Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2001-03-14
2004-02-17
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S061000, C349S063000, C349S058000, C349S161000, C362S035000, C345S087000
Reexamination Certificate
active
06693682
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display having a structure for preventing temperature rises of a liquid crystal panel and an optical member, and a light source device used for the same.
2. Description of the Related Art
In recent years, as a size of a liquid crystal display has been made larger, a desire has been strong for a liquid crystal display having a high brightness and a widely visible angle. In order to attain the liquid crystal display having the high brightness, it is tried to increase a transmittivity of the liquid crystal panel and improve light usage efficiency. However, since they have limits, an approach of increasing a brightness of a back-light, namely a light source is typically tried.
Also, with regard to the attainment of the widely visible angle, there may be a case that the transmittivity of the liquid crystal panel is sacrificed. In order to compensate this demerit, it is effective to employ a technique for increasing the brightness of the light source.
Thus, the attainment of the higher brightness of the light source gives the sufficient effect to the high brightness and the widely visible angle of the liquid crystal display.
However, as mentioned above, the increase in the brightness of the light source requires an increase in an input power to a light source device. When an attention is paid to the light emission mechanism of the light source, it is typically known that several tens of percents of energy supplied to the light source device are lost as heat. That is, associated with the increase in the input power to the light source, the heat loss is increased, and a calorific value of the light source is increased.
As the calorific value of the light source is increased, a temperature of a liquid crystal panel mounted near the light source device is also raised. Since this liquid crystal panel depends on a temperature characteristic of itself, there may be a fear of a drop in a display quality as the liquid crystal display. Thus, such a liquid crystal display is desired that can attain the high brightness without any drop in the display quality of the liquid crystal panel.
For solving such a problem, a structure is employed in which a fan or a heat sink is mounted on a rear of a body of the liquid crystal display.
A conventional liquid crystal display and a light source device used for the same will be described below with reference to the attached drawings.
FIG. 1A
is a perspective view showing a configuration of a conventional liquid crystal display. As shown in
FIG. 1A
, a liquid crystal display
1
is composed of a body
3
in which a liquid crystal panel
2
, a light source device (not shown) and the like are built in, a radiator
7
mounted on a rear of the body
3
, and a substrate part
8
.
An opening portion
31
a
is positioned on a shield front
31
constituting a surface side of the body
3
. A part of a surface of the liquid crystal panel
2
is exposed in the opening portion
31
a
, and the exposed portion forms a display surface of the liquid crystal display
1
.
Also, the radiator
7
is directly mounted in a shield rear (not shown) constituting the rear side of the body
3
. As the material for this shield rear, aluminum having high heat conduction and a lightweight are used in many cases.
In this way, the heat radiated from the light source device is released through the shield rear having the high heat radiate-ability to external portion.
Here, the surface of the liquid crystal panel
2
implies the display surface of the liquid crystal panel
2
. Hereinafter, with regard to the description of surfaces besides the liquid crystal panel
2
, a plane positioned in a direction similar to the surface of the liquid crystal panel
2
is noted as a surface, and a plane on a rear of the surface is noted as a rear.
The inner structure of the liquid crystal display will be described below with reference to
FIG. 1B
showing a section taken on the line A-A′ of FIG.
1
A. As shown in
FIG. 1B
, in the liquid crystal display
1
, the liquid crystal panel
2
having a form of substantial plate, an optical member
5
such as a diffusion plate or the like, and a light source device
4
are substantially parallel and opposite to each other. The liquid crystal panel
2
is put between a shield front
31
and a shield center
32
. The optical member
5
and the light source device
4
are put between the shield center
32
and a shield rear
33
. Also, the radiator
7
and the substrate part
8
are mounted on the rear of the shield rear
33
.
The structure of the light source device will be described below with reference to
FIGS. 2A and 2B
. As the structure of the light source device
4
, there are mainly a straight fall type structure and a side light type structure.
FIG. 2A
is a section view showing a liquid crystal display having a light source device of the straight fall type structure, and
FIG. 2B
is a section view showing a liquid crystal display having a light source device of the side light type structure.
As shown in
FIG. 2A
, in the light source device
4
having the straight fall type structure, a reflector
43
is mounted inside a substantially dished portion (hereafter, referred to as “lamp house”) of the shield rear
33
. Near a reflector
43
, a plurality of light sources
41
are mounted along the reflector
43
in parallel. Each of the plurality of the light sources
41
is cylindrical in shape. Also, the optical member
5
, such as a diffusion plate or the like, is mounted on a light emission side of the light source device
4
having the straight fall type structure so as to cover the lamp house by keeping a predetermined distance from the light source
41
, in order to avoid an occurrence of irregular brightness.
As shown in
FIG. 2B
, the light source device
4
having the side light type structure is composed of a light guide plate
42
having a form of substantial plate, a light source
41
that is mounted on one side of the light guide plate
42
and is cylindrical in shape, and a reflector
43
mounted so as to surround the light source
41
together with one side of the light guide plate
42
.
The light guide plate
42
is made of acrylic having a high light transmittivity and the like. A light from the light source
41
is transmitted through the light guide plate
42
, and radiated to the rear of the liquid crystal panel
2
from a region of an opening portion
32
a
of the shield center
32
, in the surface of the light guide plate
42
. Also, the gradation process in which a dot for adjusting the irregular brightness and the like are printed is performed on a plane opposite to a light emission surface in the light guide plate
42
, namely, the rear of the light guide plate
42
opposite to the shield rear
33
through the reflector
43
.
As the radiation structure of the conventional liquid crystal display, Japanese Laid Open Patent Application (JP-A-Showa, 61-172181) discloses a technique for radiating heat in a light source device by forming a ventilation port in a lamp house and sending air to the ventilation port, in a liquid crystal display having a light source device of a straight fall type structure.
Concretely, as shown in
FIG. 3
, a lamp house
4
a
is formed in a light source device
4
mounted on a rear side of a printed circuit board
34
equipping a liquid crystal panel
2
. A light source
41
cylindrical in shape is mounted in this lamp house
4
a
. Also, ventilation ports
44
are formed on an upper side and a lower side of the lamp house
41
.
FIG. 4
is a section view when the light source device
4
shown in
FIG. 3
is applied to the liquid crystal display. As shown in
FIG. 4
, an optical member (diffusion plate)
5
is mounted so as to cover the lamp house
4
a
, and the liquid crystal panel
2
is mounted so as to be opposite to the light source
41
through the optical member
5
.
As described above, it is obvious that if a brightness of a display surface in the liquid crystal display is improved, a heat rad
Fujishiro Fumihiko
Fukuyoshi Hirokazu
Hasegawa Fumio
Kanatsu Tsutomu
Ono Shin-Ichirou
McGinn & Gibb PLLC
NEC LCD Technologies Ltd.
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