Coating processes – Nonuniform coating
Reexamination Certificate
2002-12-26
2004-05-04
Chowdhury, Tarifur R. (Department: 2871)
Coating processes
Nonuniform coating
C438S694000, C349S187000, C101S465000
Reexamination Certificate
active
06730356
ABSTRACT:
The present invention claims the benefit of Korean Patent Application No. 89294/2001 filed in Korea on Dec. 31, 2001, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for forming a pattern, and particularly, to a method and apparatus for forming a pattern capable of simplifying the fabrication process improving productivity when a liquid crystal display device is fabricated by a printing method.
2. Discussion of the Related Art
In general, a cathode-ray tube (CRT) monitor has been mainly used for displaying information in a TV and a computer. The CRT has a high image quality and high screen brightness, and thereby the CRT has been the main stream of the display devices. However, as the screen size is increased, the size and weight of the CRT monitor is greatly increased occupying a large space, and becoming impractical as a portable device.
Flat panel display devices, such as a liquid crystal display (LCD), plasma display panel (PDP), organic electro luminescence (EL), light emitting diode (LED) and field emission display (FED), have been developed for solving the above problems. Among these flat panel display devices, the LCD is highlighted since it has been widely used in notebook PC's or computer monitors, and it has low power consumption.
FIG. 1
is a cross-sectional view of a liquid crystal display device according to the related art. As shown in
FIG. 1
, the LCD device comprises an upper substrate
10
, a lower substrate
20
and a liquid crystal layer
30
formed therebetween. A color filter
11
, which generates colored light, comprising a black matrix
12
for preventing light leaking between pixels and a resin layer including dyes or pigments of red, green, and blue colors, and are formed on the upper substrate
10
. In addition, an over coat layer (not shown) may be formed on the color filter
11
for flattening the color filter
11
and improving bonding with an ITO, and a common electrode
13
, which is a transparent conductive material for applying a voltage to the liquid crystal layer
30
, are formed on upper part thereof. In addition, an alignment layer
14
a
for aligning liquid crystal molecules is formed on the common electrode
13
.
A thin film transistor (T) and a pixel electrode
21
, which is an electrode corresponding to the common electrode
13
, are formed on the lower substrate
20
. The thin film transistor (T) comprises a gate electrode
15
to which a scan signal is applied, an active layer
16
for transmitting data signals corresponding to the scan signal, a gate insulating layer
17
for electrically isolating the active layer
16
and the gate electrode
15
, a source electrode
18
a
formed on an upper part of the active layer
16
for applying a data signal, and a drain electrode
18
b
for applying the data signal to a pixel electrode
21
. The active layer
16
comprises a semiconductor layer
16
a
formed by depositing amorphous silicon (a-Si), and an ohmic contact layer
16
b
n+-doped on both upper sides of the semiconductor layer
16
a.
A passivation layer
19
for exposing a part of the drain electrode
18
b
is formed on the thin film transistor (T), and the pixel electrode
21
and the drain electrode
18
b
are electrically connected through the exposing portion. In addition, the pixel electrode
21
and the common electrode
13
are formed as transparent electrodes made of an ITO so that light can be transmitted, and a second alignment layer
14
b
for aligning the liquid crystal molecules is formed on an upper part of the pixel electrode
21
.
In order to fabricate the liquid crystal display device discussed above, a plurality of thin film deposition processes, photolithography processes and etching processes should be repeated. In order to fabricate the thin film transistor (T), the color filter
11
, and the black matrix
12
, a photoresist pattern is formed by an exposure process using a photoresist or a mask, and an etching process is performed thereafter. However, the above processes for forming the photoresist pattern are complex, and cost for fabricating the mask is increased as the substrate is increased. Therefore, a printing method by which the patterned resist can be formed without the exposing process has been recently suggested.
FIGS. 2A through 2D
are cross sectional views of a method and apparatus for forming a pattern using a gravure offset printing method according to the related art. As shown in
FIG. 2A
, resist is applied onto a cliché
24
on which a recess
23
is formed, thereafter, a doctor blade
32
flattens the cliché on which the resist is applied. At that time, the resist
31
is formed in the recess
23
, and any other resist remaining on the area is removed.
As shown in
FIG. 2B
, a roller
33
is rotated contacting the cliché
24
, and the resist
31
filled in the recess
23
of the cliché
24
is transferred onto the roller
33
.
As shown in
FIG. 2C
, a substrate
10
a
on which a pattern will be formed is loaded on a lower part of the roller
33
, and the roller
33
is rotated to re-transfer the resist
31
a
onto the substrate
10
a.
FIG. 2D
shows the resist pattern
31
a
formed on the substrate
10
a
through the above gravure offset printing process.
FIG. 3
is a planar view of a gravure offset printing apparatus according to the related art. As shown in
FIG. 3
, in the gravure offset printing apparatus, the cliché
24
, on which the concave recess
23
is formed, and a stage
25
, on which the substrate
10
a
for forming the pattern is disposed, are integrally constructed. The roller
33
is provided for transferring the resist pattern onto the substrate
10
a
from the cliché
24
. The roller
33
can be rotated and reciprocated between the cliché
24
and the stage
25
, and the roller
33
stained with the resist filled in the cliché
24
transfers the resist pattern onto the substrate in one rotation.
FIG. 4
is a cross-sectional view of the gravure printing apparatus taken along I-I′ of FIG.
3
. The cliché
24
, on which the recess
23
is formed, and the stage
25
are integrally formed, and the roller
33
located on an upper part of the cliché
24
moves between the cliché
24
and the stage
25
to form the resist pattern on the substrate
10
a
. In order to re-transfer the resist transferred from the cliché
24
onto the substrate
10
a
in one try, a width of the roller
33
should be the same or more as that of the substrate. Therefore, the size of the roller increases as the size of the liquid crystal panel is increased, and thereby cost for fabricating the roller is increased. When the resist is transferred onto the roller
33
from the cliché, the resist is not smoothly separated from the recess of the cliché. Therefore, some resist remains in the recess, and the surface of the resist transferred to the roller is not flat. Thereby, a gap between the substrate and the resist is formed when the resist is re-transferred onto the substrate. When the substrate is etched in the etching process, etchant flows into the gap and the part is etched unnecessarily. Therefore, a fatal error may occur in the display device which requires a pattern of high precision. Also, the resist remaining on the roller should be cleaned regularly.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method and apparatus for forming a pattern using a printing method that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide simplified fabrication processes and a printing apparatus for transferring a resist pattern onto a substrate after attaching the substrate on a cliché without a roller.
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 r
Kim Eu-Gene
Lee Dong-Hoon
Lee Jung-Jae
Nam Dae-Hyun
Chowdhury Tarifur R.
LG.Philips LCD Co. , Ltd.
Qi Mike
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