柔性透明电极卷对卷压印成形的尺度效应与工艺规律研究

Metal mesh with the linewidth of 1～10 μm on the surface of polymer film is a promising candidate to replace the conventional ITO to make the transparent electrodes flexible, low sheet resistance and high transparency. The traditional lithograhpy method has complicated process and laser sintering nano-silver process has low effency. Roll to roll imprinting process is a novel approach for the continuous fabrication of large-area metal mesh. However, this process still has the defects of nonuniform linewith or even line fracture for metal mesh. The main reason is that the current process design theory is diffult to instruct the control of flow filling and shrinkage distortion of nano silver paste in micro-cavities..This proposal will investigate the size effect mechanism during the filling process and shrinkage behavior during the curing process. A constitutive model of nano silver paste considering size effect and a shrinkage model for curing process will be established, respectively. Afterwards, a simulation model of roll to roll imprinting process for flexible transparent electrodes will also be set up to reveal the mechanism of nonuniform linewith and line fracture. The influence of process parameters to the quality of metal mesh structure will be studied and a new process design method will therefore be established. A series of experiments will be conducted based on the roll to roll UV imprinting machine to verify the accuracy of simulation model and a prototype of flexible transparent electrodes with metal mesh will be fabricated. This proposal will provide the basic process theory and technology support for the high efficiency and high accuracy fabrication of transparent electrodes for flexible electronics.

聚合物薄膜表面1～10微米线宽的金属网格（Metal Mesh）有望替代传统ITO实现透明电极的柔性化、低电阻和高透光率。目前的黄光制程工序复杂、激光烧结纳米银工艺效率低，卷对卷压印成形是实现金属网格大面积连续加工的创新工艺。然而，卷对卷压印成形过程中易于产生线宽不均匀、银线断裂等缺陷，主要原因在于传统的成形工艺设计理论难以指导纳米银浆在微细膜腔中流动充型和收缩变形的控制。.本项目研究纳米银浆在微细膜腔中流动充型的尺度效应机制和固化收缩行为，建立考虑尺度效应的纳米银浆流动本构模型和银线固化收缩模型；进而建立金属网格卷对卷压印成形工艺仿真分析模型，揭示银线线宽不均匀和断裂缺陷的产生机理；研究工艺参数对网格质量的影响规律，形成金属网格卷对卷压印成形工艺设计新方法；通过金属网格卷对卷压印成形实验进行验证，制备柔性透明电极实验原型，为大面积柔性透明电极的高效高精度制造提供工艺基础理论和技术支撑。

本项目围绕柔性透明电极制备过程中透过率低及导电性差等问题开展深入研究，考虑到微纳结构对成型的影响，基于物理机制建立了粗糙表面边界滑移模型，并用于指导微纳结构的成型精度控制，同时构建了有利于大面积制备的卷对卷紫外纳米压印工艺平台，为大面积、高透过率、高导电性的柔性透明电极制备提供了理论与技术基础。.项目承担单位上海交通大学严格执行项目计划，在以下方面取得进展：（1）基于原子力显微镜进行边界滑移实验研究，分析了表面粗糙度对边界滑移影响规律，阐述了表面粗糙度影响边界滑移的微观机理；（2）基于实验结果和粗糙度影响微观机理，在理想表面边界滑移模型基础上考虑流体特性、润湿性、粗糙度等界面物性参数对边界滑移的影响，建立了粗糙表面边界滑移模型；（3）通过结构优化设计了金属网格图案，制备了透明电极的模具并避免莫瑞干涉效应。同时针对柔性透明电极的透光率相对较低问题，利用仿生原理实现了柔性透明电极复合蛾眼结构的制备，改善透明电极的透过率；（4）面向柔性透明电极的低成本、高效率、高精度制备需求，结合卷对卷工艺开发了卷对卷紫外压印实验平台和平板式刮涂平台，制备出高透过率且高导电性的柔性透明电极实验原型。.在该项目的支持下，共发表SCI论文12篇，授权发明专利7项，撰写英文专著1章节。获2019年度上海市技术发明特等奖（项目负责人排名第5），入选2020年度教育部青年长江学者，第20届全国青年岗位能手，2019年度上海市青年科技启明星，2019年度上海市青年拔尖人才等。