U.S. patent application number 11/256801 was filed with the patent office on 2006-02-16 for color liquid crystal display.
This patent application is currently assigned to HannStar Display Corporation. Invention is credited to Hung-Yi Hung, Chih-Chieh Lan, Yu-Fang Wang.
Application Number | 20060033863 11/256801 |
Document ID | / |
Family ID | 32322975 |
Filed Date | 2006-02-16 |
United States Patent
Application |
20060033863 |
Kind Code |
A1 |
Lan; Chih-Chieh ; et
al. |
February 16, 2006 |
Color liquid crystal display
Abstract
A color liquid crystal display includes a control circuit
located on a first transparent substrate. The control circuit
includes control devices and a chessboard-like circuit with
supporting areas. A passivation layer is located on the control
circuit and has contact windows to expose electrodes of the control
devices. A color filter layer is located on the passivation layer
and pixel electrodes are located on the color filter layer. The
pixel electrodes are electrically connected to the electrodes of
the control devices through the contact windows. First photoresist
layers are located on the supporting areas and the control devices,
and second photoresist layers are located on the first photoresist
layers. A common electrode is located on a surface of a second
transparent substrate that faces the first transparent substrate. A
liquid crystal layer is located between the first and the second
transparent substrates.
Inventors: |
Lan; Chih-Chieh; (Taipei,
TW) ; Hung; Hung-Yi; (Taipei, TW) ; Wang;
Yu-Fang; (Taipei, TW) |
Correspondence
Address: |
THE WEBB LAW FIRM, P.C.
700 KOPPERS BUILDING
436 SEVENTH AVENUE
PITTSBURGH
PA
15219
US
|
Assignee: |
HannStar Display
Corporation
Taipei
TW
|
Family ID: |
32322975 |
Appl. No.: |
11/256801 |
Filed: |
October 24, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10457966 |
Jun 10, 2003 |
6958792 |
|
|
11256801 |
Oct 24, 2005 |
|
|
|
Current U.S.
Class: |
349/110 |
Current CPC
Class: |
G02F 1/136209 20130101;
G02F 1/13394 20130101 |
Class at
Publication: |
349/110 |
International
Class: |
G02F 1/1333 20060101
G02F001/1333 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 2002 |
TW |
91134380 |
Claims
1. A color liquid crystal display, comprising: a first transparent
substrate; a control circuit located on the first transparent
substrate, the control circuit being constituted by control devices
and a chessboard-like circuit and the chessboard-like circuit
having supporting areas; a passivation layer located on the control
circuit and having contact windows to expose electrodes of the
control devices, respectively; a color filter layer located on the
passivation layer; pixel electrodes located on the color filter
layer, and the pixel electrodes electrically connecting to the
electrodes of the control devices through the contact windows,
respectively; first photoresist layers respectively located on the
supporting areas and the control devices; second photoresist layers
respectively located on the first photoresist layers; a second
transparent substrate; a common electrode located on a surface
facing the first transparent substrate of the second transparent
substrate; and a liquid crystal layer located between the first and
the second transparent substrates.
2. The color liquid crystal display of claim 1, wherein the first
photoresist layers are black resin layers and the second
photoresist layers are transparent photoresist layers.
3. The color liquid crystal display of claim 1, wherein the optical
density of the black resin layers is greater than 3.
4. The color liquid crystal display of claim 2, wherein the black
resin layers are non-photosensitive black resin layers.
5. The color liquid crystal display of claim 4, wherein a thickness
of the non-photosensitive black resin layers is about 0.2-1.5
.mu.m.
6. The color liquid crystal display of claim 4, wherein the
transparent photoresist layers are positive photosensitive in
type.
7. The color liquid crystal display of claim 4, wherein the
transparent photoresist layers are negative photosensitive in
type.
8. The color liquid crystal display of claim 2, wherein the
transparent photoresist layers are negative photosensitive in type
while the black resin layers are negative photosensitive black
resin layers.
9. The color liquid crystal display of claim 8, wherein a thickness
of the black resin layers is about 1-2 .mu.m.
