Synthesis of Discotic Compounds Containing Acrylate and Cinnamoyl Side Groups for Application of Liquid Crystal Photo Alignment Layers
The goal of this study is to synthesize two discotic compounds containing acrylate (HTP6Ac) and cinnamoyl (HTP6Ci) side groups which are used for the application of photo-alignment layers in liquid crystal display (LCD). These compounds were coated on ITO glass substrates and irradiated with linearly polarized UV light (LPUV), and their photo-alignment capability was compared with that of their corresponding discotic compounds containing epoxy(HTP11Ep) and coumarin(HTP11Cu) side groups in terms of thermal stability, photo stability, pretilt angle and twist anchoring energy. For HTP6Ac and HTP6Ci films, they underwent photoaddition and 【2+2】 photodimerization reaction during UV exposure. The LC alignment direction is parallel to the polarization axis of LPUV. Among these four disc compounds, HTP11Cu film required the lowest exposure energy to achieve alignment and showed the highest thermal stability. Both discotic compounds are soluble in common organic solvents. When they are irradiated with a sigle oblique exposure of LPUV light, uniform alignment for a LC cell can be achieved. The pretilt angle is around 1° and the twist anchoring energy is about 10-6 J/cm2. The threshold voltages are below 1.5 V. These discotic compounds have potential application for the alignment materials of TFT-LCD device.