Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-11-26
2004-07-13
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S154000
Reexamination Certificate
active
06762817
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 2001-74365 filed on Nov. 27, 2001, which is hereby incorporated by reference as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (hereinafter, as LCD) device, and more particularly to the liquid crystal display device having an injection opening with an improved structure in which photo-sensitive encapsulation material and sufficiently exposed with the light in order to prevent the non-hardening of the encapsulation material caused by insufficient light exposure and prevent cracks of the encapsulation material caused by a step-compensating pattern of the injection opening.
2. Discussion of the Related Art
A liquid crystal display device is a transmission flat panel display device and is applied to various electronic equipments such as a mobile phone, PDA and notebook computer. Of the flat panel display devices, the LCD is most useful because of characteristics such as light weight, smaller size and a high image quality. Moreover, as the request for a digital TV or high image quality TV and panel type TV has increased research in the field of large area LCDs is more active.
Generally, LCDs may be divided into several types based on the operation mode of the liquid crystal molecules. Of the several types the TFT (Thin Film Transistor) type (TFT-LCD) is mainly used because of the fast response time and the reduced residual image.
Referring to
FIG. 1
, the TFT-LCD includes a lower substrate
3
, upper substrate
5
and liquid crystal layer
17
therebetween. A plurality of gate lines
11
and data lines
13
are arranged in the vertical and horizontal directions on the lower substrate
3
to define a plurality of picture elements (pixels). The gate lines
11
and data lines
13
are electrically connected with an outer driving device (not shown) through pads
12
and
14
, respectively, in a non-displaying region of the lower substrate
3
. A TFT
15
is disposed in each pixel. A scanning signal is applied to the TFT
15
through the gate line
11
, so that the TFT
15
is switched to apply an image signal to the liquid crystal layer
17
from the data line
13
.
A sealing unit
7
on which sealing material is deposited is formed at the outer portion of the lower substrate
3
and upper substrate
5
, thereby the lower substrate
3
and upper substrate
5
are attached each other. As shown in the figure, a black matrix
9
is formed in a region corresponding to the sealing unit
7
to block light through the region. The black matrix
9
is formed on the upper substrate
5
. Though the black matrix
9
is disposed only the region corresponding to the sealing unit
7
in the figure, the black matrix
9
may be disposed such that the area between the pixels and TFT active area to block the light through non-displaying region.
In the figure, reference numeral
20
designates a liquid crystal injection opening for injecting liquid crystal between the attached lower and upper substrates
3
and
5
. After injecting the liquid crystal through the liquid crystal injection opening
20
, the liquid crystal injection opening
20
should be encapsulated by encapsulation material
22
. Because the encapsulation material
22
is the photo-sensitive material, the encapsulation material
22
filled inside the liquid crystal injection opening
20
is hardened by exposure to light such as ultraviolet light.
A plurality of patterns
24
are disposed at the injection opening
20
. The patterns
24
are the step-compensating patterns for preventing the generation of the defection in the TFT-LCD as steps are generated by the TFT or pixel electrode (not shown) formed in the pixel region.
Hereinafter, the TFT-LCD with the above composition will be described in more detail with reference to FIG.
2
. In the figure, the region of the TFT-LCD where the image is actually displayed and the liquid crystal injection opening area are separated for convenience of description.
As shown in the figure, a gate electrode
31
is formed in the display region on the lower substrate
3
and a gate insulating layer
32
is deposited over the whole substrate
3
. A semiconductor layer
34
is formed on the gate insulating layer
32
and activated by the scan signal applied to the gate electrode
31
to form a channel layer. Source/drain electrodes
36
are formed over the semiconductor layer
34
. The source/drain electrodes
36
are electrically connected to the pixel electrode
38
in the region of the pixel where the image is actually displayed to apply the signal from the source/drain electrodes
36
to the pixel electrode
38
when the semiconductor layer
34
is activated. A passivation layer
39
is deposited over the source/drain electrodes
36
and the pixel electrode
38
.
An alignment layer (not shown) is deposited over the passivation layer
39
, to align the liquid crystal molecules in the liquid crystal layer
17
.
A step compensating pattern
24
is formed on the gate insulating layer
32
in the liquid crystal injection opening area. This step compensating pattern
24
compensates the step caused by the pixel electrode
38
. The step compensating pattern
24
is mainly made of the semiconductor material so that the pattern
24
is formed by the same process as the semiconductor layer
34
of the TFT.
The black matrix
9
, a light-blocking element, and the color filter layer
42
are formed on the upper substrate
5
. As shown in the figure, the black matrix
9
, which is made of the material such as Cr, CrOx or Cr/CrOx, is formed in the TFT area of the pixel region, above the gate line, the data line, and the liquid crystal injection opening area. Further, a common electrode
44
is formed over the black matrix
9
and the color filter layer
42
to operate the liquid crystal molecules of the liquid crystal layer
17
as the signals are applied to the liquid crystal layer
17
through the TFT. The alignment layer is deposited on the common electrode
44
to align the liquid crystal molecules.
Spacers
50
are scattered between the lower substrate
3
and the upper substrate
5
to maintain a uniform cell gap and then the lower substrate
3
and the upper substrates
5
are sealed. The liquid crystal is injected between the sealed substrates
3
and
5
through the liquid crystal injection opening to form the liquid crystal layer
17
. Thereafter, the liquid crystal injection opening is encapsulated with the encapsulation material.
FIG. 3
shows an enlarged structure of a liquid crystal injection opening encapsulated by the encapsulation material. As shown in the figure, a plurality of step compensating patterns
24
are formed over the whole area of the liquid crystal injection opening and the encapsulation material
22
is filled at the liquid crystal injection opening area. The encapsulation material
22
is depicted as the portion hatched by points.
Although the encapsulation material
22
is not filled in the portion on the step compensating patterns
24
, as illustrated in
FIG. 3
to indicate clearly the encapsulation material and the step compensating patterns
24
, the encapsulation material in practice is also filled on the step compensating patterns
24
, as illustrated in FIG.
2
.
The encapsulation material
22
includes photo-sensitive material. Therefore, the encapsulation material
22
in the liquid crystal injection opening area is exposed to light, such as UV light, to harden the encapsulation material
22
to encapsulate the liquid crystal injection opening. In the other words, the UV light must be irradiated to the lower substrate
3
and upper substrate
5
. As shown in the figure, the black matrix
9
is formed on the upper substrate
5
in the liquid crystal injection opening area. Accordingly, it is impossible to expose sufficiently the encapsulation material with UV light because of the black matrix
9
blocks light irradiated through the upper substrate
5
. Generally, UV light having about 300 mj/cm
2
of light amount is ne
Choi Sie-Hyug
Lee Seung-Joo
Dudek James A.
LG.Philips LCD Co. , Ltd.
McKenna Long & Aldridge LLP
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