10. The color liquid crystal display of claim 1, wherein the first
photoresist layers are transparent photoresist layers and the
second photoresist layers are black resin layers.
11. The color liquid crystal display of claim 10, wherein the
transparent photoresist layers are negative photosensitive in type
while the black resin layers are negative photosensitive black
resin layers.
12. The color liquid crystal display of claim 11, wherein a
thickness of the black resin layers is about 1-2 .mu.m.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to a structure of a color
liquid crystal display (LCD) and a method of producing the same.
More particularly, the present invention relates to a method of
utilizing dual-layer photoresist to form black matrixes and spacers
on a control circuit substrate and the LCD structure fabricated by
the same method.
[0003] 2. Description of Related Art
[0004] Liquid crystal is a material having properties between those
of crystal and liquid. The alignment of the liquid crystal
molecules varies with external stimulation such as an electrical
field generated by an applied voltage. Hence, this feature of the
liquid crystal molecules can be utilized to create a display
unit.
[0005] Liquid crystal material was discovered in 1888, and
applications thereof first appeared in 1963. However, the value of
the commercial application was not proved until Sharp in Japan
developed a liquid crystal display applied in a calculator.
Japanese companies have continued to develop the technology and
improve the product's function. Development and improvement have
made the liquid crystal display widely applicable.
[0006] The thin-film-transistor (TFT) array substrate and the color
filter substrate are fabricated separately and then are assembled
in current technology for producing a color thin film transistor
liquid crystal display (TFT-LCD). As a result of the limitations of
assembling precision, the aperture ratio of the TFT-LCD cannot be
effectively increased. Based on the limitations described above,
the latest developments have led to a color filter layer being
formed on a TFT array substrate by photolithography to form a color
filter on array (COA) substrate. The subsequent process is only to
assemble the COA substrate and a transparent indium tin oxide (ITO)
substrate, with no precision limit on the assembling step.
Therefore, the aperture ratio of the TFT-LCD can be greatly
increased to decrease the power consumption. This is the
application trend for future portable products.
[0007] The black matrixes and photoresist spacers have to be
separately formed by two photolithography steps for a TFT-LCD made
by the COA technique described above. If the black matrixes and the
photoresist spacers are formed by only one photolithography step,
only black resin of the negative photosensitive type can be used
and the thickness of black resin needed is at least 5 .mu.m.
However, the light transmittance and the photosensitivity of the
black resin are reduced and the required exposure dose is about 250
mj/cm.sup.2. In comparison with black resin, the required exposure
dose is only about 19 mj/cm.sup.2 for a common transparent
photoresist. Therefore, a very long exposure time is needed for
patterning the black resin to form an ideal pattern, and the
throughput of the stepper is seriously affected. Moreover, spacers
are in charge of maintaining the distance between two transparent
substrates; hence certain requirements exist on the shape and the
height of the spacers. Consequently, the process margin for
developing the black resin of the negative photosensitive type is
very narrow.
SUMMARY OF THE INVENTION
[0008] It is therefore an objective of the present invention to
pattern the black resin and the transparent photoresist by only one
photo mask to form black matrixes and spacers simultaneously.
[0009] It is another objective of the present invention to provide
a method of forming black matrixes and spacers on a control circuit
substrate by double layers of photoresist to increase the
throughput of products.
[0010] It is still another objective of the present invention to
provide a method of forming black matrixes and spacers on a control
circuit substrate by dual-layer photoresist to increase the process
margin.
[0011] It is also another objective of the present invention to
provide a color LCD made by the method mentioned above.
[0012] In accordance with the foregoing and other objectives of the
present invention, a method of utilizing dual-layer photoresist to
form black matrixes and spacers on a control circuit substrate is
provided. A control circuit, made of control devices and a
chessboard-like circuit having supporting areas, is located on a
control circuit substrate. A passivation layer is located on the
control circuit, and contact windows are formed therein to expose
electrodes of the control devices, respectively. This method
comprises the following steps. A color filter layer and pixel
electrodes are sequentially formed on the control circuit
substrate. The pixel electrodes electrically connect to the
electrodes of the control devices through the contact windows,
respectively. A first photoresist is formed on the control circuit
substrate and then is soft-baked. The thickness of the first
photoresist is large enough to make the optical density of the
first photoresist be greater than 3. A second photoresist is formed
on the first photoresist and then is soft-baked. Next, the second
photoresist and the first photoresist are patterned to form
spacers, respectively on the supporting areas, and black
matrixeses, respectively on the control devices. The second
photoresist and the first photoresist are hard-baked.
