythiophene ink was obtained and the resistance was about 4 k.

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Fig. 2. The resistance value varies with (a) the weight percentage of each dopant in samples (01–06); (b) the weight percentage of each dopant in samples (07–12).

Fig. 3. The resistance value varies with the weight percentage of each dopant in (13–16).

As you can see from Fig. 4a, the absorption peak at 1437 cm−1 is the symmetric stretching vibration of the thiophene ring C = C. The absorption peak at 1020 cm−1 is the in-plane bending vibration of Cβ -H, and the absorption peak at 1314 cm−1 belongs to the resonance absorption of the Cα -Cα single bond. The absorption peaks at 1654 cm−1 should be attributed to the absorption of carbonyl groups which come from the oxidation of the thiophene ring. It was found that the characteristic absorption peak of α-α linked thiophene ring appeared at 771 cm−1 which indicated that the polythiophene was indeed obtained by UV treatment. These are the characteristic absorption peaks of polythiophene, indicating that the product is a thiophene polymer. Figure 4b shows the UV-Vis spectrum of the conductive thiophene ink. The ink has a wide absorption in the range of 380–450 nm, with the maximum absorption occurring at 437 nm. The wide absorption peak distribution indicating that the structure of the sample is much more complex, rather than a single structure. These characteristics indicate that the conjugation degree of the sample is obviously enhanced after polymerization, and the structure of the sample becomes more planar.

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Fig. 4. (a) The FTIR and (b) UV-Vis absorption spectra of the samples.

4 Conclusion and Prospect In this study, we adjusted the weight percentage of various dopants to optimize the ink formulation. When I2 is 75 wt%, PSS is 15 wt% and MXene is 10 wt%, the overall characteristics of the ink are preferable, and the resistance value is smallest. As can be seen from FTIR and UV-Vis spectra, thiophene polymers were indeed formed, and the 5,5’-dibromo-2,2’-bithiophene monomer may be polymerized by Cα -Cα linkage. The mechanism of thiophene monomer polymerization is still uncertain and unclear, and further research is needed. The smallest resistance value stops at about 4 k, which may be attributed to the organic materials’ inherent restriction itself. Although our research has made some progress to extent, further optimization is needed in terms of film stability and resistance reduction. In the future, we will improve it mainly from the aspects of changing photoinitiator, dopant, and processing technology, as much as possible to meet the future demand on RFID, electron device, solar cell, etc. Acknowledgements. This work was supported by the Personnel Exchange Program of the 43rd Regular Meeting of China-Czech Committee for Science and Technology Cooperation (43-7), Science and Technology General Project of Beijing Municipal Education Commission (No.KM201910015011), National Natural Science Foundation of China (No.21706016).

References 1. Shirakawa, H., Louis, E.J., MacDiarmid, A.G., et al.: Synthesis of electrically conducting organic polymers: halogen derivatives of polyacetylene, (CH)x . J. Chem. Soc., Chem. Commun. 16, 578–580 (1977) 2. Zheng, H., Zheng, Y., Wang, J., et al.: Polymer light-emitting displays with printed cathodes. Surf. Coat. Technol. 358, 228–234 (2019) 3. Saito, M., Osaka, I.: Impact of side chain placement on thermal stability of solar cells in thiophene–thiazolothiazole polymers. J. Mater. Chem. C 6(14), 3668–3674 (2018) 4. Sangermano, M., Sordo, F., Chiolerio, A., et al.: One-pot photoinduced synthesis of conductive polythiophene-epoxy network films. Polymer 54(8), 2077–2080 (2013) 5. Tamai, T., Watanabe, M., Kobayashi, Y., et al.: Surface modification of PEN and PET substrates by plasma treatment and layer-by-layer assembly of polyelectrolyte multilayer thin films and their application in electroless deposition. RSC Adv. 7(53), 33155–33161 (2017)

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6. Lei, L., Li, F., Zhao, H., et al.: One-pot synthesis of block copolymers by ring-opening polymerization and ultraviolet light-induced ATRP at ambient temperature. Polym. Chem. 56(7), 699–704 (2018) 7. Fan, L., Xu, X.: A simple strategy to enhance electrical conductivity of nanotube-conjugate polymer composites via iodine-doping. RSC Adv. 5(95), 78104–78108 (2015) 8. Ouyang, J.: “Secondary doping” methods to significantly enhance the conductivity of PEDOT: PSS for its application as transparent electrode of optoelectronic devices. Displays 34(5), 423–436 (2013) 9. Chen, S., Xiang, Y., Xu, W., et al.: A novel MnO2 /MXene composite prepared by electrostatic self-assembly and its use as an electrode for enhanced supercapacitive performance. Inorg. Chem. Front. 6(1), 199–208 (2019)

Research on Adhesion of UV Gravure Ink on PET Film Chen Zhang, Beiqing Huang(B) , Xianfu Wei, and Hui Wang School of Printing and Packaging Engineer, Beijing Institute of Graphic Communication, Beijing 102600, China [email protected]

Abstract. Gravure printing is widely used in China because of its excellent printing quality and high printing speed at present. However, traditional gravure inks have many disadvantages, such as volatile solvents and slow drying speed. UVLED ink is used because it does not contain volatile solvents and is cured quickly by UV light source gradually. Plastics are widely used in daily life based on their quality and easy to form. However, plastics generally have shortcomings such as low surface energy, which makes it difficult for ink to spread and wet. The curing speed and volume shrinkage caused by this problem plague the application of plastic films in the UV gravure field. Therefore, it is very meaningful to develop a UV gravure ink with good adhesion in the plastic films. This study explored the influence of monomers and polymers of free radical and cationic systems on volume shrinkage, curing degree, wetting effect and adhesion through the method of formula testing. In this research, the factors affecting the ink adhesion on PET film were obtained. Keywords: UV-LED gravure ink · Volume shrinkage · Adhesion

1 Introduction With the continuous development of the printing and packaging field, social environmental protection requirements for inks have gradually increased. UV inks have become the most concerned new inks with their many advantages such as wide adaptability [1]. UV ink produces a polymer high-density cross-linked structure during the curing process, which not only has a high degree of toughness, but also has anti-pollution. In addition to printing on ordinary substrates, it also applies to non-absorbent materials such as films, plastics, metal, etc. Wang Bin of our research group has prepared UV gravure inks with good color density and put forward more ideas about this [2–5]. As the most widely used substrate for printing, plastic film plays an irreplaceable role in daily life. However, due to its low surface energy and lack of polar groups, it is difficult for general ink to adhere and print [6, 7]. Qu et al. studied the hardness of UV ink on PET film and obtained some data on adhesion, but did not study the curing effect and wettability of the coating [8]. Therefore, it is necessary to optimize the adhesion of UV ink on the plastic substrate. In order to develop UV gravure inks with excellent printability and good adhesion, this © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 427–434, 2022. https://doi.org/10.1007/978-981-19-1673-1_64

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experiment explores the effects of monomers, prepolymers and various properties on adhesion. The results of this experiment can further expand the application of UV inks and plastic substrates in printing and packing.

2 Experimental 2.1 Materials Oxyethoxyethyl acrylate (EOEOEA), alcohol acrylate (HDDA, DPGDA, TPGDA, NPGDA, PETA), 4-acryloyl morpholine(ACMO) and trimethylolpropane tripropionate (TMPTA) were sponsored by Tianjin Tianjiao Radiation Curing Materials Co., Ltd. Polyester acrylate and polyurethane acrylic resins were provided by Zhanxin Resin (Shanghai) Co.,Ltd. 3,4-Epoxycyclohexylmethyl-3’,4’-Epoxycyclohexane Carboxylate (TTA21,TTA21P,TTA26) and 1,2-Epoxy-4-epoxyethylcyclohexane (TTA22) were purchased from Jiangsu Tetra New Material Technology Co., Ltd. 3,3’-[Oxybis(methylene)] bis [3-ethyloxetane](OXT-3), 3-Ethyl-3-(hydroxymethyl) oxetane(OXT-1), 3-Ethyl-3(methacryloyloxymethyl) oxetane(OXT-049), 3-Ethyl-3-oxabutanemethanol(OXT-101) were supplied by Hubei Gurun Technology Co., Ltd. Polyester acrylate and polyurethane acrylic resins were provided by Zhanxin Resin (Shanghai) Co., Ltd. Bisphenol A epoxy resin (E44) was purchased from Shandong Tianmao Technology Co., Ltd. Phthalocyanine blue pigment was supplied by Shenzhen Lihua Co., Ltd. The pigment dispersant (670) was purchased from Shanghai Kaiyin Chemical Co., Ltd. Photoinitiator 819 and DETX were kindly provided by Tianjin Jiuri Chemical. Triarylsulfonium salt (IK-1) was purchased from Nanjing Hengqiao Chemical Material Co., Ltd. 2.2 Preparation of UV Ink The synthesis of UV ink was performed through two steps. In the first step, we add color paste (25%), prepolymer (7%), monomer (63%) into a beaker, and stir in a 30 °C constant temperature water bath for 10 min. In the second step, Add photoinitiator (5%), raise the temperature to 40 °C and stir for 30 min. The PET film was placed on the RK gravure printer and ink was added to print to obtain a 150LPI sample. 2.3 Characterization The curing speed was detected by a Semray UV curing conveyor belt (Heraeus, Germany). The UV ink sample on the PET film with a metal printing rod (12 μm), using UV-LED curing light source (395 nm, 14 w/cm2 ) to cure it. Determine the maximum curing speed by adjusting the conveyor speed. In this study, touch method and infrared spectrum to evaluate the speed and curing degree of the ink. The degree of curing is estimated by the torsion peak area of the C = C double bond at 816 cm−1 . Infrared spectrum is measured by ThermoFisher Scientific Nicolet IS10. The viscosity of the sample is tested by AR2000 rheometer (American TA) at 25°C. Parallel plate rotors use 60 mm aluminum plates and we record the viscosity data at the shear rate of 1 s−1 . The data of viscosity is in mPa•s.

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The surface tension is tested by K100 surface tension meter (KRUSS) in mN/m. The contact angle is measured by DSA30S from KRUSS. The objective standard for testing ink adhesion in this experiment is to refer to the cross-cut test method of national standard GB/T9286–1998. The method of measuring volume shrinkage in this experiment is the pycnometer method. The mass of the pycnometer itself is m0 . Use the pycnometer to test the mass of liquid m2 and the mass of medium water m1 of the UV gravure ink before curing. Use a pycnometer to test the liquid density ρ 1 of the UV gravure ink after curing, the density ρ 3 of the solid after curing, and the density ρ 2 of the medium water (the density of water at 25 °C). Use the density of the UV gravure ink before and after curing to calculate the volume shrinkage rate of the tested sample. The formula is as follows: The formula for calculating liquid density ρ1 is as follows: ρ1 =

m2 − m0 × ρ2 × 100% m1 − m0

(1)

The solid density ρ 3 is measured using a specific gravity balance (DH-120M). The formula for volume shrinkage is as follows: SR =

(ρ3 − ρ1 ) × 100% ρ3

(2)

3 Results and Discussion 3.1 Effect of Monomer Types on the Adhesion of UV Gravure Ink The main function of the monomer is to dissolve and dilute the oligomer and reduce the viscosity of ink. Monomer has the greatest impact on performance. According to the difference of molecular structure and reaction principle, monomer is divided into two systems: radical monomers and cationic monomers. The two series of monomers are discussed below. Influence of Free Radical Monomers on the Adhesion and the Curing Speed of UV Gravure Ink. When we are studying the effect of monomer on adhesion, we remain free radical polymers, photoinitiators and cyan paste unchanged. We change the type of monomer. The influence of free radical monomer on the adhesion of UV gravure ink is shown in Table 1:

Table 1. The influence of free radical monomers on the adhesion and the curing speed Monomer Adhesion Curing Speed

ACMO

EOEOEA

HDDA

NPGDA

DPGDA

TPGDA

TMPTA

4

2

3

3

4

3

3

70

15

15

15

18

25

40

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We can see from the Table 1 that the UV gravure ink of the free radical system has poor adhesion. All the monomers had poor adhesion except EOEOEA, which reached adhesion level 2. For this reason, we studied the influence of volume shrinkage, wettability and curing degree on adhesion. The results of the volume shrinkage of free radical monomers are shown in Fig. 1.

Fig. 1. Volume shrinkage of free radical monomers

Volume shrinkage in Fig. 1 shows that the volume shrinkage of the free radical system is very high. Because the monomer most commonly used in free radical photo polymerization is acrylate monomer, the molecular interaction distance is shortened from the unsaturated double bond van der Waals force interaction distance before polymerization to the covalent bond distance after polymerization, so the volume shrinkage rate is usually relatively large. It can also be seen that EOEOEA has the smallest volume shrinkage and the best adhesion. HDDA, DPGDA, NPGDA, and TPGDA have larger volume shrinkage and poor adhesion. In addition, the ink adhesion is also related to the degree of curing and contact angle. The degree of curing determines the drying degree of the UV ink and the film effect after printing. Incomplete curing of the ink will directly affect the adhesion of the ink on the printed product. The degree of curing of free radical monomers is shown in Fig. 2. It can be seen from the figure that except for ACMO, the conversion rate of the carbon-carbon double bond of the other monomers after curing is above 70% and the ACMO conversion rate is the lowest. Adhesion is also the worst. NPGDA and HDDA have the same degree of curing and the same adhesion. From the perspective of adhesion performance, although DPGDA has the best curing degree, the adhesion is poor. The contact angle describes the spreading effect of the ink on the PP substrate and directly determines the printability. The contact angle of the free radical monomer on the printing substrate is shown in Fig. 3.

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Fig. 2. Double bond conversion of free radical monomers

Fig. 3. Contact angle of free radical monomer

Figure 3 shows that the interface contact angle of free radical monomers is basically between 10° and 25°. The contact angle of EOEOEA is small and the wetting action is the best, so the adhesion is better than other monomers. TMPTA has a larger contact angle on the substrate, but its adhesion is better than ACMO. Compared with TPGDA and NPGDA, DPGDA has a larger contact angle and poor adhesion. ACMO has a large contact angle and therefore poor adhesion. In summary, in terms of adhesion, monomers with a small volume shrinkage rate and a higher degree of curing are more moderately attached, and the contact angle has a small effect on adhesion. Effect of Cationic Monomers on the Adhesion of UV Ink. We remain the cationic polymers, photoinitiators and additives unchanged when we are studying the effect of cationic monomers on adhesion. The influence of cationic monomer on the adhesion of UV system is listed in Table below:

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Monomer Adhesion Curing speed

GR43

GR41

TTA21

TTA21P

TTA26

TTA22

OXT101

OXT049

2

3

1

1

1

2

2

3

48

7

35

40

30

25.5

15

7

It can be seen from Table 2 that the adhesion of the cationic system is better, among which TTA21, TTA21P and TTA26 have reached the level 1 of adhesion. The overall adhesion of the remaining monomers is better than that of the free radical system. Like free radicals, we also explored the action of the volume shrinkage, curing degree and contact angle of cationic monomers on adhesion. The results of volume shrinkage of the cationic monomer are shown in Fig. 4.

Fig. 4. Volume shrinkage of cationic monomers

Volume shrinkage in Fig. 4 shows that the cationic system is smaller than radical system. When epoxy monomers used are polymerized, the chain structure formed by ring opening is larger than the molecular structure of the monomer, which offsets part of the volume shrinkage. It can also be concluded that the smallest volume shrinkage of TTA21, TTA21P and TTA26 leads to better adhesion. The degree of curing of the cationic monomer is expressed by the ratio of epoxy group ring opening after curing. The result is shown in Fig. 5. Unsaturated bond in Fig. 5 shows that ring-opening ratio of epoxy group of the cationic monomer is lower than the double bond conversion rate of the free-radical monomer, indicating that the curing degree of the cationic system is lower than that of the free-radical system. The contact angle results of cations are shown in Fig. 6.

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Fig. 5. Bond conversion of cationic monomer.

Fig. 6. Contact angle of cationic monomer.

The angle date in Fig. 6 explains interface contact angle of cationic monomers is generally larger than that of radical ink, and the contact angles of TTA21 and TTA21P are the largest, but the adhesion is the best. This shows that the contact angle is not a decisive factor for adhesion, and that adhesion is mainly determined by the volume shrinkage rate. 3.2 Influence of Polymer on Adhesion of UV Gravure Ink Polymer is the basic skeleton of UV curing system, and the product performance after UV curing is related to the prepolymer. Because only one type of cationic prepolymer E44 was used in this study, the types of cationic prepolymers were not studied separately. We only studied free radical prepolymers. The results are listed in Table below. Table 3. The influence of radical polymer on the adhesion Prepolymer

EB811

EB870

EB270

EB150

R7480

LED01

UT30096

6361–100

DR-U317

V400

Adhesion

3

3

3

3

3

4

3

3

3

3

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It can be seen from Table 3 that the change of the prepolymer has almost no effect on adhesion. And the influence of polymer on volume shrinkage is also small. The result is listed in Table 4. Table 4. Volume shrinkage of radical polymer Prepolymer

EB811

EB870

EB270

EB150

R7480

LED01

UT30096

6361–100

DR-U317

V400

Volume shrinkage

7.66

8.56

7.53

8.81

8.19

7.97

9.01

8.75

8.35

8.95

It can be seen from Table 4 that the free radical prepolymers have little influence on the volume shrinkage which is about 10. The data results in the same adhesion.

4 Conclusions To obtain a high adhesion of UV-curable ink on PET film, Ink prepared by different monomers and prepolymers was used to print on PET film, and the influence of volume shrinkage, curing degree and contact Angle of different monomers and prepolymers on adhesion was studied in this experiment. According to the data, volume shrinkage value of the monomer is below 5%, the curing degree of the ink is above 80%, and the contact angle with the PET film is below 20°, and a good adhesion effect can be obtained. Acknowledgements. This paper is sponsored by Program of Green Printing. The paper is also funded by Publishing Technology Collaborative Innovation Center and National Innovation Program for College Students. We also gratefully acknowledge the support from BIGC Project (No.Eb202002) and Institute of Ink Rheology, BIGC.

References 1. Zhang, H.: Research on UV Curing Ink used for PE Substrate. University of Chemical Technology, Beijing (2008) 2. Huang, B., Wang, B., Ma, L., Wang, H., Wei, X.: Research on curing performance and printability of magenta UV-LED Gravure Ink. In: Zhao, P., Ye, Z., Min, Xu., Yang, Li. (eds.) Advanced Graphic Communication, Printing and Packaging Technology. LNEE, vol. 600, pp. 630–641. Springer, Singapore (2020). https://doi.org/10.1007/978-981-15-1864-5_86 3. Yi, B.: How to improve the adhesion of UV ink. Printing Today 05, 74–75 (2015) 4. Zhang, H., Chen, Z.: Research on the relationship between the adhesion and chemical structure of UV-curable monomers and oligomers on plastic substrates. Paint Ind. 47(06), 7–11 (2017) 5. Yang, L., Hao, Y., Zhou, Z.: The effect of additives on the adhesion of water-based UV-curable screen printing plastic inks. Packag. Eng. 09, 32–33+40 (2008) 6. Zhang, Q., Wang, H., Xie, Y., Ren, B.: Ultraviolet (UV) curing system adhesion promoter. Guangdong Chem. Ind. 41(21), 86–87 (2014) 7. Fouassier, J.P.: Photoinitiator, Photopolymerization and Photocuring. Munich, Munich Hanser (1995) 8. Qu, X., Wang, Z., Tan, S.: Study on the influence of high hardness UV-curable coatings on adhesion. Paint Ind. 42(11), 36–38+42 (2012)

Effect of Kaolinite’s Addition to Inking Oil on Printability of Water-Based Inks Tao Hu1 , Zehui Zhong1(B) , Jiaying Zhong2 , Peng Gao1 , Fanqi Zeng3 , and Zijun Yuan3 1 Hunan University of Technology, Academy of Packaging and Material Science,

Zhuzhou, China [email protected] 2 Xiangtan University, Academy of Chemistry, Xiangtan, China 3 Changde Jinpeng Printing Co., Ltd., Changde, China

Abstract. Objective: To investigate the influence of kaolin on the printability of water-based ink. Methods: Use kaolin to prepare diluent, adding different amount of diluent to compound three kinds of varnish, respectively marked as standard (0 g diluent),sample 1 (200 g diluent) and sample 2 (300 g diluent), then prepare these varnish into ink with five different types of colorants separately. Eventually, investigate their printability from the aspects of slip resistance, viscosity, pH value, bubbling, deposit and color rendering effect. Results: the addition of diluent to varnish can slightly reduce the anti-skid degree of water-based anti-skid ink, but does not affect the pH value of ink and its color effect. However, attention should be paid to its using after a long-term stasis for its viscosity will increase. Ink configurated as sample 1 will appear slight deposit phenomenon after being put in the oven for a period of time, the deposit can be re-dispersed to ink by given a full mix and stir and the ink can be used. But in sample 2 a large diluent content caused an obvious deposit phenomenon and might affect its printability. Conclusion: the water-based ink configurated as sample 1 can slightly improve the slip resistance of the ink and meet the printing requirements. Keywords: Diluent · Varnish · Water-based Ink · Printability

1 Introduction The advantages of water-based ink stand out compared to other ink both in printing performance and environmental friendliness, which significantly reduce the volatilization of organic matter and do no harm to health of the operator. Not flammable, tasteless and non-toxic, it has good safety performance without causing extra pollution [1–5]. While gravure printing water-based ink is mainly used in the food industry, adding kaolin diluent into the ink is less studied. In this article, different contents of kaolin were used to prepare diluent and added into three kinds of varnish separately, then these varnish are respectively mixed with five types of color paste to produce ink, whose printability were investigated in terms of slip resistance, viscosity, pH value, bubbling, sinking bottom © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 435–442, 2022. https://doi.org/10.1007/978-981-19-1673-1_65

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and color rendering effect. It is concluded that the sample 1 can suit the printing requirements. It has certain reference significance for the configuration and application range of water-based ink.

