Optical: systems and elements – Mirror – With mirror surface of varied radius
Patent
1997-02-18
1998-12-01
Shafer, Ricky D.
Optical: systems and elements
Mirror
With mirror surface of varied radius
359870, 359847, 359848, 359883, 4283084, 4283157, 428480, G02B 510, G02B 508, G02B 7188, G02B 7182
Patent
active
058447318
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a light reflecting plate applied to a light box of a liquid crystal display or lighting equipment such as a fluorescent lamp or an incandescent lamp.
BACKGROUND ART
In a side light type liquid crystal display, a light box having a structure as shown in FIG. 1 is generally used to obtain a function as a surface light source. As shown in FIG. 1, a light reflecting plate 1, a light guide plate 2, and a translucent diffusion plate 3 are stacked, and a lamp 4 is arranged on the side of these plates. Light from the lamp 4 is guided to the light guide plate 2, with repeating diffuse reflection in the interface between the light guide plate 2 and the light reflecting plate 1, and finally emitted to a display screen through the translucent diffusion plate 3. Examples of the methods used to cause the diffuse reflection in the interface between the light guide plate 2 and the light reflecting plate 1 as described above are: a method of printing a pattern which causes diffuse reflection on the lower surface (the boundary surface with respect to the light reflecting plate 1) of the light guide plate 2; a method of inserting a film on which a predetermined pattern is printed between the light guide plate 2 and the light reflecting plate 1; and a method of giving fine texture to the lower surface of the light guide plate 2.
Also, since the light reflecting plate 1 is required to have a high reflectance, various materials described below are conventionally used. As an example, a light reflecting plate is known which is manufactured by forming a metal mirror surface by depositing a metal deposition film on the surface of a substrate such as a metal. Unfortunately, since diffuse reflection does not easily occur on a light reflecting plate having a metal mirror surface, the quantity of light propagating to the display screen decreases contrary to the expected result. A light reflecting plate made from a film containing a white pigment such as titanium oxide is also used. In a light reflecting plate constructed of this film, the addition amount of the pigment must be increased to suppress the leakage of light to the rear surface. However, the white pigment added to the film absorbs light having a specific wavelength. Accordingly, if the addition amount is increased, an increase in the light loss can no longer be neglected and the reflectance decreases.
Jpn. Pat. Appln. KOKAI Publication No. 4-296819 has disclosed a light reflecting plate made from a polyester film containing fine cells. A light reflecting plate made from a laminated film of this polyester film containing fine cells and another polyester film in which grains of calcium carbonate or silica which does not absorb light are dispersed is also disclosed. This polyester film containing fine cells is manufactured by dispersing an incompatible polymer in polyester and forming voids (cells) around the incompatible polymer grains when the polyester is uniaxially or biaxially oriented. However, it is difficult to uniformly disperse the incompatible polymer in polyester. Therefore, the dispersion of cells in the polyester is also nonuniform and so light cannot be well diffuse-reflected. Additionally, the oriented film is as thin as less than 200 .mu.m, and this increases the leakage of light to the rear surface of the film. As a consequence, a satisfactory reflectance is difficult to achieve by the film disclosed in the above-mentioned publication. To obtain a sufficient reflectance, therefore, it is necessary to arrange another light reflecting plate having a metal mirror surface on the rear surface of the film.
Analogously, the shade of lighting equipment, for example, is sometimes required to have a high reflectance. Examples of light reflecting plates for this use are a light reflecting plate constructed of a metal material such as a steel plate or an aluminum plate and a light reflecting plate manufactured by coating the surface of a plastic injection-molded product with a paint containing a light-reflective pigment
REFERENCES:
patent: 3637458 (1972-01-01), Parrish
patent: 5113476 (1992-05-01), Okada et al.
patent: 5118372 (1992-06-01), Spahn
patent: 5269977 (1993-12-01), Nakahashi et al.
patent: 5645929 (1997-07-01), Debe
Ito Masayasu
Kabumoto Akira
Okada Mitsunori
Yoshida Naoki
Shafer Ricky D.
Sikd-er Mohammad Y.
The Furukawa Electric Co.,Ltd.
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