Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-10-11
2004-06-15
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S113000
Reexamination Certificate
active
06750932
ABSTRACT:
The present invention claims the benefit of Korean Patent Application No. 2001-63140, filed in Korea on Oct. 12, 2001, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and more particularly, to a transflective liquid crystal display (LCD) device that is used both in a transmissive mode and in a reflective mode.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device includes two substrates spaced apart and facing each other, and a liquid crystal material layer interposed between the two substrates. Each of the first and second substrates includes an electrode, whereby the electrodes of each of the first and second substrates face each other. When a voltage is applied to each of the electrodes, an electric field is induced between the electrodes. Accordingly, an alignment of the liquid crystal molecules of the liquid crystal material layer is changed by the varying intensity or direction of the induced electric field. Thus, the LCD device displays an image by varying transmittance of light through the liquid crystal material layer according to the arrangement of the liquid crystal molecules. However, since the liquid crystal display (LCD) device is not luminescent, an additional light source is required to display images.
The liquid crystal display device may be categorized into two different types depending upon the type of light source used; a transmissive type and a reflective type. In the transmissive type, a back light is positioned behind a liquid crystal panel, wherein light incident from the back light enters into the liquid crystal panel. Accordingly, an amount of light transmitted through the liquid crystal material layer is controlled by the alignment of the liquid crystal molecules. Thus, the substrates and the electrodes must be formed of transparent conductive materials. Since the transmissive liquid crystal display (LCD) device uses the back light as a light source, it can display bright images in dark surroundings. In addition, the light intensity of the back light must be increased since the amount of transmitted light is relatively small. Consequently, the transmissive liquid crystal display (LCD) device requires a relatively high power consumption due to the low light intensity of the back light.
In the reflective type LCD device, ambient sunlight or artificial light is used as a light source of the LCD device. The ambient light incident from the surroundings is reflected by a reflective plate of the LCD device according to the arrangement of the liquid crystal molecules. Since there is no back light, the reflective type LCD device has considerably lower power consumption than the transmissive type LCD device. However, the reflective type LCD device may not be suitable for use in places with low ambient light since an artificial light source would be required.
FIG. 1
is a cross-sectional view of a transflective LCD device according to the related art. In
FIG. 1
, transmissive electrodes
12
are formed along an inner surface of a first substrate
11
that includes a thin film transistor (not shown) electrically connected to each of the transmissive electrodes
12
. Reflective electrodes
13
are formed on the transmissive electrodes
12
, and each has a transmissive hole
13
a
exposing a portion of the transmissive electrode
12
. A first polarizer
14
is arranged along an outer surface of the first substrate
11
, thereby linearly polarizing incident light.
A second substrate
21
is spaced apart from and faces the first substrate
11
, and a color filter layer
22
is formed on an inner surface of the second substrate
21
. The color filter layer
22
is composed of three sub-color filters of red (R), green (G), and blue (B). Each of the sub-color filters correspond to each of the transmissive electrodes
12
. A common electrode
23
is formed on the color filter layer
22
, and is made of a conductive transparent material. A diffusing film
24
and a second polarizer
25
are subsequently arranged along an outer surface of the second substrate
21
, wherein a transmission axis of the second polarizer
25
is perpendicular to a transmission axis of the first polarizer
14
. A liquid crystal material layer
30
is disposed between the reflective electrodes
13
and the common electrode
23
.
In
FIG. 1
, a back light unit
40
is disposed beneath the first polarizer
14
, and is used as a light source during a transmissive mode of the transflective LCD device. The back light unit
40
includes a light guide panel
42
, a lamp
41
, a collimating sheet
43
, and a diffusing sheet
44
. The light guide panel
42
includes scattering patterns formed along a lower surface, thereby changing linear light of the lamp
41
into plane light.
In a transmissive mode, a first light “L
1
” generated from the back light unit
40
penetrates into the first polarizer
14
and through the first substrate
11
. In addition, the first light “L
1
” passes through the portion of the transmissive electrode
12
that corresponds to the transmissive hole
13
a
and through the liquid crystal material layer
30
. Then, the first light “L
1
” is transmitted through the common electrode
23
, the color filter layer
22
, the second substrate
21
, the diffusing film
24
, and the second polarizer
25
.
In a reflective mode, a second light “L
2
” incident from ambient surroundings, such as sunlight or artificial light, passes through the second polarizer
25
, the diffusing film
24
, the second substrate
21
, the color filter
22
, the common electrode
23
, and the liquid crystal material layer
30
. Then, the second light “L
2
” is reflected by the reflective electrode
13
and is transmitted back through the liquid crystal material layer
30
, the common electrode
23
, the color filter
22
, the second substrate
21
, the diffusing film
24
, and the second polarizer
25
.
By comparison, the transflective LCD device has lower reflectance than the reflective LCD device because of the transmissive hole
13
a
formed in the reflective electrode
13
. Specifically, in the reflective mode, light incident toward the transmissive hole
13
a
is transmitted to the back light unit
40
and is not reflected. In addition, the transflective LCD device has lower brightness than the transmissive LCD device in the transmissive mode since light incident toward the reflective electrode
13
from the back light unit
40
is reflected toward the back light unit
40
.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a transflective liquid crystal display (LCD) device that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a transflective liquid crystal display (LCD) device that improves brightness both in a transmissive mode and in a reflective mode.
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, a transflective liquid crystal display device includes a liquid crystal panel having a pixel electrode, wherein the pixel electrode includes a first reflective region and a first transmissive region, a patterned reflective panel adjacent to the liquid crystal panel, the patterned reflective panel having a second reflective region and a second transmissive region, and a back light unit adjacent to the patterned reflective panel, wherein the patterned reflective panel is movable along a direction parallel to the liquid crystal panel.
I
Kim Robert H.
LG.Philips LCD Co. , Ltd.
Morgan & Lewis & Bockius, LLP
Wang George Y.
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