Illumination – Illuminated scale or dial – Illuminated through meter case
Reexamination Certificate
2000-10-20
2002-04-16
O'Shea, Sandra (Department: 2875)
Illumination
Illuminated scale or dial
Illuminated through meter case
C362S033000, C362S085000, C349S061000
Reexamination Certificate
active
06371622
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 1999-13183, 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 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. LCDs use an external light source, 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.
LCD devices are largely classified into transmissive type devices and reflective type devices, depending on the method of utilizing light. The transmissive type LCDs includes 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, the backlight units of transmissive LCDs have excessive power consumption.
On the other hand, reflective type LCDs include 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 unit. 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
2
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 the natural light or peripheral light is not sufficient. In order to solve this problem, there has been suggested a reflective LCD using auxiliary light source other than natural light.
FIG. 2
shows a reflective LCD employing a point light source disclosed in the magazine,
Nikkei Electronics Asia,
published in July 1998. Referring to
FIG. 2
, the conventional reflective LCD includes a reflective liquid crystal panel
12
, a support bar installed at one side of the reflective liquid crystal panel
12
, and an auxiliary light source
16
as a point light source installed at the edge of the support bar
14
. The auxiliary light source
16
radiates light onto the reflective liquid crystal display panel
12
from a certain distance by means of the support bar
14
. Because the auxiliary light source
16
of the reflective LCD has a point light source and because the support bar
14
is installed at the comer of the reflective liquid crystal panel
12
, the incidence angle of the light provided by the auxiliary source on the display screen is different at every incident position. Thus, the quantity of light at each incident position differs considerably on the reflective LCD device. Accordingly, the brightness of the reflective LCD is non-uniform because the LCD is not illuminated with a uniform quantity of light.
FIG. 3
shows a reflective LCD disclosed in U.S. Pat. No. 5,477,239. Referring to
FIG. 3
, the conventional reflective LCD shown includes a display module
24
pivotally attached to a main body. 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
. Each auxiliary light source
26
a
and
26
b
radiates light onto the surface of the reflective liquid crystal display panel
22
. 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 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 structure must have a different inclination angle and height so that a light can be uniformly received at the display screen of the reflective liquid crystal display panel
22
. The minute structures are difficult to design and to fabricate because of the plurality of inclination angles required. Moreover, 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. Light incidence efficiency is low because the quantity of light incident to the reflective liquid crystal display panel
22
at different positions depends upon the distance from the auxiliary light sources
26
a
and
26
b
to each position on the liquid crystal display panel
22
.
FIG. 4
shows a reflective LCD disclosed in U.S. Pat. No. 5,091,873. Referring to
FIG. 4
, the conventional reflective LCD includes a display module
34
pivotally attached to 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 reflective LCD increases the bulk of the main body
38
, and the light source
40
complicates the structure.
As described above, in conventional reflective LCDs, it is difficult for light to be uniformly radiated onto the display screen, because of the location of the auxiliary light source. Moreover, it is difficult to make a product using a conventional reflective LCD that is light weight and small in dimension because of the need for an auxiliary light source.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an auxiliary light source unit for 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.
A further object of the present invention is to provide an auxiliary light unit for a reflective liquid crystal display that permits the liquid crystal display to be light weight and small in dimension.
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 installed pivotally at the main body; a support member opened and closed
LG. Philips LCD Co. Ltd.
Long Aldridge & Norman LLP
O'Shea Sandra
Sawhney Hargobind S.
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