Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2002-10-25
2004-12-28
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C362S035000
Reexamination Certificate
active
06836303
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) apparatus, and more particularly to a light guide plate for improving a front visual angle characteristic and an LCD apparatus having the same.
2. Description of the Related Art
In general, an LCD apparatus has an advantage over a CRT type display apparatus in aspects of weight and size. The advantage of the LCD can be realized by using a liquid crystal. The liquid crystal is controlled by an electric field. The liquid crystal is arranged in a predetermined direction parallel to a direction of the electric field, and a light transmittance varies depending on the arrangement of the liquid crystal.
The LCD apparatus requires a light to display an image through the liquid crystal. That is, since display properties are varied depending on a uniformity of a light provided to the liquid crystal, the light having a uniform brightness has to be provided to the liquid crystal.
However, it is difficult to provide a surface light source having the uniform brightness to the liquid crystal. Thus, a lamp
10
having a linear light source or a light emitting diode (LED) having a point light source are used as a device that provides the light as shown in FIG.
1
.
FIG. 1
is a schematic view showing an LCD panel of a conventional LCD apparatus.
FIG. 2
is a graph showing a distribution of brightness in accordance with a visual angle in the LCD apparatus shown in FIG.
1
.
Referring to
FIG. 1
, the light having the linear light source or the point light source is incident to a light guide plate
20
, and then the light guide plate
20
converts the light having the linear or point light sources into a light having the surface light source.
After converting the linear light source into the surface light source by the light guide plate
20
, the light is emitted through a light emitting surface of the light guide plate
20
. However, since a refractive index of the light guide plate
20
is greater than that of an air, the light having the surface light source is emitted in a direction inclined, about 75 to 83 degrees, with respect to a direction perpendicular to a light emitting surface of the light guide plate
20
. This means that the brightness of the front visual angle of the LCD having the light guide plate
20
is lowered, so that a quality of the displayed image is not desirable.
To prevent the brightness from being lowered, a diffusion sheet
30
, a first prism sheet
43
, a second prism sheet
46
are sequentially disposed on the light guide plate
20
. The diffusion sheet
30
, the first prism sheet
43
and the second prism sheet
46
change the direction of the light inclined with respect to a normal line to the light emitting surface into a direction perpendicular to the light emitting surface of the light guide plate
20
.
The LCD apparatus further includes a reflecting plate
15
under the light guide plate
20
, a protecting sheet
50
on the second prism sheet
46
and LCD panel
60
that controls the liquid crystal.
Referring to
FIG. 2
, a graph indicated by a character “a” shows the brightness distribution of the light emitted through the light guide plate
20
, a graph indicated by a character “b” shows the brightness distribution of the light sequentially emitted through the light guide plate
20
and the diffusion sheet
30
, and a graph indicated by a character “c” shows the brightness distribution of the light sequentially emitted through the light guide plate
20
, the diffusion sheet
30
and the first and second prism sheets
43
and
46
.
With reference to the graph “a”, in case of the light through the light guide plate
20
, the brightness of the front visual angle is low and the brightness of the visual angle of about 70 to 80 degrees is maximized. The light emitted from the diffusion sheet
30
has the brightness of the front visual angle generally greater than that of the light emitted from the light guide plate
20
, as indicated by the character “b”. The light emitted from the first and second prism sheets
43
and
46
has the highest brightness of the front visual angle as indicated by the character “c”. The light of which the direction thereof is corrected by the diffusion sheet
30
, the first prism sheet
43
and the second prism sheet
46
is provided to the LCD panel, thereby displaying the image having a uniform brightness in general.
However, since the LCD apparatus adopts some sheets such as the diffusion sheet
30
, the first and second sheets
43
and
46
and so on, the thickness and the weight of the LCD apparatus are increased. Also, the manufacturing cost of the LCD apparatus increases by adopting the diffusion sheet
30
, the first and second sheets
43
and
46
and the like.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a light guide plate for improving a front visual angle characteristic.
The present invention provides an LCD apparatus having a reduced number of optical sheets.
The present invention provides an LCD apparatus without an optical sheet.
In one aspect of the invention, there is provided a light guide plate comprising: a side portion for receiving light; a light reflecting portion for reflecting the light input through the side portion; and a light emitting portion facing the light reflecting portion, for emitting the light reflected by the light reflecting portion, wherein the light emitting portion has a visual angle correcting means for increasing a brightness of the light emitted through the light emitting portion at a front visual angle.
In another aspect, there is provided an LCD apparatus comprising: an LCD panel assembly for controlling a liquid crystal to display an image; and a backlight assembly having a lamp assembly for supplying a light and a light guide plate for guiding the light from the lamp assembly to the LCD panel assembly, wherein the light guide plate comprises a side portion for receiving the light, a light reflecting portion for reflecting the light input through the side portion, and a light emitting portion facing he light reflecting portion, for emitting the light reflected by the light reflecting portion, the light emitting portion includes a visual angle correcting means for increasing a brightness of the light emitted through the light emitting portion at a front visual angle.
In further aspect, there is provided an LCD apparatus comprising: an LCD panel assembly for controlling a liquid crystal to display an image; and a backlight assembly having a lamp assembly for supplying a light, a light guide plate for guiding the light from the lamp assembly to the LCD panel assembly and a prism sheet disposed between the LCD panel and the light guide plate, wherein the light guide plate comprises a side portion for receiving the light, a light reflecting portion for reflecting the light input through the side portion, and a light emitting portion facing the light reflecting portion, for emitting the light reflected by the light reflecting portion, and the light emitting portion includes a visual angle correcting means for increasing a brightness of the light emitted through the light emitting portion a front visual angle.
REFERENCES:
patent: 4043636 (1977-08-01), Eberhardt et al.
patent: 4811507 (1989-03-01), Blanchet
patent: 5394308 (1995-02-01), Watanabe et al.
patent: 5961198 (1999-10-01), Hira et al.
patent: 6700632 (2004-03-01), Taniguchi et al.
Cantor & Colburn LLP
Kim Robert H.
Samsung Electronics Co,. Ltd.
Schechter Andrew
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