以液晶單體直接光聚合反應製備光學異方性薄膜

Abstract

本研究合成兩系列新型含雙環氧乙院之液晶化合物，兩系列雙環氧乙院液晶化合物分別含有反式環己二羰酸二苯酯或具氟側取代基之反式環乙二羰酸二苯酯液晶基，所合成之液晶單體，都具有向列型液晶相，研究結果顯示，導入氟側取代基會使所合成單體，液晶溫度範圍變窄，而且變成只具有單變型之向列型液晶相。本研究也合成數種含4—氰基聯苯或4—戊院環己羰酸聯苯酯之環氧乙烷及丙烯酸酯單體，這些單體化合物皆呈現向列液晶相，可以作為調配向列液晶混合物用。 本研究第二部份係將所合成之液晶單體或混合物排列在兩片玻璃中間形成扭轉90度向列型排列，再經照光聚合製備出透明的光學異方性高分子薄膜，所形成之高分子薄膜具有相當大的雙折射率及波長相依折射率值，這些高分子薄膜可以作為扭轉向列液晶顯示器視角補償膜。研究結果顯示所製備之光學異方性薄膜，其中與扭轉向列液晶顯示器有最相似之雙折射率及波長相關雙折射率值者，其對扭轉向列行液晶顯示器有最佳之視角補償效果。

Two series of new liquid crystal (LC) diepoxides are synthesized and characterized. Both series of diepoxides contain either a diphenyl trans-cyclohexane dicarboxylated moiety or a lateral fluoro-substituted diphenyl trans-cyclohexane dicarboxylate moiety as mesogens. All LC monomers showe respectively a nematic phase. The results demonstrate that introducing a lateral fluoro-substituent into the mesogens will decrease the temperature range of the nematic phase and the obtained LC monomers show why a monotropic nematic phase. Furthermore, several LC epoxides and acrylates containing ether a cyanobiphenyl or a biphenyl 4-pentyl cyclohexane carboxylate mesogen are also synthesized. The synthesized monomers which show a nematic phase, are used to formulate LC mixtures. In the second part of the this study, the LC monomers or mixtures are oriented in 90 degrees twist way between two glass substrates. During photopolymerization, the ordering of the LC molecules was fixed, yielding a optically anisotropic LC networks. The clean LC networks show very large birefrigence and birefrigence dispersion. The results demostrate that a films for a TN-LCD. The results demonstrate that a film which shows very similar △n and △n dispersion as the TN-LCD cell, reveal the best viewing angle improment for the TN-LCD.