Sheet-like source light device and liquid crystal display...

Illumination – Illuminated scale or dial – Edge illuminated modifier or light rod/pipe

Reexamination Certificate

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Details

C362S035000

Reexamination Certificate

active

06419369

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet-like light source device and a liquid crystal display device using the sheet-like light source device. More particularly, it relates to a sheet-like light source device which is employed as a backlight of a liquid crystal display device, which has high impact resistance and can be manufactured at a low cost even if the device is large in size, and which can suppress the occurrence of uneven brightness, and a liquid crystal display device using the surface light source device.
2. Discussion of the Background
In a liquid crystal display device, a backlight is employed to apply light onto a liquid crystal display element. As shown in
FIGS. 4
to
5
, a conventional backlight has a reflecting plate
4
arranged to face a light reflecting surface
3
b
of a flat light-conducting plate
3
and an optical sheet
6
arranged on the light emission surface
3
c
opposed to the light reflecting surface
3
b.
A light source (lamp)
1
is provided along the light incidence surface
3
a
of the light-conducting plate
3
, and a reflecting member (reflector)
2
is arranged around the light source
1
so as to allow light from the light source
1
to be efficiently incident on the light-conducting plate
3
. In many cases, a fluorescent tube is employed as the light source
1
. One or a plurality of fluorescent tubes are arranged relative to one side surface of the light-conducting plate
3
. The light sources
1
are sometimes arranged on a plurality of sides of the light-conducting plate
3
, respectively. The optical sheet
6
is, for example, a plurality of prism sheets arranged to converge light in the direction of the angle of visibility of the liquid crystal display element
7
. As shown in
FIG. 4
, the light source
1
, reflecting member
2
, light-conducting plate
3
and reflecting member (reflector)
2
are held by a holding member (frame)
5
. This holding member
5
also forms a gap between the liquid crystal display element
7
and the light-conducting plate
3
so as to prevent excessive pressure from being applied onto the optical sheet
6
. With the conventional structure, an optical structure cannot be formed on the side surface of the light-conducting plate
3
facing the light source
1
, and the position of the light-conducting plate
3
cannot be, therefore, fixed using the side surface facing the light source
1
. Due to this fact, as shown in
FIG. 5
, a protrusion
3
d
or a recess is formed on a side surface which does not face the light source
1
to thereby hold the position of the light-conducting plate
3
. A structure to be fitted into this protrusion
3
d
is formed on the holding member
5
. By fitting the structure into the protrusion
3
d,
the light-conducting plate
3
is fixed.
However, due to formation of the protrusion
3
d
for fixing to the light-conducting plate
3
, the following problems occur: (1) Force concentrates on the protrusion
3
d
when impact load is applied. If the surface light source device is larger in size, in particular, the weight of the light-conducting plate increases and the light-conducting plate cannot resist the impact load, thereby causing a crack. (2) Due to the optical structure provided on the side surface of the light-conducting plate
3
, abnormal light emission derived from the optical structure occurs. (3) The formation of the protrusion
3
d
pushes up the unit price of the light-conducting plate or the cost of a die for forming it. (4) The light source
1
cannot be arranged on the side surface having the protrusion
3
d.
(5) If the light-conducting plate
3
has a prism function, abnormal light emission due to the protrusion
3
d
widely occurs on the surface.
The present invention has been made to solve the above-mentioned problems. It is an object of the present invention to provide a sheet-like light source device and a liquid crystal display device using the sheet-like light source device which can ensure high impact resistance even if the sheet-like light source device is large in size, which can be manufactured at a low cost and which can suppress the occurrence of uneven brightness.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a sheet-like light source device of side-light type comprising a light-conducting plate made of transparent material; at least one rod-like light source arranged to be adjacent to a light incidence surface which is at least one side of the light-conducting plate, a tubular reflecting member covering portions of the rod-like light source other than a surface facing the light-conducting plate, a planar reflecting member disposed proximate to a position facing a lower surface of the light-conducting plate, and a holding member housing the light-conducting plate, the light source and both of the reflecting members, wherein a stepped portion is provided on the holding member to contact a part of a side of the light-conducting plate on which the rod-like light source is arranged, with the holding member for holding the light-conducting plate, and a distance between the light-conducting plate and the holding member on the stepped portion is made narrower than a distance between an opening portion of the tubular reflecting member and the light-conducting plate.
Further, a liquid crystal display device according to the resent invention is characterized by disposing a liquid crystal display element on the sheet-like light source device.


REFERENCES:
patent: 6064455 (2000-05-01), Kim
patent: 6074070 (2000-06-01), Sasako
patent: 6219117 (2001-04-01), Nagakubo et al.
patent: 6295105 (2001-09-01), Lee et al.

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