Liquid crystal cells – elements and systems – Particular structure – Interconnection of plural cells in series
Patent
1998-08-24
2000-11-14
Parker, Kenneth
Liquid crystal cells, elements and systems
Particular structure
Interconnection of plural cells in series
349 86, 349187, 349201, G02F 11347, G02F 113
Patent
active
061477265
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a display device and, more particularly, to the structure of a liquid crystal device using a composite multi-layer consisting of a liquid crystal and films and a method of manufacturing the same. The present invention relates to a display device controlling reflection/transmission with the liquid crystal device.
BACKGROUND ART
A conventional reflective liquid crystal display device has been developed and spread as a display device operated with feeble power, and as information transmission medium such as a watch, a calculator, a cellular, a compact portable device, or various home electric products. As display modes, various types such as a TN (twisted nematic) type, an STN (super twisted nematic) type, and a ferroelectric type have been devised. However, all the devices use polarizing plates. Actually, since 60% of incident light to a liquid crystal element are absorbed by the polarizing plate, a dark screen is obtained. A resultant display is far from an ideal reflective display, e.g., a black display on a white background which can be easily seen.
In particular, a reflective color liquid crystal display device reflects a maximum of 10% or less of incident external light being incident on the display device to perform a display because of light absorption of the polarizing plate and a color filter. A resultant display is very dark, and is far from a vivid bright color display such as a display on print.
In recent years, as a method of solving the above drawback and realizing a bright color display without using a polarizing plate, a prior art 1 (Japanese Unexamined Patent Publication No. 6-294952) is proposed to attract attentions. In this propose, a mixture of a liquid crystal material and a polymer material consisting of a photo-set resin is inserted between a pair of substrates, and a laser beam is irradiated on the substrates in two directions, i.e., the upper and lower directions, to cause the interference pattern of the two laser beams to form strong/weak fringes of light in the mixture layer of the liquid crystal and the polymer material. The polymer photo-setting resin is photo-set in the form of layers according to the strong/weak fringe pattern to realize a multi-layer film consisting of polymer photo-setting resin layer/liquid crystal layer/polymer photo-setting resin layer/liquid crystal layer, . . . . Light having a specific wavelength range is interference-reflected according to the principle of composite multi-layer film interference reflection. When a voltage is applied to the multi-layer film by electrodes on the inner surfaces of the pair of substrates, the molecular axis direction of liquid crystal molecules in the liquid crystal layer changes. Accordingly, the refraction factor of the liquid crystal layer also changes. Therefore, the conditions of the interference reflection cannot be satisfied, and reflected light intensity also changes. In this way, light modulation can be performed by a voltage, the device functions as a display device. In the display device mentioned above, since any polarizing plate is not used, bright colors can be obtained. In addition, by changing the wavelength or irradiation angle of the irradiated laser beam, an interference pitch can be freely selected to realize arbitrary display colors. The display device, especially, as a reflective color display device, is more excellent than a conventional TN or STN reflective color display device.
However, as the drawback of the display device, as described in a prior art 2 (ASIA DISPLAY '95 P603-606), since a layer consisting of a photo-setting resin is formed with interference by two laser beams, the interference pitch is highly accurate, and the wavelength width of interference-reflected light is very narrow. Therefore, the display has vivid colors, but lacks brightness as a reflective display is obtained. In general, white is most desirable as a background color of the reflective display. For this reason, the conditions of interference reflection must be satisf
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"Three-Primary-Color Holographic Polymer Dispersed Liquid Crystal (HPDLC) Devices for Reflective Displays", M. Date, N. Naito, K., Tanaka, K. Kato, S. Sakai, NTT Interdisciplinary Res. Labs., Musashino, Japan, ASIA DISPLAY '95, pp. 603-606.
"9.1: Reflective Color LCDs Based on H-PDLC and PSCT Technologies", G.P. Crawford, T.G. Fiske, dpiX, A Xerox Company, Palo Alto, CA, L.D. Silverstein, VCD Sciences, Scottsdale, AZ, SID 96 DIGEST, pp. 99-102, 1996.
"Holographically Formed Liquid-Crystal/Polymer Device for Reflective Color Display", Kenji Tanaka, Kinya Kato, Shinji Tsuru, Shigenoubu Sakai, NTT Interdisciplinary Research Laboratories, Tokyo, Japan, Journal of the SID (Society for Information Display), Feb. 1, 1994, pp. 37-40.
Kimura Mutsumi
Koyama Tomoko
Kubota Kanemitsu
Parker Kenneth
Seiko Epson Corporation
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