[0013] According to a preferred embodiment of the present
invention, the first photoresist is black resin and the second
photoresist is transparent photoresist. When the first photoresist
is non-photosensitive black resin, the second photoresist is
positive or negative photosensitive photoresist. The thickness of
the non-photosensitive black resin is about 0.2-1.5 .mu.m to let
the optical density of the black resin be greater than 3. The
method of patterning the first and the second photoresist comprises
the following steps. The second photoresist is exposed and then is
developed by a developer solution. The developer solution is also
used to remove the first photoresist uncovered by the second
photoresist during developing the second photoresist.
[0014] According to another preferred embodiment of the present
invention, the first photoresist is a black resin and the second
photoresist is a transparent photoresist. When the first
photoresist is a negative photosensitive black resin, the second
photoresist is negative photosensitive transparent photoresist. The
thickness of the negative photosensitive black resin is about 1-2
.mu.m to let the optical density of the black resin be greater than
3. The second and the first photoresist are patterned by
photolithography.
[0015] In accordance with the foregoing and other objectives of the
present invention, a method of utilizing dual-layer photoresist to
form black matrixes and spacers on a control circuit substrate is
provided. A control circuit, made of control devices and a
chessboard-like circuit having supporting areas, is located on a
control circuit substrate. A passivation layer is located on the
control circuit, and contact windows are formed therein to expose
electrodes of the control devices, respectively. This method
comprises the following steps. A color filter layer and pixel
electrodes are sequentially formed on the control circuit
substrate. The pixel electrodes electrically connect to the
electrodes of the control devices through the contact windows,
respectively. A first photoresist is formed on the control circuit
substrate and then is soft-baked. A second photoresist is formed on
the first photoresist and then is soft-baked. The thickness of the
second photoresist is large enough to make the optical density of
the second photoresist be greater than 3. Next, the second
photoresist and the first photoresist are patterned to form
spacers, respectively on the supporting areas, and black
matrixeses, respectively on the control devices, by
photolithography. The second photoresist and the first photoresist
are hard-baked.
[0016] According to another preferred embodiment of the present
invention, the first photoresist is transparent photoresist and the
second photoresist is black resin. When the second photoresist is a
negative photosensitive black resin, the first photoresist is
negative photosensitive transparent photoresist. The thickness of
the negative photosensitive black resin is about 1-2 .mu.m to let
the optical density of the black resin be greater than 3.
[0017] In accordance with the foregoing and other objectives of the
present invention, a color liquid crystal display is provided. The
color liquid crystal display comprises a first transparent
substrate, a control circuit, a passivation layer, a color filter
layer, pixel electrodes, first photoresist layers, second
photoresist layers, a second transparent substrate, a common
electrode, and a liquid crystal layer. The control circuit, made of
control devices and a chessboard-like circuit having supporting
areas, is located on the first transparent substrate. A passivation
layer is located on the control circuit, and contact windows are
located therein to expose electrodes of the control devices,
respectively. A color filter layer and pixel electrodes are
sequentially located on the control circuit substrate. The pixel
electrodes electrically connect to the electrodes of the control
devices through the contact windows, respectively. The first
photoresist layers are respectively located on the supporting areas
and the control devices. The second photoresist layers are
respectively located on the first photoresist layers. The common
electrode is on a surface, which faces the first transparent
substrate, of the second transparent substrate. The liquid crystal
layer is located between the first and the second transparent
substrates.