2 Experimental Materials and Methods 2.1 Raw Materials and Equipment Calcined kaolin, 78-D resin, 0212A resin, 1603, 140-A, 180, 181 antifoaming agent, 191 neutralizing agent. Grinding glass beads, A1-BK yellow pulp, A3-BK golden red pulp, A4-BK red pulp, A6 blue pulp, A7 green pulp, Guangdong Tianlong Ink Co., Ltd.; Zahn cups, manual color display wheel, pH meter, rapid dispersion tester for paint, IKA RW20 Digital, BGD 740/2 high-speed dispersion machine, precision OVEN, BIAGEDA Precision Instrument (Guangzhou) Co., Ltd. Anti-skid tester, Guangdong Tianlong Ink Co., Ltd. 2.2 Preparation of Water-Based Ink Preparation of diluent: Use four steel cans to weigh a total of 300 g of 78-D resin, 80, water and kaolin in an electronic balance. Add 200 g of ground glass beads. Then grinding with coating rapid dispersion tester, filter and bottle it after 3 h for later use. Preparation of ink mixing oil: Add certain proportion of 0212A resin, 1603, 140-A, 181 antifoaming agent, 191 neutralizing agent, 325 into three large beakers respectively. Add different amount of prepared diluent and mark it as standard(0 g) diluent, sample 1 (200 g diluent) and sample 2 (300 g diluent)respectively, using high-speed disperser to disperse at 3000 r/min for 1 h, then test its viscosity with Zahn cups. Dilute it with water until the viscosity reaches 15 s, bottle it for later use. Preparation of ink: Weigh 50 g of ink oil (standard/sample sample 1/sample 2), color paste (A1-BK yellow pulp/A3-BK golden red pulp/A4-BK red pulp/A6 blue pulp/A7 green pulp) 50 g. With 15 bottles of ink samples in total, use a blender to disperse for 1 min at 1000 r/min, and then cover the bottle for later use. 2.3 Analyzing and Testing Anti-skid Test. The test is based on the ink anti-skid specifications of Binxing Company. Cut the white cardboard into 10 cm * 30 cm strips. Clean and dty the anilox roller of color wheel. Drop the appropriate amount of ink into the gap between the anilox roller and the rubber wheel, evenly spread the color and dry the templet for testing. Cut the white cardboard into 5 cm * 5 cm, attach it to the metal weight with double-sided tape, facing the white surface outwards. Fix the pre-test sample paper on the tester board, place the metal weight with white cut board on the sample. Press the switch to lift the board automatically and slowly. After the weight falls, record the angle at which the board is lifted and use it as a reference for skid resistance. All kinds of ink should respectively use white paper and kraft paper, each test 4 times before taking average value.

Effect of Kaolinite’s Addition to Inking Oil on Printability

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Viscosity Test. This paper uses GB/T 13217.4-2008 liquid ink viscosity test method. Use the Zahn cups # 4 to test. Detect the viscosity of 15 bottles of ink samples after being prepared and standing for 36 h. pH Test. Measure 15 bottles of ink samples and 3 bottles of ink mixing oil with a pH meter for 3 times before taking average value. Bubble Test. Weigh 70 g ink sample into a large cylinder. Clean and dry the bubbling machine, and then put it into the measuring cylinder. Read the degree of liquid level height and record. Turn on the machine to the maximum bubbling rate. After 30 min, read and record the liquid level height and the highest liquid level height. Sedimentation Test. Cap and place15 bottles of ink samples into an oven at 60 °C. Remove them and cool to room temperature after 4 h. Stir the bottom of the bottle with an ink sharpener to observe the subsidence. Ink Contrast. Cuting the white card and krafting card into 10 cm * 30 cm strips standby, Keep the anilox roller of color wheel clear, clean and dry, and drop the right amount of standard/sample 1, standard/sample 2, sample 1/sample 2 ink respectively into the gap between the anilox roller and the rubber wheel, evenly spread the color. Use Aseri spectrophotometer to measure L * , a * and b * values of sample strips, then calculate the chromatism E*according to the formula to. The chromatism calculation formula:  (1) E = (L∗ )2 + (a∗ )2 + (b∗ )2

3 Results and Discussion 3.1 Analysis of Anti-slip Degree Water - based ink skid resistance is also an important printing adaptability, especially in the carton printing. In this experiment A1-BK yellow pulp, A3-BK golden red pulp and A4-BK red pulp are anti-skid and wear-resistant while A6 blue paste, A7 green paste are ordinary high-grade printing ink color paste. Thus the anti-slip degrees of the first three types of ink paste configuration are higher the latter two. The following table shows that in three types of anti-skid ink, the anti-slip degrees of sample 1 and sample 2 are slightly reduced compared to standard, but for A6 and A7 paste basically the skid resistance basically remained unchange. The addition of diluent will slightly reduce the anti-slip degree of non-slip ink, but the reduction is small so the ink can continue to be used (Table 1). 3.2 Viscosity Analysis Viscosity is one of the easy variables to change in the printing process, also a variable that has the largest and fastest impact on printing quality. The viscosity of water-based ink will affect many aspects of printing [6]. As can be seen from the following table, due to

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Table 1. Slip resistance of ink on white and kraft card paper (White cardboard/Kraft paper) A1-BK

A3-BK

A4-BK

A6

A7

Standard

30.7/31.2

31.7/31.4

30.2/30.3

27.6/26.6

27.9/27.4

Sample 1

29.4/29.2

30.4/30.8

29.7/28.9

27.6/26.9

27.5/27.9

Sample 2

29.0/29.3

30.7/30.4

28.6/29.0

27.1/26.8

27.0/27.8

a slightly higher viscosity of varnish in sample 1, the ink also has a high viscosity. When the ink is just prepared, the basic viscosity between ink made from same pastes show little difference. Only ink made from different pastes show large viscosity differences, which is the result of the viscosity difference of the paste itself. After standing for 36 h, all the ink viscosity rose higher while sample 1 and 2 significantly increased. This phenomenon is caused by the resin and kaolin content added into the diluent (Table 2). Table 2. Viscosities of inking oil and ink just prepared and rested for 36 h Varnish 0h/36 h

A1-BK 0h/36 h

A3-BK 0h/36 h

A4-BK 0h/36 h

A6 0h/36 h

A7 0h/36 h

Standard

15/17

20/23

16/23

15/18

16/23

15/19

Sample 1

16/21

23/25

17/26

17/23

18/26

17/23

Sample 2

15/21

22/25

15/25

16/22

17/24

16/21

3.3 pH Analysis The pH value of the ink will have a certain impact on the printing effect. When the pH value of water-based ink is between 8.2–9.5 its solid content, surface tension, viscosity value and other detected data show that its performance remains stable [7]. Therefore, it is appropriate to control pH between 8.2–9.5. As can be seen from the following table, all ink pH value is basically between 9.3–9.5, diluent added in sample 1 and 2 does not caused great impact on their pH value, and they are qualified in pH aspect (Table 3). Table 3. The pH values of inking oil and ink Varnish

A1-BK

A3-BK

A4-BK

A6

A7

Standard

9.70

9.40

9.49

9.56

9.46

9.47

Sample 1

9.62

9.32

9.45

9.52

9.49

9.30

Sample 2

9.47

9.35

9.43

9.51

9.40

9.33

Effect of Kaolinite’s Addition to Inking Oil on Printability

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3.4 Bubble Analysis After the bubble meter being placed in the measuring cylinder, the foam has completely overflowed the large measuring cylinder within 1 min. All ink samples have the same issue and thus a poor antifoaming ability. The reason for this is the low amount of 181 defoaming agent in the formula. Therefore, it is necessary to improve by increasing the content of defoaming agent. 3.5 Subsidence Analysis Water-based ink will not precipitate under normal circumstances. But due to the characteristics of the ink, such as the poor dispersion of resin, plus the charge/gravity difference of resin and pigments and high temperature exposure, coaglulation may still appear during the storage process. Slight sediment can be redistributed into the ink by stirring and shaking fully before use. More serious one will affect the quality of printing ink. It can be seen from the table below that the addition of diluent increases the subsidence phenomenon. Particularly in sample 2, whose subsidence phenomenon is more serious due to more diluent, it may affect the printing quality (Table 4). Table 4. Deposit degrees of inking oil and ink Varnish

A1-BK

A3-BK

A4-BK

A6

A7

Standard

0

0

1

0

0

0

Sample 1

0

1

1

0

1

0

Sample 2

1

3

3

2

2

2

Note: 0 indicates no subsidence, and bigger number represents more obvious subsidence

3.6 Ink Color Contrast During the printing process, final color presentation of the print is related to many factors. As an indispensable material in the printing process, the nature of ink itself largely affects or determines the final color presentation [8]. Use chromatism E to measure, generally the difference in color is hard to observe with naked eye when E ≤ 1,which meet the printing requirements. Table 5 is the final color difference between standard/sample and standard/sample 2 based on measured Lab values. As Figs.1, 2 and 3 shows, chromatism is basically less than 1 and do not show much difference under sufficient light condition. Thus, the result can meet the printing requirements.

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T. Hu et al. Table 5. E values of standard, sample 1 and sample 2 White cardboard sample 1

White cardboard sample 2

Kraft paper sample 1 Kraft paper sample 2

A1-BK

0.74

0.43

0.93

0.61

A3-BK

0.32

0.74

0.64

0.80

A4-BK

0.90

0.86

0.95

0.74

A6

1.14

0.61

1.25

0.95

A7

0.29

0.68

1.11

0.67

a

b

Fig. 1. Color comparison of A3 ink on white cardboard (left) and kraft paper (right)

a

b

Fig. 2. Color comparison of A6 ink on white cardboard (left) and kraft paper (right)

Effect of Kaolinite’s Addition to Inking Oil on Printability

a

b

441



Fig. 3. Color comparison of A7 ink on white cardboard (left) and kraft paper (right)

4 Conclusion Kaolin diluent has little effect on anti-slip degree of ordinary ink, it will slightly reduce the degree but does not affect its continued use. Also it will not affect the pH value of the ink or its color presentation. However, it should be noted that the viscosity will become larger after a long time of standing. Sample 1 ink appeared a little subsidence phenomenon after a period of time in oven, but after stiring the sediment can be re-dispersed into ink which can be used normally. Sample 2 ink has more obvious phenomenon due to more diluent addition, and it may affect the printing quality. In conclusion, sample 1 ink can meet the printing requirements. It has certain reference significance for the configuration and application range of water-based ink. Acknowledgements. National Key Research and Development Program Project “Research and Development of Intelligent Packaging Equipment for Slurry and Thick Food” and Innovation training program for college students (No.2018YFD0400705 and No. 4473/4474).

References 1. Hui, R., Jing, F., Lei, C., Xiaomeng, W., Lina, Y.: Brief analyze of the promotion of green printing ink on air pollution prevention and control. Plast. Packag. 30(06), 1–5 (2020) 2. Hui, S.: Research and analysis on the application of environmental protection ink in green cigarette pack. Leather Manuf. Environ. Technol. 2(02), 118–120 (2021) 3. Weiwei, L., Hongxia, W., Yuhao, Z., Ma Liang, D., Jie, P.L.: Preparation and food application of environmental-friendly inks based on gelatin. Food Ferment. Ind. 47(10), 265–270 (2021) 4. Gu, C.: Study on Synthesis and Properties of Water-based Ink Binder Resin. Modern Chem. Res, 4(24), 28–29 (2020) 5. Li, J.: Policy and technical recommendations on ln-depth VOCs control in printing and packaging industry during “the Fourteenth Five-Year Plan” period. Print China. 15(06), 18–19 (2020) 6. Zhu, Y.: Analysis of dispersing property of pigment in water-based ink and its influence on printability of ink. Adhesion, 43(07), 39–42+70 (2020)

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7. Xianmei, Z., Jin, D.: Effect of pH on waster-based ink printing quality. China Pulp 38(02), 41–44 (2017) 8. Chen Chunxia, Y., Yujuan, Z.J., Meiying, X.: Analysis on colorimetric results for flexographic printing with water-based ink. Paper Sci. Technol. 37(06), 70–77 (2018)

Comparative Study on the Retort Resistance and Color Reproduction of Water-Based Ink on Paper and Plastic Film Tao Hu1 , Zehui Zhong1(B) , Jiaying Zhong2 , Peng Gao1 , Fanqi Zeng3 , and Zijun Yuan3 1 Hunan University of Technology, Academy of Packaging and Material Science,

Zhuzhou, China [email protected] 2 Xiangtan University, Academy of Chemistry, Xiangtan, China 3 Changde Jinpeng Printing Co., Ltd., Changde, China

Abstract. Objective: To investigate the printability of water-based ink on paper and plastic film. Method: Use previously-prepared inks with the best printability in different kaolin diluents to make samples on different printing paper and plastic film respectively, analyzing their heat resistance, water resistance, adhesion and color reproduction. Results: The printing effect of water-based ink will be significantly worse after heated; when printed on the substrate, the density of the plastic film decreases the most if the substrate encounters water; water-based inks of all colors have the lowest adhesion to the plastic film, also the highest color difference and a poor color reproduction. Conclusion: Water-based inks with different content of kaolin diluent have poor printability on plastic films and needed to be improved from four aspects: heat resistance, water resistance, adhesion and color reproduction. Keywords: Water-based ink · Paper · Plastic film · Printability

1 Introduction With the control of volatile organic compounds emissions, water-based ink will gradually replace solvent-based ink in the field of food packaging. The water-based ink applied to food packaging plastic film must have good cooking resistance and color reproduction performance. The cooking resistance mainly includes heat resistance, water resistance and adhesion [1–7]. By adding certain proportion od kaolin into the diluter, the water-based ink has little effect on the skid resistance of ordinary ink. It will slightly reduces the skid resistance of anti-skid ink, but does not affect its continued use or pH value or color rendering effect. After a period of time in the oven, there will be some sediment. Although through shaking thoroughly before use can redistribute them into the ink and meet the printing requirements, whether it can be printed on the plastic film of food packaging remains uncertain. In this paper, kaolin ink was added and printed on four different papers and two © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 443–448, 2022. https://doi.org/10.1007/978-981-19-1673-1_66

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different plastic films, respectively. The heat resistance, water resistance, adhesion performance and color reproduction performance were compared and analyzed to explore the application of the water-based ink on food packaging plastic films. It improves the basis for the subsequent improvement of water-based ink printing suitability.

2 Experimental Materials and Methods 2.1 Raw Materials and Equipment Calcined kaolin, 78-D resin, 0212A resin, 1603, 140-A, 180, 181 antifoaming agent, 191 neutralizing agent. Grinding glass beads, red paste, green paste, yellow paste, black paste, Guangdong Tianlong Ink Co., Ltd. Zahn cups, coating rapid dispersion testing machine, IKA RW20 Digital, BGD 740/2 high speed dispersion machine, Beigeda Precision Instrument (Guangzhou) Co., Ltd. Eact spectrophotometer, Eact Co., Ltd.; HK-310B color display machine; TG gravimetric analyzer, TA Instruments. 2.2 Preparation of Water-Based Ink Preparation of diluent: A total of 300 g of 78-D resin, 180, water and kaolin were weighed by 4 steel cans in an electronic balance. Add 200 g of ground glass beads. Use the coating rapid dispersion tester to grind, then filter and bottle after 3 h. Preparation of ink mixing oil: Add certain proportion of 0212A resin, 1603, 140-A, 181 defoaming agent, 191 neutralizing agent, 325 in the large beaker. Add 200 g of the prepared diluent. Use a high speed disperser to disperse at 3000 r/min for 1 h at a rotating speed, using Japanese Zahn cups to detect the viscosity. Dilute it with water until the viscosity is 15 s, then bottle it. Preparation of ink: weigh 50 g red, green, yellow and black paste in each of the four sample bottles. Then add 50 g of the prepared mixing ink oil. Use a blender to disperse for 1 min at 1000 r/min speed, and then cover the bottle cap for use. 2.3 Analysis and Testing Heat Resistance Test. Weigh a small amount of dry film and test it on a thermogravimetric analyzer. Use nitrogen as protective gas with a temperature range of 30–500 °C and a heating rate of 10 °C/min. Water Resistance Test. Use gravure proofing machine to proof on different substrate. After natural drying, use X-rite528 spectrophotometer to measure and record the density and Lab values. Dip in a small amount of moisture with a cotton swab, evenly coat it on the substrate. After a while, use a paper towel to absorb excess water. Measure density and Lab values again after drying. Then compare the density values and calculate the Lab chromatism. The chromatism calculation formula:  (1) E = (L∗ )2 + (a∗ )2 + (b∗ )2

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Adhesion Performance Test. Prepare the scraped samples according to GB/T13217.1, and place them for 24 h. Stick the adhesive tape to the printing surface of the ink. Roll back and forth 3 times on the adhesive tape press machine. After leaving for 5 min, tear the tape in reverse with a little force by hand. Cover the uncovered part with 20 mm wide translucent mm paper. Record the number of cells of the ink layer and the removed layer. According to the formula: A = M/(M + N). Among them: A-ink adhesion fastness; M-the number of cells of ink layer; N-the number of cells of removed layer. Color Reproduction Test. Use gravure proofing machine to print on different substrate proofing, measure and record the LAB values of various strips by spectrophotometer. Then use 100 g offset paper spline as reference spline. Respectively calculate the chromatism data of other splines and 100 g offset paper splines and evaluate the color reproduction performance of water-based ink. Then contrast and analyze the color reproduction performance of paper and plastic film.

3 Results and Discussion 3.1 Heat Resistance Analysis Low temperature cooking refers to 110–115 °C;Medium temperature cooking refers to 121–125 °C; High temperature cooking refers to 130–135 °C. In the Fig. 1 below, th,e initial decomposition temperature is 186 °C. The decomposition temperature of 5% weightlessness is 286 °C. The decomposition temperature of 10% weightlessness is 309 °C. Basically it can meet the high temperature cooking condition. Cosidering the printing effect of water-based ink will be significantly worse after heating, it is necessary to pay attention not to store it in high temperature conditions for long.

Fig. 1. Water-based ink TG curve

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3.2 Water Resistance Analysis It can be seen from the following table that the density of splines decreased to varying degrees after wetting. The main reason is that after wetting, part of the ink dissolved into water, thus the density reduced. Among all the density of OPP and PET films decreased to a considerable extent. So if the water-based ink is expected to be printed on plastic film, its water resistance needs to be improved (Tables 1 and 2). Table 1. Density of different substrates before and after wetting Red

Green

Black

Yellow

150 g coated paper

1.83/1.63

1.74/1.64

1.97/1.80

1.47/1.31

120 g coated paper

1.76/1.58

1.67/1.55

1.92/1.73

1.43/1.32

100 g offset paper

1.88/1.58

1.67/1.42

1.94/1.78

1.38/1.29

80 g offset paper

1.86/1.69

1.69/1.64

1.87/1.76

1.46/1.31

OPP plastic film

1.85/1.09

1.71/1.11

1.86/1.03

1.42/0.78

PET plastic film

1.86/0.96

1.73/1.02

1.95/0.95

1.48/0.83

Table 2. E values of different substrates before and after wetting Red

Green

Black

Yellow

150 g coated paper

2.53

3.14

3.26

4.16

120 g coated paper

1.51

2.63

4.52

3.97

100 g offset paper

2.41

2.27

2.62

2.53

80 g offset paper

2.63

0.98

1.92

2.04

OPP plastic film

7.52

8.49

8.52

12.41

PET plastic film

9.83

10.46

9.28

10.49

3.3 Adhesion Performance Analysis According to the following table, adhesion fastness on coated paper and offset paper is considerable, and even better on paper. But the adhesion fastness on the plastic film is low. Food packaging plastic film mainly includes polar PET film and non-polar OPP film, etc. The ink on these two films cannot have a good adhesion. This is the main reason for the poor printing suitability of water-based ink on plastic film. Therefore, this aspect needs to be improved in subsequent experiments (Table 3).

