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1 Dec 1999

Volume 86, Issue 11, pp. 5927-6612

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Reversible optical control of transmittance in polymer/liquid crystal composite films by photoinduced phase transition

Hyoung-Kwan Lee, Akihiko Kanazawa, Takeshi Shiono, Tomiki Ikeda, Toru Fujisawa, Masao Aizawa, and Bong Lee

J. Appl. Phys. 86, 5927 (1999); http://dx.doi.org/10.1063/1.371717 (8 pages) | Cited 17 times

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We have demonstrated reversible change in transmittance of composite films, which are composed of an isotropic (I) polymer matrix and a host nematic (N) liquid crystal (LC) containing donor–acceptor type azobenzene LCs (AzoLCs) as photoresponsive molecules, by means of reversible phase transition in the LC domain. The composite films were prepared by in situ thermal polymerization-induced phase separation (PIPS) method from their homogeneous mixtures. Photoisomerization of AzoLCs was induced within the polymer network, and the resultant effect brought about isothermal change in transmittance. The photoinduced reversible and repeatable changes between opaque light scattering and clear transparent states were achieved effectively by irradiation with a monochromatic light at 366 nm. These changes are attributed to photochemical N–I phase transition and rapid thermal I–N phase transition in the host LC domain based on reversible change in molecular sharp of the guest AzoLCs. The optical effects were influenced by such factors as temperature of the composite films in the initial state and photoisomerization ability of the guest AzoLCs. The composite films acted as an optical switching material without polarizers. © 1999 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
42.70.Df Liquid crystals
64.70.M- Transitions in liquid crystals
42.70.Jk Polymers and organics
42.79.Wc Optical coatings
82.35.-x Polymers: properties; reactions; polymerization
82.30.Qt Isomerization and rearrangement
82.50.-m Photochemistry

Dynamic parameter space method to represent the operation modes of liquid crystal displays

Hongfei Cheng, Hongjin Gao, and Fushan Zhou

J. Appl. Phys. 86, 5935 (1999); http://dx.doi.org/10.1063/1.371636 (3 pages) | Cited 3 times

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We have developed a dynamic parameter space method to represent the operation modes of general twisted nematic liquid crystal displays. This method was based on the efficient calculation programs for director distributions by variation technique and optical properties by Berreman’s 4×4 matrix technique. Transmission or reflectance of liquid crystal display devices could be calculated in {φ,dΔn,β} space with varying voltage applied. The dynamic parameter space method is a useful tool to optimize the operation modes of liquid crystal displays. © 1999 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
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