Optical: systems and elements – Holographic system or element – Using a hologram as an optical element
Patent
1989-05-08
1992-01-21
Hille, Rolf
Optical: systems and elements
Holographic system or element
Using a hologram as an optical element
359 79, 359 93, G02F 113
Patent
active
050823531
ABSTRACT:
A liquid-crystal display apparatus comprising two substrates opposing each other and having electrodes formed on the opposing surfaces, at least one of the electrodes being transparent, a nematic liquid crystal layer interposed between the substrates and having pre-tilt angle .theta. of greater than 1.degree. with respect to the surfaces of the substrates, and having a twisting angle of 180.degree. to 360.degree. from the first substrate to the second substrate, a first polarizer arranged on that side of the first substrate which faces away from the electrode formed thereon, a second polarizer arranged on that side of the second substrate which faces away from the electrode formed thereon, and an optical retardation member or a combination of an optical retardation member and a quarter-wave plate, each located between the polarizers. The value of R=.DELTA.n.multidot.d cos.sup.2 .theta. ranges from 0.4 to 0.8, where .DELTA.n is the optical anisotropy of the nematic liquid crystal material, d (.mu.m) is the thickness of the liquid crystal layer, and .theta. is the pre-tilt angle of the liquid crystal material. The value of R'=.DELTA.n'.multidot.d' ranges from 0.22+0.55 m to 0.42+0.65 m, or from 0.47+0.55 m to 0.67+0.65 m (m=0, 1, or 2), where .DELTA.n' is the optical anisotropy of the optical retardation member and d' (.mu.m) is the thickness of the optical retardation member. Owing to the optical retardation member located between the polarizers, and also to the specific values of R and R', the apparatus can perform high-quality monochrome display with great background whiteness and high image contrast.
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Kotani et al., "Effect of Various Parameters on Matrix Display Characteristics of SBE Liquid-Crystal Cells", Proceedings of the Society for Information Display (SID), vol. 28, No. 2, 1987, pp. 149-154.
Nonemissive Electrooptic Displays edited by A. R. Kmetz and F. K. von Willisen, pp. 59-65.
Hille Rolf
Ho Tan
Kabushiki Kaisha Toshiba
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