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Table 3. Ink adhesion fastness of different substrates Red

Green

Black

Yellow

150 g coated paper

0.90

0.93

0.93

0.91

120 g coated paper

0.91

0.90

0.91

0.92

100 g offset paper

0.94

0.96

0.96

0.97

80 g offset paper

0.93

0.96

0.94

0.95

OPP plastic film

0.71

0.68

0.72

0.74

PET plastic film

0.73

0.79

0.80

0.76

3.4 Color Reproduction Analysis It can be seen from the table below that the chromatism between 80 g and 100 g offset paper is the smallest. The chromatism between coated paper and 100 g offset paper is slightly larger, and between OPP film and PET film and 100 g offset paper is particularly large, which does not conform to the ink industry color reproduction standards seriously. The main reason for this phenomenon is that water-based ink can not adhere to these two kinds of film well and only stays on the surface, causing large chromatism. The ability of color reproduction can be improved by improving the adhesion property of water-based ink in plastic film (Tables 4 and 5). Table 4. Lab values of various bars Lab

Red

Green

Black

Yellow

150 g coated paper

L* a* b*

51.09 57.01 52.83

51.33 −49.95 31.59

9.99 −0.03 −0.13

86.39 16.35 87.24

120 g Coated paper

L* a* b*

51.62 59.55 53.01

53.16 −49.69 31.30

7.75 −0.09 0.00

85.43 15.52 89.12

100 g offset paper

L* a* b*

47.92 64.00 53.49

42.97 −51.72 29.22

15.72 0.13 0.04

83.83 16.43 84.86

80 g offset paper

L* a* b*

46.31 58.32 52.60

43.91 −50.86 31.05

22.73 0.52 0.36

81.02 14.66 92.21

OPP plastic film

L* a* b*

56.62 45.23 52.53

56.24 −42.31 30.23

7.23 −0.23 −0.02

89.14 16.31 78.42

PET plastic film

L* a* b*

57.24 46.31 52.25

58.14 −43.32 31.45

6.41 0.24 −0.01

90.41 16.01 80.12

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T. Hu et al. Table 5. E values of various strips and 100 g offset paper Red

Green

Black

Yellow

150 g coated paper

7.29

8.87

5.73

3.50

120 g coated paper

5.81

8.74

7.97

4.64

80 g offset paper

5.97

2.23

7.03

8.07

OPP plastic film

20.71

16.30

8.50

11.39

PET plastic film

18.11

21.33

11.12

12.50

4 Conclusion The ink configured in this article has good printing adaptability on paper and meets the printing requirements. When it is printed on the food packaging plastic film, the heat resistance of the ink itself fits the conditions, but the printing effect should be significantly worse after heating; It has poor water resistance and its density will be greatly reduced after being wetted, affecting the color reproduction; It has poor adhesion and does not adhere well to OPP and PET films. This results in a larger chromatism compared with the paper after printing, which does not meet the printing requirements. The kaolin diluent water-based ink is not suitable for printing on plastic film, and it mainly needs to be improved from the aspects of water resistance and adhesion. Acknowledgements. National Key Research and Development Program Project “Research and Development of Intelligent Packaging Equipment for Slurry and Thick Food” and Innovation training program for college students (No.2018YFD0400705 and No. 4473/4474).

References 1. Hui, R., Jing, F., Lei, C., Xiaomeng, W., Lina, Y.: Brief analyze of the promotion of green printing ink on air pollution prevention and control. Plast. Packag. 30(06), 1–5 (2020) 2. Hui, S.: Research and analysis on the application of environmental protection ink in green cigarette pack. Leather Manuf. Environ. Technol. 2(02), 118–120 (2021) 3. Weiwei, L., Hongxia, W., Yuhao, Z., Ma Liang, D., Jie, P.L.: Preparation and food application of environmental-friendly inks based on gelatin. Food Ferment. Ind. 47(10), 265–270 (2021) 4. Gu, C.: Study on synthesis and properties of water-based ink binder resin. Mod. Chem. Res. 4(24), 28–29 (2020) 5. Li, J.: Policy and technical recommendations on in-depth VOCs control in printing and packaging industry during “the fourteenth five-year plan” period. Print China 15(06), 18–19 (2020) 6. Yupeng, W.: Testing method of VOC in coatings, inks and adhesives based on technical requirement for environmental labeling products. Coat. Protect. 42(05), 38–42 (2021) 7. Liu, R., Wu, J., Yang, L., Sun, X.: Discussion on the effects of different boiling temperatures on the barrier property of retort pouch. China Plast. Ind. 44(10), 109–110+114 (2016)

Preparation and Research Progress of Cellulose-Based Transparent Film Xin Li, Ling Cai, and Guangxue Chen(B) State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China [email protected]

Abstract. Since the rise of flexible optoelectronic devices in the 1970s, plastic has been used as the main substrate of optoelectronic devices. As an important structural unit of electronic devices, substrates have an enormous impact on the manufacturing methods and performance of electronic devices. The choice of different substrate materials has a great effect and influence on electronic devices. However, due to the non-renewability and non-biodegradability of plastics and the huge threat to the environment caused by their use, researchers have been looking for alternative materials for green plastics in recent years. With the efforts of many scientific researchers, due to their good mechanical properties, thermal properties, highly controllable optical properties, repeatability and biodegradability, cellulose-based films can become ideal substrates for optoelectronic devices. This article elaborates the preparation of nanocellulose, the transparent mechanism, classification and preparation methods of cellulose-based films, and prospects for its application prospects. Keywords: Cellulose · Transparent film · Mechanism · Classification

1 Introduction With the rapid development of science and technology and the increasing material needs of human beings, the scope of electronic products appearing in human daily life is becoming wider and wider, and they have become an inseparable part of our lives. However, while electronic products provide convenience to our lives, they also have a negative impact on the environment. For example, in the process of manufacturing electronic products, the overwhelming consumption of non-renewable energy and the massive use of non-degradable materials, etc. Although people have made a lot of efforts to solve such problems, there is still no efficient solution to this problem. In recent years, the development of materials that have the advantages of low cost, reusability, and no pollution, and their use in electronic devices, has always been a research hotspot. As an important structural unit of electronic devices, the substrate has a huge impact on the manufacturing method and performance of electronic devices. Therefore, the choice of substrate material has a very different effect and influence on electronic devices

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 449–454, 2022. https://doi.org/10.1007/978-981-19-1673-1_67

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[1]. Compared with common electronic device substrate materials Polyethylene naphthalate, Polyethylene terephthalate, Polyimide, epoxy resin, etc., cellulose, which is inexpensive and abundant in nature, has become a great choice for new substrate materials. It can be designed as an ideal substrate with adjustable mechanical and optical properties. A highly feasible and promising method in the field of devices [2, 3]. In addition, the application range of cellulose-based films is continuously being broadened, and its preparation, modification and application are all issues worthy of study. In this article, the transparency mechanism, classification and application of cellulose film will be explained in detail.

2 Preparation of Nanocellulose Cellulose is a linear polymer comprised of amorphous and crystalline regions. The principle of separating Nanocellulose from natural cellulose is that under the action of chemical reagents or mechanical force, the loosely arranged amorphous regions are degraded before the more regular crystalline regions, and nano-scale cellulose is obtained. The excellent properties of cellulose are related to its own crystallinity, morphology and size, but differences in fiber raw materials and preparation methods will lead to differences in these physical and chemical properties of cellulose. In this paper, nanocellulose is divided into three categories based on the different preparation methods and sources: Nanofibrillated cellulose (NFC), Nanocrystalline cellulose (NCC) and Bacterial nanocellulose (BNC) [4]. It is shown in Table 1. Table 1. The classification of nanocellulose materials Category

Raw materials

Preparation

Diameter

NFC

Wood, sugar beet, potato tuber, etc

Mechanical method

5–60 nm

A few microns

NCC

Wood, cotton, hemp plants, microcrystalline cellulose, etc

Acid hydrolysis

5–70 nm

100–250 nm

BNC

Low molecular weight sugars, alcohols

Bacterial synthesis

20–100 nm

Length

Variable

3 Mechanism of Cellulose Film Transparency As shown in Fig. 1, the structural unit skeleton in cellulose has ether bonds, C-C, CH, -OH functional groups that do not absorb sunlight, so that pure cellulose presents a transparent appearance [4]. Therefore, cellulose can be used as raw material for the preparation of transparent films. However, the optical properties of cellulose films of different raw materials vary greatly. When light is incident on the cellulose film, due

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to the smoothness of the film surface, back reflection will occur in a part of the light, causing in the loss of luminous flux. Secondly, there is a remarkably large difference between the refractive index of the air (1.0) existing in the pores of the film and the cellulose (1.5) as the substrate of the film, and the light scattering phenomenon into the film, the light transmittance is again reduced. It can be seen that the transparency of cellulose film is related to its surface morphology, thickness, bulk density, porosity and raw fiber. Studies have shown that by controlling the porosity of the cellulose film and the diameter, the optical properties of the film can be adjusted [5].

Fig. 1. Mechanism of cellulose film transparency

4 Classification of Cellulose Transparent Film According to the preparation methods and raw materials, cellulose transparent film can be divided into three categories: Micron-sized cellulose transparent films, regenerated cellulose films, and Nanocellulose films. 4.1 Micron-Cellulose Transparent Film Generally speaking, the preparation methods of Micron-cellulose transparent film can be divided into three types: dipping method, partial dissolution method and mechanical method [6–8]. The impregnation method uses oils, waxes, gums and other substances with a refractive index similar to that of cellulose as transparent agents to impregnate paper. Wen Hu et al. used the dipping method to drop CMC onto the opaque paper, and the haze and transparency value of the composite film obtained were as high as 82% and 90% [9]. Although the impregnation method is simple and efficient, the impregnation may have a negative impact on the appearance and printing performance of the paper. In the 19th century, the partial dissolution method first appeared. The principle is to dissolve part of the fibers on the surface of the paper, thereby filling the internal voids of the paper to make it appear transparent [10–12]. When Pengbo Lu used ionic liquids to obtain a highly transparent all-cellulose film. The transmittance and mechanical properties of the paper have been increased by 2.6 times and 2.0 times, respectively [11]. This method indicate that this process has the potential to be used in large-scale industrial production. The mechanical is that the direct use of Micron-sized cellulose as the raw material, through mechanical action to destroy the hollow structure of the fiber and split the

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fiber. The pulp after beating treatment can produce a dense structure in the papermaking process, and then the porosity is further reduced by super calendaring [13]. The cellulose transparent film prepared by this method is generally within the range of translucent film, and it is also accompanied by disadvantages such as poor mechanical properties, high energy consumption, and huge fiber damage. Therefore, in recent years, little research has been done on it. 4.2 Regenerated Cellulose Film Regenerated cellulose film (RCF) refers to a transparent film made from regenerated cellulose, which uses chemical reagents to dissolve the cellulose, and then extrudes or coats it [14, 15]. Although the chemical solvents have brought a burden to the environment, the green, economical and simple solvents has been developed. Through the efforts of scientific researchers, DMAc/LiCl, ionic liquids, and aqueous NaOH solutions have been introduced as reaction solvents to reduce the burden on the environment [16]. 4.3 Nanocellulose Film Nanopaper, generally refers to a transparent film prepared from cellulose nanofibers (CNF). Nanopaper has been valued in scientific research fields and enterprises. Through research, it is known that the Nanopaper prepared by CNF after TEMPO oxidation has better barrier properties and higher transparency than untreated transparent paper. Xiuxuan Sun et al. used TEMPO and a high-pressure microfluidizer to prepare oxidized CNC. The light transmittance and tensile strength TOCNC film of are as high as 98.4% (at 550 nm) and 236.5 MPa, respectively [16]. Nanopaper is generally prepared by vacuum filtration, so the thickness is usually less than 60 µm, resulting in mechanical properties that cannot meet the manufacturing requirements of some electronic devices.

5 Application and Research Progress of Cellulose Film 5.1 Traditional Application The application of cellulose transparent film has a long history, and the traditional application direction is mostly in packaging and printing. It has the characteristics of good mechanical properties, stable structure, strong thermal stability, and superior optical properties. It is widely used in convex and concave pressing, manual drawing, laser printing, etc. The transparent paper used in the tobacco packaging system is mostly made from reforested trees. These trees have been crushed and contain no chemicals. Because the natural transparent paper can make the product completely visible, and ensure its taste and smell, and then Coupled with the porosity and natural characteristics of the paper, the tobacco can be kept in an environment free from humidity and overheating [17]. In addition, RCF is mostly used in the packaging of food, cosmetics and other products. The demand for transparent paper for this purpose is huge, and the output is increasing year by year. In recent years, some researchers have improved the traditionally used transparent paper. Fang et al. obtained a uniform coating solution by mixing fluorocarbon, modified

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starch and sodium alginate, and then coated it on the surface of transparent paper. As the coating weight increased, the surface of the paper became smoother and more uniform; The grease barrier performance of coated paper is significantly better than that of base paper; the contact angle of base paper decreases from 29.41° to 23.46° within 20 min, while the contact angle of coated paper increases significantly, reaching a stable state within 2 min, with the maximum contact The rate of angular change is only 0.06°/min [18]. 5.2 Novel Applications Cellulose based materials have the advantages of degradability, low cost, adjustable optical and mechanical properties. In recent years, there are more and more researches on their applications in electronic devices such as solar cells, light-emitting diodes. For example, Shen Chen prepared superhydrophobic Nanopaper with tempo oxidized CNFs and polysiloxane, and improved the water repellency (static contact angle of 70.7%) and toughness (118.7%) of Nanopaper through further silylation. However, the raw materials of Nanopaper consume a lot of energy, and the preparation method of vacuum filtration is also an obstacle to its large-scale production. The results show that transparent paper-based materials have broad application prospects as flexible, transparent and environmentally friendly luminescent displays, lighting paper and biosensors [19].

6 Conclusion In recent years, with the efforts of many scientific research workers, there are many preparation methods and application ways of cellulose transparent membrane, but each has its own advantages and disadvantages. How to make good use of the advantages of cellulose transparent membrane, such as renewable, low cost, to develop large-scale industrialized preparation methods and find high-value application ways still need efforts. Acknowledgement. This work has been financially supported by the Natural Science Foundation of China (Grant No. 61973127), Guangdong Provincial Science and Technology Program (Grant No. 2017B090901064), and Chaozhou Science and Technology Program (Grant No. 2020ZX14).

References 1. Fang, Z., Zhu, H., Bao, W., et al.: Highly transparent paper with tunable haze for green electronics. Energy Environ. Sci. 7(10), 3313–3319 (2014) 2. Nogi, M., Karakawa, M., Komoda, N., et al.: Transparent conductive nanofiber paper for foldable solar cells. Sci. Rep. 5, 17254 (2015) 3. Hu, L., Zheng, G., Yao, J., et al.: Transparent and conductive paper from nanocellulose fibers. Energy Environ. 6(2), 513–518 (2013) 4. Koga, H., Nogi, M., Komoda, N., et al.: Uniformly connected conductive networks on cellulose nanofiber paper for transparent paper electronics. NPG Asia Mater. 6(3), 93 (2014) 5. Ummartyotin, S., Juntaro, J., Sain, M., et al.: Development of transparent bacterial cellulose nanocomposite film as substrate for flexible organic light emitting diode (OLED) display. Ind. Crops Prod. 35(1), 92–97 (2012)

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6. Kang, X., Sun, P., Kuga, S., et al.: Thin cellulose nanofiber from corncob cellulose and its performance in transparent nanopaper. ACS Sustain. Chem. Eng. 5(3), 2529–2534 (2017) 7. Laroque, C.: History and analysis of transparent papers. Paper Conserv. 28(1), 17–32 (2004) 8. Brown, W.F.: Vulcanized fibre-an old material with a new relevancy. In: Proceedings of the Electrical Insulation Conference & Electrical Manufacturing & Coil Winding Conference, F (1999) 9. Hu, W., Chen, G., Liu, Y., et al.: Transparent and hazy all-cellulose composite films with superior mechanical properties. ACS Sustain. Chem. Eng. 6(5), 1–21 (2018) 10. Nishino, T., Arimoto, N.: All-cellulose composite prepared by selective dissolving of fiber surface. Biomacromol 8(9), 2712–2716 (2007) 11. Lu, P., Cheng, F., Ou, Y., et al.: Rapid fabrication of transparent film directly from wood fibers with microwave-assisted ionic liquids technology. Carbohyd. Polym. 174(03), 330–336 (2017) 12. Yousefi, H., Nishino, T., Faezipour, M., Ebrahimi, G., Shakeri, A.: Direct fabrication of allcellulose nanocomposite from cellulose microfibers using ionic liquid-based nanowelding. Biomacromol 12(11), 4080–4085 (2011). https://doi.org/10.1021/bm201147a 13. Laroque, C.: Transparent papers: a technological outline and conservation revIew. Stud. Conserv. 45(1), 21–31 (2000) 14. Hyden, W.L.: Manufacture and properties of regenerated cellulose films. Ind. Eng. Chem. 21(5), 405–410 (1929) 15. Fink, H.P., Weigel, P., Purz, H.J., et al.: Structure formation of regenerated cellulose materials from NMMO-Solutions. Prog. Polym. Sci. 26(9), 1473–1524 (2001) 16. Sun, X., Wu, Q., Ren, S., Lei, T.: Comparison of highly transparent all-cellulose nanopaper prepared using sulfuric acid and TEMPO-mediated oxidation methods. Cellulose 22(2), 1123– 1133 (2015). https://doi.org/10.1007/s10570-015-0574-6 17. Neto, H.M.D.C.: Transparent Paper, for Tobacco-Packaging System, US20090229620 [P/OL] (2009) 18. Jiang, X., Chen, G., Fang, Z.Q.: The application of starch - sodium alginate composite coating on transparent paper for food packaging. Adv. Mater. Res. 893(4), 472–477 (2014) 19. Chen, S., Song, Y., Xu, F.: Highly transparent and hazy cellulose nanopaper simultaneously with a self-cleaning superhydrophobic surface. ACS Sustain. Chem. Eng. 6(4), 5173–5181 (2018)

Biocomposites Based on Spent Coffee Grounds and Application in Packaging: Review Yiyu Chen1 , Qiongyang Li1 , Cheng Feng1 , Yuwei Hu2 , Yutao Liu2(B) , and Junfei Tian1(B) 1 State Key Laboratory of Pulp and Paper Engineering, South China University of Technology,

Guangzhou, China [email protected] 2 Key Laboratory of South China Modern Biological Seed Industry, Ministry of Agriculture and Rural Areas, National S and T Innovation Center for Modern Agricultural Industry, Guangzhou, China [email protected]

Abstract. Spent coffee grounds (SCG) are agricultural residues of the coffee industry and rich in multiple organic compounds, showing a promising prospect for valorization. Notably abundant in polysaccharides like cellulose, SCG are important source for biomass-based fiber, which have been extensively explored to fabricate biocomposite with matrix such as polyethylene and polylactic acid. Though incorporating SCG particles into matrix is a facile and cost-effective approach to obtain highly sustainable and value-added material, proper pretreatments on those particles are usually demanded for desirable changes such as better compatibility and degradability. Herein, several commonly used methods were reviewed in terms of removing unwanted substances by oil extraction and alkaline treatment, and chemical modification by acetylation, maleated coupling and silane treatment, of which the influences on the properties of the biocomposite were discussed. Furthermore, we summarized the matrices mostly used to compound with SCG, which ranged from those petroleum-based to the favorable bio-based ones. Finally, the future direction of the biocomposite with SCG in the field of packaging was proposed. Keywords: Spent coffee grounds · Biocomposite · Pretreatment. Matrix · Packaging

1 Introduction Coffee, a worldwide popular beverage, contributes to an enormous market [1], however leaving behind millions of tons residue—spent coffee grounds (SCG). According to the ICO (International Coffee Organization), over 9 million tons of coffee are consumed worldwide each year [2], followed by a yield of 650 kg SCG per ton of coffee beans used. Often those brown waste just return as compost, fertilizer and landfill, which not only is a huge loss for this valuable resource, also may induce hazard into the soil along © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 455–461, 2022. https://doi.org/10.1007/978-981-19-1673-1_68

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with the plants in it. Therefore, many efforts have been made to valorizing them, such as developing value-added products [3], designing a sustainable life circle [4] and so on. Produced in the brewing process of coffee beans [5], SCG commonly contain proteins, non-protein nitrogenous compounds, minerals, nitrogen-containing tan compounds, brown-colored compounds, caffeine, lipids, phenolic compounds and carbohydrates [6]. Among them, carbohydrates, the most significant component in SCG, is composed of polysaccharides--mostly fiber, which accounts for about 45% of the total dry mass of SCG, making it an important source of biofiber. Degradable materials have always been the focus of the packaging industry for less negative impact on both the ecosystem and human society after being abandoned. Naturally biodegradable bioplastics such as PLA [7], PBAT [8], PHA [9], etc., have attracted much attention in the field of packaging material, as well as optimizing traditional petroleum-based plastics by compounding cellulose-based biomass to effectively improve their physical and chemical properties. Abundant in fiber, SCG emerges as attractive raw material for high-quality bio-fiberbased composite after removal of some substances like lipids and phenolic compounds, which may hinder the cross-linking and fusion between the fiber and the matrix, impair the structure and lead to poor performance of the composite. By investigating the pretreatments in the existing literature, this paper summarized their mechanism and effect on SCG, as well as the interaction between the pretreated SCG and different matrices, further proposing the outlook of SCG-based biocomposite packaging materials.

