Illumination – Revolving
Reexamination Certificate
2002-07-29
2004-12-07
Lee, Y My Quach (Department: 2875)
Illumination
Revolving
C362S561000
Reexamination Certificate
active
06827460
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-235820, filed Aug. 3, 2001, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lighting panel and a display device in which the lighting panel is used and, particularly, to a lighting panel having a light-collecting function of collecting and emitting incident light rays introduced from a light source or the outside.
2. Description of the Related Art
In a liquid crystal display device, for example, a liquid crystal display panel does not have a self-emission capacity and, therefore, a lighting panel is disposed as a back light on the rear surface side of the liquid crystal display panel.
FIG. 24
is a side view of part of an example of such a conventional liquid crystal display device. The liquid crystal display device comprises a liquid display panel
1
and a lighting panel
11
which is disposed on the rear side opposite to the front surface side of the panel which is the observation side.
The liquid crystal panel
1
is configured in such a manner that a glass substrate
2
on the front surface side and a glass substrate
3
on the rear surface side are bonded together through a sealing member (not shown) in the form of a substantially square frame, and that a liquid crystal (not shown) is sealed in a space enclosed by the two glass substrates
2
,
3
and the sealing member. A polarizer
4
on the front surface side is bonded to the front surface of the glass substrate
2
on the front surface side and a polarizer
5
on the rear surface side is bonded to the rear surface of the glass substrate
3
on the rear surface side.
The lighting panel
11
includes a light guide plate
12
provided on the rear surface side of the liquid crystal panel
1
. The light guide plate
12
has a flat square shape. The surface of the light guide plate
12
opposed to the liquid crystal panel
1
serves as an emission surface
13
from which light is emitted, and a prescribed end surface (the left-hand end surface in
FIG. 24
) of the light guide plate
12
serves as an incidence surface onto which light is incident. The light guide plate
12
is configured in such a manner that an inclined surface
15
is formed so that the thickness of the light guide plate
12
becomes gradually small, along the rear surface on the rear side with respect to the emission surface
13
, from the side of the incidence surface
14
to the side of an end surface
12
a
opposed to the incidence surface
14
.
A reflector
16
is attached to the inclined surface
15
of the light guide plate
12
. A cold cathode fluorescent tube (a light source)
17
is provided in a position facing the incidence surface
14
of the light guide plate
12
. An end portion of the reflecting sheet
18
which covers the cold cathode fluorescent tube
17
is attached to the front surface on the incidence surface side
14
of the light guide plate
12
, and the other end portion is bonded to the rear surface on the incidence surface side
14
of the reflector
16
.
Light coming from the cold cathode fluorescent tube
17
and light reflected by the reflecting sheet
18
are caused to be incident onto the incidence surface
14
of the light guide plate
12
. The incident light propagates (is guided) through the light guide plate
12
from the incidence surface
14
toward the end surface
12
a
, is reflected by the reflector
16
, emitted from the emission surface
13
and caused to be incident onto the rear surface of the liquid crystal display panel
1
, and is caused to irradiate the liquid display panel
1
from the rear surface side thereof. Then, image light corresponding to the display drive of the liquid display panel
1
is emitted from the front surface of the liquid display panel
1
.
In the above conventional liquid crystal display device, it is possible to uniformize the luminance distribution of light emitted from the front surface of the liquid crystal display panel
1
by uniformizing an amount of light emitted from the emission surface
13
of the light guide plate
12
. Next, this principle will be described below. On the inclined surface
15
of the light guide plate
12
are provided a large number of spot-like light control patterns in black ink in such a manner that the density of spot-like black patterns decreases gradually as they become away from the incidence surface
14
, in other words, the absorptance of incident light decreases in proportion to the distance from the incidence surface
14
.
More specifically, because near the cold cathode fluorescent tube
17
, the intensity of the light which is reflected by the reflector
16
of the light guide plate
12
and emitted from the emission surface
13
toward the liquid crystal display panel
1
is high, the black pattern density formed on the inclined surface
15
of the light guide plate
12
is increased in order to increase the absorptance of the light reflected by the reflector
16
. However, because the intensity of the light reflected by the reflector
16
decreases with increasing distance from the cold cathode fluorescent tube
17
, the black pattern density formed on the inclined surface
15
of the light guide plate is gradually reduced so that the absorptance decreases gradually. As a result, the intensity of the light emitted from the emission surface
13
of the light guide plate
12
becomes uniform over the whole surface.
In the above conventional liquid crystal display device, because a large number of spot-like light control patterns in black ink are provided on the inclined surface
15
of the light guide plate
12
, part of light is absorbed by the light control patterns. This poses the problem that the utilization efficiency of light is low, resulting in a decrease in luminance. BRIEF SUMMARY OF THE INVENTION
The object of the invention is to provide a lighting panel capable of improving the utilization efficiency of light and a display device in which the panel is used.
In a first aspect of the invention, an optical surface constituted by a large number of continuous optical elements is provided on a light guide plate. Each optical element has a curved surface, which refracts part of light introduced from the incidence surface toward the end surface at a low angle along a plane parallel to the emission surface, and an inclined surface which refracts part of light refracted by the curved surface toward the emission surface.
In a second aspect of the invention, on a light guide plate which has an incidence surface on which light emitted from a point light source is incident, there is formed an inclined surface which is extended in a direction substantially parallel to the incidence surface.
In a third aspect, an optical sheet is disposed on the side of an emission surface of a light guide plate. The optical sheet causes light emitted from the emission surface of the light guide plate in a direction substantially perpendicular to the emission surface to pass therethrough without any change, and converts light emitted in a slant direction from the emission surface of the light guide plate toward an end surface of the light guide plate into light to be emitted from the front surface of the optical sheet in a direction substantially perpendicular to the emission surface of the light guide plate.
According to the first aspect of the invention, owing to the optical surface formed on the light guide plate, which has the curved surfaces and inclined surfaces, also on a distal end remote from the incidence surface of the light guide plate, light introduced from the incidence surface is sufficiently refracted to the emission surface of the light guide plate. Therefore, the utilization efficiency of light can be improved.
According to the second aspect of the invention, light introduced from the point light source is refracted in a direction parallel to the incidence surface by means of the in
Casio Computer Co. Ltd.
Frishauf Holtz Goodman & Chick P.C.
Lee Y My Quach
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