Photoinduced anisotropy of the photo-alignment of liquid crystals on coumarin-containing copolymer film

In this paper, a copolymer containing photosensitive group was used as photo-alignment film through linearly polarised ultraviolet irradiation to a varying heating rate for an investigation of liquid crystal orientation. When the polymer film is exposed to linearly polarised ultraviolet, it can generate a polarisation-axis selective photoreaction. Then the thin film underwent thermally enhanced photoinduced molecular reorientation followed by subsequent annealing. Fixed exposure energy was 324 mJ cm−2 and annealing temperature was 98°C, heating rates varied from 5 to 30 S °C−1, a large anisotropy was generated. According to the method mentioned in the paper to calculate the enhanced ratio, the best heating rate is 20 S °C−1.