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Liquid Crystal Alignment Induced by Polyimides Exposed to Linearly Polarized Light

聚酰亚胺暴露于线偏振光诱导的液晶取向

基本信息

批准号：
10555301
负责人：
IKEDA Tomiki
金额：
$ 7.68万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10555301/
关键词：
Polyimide Alignment Layer Polarized Light Liquid Crystals Photoinduced Alignment Non-Rubbing Alignment 光駆動

项目摘要

Through this study on photoalignment (non-robbing alignment) technique for liquid crystal (LC) devices, we have revealed that aromatic polyimides (Pis) exposed to linearly polarized UV light (366 nm) show a high alignment efficiency without significant change in the chemical structure of PIs. We extended the PI films as an alignment layer to dynamic control technique of nematic LCs (NICs). The most significant characteristic of this system is to utilize photoinduced Freedericksz transition as a trigger to control alignment of NICs. We realized the optical switching of with the photosensitive PIs containing benzophenone moiety as an alignment film. It became clear that the threshold voltage of Freedericksz transition, at which change in the LC alignment occurs, is quite different between irradiated and unitradiated conditions. It was found that photoirradiation at 366 nm resulted in the immediate change in the transmittance when bias voltage of 4.5 V was applied across the cell. Although the mechanism is not well understood at the present stage, formation of intra- or intermolecular charge transfer complexes in the surface area of PI films by photoirradiation ( i.e., change in the polarity) seems to participate in the phenomenon. In conclusion, we have shown for the first time that the photosensitive PI films enable optical control of Freedericksz transition of NLCs. This phenomenon is useful for development of polarization-controllable materials in which permanent electric polarization is controlled by change in dipolar alignment based on Freedericksz transition.

通过对液晶（LC）器件光配向（非抢配向）技术的研究，我们发现，暴露于线偏振紫外光（366 nm）的芳香族聚酰亚胺（Pi）表现出高配向效率，且PI的化学结构没有显着变化。我们将 PI 薄膜作为取向层扩展到向列液晶 (NIC) 的动态控制技术。该系统最显着的特点是利用光诱导的 Freedericksz 跃迁作为触发器来控制 NIC 的对齐。我们以含有二苯甲酮部分的光敏PI作为配向膜实现了光学开关。很明显，Freedericksz 转变的阈值电压（LC 排列发生变化）在辐照条件和未辐照条件下有很大不同。结果发现，当在电池上施加 4.5 V 的偏压时，366 nm 的光照射会导致透射率立即发生变化。尽管目前阶段尚不清楚其机制，但通过光照射（即极性的变化）在 PI 薄膜表面区域形成分子内或分子间电荷转移复合物似乎参与了这一现象。总之，我们首次证明光敏 PI 薄膜能够对 NLC 的 Freedericksz 跃迁进行光学控制。这种现象对于开发偏振可控材料很有用，其中永久电极化是通过基于弗里德里克斯跃迁的偶极排列的变化来控制的。