[0018] According to a preferred embodiment of the present
invention, the first photoresist is black resin and the second
photoresist is transparent photoresist. When the first photoresist
is non-photosensitive black resin, the second photoresist is
positive or negative photosensitive photoresist. The thickness of
the non-photosensitive black resin is about 0.2-1.5 .mu.m to let
the optical density of the black resin be greater than 3. The
method of patterning the first and the second photoresist comprises
the following steps. The second photoresist is exposed and then is
developed by a developer solution. The developer solution is also
used to remove the first photoresist uncovered by the second
photoresist during developing the second photoresist.
[0019] According to another preferred embodiment of the present
invention, the first photoresist is a black resin and the second
photoresist is a transparent photoresist. When the first
photoresist is a negative photosensitive black resin, the second
photoresist is negative photosensitive transparent photoresist. The
thickness of the negative photosensitive black resin is about 1-2
.mu.m to let the optical density of the black resin be greater than
3. The second and the first photoresist are patterned by
photolithography.
[0020] According to this preferred embodiment of the present
invention, the first photoresist is transparent photoresist and the
second photoresist is black resin. When the second photoresist is a
negative photosensitive black resin, the first photoresist is
negative photosensitive transparent photoresist. The thickness of
the negative photosensitive black resin is about 1-2 .mu.m to let
the optical density of the black resin be greater than 3.
[0021] In the foregoing, the invention utilizes the much-improved
light transmittance and photosensitivity properties of the
transparent photoresist rather than those of the black resin to
decrease the thickness needed by black resin used in the prior
arts. Hence, the exposure time needed for the black resin used in
the prior arts can be greatly reduced to increase greatly the
product throughput.
[0022] It is to be understood that both the foregoing general
description and the following detailed description are examples,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0024] FIG. 1 is a vertical view of a control circuit substrate
according to one preferred embodiment of this invention;
[0025] FIGS. 2 and 3 are cross-sectional diagrams of utilizing
dual-layer photoresist to form black matrixes and spacers on a
control circuit substrate in FIG. 1 according to a preferred
embodiment of this invention; and
[0026] FIGS. 2 and 4 are cross-sectional diagrams of utilizing
dual-layer photoresist to form black matrixes and spacers on a
control circuit substrate in FIG. 1 according to another preferred
embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0028] As stated above, this invention provides a method of
utilizing dual-layer photoresist to form black matrixes and spacers
on a control circuit substrate and the LCD structure fabricated by
the same method to increase greatly the product throughput.
[0029] FIG. 1 is a vertical view of a control circuit substrate
according to one preferred embodiment of this invention. In FIG. 1,
a control circuit, such as a thin film transistor (TFT) array, is
formed on a transparent substrate 100. Each TFT in the TFT array
comprises gate 110, source 120 and drain 130. Each gate 110
electrically connects to a gate line 115 made by a first metal
layer. Each source 120 electrically connects to a data line 125
made by a second metal layer. The data lines 125 cross over the
gate lines 115 to define pixels 135. Red (R), green (G) and blue
(B) color filters are respectively formed on each pixel 135 later,
and each TFT is respectively formed in a corner of each pixel 135.
Hence, a control circuit substrate is formed.
[0030] The black matrixeses are formed on the areas 145 above the
TFTs to prevent photocurrent occurring during the "off" state of
the TFTs. The spacers are formed on opaque areas such as supporting
areas 140 on the gate lines 115. The material of the gate lines 115
and the data lines 125 is metal, which is an opaque material.
Therefore, black matrixeses need not be formed on the gate lines
115 and the data lines 125 to compartment adjacent pixels 135. In
FIG. 1, the relative positions of the pixel electrodes 190 formed
later and the TFT are also displayed. The subsequent processes are
described in the following embodiments 1-2.
EMBODIMENT 1
[0031] FIGS. 2 and 3 are cross-sectional diagrams of utilizing
dual-layer photoresist to form black matrixes and spacers on a
control circuit substrate in FIG. 1 according to a preferred
embodiment of this invention. The labels A and B in FIGS. 2 and 3
indicate the cross-sectional views of the cross-sectional lines M'
and BB', respectively. The TFT structures are not drawn in the
Parts A in FIGS. 2 and 3 to simplify the pictures.
