银纳米线墨水的流平流变学机制及其在高均匀电极可控制备中的应用基础研究

Silver-nanowire transparent electrode is a key basic component in the field of flexible electronics. However, its application is still restricted by the preparation of highly uniform silver-nanowire transparent electrode. The leveling process of ink is crucial for preparing highly uniform electrode. However, the influence of different factors on the leveling process of silver-nanowire ink is still unclear at present and for this reason, it's difficult to control the leveling process of silver-nanowire ink effectively. To solve this problem, based on previous studies, this project plans to study the influence of different factors on the flatness of the wet film at different periods (the earlier stage, the middle and later periods) of leveling respectively. Then, the mathematic relationships (curves and empirical formulae) between the flatness of the wet film and these factors will be established. From these relationships, the rheological behaviors of silver nanowire ink at different periods (the earlier stage, the middle and later periods) will be revealed. Finally, integrated leveling rheological mechanism of silver nanowire ink will be obtained. This mechanism possesses a certain degree of universality and can provide theoretical reference for the preparation of solution-processed uniform films of various materials. In this project, three aspects are mainly focused on: 1. the influences (single and synergy) of seven factors (including the surface tension of the ink and substrate, the ink viscosity, etc) on the flatness of the wet film will be studied quantificationally; 2. the influences (single and synergy) of ten factors (including the destruction site, the surface tension of the ink, etc) on the flatness of the wet film will be studied quantificationally; 3. under the guidance of the systematic mechanism refined from above studies, silver nanowire-PET transparent electrode with high uniformity will be prepared to verify the correctness of above mechanism.

银纳米线透明电极是柔性电子领域的关键部件，但高均匀银纳米线透明电极的制备仍是制约其应用的一大瓶颈。墨水流平是制备高均匀电极的关键，但目前不同因素对银纳米线墨水流平的影响规律尚不明确，这导致银纳米线墨水流平难以被有效调控。针对该问题，本项目拟在前期研究基础上，分别定量研究流平前期和中后期不同因素对湿膜平整度的影响，建立湿膜平整度与影响因素的曲线和经验公式关系，揭示流平前期和中后期银纳米线墨水的流变学行为，最终获得完整的银纳米线墨水流平流变学机制模型。该模型具有一定普适性，能为湿法制备各种材料的均匀薄膜提供理论参考。具体研究包括：1、定量研究流平前期墨水/基底表面张力、墨水粘度等七因素对湿膜平整度的单一和协同影响规律；2、定量研究流平中后期湿膜破坏位点、墨水表面张力等十因素对湿膜平整度的单一和协同影响规律；3、综上研究，形成系统理论，并基于此制备高均匀银纳米线-PET透明电极，印证理论正确性。

项目在银纳米线墨水前期/中后期流平流变学机制、银纳米线墨水分散/消泡/干燥/分布动力学、商用墨水和大尺寸高均匀薄膜制备技术开发、银纳米线稳定性等方面开展了系列研究。主要开展的工作如下：1、墨水前期流平研究方面，完成了适用于金属纳米线墨水的增稠剂的筛选，研究了墨水表面张力、粘度对墨水前期流平的影响规律，从墨水浸润、铺展、干燥几方面揭示了粘度提升墨水流平效果的机理，查明了粘度与银纳米线分散性、涂膜工艺之间的关系，阐明了墨水粘度、增稠剂对薄膜导电性、均匀性、透过率、附着力的具体影响。2、墨水中后期流平研究方面，探究了湿膜破坏阶段破坏点位置、破坏力大小、溶解度、破坏点数量对墨水中后期流平的影响并揭示了相应的作用机理，阐明了墨水再流动阶段粘度对中后期流平的影响。3、提出了全小分子液体助剂的新墨水设计理念，研究了银纳米线墨水的分散、消泡、干燥、分布动力学，揭示了相应设计、助剂的作用机理，查明了最佳助剂种类/含量、后处理温度等。4、通过前面研究建立了较完整的银纳米线墨水动力学模型，基于模型开发了商用银纳米线墨水和大尺寸高均匀柔性透明电极制备技术，制备的0.6米宽、30米长的大尺寸柔性电极方阻46.1Ω/sq、可见光区透过率87%以上、雾度1.39%、方阻分布不均匀度3.62%，指标满足应用要求，用其开发的32英寸大尺寸柔性触控屏性能良好。5、项目开发的墨水配方和薄膜技术分别转让给了重庆柔纳科技有限公司、苏州三百亿科技有限公司和上海巨尔希电子科技有限公司，其中重庆柔纳科技有限公司已利用相关技术实现产值几千万元。6、提出了隧穿焊接法来解决绝缘高分子壳层导致银纳米线不导电的问题，使一直包裹高分子从而提升纳米线稳定性的方法变为可行，研究了银纳米线电极和银@PVP核壳纳米线电极的焊接并总结了普遍的焊接规则，查明了高分子壳层的引入对银纳米线性能的影响。上述银纳米线墨水动力学模型具有一定普适性，能为湿法制备各种材料的均匀薄膜提供理论参考。