2 Pretreatments on SCG As mentioned above, the raw SCG contain multiple substances, much of which may block the coalesce of biocomposite forming. Therefore, those untreated SCG, usually brown particles, demand certain pretreatments to remove those unwanted substances to obtain desirable morphology, so that its compatibility with matrices could be improved. Herein, several mostly used methods including oil extraction, alkaline treatment, acetylation, maleated coupling, silane treatment were presented. SCG contain rich and diverse lipids, some of which are found beneficial to human health. Therefore, SCG is often refined for coffee oil, leaving the oil-extracted SCG to further utilization. The removal of the fat can cause a great change in SCG composition, surface morphology and some properties of the obtained particle, influencing the functionality of the biocomposite when it is made into packaging material. Wu et al. removed the coffee oil from SCG with n-hexane by ultrasonication, finding that the size of the SCG particle after extraction (ESCG) decreased, along with a rougher surface as well as a more porous structure as shown in Fig. 1(a) and (b) [10]. They believed that the removal of oils enabled the particles disperse in the matrix more uniformly and restrain with the polymer chain more tightly, contributing to a crack-less surface on the composite as well as better compatibility. As shown in Fig. 1(c) and (d), the surface fine cracks of the formed composite material are reduced, the uniformity is improved, and the bending resistance and tensile resistance are further improved.

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Fig. 1. Surfaces of SCG particles (a) and ESCG particles (b) and the fractured surfaces of ESCGPC (c) and SCGPC (d) [10].

Alkaline treatment, also mercerization, is one of the most applied chemical methods to removes a certain amount of lignin, oils and wax over the fiber reinforcing thermoplastics and thermosets [11]. This chemical treatment by alkaline disrupts the hydrogen bonding of the network structure, increasing the surface roughness, thereby exposing more celluloses for reaction sites in the coupling. In this process, the SCG are immersed in the strong alkaline like NaOH, to get swelling up for changes in structure, morphology and mechanical properties. The content changes of each composition of SCG after alkaline treatment are shown in Table 1. Table 1. Composition of SCG and D-SCG Samples Density (kg m−3 ) Cellulose (%) Hemicellulose (%) Lignin (%) Porosity (%) SCG

562 ± 5

18.2 ± 0.8

51.5 ± 0.5

30.3 ± 1.5

64.2 ± 0.31

D-SCG

287 ± 7

41.8 ± 0.5

53.6 ± 0.7

4.8 ± 0.5

81.7 ± 0.29

D-SCG = Delignified SCG

Manalo et al. found that the bamboo fiber was treated with 6 wt% NaOH solution, further compounded with polyester to fabricate the biocomposite, which was compared with those without alkali treatment in terms of bending strength, tensile strength, compressive strength and hardness, 7%, 10%, 81% and 25% higher respectively [12]. Compared with SCG without alkali treatment, the SCG composite material after alkali treatment has better tensile strength, thermal stability, crystallinity and water resistance. Other chemical pretreatments like silane treatment, acetylation, melated coupling are often seen in the modification of natural fibers. Silane treatment is to use a coupling agent with multifunctional groups to modify the surface of the fiber. By generating a siloxane containing Si-O-Si bonds, that is, a chemical connection is established between the fiber surface and the matrix to achieve compatibility between the two. The silane coupling agent is a composite hydrocarbon chain, which can inhibit the fiber from swelling into the matrix, thereby enhancing the cross-linking of the two and improving the performance

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stability of the material. Essabir et al. bleached SCG with 8 wt% NaOH and H2 O2 , and then used tetraethyl orthosilicate (TEOS) to silanize them [13]. They found that the compatibility of the two is improved, which makes its tensile strength of SCG increased by 6% compared to the untreated SCG. Acetylation is a chemical surface modification method that uses the acetyl group (-CH3 CO) to react with the hydroxyl group (-OH) on the fiber, that is, to cover the hydrophilic hydroxyl group, thereby reducing the hydrophilicity of the fiber. Working in the same way, maleic anhydride also is a coupling agent commonly used for surface modification of fiber and matrix to improve the compatibility of the two. 2.1 Matrices for SCG Biocomposites In 2019, the global production of plastics has exceeded 368 million tons, of which approximately 39.6% were processed into packing products that mostly ended up as waste (up to 97%), causing series of urgent environmental issues. To mitigate them, multiple approaches have been raised: sustainable packaging solutions, replacing non-degradable plastics with degradable materials like paper, endowing plastic with more degradability and so on. Among them, filling plastic matrix with biomass particles has attracted much attention for the prominent cost efficiency as well as the improved mechanical property, thermal stability, biodegradability, and processability for packaging. A remarkable effort has been made to well incorporate SCG into the matrices ranging from those derived from petroleum to naturally degradable ones that are refined from plants. Non-degradable polyethylene (PE) and polypropylene (PP), cheap and excellent in mechanical strength, hydrophobicity, moisture resistance [14], are the mostly used petroleum-based matrices. Though it has been widely proved that SCG enhance the rigidity and thermal stability of the matrix, the challenge remains that SCG impair the mechanical property of the obtained biocomposite. To maintain the mechanical property as much as possible, Arrigo, R. et al. [15] burned the SCG into the biochar (BC) with enriched porous structure and functional groups, which helped the particles better interact with the matrix of high-density polyethylene (HDPE). They believed that the molecular chain restraint on the particle surface and within the empty channels, improved the rheological property and thermal stability of the polymer. Other studies instead focused on mitigating the incompatibility between the hydrophilic SCG and hydrophobic matrices, thus optimizing the mechanical property of the biocomposite [16]. Meanwhile, degradable petroleum-based plastics like poly (butylene adipate-coterephthalate) (PBAT) gain more and more attention from the public and researchers for their natural degradability. Filling the matrices with SCG can not only cut down the cost significantly, also help strengthen some properties like thermal stability, and even accelerate the degradation. Moustafa, H. et al. fabricated a biocomposite based on SCG and PBAT and further studied how the addition of polyethylene glycol (PEG) affected the composites [17]. They found that the tensile strength of SCG/PBAT composites was notably improved with 10 wt% PEG added, making it more processable during package manufacture. Though a noteworthy improvement on petroleum-based plastics has been made, more aggressive actions need to be in place to address the problems like “white pollution”.

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Many suggested replacing the petroleum-based plastics in the packaging industry with those derived from biomass such as PLA, polybutylene succinate (PBS), and PHA, starch and pectin. Plenty of effort has been in the way including SCG, which may be transformed into PHA and enhance other biomass-based matrices as filler. The obtained composites present better mechanical property, thermal stability and degradability, gaining a broad prospect in the field of packaging. Ana Paula da Silva et al. developed a biocomposite with PLA and SCG, and found that compared with pure PLA, the hydrophilicity and degradability of the biocomposite was enhanced after adding SCG. Starch, a high-molecular carbohydrate, is also used to be degradable packaging materials [18]. Elisa and his team casted a film with SCG, starch and glycerin, where SCG was used as an intensifier to improve the tensile strength of the film [19]. SCG can be added to PLA to improve its degradability, but its relatively weak compatibility between them has also restricted the development of PLA/SCG composites. Chin-San Wu treated the SCG with crosslinking agent TEOS and grafted the PLA matrix with maleic anhydride [20]. They found that the cross-linked SCG homogeneously dispersed in the grafted polymer, contributing to the greater compatibility and thus the more desirable mechanical properties.

3 Conclusion and Outlook As concern on sustainability intensively increases, processing of biomass gains more and more weight, inspiring innovative and cost-effective approaches to valorize those mass residues like SCG. The abundant content of natural fiber makes SCG favorable raw material to enhance polymer properties as fillers. To obtain desirable properties, some unwanted components always need to be removed first by pretreatments like oil extraction and alkaline treatment, which help SCG disperse uniformly in the matrix, thus mitigating the loss in mechanical properties such as tensile strength. Other common chemical ways to boost the compatibility between SCG and matrix are acetylation, maleated coupling and silane treatment, which make the biocomposite more processable in the packaging manufacture. Matrices derived from petroleum ranging from the non-degradable like PP and PE, to the degradable ones like PBAT, have been widely explored to fabricate biocomposite with SCG for their low cost. But when it comes to degradability, bio-based materials such as PLA and starch are more convincing choices for the public, though faced with a much higher price and deficits in mechanism, which SCG have been proved to have a positive impact on while bringing down the cost significantly. However remarkable the progress has been made in terms of SCG based composite, the loss of mechanical property after adding SCG still limits its application in packaging. For one thing, optimizing the pretreatment to be more cost-effective and less compromising in properties in industrial production is important. For another thing, persistent attempt should be encouraged to compounding SCG with other biomass-based materials to explore new composite.

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References 1. Ballesteros, L.F., Cerqueira, M.A., Teixeira, J.A., Mussatto, S.I.: Production and physicochemical properties of carboxymethyl cellulose films enriched with spent coffee grounds polysaccharides. Int. J. Biol. Macromol. 106, 647–655 (2018) 2. ICO: Coffee Trade Stats. International Coffee Organization, UK (2020). http://www.ico.org/ prices/new-consumption-table.pdf 3. Arulrajah, A., Maghoolpilehrood, F., Disfani, M.M., Horpihulsuk, S.: Spent coffee grounds as a non-structural embankment fill material: engineering and environmental considerations. J. Clean. Prod. 72, 181–186 (2014) 4. Rivera, X.C.S., Gallego-Schmid, A., Najdanovic-Visak, V., Azapagic, A.: Life cycle environmental sustainability of valorisation routes for spent coffee grounds: From waste to resources. Resour. Conser. Recycl. 157 (2020) 5. Cruz, R., et al.: Espresso coffee residues: a valuable source of unextracted compounds. J. Agric. Food Chem. 60(32), 7777–7784 (2012) 6. Campos-Vega, R., Loarca-Pina, G., Vergara-Castaneda, H.A., Oomah, B.D.: Spent coffee grounds: a review on current research and future prospects. Trends Food Sci. Technol. 45(1), 24–36 (2015) 7. Lukic, I., Vulic, J., Ivanovic, J.: Antioxidant activity of PLA/PCL films loaded with thymol and/or carvacrol using scCO2 for active food packaging. Food Packag. Shelf Life 26, 100578 (2020). https://doi.org/10.1016/j.fpsl.2020.100578 8. Moustafa, H., El Kissi, N., Abou-Kandil, A.I., Abdel-Aziz, M.S., Dufresne, A.: PLA/PBAT bionanocomposites with antimicrobial natural rosin for green packaging. ACS Appl. Mater. Interf. 9(23), 20132–20141 (2017) 9. Fabra, M.J., Lopez-Rubio, A., Ambrosio-Martin, J., Lagaron, J.M.: Improving the barrier properties of thermoplastic corn starch-based films containing bacterial cellulose nanowhiskers by means of PHA electrospun coatings of interest in food packaging. Food Hydrocoll. 61, 261–268 (2016) 10. Wu, H.J., et al.: Effect of oil extraction on properties of spent coffee ground-plastic composites. J. Mater. Sci. 51(22), 10205–10214 (2016) 11. Faruk, O., Bledzki, A.K., Fink, H.-P., Sain, M.: Biocomposites reinforced with natural fibers: 2000–2010. Prog. Polym. Sci. 37(11), 1552–1596 (2012) 12. Manalo, A.C., Wani, E., Zukarnain, N.A., Karunasena, W., Lau, K.T.: Effects of alkali treatment and elevated temperature on the mechanical properties of bamboo fibre-polyester composites. Comp. Part B-Eng. 80, 73–83 (2015) 13. Essabir, H., Raji, M., Laaziz, S.A., Rodrique, D., Bouhfid, R., Qaiss, A.E.: Thermomechanical performances of polypropylene biocomposites based on untreated, treated and compatibilized spent coffee grounds. Comp. Part B-Eng. 149, 1–11 (2018) 14. Tankhiwale, R., Bajpai, S.K.: Preparation, characterization and antibacterial applications of ZnO-nanoparticles coated polyethylene films for food packaging. Coll. Surf B Bioint. 90, 16–20 (2012) 15. Arrigo, R., Jagdale, P., Bartoli, M., Tagliaferro, A., Malucelli, G.: Structure-property relationships in polyethylene-based composites filled with biochar derived from waste coffee grounds. Polymers (Basel) 11(8) (2019) 16. Mendes, J.F., et al.: Thermo-physical and mechanical characteristics of composites based on high-density polyethylene (HDPE) e spent coffee grounds (SCG). J. Polym. Environ. 29(9), 2888–2900 (2021). https://doi.org/10.1007/s10924-021-02090-w 17. Moustafa, H., Guizani, C., Dufresne, A.: Sustainable biodegradable coffee grounds filler and its effect on the hydrophobicity, mechanical and thermal properties of biodegradable PBAT composites. J. Appl. Poly. Sci. 134, 8 (2017). https://doi.org/10.1002/app.44498

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18. Oates, C.G.: Towards an understanding of starch granule structure and hydrolysis. Trends Food Sci. Tech. 8(11), 375–382 (1997) 19. Gazonato, E.C., Maia, A.A.D., Moris, V.A.d.S., Paiva, J.M.F.d.: Thermomechanical properties of corn starch based film reinforced with coffee ground waste as renewable resource. Mater. Res. 22(2) (2019) 20. Wu, C.-S.: Renewable resource-based green composites of surface-treated spent coffee grounds and polylactide: characterisation and biodegradability. Polym. Degrad. Stab. 121, 51–59 (2015)

Preparation of Polymer Latex Containing Infrared Dye and Its Application to the Preparation of Computer to Plate Precursors Li An, Hongli Zhang, Kunbi Qin, Chunxing Ren, and Zhongxiao Li(B) Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. This work relates to preparation of a lithographic coating which can be made a environment friendly printing plate with computer to plate (CTP) technology. The lithographic coating was consisted of polymer latex containing 830 nm oil-soluble infrared dye (IR) and carboxyl group, amine oxide-substituted polymer resin and other auxiliaries. The characteristics of the polymer resin, polymer latex, coating solution and CTP precursor were evaluated by many methods. The negative image could be obtained through image-wise exposure and water developing. The presence of hydrogen bonding interaction between the emulsion polymer containing carboxyl group and the amine oxide substituted hydrophilic binder in the CTP precursor was found to have a significant effect on imaging quality. Keywords: Computer to plate precursor · Laser-imageable · Infrared dye

1 Introduction In recent years, as the requirements of energy saving and emission reduction, printing industry is upgrading for consumables. Printing plate is one of the important consumables and usually used alkaline solution for development, thus, many problems such as chemical reagent emissions is existed. Therefore, chemical free CTP technology emerged based on the consideration of environmental protection [1, 2]. As lower toxicity compared to solvent-based products, water-based systems are paid enough attention in the field of coating. The chemical free CTP technology is also using water-based materials as precursor. In recent years, the chemical free CTP technology has been attracted more and more attention by many developed countries, and the famous companies have launched corresponding products on the printing exhibition. For example, Azura thermal plate from AGFA company in Germany, Therma Direct thermal plate from Kodak company in the United States and Brillia HD PRO-T thermal plate from Fuji company in Japan. However, some products are not fully developed by water, and chemical reagents are used more or less. The working principles based on fusible micro colloidal particles launched by Agfa company, the image generation is completely

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 462–470, 2022. https://doi.org/10.1007/978-981-19-1673-1_69

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a physical process, and water development can be realized, the mechanism of chemical free CTP technology is that the thermoplastic polymer particles can be fused by 830 nm laser exposure (Fig. 1). The main components include 830 nm oil soluble IR dye and resin. The hydrophobic dye can be encapsulated by miniemulsion polymerization method [3–5]. Thus, the water-based precursor, which made from 830nm oil soluble IR dye, will come true. However, there are also shortcomings that the final image will be fall off from the aluminum plate, due to the poor adhesion between the precursor and plate surface. In coatings and adhesives areas, the crosslinking principle is often used to improve the performance of thermal and mechanical property. Crosslinking based on non-covalent bonds, such as hydrogen bonding or ionic crosslinking can also give the material enhanced properties. In this paper, a crosslinking strategy is used to construct a CTP precursor. The 830 nm oil soluble IR dye was encapsulated by miniemulsion polymerization containing carboxyl group. The polymer resin designed containing amine oxide group as binder. The hydrogen bonds can be formed by this polymer nanoparticles with amine oxide resin, and make the CTP image more durable.

Fig. 1. Imaging process for the chemical-free CTP plate

2 Experimental 2.1 Materials and Methods Styrene and acrylonitrile which were purchased from Shanghai Aladdin Biochemical Technology Co., were refined by vacuum distillation before use. The other reagents Mono-2-(methacryloyloxy)ethyl phthalate (MMAEP), 2-(dimethylamino) ethyl acrylate, sodium persulfate (APS), hydrogen peroxide(30 wt%), L-ascorbic acid and tertbutyl hydroperoxide (TBH, 30wt%) were supported by J&k Chemical Co. and used without purification. The IR dye (Fig. 2) with the maximum absorption near 830 nm (IR830 ) were purchased from Shanghai Wujing Chemical Technology Co., Ltd. and used as received. 2-(((Dodecylthio)carbonothioyl)thio)-2-propanoic acid (DCTPA) was prepared in our lab. Distilled deionized water (DDW) and organic solvents are conventional reagents and used as received.

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Fig. 2. Molecular structure of the 830 nm IR dye (IR830 )

2.2 Synthesis of Macromolecule Resin Containing Amine Oxide(O-PDMAEA) First, 0.15 g of APS was dissolved in 5 mL of DDW. Then, 20 g of 2-(dimethylamino) ethyl acrylate, 0.15 g of DCTPA and 20 g of deionized water were added into a threenecked round-bottom flask. The purpose of adding a little DCTPA is to control the polymerization rate. The mixture was stirred to obtain a clear solution. Then, the APS aqueous solution was added under stirring at ambient temperature. Obvious exothermic phenomenon appeared and the viscosity of the solution increased gradually. The reaction mixture was stirred for 10 h to yield a yellowish viscous solution. The product obtained by this polymerization is noted as PDMAEA. FTIR (KBr, cm−1 ): 3300-3500, 2960, 2865, 2360, 1726, 1575, 1472, 1397, 1286, 1170, 1082, 1070, 990, 928. 0.5 g of dimethyl carbonate was added and the temperature was raised to 70 °C. 10 g of hydrogen peroxide aqueous solution (30 wt%) was added dropwise with 2h. Then, the temperature was raised to 75 °C and kept for another 3 h, providing an almost colorless viscose solution. The polymer solution was slowly poured into an excess of ethanol to afford a white solid. The solid was collected and washed repeatedly with ethanol. The white solid was dried in vacuo at 80 °C for 8 h. The final product, oxidized PDMAEA, is noted as O-PDMAEA. The yield was 18.84 g (84.2%). FTIR (KBr, cm−1 ): 3300-3500, 2960, 2865, 2360, 1726, 1575, 1472, 1397, 1286, 1070, 960. 2.3 Preparation of Polymer Latex Containing IR830 and MMAEP Sodium dodecyl sulfate (1.35 g), L-ascorbic acid (0.52 g) and DDW (160 ml) were mixed to make the aqueous phase. The oil phase was made from styrene (21.33 g), acrylonitrile (10.75 g), hexadecanol (0.33 g), MMAEP (8 g) and IR830 (1.35 g). Then, the aqueous phase and oil phase were mixed by a high-pressure homogenizer for 10 min. The obtained miniemulsion was placed in a four-necked flask, and mechanically stirred for half an hour at 25 °C. The TBH (0.4 g) in water (40 ml) was added into the emulsion by peristaltic pump to start the polymerization. The polymerization lasted for 8 h under nitrogen environment. Finally, the latex with polymer particles encapsulating IR830 was filtered with a Buchner funnel. The filtrate was collected and kept for later use. For the need of comparison, the latex without adding MMAEP was also prepared. Styrene (26.67 g) and acrylonitrile (13.33 g) were used as monomer. Other recipes are the same as above mentioned.

