Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
1999-10-29
2002-10-22
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S065000, C349S067000, C349S070000, C349S071000
Reexamination Certificate
active
06469755
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an illuminating apparatus for use in a liquid crystal display for television, a liquid crystal display for a computer and the like, which illuminating apparatus is provided in the back of a liquid crystal display device that displays a picture by modulating an optical state of light; and, in particular, the invention relates to an illumination apparatus having an improved and efficient collimating property and a liquid crystal display device using the same.
Recent technical developments and advancements the liquid crystal displays, and in particular, color liquid crystal displays, have been very remarkable, so that many types of color liquid crystal displays that feature a high performance display quality comparable to that of a cathode ray tube display are now on the market. Further, with the proliferation of note-type personal computers, any type of such liquid crystal display without provision of a back light illumination is not qualified for use as a commercial product, namely, the back light illumination is now an indispensable component in any direct-view-type color liquid crystal display device.
Generally, there are two types of color liquid crystal displays. One type is an active matrix driven twisted nematic (TN) liquid crystal display using thin film transistors (TFT), and another type is a multiplex driven super twisted nematic (STN) liquid crystal display. Both types of display are arranged to display pictures in such a manner that a polarizing plate, which is disposed on both surfaces of a liquid crystal device having its liquid crystal layer interposed between glass substrates, modulates the polarized state of linearly polarized light directed therethrough. More recently, various other types of displays have been proposed, such as ones using the selective reflection of cholesteric, controlling optical scattering and transmittance, optical absorption and transmittance or the like. The levels of brightness of the back light required in these note-type personal computers vary depending on their applications and specifications. However, for color note-type personal computers, it is mandatory to provide for a thin, light-weight design, with a low power consumption in addition to the requirement for a satisfactory brightness level. Still further, there is an increasing expectation for provision of a larger display screen, such as a computer display, using a liquid crystal device, and, therefore, it is necessary to provide for a display having a broader light emission property so as to provide a wider viewing angle, in addition to the provision of an improved brightness. Still more, there is a high expectancy for realization of a television having a larger display screen, wider viewing angle and a brighter liquid crystal display.
Thereby, there have been proposed and realized various methods for providing wider viewing angle liquid crystal displays, using TFTs, and operating in a multi domain vertical alignment nematic (MVA) mode, inplane switching (IPS) mode and the like. However, although these MVA and IPS modes have remarkably improved the viewing angle compared to the conventional TN, STN modes, they are associated with problems such as the occurrence of color changes and a drop in contrast ratio depending on its viewing angle and the like.
Other devices providing a wider viewing angle having no view angle dependency, which is realized on a screen which is disposed on a collimated light source and a liquid crystal display device, are disclosed in WO PCT/US94/07369, PCT/9-500981, PCT/9-505412, PCT/8-511129, PCT/9-507920, PCT/10-500528 and the like. Still other devices having screens and collimating technologies different from the above are disclosed in U.S. Pat. No. 2378252, WO PCT/US97/07374 (JPA Laid-open Nos. 6-202107 and 6-324217), respectively.
Still further, in a fluorescence color display disclosed in JPA Laid-open No. 60-50578 or in a liquid crystal display module disclosed in JPA No. 7-253576, color display devices are proposed which are comprised of an ultraviolet ray or near ultraviolet ray emitting light source; fluorescent materials for emitting red, green or blue color fluorescence disposed corresponding to liquid crystal display pixels by irradiation of ultraviolet rays; liquid crystal elements used as an optical shutter; and a color display unit for displaying a color picture by fluorescence of fluorescent materials. Still another color display unit is disclosed in JPA No. 9-80434, in which a blue color emission organic electroluminescence (EL) is used, and fluorescent material members which produce fluorescent red or green colors by irradiation of the blue light source are disposed in the form of a matrix.
Moreover, in the aforementioned display unit that uses fluorescent materials, its liquid crystal display elements function merely as an optical shutter for selectively allowing ultraviolet rays to pass, and its display is effected by fluorescence of a fluorescent material member disposed corresponding to a pixel through which ultraviolet rays have passed. Its fluorescence color is determined by a property of its fluorescent material, and a bright color rendering of red, green and blue becomes possible without absorption by a color filter, thus realizing a bright and clear color display. Still further, because a uniform spatial dispersion of light from the fluorescent materials is obtained without depending on the direction of the incident light, an improved display quality without a viewing angle dependency is realized.
The aforementioned collimating technology is associated with a problem in that its light utilization efficiency is substantially low. Further, an improved light utilization efficiency, which recently became available using a reflective polarizer based on the polarized light conversion technique disclosed, in U.S. Pat. Nos. 5486949, 5122906, SID 92 Digest p 427, JPA No. 7-36032, SID 95 Digest p 735, is insufficient and not suitable for the purpose of the invention. Still further, a construction using a prism sheet as an optical path converter which uses, for example, a brightness enhanced filter manufactured by 3M, has been disclosed for the purpose of improvement of forward directivity of light, however, its collimating property is low. Because of this low collimating property, when a wide viewing angle display is generated using fluorescent materials on a screen, unclear and bleeding color pictures are displayed due to the thickness of the glass substrates and the like.
SUMMARY OF THE INVENTION
The present invention is directed to a solution of the aforementioned problems, and is designed to provide an illumination apparatus and a liquid crystal display using the same that features a high efficiency collimating function such that an improved brightness and a wider viewing angle for a liquid crystal display can be realized. By provision of the illuminating apparatus that features an improved light utilization efficiency and a collimating function, it will become possible to realize a high brightness liquid crystal display, a wider viewing angle liquid crystal display, and a multiple liquid crystal display which displays a seamless picture on a plurality of liquid crystal displays which are aligned in a matrix array in combination without a gap.
A main object of the invention is to provide an illumination device having an improved collimating function which is realized by providing a collimating unit at a light incidence surface of a light guide, and to provide a bright liquid crystal display using the same. Another object of the invention is to provide a liquid crystal display which features a wider viewing angle by provision of a light spreading screen over liquid crystal elements. Still another object of the invention is to provide a large screen liquid crystal display system having a plurality of liquid crystal displays disposed without gap therebetween, each having a highly collimated illumination; a focus system disposed on the side of the display; a magnification sy
Adachi Masaya
Hiyama Ikuo
Tsumura Makoto
Ngo Julie
Sikes William L.
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