Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-09-08
2004-11-23
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06822710
ABSTRACT:
CROSS REFERENCE
This application claims the benefit of Korean Patent Application No. 1999-38155, filed on Sep. 8, 1999, under 35 U.S.C. § 119, the entirety of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a backlight device, and more particularly, to a backlight device for use in a liquid crystal display (LCD) device.
2. Description of Related Art
FIG. 1
shows a conventional backlight device for use in an LCD device. As shown in
FIG. 1
, the conventional backlight device
100
includes a light source
10
, a U-shaped lamp holder
15
having a lamp reflector
16
, a light waveguide plate
40
, a reflector
50
, and a prism sheet
20
. The light source
10
is located adjacent to an end
40
a
of the light waveguide plate
40
, and most of the light source
10
is surrounded by the lamp holder
15
. The end
40
a
constitutes a surface through which the incident light from the light source
10
is emitted. The prism sheet
20
is arranged on a front surface
40
b
of the light wave guide plate
40
, and the reflector
50
is located under a bottom surface
40
c
of the light wave guide plate
40
.
The emitted light from the light source
10
is directed toward the surface
40
a
of the light waveguide plate
40
by the lamp reflector
16
and is then directed either toward a prism sheet
20
or a reflector
50
. The light reflected by the reflector
50
is emitted toward the observer through a prism sheet
20
, and a liquid crystal panel (not shown) in the form of an information.
FIG. 2
is a graph illustrating brightness with respect to an angle of light passing through the prism sheet. As shown in
FIG. 2
, brightness distribution is discursive. In other words, light passing through the prism sheet
20
is not well collimated. As a result, light collimating efficiency is bad, and collimating loss takes place at portions “A”. In addition, in the conventional backlight device of such a structure, it is not easy to narrow an angle of light passing through the prism sheet to a desirable angle range (for example, from −40 degrees to +40 degrees).
For the foregoing reasons, there is a need for a backlight device having a high light collimating efficiency.
SUMMARY OF THE INVENTION
To overcome the problem described above, preferred embodiments of the present invention provide a backlight device having a high light collimating efficiency.
In order to achieve the above object, a preferred embodiment of the present invention provides a backlight device for a liquid crystal display device, including: a light source providing light; a light waveguide plate guiding light from the light source, having an emitting surface, a front surface and a bottom surface, the emitting surface being adjacent to the light source; a reflector arranged under the bottom surface of the light wave guide plate, reflecting light; and at least one cholesteric liquid crystal (CLC) film arranged over the front surface of the light wave guide plate, collimating light.
The CLC film has a one-layered structure of one of either a right- or a left handed CLC layer, wherein the right- and left handed CLC layer selectively reflect right- and left-handed circularly polarized light, respectively. The CLC film may also have a dual-layered structure of a right- and a left handed CLC layer, wherein the right- and left handed CLC layer selectively reflect right- and left-handed circularly polarized light, respectively. The backlight device further includes a prism sheet arranged between the CLC film and the front surface of the light wave guide plate.
By using the backlight device according to preferred embodiments of the present invention, light collimating efficiency and brightness can be improved.
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Moon Jong-weon
Son Hyeon-Ho
LG. Philips LCD Co. Ltd.
Parker Kenneth
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