Photoalignment of Liquid Crystals on Photo-Cross-Linkable Polymer Films with Anthracene at the End of the Side Group

Authors:
  • NKNobuhiro Kawatsuki
    Nobuhiro Kawatsuki
  • TATadahiro Arita
    Tadahiro Arita
  • YKYuya Kawakami
    Yuya Kawakami
  • TYTohei Yamamoto
    Tohei Yamamoto
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Abstract
Three kinds of photo-cross-linkable polymethacrylate films with an anthracenemethoxybiphenyl side group or an anthracenemethyl side group were irradiated by a linearly polarized (LP) UV light, and the resultant films were applied to the alignment layer for liquid crystals (LC). The photoinduced optical anisotropy of the film was negative and similar among the polymers. Uniform LC alignment could not be obtained on the polymer without the biphenyl group, but the LC aligned homogeneously on the polymers with a biphenyl group. When the absorptive direction of the anthracene group was parallel to the long axis of the biphenyl group, the alignment direction was parallel to the electric vector (E) of the LP-UV light at the beginning of the irradiation and it changed to perpendicular with increase in the exposure dose. In contrast, when the absorptive direction of the anthracene group was not parallel to the long axis of the biphenyl group, the LC alignment direction was perpendicular toE. These types of alignment behavior suggest that the LC alignment direction is controlled by the direction of the biphenyl group in the photo-cross-linked side group.

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