Azodyes as photoalignment materials for polymerizable liquid crystals

We demonstrate the excellent photoalignment capability of sulfuric azodyes for polymerizable liquid crystals (PLC) whose anisotropic films are extensively studied as basic elements of many passive optical devices (e.g., retardation films, polarizers, and color filters). These dyes exhibit a high affinity to various substrates and insolubility in PLC and organic solvents commonly used for their dilution. An extremely low exposure dose (less than 50 mJ) is needed to induce an excellent planar alignment of PLC. This alignment can be easily patterned using minimal numbers of masks and exposure steps. No sign of alignment deterioration is observed after photopolymerization. These imply that new photoalignment materials can be effectively used for the industrial production of optical films based on PLC. Particularly, they suit the continuous manufacturing process for such films.