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Control of Liquid Crystal Alignment Based on 3-Dimensional Molecular Manipulation

基于三维分子操纵的液晶取向控制

基本信息

批准号：
12555242
负责人：
IKEDA Tomiki
金额：
$ 8.26万
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：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

Uniform alignment of liquid crystals (LCs) is indispensable for their optical and optpelectronic applications, which is conventionally obtained by mechanically rubbing a polyimide (PI) layer. However, dust particles and static surface charges are produced by the rubbing process, which would cause electrical and mechanical damage to thin film transistors. In recent years, the technique for unidirectional alignment of LCs caused by PI films exposed to linearly polarized UV (LPUV) light has been developed. this method allows for easy control of the alignment direction and the fast preparation of an alignment layer, and causes little dust particles and electrostatic damage. In this case, the alignment of LC is perpendicular to the polarization of LPUV light, and exposure should be made two times in order to give precise pretilt of LCs. In this project , we developed a novel method to induce a parallel alignment of LC to polarization of LPUV light by irradiating during the thermal treatment process. Polyamic-acid-coated ITO glass substrate was irradiated with LPUV light at 8.5 mW/cm^2 during the thermal imidization process. The irradiation time was about 30 min and the thermal treatment was processed from 100 to 250 ℃ at a heating rate of 5 ℃/mm. After irradiation, the substrate was then imidized for 10 min at 250 ℃. LC cells with a gap of 5 μm were constructed using two pieces of the above substrates with parallel polarization axes. 4'-Pentyl-4-cyanobiphenyl (5CB) doped with 0.3 wt% dichroic dye M-137 (λmax = 639 nm) was filled into the cells in an isotropic phase at 75 ℃ and cooled down to room temperature. By polarizing microscopy and polarized UV spectra, it was found that the LC molecules were aligned uniaxially and uniformly.

液晶（lc）的均匀排列对于其光学和光电应用是必不可少的，这通常是通过机械摩擦聚酰亚胺（PI）层来获得的。然而，摩擦过程会产生灰尘颗粒和静态表面电荷，这会对薄膜晶体管造成电气和机械损伤。近年来，在线偏振紫外光（LPUV）光照射下，研究了PI薄膜对LCs的单向对准技术。这种方法可以很容易地控制对准方向和快速制备对准层，并且产生很少的灰尘颗粒和静电损坏。在这种情况下，LC的对准方向与LPUV光的偏振方向垂直，为了得到精确的LC预倾斜，需要进行两次曝光。在本项目中，我们开发了一种新的方法，通过在热处理过程中辐照来诱导LC与LPUV光的偏振平行对准。在热亚酰化过程中，用8.5 mW/cm^2的LPUV光照射聚酰胺酸涂层ITO玻璃基板。辐照时间约为30 min，热处理温度为100 ~ 250℃，升温速率为5℃/mm。辐照后，底物在250℃下咪化10 min。利用两片平行极化轴的衬底构建了间隙为5 μm的LC电池。将掺杂0.3 wt%二色性染料M-137 （λmax = 639 nm）的4′-戊基-4-氰联苯（4′-Pentyl-4-cyanobiphenyl, 5CB）在75℃下以各向同性相填充到细胞中，冷却至室温。通过偏光显微镜和偏振紫外光谱分析，发现LC分子呈单轴均匀排列。