Synthesis of Discotic Compounds Containing Coumarin Side Groups for the Applications of Liquid Crystal Photo-Alignment Layers
|關鍵字:||香豆素, 碟狀分子, 光配向膜;coumarin, discotic compound, photo-alignment layer|
|摘要:||本研究主要目的是合成含有香豆素感光基團於側鏈的碟狀分子(1M)，並探討其在液晶光配向膜上的應用性。為了探討不同的感光基團對液晶配向性質、感光性和熱穩定性的影響，本研究並比較三種側鏈分別含有香豆素、丙烯酸酯和環氧基不同感光基團的碟狀分子。三種單體以旋轉塗佈法製成膜，經由線性偏極化紫外光 (LPUV) 照射後，都可以產生排列液晶的能力。
單體1M在照光聚合過程當中，利用紫外可見光光譜分析，證實其只進行 (2 + 2) 環化加成反應。經由低能量LPUV照射下，誘導液晶分子排列的方向是平行於LPUV偏極化的方向，而且在相同曝光強度下，單體1M僅需要2.4 J/cm2的曝光能量就可以達到均勻排列液晶分子的效果，遠比需要較多曝光能量的感光基團丙烯酸酯或環氧基來的省時。利用單體1M配向之液晶盒具有相當高的熱穩定性，其經由160℃高溫下測試不會有所改變。此外，利用一次傾斜曝光能夠在1M光配向膜上產生小預傾角。由於單體1M具有感光性高、溶解性好且不需要摩擦定向的優點，將有潛力應用在製備薄膜電晶體驅動的多區域液晶顯示器上。|
The goal of this study is to synthesize a discotic compound (1M) containing coumarin side group for the application of liquid crystal photo-alignment materials. The monomer 1M was also compared with two discotic monomers which containing acrylate and epoxy side groups based on their alignment capability, photosensitivity and device thermal stability. Three monomers were spin coated on the ITO glass substrates and irradiated with linearly polarized UV (LPUV) light. All three monomers showed the photo-alignment capability. The UV-visible spectra verified that monomer 1M underwent 2 + 2 photodimerization during the UV exposure. The LC alignment direction is parallel to the polarization axis of LPUV. The alignment was achieved when the LPUV exposure energy was higher than 2.4 J/cm2. The required exposure energy of monomer 1M was much lower than that of monomers 2M and 3M. It can save processing time in LCD manufacture. The uniform alignment was remained even when the temperature was raised to 160℃. A small pretilt angle was generated when the monomer 1M film was irradiated with single oblique exposure of LPUV light. The monomer 1M with high photosensitivity, good solubility in common organic solvent, has potential application for the multi-domains TFT-LCD devices.