Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-07-31
2003-09-02
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S113000
Reexamination Certificate
active
06614496
ABSTRACT:
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 device and a method of manufacturing the same.
2. Description of Related Art
In general, liquid crystal displays are divided into transmissive LCD devices and reflective LCD devices according to whether the display uses an internal or an outer light source.
A typical transmissive LCD device comprises a liquid crystal panel and a back light device. The liquid crystal panel includes upper and lower substrates with a liquid crystal layer interposed therebetween. The upper substrate has a color filter, and the lower substrate has a thin film transistor (TFT) as a switching element. An upper polarizer is arranged on the upper substrate of the liquid crystal panel, and a lower polarizer is arranged between the lower substrate of the liquid crystal panel and the backlight device.
At this time, the two polarizers have a transmittance of 45%, the two substrates have a transmittance of 94%, the TFT array and the pixel have a transmittance of 65%, and the color filter has a transmittance of 27%. respectively. Therefore, the transmisive LCD device gets to have about a transmittance of 7.4% as seen in
FIG. 1
which shows a transmittance after light passes through each layers. For such a reason, the transmissive LCD device requires a high brightness and thus an electrical power consumption by the backlight device increases. In order to supply a sufficient power to the backlight device, a relatively heavy battery is employed, and there still exits a problem that the battery can not be used for a long time.
In order to overcome the problem described above, the reflective LCD has been developed. Since the reflective LCD device uses ambient light, it is easy to carry. Also, the reflective LCD device is superior in aperture ratio than the transmissive LCD device.
FIG. 2
is a plan view illustrating a typical reflective LCD device. As shown in
FIG. 2
, the reflective LCD device includes gate lines
6
and
8
arranged in a transverse direction, data lines
2
and
4
arranged in a longitudinal direction perpendicular to the gate lines
6
and
8
, and thin film transistors “S” (TFTs) near cross points of the gate line
8
and the data line
2
. Each of the TFTs “S” has a gate electrode
18
, a source electrode
12
and a drain electrode
14
. The data electrode
18
extends from the data line
2
, and the gate electrode
18
extends from the gate line
8
. The reflective LCD device further includes reflective electrodes
10
. The reflective electrode
10
is electrically connected with the drain electrode
14
through a contact hole
16
and is made of a metal having a good reflectance.
By the way, the reflective LCD device has a problem that it is affected by its surroundings. For example, the brightness of ambient light in an office differs largely from that of the outdoors. Also, even in the same location, the brightness of ambient light depends on the time of day (e.g., noon or dusk).
In order to overcome the problem described above, a transflective LCD device has been developed.
FIG. 3
shows a conventional transflective LCD device. As shown in
FIG. 3
, the conventional transflective LCD device includes gate lines
40
arranged in a transverse direction, data lines
20
arranged in a longitudinal direction perpendicular to the gate lines
40
, thin film transistors “T” (TFFs) located near the cross points of the gate and data lines
40
and
20
. Each of the TFTs “T” includes a gate electrode
34
, a source electrode
30
and a drain electrode
32
. The gate electrode
34
is extended from the gate line
40
, and the source electrode
30
is extended from the data line
20
. The conventional transflective LCD device further includes a reflective electrode
37
and a pixel electrode
39
connected with the drain electrode
32
through a contact hole
36
. The reflective electrode
37
has a light transmitting hole
104
for transmitting light.
A method of manufacturing the conventional transflective LCD device is explained in detail below.
FIGS. 4A through 4G
are processing views illustrating a method of manufacturing the conventional transflective LCD device. As shown in
FIG. 4A
, a metal layer is deposited on a transparent substrate
1
and patterned into a gate electrode
34
. As shown in
FIG. 4B
, a gate insulating layer
20
is formed on the exposed surface of the substrate
1
while covering the gate electrode
34
. The semiconductor layer
22
is formed over the gate electrode
34
. Sequentially, as shown in
FIG. 4C
, source and drain electrodes
30
and
32
spaced apart from each other are formed on the semiconductor layer
22
. Then, as shown in
FIG. 4D
, a first passivation film
24
is formed on the exposed surface of the substrate
1
while covering the source and drain electrodes
30
and
32
. A predetermined portion of the drain electrode
32
is exposed and thus a first contact hole
36
is formed. Next, as shown in
FIG. 4E
, an opaque conductive layer is deposited on the first passivation film
24
and patterned into a reflective electrode
37
, forming a light transmitting hole
104
and contacting the drain electrode
32
through the first contact hole
36
. As shown in
FIG. 4F
, a second passivation film
38
is formed on the exposed surface of the substrate while covering the reflective electrode
37
. A second contact hole
36
′ is formed at a location corresponding to the first contact hole
36
. Finally, as shownn in
FIG. 4G
, a transparent conductive layer is deposited on the whole surface of the substrate
1
and patterned into a pixel electrode
39
, contacting the reflective electrode
37
through the second contact hole
36
′. Therefore, most of the important components of the conventional transflective LCD device are completed. At this point, the step of depositing the second passivation film
38
is optional, and therefore the second passivation film
38
may be not formed so that the pixel electrode
39
may contact the reflective electrode
37
directly. However, when the step of depositing the second passivation film
38
is omitted, a line defect such as a line open of the reflective electrode
37
may occur due to an etchant during patterning the transparent conductive layer into the pixel electrode
39
.
As described above, the method of manufacturing the conventional transflective LCD device is very complex and thus requires a lengthy processing time. In order to reduce the number of the processes, if the step of forming the second passivation film
38
is omitted, as described above, there comes a problem that a line defect such as a line open of the reflective electrode
37
may occur due to an etchant during patterning the transparent conductive layer into the pixel electrode
39
. Therefore, the conventional method of the transflective LCD device leads to a low production yield.
For the foregoing reasons, there is a need for a method of manufacturing a transflective LCD device by a simple process.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a transflective liquid crystal display device which can be manufactured with a high production yield by a simple process and a method of manufacturing the same.
The preferred embodiments of the present invention provide a transflective LCD device having a good resolution.
In order to achieve the above object, a transflectuive liquid crystal display device according to a preferred embodiment of the present invention includes a first transparent substrate and a second transparent substrate. The second substrate has a color filter and spaced apart from the first transparent substrate. The transflective liquid crystal display device further includes a liquid crystal layer interposed between the first and second transparent substrate and a gate electrode arranged on the first transparent substrate. The transflective liquid crysta
Ahn Byung-Chul
Song In-Duk
LG. Philips LCD Co. Ltd.
Schechter Andrew
Ton Toan
LandOfFree
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