Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2003-01-21
2004-09-07
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000
Reexamination Certificate
active
06788367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is relates to a liquid crystal display (LCD) device, more particularly to a liquid crystal display device having the best performance of contrast ratio and color saturation in the transmissive and reflective areas of color LCD by adjusting the thicknesses of two color filters on the lower and upper transparent substrates.
2. Description of the Prior Art
A color LCD [liquid crystal display] panel comprises two transparent substrates and a liquid crystal layer between the substrates. In general, a color filter is only placed on the transparent substrate opposite to TFTs (thin film transistors). It means that the color filter and TFTs are placed on different transparent substrates respectively opposite to each other.
For the transmissive-type or reflective-type color LCD, the presented color saturation is identical because the distance for light rays passing through a color filter in the whole liquid crystal panel is the same. But for the transflective-type color LCD, please refer to
FIG. 1
, when external light rays are sufficient to display figures or pictures on the screen, the color LCD will use external light rays
111
as the light source according to the reflection theory. So light rays pass through the color filter
13
twice in the reflective area
11
, which will present the higher color saturation. When external light rays are insufficient to display figures or pictures on the screen, the color LCD will use its back light (BL) source according to the transmissive theory. Then the light rays
121
pass through the color filter
13
once in the transmissive area
12
, which will present the lower color saturation in comparison to the reflective area
11
.
Because of the above reasons, when the transflective-type color LCD uses both of the transmissive and reflective display modes at the same time, the problem of different color saturation is produced. The methods that have been practically used in the industry are illustrated in FIG.
2
A and
FIG. 2B. A
method that the color filter in the reflective area
21
is thinner than the color filter in the transmissive area
22
is adopted. The reflective area
21
is in the left side of FIG.
2
A and the transmissive area
22
is in the right side of FIG.
2
A. If external light rays
211
, as the light source, are sufficient to display figures and pictures on the screen, the light rays
211
of the reflective area
21
will pass through the color filter
212
and be reflected by the reflective electrode on the elevated reflective layer
213
. Because of elevated reflective layer
213
with the bumps, many reflective light rays
214
will be produced according to the scattering theory to pass through the liquid crystal layer
23
and the color filter
212
to display figures and pictures on the screen. But when external light rays are insufficient to display figures and pictures on the screen, the LCD will use its BL
221
to pass through the liquid crystal layer
23
and the color filter
222
. Owing to the thickness t of color filter
212
be less than the thickness T of color filter
222
, it will generate the similar substantially color saturation in both of the reflective and transmissive areas under the thickness compensation theory.
Another method for making many hollow holes in the color filter at the reflective area is adopted in FIG.
2
B. The reflective area
26
is in the left side of FIG.
2
B and the transmissive area
27
is in the right side of FIG.
2
B. When external light rays
261
are sufficient to display figures and pictures on the screen, the LCD will use external light rays
261
as the light source. Therefore, the light rays
261
of the reflective area
26
will pass through the color filter
262
and be reflected by the reflective electrode on the elevated reflective layer
263
. Because of elevated reflective layer
263
with the bumps, many reflective light rays
264
will be produced according to the scattering theory to pass through the liquid crystal layer
28
and the color filter
262
to display figures and pictures on the screen. But when external light rays are insufficient, the LCD will use its BL
271
, passing through the liquid crystal layer
28
and the color filter
272
, to display figures and pictures on the screen. There are many small holes in the color filter
262
and there is not any small hole in the color filter
272
. It will generate the similar substantially color saturation in both of the reflective and transmissive areas by using the small holes in the color filter of reflective area.
It still exists the problem for aligning two glass substrates either using the method that the color filter in the reflective area is thinner than the color filter in the transmissive area or the method for making many hollow holes in the color filter at the reflective area. Especially due to the present LCD have quite small pixel; it is very difficult to align the reflective and transmissive areas of two glass substrates. The problem of different color saturation in the reflective and transmissive areas will be produced while there is a little deviation on the alignment.
SUMMARY OF THE INVENTION
In the light of the state of the art described above, it is an object of the present invention to provide a liquid crystal display (LCD) device with two color filters on the lower and upper transparent substrates which is immune to the problems of the conventional LCD device described above.
It is another object of this invention to provide a liquid crystal display device with two color filters on the lower and upper transparent substrates to present the same color saturation in the reflective and transmissive areas.
It is a further object of this invention to provide a liquid crystal display device with two color filters on the lower and upper transparent substrates to overcome the problem for disaligning the reflective and transmissive areas on the lower and upper transparent substrates.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a liquid crystal display device which includes a general aspect of the present invention a liquid crystal display device which includes a first substrate having a reflective area and a transmissive area, and a plurality or thin film transistors (TFTs) thereon; a dielectric layer on said first substrate; a first color filter on said dielectric layer; an elevated dielectric layer on said first color filter in said reflective area; a first electrode on said elevated dielectric layer in said reflective area and on said first color filter in said transmissive area, wherein the top surface of said first electrode in said reflective area is higher than the top surface of said first electrode in said transmissive area; a liquid crystal layer on said first electrode; a second electrode on said liquid crystal layer; a second color filter on said second electrode; and a second substrate on said second color filter.
Base on the idea described above, wherein said first and second substrates are transparent.
Base on the aforementioned idea, wherein the material of said dielectric layer is selected from the group consisting of SiO
2
, Si
3
N
4
and both.
Base on the idea described above, the material of said elevated dielectric layer is photopolymer.
Base on the aforementioned idea, wherein the thickness of said elevated dielectric layer is about 1~3 &mgr;m.
Base on the idea described above, wherein said first and second color filters comprise three non-overlapping color areas.
Base on the aforementioned idea, wherein said three color areas are red, green and blue.
Base on the idea described above, wherein the colors of identical areas on said first and second color filters are same.
Base on the aforementioned idea, wherein said first electrode is coated by using the sputter method.
Base on the idea described above, wherein the height of said first electrode on said elevated dielect
Chang Shih-Chang
Tsai Yaw-Ming
Lowe Hauptman & Gilman & Berner LLP
Ton Toan
Toppoly Optoelectronics Corp.
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