Illumination – Revolving
Reexamination Certificate
1998-10-30
2001-08-14
Henry, Jon (Department: 2872)
Illumination
Revolving
C362S561000, C362S223000, C349S065000
Reexamination Certificate
active
06273577
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light guide plate, a surface light source using the light guide plate, and a liquid crystal display, and more particularly, to a surface light source used for a back light of a liquid crystal display, a lighting advertisement, a traffic-control sign, etc., and a light guide plate provided for the surface light source and a back light type liquid crystal display such as a viewfinder etc.
2. Description of the Prior Art
Examples of a surface light source for a back light of a liquid crystal display (LCD) include one of a side light type having a transparent flat plate as a light guide plate. In such a surface light source, light from such light sources as a fluorescent light is incident from one of side end surfaces of a light guide plate composed of a transparent parallel flat plate or a flat plate having a wedge shape in cross section, the light is propagated throughout the whole area of the light guide plate utilizing total reflection inside the transparent flat plate, a part of the propagated light is changed into diffused reflected light at less than a critical angle by a light scattering reflective plate on the reverse surface of the light guide plate, and the diffused light is emitted from the surface of the light guide plate (see Japanese Utility Model Laid-Open No. 162201/1980, for example).
Examples of a surface light source for a back light also include one so adapted that a lens sheet having a projection of a triangular prism-type lenticular lens on its one surface, the other surface of which is smooth, is superimposed on the surface of a light guide plate provided for the above-mentioned surface light source with the surface of the projection directed upward, to diffuse its diffused emitted light uniformly and isotropically in a desired angular range utilizing a light focusing function of the lens (see, Japanese Utility Model Laid-Open No. 107201/1992, for example).
When the lens sheet is used in combination with a mat transparent diffusing plate (a mat transparent sheet), light energy of a light source is more intensively distributed in a desired restricted angular range, and diffused light higher in uniformity and isotropy can be obtained in the angular range, as compared with a light guide plate using only the mat transparent diffusing plate as disclosed in U.S. patent application Ser. No. 4,729,067.
As a measure to achieve higher luminance of a back light used for a liquid crystal display, there has recently been a tendency to employ such construction that two lenticular lens sheets are overlapped with each other at right angles (see Monthly Display, May 1996, pp. 35~pp. 39).
Furthermore, examples of a surface light source for a back light of a liquid crystal display include one that has an outer light collecting portion at side end surfaces of the light guide plate in order to use outer light, such as the sunlight and a light from a lighting apparatus as a secondary light source. That outer light collecting portion, having a circle shape in cross section, consists of a cylindrical lens (see Japanese Patent Laid-Open No. 11249/1993).
FIG. 19
is a schematic view of a liquid crystal display using the light guide plate. As shown in the figure, a liquid crystal display is provided with a liquid crystal panel
39
on the side of a light emission surface
34
which diffuses and emits the light of a light guide plate
30
. In the case of using this liquid crystal display as a viewfinder for a digital video camera, for example, a body of a camera is positioned on the opposite side (the left side of the figure) of the light emission surface of the light guide plate
30
, and a cameraman watches images from the right side of the liquid crystal panel
39
through light emitted from the light emission surface
34
.
An outer light collecting portion
40
composed of a cylindrical lens having a circle shape in cross-section is provided at the upper end of the light guide plate
1
in order to collect outer light as secondary light. A surface of this cylindrical lens for collecting outer light (the face formed when the dotted-line A-A′ in the figure moves in vertical direction to the paper) faces to the upper direction of the paper (the direction indicated as “the direction of the surface” in the figure), and is constructed so as to collect light from the upper side effectively.
In another situation in using liquid crystal display, however, it is desirable to exploit outer light collected not only from the upper side but also from a light emission surface. The construction in which outer light is taken only from the upper side can not enlarge an area of surface for collecting outer light, therefore, decreases the efficiency of collecting outer light and has a problem that the reduction of power consumption can not be achieved.
SUMMARY OF THE INVENTION
The present invention has been made for solving the above-mentioned problems and has for its object to reduce power consumption at the main light source by increasing the efficiency to collect outer light.
The second object of the present invention is to provide light guide plate which make it possible to abandon the main light source.
The third object of the present invention is to provide surface light source using the light guide plate and liquid crystal display.
In order to attain the above-mentioned objects, the light guide plate of a first embodiment in the present invention is formed of resin in one body and is provided with an outer light collecting portion to collect outer light, a light emission surface for emitting the outer light collected from the outer light collecting portion, and the outer light collecting portion sticks out of the light emission surface to the light emission direction.
In order to attain the above-mentioned objects, the light guide plate of a second embodiment in the present invention is formed of resin in one body and is provided with an outer light collecting portion to collect outer light, a light emission surface for emitting the outer light collected through the outer light collecting portion and a light reflection surface, which is opposite to the light emission surface, for reflecting the outer light collected through the outer light collecting portion, and the outer light collecting portion sticks out of the light emission surface an the light reflection surface.
Further, the light guide plate of the present invention which is formed of resin in one body is provided with an outer light collecting portion to collect outer light, a light emission surface for emitting the outer light collected through the outer light collecting portion and a light reflection surface, which is opposite to the light emission surface, for reflecting the outer light collected through the outer light collecting portion, and the outer light collecting portion sticks out of the light emission surface and the light reflection surface, and the outer light collecting portion is thicker than the light emission surface and the light reflection surface.
In order to attain the above-mentioned objects, the light guide plate of the third embodiment in the present invention is formed of resin in one body and is provided with an outer light collecting portion for collecting outer light at the upper end of the light guide plate, and the surface for collecting outer light of the outer light collecting portion faces to the upper slant direction.
Further, in order to attain the above-mentioned objects, the light guide plate of the present invention is formed of resin in one body and is provided with an outer light collecting portion for collecting outer light and a light emission surface for emitting the collected outer light through the outer light collecting portion. A first lens portion consisting a plurality of lenticular unit lenses in a recessed or projected shape is formed on the light emission surface, and the plurality of lenticular unit lenses in the first lens portion are so arranged that their respective ridge lines are ne
Goto Youichiro
Higuchi Masahiro
Kusafuka Takanari
Nose Toru
Sato Michiaki
Darby & Darby
Henry Jon
Sanyo Electric Co,. Ltd.
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