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2.4 Preparation of the Heat-Sensitive Negative-Working Lithographic CTP Precursor and Laser Exposure The CTP precursor was produced by first applying a coating solution onto the aluminum substrate (special for CTP plate). The main compositions of the coating solutions were 10 g polymer latex, 0.25 g amine oxide resin. Little auxiliaries such as leveling agent were also added in the coating solutions to make the final film smoother and more uniform. The precursor was applied from an aqueous coating solution (solid content of about 15 wt%) and dried at 80 °C. A dry precursor weight of 1.2 ± 0.05 g/m2 on the plate was obtained. Then the sample was mounted on the exposure device for 830 nm IR laser scanning to form a latent image. The device is an infrared laser diode with 2 w output power which was made by Changchun New Industry Photoelectric Technology Co., Ltd. The laser wavelength is 830 nm and its pulse width is 10 ns. Finally, the exposed film was developed with deionized water to get the final stable image. 2.5 Measurements The structure of hydrophilic binder was measured by a Shimadzu FTIR-8400 infrared spectrometer. The wavenumber was range from 600 to 4000 cm−1 . 1 H NMR spectra of the amine oxide substituted hydrophilic binder was recorded on a Bruker AV400 MHz NMR spectrometer. D2 O was used as solvent. The UV-2501PC spectrophotometer was used to measure the encapsulated IR830 at room temperature. The number average particle size of the diluted emulsion was done by a Malvern ZETASIZER Nano (DLS) at 25 °C. Kruss Optical contact angle was used to test the surface water contact angles. The surface topography of the image-recording layer was detected by Hitachi SEM SU8020.

3 Results and Discussion 3.1 Synthesis of the Resin Containing the Tertiary Amine Oxide Group As shown in Fig. 3, the tertiary amine oxide resin was synthesized via two steps reaction. The first step is the polymerization of 2-(dimethylamino) ethyl acrylate as monomer, DCTPA as a molecular weight regulator and sodium persulfate (APS) as initiator. The second step is the process of oxidation by hydrogen peroxide aqueous solution (30 wt%). 1 H NMR spectra of the final tertiary amine oxide resin was shown in Fig. 4. The signal at 3.34 ppm is attributed to the methyl group on the tertiary amine oxide group. Meanwhile, the multiple peaks at 3.62 and 4.05 are ascribed to the two ethyl linked to nitrogen. This indicated that poly(2-(dimethylamino) ethyl acrylate) was successfully oxidized to the corresponding product.

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DTCTP

N

N

O

H2O; K2S2O7

n O

O

H 2O 2 O

(CH3O)2CO

(PDMAEA)

N

n (O-PDMAEA)

Fig. 3. Synthetic route of the water-soluble polymer as hydrophilic binder containing amine oxide group

Fig. 4. 1 H NMR spectra of the tertiary amine oxide resin

3.2 Preparation of Polymer Latex Containing IR830 Dye and Carboxyl Group Figure 5 shows the mechanism of this polymerization. The polymer latex had a solid content of about 20 wt % were obtained. The polymer nanoparticles encapsulated IR830 and carboxyl group shows a maximum wavelength of UV-vis absorption spectrum around 830 nm in Fig. 6. This means that the IR830 was encapsulated steadily in the polymer nanoparticles and the MMAEP monomer did not affect the structure of the IR dye. 3.3 Preparation and Characterization of the Coating Solution In this study, synthesis of the polymer latex containing IR830 dye and carboxyl group is the key to the preparation of the coating solution for the chemical-free CTP precursor, and the polymer particles should be stable and uniform when applied to imaging materials. Figure 7 exhibits the DLS results for the emulsion and the coating solution, respectively. It directly indicates that the size of the polymer particles is around 40 nm with nearly monodispersity. However, the particle size of the coating solution increased to above 80 nm sharply and their polydispersition index (PDI) also widened from 0.1 to 0.5. This

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Fig. 5. Synthetic route of the polymer latex containing oil soluble IR830 derived from styrene, acrylonitrile and MMAEP 1.5

830nm

polymer latex containing IR830 and carboxyl group

Abs

1.0

0.5

600

700

800

900

Wavelength(nm)

Fig. 6. Absorption spectra of polymer latex containing IR830 dye and carboxyl group

is due to that the coating solution consists of the emulsion copolymer particles having the MMAEP moiety and the hydrophilic binder with amine oxide group. A small part of carboxyl group of the emulsion copolymer at the surface of the polymer particles might form intermolecular hydrogen bonds (–O-H…O-N–) with the amine oxide polymer binder. As a result, it was found that average particle size and PDI value increased with the preparation of the coating solution.

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Polymer latex Coating solution

Number(%)

25

20

15

10

5

0 10

100

Particle Size (nm)

Fig. 7. DLS analysis of the polymer latex and the coating solution

3.4 Properties of CTP Precursor and Imagewise Exposure The CTP precursor was produced by applying a coating solution onto the aluminum substrate (special for CTP plate). The main compositions of the coating solution were polymer latex containing 830 nm oil-soluble IR dye and carboxyl group, hydrophilic binder containing tertiary amine oxide group and other auxiliaries. The original precursor surface is hydrophilic and can be easily developed by neutral water. Upon image-wise laser exposure, the surface properties change a lot. Figure 8 shows contact angle with water drop on the both non-imaged and imaged area. The contact angle of the water drop on the non-imaged area was 30°, and then it increased to 65°, when the CTP precursor surface was exposed. This indicated that the microstructure of laser exposure area changed significantly. The surface morphology of the exposed and non-exposed areas of the image-recording layer, which was recorded by SEM in Fig. 9, can prove it. The polymer particles in the non-exposed area were still clearly visible. After exposure, separate polymer particles could not be observed due to heat-induced fuse and coagulation of them.

Fig. 8. Contact angle with water drop on non-imaged area (a) and imaged area (b).

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Fig. 9. SEM photographs of non-exposed area and exposed area.

In order to compare the imaging quality of precursors in the presence of hydrogen bonds, the latex without MMAEP was also added as polymer particles in coating solution to prepare the precursor. As seen in Fig. 10, the final image of the CTP precursors after exposure by 830 nm infrared laser and development by neutral water at 25 °C. The image of line is very clear and has a good quality in Fig. 10(a). Conversely, the Fig. 10(b) which made from the latex without MMAEP was removed after developing with water and its clean-out performance was relatively poor. As there was no carboxyl group in precursor (Fig. 10(b)), no hydrogen bongding existed in this sample, before or after infrared laser exposure. However, hydrogen bongding should be present in the sample of Fig. 10(a), especially after laser exposure. A comparison of Fig. 10(a) and Fig. 10(b) indicates that intermolecular hydrogen bonding interactions played an important role in improving the performance of the image-recording layers.

Fig. 10. Image of line (a) using the latex containing MMAEP and (b) using the latex without MMAEP after 830 nm infrared laser exposure with water development at 25 °C

4 Conclusions A new chemical-free CTP precursor was made from polymer latex containing 830 nm oil soluble IR dye and carboxyl group, amine oxide resin and other auxiliaries. It can be obtained negative image through image-wise exposure by 830 nm IR laser radiation followed with water developing. DLS revealed that polymer containing carboxylic acid in the latex can be formed intermolecular –OH…N– hydrogen bond with amine

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oxide substituted hydrophilic binder. With the intermolecular –OH…N– hydrogen bonds crosslinking together, the final developed clear images on the aluminum plate substrate can be easily obtained. Acknowledgements. This research was supported by National Natural Science Foundation of China (No. 21905028), Scientific Research Project of Beijing Educational Committee (KM202110015009), Beijing Municipal Natural Science Foundation (No. 2192017) and Cross Training Program of High Level Talents in Beijing Universities (22150121003/062).

References 1. Liang, Z., Zhu, J., Li, F., et al.: Synthesis and properties of self-crosslinking waterborne polyurethane with side chain for water-based varnish. Prog. Org. Coat. 150, 105972 (2021) 2. Sorce, F.S., Shields, T., Ngo, S., et al.: The effect of varying molecular weight on the performance of HMMM-crosslinked polyester coatings. Prog. Org. Coat. 149, 105920 (2020) 3. Abdou, L.A.W., El-Molla, M.M., Hakeim, O.A., et al.: Synthesis of nanoscale binders through mini emulsion polymerization for textile pigment applications. Ind. Eng. Chem. Res. 52(6), 2195–2200 (2013) 4. Weiss, C.K., Landfester, K.: Miniemulsion polymerization as a means to encapsulate organic and inorganic materials. In: van Herk, A.M., Landfester, K. (eds.) Hybrid Latex Particles, pp. 185–236. Springer, Heidelberg (2010). https://doi.org/10.1007/12_2010_61 5. An, L., Cai, Z., Wang, W., et al.: A thermo-sensitive imaging coating derived from polymer nanoparticles containing infrared absorbing dye. Eur. Polym. J. 52, 166–171 (2014)

Development of Solution-Processed Organic Semiconductor Thin Films Wenjuan He, Suyun Wang, Beiqing Hang, Xianfu Wei, and Lijuan Liang(B) School of Printing and Packaging Engineer, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. In recent years, organic thin film transistors have gradually occupied most of the market, and they have played a huge role in the fields of flexible wearable electronics, flexible biosensors, organic light-emitting diodes, and nonvolatile memories. Organic semiconductor layers act as a major component of thin-film transistors, which can be printed by roll-to-roll at room temperature for large-area preparation on flexible substrates. However, in the process of preparing thin films by solution method, it is necessary to pay attention to how to control the surface morphology of organic semiconductor thin films and the nucleation and growth of crystals. Owing to the morphology of the film and the growth of crystals determine the performance of organic thin film transistors. Therefore, in this small review, we will concentrate on the preparation of organic semiconductor thin films by solution-processed in recent studies by each team, and briefly evaluate the advantages and disadvantages of the preparation method, as well as the prospects for the future research process of organic semiconductor layers. It can be anticipated that our understanding of these method will lay an important foundation for the future preparation of low-cost, high-performance flexible printed electronic devices. Keywords: Solution process · Organic thin film transistor · Organic semiconductor · Mobility

1 Introduction Organic electronic devices, with their advantages of low cost, simple preparation, easy integration and flexibility, are widely used in the preparation of biological flexible display [1], sensors [2], logic circuits [3], wearable electronics [4], non-volatile memory and other fields. Therefore, in decades of continuous research, people gradually have a more in-depth understanding of organic thin film transistors (OTFTs). At present, the preparation of organic thin film transistor devices by solution process has become the top priority of many research teams. Because the principle of the solution method is to select a suitable solvent to dissolve the solid solute, so as to prepare solutions suitable for various processes, and to prepare crystalline thin films.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 471–479, 2022. https://doi.org/10.1007/978-981-19-1673-1_70

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Therefore, the solution method can greatly improve the utilization rate of materials. At the same time, for the realization of high throughput, commercialization and large area of processing expansion, the solution method has become the preferred process of preparation [5]. These processes include many new and self-created methods, simple spin coating [6], drop coating [7], as well as traditional printing methods [8]. Compared with the technology of chemical vapor deposition, however, the solution method is low cost, simple process, but the quality of the film still has a lot of progress in space [9]. This article focuses on the preparation and improvement of organic semiconductor thin films by different research groups in recent years. It also discusses the advantages and disadvantages of different processes, briefly introduces the application direction of organic thin film transistors, summarizes the experimental methods and looks forward to the development prospects of organic semiconductor thin film preparation processes.

2 Preparation of Organic Semiconductor Thin Film by Solution Process 2.1 Spin Coating There are various preparation methods of OTFTs, and the preparation of organic semiconductor thin films by the solution method is welcomed by the majority of researchers. Among them, the spin-coating [10] is to prepare crystalline or amorphous organic films by adjusting the concentration and rotation speed of the solution and selecting the solvent. Its outstanding advantages are simple operation and good film uniformity and compactness, but it also has more coffee rings [11]. Wang et al. [12] quantitatively analyzed the wetting behavior of organic semiconductor solution on the hydrophobic insulating layer, calculated the diffusion parameters, and finally prepared high-quality organic semiconductor layer by spin coating. Meanwhile, Yuan et al. [13] used the eccentric spin coating to prepare organic semiconductor thin films, and successfully prepared organic thin film transistor devices with a mobility of up to 43 cm2 /Vs, which gained widespread attention. The so-called eccentric spin coating is to place the substrate away from the center of the spin coater to prepare a thin film, as shown in Fig. 1.

Fig. 1. A schematic view of a spin coating process eccentric [13].

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However, spin coating can not only be applied to rigid substrates, as well as to flexible substrates. Ren et al. [14] prepared ultra-thin C8-BTBT OTFT arrays by spin coating, and optimized the spin coating speed, solution concentration and other parameters to increase the mobility to 11 cm2 /Vs. In Fig. 2, the ultrathin film prepared by them can be peeled off and adhered to the creases of fingers, knife blades, butterfly wings or even books, with good adhesion, without affecting the mobility of the device. This experimental method is simple and convenient for the preparation of ultra-thin film layer, which lays a certain foundation for the research of wearable electronic memory and biosensor.

Fig. 2. (a) is the preparation process of flexible devices, (b) is the application of OTFT [14]

2.2 Printing Process In addition, many teams hope to develop low-cost, large-scale fabricated devices, and use traditional printing processes to fabricate fully printed OTFTs, and have achieved different results. Duan et al. [15] deposited a water-soluble resist on the organic semiconductor layer by screen printing to protect it from etching. Finally, screen printing was used to position the sample to achieve high resolution and fabricate a pseudo CMOS inverter that can produce high gain and noise tolerance. At the same time, their team [16] used a combination of screen printing and dam to prepare a uniform and continuous film of C8-BTBT mixed with polymethyl methacrylate (PMMA). The highest mobility of the device reaches 12.1 cm2 /Vs. As shown in Fig. 3, the purpose of using the dam in 3(b) is to limit the diffusion of ink to change the crystallization process. It is proved that screen printing is a good choice for low-cost and efficient preparation of high-performance films.

Fig. 3. (a–b) Schematic diagram of the film prepared by screen printing, the optical microscope (OM) image of the screen printed C8-BTBT film without the dam (c–e) and with the dam (f–h) [16]

Ink-jet printing plays a very important role in the preparation of printing electronic devices. It is characterized by high quality printed film, good resolution and patternable.

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Liang et al. [6] constructed OTFT memory based on C8-BTBT and DNA complex as organic semiconductor layer and dielectric layer respectively, and measured the hole mobility of 0.65 cm2 /Vs, and the storage time of more than 100 s. They used the selective self-assembly of the organic semiconductor solution to the hydrophilic/hydrophobic solution, finally formed a high-resolution organic semiconductor array with a regular shape. Minemawari et al. [17] prepared C8-BTBT films using inkjet printing to control the formation of crystal nucleation. As shown in Fig. 4, nozzles A and B are filled with semiconductor solution and anti-solvent respectively. As the two ink solutions merge, the semiconductor solution-air interface begins to crystallize, and the creases of the film will be smoothed and then attached tightly. Using the pattern method in the figure, the single crystal yield reached 50%. It can be seen that inkjet printing can not only be used to print electrodes, but also a good single crystal film can be prepared in combination with the pattern method, which provides a good foundation for high-performance devices.

Fig. 4. Inkjet printing organic single crystal film: (a) inkjet printing preparation process, (b–d) a photomicrograph of the C8-BTBT film, (e) AFM image of the step structure on the film surface [17]

Kang et al. [18] used inkjet printing to study the effect of overlapping conditions and substrate temperature on film crystallization, resulting in a one-dimensional oriented TIPS-pentacene crystal structure, which avoided the formation of coffee rings. In the same way, Wang et al. [19] used Fuji Dimatix DMP3000 piezoelectric inkjet printer to prepare organic semiconductor thin films by changing the process parameters such as base temperature and drop distance, and obtained better thin film morphology. Similarly, Feng et al. [20] also used this printer to prepare fully printed transistors. It proves that the traditional printing method has considerable potential for large-scale and low-cost fabrication of transistors. 2.3 Other Solution Methods Solvent Vapor Annealing. Liu et al. [21] abandoned the traditional molecular annealing crystallization method and pioneered the solvent vapor annealing method (SVA) to obtain single crystal grains at the polymer-semiconductor interface, with a saturated mobility of 9.1 cm2 /Vs. SVA means that the finished film is placed in a solvent at room temperature, and the vapor pressure of the solvent is used for crystallization. As shown in Fig. 5, it can be seen that after SVA, as time increases, the crystal grains continue to grow. As we all know, single crystal particles can reach hundreds of microns, and

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Fig. 5. (a–f) Optical images acquired from SVA at different time periods, (g–i) AFM image of a one-dimensional single crystal [21]

the interface is also very smooth. This research provides an important method for the crystallization of thin films. Fluid-Enhanced Crystal Engineering. Diao et al. [22] invented a method called FLUENCE, as shown in Fig. 6. They designed a micro-columnar and crescent-shaped printing blade to promote crystal growth and control crystal nucleation. Ultimately, the good film morphology successfully increased the hole mobility of the device to 10 cm2 /Vs. Analogously, this is somewhat similar to the principle of the meniscus guiding coating [23], which regards the meniscus as the gas-liquid interface when the solution evaporates. The solvent in the solution evaporates, and the solute reaches the saturation point and precipitates and deposits on the substrate to form a uniform film.

Fig. 6. Picture of film preparation with crescent blade [22]

Droplet Pinned Method. Liu et al.[24]. adopted an improved “fixed drop method”. A solid needle was placed in a centimeter-sized area as a solution holder, and a largescale ordered crystal array of organic semiconductors of TIPS-pentacene, anthracene, tetraene, perylene, and C60 [24] was prepared, achieving 6.46 cm2 /Vshole mobility. As shown in Fig. 7, the organic field-effect transistors prepared by this method have almost all mobility greater than 1 cm2 /Vs, the maximum value can reach 6 cm2 /Vs, and the threshold voltage is between 20–58 V. The film prepared by this method has good morphology, but the repetition rate is not good, and further investigation is needed.

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Fig. 7. (a–f) Scaling growth and optical microscope images of pentacene and (g) experimental steps of needle pruning method [24]

Push Coating. Ikawa et al. [25] developed a push-coating technique, as shown in Fig. 8. Push-coating technology refers to compressing microliter droplets through a viscoelastic PDMS die to generate a thin organic semiconductor layer on the surface of the substrate. They designed a PDMS/fluorocarbon polymer/PDMS stamp, where the PDMS layer is used as a double-surface contact layer, and the fluorocarbon polymer is used as a barrier layer to prevent solvent diffusion. The three-layer structure effectively promotes the solvent retention in the die and reduces the deformation of the die on the solvent adsorption. More importantly, even if the imprinting lasts for a long time, the stamper and the semiconductor polymer film can be perfectly peeled off. The film quality and mobility prepared by this experimental method are better than those prepared by spin coating.

Fig. 8. Schematic diagram of push-coating semiconductor polymer films

Many of the above-mentioned research methods for preparing organic semiconductor thin films by solution methods are different. But many of them just stay in the laboratory research stage. As shown in Table 1, the preparation of spin-coating can obtain higher mobility and lower threshold voltage, but large-scale production requires more sophisticated process requirements and superior film properties. In the process of preparing the film, not only the quality of the film, but also the influence of the interface defects on the carrier transport should be considered, so that the mobility can be improved continuously. The self-created preparation methods of each team can get good films, which need further study to achieve commercialization. Ultimately, the printing method is the one with the greatest potential for commercialization.

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Table 1. Device characteristics by different preparation processes Method Spin coating

Printing

Other

Semiconductor

Threshold voltage (V)

On/off ratio

Mobility (cm2 V−1 s−1 )

Ref

Off-center

C8-BTBT

/

/

43

[13]

On-center

C8-BTBT

−15

Over 106

11

[14]

TIPS pentacene

0.11

107

0.11

[26]

Screen printing

C8-BTBT/PMMA

−12

8 × 109

12.1

[16]

Inkjet printing

C8-BTBT

−10

105 –107

16.4

[17]

TIPS pentacene

−0.5

5.8 × 106

~0.13

[18]

TIPS-PEN

−21

105

0.78

[19]

TIPS-PEN/PS

−0.17

3.1 × 105

0.26

[20]

C8-BTBT

/

105

9.33

[27]

Solvent vapor annealing

C8-BTBT

−18.9

107

9.1

[21]

Fluid-enhanced crystal engineering

TIPS pentacene

/

106– 108

11

[22]

Droplet pinned method

TIPS pentacene

−27.16

3.61 × 106

6.46

[24]

Push coating

P3HT

/

/

0.47

[25]

3 Conclusions and Outlook To sum up, this paper focuses on the research on the preparation process of organic semiconductor films in recent years, starting from the spin-coating, printing process and the self-created method of each team. Some teams adhere to the concept of the simplest way to develop the best device, through continuous efforts to achieve many excellent results. There are also many teams that have developed or upgraded their own processes to produce high-performance OTFTs. In addition, other groups are combining traditional printing methods with novel device fabrication methods to develop low-cost, high-throughput fabrication methods. Their methods are quite feasible in the laboratory and in theory, but the improvement and innovation of many methods still have problems such as a complex process, low mobility and inapplicability to high-throughput production. In this rapidly changing era, these devices have good stability when applied to sensors, nonvolatile memory and electrical switches. For example, OTFT can be applied to pressure sensors, steam sensors, biosensors as the sensor identification element. It can be made into a variety of bio-sensing devices in conjunction with the dielectric material, for individuals to provide health care services, including routine health monitoring, health records and elderly care. OTFT can also be used as non-volatile memory, which has the characteristics of non-destructive reading and high integrated density. Meanwhile, it has the advantages of low cost, flexibility and large area preparation, and has an adjustable storage window, which can meet the requirements of memory. Finally, the OTFT is used as a switching element for organic light-emitting diodes (OLED), which control the switching state of the diode. Based on the actual application, however, these different experimental methods and ideas, will be the preparation for the future the OTFT device

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to lay the firm foundation of large area, but also indicate the direction for its wider application. We also believe that OTFT has great potential in the direction of flexible biosensors and non-volatile memory, which requires people to concentrate on research and invention.