[0032] In FIG. 2, a passivation layer 150 such as a silicon nitride
layer is formed by, for example, chemical vapor deposition (CVD) on
the control circuit substrate 105 (i.e. the transparent substrate
100 having the control circuit thereon as shown in FIG. 1). The
control circuit substrate 105 comprises, for example, a TFT array
substrate. Next, the passivation layer 180 is patterned by, for
example, photolithography and etching to form contact windows 152
therein to expose drains 130 (not shown in FIG. 2) of the TFT,
respectively.
[0033] A color filter layer 155 is formed on the control circuit
substrate 105. The color filter is made of red, green and blue
colors color filters respectively on pixels 135 (as shown in FIG.
1). In general, the red, green and blue photoresist are
respectively patterned by three photolithography steps to form the
red, green and blue colors color filters and thus the color filter
layer 155.
[0034] A transparent conductive layer is formed and then is
patterned to form pixel electrodes 160 by, for example,
photolithography and etching. The pixel electrodes 160 electrically
connect to the drains 130 (not shown in FIG. 2) of the control
devices through the contact windows 152, respectively. A material
of the pixel electrodes 160 includes indium tin oxide or indium
zinc oxide.
[0035] In FIG. 3, a black resin is formed on the control circuit
105 having the color filter layer 155 and the pixel electrodes 160
located thereon. Then, the black resin is soft-baked. A transparent
photoresist is formed on the black resin and then is soft-baked.
Next, the transparent photoresist and the black resin are patterned
and hard-baked to form black resin layers 165 and transparent
photoresist layers 170. Consequently, black matrixes is formed by
stacking the black resin layers 165 and the transparent photoresist
layers 170 on Part A, and spacers are formed by stacking the black
resin layers 165 and the transparent photoresist layers 170 on Part
B.
[0036] According to a preferred embodiment of this invention, when
a material of the black resin layers 165 is non-photosensitive
black resin, the material of the transparent photoresist layers 170
is positive or negative photosensitive transparent photoresist. The
thickness of the non-photosensitive black resin is about 0.2-1.5
.mu.m so that the optical density of the black resin is greater
than 3 to shield the control devices from external light. Moreover,
the total thickness of the black resin layers 165 and the
transparent photoresist layers 170 is equal to the required spacing
between the two transparent substrates of a liquid crystal
display.
[0037] The method of patterning the black resin and the transparent
photoresist comprises the following steps. The transparent
photoresist is exposed and then is developed by a developer
solution. The developer solution is also used to remove the black
resin uncovered by the transparent photoresist during developing
the transparent photoresist. Since the needed exposure dose for
exposing the transparent photoresist is less than that for exposing
the black resin, the exposure dose required for the transparent
photoresist is much less than that for the black resin alone in the
exposure step. In the subsequent developing step, the insoluble
transparent photoresist 170 can protect the black resin 165 lying
below by being insoluble in the developer solution. Therefore, only
one photo mask, i.e. one photolithography process, is needed to
form the black matrixes and the spacers simultaneously.
[0038] According to another preferred embodiment, when a material
of the black resin layers 165 is a negative photosensitive black
resin, the material of the transparent photoresist layers 170 is
also a negative photosensitive transparent photoresist. Therefore,
the black resin and the transparent photoresist can be
simultaneously patterned by conventional photolithography.
[0039] The thickness of the non-photosensitive black resin is about
1-2 .mu.m so that the optical density of the black resin is greater
than 3 to shield the control devices from external light. Moreover,
the total thickness of the black resin layers 165 and the
transparent photoresist layers 170 is equal to the required spacing
between the two transparent substrates of a liquid crystal display.
Similarly, since the exposure dose required for exposing the
transparent photoresist is less than that for the black resin, the
exposure dose required for the transparent photoresist and the
black resin is much less than that for the black resin alone in the
exposure step. In the subsequent developing step, the unexposed
black resin and the transparent photoresist can be simultaneously
dissolved in the developer solution. Therefore, only one photo
mask, i.e. one photolithography process, is needed to form the
black matrixes and the spacers simultaneously.
