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Novel photoinduced alignment phenomenon of liquid crystals on aromatic polyamide films
Author(s) -
Akiyama Eiichi,
Miyama Yukihiro,
Nagase Yu,
Nemoto Nobukatsu,
Endo Hideyuki,
Nihira Takayasu,
Fukuro Hiroyoshi,
Kohtoh Noriaki
Publication year - 2000
Publication title -
journal of the society for information display
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 52
eISSN - 1938-3657
pISSN - 1071-0922
DOI - 10.1889/1.1828761
Subject(s) - liquid crystal , materials science , polyamide , polymer , chromophore , photochemistry , molecule , irradiation , ultraviolet , ultraviolet light , perpendicular , electric field , chemical structure , visible spectrum , optoelectronics , polymer chemistry , chemistry , organic chemistry , composite material , geometry , mathematics , quantum mechanics , nuclear physics , physics
— The liquid‐crystal (LC) alignment properties of polyamide films exposed to ultraviolet (UV) light were investigated. It was found that the uniform and stable alignment of LC molecules was achieved on films of aromatic polyamides exposed to linearly polarized UV light, even though these polymers contained no common photoreactive group such as cinnamoyl, coumarin, or azo chromophore. The alignment was induced in the same direction, which was perpendicular to the electric‐field vector of the linearly polarized light. The change in the UV‐visible absorption spectra before and after UV exposure suggested that the photoreaction of aromatic polyamide occurred only on the film surface, and that even such a small change in the film was enough to induce uniform alignment of the LC molecules. Furthermore, it was suggested that the photoreaction of this system was accelerated in the presence of oxygen. This paper also deals with the effect of the chemical structure of polymers on their LC photoalignment characteristics, i.e. , the sensitivity of the photoinduced LC alignment. As a result, polymer materials with excellent LC photoalignment sensitivity have been determined, which could induce the uniform and unidirectional LC alignment by irradiation of 0.2–0.5 J‐cm −2 of linearly polarized 313‐nm light. In addition, the alignment of the LC cell was found to be thermally and optically stable.