Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-06-11
2004-08-24
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C347S107000
Reexamination Certificate
active
06781649
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a liquid crystal display device and a process for making the same.
BACKGROUND OF THE INVENTION
FIG. 9
shows an example of conventional liquid crystal display devices. This liquid crystal display device includes a first and a second substrates
41
,
42
. The first and the second substrates
41
,
42
are disposed in parallel to each other.
The first substrate
41
includes an upper surface
41
a
provided with a polarizer plate
45
and a retardation plate
46
. The polarizer plate
45
allows penetration of light rays that vibrate only in a specific direction. The polarizer plate
45
restricts entry of the light rays from the outside to the first substrate
41
or exit of the light rays from the first substrate
41
. The retardation plate
46
is disposed between the first substrate
41
and the polarizer plate
45
. The retardation plate
46
compensates for interference colors caused by birefringence at the liquid crystal. The retardation plate
46
enhances the viewing angle.
The first substrate
41
includes a lower surface
41
b
provided with a color filter layer
47
. The color filter layer
47
may comprise a water absorptive resin, for example. The color filter layer
47
includes filter strips
47
R,
47
G,
47
B. The filter strips
47
R,
47
G,
47
B are colored red, green and blue, respectively. The filter strips
47
R,
47
G,
47
B are arranged in parallel to each other in a widthwise direction.
The color filter layer
47
has a lower surface provided with a plurality of transparent electrodes
51
in the form of strips. The transparent electrodes
51
are arranged in corresponding relationship with filter strips
47
R,
47
G,
47
B. The second substrate
42
has an upper surface
42
a
provided with a plurality of reflective electrodes
53
in the form of strips which extend perpendicularly to the transparent electrodes
51
.
A liquid crystal layer
43
filled with liquid crystal is disposed between the first and the second substrates
41
,
42
. The liquid crystal layer
43
is surrounded by a seal member
55
. Pixels are provided at the intersections between the transparent electrodes
51
and the reflective electrodes
53
in the liquid crystal layer
43
. The pixels of the liquid crystal layer
43
are arranged in a matrix. A surface of the transparent electrodes
51
and a surface of the reflective electrodes
53
are covered, respectively, with an alignment films
54
A,
54
B. These alignment films
54
A,
54
B determine the twist of liquid crystal (liquid crystal molecules).
Light rays from the outside enter the above-described liquid crystal display device and travel through the polarizer plate
45
, the retardation plate
46
, the first substrate
41
, the color filter layer
47
, the transparent electrodes
51
and the liquid crystal layer
43
. After travelling through the liquid crystal layer
43
, the light rays are reflected upwardly by the reflective electrodes
53
. The light rays reflected upwardly, then, travel back through the same path to be emitted to the front side of the liquid crystal display device.
The filter strips
47
R,
47
G,
47
B of the color filter layer
47
provides corresponding colored regions
48
R,
48
G,
48
B on the surface of the color filter layer
47
, as shown in the FIG.
10
. The colored regions
48
R,
48
G,
48
B are strips provided in parallel to each other in a widthwise direction. Each of the filter strips
47
R,
47
G,
47
B is provided when a color ink is supplied to the water absorptive resin of the color filter layer
47
by the ink-jet method, for example.
In the ink-jet method, an ink-jet printhead
57
is first arranged on a surface of the water absorptive resin applied on the surface
41
b
of the first substrate
41
, as shown in the FIG.
11
. Then, nozzles
57
R,
57
G,
57
B of the ink-jet printhead
57
jet red, green or blue inks, respectively. In this way, the water absorptive resin is impregnated with the color ink. Each of generally circular dots
58
is provided by a color ink droplet on a surface of the color filter layer
47
, as shown in the FIG.
12
.
The ink-jet printhead
57
, then, translates to the next row as viewed perpendicularly to the paper plain of the
FIG. 12
, and jets an ink. Thereby, a plurality of dots
58
are arranged partially overlapping with each other, providing the colored regions
48
R,
48
G,
48
B. The diameter of the dots
58
may be approximately 90 &mgr;m.
The size of the dots
58
may vary due to the state or the amount of the color ink jetted. When the diameter of the dots
58
varies by 10%, irregularities in the dot diameter will be in a range of approximately 81-99 &mgr;m. As a result, when two dots between adjacent colored regions
48
R,
48
G,
48
B are both diametrically smallest, the size of the clearance therebetween (indicated as A in the
FIG. 12
) is as large as about 9 &mgr;m at the maximum.
When the dots have such diametrical irregularities in the colored regions
48
R,
48
G,
48
B, clearances at boundaries of adjacent colored regions
48
R,
48
G,
48
B may become relatively large. The boundaries between the adjacent colored regions
48
R,
48
G,
48
B undulate due to the clearances. Therefore, in the liquid crystal display device incorporating the color filter layer
47
having such clearances and undulations, the filter strips
47
R,
47
G,
47
B may not suitably mix different colors, thereby failing to provide proper color representation. The clearances and the undulations also deteriorate the image quality.
In order to eliminate the clearances and the undulations described above, a black matrix that intercepts light may be provided at the boundaries of the filter strips
47
R,
47
G,
47
B. However, formation of a black matrix may require photolithography, the manufacturing process may become complex, consequently resulting in an increase of production time and cost. Other methods may include providing a barrier wall or water repellent treatment at the boundaries of the filter strips
47
R,
47
G,
47
B on a surface of the water absorptive resin
56
for preventing color ink deposition. However, these methods also require time and increase the cost.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a liquid crystal display device which is capable of eliminating or at least reducing the problems described above.
In accordance with a first aspect of the present invention, there is provided a liquid crystal display device comprising: a first and a second substrates disposed in parallel to each other; a liquid crystal layer disposed between the two substrates and filled with liquid crystal; and a color filter layer disposed on a surface of the first substrate facing the second substrate;
wherein a surface of the color filter layer is provided with plural filter strips each retaining a respective color ink; and
wherein each of the filter strips includes plural columns of and plural rows of generally circular dots arranged in a strip or rectangle, each of the dots being provided by a color ink droplet.
Preferably, the color filter layer may comprise a water absorptive resin.
Preferably, each of the filter strips may be provided by impregnating the water absorptive resin with a respective color ink.
Preferably, each of the dots may be 20-40 &mgr;m in diameter.
Preferably, adjacent ones of the dots may partially overlap each other.
Preferably, the color inks may include red, green and blue inks.
Preferably, the liquid crystal in the liquid crystal layer may be controlled by voltage application in a normally black mode.
In accordance with a second aspect of the present invention, there is provided a process for making a liquid crystal display device which comprises: a first and a second substrates disposed in parallel to each other; a liquid crystal layer disposed between the two substrates and filled with liquid crystal; and a color filter layer disposed on a surface of the first substrate facing the second substrate; the process comprising the steps of:
app
Fujimoto Hisayoshi
Onishi Hiroaki
Di Grazio Jeanne Andrea
Kim Robert H.
Rohm & Co., Ltd.
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