References 1. Ryu, G.S., Kim, J.S., Jeong, S.H., Song, C.K.: A printed OTFT-backplane for AMOLED display. Org. Electron. 14, 1218–1224 (2013) 2. Jung, M., et al.: All-printed and roll-to-roll-printable 13.56-MHz-operated 1-bit RF tag on plastic foils. IEEE Trans. Electron. Dev. 57, 571–580 (2010) 3. Pierre, A., Deckman, I., Lechêne, P.B., Arias, A.C.: High detectivity all-printed organic photodiodes. Adv. Mater. 27, 6411–6417 (2015) 4. Minari, T., Liu, X., Kanehara, M.: Printable electronic circuits based on metal nanoparticles and organic semiconductors. In: 2018 International Conference on Electronics Packaging and iMAPS All Asia Conference (ICEP-IAAC) (2018) 5. Mohammed, M.G., Kramer, R.: All-printed flexible and stretchable electronics. Adv. Mater. 29(19), 160496 (2017) 6. Liang, L., Liu, X., Kanehara, M., et al.: Layer-by-layer printing non-volatile organic thin-film transistor memory with a planarly-oriented DNA-complex dielectric. Org. Electron. 55(Apr), 75–81 (2018) 7. Chandrakasan, A.P., Sheng, S., Brodersen, R.W.: Low-power CMOS digital design. IEEE J. Solid-State Circ. 27(4), 473–484 (1992) 8. Dennard, R.H., Gaensslen, F.H., Rideout, V.L., Bassous, E., Leblanc, A.: Design of ionimplanted MOSFET’s with very small physical dimensions. IEEE J. Solid-State Circ. 9(5), 256–268 (1974) 9. Wuu, D., Horng, R., Tsai, T.: Light emitting diode. Yale Rev. 42(4), 173–180 (2005) 10. Acton, O., Dubey, M., Weidner, T., et al.: Organic thin-film transistors: simultaneous modification of bottom-contact electrode and dielectric surfaces for organic thin-film transistors through single-component spin-cast monolayers. Adv. Funct. Mater. 21(8), 1328–1328 (2011) 11. Wang, Z., Guo, H., Li, J., Wang, L., Dong, G.: Marangoni effect-controlled growth of oriented film for high performance C8-BTBT transistors. Adv. Mater. Interfaces 6(8), 1801736 (2019) 12. Wang, S., Zhao, X., Tong, Y., Tang, Q., Liu, Y.: Directly spin coating a low-viscosity organic semiconductor solution onto hydrophobic surfaces: toward high-performance solutionprocessable organic transistors. Adv. Mater. Interfaces 7, 1901950 (2020) 13. Yuan, Y., Giri, G., Ayzner, A.L., Zoombelt, A.P., Mannsfeld, S.C., Chen, J.: Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method. Nat. Commun. 5(1), 1–9 (2014) 14. Ren, H., Cui, N., Tang, Q., Tong, Y., Zhao, X., Liu, Y.: High-performance, ultrathin, ultraflexible organic thin-film transistor array via solution process. Small 14(33), 1801020 (2018) 15. Duan, S.M., et al.: Solution-processed centimeter-scale highly aligned organic crystalline arrays for high-performance organic field-effect transistors. Adv. Mater. 32, 1908388 (2020) 16. Duan, S., Gao, X., Wang, Y., et al.: Scalable fabrication of highly crystalline organic semiconductor thin film by channel-restricted screen printing toward the low-cost fabrication of high-performance transistor arrays. Adv. Mater. 31(16), 1807975 (2019) 17. Minemawari, H., Yamada, T., Matsui, H., et al.: Inkjet printing of single-crystal films. Nature 475(7356), 364–367 (2011)

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18. Kang, B.J., Oh, J.H.: Influence of substrate temperature and overlap condition on the evaporation behavior of inkjet-printed semiconductor layers in organic thin film transistors. Thin Solid Films 598(Jan.1), 219–225 (2016) 19. Wang, X., Yuan, M., Xiong, X., et al.: Process optimization for inkjet printing of triisopropylsilylethynyl pentacene with single-solvent solutions. Thin Solid Films 578, 11–19 (2015) 20. Feng, L., Jiang, C., Ma, H., et al.: All ink-jet printed low-voltage organic field-effect transistors on flexible substrate. Org. Electron. 38(Nov), 186–192 (2016) 21. Liu, C., Minari, T., Lu, X., et al.: Solution-processable organic single crystals with bandlike transport in field-effect transistors. Adv. Mater. 23(4), 523–526 (2011) 22. Liu, C., Minari, T., Lu, X., Kumatani, A., Takimiya, K., Tsukagoshi, K.: Solution-processable organic single crystals with bandlike transport in field-effect transistors. Adv. Mater. 23, 523–526 (2011) 23. Ying, D., Shaw, L., Bao, Z., et al.: Morphology control strategies for solution-processed organic semiconductor thin films. Energy Environ. Sci. 7(7), 2145–2159 (2014) 24. Liu, S., et al.: Large-scale fabrication of field-effect transistors based on solution-grown organic single crystals. Sci. Bull. 60(12), 1122–1127 (2015). https://doi.org/10.1007/s11434015-0817-9 25. Ikawa, M., Yamada, T., Matsui, H., et al.: Simple push coating of polymer thin-film transistors. Nat. Commun. 3, 1176 (2012) 26. Park, Y., Baeg, K.J., Kim, C.: Solution-processed nonvolatile organic transistor memory based on semiconductor blends. ACS Appl. Mater. Interfaces 11(8), 8327–8336 (2019) 27. Fang, X., et al.: Patterning liquid crystalline organic semiconductors via inkjet printing for high-performance transistor arrays and circuits. Adv. Funct. Mater. 31, 2100237 (2021)

Preparation of a Fluorinated Latex via RAFT Surfactant-Free Emulsion Polymerization Zhongxiao Li, Hongli Zhang, Hanyu Cai, and Li An(B) Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. Firstly, an amphiphilic fluorinated block copolymer was prepared via reversible addition fragmentation chain transfer (RAFT) polymerization of acrylic acid, dodecafluoroheptyl methacrylate (DFHMA) and methyl methacrylate (MMA), which was characterized by gel permeation chromatography (GPC). Then using the fluorine-containing block copolymer as the emulsifier, stearyl alcohol as the co-emulsifier and the combination of tert-Butyl hydroperoxide (TBH) and ascorbic acid (LAA) as the initiator, a fluorinated latex was prepared by emulsion copolymerization of DFHMA and butyl methacrylate (BMA). The prepared fluorinated latex was stable and had a uniform particle size distribution. Finally, thin latex coatings were prepared with the fluorinated latex, and the wettability of the latex coating and the effect of heat treatment on the affinity of the coating were investigated. Keywords: RAFT · Fluorinated amphiphilic block copolymer · Fluorinated latex · Contact angle · Wettability

1 Introduction Fluoropolymer, also known as fluororesin, is a general term for synthetic resins containing fluorine atoms in molecules, which is mainly polymerized by vinyl fluoride monomers or by incorporating fluorinated monomer to the main chain of acrylate polymers. Fluoropolymers exhibit good heat resistance, low temperature resistance, excellent weather resistance, electrical insulation, chemical corrosion resistance and ultralow surface tensions, which have been drawing more and more attention. They are widely used in electronics, chemical industry, automobile and construction industry, textile, medicine and other fields [1–4]. The general methods for the synthesis of fluoropolymers are solution polymerization and emulsion polymerization. Solution polymerization requires uncommon solvents such as fluorine-containing solvents, which are more expensive and less environmentally friendly. Emulsion polymerization uses water as the reaction medium, which is green and low cost. In emulsion polymerization, monomers need to be transferred from the monomer droplets to micelles through water phase. However, fluorinated acrylate monomers usually have extraordinarily low aqueous solubility and are typically difficult to emulsify. These make classical emulsion polymerization not suitable for those cases © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 480–486, 2022. https://doi.org/10.1007/978-981-19-1673-1_71

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involving fluorinated acrylate monomers. An improved emulsion polymerization method suitable for fluorinated monomers is to add organic solvents in the continuous phase. The introduction of organic solvents increases the solubility of fluorinated monomer [5]. In addition, a so-called core-shell structured fluorine containing emulsion can be prepared by semi-continuous seeded emulsion polymerization. Here, a first stage polymer emulsion was swelled with the fluoromonomer and polymerized by semi-batch method in the second stage, giving core-shell particles containing a fluoropolymer in the shell. Seed emulsion polymerization has the advantages of narrow particle size distribution, facile molecular design and so on. The main disadvantage of this method is that it is only suitable for polymerizable monomers with less fluorine content due to the requirement of a compatibility between the first stage polymer and the fluorinated monomers [6, 7]. Recent studies have shown that the miniemulsion polymerization with droplet nucleation can be used for polymerization of fluorinated monomers. For miniemulsion polymerization, it is not necessary that monomers transport through the water phase, whereas droplet nucleation of minidroplet is the key step. It also requires the presence of special emulsifiers suitable for fluorinated monomers, such as fluorinated surfactants and (or) long-chain hydrophobic surfactants, which are not easily available [8, 9]. Amphiphilic fluorinated block copolymers have fluorinated units, which should exhibit better affinity for fluorine-containing monomers and polymers. As a result, they are likely to be the appropriate emulsifiers for fluorinated monomers. In this paper, an amphiphilic fluorinated block copolymer was prepared and used in the emulsion copolymerization of dodecafluoroheptyl methacrylate and butyl methacrylate. It will be shown that a stable fluorinated latex with narrow size distribution can be made by this process.

2 Experimental 2.1 Materials DFHMA, BMA, MMA, acrylic acid, azodiisobutyronitrile (AIBN), L-ascorbic acid (LAA), vanadium(IV) oxide sulfate (VOSO4 ) and TBH (70% solution in water) were purchased from Beijing Chemicals Co. and used as received. 2-(((Dodecyl-thio) carbonothioyl)thio)-2-propanoic acid (DCTPA) was prepared in our lab. Deionized water was used as the aqueous media. All organic solvents are commercial products. 2.2 Preparation of Fluorinated Block Copolymer (FBP) DCTPA (4.86 g), acrylic acid (20 g), 1,4-dioxane (25 g) and AIBN (0.5 g) were successively added into a 250 mL four-necked flask equipped with a reflux condenser, a mechanical agitator, a nitrogen inlet and a thermometer. The mixture was stirred at ambient temperature to give a clear solution. The mixture was stirred at 70 °C for 16 h. Then, DFHMA (40 g), MMA (10 g), AIBN (0.40 g) and 1,4-dioxane (20 g) were added into the reaction mixture. Additional AIBN (0.12 g) was added after 12 h and stirred for another 12 h. A clear viscous liquid was obtained. Under stirring, the liquid was poured into 500 mL of water to obtain a yellowish solid, which was washed with water, collected and dried. Yield: 95.6%.

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2.3 Preparation of the Fluorinated Latex First, FBP (7.50 g) was dissolved in an aqueous solution prepared by dissolving 0.30 g of sodium hydroxide in 105 g of water. Then, a solution of DFHMA (18.0 g), BMA (4.5 g) and octadecanol (0.3 g) was added to the above aqueous solution. The mixture was treated with a high pressure homogenizer for 15 min to obtain pre-emulsified monomer mixture. Afterwards, the pre-emulsion, TBHP (0.27 g) and a small amount of VOSO4 were placed in a four-necked flask equipped with a heat exchange system and mechanically stirred for 0.5 h at 30 °C. After de-airing with nitrogen, a solution of LAA (0.36 g) in water (7.5 g) was added drop by drop slowly into the reactants in about 1.5 h. Finally, the emulsion was filtered with a Buchner funnel. Then the fluorinated latex was obtained.

3 Results and Discussion 3.1 Preparation of FBP and the Fluorinated Latex As shown in Scheme 1, FBP was prepared by two-step RAFT polymerization in the presence of DCTPA. At the first step of RAFT polymerization of acrylic acid, low molecular weight poly(acrylic acid) (PAA) was obtained. Then at the second step of RAFT copolymerization of DFHMA and MMA, FBP was obtained. GPC was used to measure the molecular weight of the two products in the different stages of polymerization, i.e., PAA and FBP (Table 1). The number average molecular weights (M n ) of PAA and FBP measured by GPC were 1865 and 5401 respectively, which were close to the calculated values. Additionally, the polydispersity index was less than 1.55. These results demonstrated the living nature of the polymerization. Emulsion copolymerization of DFHMA and BMA was carried out in the presence of FBP which was partially neutralized by sodium hydroxide. FBP acted as a reactive emulsifier for its involvement in the emulsion polymerization, and finally became part of the formed particles. Furthermore, the hydrophilic moieties of FBP, namely the sodium carboxylate groups, were located on the surface of the latex particles and formed a stable hydrophilic layer which contributed to the stability of the emulsion. The size distribution of the fluorinated latex was measured by a Malvern ZETASIZER Nano (Fig. 1). The average radius of the particles was around 60 nm and the corresponding polydispersity index (PDI) was 0.065, indicating that the fluorinated latex was nearly monodisperse. Figure 2 showed the Fourier transform infrared spectrometry (FTIR) spectra of FBP and the fluorinated latex polymer. The band of C = C at 1630 cm−1 was not found, indicating that all the monomers had been polymerized to high polymer. There were some similar absorption bands, such as the C-H stretch vibration peaks at 2930 cm−1 and 2854 cm−1 , the bending vibration peaks at 1450 cm−1 (CH2 ) and 1387 cm−1 (CH3 ), the characteristic absorption of ester group (C = O) at 1732 cm−1 , and those at 1160– 1235 cm−1 which were assigned to the C-F absorption peaks. The strong absorption at 1704 cm−1 in Fig. 2(a) was ascribed to the carboxylic acid group (COOH) of FBP. By comparison, the fluorinated latex polymer did not exhibit obvious characteristic absorption near 1704 cm−1 (Fig. 2(b)), which was thought to be due to its low content of carboxylic acid group.

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Scheme 1. Preparation of FBP and the fluorinated latex Table 1. Determination of molecular weights of PAA and FBP by GPC* Sample

Retention time

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The thermal stability was characterized by thermal gravimetric (TG) analysis of the fluorinated latex polymer. As shown Fig. 3, there was little weight loss (99.9%), guanidine thiocyanate (>99%), 1-propyl-3-methylimidazole iodide (>98%), 4-tert-butylpyridine (>96%) were purchased from Alfa Aesar Reagent Co., Ltd.; ITO-PET was purchased from Xi’an Qiyue Biotechnology Co., Ltd. 2.2 Preparation of PEDOT Gel 2 g PEDOT: PSS solution, 60 mg or 120 mg lithium iodide (LiI) 50 wt% aqueous solution and 300 mg 1 wt% sodium carboxymethyl cellulose aqueous solution were mixed and sealed in a glass bottle. Keep the mixed solution at 90 °C for 3 h. The prepared hydrogel is purified by repeated washing with deionized water. The hydrogel is immersed in the electrolyte (1-propyl-3-methylimidazole ammonium iodide (0.6 M), I2 (0.01 M), LiI (0.1 M), 4-tert-butylpyridine (0.5 M), thiocyanate guanidine (0.5 M)) and allowed to stand for 24 h. The two PEDOT: PSS hydrogel electrolytes DSSC were obtained and named Gel 1-DSSC and Gel 2-DSSC, respectively. 2.3 DSSC Assembling The ITO-PET was washed with acetone, ethanol and deionized water respectively. The titanium dioxide paste and Pt paste were transferred to ITO-PET by screen printing, and heated at 125 °C for 1 h. The ITO-PET coated with titanium dioxide slurry was immersed in a dye bath of N719 dye solution for 24 h to obtain a photoanode. PEDOT: PSS hydrogel electrolyte was transferred to the photoanode by screen printing. The sarin film was cut into a hollow structure and placed between the photoanode and the counter electrode. Heating it with a hot press at 120 °C for 20 s to complete the cell packaging.

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3 Results and Discussion 3.1 Scanning Electron Microscope of Gel Electrolyte It can be seen from Fig. 1 (a) that the structure of the aerogel obtained by freeze-drying the PEDOT: PSS solution was in a disordered state and had no pores. The freeze-dried aerogel of PEDOT gel in Fig. 1 (b) showed a clear pore structure. This is because the addition of lithium salt provides a large number of cations, which breaks the electrostatic interaction between the PEDOT molecular chain and the PSS molecular chain, so that the PEDOT molecular chain breaks the bondage of the PSS chain and realizes the regular accumulation between chains, gradually forming gel.

Fig. 1. SEM images of (a) aerogel obtained by freeze-drying a PEDOT: PSS solution; (b) aerogel obtained by freeze-drying PEDOT gel electrolyte

3.2 Photovoltaic Performances of DSSC Figure 2 (a) showed the J-V curves based on the liquid electrolyte DSSC(L-DSSC), Gel 1-DSSC and Gel 2-DSSC, and the corresponding photoelectric parameters were shown in Table 1. The DSSC assembled with pure ionic liquid electrolyte had the highest efficiency, reaching 7.25%, and the V OC , J SC and FF are 0.77 V, 14.11 mA/cm2 and 0.66, respectively. The efficiencies of Gel 1-DSSC and Gel 2-DSSC were 5.13% and 5.84%, respectively. When the added amount of lithium salt was increased from 60 mg to 120 mg, the efficiency of the DSSC was also improved. As shown in Fig. 2 (b), the electrolyte and the platinum counter electrode were assembled into a symmetrical structure of Pt counter electrode/electrolyte/Pt counter electrode, and the energy quist was tested with an electrochemical workstation to study the electrolyte/counter electrode electrochemical impedance behavior at the interface. Both Rs and Rct increased in the order of L-DSSC < Gel 2-DSSC < Gel 1-DSSC, indicating that the catalytic activity of Gel 2-DSSC is the highest in the order of I− 3 reduction. The assembled PEDOT gel has a network-like microstructure, which provides a channel for charge transport.

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Fig. 2. (a) J-V curves of L-DSSC, Gel 1-DSSC and Gel 2-DSSC; (b) Nyquist plots of L-DSSC, Gel 1-DSSC and Gel 2-DSSC Table 1. J-V curve parameters of L-DSSC, Gel 1-DSSC and Gel 2-DSSC Jsc (mA/cm2 ) Voc (V) FF L-DSSC

η (%)

14.11

0.76

0.65 6.97

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3.3 Stability Analysis of DSSC In order to further compare the stability of the cell, an outdoor stability test was carried out. As shown in Fig. 3, the JSC of the L-DSSC began to decrease significantly after 300 h of operation, while the QS-DSSC began to decrease significantly after 410 h of operation. Under the same packaging conditions, the decrease of JSC may be caused by the electrolyte volatilizes or is caused by leakage. After 1000 h, the efficiency of the liquid electrolyte DSSC is only 75% of the original efficiency, while QS-DSSC still maintains 90% of the original efficiency.

Fig. 3. Stability analysis of L-DSSC, Gel 1-DSSC and Gel 2-DSSC

4 Conclusions In summary, PEDOT gel with different lithium contents was prepared and used as electrolyte to prepare DSSC, and the performance of DSSC was characterized. The results

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showed that as the amount of lithium added increases, the pore space of the gel will become larger, thereby adsorbing more electrolyte, resulting in an increase in the efficiency of DSSC. When the lithium content was 120 mg, the efficiency of the gel electrolyte DSSC reaches 5.84%. Compared with liquid electrolytes, gel electrolyte DSSC had longer lasting stability. After 1000 h of testing, the gel electrolyte DSSC can still maintain 90% of the original efficiency. Acknowledgements. This work was supported by the Key Scientific Research Project of Beijing Municipal commission of Education (KZ201910015016), the National Natural Science Foundation of China (21776021), the BIGC Key Project (Ec202004), and the Cross training Plan for High Level Talents in Beijing.

