Illumination – Revolving
Patent
1998-07-30
2000-08-08
Spyrou, Cassandra
Illumination
Revolving
362 32, 362 26, 362 29, 362302, 362309, 385 36, 359599, F21V 800
Patent
active
060991356
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The Present invention relates to a surface light source device for a display apparatus such as a liquid crystal display device for use in a portable personal computer, a liquid crystal television or the like; a sign display apparatus such as a guide marking board, a large-size signboard or the like used in a station, public facilities or the like; or for a traffic sign display apparatus such as various types of guide signs, traffic signs or the like on a highway road or a general road; and the present invention relates more particularly to a surface light source element for emitting light which has high brightness and a uniform brightness distribution on a light emitting plane without performing any uniformity-enhancing processing such as treatment with a spot pattern or the like.
DESCRIPTION OF THE RELATED ART
Recently, a color liquid crystal display device has been widely used in various applications such as in portable personal computers, liquid crystal televisions, video built-in type liquid crystal televisions, etc. This liquid crystal display device comprises a back light portion and a liquid crystal display portion. An under-lighting system in which a light source is disposed just under the liquid crystal display portion and an edge-lighting system in which a light source is disposed on the side surface of a light conductor are used as a lighting system for the back light portion.
Recently, the edge-lighting system has been more frequently used because it is more suitable for reducing the size of the liquid crystal display device. In the edge-lighting system, the light source is disposed at a side surface portion of a planar light conductor so as to emit light from the entire surface of the light conductor, and thus the back light portion using this system is called a "surface light source device".
According to such a surface light source device, a light conductor is formed of a planar transparent member such as an acrylic resin plate or the like, and light emitted from a light source which is disposed at the side surface of the light conductor is introduced through the side surface (light incident face) of the light conductor into the light conductor. The incident light totally (completely) reflects from the obverse surface of the light conductor (light emitting face) and the back surface of the light conductor and then passes through the light conductor. Further, a light emitting function or light emitting portion such as a light the light conductor to emit the light from the whole light emitting face. However, when the light emitting portion is uniformly formed on the obverse surface or the back surface of the light conductor, the brightness of the emitted light is more reduced as the light is farther away from the light source, so that the brightness distribution on the light emitting plane becomes disuniform and thus a high-quality display image cannot be obtained.
This result is more noticeable as the size of the liquid crystal display device increases, and thus the surface light source device cannot practically be used for a large-size liquid crystal display device of 10-inches or more in size. Despite this, large-size liquid crystal display devices have recently been in demand and, following this recent demand, liquid crystal display devices used for portable personal computers, liquid crystal televisions or the like have additionally been required to have a brightness distribution of very high uniformity on the screen thereof.
Furthermore, marking apparatuses such as a guide signboard or a large-size signboard, and traffic sign apparatuses such as a guide sign, a traffic signboard or the like, have used two illumination systems, i.e., an internal illumination system and an external illumination system, to enhance visual recognition and character recognition at night. According to the internal illumination system, characters, figures, photographs, etc., are formed on a semi-transparent plastic plate such as a methacrylate plate or the like by cut-out, print or the
REFERENCES:
patent: 5550676 (1996-08-01), Ohe et al.
patent: 5627926 (1997-05-01), Nakamura et al.
patent: 5718497 (1998-02-01), Yokoyama et al.
Chiba Issei
Hayashi Yasuko
Oda Masaharu
Mitsubishi Rayon Co. Ltd.
Sikd-er Mohammad Y.
Spyrou Cassandra
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