Illumination – Revolving
Reexamination Certificate
1999-06-16
2001-06-26
Sember, Thomas M. (Department: 2875)
Illumination
Revolving
C362S084000, C362S800000, C362S023000
Reexamination Certificate
active
06250767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light guide plate, a surface light source and a display using the light guide plate, and more particularly, relates to a light guide plate which collects light from an internal light source and external light from the sun or a fluorescent lamp and emits a simple light or a synthesized light from a light emissive surface thereof, a surface light source serving as a back light for a non-self light emission type display, which does not emit light by itself, such as a liquid crystal display, and a back light type display such as a liquid crystal display for a digital still camera or a video camera which displays an object.
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 lamp is incident from one of side end surfaces of a light guide plate comprising 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 by 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. 16220 1/1980).
Furthermore, examples of a surface light source for a back light include one that has an external light collecting portion at side end surfaces of the light guide plate in order to use external light such as the sunlight and light from a lighting apparatus as a secondary light source. The external light collecting portion, having a semicircle shape in cross section, forms a cylindrical lens (see Japanese Patent Laid-Open No. 11249/1993).
FIG. 6
is a schematic view illustrating a conventional liquid crystal display.
The conventional liquid crystal display comprises a liquid crystal panel
111
, an internal light source
110
such as a fluorescent tube, and a light guide plate
100
. When using this liquid crystal display as a liquid crystal monitor for an electric still camera, for example, a body of a camera is positioned on the left hand of the light guide plate
100
in the figure, and a user watches images from the right hand of the liquid crystal panel
111
in the figure through the light emitted from the light emissive surface
103
.
An external light collecting portion
101
comprising a cylindrical lens having a semicircle shape in cross-section is provided at an upper end of the light guide plate
100
included in the conventional liquid crystal display in order to collect external light as main light. Therefore, external light from the upper and side direction can be collected effectively.
An internal light source
110
is provided in the lower proximity to an internal light collecting surface
102
which is opposite to the external light collecting portion
101
. The internal light source
110
emits secondary light to the internal light collecting surface
102
when external light is not sufficient due to cloudy or rainy weather or indoor use. The light incident from the internal light collecting surface
102
reflects several times in the inside of the light guide plate
100
and most of the incident light is emitted from the light emissive surface
103
in the end.
The conventional liquid crystal display, however, has a construction in which the external light collecting portion
101
and the internal light source
110
face each other. In conjunction with this, light reflection process can not be applied to the external light collecting portion
101
and the internal light collecting surface
102
since light comes in from the external and internal light source. As a result, a part of the external light collected from the external light collecting portion
101
leaks from the internal light collecting surface
102
and a part of the light incident from the internal light source through the internal light collecting surface
102
e dispersed from the external light collecting portion
101
, causing extreme decrease the efficiency of utilizing the external light and the light from the internal light source.
The thickness of the light guide plate comprising the light guide plate
100
and the internal light source
110
of the conventional liquid crystal display in
FIG. 6
is considerably restricted to the thickness of the internal light source
110
as taking the collecting efficiency of internal light and limitation in size of the internal light source
110
in mechanical view point into consideration. It causes a difficulty in making a light guide plate slimmer.
SUMMARY OF THE INVENTION
To overcome the above described drawback, the present invention has an objective to provide a light guide plate and a surface light source using the light guide plate to improve the utilization efficiency of external light and light from an internal light source and to achieve a slimmer light guide plate.
A light guide plate according to the present invention comprises a light guide plate having a light incident surface and light emissive surface, an external light collecting portion formed on one end of the light guide plate for collecting external light, and an mounting portion for an internal light source formed for mounting an internal light source in proximity to the external light collecting portion in the light guide plate.
The light guide plate of the present invention includes an internal light collecting surface formed on the mounting portion for an internal light source.
The mounting portion for an internal light source may be formed in a position where external light incident from the external light collecting portion in the light guide plate is not obstructed thereby.
The mounting portion for an internal light source can be formed on the light emissive surface in the light guide plate.
The mounting portion for an internal light source is formed on an opposite surface to the light emissive surface in the light guide plate and on the external light collecting portion side from an extended line along the most upper surface on which a non-self light emission type display is mounted.
In the above mentioned construction, a light reflection process can be employed to the opposite surface to the external light collecting portion. Therefore, the present invention can contribute to reducing electric power consumption by preventing the light collected from the external and internal light collecting portion from being leaked and improving the efficiency of light utilization.
A surface light source of the present invention comprises a light guide plate having a light incident surface and light emissive surface, an external light collecting portion formed on one end of the light guide plate for collecting external light, an mounting portion for an internal light source formed in proximity to the external light collecting portion in the light guide plate, and an internal light source provided to the mounting portion for an internal light source.
The internal light source is formed in a position where external light incident from the external light collecting portion in the light guide plate is not obstructed thereby.
In the above mentioned construction, the internal light source is disposed in proximity to the external light collecting portion and a light reflection process can be employed to the opposite surface to the external light collecting portion. Therefore, the present invention can contribute to reducing electric power consumption by preventing the light collected from the external and internal light collecting portion from being leaked and by improving the efficiency of light utilization.
The internal light source can be disposed on the light emissive surface in the
Higuchi Masahiro
Kiyota Kenji
Kusafuka Takanari
Okamoto Kenkiti
Sato Michiaki
Arent Fox Kintner & Plotkin & Kahn, PLLC
Sanyo Electric Co,. Ltd.
Sember Thomas M.
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