References 1. Liu, I., Hung, W., Teng, H., Venkatesan, S., Lina, J., Lee, Y.: High-performance printable electrolytes for dye-sensitized solar cells. J. Mater. Chem. A 5(19), 9190–9197 (2017) 2. Jiao, S., et al.: Development of rapid curing SiO2 aerogel composite-based quasi-solid-state dye-sensitized solar cells through screen-printing technology. ACS Appl. Mater. Interfaces 12(43), 48794–48803 (2020) 3. Liu, Y., et al.: Soft and elastic hydrogel-based microelectronics for localized low-voltage neuromodulation. Nat. Biomed. Eng. 3(1), 58–68 (2019) 4. Feig, V., Tran, H., Lee, M., Bao, Z.: Mechanically tunable conductive interpenetrating network hydrogels that mimic the elastic moduli of biological tissue. Nat. Commun. 9(1), 1–9 (2018) 5. Leaf, M., Muthukumar, M.: Electrostatic effect on the solution structure and dynamics of PEDOT: PSS. Macromolecules 49(11), 4286–4294 (2016)

High-Performance Flexible Photodetector with Two-Dimensional Graphene Heterostructure Mengzhu Wang, Yingying Xiao, Huiqing Zhao, Huiling Zhang, Dan Zhao, and Ruping Liu(B) School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. With the rapid development of optoelectronics, the demand for flexible electronic products such as smart phones, wearable devices, and electronic tattoos continues increasing. As a typical optoelectronic device, flexible photo detectors with bendable and foldable functions are widely used in various fields. As a new functional material with excellent electrical and optical properties, graphene can be composited with various flexible substrates. Among them, graphene-based optoelectronic devices with heterostructures have excellent properties and have become a research hotspot in the field of photoelectric detection in recent years. This article first reviews the development of graphene-based photo detectors. Then focus on the systematic analysis of three different types of grapheneheterostructure photodetectors, discuss its unique coupling mechanism and the novel characteristics that they exert. Finally, it summarizes the future applications of graphene heterojunction flexible photodetection and the challenges faced in this field. Keywords: Graphene · Photodetector · Heterostructure · Flexible device

1 Introduction The core of the photodetector is to convert the absorbed photon energy into a detectable electrical signal through an electronic process. Flexible photodetectors have many advantages, such as small size, bending resistance, and high sensitivity. Hence, their applications in bionics, medical care, and wearable devices have attracted more and more attention. However, such flexible devices need to maintain stable performance during repeated bending, folding, or stretching, which places high requirements on the mechanical stability and flexibility of the electrodes and functional materials. As the first 2D layered material known to people, graphene has attracted wide attention due to its unique optical absorption capacity, extraordinary elastic modulus, and extremely high carrier mobility [1, 2]. Many researchers applied it to optoelectronic devices and obtained excellent performance. However, the all-graphene-based photodetector still has many limitations. Here, we first give a brief introduction to all-graphene-based devices. Then focus on the highperformance graphene heterostructure photodetector, analyze the device parameters © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 511–517, 2022. https://doi.org/10.1007/978-981-19-1673-1_76

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according to the heterogeneous composite of different materials and graphene, and discuss its application in flexible wearable electronic devices. Finally, the full text is summarized and prospects for the development of this field are given.

2 Full Graphene Photodetector Graphene is a 2D allotrope of carbon atoms, which is formed by the covalent bonding of carbon atoms. Its unique two-dimensional layered nanostructure gives it outstanding thermal conductivity and robust strength, excellent physical properties and good chemical stability, with a Young’s modulus as high as 1.0 TPa and a tensile strength of 130 Gpa. Graphene has a very high intrinsic electron mobility (20000 cm2 v−1 s−1 ), and can achieve micron-scale ballistic transmission at room temperature [3]. As shown in Fig. 1, graphene has unique absorption spectrum which covers most of the electromagnetic spectra (from far-infrared to ultraviolet) [2, 4]. Moreover, the electron mobility of graphene is less affected by temperature changes. At any temperature between 50 and 500 K, the electron mobility of single-layer graphene is about 15000 cm2 v−1 s−1 . It can maximize the gain of the photodetector device, can be processed into structures of different shapes, and has a broad prospect in flexible optoelectronic devices.

Fig. 1. Band gap value and detection range of various two-dimensional materials [4]

In 2009, Xia et al. made the first graphene photodetector with graphene as a lightabsorbing layer. By adjusting the back gate bias, the channel carrier concentration is indirectly controlled, and ultra-fast photodetection is obtained. For light-emphasizing up to 40 GHz, the light response will not be reduced [5]. Subsequently, the American IBM’s Mueller et al. used the asymmetric interdigital electrode method to improve the performance of the graphene photodetector, and realized the optical data link communication at 1550 nm at 10 Gbit/s [6]. Compared with symmetrical electrodes, the asymmetrical electrode structure can enhance the built-in electric field, reduce the barriers to carrier migration, and greatly improve the sensitivity, so it has the advantages of

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high stability and fast response speed. The fabrication of full graphene photodetectors is mainly based on the high quality growth technology of graphene. As the Chemical vapor deposition (CVD) technology has become more mature, researchers have demonstrated large-area growth of graphene by low-temperature metal-free plasma-enhanced CVD, and fabricated all-graphene photo detectors. The detector has a high response rate in the visible light range, and the maximum photogenerated current can reach mA level. However, graphene itself does not have a band gap, which will cause the dark current of the device to be too high. The light absorption of single-layer graphene is only 2.3%. This weak light absorption limits the concentration of photogenerated carriers [7], resulting in very low photo responsivity and sensitivity of the device. Therefore, as to how to improve the performance of graphene detectors, researchers have made many attempts. The following focuses on graphene-heterostructure composite devices to analyze their performance.

3 Graphene Heterostructure Photodetector Heterojunction is the interface area formed by the contact of two different semiconductors. This structure usually has excellent optoelectronic properties that cannot be achieved by the respective PN junctions of the two semiconductors. Many heterostructures obtained by doping two-dimensional materials with graphene can greatly improve the performance of photodetectors, such as expanding the working wavelength of the device and improving the responsivity. Studies have shown that van der Waals (vdWs) heterojunction is an effective way to realize broadband polarization-sensitive photodetection [8]. 3.1 Graphene/Semiconductor Heterojunction Photodetector Graphene-semiconductor heterojunction photodetectors can simultaneously use the excellent light absorption of semiconductors and the ultra-high mobility of graphene to solve several basic problems in photodetector applications, such as weak light absorption, the short lifetime of the order of picoseconds of photogenerated carriers in graphene, small effective detection area, etc. Photoinduced electron-hole pairs are separated at the graphene/semiconductor interface. This unique heterostructure breaks the limitations of epitaxial growth in the past, such as point defects and dislocations caused by interatomic diffusion and lattice mismatch. The external quantum efficiency of this device is relatively high. Due to its gain mechanism, the response rate is extremely high and can be adjusted by applying a reverse bias. Such as ZnO, a semiconductor material with a wide band gap of ≈3.37 eV and transparent conductivity. The graphene/ZnO heterojunction flexible photodetector can achieve broadband detection in the ultraviolet to visible range at room temperature, and have extremely high photoconductivity under external voltage [9]. In addition, TiO2 nanomaterials are non-toxic and low-cost, with good chemical stability and thermal stability, which can be used as a shielding layer in optoelectronic devices to prevent the penetration of water molecules and oxygen, and provide excellent electron transport

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performance and relatively high electron mobility. As shown in Fig. 2a, after photoexcitation of graphene, electrons are transferred to the TiO2 layer under the built-in field, and holes are transferred multiple times in the graphene channel. For ultraviolet light, the TiO2 layer absorbs most of the light power and generates electron-hole pairs, and electrons are injected into the graphene channel. This graphene/TiO2 heterojunction photoelectric device has extremely high photoconductivity gain and photosensitivity [10]. Dr. Shuchao Qin from Nanjing University and others fabricated a graphene/C60 heterostructure photodetector on a PET (Polyethylene terephthalate) substrate. The tight electronic coupling on the all-carbon interface improves the efficiency of interface charge transfer. Coupled with the excellent light absorption capacity of C60 , the detector can detect brighter signals including fluorescent lights and has excellent mechanical flexibility. At present, there are also methods for directly growing semiconductor materials on graphene films (Fig. 2b), which can avoid the pollution caused during the transfer process, and manufacture graphene heterostructure photodetectors with high uniformity and controllability [11, 12].

Fig. 2. (a) Energy level diagram of the graphene/TiO2 interface [10] (b) The epitaxial growth of PbI2 crystals on the graphene surface [12]

3.2 Graphene/Transition Metal Disulfide Heterojunction Photodetector There are high absorption coefficients and light induced electron-hole pair generation in the atomic thin heterostructure, which has broad prospects in the application of optoelectronic devices. The transition metal disulfides (TMDs) that form this heterostructure are a layered material with strong in-plane bonding and weak out-of-plane bonding. As a two-dimensional vdWs crystal, TMDs have unique electronic and mechanical properties. It has a flat and clean interface without dangling bonds, high carrier mobility, and narrow band gap. Graphene can be stacked with these different two-dimensional materials into vdWs heterostructures, without the limitations of lattice mismatch [13]. Because the energy gap is located in the visible spectrum of solar radiation and the chemical stability is relatively high, molybdenum disulfide (MoS2 ) is the most researched TMDs used in optoelectronic devices in recent years. The layered configuration of graphene/MoS2 can maximize the optical response of graphene devices. The simple and adjustable characteristics of the graphene Fermi surface make it a tunable electrode to effectively separate photo-generated carriers. The device of this kind of heterogeneous structure can work without external bias voltage, which greatly reduces

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the power consumption while improving the detection rate of the device. In order to achieve better flexibility, graphene photoelectric devices can be made on ordinary cellulose paper. Pairkshit et al. used a dip coating method to deposit graphene on paper, and then hydrothermally grew MoS2 to fabricate a paper-based graphene/MoS2 visible light photodetector. This high photogain heterostructure device is more sensitive to visible light [14]. Later, Pataniya et al. fabricated the WS2/graphene heterostructure photodetector, which has excellent light response performance in a wide spectral range. After optimization, it achieved 0.439 AW−1 responsivity and 1.41 × 1010 jones detection rate, showing a stable light response within 500 bending cycles [15]. Compared with the traditional covalent bonds and thin film heterostructures, this transition metal disulfide heterostructure has higher interface quality and will not cause problems such as lattice mismatch strain due to the lack of covalent bonds. 3.3 Graphene/Perovskite Heterojunction Photodetector Organic-inorganic halide perovskite CH3 NH3 PbI3 (MAPbI3 ) has excellent optoelectronic properties, long charge carrier lifetime, high photoluminescence quantum efficiency, and large defect tolerance. These materials can provide synergistic effects in optoelectronic devices and complementarily improve the performance of each component [16]. Due to suppressed charge recombination, the halide perovskite-graphene photodetector exhibits higher light responsiveness. Zheng et al. of Sun Yat-sen University designed a low-temperature two-step method to synthesize highly crystalline perovskite nanosheets, and fabricated a flexible photodetector with a high light response of 12 AW−1 and a fast response speed of 2.2 ms. The device has repeatable bending stability [17]. The formation of spatially inefficient perovskite islands on graphene will produce perovskite grains with lower crystallinity, which will reduce the photogenerated carrier density compared with the perovskite layer. Therefore, a problem to be overcome by highperformance graphene hybrid photodetectors is to effectively combine high-efficiency plasma nanoparticles with high-density perovskite films. Lee et al. developed a graphene hybrid photodetector with high-efficiency light-trapping characteristics. As shown in Figure 3, its light response rate is 5.90 × 104 AW−1 , and the specific detection rate is 1.31 × 1013 jones, which is the highest detection value of perovskite-functionalized graphene photodetectors reported so far. Repeated bending 1000 times, the light response rate is still good, with significant mechanical durability [18]. The response speed, responsivity and stability of flexible graphene/perovskite hybrid photodetectors need to be further improved. This simple and low-cost manufacturing provides the possibility for largescale applications in sensitive broadband detection. Researchers have developed selfpowered photodetectors [19]. These new flexible graphene hybrid photodetectors are expected to contribute to the development of wearable photodetectors, and imaging sensors suitable for microlight photography.

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Fig. 3. (a) The flexible G-GNS-P-PD device structure (b) Physical picture (c) The photocurrent and dark current of the device under 1000 cycles [18]

4 Conclusion Flexible photodetectors can retain its performance under large strains, and are receiving more and more attention in electronic eyes, bionic sensing, smart textiles and wearable devices. This article reviews the latest developments in graphene heterojunction flexible detector. By combining graphene with different materials, the sensitivity can be significantly improved. There are still the following problems in this field, such as the coupling principle of heterojunction and the charge transfer between different material interfaces need to be studied in depth, which is very important for improving the performance of heterojunction photodetectors and the design of new-principle optoelectronic devices. For applications in different fields, the focus of improving device performance is also different, and further exploration is needed to find the best method. For example, for the detection of weak light, the surface plasmon polaritons can be used to improve light absorption, and for optical communication, the response of the detector can be enhanced by compounding semiconductor quantum dots on graphene, etc. Acknowledgments. This work was supported by the National Natural Science Foundation of China (No. 61971049), the Key Scientific Research Project of Beijing Municipal Commission of Education (KZ202010015024), the Research and Development Program of BIGC (Ec202006), and the Beijing Municipal Science and Technology Commission (Z181100004418004).

References 1. Huo, N., Konstantatos, G.: Recent progress and future prospects of 2D-based photodetectors. Adv. Mater. 30(51), 1801164 (2018) 2. Long, M., et al.: Progress, challenges, and opportunities for 2D material based photodetectors. Adv. Func. Mater. 29(19), 1803807 (2018) 3. Heersche, H.B., et al.: Bipolar supercurrent in graphene. Nature 446(7131), 56–59 (2007) 4. Novoselov, K.S., et al.: Electric field effect in atomically thin carbon films. Science 306(5696), 666–669 (2004) 5. Xia, F., Mueller, T., Lin, Y.M., Valdes-Garcia, A., Avouris, P.: Ultrafast graphene photodetector. Nat. Nanotechnol. 4(12), 839–843 (2009) 6. Mueller, T., Xia, F.N.A., Avouris, P.: Graphene photodetectors for high-speed optical communications. Nat. Photon. 4(5), 297–301 (2010) 7. Nair, R.R., et al.: Fine structure constant defines visual transparency of graphene. Science 320(5881), 1308 (2008)

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8. Zhu, W., Wei, X., Yan, F., et al.: Broadband polarized photodetector based on p-BP/n-ReS2 heterojunction. J. Semicond. 40(09), 092001 (2019) 9. Wang, Y., Zhu, L., Du, C.: Flexible difunctional (pressure and light) sensors based on ZnO nanowires/graphene heterostructures. Adv. Mater. Interfaces 7(6), 1901932 (2020) 10. Cheng, C., Yang, H., et al.: Performance enhancement of graphene photodetectors via in situ preparation of TiO2 on graphene channels. Adv. Mater. Technol. 4(3), 1800548 (2019) 11. Qin, S., Du, Q., Dong, R., Yan, X., Wang, F.: Robust, flexible and broadband photodetectors based on van der Waals graphene/C60 heterostructures. Carbon 167(15), 668–674 (2020) 12. Zhang, J., Huang, Y., Tan, Z., et al.: Low-temperature heteroepitaxy of 2D PbI2/Graphene for large-area flexible photodetectors. Adv. Mater. 30(36), 1803194 (2018) 13. Ye, M., Zhang, D., Yap, Y.: Recent advances in electronic and optoelectronic devices based on two-dimensional transition metal dichalcogenides. Electronics 6(2), 43 (2017) 14. Sahatiya, P., Gopalakrishnan, A., Badhulika, S.: Paper based large area Graphene/MoS2 visible light photodetector. In: 2017 IEEE 17th International Conference on Nanotechnology (IEEE-NANO), Pittsburgh, USA (2017) 15. Pataniya, P.M., Sumesh, C.K.: WS2 nanosheet/graphene heterostructures for paper-based flexible photodetectors. ACS Appl. Nano Mater. 3(7), 6935–6944 (2020) 16. Lee, Y.H., Song, I., Su, H.K., et al.: Perovskite granular wire photodetectors with ultrahigh photodetectivity. Adv. Mater. 32(32), 2002357 (2020) 17. Zheng, W., Lin, R., Zhang, Z., et al.: An ultrafast-temporally-responsive flexible photodetector with high sensitivity based on high-crystallinity organic–inorganic perovskite nanoflake. Nanoscale 9(34), 12718 (2017) 18. Lee, Y.H., Park, S., Won, Y., Mun, J., Ha, J.H., et al.: Flexible high-performance graphene hybrid photodetectors functionalized with gold nanostars and perovskites. NPG Asia Mater. 12(79), 2–12 (2020) 19. Li, J., Yuan, S., Tang, G., et al.: A high-performance, self-powered photodetector based on perovskite and graphene. ACS Appl. Mater. Interfaces 9(49), 42779–42787 (2017)

Research Progress on Novel Structures of Flexible Memristor Devices Huiling Zhang, Huiqing Zhao, Mengzhu Wang, Yingying Xiao, Dan Zhao, and Ruping Liu(B) School of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected]

Abstract. The explosive growth of information has brought tremendous impetus to the development of memory. Among all kinds of memories, due to simple structure, low energy consumption, and high miniaturization, memristor has attracted much attention, especially in the internet of things, artificial intelligence. By changing the applied voltage and current, the memristor can realize high/low resistance conversion to complete information storage. However, wearable devices put forward higher requirements for the mechanical properties of memristors. How to improve the flexibility of the memristor while ensuring the performance of the memristor is the focus of research. In order to address this question, in addition to using different materials to prepare the memristor, changing the structure of the memristor is also a very effective method. This paper summarized and discussed the structure of the flexible memristor, and described its latest configuration. In addition, this paper will also introduce the application of flexible memristors with different structures and its challenges and development direction. Keywords: Flexible memristor · Artificial bionic synapse · Memristor structure

1 Introduction The explosive growth of data information puts forward higher requirements on storage devices. Current storage devices cannot improve performance while reducing size, and traditional von Neumann-based computer systems have encountered bottlenecks. With a simple structure, good scalability, high-density storage, fast operating speed, low power consumption and high durability, the memristor is a promising storage device [1–3]. The electrical performance of the memristor matches the working principle of the nerve synapse. Thus, the memristor has been used to simulate the long/short-term synaptic plasticity of the nerve synapse (STP/LDP), the discharge time-dependent plasticity (STDP) and joint memory, etc. [4, 5]. It can create neural networks to realize perceptual operations. Therefore, preparing biomimetic artificial synaptic devices to imitate the information processing method of the human brain is a potential way to achieve efficient computing. However, wearable electronic equipment puts forward higher requirements on the mechanical performance of the device. The memristor as a key component in the © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 518–522, 2022. https://doi.org/10.1007/978-981-19-1673-1_77

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entire device will be developed in the direction of flexibility. Various new structures of memristors have been developed to improve their flexibility. It will become an essential unit in wearable electronic devices and artificial nerve synapse bionic devices in the future.

2 Flexible Memristor Structure 2.1 Flexible “Sandwich” Structure The “sandwich” structure memristor includes the top and bottom electrode layers and the middle dielectric layer (Fig. 1a). As the classic structure of the memristor, the “sandwich” structure memristor is simple and easy to prepared. The first working memristor is a “sandwich” structure memristor based on TiO2 prepared by HP Lab researchers in 2008 [6]. At present, researchers based on the classic “sandwich” structure prepared many new structures to improve the flexibility of the memristor. Yang et al. [7] based on polyurethane (TPU): silver nanoparticles and polydimethylsiloxane (PDMS) manufactured a stretchable corrugated memristor. Even the strain was as high as 60%, or after 300 cycles of 35% tensile strain, no performance degradation was observed. Moreover, they successfully simulated the synapse functions, including potentiation/depression characteristics, STP and LTP, “learningforgetting-relearning” behaviour, spike-rate-dependent, and spike-amplitude-dependent plasticity. In addition to changing the overall structure of the memristor, it is also possible to add structure to the dielectric layer to improve its mechanical properties. The TiO2 /HfO2 double-layer structure shows excellent characteristics, such as self-rectification, multiple resistance states, self-compliance and flexibility [8]. Zhang et al. [9] prepared a double-layer TiO2 /HfO2 structure flexible memristor on a polyethylene naphthalate (PEN) substrate. With a bending radius of 70 to 10 mm, the device still maintains its original performance. Interestingly, the performance degradation can be recovered after long-term stability testing. Adding a buffer layer between the electrode and the dielectric layer can not only improve the adhesion between them but also improve the flexibility and stability of the memristor. Dayanand Kumar et al. [10] used Al2 O3 on both sides of the ZnO to stabilize the local oxygen migration for filament formation and rupture. Even under 104 consecutive repeated flexible bends with a bending radius of 3 mm, the device still showed high mechanical stability and high durability. 2.2 Flexible Plane Structure The dielectric layer, upper and lower electrode layers are on the same plane in a planar memristor (Fig. 1b). With a planar structure, the phenomenon of the resistance change mechanism can be more intuitively observed [11]. When the two electrodes are the same material, the planar devices require fewer manufacturing steps and lead to lower costs and faster manufacturing processes. Georgii A. Illarionov et al. [12] used inkjet printing to deposit TiO2 nanoparticles in the nano-gold trench. However, due to incomplete

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trench filling, the device response was weak and the flexibility is poor, so the fabrication technology still needs to be further improved. Abunahla et al. [13] separated the gold electrodes by a gap containing a partially reduced graphite oxide (prGO) film, which was fabricated from an aqueous solution of GO by using standard microfabrication processes and prepared it on the cyclic olefin copolymer (COC) substrate. The device shows more than 20 different resistance states by applying continuous voltage sweeps. And the device can be operated on a flexible substrate to be used in flexible memory and Artificial Intelligence (AI). 2.3 Flexible Cross-Bar Structure The cross bar structure is composed of upper and lower electrodes crossing each other perpendicularly with the dielectric layer between them (Fig. 1c). It can realize largecapacity storage, as each node at the intersection is an effective logic storage unit. With high integration, high non-volatility, multiple logic functions, and good fault tolerance, the cross-bar memristor exhibits a great potential. Wang et al. [14] coated carbon fibers (Cf ) with Ba0.6 Sr0.4 TiO3 (BST) (BST@Cf ) and cross-stacked it on polyimide (PI) film to make a BST@Cf memristor. After being bent 3000 times, the memristor and was cycled successfully 1000 times and the on/off ratio reached a maximum of 106 . In addition, the device showed synaptic behavior of learning and forgetting processes and potential applications in wearable electronic devices. To greatly expand the cell density of memristive devices, three-dimensional (3D) stacking of storage devices provides a great method [15]. Chen et al. [16] prepared a 3D stacked flexible memristor based on parylene-C. The device exhibits excellent retention time (>105 s), endurance cycle (>300), and resistance on/off ratio (>10). In addition, when fabricated on a 10 µm parylene-carbon substrate, it shows excellent flexibility and transparency. Even under bending conditions (radius < 10 mm), it can still work well.

