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Title: Azodye aligning layers for liquid crystal cells
Authors: Chigrinov, Vladimir G.
Prudnikova, Elena K.
Kozenkov, Vladimir M.
Ling, Zhihua
Kwok, Hoi-Sing
Keywords: Photo-induced alignment
Azo dye film
UV-light polarization
Azimuthal anchoring energy
Thermal stability
Issue Date: 2002
Citation: Society for Information Display International Symposium Digest of Technical Papers, v. 33, no. 2, 2002, p. 1106-1109
Abstract: The photo-induced alignment of liquid crystal onto a photochemical stable azo dye film is studied for the liquid crystal display (LCD) applications. The photo-aligning of azo dye takes place due to the pure reorientation of the molecular absorption oscillators perpendicular to the UV-light polarization. The order parameters S= -0.4 (80% of the maximum absolute value Sm= -0.5) was measured at the wavelength of 372 nm from the polarized absorption spectra. The temperature stable pretilt angle of 5.30 was obtained by a two-step exposure of azo- dye film using normally incident polarized light followed by oblique non-polarized light. The azimuthal anchoring energy of the photo-aligned substrate was Aφ> 10-4 J/m2, which is of the same magnitude as the anchoring of the rubbed PI layer. VHR value of the photo-aligned LC cell was also found to be very high (98-99%) at room temperature and more than 95% at T=800C. The thermal stability of the photo-aligned azo-dye layers is sufficiently high, while UV-stability has to be improved e.g. by polymerization. The bright perspectives for the new LCD aligning technology are envisaged.
Rights: This paper is made available with permission of the Society for Information Display. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
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