以光聚合碟狀液晶單體製備異向性高分子薄膜

Abstract

本研究首先合成兩個系列之新型含triphenylene團基之碟狀液晶單體，第一系列單體是在周邊苯環上導入氟側取代基，第二系列單體則是將銜接周邊苯環與柔軟烷鏈之連接基改為酯基。第一系列合成之液晶單體，除了含最短的柔軟烷鏈之單體沒有液晶相外，其餘的皆呈現柱狀型碟狀液晶相（Drd），研究結果顯示，導入氟側取代基會造成均向點溫度升高，且大部份之液晶單體在均向點之前就分解了；當柔軟烷鏈愈長時，所合成單體熔點愈低。而以酯基為連接基之液晶單體，均向點溫度則下降許多，且形成六角柱型碟狀液晶相（Dhd）。 本研究第二部份係將所合成的液晶單體與含雙環氧乙烷之非液晶化合物，以不同比例混合，灌入已經表面處理之平行排列液晶盒中，經紫外光照射後，可得光學異向性之高分子薄膜。此外，也混合具有向列型液晶相之碟狀液晶單體，利用旋轉塗佈的方式，塗佈在已定向摩擦之PI表面，再經紫外光照射，可得傾斜排列之光學異向性薄膜。這兩種不同方式所做出之高分子薄膜，皆可做為液晶顯示器之補償膜，以改善視角太窄的問題。

In this study, two series of new triphenylene-based discotic liquid crystalline monomers were prepared. For the first series of monomers, a lateral fluoro group is introduced into the peripheral phenyl ring. For the second series of monomers, an ester group is used to link the flexible alkyl spacer and the peripheral phenyl ring. For the first series, all monomers demostrate rectangular columnar mesophase except one with the shortest spacer length. The introduction of fluorine as lateral substitution tends to increase the clearing point of a monomer. Most of these discotic compounds decompose before their clearing temperatures observed on the DSC heating scans. The monomer with longer flexible spacer length shows a lower melting point. For the liquid crystalline monomer containing ester linking group shows a lower clearing point and forms a hexagonal columnar mesophase. In the second part of this study, two methods were used to prepare two kinds of anisotropic polymer films. The discotic liquid crystal monomers were filled into LC cells with parallel alignment and cured with UV radiation to form C-plate type retardation films. Furthermore, we used a spin-coating method to obtain O-plate type retardation films. Both anisotropic polymer films can be used as compensation films in order to improve the viewing angle properties of LCDs.