Fig. 1. Flexible memristor structure. (a) Flexible “sandwich” structure. (b) Flexible plane structure. (c) Flexible cross-bar structure

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3 Conclusions This article introduces the latest structure of flexible memristors. It can be seen that “sandwich” structure is no longer the only choice for flexible memristors. More and more new structure memristors are widely used. Table 1 summarizes the performance and application of some flexible memristors with different structures. Although the flexible memristor has a bright application prospect, there are still some problems to be solved. Table 2 shows the advantages and disadvantages of various structures of flexible memristor. How to improve the stability while ensuring flexibility is still a problem. With the development of science and technology, memristor structures with better performance will continue to be explored. In the future, flexible memristors will further increase storage capacity while reducing size and keeping stability and shine in wearable devices and artificial bionic synapses. Table 1. Performance and application of flexible memristor Flexible memristor

Memristor properties

Flexibility

Applications

Reference

ITO/TiO2 /HfO2 /Pt/PEN

Coefficients variations for high/low resistance state: ≈3.2%/≈3%

Withstand bending radius ranging from 70 to 10 mm

Wearable electronics

9

TiN/Al2 O3 /ZnO/Al2 O3 /TiN

ON/OFF ratio: >102 endurance: >104 cycles

Withstand Wearable bending memristor radius up to 3 mm

10

Au/prGO/Au

Over 20 different resistance states

Bendable and stretchable

AI inference application

12

Cu/TiO2 @C/PI

ON/OFF ratio: 105 endurance: over 1500 cycles

Flexible

Artificial synaptic

14

Table 2. Advantage and disadvantage of flexible memristor Flexible memristor

Advantage

Disadvantage

Flexible “Sandwich” memristor

Simple structure Simple preparation

Small-capacity storage

Flexible plane memristor

Lower costs Fast manufacturing processes

Small-capacity storage

Flexible cross-bar memristor

Large-capacity storage

Complex preparation

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Acknowledgement. This work was supported by the National Natural Science Foundation of China (61971049), the Key Scientific Research Project of Beijing Municipal Commission of Education (KZ202010015024), the Research and Development Program of Beijing Institute of Graphic Communication (Ec202006), the Beijing Municipal Science and Technology Commission (Z181100004418004).

References 1. Wang, W., Wang, M., Ambrosi, E.: Surface diffusion-limited lifetime of silver and copper nanofilaments in resistive switching devices. Nat. Commun. 10(1), 81 (2019) 2. Ielmini, D., Wong, H.S.P.: In-memory computing with resistive switching devices. Nat. Electron. 1, 333–343 (2018) 3. Sun, B.W., Qian, K., Wang, Q.P.: Research progress of flexible memristor. Micro Nano Electron. Intell. Manuf. 1, 76–86 (2019) 4. Chen, L., Zhou, W., Li, C., Huang, J.: Forgetting memristors and memristor bridge synapses with long- and short-term memories. Neurocomputing 456, 126–135 (2021) 5. Chen, L., He, Z., Li, C., Wen, S., Chen, Y.: Revisiting memristor properties. Int. J. Bifurc. Chaos 30, 2050172 (2020) 6. Strukov, D.B., Snider, G.S., Stewart, D.R.: Erratum: the missing memristor found. Nature 453, 80–83 (2018) 7. Yang, M., et al.: Stretchable and conformable synapse memristors for wearable and implantable electronics. Nanoscale 10, 18135–18144 (2018) 8. Ryu, J.H., Kim, S.: Artificial synaptic characteristics of TiO2/HfO2 memristor with selfrectifying switching for brain-inspired computing. Chaos Solitons Fractals 140, 110236 (2020) 9. Zhang, R., et al.: Role of oxygen vacancies at the TiO2 /HfO2 interface in flexible oxide-based resistive switching memory. Adv. Electron. Mater. 5, 1800833 (2019) 10. Kumar, D., Chand, U., Siang, L.W., Tseng, T.Y.: High-performance TiN/Al2 O3 /ZnO/Al2 O3 /TiN flexible RRAM device with high bending condition. IEEE Trans. Electron. Dev. 67, 493–498 (2020) 11. Sun, H., et al.: Direct observation of conversion between threshold switching and memory switching induced by conductive filament morphology. Adv. Func. Mater. 24, 5679–5696 (2014) 12. Illarionov, G.A., Kolchanov, D.S., Kuchur, O.A., Zhukov, M.V., Morozov, M.I.: Inkjet assisted fabrication of planar biocompatible memristors. RSC Adv. 9, 35998–36004 (2019) 13. Abunahla, H., Halawani, Y., Alazzam, A., Mohammad, B.: NeuroMem: analog graphenebased resistive memory for artificial neural networks. Sci. Rep. 10, 9473 (2020) 14. Wang, Z., et al.: Vacancy-induced resistive switching and synaptic behavior in flexible BST@Cf memristor crossbars. Ceram. Int. 6(13), 21569–21577 (2020) 15. Mountain, D.J., Mclean, M.M., Krieger, C.D.: Memristor crossbar tiles in a flexible, general purpose neural processor. IEEE J. Emerg. Sel. Top. Circ. Syst. 8, 137–145 (2017) 16. Chen, Q., Wang, Z., Lin, M., Qi, X., Huang, R.: Homogeneous 3D vertical integration of parylene-C based organic flexible resistive memory on standard CMOS platform. Adv. Electron. Mater. 7(2), 2000864 (2020)

Research Progress of Glucose Sensor Suitable for 3D Printing Kun Hu1,2(B) , Linxinzheng Guo1 , Haibo Wang1 , Jundong Wang1 , Weiwei Sun1 , and Kunlan Wang1 1 Beijing Engineering Research Center of Printed Electronics, Institute of Printing and Packaging Engineering, Beijing Institute of Graphic Communication, Beijing, China [email protected] 2 College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian, China

Abstract. Diabetes is a series of metabolic disorders, such as sugar, protein, fat, water and electrolytes. It is caused by a variety of pathogenic factors, such as genetic factors, immune disorders, microbial infections and toxins, leading to pancreatic islet dysfunction and insulin resistance. At present, drug intake and real-time blood glucose monitoring are the main methods for diabetic patients to treat diabetes. At present, there are three methods for detecting blood glucose concentration: color method, sensor method and fluorescence calibration method. Each of these three methods has its advantages. Among them, the glucose sensor has the advantages of simple instrument, high selectivity and sensitivity, fast detection speed, and convenient use. In the past ten years, electrochemical glucose sensors have made great progress. The glucose electrochemical sensor uses the glucose oxidase fixed on the surface of the working electrode to carry out the Redox reaction with the glucose in the tissue fluid. The glucose concentration is obtained by measuring its electrical signal through a certain algorithm. This article reviews the development of glucose sensors in recent years, the selection of glucose sensor materials in recent years, the preparation technology of materials, and the development prospects of glucose sensors. Keywords: Glucose sensor · Glucose oxidase · Enzyme immobilization

1 Introduction Diabetes is a worldwide refractory disease that accompanies a lifetime. As of 2019, there are more than 97 million people with diabetes in China, and about 150 million people have pre-diabetes. The prevalence of diabetes in men over the age of 20 in China is 10.6% and 8.8% respectively, and the total prevalence is 9.7%. The normal blood glucose concentration ranges from 3.8 to 6.1 mmol/L. Blood glucose level is the basic indicator for diagnosing diabetes. At present, there are three methods for detecting blood glucose concentration: color method, sensor method and fluorescence calibration method. Each of these three methods has its advantages. Among them, the glucose sensor has the advantages of simple instrument, high selectivity and sensitivity, fast detection speed, and convenient use. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 P. Zhao et al. (Eds.): Interdisciplinary Research for Printing and Packaging, LNEE 896, pp. 523–529, 2022. https://doi.org/10.1007/978-981-19-1673-1_78

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In the past ten years, electrochemical glucose sensors have made great progress. The glucose electrochemical sensor uses the glucose oxidase (GOD) fixed on the surface of the working electrode to undergo redox reaction with the glucose in the tissue fluid, and obtains the glucose concentration by measuring its electrical signal through a certain algorithm [1]. This study summarizes the development of glucose sensors in recent years, the selection of glucose sensor materials in recent years, material preparation technology and prospects [2].

2 Application Principle of Glucose Sensor Since 1962, Clark and Lyons proposed the first-generation glucose sensor for the first time [3]. Later, in 1967, Updike and Hicks first developed a glucose oxidase (GOD) electrode based on platinum electrodes, which immobilized glucose oxidase in a gel and used it to quantitatively detect the glucose content in serum. In 1972, Guillbault and Montalvo prepared a urea sensor by immobilizing urease on an ammonia electrode, and proposed the use of a potentiometric glucose enzyme sensor. In 1973, Nilsson et al. developed the first potential type trypsin sensor. Subsequently, in the past 60 years, glucose sensors around the world have made tremendous progress, from invasive to wearable, from measuring blood to measuring saliva, sweat, etc., and made great progress [4]. According to different reaction mechanisms, glucose sensors can be divided into three generations. GOx -based third-generation sensors use engineered enzymes with modified structures to facilitate direct electron exchange between the electrode and the embedded enzyme [5]. In the third-generation glucose sensor, it can not only avoid the oxygen limitation of the first-generation sensor, but also avoid the problems caused by the penetration of electronic media and the competition with oxygen in the second-generation sensor. In this sensor, the enzyme is directly fixed on the surface of the working electrode, so that the active center of the enzyme is close to the surface of the electrode. The direct electron transfer between the enzyme and the working electrode is easy to carry out, successfully avoiding the interference of previous sensors. Therefore, the third-generation glucose sensor has a faster response speed. Higher sensitivity and better anti-interference ability [6]. For this type of sensor electrode, the electron exchange rate depends on the electrode material, the interface characteristics of the electrode and the electrolyte, and the characteristics of the enzyme. However, it is clear that the electrochemical detection of by-products is still the basis of glucose sensors. Most commercial sensors and related research rely on the first and second-generation GOx technologies, and the demand for oxygen supply has been solved by a semi-permeable membrane that is easy and inexpensive to manufacture. However, there is a strong need for advanced sensor design that can effectively detect glucose without oxygen, selectivity and energy [7].

3 Graphene Glucose Sensor In recent years, as a new type of material, graphene has received widespread attention due to its good physical and chemical properties [8]. At present, graphene is widely

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used in sensors, biological materials, conductive inks, energy storage materials, lithium batteries, semiconductor materials and other fields. According to research, graphene can effectively promote the redox reaction process near the electrode due to its fast electron transfer ability [9]. Direct electron transfer from graphene to glucose oxidase has also been discovered. Therefore, as a sensitive material, graphene has certain application potential in glucose sensors. Liu Kunlin et al. prepared graphene flexible temperature sensor films based on the conductivity of graphene based on continuous medium penetration, simple operation and low screen printing cost [10]. The conductive graphene film is made of graphene conductive ink screen printing. After high temperature treatment, the conductivity is significantly improved.. The linearity of the flexible temperature sensor is 0.971, and the temperature coefficient of resistance is 0.388%/°C. Placed at 20 °C, 40 °C and 60 °C for 1 h, the relative change rate of resistance is 0.05%–0.08%; the response time is about 5 s; it is almost not affected by deformation, but the sensor cannot be normal in a high humidity environment Work. This problem can be solved by wrapping a layer of flexible material on the surface. Nanographene has a good three-dimensional structure, a large specific surface area, a high glucose oxidase load, and a stable structure. At the same time, 3D graphene, as a kind of multilayer graphene, is the first choice for the preparation of glucose sensors due to its good conductivity and stable electrical properties [11]. Sun Tai and others from Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences developed a glucose sensor based on a 3D graphene electrode diagram, using PET as a flexible substrate, and the working electrode layer is composed of 3D graphene and an enzyme film layer., Including the enzyme membrane coating composed of glucose oxidase, chitosan solution and glutaraldehyde solution. The sensor has the advantages of economy, environmental protection, simplicity, high efficiency, controllable quality, etc., and overcomes the shortcomings of the existing glucose sensor. In addition, the glucose sensor made of three-dimensional graphene has the advantages of high sensitivity, accurate measurement, strong biocompatibility, and high stability.

4 Glucose Sensor with Zinc Oxide Modified Electrode Zno has significant sensing surface, chemical stability, wide direct band gap, high excitation binding energy, high refractive index, high electron mobility, low toxicity, piezoelectricity and UV protection. Zinc oxide has good biocompatibility, and its high electric point (IEP) is about 9.5 [12, 13]. Zinc oxide, a protein suitable for electrostatic adsorption at low electrical points, is relatively stable at physiological pH, so it is suitable for in vivo application [14]. Because ZnO has good piezoelectric properties, a two-step wet chemical method was used to prepare ZnO nanorods with uniform morphology, consistent orientation, and controllable aspect ratio on a conductive glass substrate [15]. Fan Jinze et al. deposited Pt nanoparticles on ZnO nanotubes using titanium as a substrate, and prepared a new type of enzyme-free glucose sensor by electrochemical methods [16]. The linear range of Pt-Zno/Ti modified electrode is 1 × 10–5 –1 × 10–2 mol/L, the response time is less than 4s, and the repeatability is good.

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Jing Weixuan et al. manually wound gold wires on the core in a spiral manner, synthesized ZnO nanowires on the spiral by a water bath method, and physically adsorbed glucose oxidase (GOD) on the ZnO nanowires to prepare a glucose sensor working electrode [17]. The sensitivity of the sensor is (1.410 ± 0.665) µA·L/(mmol·cm2 ), the linear range is 0–(4.292 ± 0.652) mmol/L, the Michaelis constant is (3.571 ± 1.280) mmol/L, and the detection limit is (14.085 ± 8.393) µmol/L. With the dynamic increase of GOD, a spiral-type linear cross-scaled glucose sensor with better performance can be obtained. Zinc oxide nanostructures have shown great potential in biosensors as enzyme carriers. High-performance ZnO nanostructured enzyme biosensor: 1) Controlled synthesis of ZnO with different morphologies has a larger specific surface area. The larger the specific surface area, the higher the sensitivity of the glucose sensor. 2) ZnO nanostructures with high IEPs promote the electrostatic adsorption of enzymes. Their biocompatibility also provides a good microenvironment for maintaining enzyme activity. 3) The high crystallinity ZnO nanostructure can provide a direct electron conduction channel between the active center of the enzyme and the electrode surface without the need for a medium [14].

5 Immobilization of Glucose Oxidase In recent years, with the continuous exploration of researchers, in order to improve the stability of glucose oxidase, facilitate the separation of products, reduce costs, and simplify operations, enzyme immobilization methods have gradually been enriched. Mainly include adsorption method, embedding method, cross-linking method and so on. The cross-linking method refers to the use of a cross-linking agent to form covalent crosslinks between the same enzyme or multiple enzyme molecules. Adding a cross-linking agent can link the enzyme molecules to form a network cross-linked structure between the enzyme molecules and the cross-linking agent, so that the originally dispersed enzyme molecules can gather together to form an enzyme or a multi-enzyme complex. Commonly used functional crosslinking agents are glutaraldehyde, dicarboxylic acid and dimethyl adipate. The advantage of the cross-linking method is that it does not require carrier connection and is simple to operate. However, excessive cross-linking will cause the active center of the enzyme to appear shadow during the aggregation process, thereby reducing the mechanical properties of the enzyme complex [18]. Xu et al. used multi-walled carbon nanotubes to accelerate the immobilized electron transfer between horseradish peroxidase and electrode, which is a glassy carbon electrode modified by horseradish peroxidase and glucose oxidase on multi-walled carbon nanotubes Connected from above [19]. The double enzyme is cross-linked with multiwalled carbon nanotubes through glutaraldehyde and bovine serum albumin, and the glucose sensor is sensitive to a glucose concentration of 0.4–1 mmol. The sensor has good selectivity and durability, and has a long-term relative standard deviation 5%. The recovery rate of glucose-added human serum samples is between 96% and 101%. Mesoporous material, a porous material with a pore diameter between 2–50 nm. Mesoporous materials have the characteristics of high specific surface area, regular and ordered pore structure, narrow pore size distribution and continuously adjustable pore size. In addition, the ordered channels of this material can be used as a “microreactor”.

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Li et al. prepared a high-sensitivity glucose biosensor, which is made of a composite material made of mesoporous hydroxyapatite and mesoporous titanium dioxide, and then ultrasonically mixed with multi-walled carbon nanotubes to form a rough nanocomposite film [20]. The mesoporous titanium dioxide particles prepared by the author are spherical, with a particle size of about 20–50 nm, and the particles are interconnected to form a mesoporous framework. Multi-walled carbon nanotubes surround hydroxyapatite nanotubes and titanium dioxide nanoparticles, and the mesoporous hydroxyapatite/mesoporous titanium dioxide/multi-walled carbon nanotube film has a rough surface and a three-dimensional network structure, and the pore size is about 30 nm. This structure can increase the effective surface area of the GOx load and effective substrate diffusion, which is beneficial to improve the response performance of the glucose sensor. Glucose oxidase is immobilized on the membrane of the electrode. The sensor has good electrocatalytic activity for glucose oxidation. At 0.3 V and pH = 6.8, the sensitivity of the sensor is 57 µA·M·cm2 . When the signal-to-noise ratio is 3, the linear dynamic range is 0.01–15.2 mm, the correlation coefficient is 0.9985, and the detection limit is 2 µm. Uric acid, ascorbic acid, dopamine and most carbohydrates did not interfere. Wang et al. synthesized dendritic mesoporous silica nanoparticles using triethylamine as an alkali source, and synthesized amino-modified dendritic mesoporous silica nanoparticles using 3-aminopropyltriethoxysilane.To fix glucose oxidase [21]. The diameter of the immobilized GOD is about 200 nm and the shape is uniform. Under the optimal fixation conditions, the protein load was 225 mg/g and the enzyme activity was 215 U/mg. The lowest detection limit of immobilized GOD for glucose detection is 0.0014 mg/mL. This method is simple to operate and has high accuracy, improves the pH stability, thermal stability and reusability of the enzyme, and reduces the detection cost. When testing serum samples, more than 80% of the activity is still present after 36 times of repeated use. The pore size of ordered mesoporous materials can be continuously adjusted in the range of 2–50 nm, and the characteristics of non-physiological toxicity make it very suitable for immobilizing and separating enzymes, proteins, and Solidify the enzyme, and can inhibit the leakage of the enzyme. This immobilization method can maintain the activity of the enzyme well.

6 3D Printed Glucose Sensor In recent years, 3D printing technology, also known as additive manufacturing, has received great attention due to its ability to produce complex three-dimensional prototypes and equipment quickly and at low cost. This technology is providing a large number of applications in different fields, such as healthcare, biomedicine, pharmaceuticals, engineering, chemistry, and electrochemistry. Numerous applications in the electrochemical field have made technological progress in the development of equipment from energy storage, energy conversion to sensors. Using 3D printing technology to prepare glucose sensors, there are few reports in this direction, and this field has broad prospects. Raquel G. et al. prepared a new conductive composite wire based on graphene/polylactic acid (G-PLA) matrix with nickel hydroxide particles introduced

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into it, and its filaments have extremely low electrical conductivity. Three-dimensional printed electrodes using new conductive filaments are used to prepare low-cost nonenzymatic sensors. The new 3D printed disposable electrode is used for the selective detection of glucose (without enzyme sensor), the detection limit is 2.4 mmol/L, and it is not interfered by ascorbic acid, urea and uric acid. The sensor is assembled in a portable electrochemical system, which can realize rapid identification, 160 times per hour, and the relative standard deviation is