Inaba Yoshimi, Yanagisawa Takayuki
Toppan Technical Research Institute, TOPPAN Holdings Inc., Sugito, Saitama, 345-8508, Japan.
Sci Rep. 2024 Mar 26;14(1):7102. doi: 10.1038/s41598-024-57851-z.
Forming large pitch and depth patterns spontaneously based on a bottom-up approach is a challenging task but with great industrial value. It is possible to spontaneously form an uneven (concave-convex) patterns with submillimeter-to-millimeter-scale pitches and depths by the direct pattern exposure of a UV-curable oil-in-water (O/W) emulsion liquid film. UV irradiation generates a latent pattern of a cured particle aggregation in the liquid film, and an uneven structure is spontaneously formed during the subsequent drying process. This process does not require any printing and embossing plates or development process. In this report, we presented an example of unevenness formation with a maximum pattern depth of approximately 0.4 mm and a maximum pitch width of 5 mm. The patterns formed by this method have raised edges in the exposed areas and fogging in unexposed areas. The pattern shapes become conspicuous under overexposure conditions, but the formation mechanism has not yet been understood in detail and needs to be investigated. In this study, we focused on the exposure process and clarified the mechanism of pattern formation by analyzing the dynamics of emulsion droplets in the medium by an in situ microscopy observation method. As a result, we found that the fogging was mainly caused by light leakage from the exposed area, and the raised pattern edges were caused by droplets transported from the unexposed area to the exposed area. Furthermore, the convection caused by the heat generated from polymerization is a determining factor affecting all these phenomena. By controlling the pattern shape related to convection utilizing direct projection exposure, we showed an example of eliminating raised pattern edges with a height difference of approximately 0.1 mm. By devising and selecting exposure methods, we can expand the range of design applications such as interior decorative patterns.
基于自下而上的方法自发形成大间距和深度的图案是一项具有挑战性但具有巨大工业价值的任务。通过对紫外线可固化的水包油（O/W）乳液液膜进行直接图案曝光，可以自发形成具有亚毫米到毫米尺度间距和深度的不均匀（凹凸）图案。紫外线照射在液膜中产生固化颗粒聚集的潜像图案，并且在随后的干燥过程中自发形成不均匀结构。该过程不需要任何印刷和压花板或显影过程。在本报告中，我们展示了一个不均匀性形成的例子，其最大图案深度约为0.4毫米，最大间距宽度为5毫米。通过这种方法形成的图案在曝光区域有凸起边缘，在未曝光区域有雾化现象。在过度曝光条件下图案形状变得明显，但形成机制尚未得到详细理解，需要进行研究。在本研究中，我们聚焦于曝光过程，通过原位显微镜观察方法分析介质中乳液液滴的动力学，阐明了图案形成的机制。结果，我们发现雾化主要是由曝光区域的光泄漏引起的，而凸起的图案边缘是由从未曝光区域传输到曝光区域的液滴引起的。此外，聚合产生的热量引起的对流是影响所有这些现象的决定性因素。通过利用直接投影曝光控制与对流相关的图案形状，我们展示了一个消除高度差约为0.1毫米的凸起图案边缘的例子。通过设计和选择曝光方法，我们可以扩大诸如室内装饰图案等设计应用的范围。
