Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2000-10-20
2003-05-20
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S063000, C361S689000
Reexamination Certificate
active
06567137
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 1999-13184, filed on Apr. 14, 1999, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reflective liquid crystal display, and more particularly to an auxiliary light source unit for radiating light other than natural light onto a reflective liquid crystal display.
2. Discussion of the Related Art
A liquid crystal display (LCD) is a flat panel display device having advantages of small bulk, thin thickness and low power consumption. LCDs have been used in connection with portable computer devices, such as notebook personal computers, office automation equipment and audio/video machinery, etc. LCDs control an electric field applied to a liquid crystal material having a dielectric anisotrophy to transmit or shut off a light, thereby displaying a picture or an image. Unlike display devices that generate light internally, such as an electro-luminescence (EL) device, a cathode ray tube (CRT), a light emitting diode (LED) and so on, LCDs use external light rather than generating light internally.
LCD devices are largely classified into transmissive type devices and reflective type devices, depending on the method of utilizing light. Transmissive type LCDs include a liquid crystal panel having a liquid crystal material injected between two transparent substrates and a backlight unit for supplying light to the liquid crystal panel. However, it is difficult to make a transmissive LCD with thin thickness and light weight. Moreover, backlight units of transmissive LCDs have excessive power consumption.
On the other hand, reflective type LCDs includes a reflective liquid crystal display panel
10
that transmits and reflects natural light and peripheral light to and from the display screen without a backlight. As shown in
FIG. 1
, reflective liquid crystal panel
10
consists of a liquid crystal panel
2
in which a liquid crystal material is injected between two transparent substrates, and a reflector
4
arranged at the rear side of the liquid crystal panel
2
or arranged at the interior of the liquid crystal panel to reflect a light toward the viewing side. This reflective LCD reflects natural light or peripheral light by means of the reflector
4
to display a picture or an image. However, the reflective LCD has a considerably low brightness level when natural light or peripheral light is not sufficient. An observer cannot view the display image at such low brightness levels. In order to solve this problem, there has been suggested a reflective LCD using an auxiliary light source other than natural light.
FIG. 2
shows a reflective LCD disclosed in U.S. Pat. No. 5,477,239. Referring to
FIG. 2
, the conventional reflective LCD shown includes a display module
24
attached pivotally to a main body
28
. The display module
24
houses a reflective liquid crystal display panel
22
, and auxiliary light sources
26
a
and
26
b
. Auxiliary light sources
26
a
and
26
b
are line light sources at the left and right sides of the reflective liquid crystal display panel
22
. Each auxiliary light source
26
a
and
26
b
is installed in such a manner to be opened and closed on the display module
24
, and to radiate light onto the surface of the reflective liquid crystal display panel
22
to the exterior of the display module
24
. A film (not shown) is adhered to an upper glass substrate of the reflective liquid crystal display panel
22
. This film includes a number of minute structures for reflecting light received at an inclination angle from the auxiliary light sources
26
a
and
26
b
toward the display screen of the reflective liquid crystal display panel
22
. Each of the minute structures must have a different inclination angle and height at every position so that a light can be uniformly received at the display screen of the reflective liquid crystal display panel
22
. Because of this, there is difficulty in designing and fabricating the minute structures. Because additional area is required for the display module
24
to house the auxiliary light sources
26
a
and
26
b
, the effective display area of the liquid crystal display panel
22
is reduced and the display module
24
is enlarged. Moreover, light incidence efficiency is low because of the difference in the quantity of light incident to the reflective liquid crystal display panel
22
at different positions. The quantity of light thus depends on the distance from the auxiliary light sources
26
a
and
26
b
to the position on the liquid crystal display panel
22
.
FIG. 3
shows a reflective LCD disclosed in U.S. Pat. No. 5,091,873. Referring to
FIG. 3
, the conventional reflective LCD includes a display module
34
installed pivotally at a main body
38
and mounted with a reflective liquid crystal display panel
32
, and a light source
40
mounted releasably on the main body
38
. The light source
40
includes a lamp
42
for generating light and a reflector
44
for reflecting light radiated from the lamp
42
toward the reflective liquid crystal display panel
32
, thereby radiating light onto the display screen of the liquid crystal display panel
32
. However, the main body
28
of the reflective LCD is bulky and the structure is complicated because of the light source
40
. Moreover, light incidence efficiency is low because of the difference in the quantity of light incident to the liquid crystal display panel
32
. The quantity of light varies with the distance between the reflector
44
and the reflective liquid crystal display panel
32
.
As described above, conventional reflective LCDs have the disadvantage that light cannot be uniformly radiated onto the display screen because of the location of the auxiliary light source. Moreover, because of the added weight and size of the auxiliary light source, it is difficult to make a product using a conventional reflective LCD that is light weight and small in dimension.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an auxiliary light source unit for a reflective liquid crystal display (LCD) that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an auxiliary light unit for a reflective liquid crystal display that is adapted to radiate light uniformly.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an auxiliary light source apparatus for a reflective liquid crystal display according to an embodiment of the present invention includes a main body; a reflective display module connected pivotally to the main body; and an auxiliary light source, the auxiliary light source being opened and closed from and to the reflective display module, for radiating light onto a display area of the reflective display module.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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patent: 4561044 (1985-12-01), Ogura et al.
patent: 5379201 (1995-01-01), Friedman
patent: 5477239 (1995-12-01), Busch et al.
patent: 5615945 (1997-04-01), Tseng
patent: 5803572 (1998-09-01), Brada
patent: 5822546 (1998-10-01), George
patent: 5868487 (1999-02-01), Polley et al.
patent: 6049410 (2000-04-01), Nakagaki et al.
patent: 6262884 (2001-07-01), Hwang et al.
patent: 6330386 (2001-12-01), Wagner et al.
patent: 6367946 (2002
LG. Philips LCD Co. Ltd.
McKenna Long & Aldridge LLP
Parker Kenneth
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