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Azo‐dye aligning layers for liquid‐crystal cells
Author(s) -
Chigrinov Vladimir,
Prudnikova Elena,
Kozenkov Vladimir,
Kwok Hoi Sing,
Akiyama Hidenari,
Kawara Tatsuo,
Takada Hirokazu,
Takatsu Haruyoshi
Publication year - 2003
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 - 10.1889/1.1825686
Subject(s) - materials science , liquid crystal , wavelength , polarization (electrochemistry) , optics , absorption (acoustics) , thermal stability , perpendicular , optoelectronics , layer (electronics) , anchoring , liquid crystal display , crystal (programming language) , thermal , absorption spectroscopy , visible spectrum , chemistry , composite material , physics , geometry , organic chemistry , mathematics , structural engineering , meteorology , computer science , engineering , programming language
— The photo‐induced alignment of liquid crystal onto a photochemical stable azo‐dye film was studied for 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 S m = −0.5) was measured at a wavelength of 372 nm from the polarized absorption spectra. The temperature‐stable pretilt angle of 5.3° 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 A ϕ > 10 −4 J/m 2 , which is of the same magnitude as the anchoring of the rubbed PI layer. The 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 =80°C. 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 new LCD aligning technology based on photochemical stable azo‐dye layers is envisaged.