Illumination – Revolving
Reexamination Certificate
2002-07-02
2004-02-17
Quach-Lee, Y. My (Department: 2875)
Illumination
Revolving
C362S026000
Reexamination Certificate
active
06692134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface-emitting device and a liquid crystal display device.
2. Description of the Related Art
Hitherto, in reflective liquid crystal display devices that produce display with ambient light used as a light source, the visibility of the display extremely decreases in an environment in which ambient light is insufficient, for example, when used in a dark place, because the brightness depends on the amount of ambient light. Accordingly, a liquid crystal display device has been proposed in which a front light (surface-emitting device) serving as an auxiliary light source is placed in the front of a reflective liquid crystal display unit (liquid crystal display element). The liquid crystal display device having the front light operates as a normal reflective liquid crystal display device in an environment in which ambient light is sufficient, for example, outdoors in the daytime, and illuminates the front light as the light source, as necessary.
FIG. 6
shows an example of such a liquid crystal display device in which a front light is placed in the front of a liquid crystal display element. A liquid crystal display device
100
shown in
FIG. 6
includes a liquid crystal display unit
120
, and a front light
110
. The front light
110
is placed in the front of (on the upper surface in
FIG. 6
) of the liquid crystal display unit
120
so that a light guide panel
112
is disposed in a display region of the liquid crystal display unit
120
.
The front light
110
includes a flat light guide panel
112
formed by injection-molding a transparent acrylic resin or the like, and a bar light source
113
disposed at an end of the light guide panel
112
. A light-source cover
115
having an angular-U profile and made of a metal plate is mounted from the side of the bar light source
113
. That is, the light-source cover
115
stores the bar light source
113
therein, and grasps the ends of the upper and lower surfaces of the light guide panel
112
on the side of the bar light source
113
by the inner surface at its open leading end, thereby supporting the light guide panel
112
and the bar light source
113
at predetermined positions. A reflecting film (not shown) made of a silver thin film or the like is formed on the inner surface of the light-source cover
115
so as to return light, which is emitted toward the inner surface of the light-source cover
115
without entering the light guide panel
112
, to a light guide member
113
a
for utilization. The lower surface of the light guide panel
112
(on the side of the liquid crystal display unit
120
) serves as an emergent surface from which light emerges, and a surface opposite from the emergent surface (upper surface of the light guide panel
112
) serves as a prism surface
112
c
on which wedge-shaped grooves
114
are alternately and periodically arranged so as to change the direction of light propagating inside the light guide panel
112
.
The bar light source
113
includes a bar-shaped light guide member
113
a,
and LEDs (Light Emitting Diodes)
113
b
disposed at both ends thereof so as to serve as light emitting elements. Light emitted from the LEDs
113
b
is guided to an end face
112
a
of the light guide panel
112
by the light guide member
113
a,
and enters the light guide panel
112
through the end face
112
a.
The liquid crystal display unit
120
is of a reflective type, and produces display by reflecting light incident from the front light
110
by a built-in or externally mounted reflecting plate. The liquid crystal display device
100
having the above configuration produces normal reflective display by reflecting external light in an environment in which external light is sufficient, and produces display by reflecting light from the front light
110
serving as the light source in a dark place in which external light is not obtained.
In the liquid crystal display device
100
having the above configuration, however, a phenomenon in which the brightness of the front light
110
partially decreased sometimes occurred in acceleration tests in which heating and cooling were periodically repeated. The present inventors and the like made examinations on this problem, and found that the decrease of the brightness was caused by the displacement of the light guide panel
112
and the light guide member
113
a.
FIG. 7
is a plan view showing the optical path of the front light
110
shown in FIG.
6
. As shown in
FIG. 7
, a surface of the light guide member
113
a
of the bar light source
113
opposite from the light guide panel
112
serves as a prism surface
118
, and light incident from the LEDs
113
b
on the light guide member
113
a
is reflected by the prism surface
118
, and is emitted toward the light guide panel
112
. Since the propagating direction of the light reflected by the prism surface
118
is limited to a narrow range in the front light
110
having such a structure, the position of the light guide panel
112
relative to the light guide member
113
a
of the bar light source
113
must be exactly adjusted, in particular, in the widthwise direction of the light guide panel
112
, in order to uniformly direct the light into the light guide panel
112
. For example, as shown in
FIG. 7
, when the light guide panel
112
is displaced to the right in the figure, the amount of light at a right edge
116
of the light guide panel
112
partially decreases, and the amount of emergent light is prone to be nonuniform in the plane. This partially decreases the visibility of the liquid crystal display device
100
.
Since the bar light source
113
and the light guide panel
112
are fixed by mounting the light-source cover
115
having an angular-U profile to the end of the bar light source
113
in the liquid crystal display device
100
, as described above, the light guide panel
112
is grasped by the inner side of the light-source cover
115
. Since the light guide panel
112
is clamped by a wide inner surface of the light-source cover
115
in such a structure, the wide inner surface of the light-source cover
115
receives expansion and contraction of the reflecting film formed on the inner surface of the light-source cover
115
, and the light guide panel
112
is prone to displacement.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a reliable surface-emitting device in which a bar light source and a light guide panel can be placed and maintained in precise positions.
Another object of the present invention is to provide a reliable liquid crystal display device in which a surface-emitting device and a liquid crystal display element can be maintained in precise positions.
In order to achieve the above objects, according to an aspect, the present invention provides a surface-emitting device including a bar-shaped light source, and a light guide panel in which light from the light source is introduced from an end face and is emitted from an emergent surface, wherein the light source is supported at an end of the light guide panel by a cover member disposed so as to cover the light source and the end of the light guide panel, projecting pieces are formed at both ends of the cover member so as to clamp the end of the light guide panel from both sides in the widthwise direction, and the light guide panel is positioned in the widthwise direction by the projecting pieces.
In such a configuration, since the light guide panel can be precisely positioned in the widthwise direction by the projecting pieces formed at both ends of the cover member, the light guide panel and the light source are rarely displaced, and the reliability of the surface-emitting device can be increased.
Preferably, projecting pieces contain first portions that project in the widthwise direction of the light guide panel and second portions that extend from the first portions along the lengthwise direction of the light guide panel, and the distance between the projecting pieces is substantially equal
Nagakubo Hideaki
Ohwada Kou
LandOfFree
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