We have found that the condensation-type aromatic polymers such as polyamide, polyurea and polyester acted as LC photo-alignment layers by the exposure of the linearly polarized UV light. These LC photo-alignment materials showed very high sensitivity and the obtained TN cell with them achieved the durability against light and heat. However, the photo-reactivity and the photo-induced alignment mechanism have not yet been revealed. In this study, two kinds of aromatic polyesters with and without the ability of photo-alignment material were prepared, and their different photo-reactivities were investigated by means of UV-Vis absorption spectra, surface energy and IRRAS. As a result, the photo-reaction induced by n-π exciting of carbonyl group anisotropically occmted with no relation to the performance as the LC alignment layer. But it was suggested that the reaction selectivity was different between the two kinds of the polyesters.
