Anchoring properties of photoaligned azo-dye materials

The photoinduced alignment of a liquid crystal (LC) on films of azo dyes was studied for the liquid crystal display applications. In order to improve the alignment stability of the photoaligned dye (SD-1), the azo-dye derivative with polymerizable terminal groups was synthesized (SDA-1). The films of SDA-1 exhibit good photoalignment properties and ultraviolet stability after thermal polymerization. We investigated the anchoring coefficient for polar and azimuthal energy for both azo-dyes SD-1 and SDA-1 using a differential method developed by us. The polar and azimuthal anchoring strengths of azo-dye aligning materials are comparable with those of usual polyimide aligning materials. The electro-optic response of a 90 degrees twisted LC cell remains almost the same after heating up to 200 degrees C, i.e., the anchoring energy remains considerably high.