[0040] The subsequent fabrication processes are well known by
persons skilled in the art. Hence, the cross-sectional diagrams of
the fabrication processes are omitted here, and subsequent
fabrication processes are described verbally, only.
[0041] Next, another transparent conductive layer is formed on
another transparent substrate as a common electrode. These two
transparent substrates are parallel assembled, and the pixel
electrodes 160 and the common electrode face each other. The
periphery of the two transparent substrates is sealed, and only one
opening is left for pouring liquid crystal into the space between
the two transparent substrates. After pouring in the liquid crystal
to fill the space between the two transparent substrates, the
opening is sealed to accomplish the fabrication process of a TFT
LCD.
EMBODIMENT 2
[0042] FIGS. 2 and 4 are cross-sectional diagrams of utilizing
dual-layer photoresist to form black matrixes and spacers on a
control circuit substrate in FIG. 1 according to another preferred
embodiment of this invention. The labels A and B in FIGS. 2 and 4
indicate the cross-sectional views of the cross-sectional lines AA'
and BB', respectively. The TFT structures are not drawn on the
Parts A in FIGS. 2 and 4 to simplify the pictures. Besides, a
detailed description of FIG. 2 has been given above, and hence is
omitted here.
[0043] In FIG. 4, a transparent photoresist is formed on the
control circuit 105 having the color filter layer 155 and the pixel
electrodes 160 located thereon. Then, the transparent photoresist
is soft-baked. A black resin is formed on the black resin and then
is soft-baked. Next, the black resin and the transparent
photoresist are patterned and hard-baked to form transparent
photoresist layers 175 and black resin layers 180. Consequently,
black matrixes is formed by stacking the transparent photoresist
layers 175 and the black resin layers 180 on Part A, and spacers
are formed by stacking the transparent photoresist layers 175 and
the black resin layers 180 on Part B.
[0044] According to another preferred embodiment, when a material
of the black resin layers 180 is a negative photosensitive black
resin, the material of the transparent photoresist layers 175 is
also a negative photosensitive transparent photoresist. Therefore,
the black resin and the transparent photoresist can be pattered by
conventional photolithography simultaneously.
[0045] The thickness of the non-photosensitive black resin is about
1-2 .mu.m so that the optical density of the black resin is greater
than 3 to shield the control devices from external light. Moreover,
the total thickness of the black resin layers 165 and the
transparent photoresist layers 170 is equal to the required spacing
between the two transparent substrates of a liquid crystal display.
Similarly, since the exposure dose required for the transparent
photoresist is less than that for the black resin, the exposure
dose required for the transparent photoresist and the black resin
is much less than that for the black resin alone in the exposure
step. In the subsequent developing step, the unexposed black resin
and the transparent photoresist can be simultaneously dissolved in
the developer solution. Therefore, only one photo mask, i.e. one
photolithography process, is needed to form the black matrixes and
the spacers simultaneously.
[0046] The subsequent fabrication processes are well known by
persons skilled in the art. Hence, the cross-sectional diagrams of
the fabrication processes are omitted here, and subsequent
fabrication processes are described verbally, only.
[0047] Next, another transparent conductive layer is formed on
another transparent substrate as a common electrode. These two
transparent substrates are parallel assembled, and the pixel
electrodes 160 and the common electrode face each other. The
periphery of the two transparent substrates is sealed, and only one
opening is left for pouring liquid crystal into the space between
the two transparent substrates. After pouring in the liquid crystal
to fill the space between the two transparent substrates, the
opening is sealed to accomplish the fabrication process of a TFT
LCD.
[0048] In light of foregoing, the function of the black matrixes is
achieved by black resin having a thickness that makes the optical
density of the black resin greater than 3. The function of the
spacers is achieved by the transparent photoresist to maintain the
required spacing between the two transparent substrates of a LCD.
Therefore, the transparent photoresist having much improved
properties of light transmittance and photosensitivity can be used
to replace most of the black resin to greatly reduce the required
thickness of a single black resin layer. Therefore, utilizing this
invention can not only decrease the required exposure time but also
increase the process margin, and thus the product throughput is
greatly increased.
[0049] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *