U.S. patent application number 12/274609 was filed with the patent office on 2009-03-19 for methods for fabricating transflective liquid crystal displays.
This patent application is currently assigned to AU OPTRONICS CORP.. Invention is credited to Chih-Ming Chang, Chih-Jen Hu, Kuo-Yung Hung, Chih-Chun Pei.
Application Number | 20090075189 12/274609 |
Document ID | / |
Family ID | 38619124 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090075189 |
Kind Code |
A1 |
Hung; Kuo-Yung ; et
al. |
March 19, 2009 |
METHODS FOR FABRICATING TRANSFLECTIVE LIQUID CRYSTAL DISPLAYS
Abstract
A method for fabricating a display is disclosed. A first
substrate comprising a plurality of pixels is provided, each pixel
comprises a plurality of sub pixels. A second substrate
substantially opposite to the first substrate is provided, wherein
the second substrate is divided into a plurality of regions
corresponding to the sub-pixels, and at least three of the regions
are color regions and at least one of the regions is a fourth
region. A photoresist pattern layer is formed on the second
substrate, such that the photoresist pattern layer corresponding to
the at least three color regions are color photoresist pattern
layers and the photoresist pattern layer corresponding to the at
least one fourth region is a fourth photoresist pattern layer. A
first covering layer is formed on the photoresist layer. A liquid
crystal layer is interposed between the first substrate and the
second substrate.
Inventors: |
Hung; Kuo-Yung; (Miaoli
County, TW) ; Chang; Chih-Ming; (Taoyuan County,
TW) ; Hu; Chih-Jen; (Hsinchu City, TW) ; Pei;
Chih-Chun; (Taoyuan County, TW) |
Correspondence
Address: |
THOMAS, KAYDEN, HORSTEMEYER & RISLEY, LLP
600 GALLERIA PARKWAY, S.E., STE 1500
ATLANTA
GA
30339-5994
US
|
Assignee: |
AU OPTRONICS CORP.
Hsinchu
TW
|
Family ID: |
38619124 |
Appl. No.: |
12/274609 |
Filed: |
November 20, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11554657 |
Oct 31, 2006 |
|
|
|
12274609 |
|
|
|
|
Current U.S.
Class: |
430/20 |
Current CPC
Class: |
G02F 1/133516 20130101;
G02F 2202/023 20130101; G02F 1/133555 20130101; G02F 1/133519
20210101 |
Class at
Publication: |
430/20 |
International
Class: |
G02F 1/13 20060101
G02F001/13 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2006 |
TW |
95114273 |
Claims
1. A method for fabricating a display comprising: providing a first
substrate comprising a plurality of pixels, each pixel comprises a
plurality of sub pixels; providing a second substrate substantially
opposite to the first substrate, wherein the second substrate is
divided into a plurality of regions corresponding to the
sub-pixels, and at least three of the regions are color regions and
at least one of the regions is a fourth region; forming a
photoresist pattern layer on the second substrate, such that the
photoresist pattern layer corresponding to the at least three color
regions are color photoresist pattern layers and the photoresist
pattern layer corresponding to the at least one fourth region is a
fourth photoresist pattern layer; forming a first covering layer on
the photoresist layer; and interposing a liquid crystal layer
between the first substrate and the second substrate.
2. The method of claim 1, wherein the first covering layer has a
substantially uniform thickness.
3. The method of claim 1, further comprising: forming a second
covering layer on the first substrate.
4. The method of claim 3, wherein the second covering layer has a
substantially uniform thickness.
5. The method of claim 3, wherein the first covering layer and the
second covering layer both have substantially uniform
thicknesses.
6. The method of claim 3, wherein formation the photoresist pattern
layer comprises: coating the photoresist layer on the second
substrate; and patterning the photoresist layer to define the
photoresist layer corresponding to the at least three color regions
as the color resist pattern layers and to define the photoresist
layer corresponding to the at least one fourth region as the fourth
resist pattern layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of pending U.S. patent
application Ser. No. 11/554,657, filed Oct. 31, 2006 and entitled
"TRANSFLECTIVE LIQUID CRYSTAL DISPLAYS AND METHODS FOR FABRICATING
THE SAME", which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a display and methods for
fabricating the same, and more particularly, to a liquid crystal
display and methods for fabricating the same.
[0004] 2. Description of the Related Art
[0005] Liquid crystal displays (LCD) are commonly used for flat
panel displays. Owing to dielectric anisotropy and conductive
anisotropy of liquid crystal molecules, molecular orientation of
liquid crystals can be shifted under an external electronic field,
such that various optical effects are produced. The panel structure
of an LCD typically comprises two laminated substrates separated by
a gap and liquid crystal injected therebetween. Corresponding
electrodes on each substrate control the direction and arrangement
of liquid crystal molecules.
[0006] Referring to FIG. 1A, in addition to the three primary
colors pixels, which are red, green, and blue pixels, a white pixel
is also provided to increase transmissive or reflective brightness
and thus reduce power consumption. Mixed RGBW LCDs, however, suffer
from many drawbacks.
[0007] Referring to FIG. 1B, a first substrate 100 such as an array
substrate is provided. The first substrate 100 comprises a
plurality of pixels, each comprising a plurality of sub-pixels.
[0008] A plurality of thin film transistors (TFTs) 108 is then
formed on the first substrate 100, and each sub-pixel corresponds
to a TFT 108. The TFT 108 comprises a gate 102, source 104, and
drain 106.
[0009] A second substrate 110 opposite to the first substrate 100
is provided. The second substrate 210, preferably is a color filter
substrate, comprises a red region provided with a red resist layer
R thereon, a blue region provided with a blue resist layer B
thereon, a green region provided with a green resist layer G
thereon and a white region provided with a transparent resist layer
W thereon, wherein each region corresponds to a sub-pixel. Thus, a
color filter layer with the mixed RGBW is obtained.
[0010] After forming the RGB resist layers, a planarized covering
layer 112 is blanketly coated on the second substrate 110 and the
gaps between RGB resist layers is thus filled with the covering
layer 212, thereby forming the transparent resist layer W. The
planarized covering layer 112 is beneficial for subsequent
fabrication processes due to its planar surface. Because the RGB
resist layers affect surface tension and mechanical action of the
covering layer 112, a gap "d" exists in portions of the covering
layer 112 corresponding to the white region. Accordingly, a color
shift phenomenon such as a yellow shift arises in LCDs.
BRIEF SUMMARY OF THE INVENTION
[0011] In accordance with one embodiment of the present invention,
a transflective liquid crystal display comprises a first substrate
comprising a plurality of pixels, wherein each pixel comprises a
plurality of sub-pixels and each sub-pixel comprises at least one
transmissive region and at least one reflective region. A second
substrate is substantially opposite to the first substrate, wherein
the second substrate is defined into a plurality of regions
corresponding to the sub-pixels, and at least three of the regions
are color regions and at least one of the regions is a fourth
region. A first covering layer covers the first substrate, wherein
a portion of the first covering layer in the transmissive region of
each sub-pixels corresponding to the at least one fourth region is
substantially thicker than other portions of the first covering
layer in the transmissive region of each sub-pixels corresponding
to the at least three of the regions, and the thickness of the
first covering layer in the reflective region of each sub-pixels
corresponding to the at least one fourth region is substantially
equal to the thickness of other portions of the first covering
layer in the reflective region of each sub-pixels corresponding to
the at least three of the regions. And a liquid crystal layer is
disposed between the first substrate and the second substrate.
[0012] In accordance with another embodiment of the present
invention, a method for forming a transflective liquid crystal
display comprises providing a first substrate comprising a
plurality of pixels, each pixel comprises a plurality of
sub-pixels, and each sub-pixel comprises at least one transmissive
region and at least one reflective region. A second substrate
substantially opposite to the first substrate is provided, wherein
the second substrate are defined into a plurality of regions
corresponding to the sub-pixels, and at least three of the regions
are color regions and at least one of the regions is a fourth
region. A first covering layer is formed on the first substrate. A
plurality of lithography processes are performed on the first
covering layer, wherein number of exposures of the first covering
layer in the transmissive region of each sub-pixels corresponding
to the at least one fourth region are less substantially than that
of the first covering layer in the transmissive region of each
sub-pixels corresponding to the at least three of the regions, and
a liquid crystal layer is interposed between the first substrate
and the second substrate.
[0013] In accordance with yet another embodiment of the present
invention, a method for fabricating a display comprises providing a
first substrate comprising a plurality of pixels, each pixel
comprises a plurality of sub pixels. A second substrate
substantially opposite to the first substrate is provided, wherein
the second substrate is defined into a plurality of regions
corresponding to the sub-pixels, and at least three of the regions
are color regions and at least one of the regions is a fourth
region. A photoresist pattern layer is formed on the second
substrate, wherein the photoresist pattern layer corresponding to
the at least three color regions are color resist layers and the
photoresist pattern layer corresponding to the at least one fourth
region is a fourth resist layer. A first covering layer is formed
on the photoresist pattern layer. And a liquid crystal layer is
interposed between the first substrate and the second
substrate.
[0014] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention can be more fully understood by
reading the subsequent detailed description and examples with
references made to the accompanying drawings, wherein:
[0016] FIG. 1A is schematic view of pixel arrangement of a mixed
RGBW LCD.
[0017] FIG. 1B is cross section of a conventional transflective
liquid crystal display.
[0018] FIG. 2 is a cross section of an embodiment of a single gap
transflective liquid crystal display of the present invention.
[0019] FIG. 3 is a cross section of an embodiment of a dual gap
transflective liquid crystal display of the present invention.
[0020] FIG. 4A-4C are schematic views showing formation of the
second covering layer of the single gap transflective liquid
crystal display according with a preferred embodiment of the
present invention.
[0021] FIGS. 5A-5C are schematic views showing formation of the
second covering layer of the single gap transflective liquid
crystal display according with another embodiment of the present
invention.
[0022] FIGS. 6A-6C are schematic views showing formation of the
covering layer of the dual gap transflective liquid crystal display
according with a preferred embodiment of the present invention.
[0023] FIGS. 7A-7C are schematic views showing formation of the
covering layer of the dual gap transflective liquid crystal display
according with another embodiment of the present invention.
[0024] FIG. 8 is a cross section of a transflective liquid crystal
display according with another embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The following description is of the best-contemplated mode
of carrying out the invention. This description is made for the
purpose of illustrating the general principles of the present
invention and should not be taken in a limiting sense. The scope of
the present invention is best determined by reference to the
appended claims.
[0026] In this specification, expressions such as "overlying the
substrate", "above the layer", or "on the film" simply denote a
relative positional relationship with respect to the surface of the
base layer, regardless of the existence of intermediate layers.
Accordingly, these expressions may indicate not only the direct
contact of layers, but also, a non-contact state of one or more
laminated layers.
[0027] FIG. 2 shows a cross section of a single gap transflective
liquid crystal display according with a preferred embodiment of the
present invention. Referring to FIG. 2, a first substrate 200,
which the materials may comprise transparent material such as
glass, low alkali glass, non-alkali glass, or likes, flexible
material such as plastics, poly carbonate (PC), polymethyl
methacrylate (PMMA), or likes, opaque material such as ceramics,
wafer, or likes, is provided. The first substrate 200 comprises a
plurality of pixels for displaying image, each comprising a
plurality of sub-pixels. Each sub-pixel comprises at least a
reflective region R and at least a transmissive region T. In the
reflective region R, a light source for the liquid crystal display
is provided by reflected exterior light, while in the transmissive
region T, a back light source is used as a light source for the
liquid crystal display. The transflective liquid crystal display
thus reduces power consumption and achieves better efficiency.
[0028] A plurality of thin film transistors (TFTs) 208 are formed
on the first substrate 200 which may be an array substrate. In a
preferred embodiment, each sub-pixel corresponds to a TFT 208, and
each TFT 208 comprises a gate 202, a channel (not shown), an ohmic
contact layer (not shown), source 204, and drain 206. Preferably,
the TFT 208 may be a bottom-gate type TFT, but not-limited it's. Of
course, other types of TFTs such as a top-gate type TFT, an etching
stop type TFT, or likes may be can to use. Constructing of the
material of the TFT 208 may comprise polysilicon, amorphous
silicon, single crystal silicon, microcrystalline silicon, or
combinations thereof. In other words, the material of the channel
(not shown) and the ohmic contact layer (not shown) may comprise
polysilicon, amorphous silicon, single crystal silicon,
microcrystalline silicon, or combinations thereof. The ohmic
contact layer (not shown) may be doped with N type ions such as P,
As, or the like. Alternatively, the ohmic contact layer (not shown)
may be doped with P type ions such as B or the like.
[0029] A second substrate 210 substantially opposite to the first
substrate 200 is provided. The second substrate 210, preferably a
color filter substrate, may comprise at least three color regions
and at least one fourth region corresponding to the sub-pixels.
These three color regions may comprise a red region provided with a
red resist layer R thereon, a blue region provided with a blue
resist layer B thereon and a green region provided with a green
resist layer G thereon. The fourth region may comprise a white
region, also referred to as an achromatic region, provided with a
transparent resist layer W thereon. A color filter layer with the
mixed RGBW is thus obtained.
[0030] The embodiments of the present invention described
hereinafter are based on the three primary colors RGB as shown in
FIG. 2. The present invention is, however, not limited to the
disclosed RGB regions. In other words, various colors of resist
layers in the color regions, for example, yellow, brown, purple, or
other colors can be used without departing from the spirit or scope
of the present inventive concept. Additionally, the embodiments of
the present invention are based on a rectangular shape of the color
regions and the fourth region. The present invention is, however,
not limited to the rectangular color regions or the fourth region
disclosed. Various shapes of the color regions and the fourth
region can be used, for example, circle, polygon, triangle,
hexagon, or ellipse without departing from the spirit or scope of
the present inventive concept. Furthermore, the present invention
is not limited to the white region in the fourth region. Other
colors of the resist layer or the colors of the resist layer can be
used in the fourth region for improving color saturation and color
contrast of an LCD.
[0031] In the above-mentioned LCD structure, a flatness of a
covering layer 212 is blanketly coated on the second substrate 210
after forming the RGB resist layers, and the gaps between RGB
resist layers is thus filled with the covering layer 212, thereby
forming the transparent resist layer W. The covering layer 212 is
beneficial to subsequent fabrication processes due to its planar
surface. Because the RGB resist layers affect surface tension and
mechanical action of the covering layer 212, a gap "d" exists in
portions of the covering layer 212 corresponding to the fourth
region.
[0032] In a preferred embodiment, a covering layer 214 is formed on
the first substrate 200 to cover the first substrate 200 and the
TFTs 208. In the transmissive region T, a portion of the covering
layer 214 corresponding to the fourth region (white region) is
substantially thicker than other portions of the covering layer 214
corresponding to the color regions. In the reflective region R, a
portion of the covering layer 214 corresponding to the fourth
region (white region) and the color regions has substantially
uniform thickness. In other words, the covering layer 214
corresponding to the transmissive region T of the fourth region has
a protruding portion 216. The protruding portion 216 of the
covering layer 214 compensates for the gap "d" in the covering
layer 212 corresponding to the white region, and optical efficiency
of a display is thus improved.
[0033] Detailed description of forming the aforementioned structure
of the covering layer 214 is provided in the following. The
covering layer 214, preferably comprising photo-sensitive material,
is formed on the first substrate 200. The covering layer 214 is
exposed for a plurality of times, wherein the number of exposures
of the covering layer 214 corresponding to the white region in the
transmissive region T is less than that of the covering layer 214
corresponding to the red, blue, and green regions in the
transmissive region T. The covering layer 214 is then
developed.
[0034] FIG. 4A-4B are schematic views showing formation of the
covering layer 214 of the single gap transflective liquid crystal
display according with a preferred embodiment of the present
invention. Referring to FIG. 4A, the covering layer 214, which may
comprise photo-sensitive material such as photoresist, is blanketly
coated on the first substrate (not shown) to cover the thin film
transistors (not shown) and the first substrate. In a preferred
embodiment, the photoresist layer acting as the covering layer is a
positive photoresist layer. The covering layer 214 corresponding to
the reflective region T is exposed, while the covering layer 214
corresponding to the transmissive region T is shaded by a mask such
as a photomask. The exposed portion of the covering layer 214 is
marked by oblique lines.
[0035] Referring to FIG. 4B, the covering layer 214 corresponding
to the transmissive region T of the fourth region (white region) is
shaded by, for example, a photomask, while the covering layer 214
corresponding to the transmissive region T of the RGB regions and
the covering layer 214 corresponding to the reflective region R are
exposed. Referring to 4C, the covering layer 214 besides openings
402 in the transmissive region T is shaded by, for example, a
photomask, while the covering layer 214 corresponding to the
opening segments in the transmissive region T is exposed. In the
light of the previously described method for performing lithography
processes on the covering layer 214, the number of exposures of the
covering layer 214 in the transmissive region of each sub-pixels
corresponding to the at least one fourth region is less than that
of the first covering layer in the transmissive region of each
sub-pixels corresponding to the at least three of the regions for
once. Accordingly, the covering layer 214 corresponding to the
transmissive region of the fourth region is substantially thicker
than the covering layer 214 corresponding to the transmissive
region T of the RGB regions.
[0036] In a preferred embodiment, the covering layer 214 may have a
thickness of about 2.0 .mu.m. Exposure doses may expose the
covering layer 214, made of positive photoresist, to a depth of
about 0.6 .mu.m to about 0.8 .mu.m. The covering layer 214
corresponding to the transmissive region T of the white region may
have a thickness of about 1.8 .mu.m to about 2.2 .mu.m. The
covering layer 214 corresponding to other portions besides the
transmissive region T of the white region may have a thickness of
about 1 .mu.m to about 1.6 .mu.m, preferably, 1.2 .mu.m to about
1.6 .mu.m. The protruding portion 216 may has a thickness of about
0.1 .mu.m to about 0.3 .mu.m, that is, the portion of the covering
layer 214 in the transmissive region of each sub-pixels
corresponding to the at least one fourth region is thicker than the
other portions of the covering layer 214 in the transmissive region
of each sub-pixels corresponding to the at least three of the
regions about 0.1 .mu.m to about 0.3 .mu.m.
[0037] FIGS. 5A-5C are schematic views showing formation of the
covering layer 214 of the single gap transflective liquid crystal
display according with another embodiment of the present invention.
Referring to FIG. 5A, the covering layer 214, which may comprise
photo-sensitive material such as photoresist, is blanketly coated
on the first substrate (not shown) to cover the thin film
transistors (not shown) and the first substrate. In a preferred
embodiment, the photoresist layer acting as the covering layer 214
is a positive photoresist layer. The covering layer 214
corresponding to the transmissive region T of the fourth region is
shaded by, for example, a photomask, while the covering layer 214
corresponding to the transmissive region T of the RGB regions and
the covering layer 214 corresponding to the reflective region R are
exposed.
[0038] Referring to FIG. 5B, the covering layer 214 corresponding
to the transmissive region T is shaded by, for example, a
photomask, while the covering layer 214 corresponding to the
reflective region R is exposed. Referring to FIG. 5C, the covering
layer 214 besides openings 502 in the transmissive region T is
shaded by, for example, a photomask, while the covering layer 214
corresponding to the openings 502 in the transmissive region T is
exposed. In the light of the previously described method for
performing lithography process on the covering layer 214, the
number of exposures of the covering layer 214 in the transmissive
region of each sub-pixels corresponding to the at least one fourth
region is less than that of the covering layer 214 in the
transmissive region of each sub-pixels corresponding to the at
least three of the regions for once. Accordingly, the covering
layer 214 corresponding to the transmissive region of the fourth
region is substantially thicker than the covering layer 214
corresponding to the transmissive region T of the RGB regions.
[0039] FIG. 3 shows a cross section of a dual gap transflective
liquid crystal display according with a preferred embodiment of the
invention. The structure and fabrication process of FIG. 3 is
similar to FIG. 2. Therefore, detailed description thereof is
omitted. FIG. 3 differs from FIG. 2 in that a thickness Tr of a
liquid crystal layer 302 in a reflective region R is substantially
less than a thickness Tt of the liquid crystal layer 302 in a
transmissive region T. Accordingly, the covering layer 304
corresponding to the reflective region R is substantially thicker
than the covering layer 304 corresponding to the transmissive
region T. To reduce the color shift phenomenon, the covering layer
304 corresponding to the fourth region (white region) in the
transmissive region T is substantially thicker than the covering
layer 304 corresponding to the RGB regions in the transmissive
region T. In the reflective region R, a portion of the covering
layer 304 corresponding to the fourth region (white region) and the
color regions (RGB) has substantially uniform thickness. In a word,
the covering layer corresponding to the white region in the
transmissive region T has a protruding portion 306.
[0040] Detailed description of forming the aforementioned structure
of the covering layer 214 is provided in the following. The
covering layer 304, preferably comprising photo-sensitive material,
is formed on the first substrate. The covering layer 304 is then
exposed for a plurality of times, wherein the number of exposures
of the covering layer 304 in the transmissive region T is more than
that of the covering layer 304 in the reflective region R, and the
number of exposures of the covering layer 304 corresponding to the
white region in the transmissive region T is less than that of the
covering layer 304 corresponding to the RGB regions in the
transmissive region T. The covering layer 304 is next
developed.
[0041] FIGS. 6A-6C are schematic views showing formation of the
covering layer 304 of the dual gap transflective liquid crystal
display according with a preferred embodiment of the invention.
Referring to FIG. 6A, the covering layer 304, which may comprise
photo-sensitive material such as photoresist, is blanketly coated
on the first substrate (not shown) to cover the thin film
transistors (not shown) and the first substrate. In a preferred
embodiment, the photoresist layer acting as the covering layer 304
is a positive photoresist layer. The entire covering layer 304 is
exposed. The exposed portion of the covering layer 304 is marked by
oblique lines.
[0042] Referring to FIG. 6B, the entire covering layer 304 is then
exposed again. Referring to 6C, the covering layer 304
corresponding to the RGB regions in the transmissive region T and
the covering layer 304 corresponding to an opening 602 of the white
region in the transmissive region T are exposed, while the covering
layer 304 except for the opening 602 in the transmissive region T
and the covering layer 304 corresponding to the RGB regions and
white region in the reflective region R are shaded by, for example,
a photomask. In the light of the previously described method for
performing lithography processes on the covering layer 304, the
number of exposures of the covering layer 304 in the transmissive
region of each sub-pixels corresponding to the at least one fourth
region (white region) is less than that of the first covering layer
in the transmissive region of each sub-pixels corresponding to the
at least three of the regions (RGB regions) for once. Accordingly,
the covering layer 304 corresponding to the transmissive region of
the white region is substantially thicker than the covering layer
304 corresponding to the transmissive region T of the RGB
regions.
[0043] FIGS. 7A-7C are schematic views showing formation of the
covering layer 304 of the dual gap transflective liquid crystal
display according with another embodiment of the invention.
Referring to FIG. 6A, the covering layer 304, which may comprise
photo-sensitive material such as photoresist, is blanketly coated
on the first substrate (not shown) to cover the thin film
transistors (not shown) and the first substrate. In a preferred
embodiment, the photoresist layer acting as the covering layer 304
is a positive photoresist layer. The covering layer 304 in the
reflective region R is exposed, while the covering layer 304 in the
transmissive region T is shaded by, for example, a photomask.
[0044] Referring FIG. 7B, the entire covering layer 304 is exposed.
Referring to 7C, the covering layer 304 corresponding to the RGB
regions in the transmissive region T and the covering layer 304
corresponding to a opening 702 of the white region in the
transmissive region T are exposed, while the covering layer 304
except for the opening 702 in the transmissive region T and the
covering layer 304 corresponding to the RGB regions and white
region in the reflective region R are shaded by, for example, a
photomask. In the light of the previously described method for
performing lithography process on the covering layer 304, the
number of exposures of the covering layer 304 in the transmissive
region of each sub-pixels corresponding to the at least one fourth
region (white region) is less than that of the first covering layer
in the transmissive region of each sub-pixels corresponding to the
at least three of the regions (RGB regions) for once. Accordingly,
the covering layer 304 corresponding to the transmissive region of
the white region is substantially thicker than the covering layer
304 corresponding to the transmissive region T of the RGB
regions.
[0045] FIG. 8 is a cross section of a transflective liquid crystal
display according with another embodiment of the invention.
Referring to FIG. 8, a first substrate 800, which may comprise
transparent material such as glass, low alkali glass, non-alkali
glass, or likes, flexible material such as plastics, poly carbonate
(PC), polymethyl methacrylate (PMMA), or likes, opaque material
such as ceramic, wafer, or likes, is provided. The first substrate
800 comprises a plurality of pixels.
[0046] A plurality of thin film transistors (TFTs) 808 are formed
on the first substrate 800 which may be an array substrate. In a
preferred embodiment, each sub-pixel corresponds to a TFT 808, and
each TFT 808 comprises a gate 802, a channel (not shown), an ohmic
contact layer (not shown), source 804 and drain 806. Preferably,
the TFT 808 may be a bottom-gate type TFT. Alternatively, other
types of TFTs such as a top-gate type TFT, an etching stop type
TFT, or likes may be used. The TFT 808 may be made of polysilicon,
amorphous silicon, single crystal silicon, microcrystalline
silicon, or combinations thereof. The channel (not shown) and the
ohmic contact layer (not shown) may comprise polysilicon, amorphous
silicon, single crystal silicon, microcrystalline silicon, or
combinations thereof. The ohmic contact layer (not shown) may be
doped with N type ions such as P, As, or likes. Alternatively, the
ohmic contact layer (not shown) may be doped with P type ions such
as B or likes. A first covering layer 807 is then formed on the
first substrate 800 and TFTs 808.
[0047] A second substrate 810 opposite to the first substrate 800
is provided. The second substrate 810, preferably a color filter
substrate, may comprise at least three color regions and one fourth
region corresponding to the sub-pixels. These three color regions
may comprise a red region, a blue region, and a green region, and
the fourth region may comprise a white region. Photoresist pattern
layers are then formed on the second substrate 810. The photoresist
pattern layers comprises a red resist layer R in the red region, a
blue resist pattern layer B in the blue region, a green resist
pattern layer G in the green and a transparent resist pattern layer
W in the white region. In a preferred embodiment, the red resist
pattern layer R is formed in the red region in the second substrate
810 by a lithography process. The blue resist pattern layer B is
formed in the blue region in the second substrate 810 by a
lithography process. The green resist pattern layer G is formed in
the green region in the second substrate 810 by using a lithography
process. The transparent resist pattern layer W is formed in the
white region in the second substrate 810 by using a lithography
process.
[0048] Note that the transparent resist pattern layer W is filled
into the fourth region in the second substrate 810, and the
transparent W in the color regions such as RGB regions is removed
by a lithography process. Because the transparent resist pattern
layer W only exists in the white region, a gap "d.degree." in
portions of the covering layer on the second substrate 810
corresponding to the white region due to the surface tension and
the mechanical action of the RGB region thus disappears.
[0049] A covering layer 803 is then formed in the RGB regions and
white region on the second substrate 810. Surface of the covering
layer 803 is flat, and there is no gap "d" in the covering layer
803. Lastly, a liquid crystal layer 830 is interposed between the
first substrate 800 and the second substrate 810 to complete the
fabrication of an LCD.
[0050] According to the disclosed embodiments above, in a single
gap transflective liquid crystal display or a dual gap
transflective liquid crystal display, the covering layer
corresponding to the white region is substantially thicker than the
covering layer corresponding to the color regions by adjusting the
number of exposures of the covering layer in the transmissive
region. While, the covering layer corresponding to the reflective
region substantially has a uniform thickness. In the reflective
region, a circuit controller such as a Look-Up-Table may be used to
reduce the color shift phenomenon, for example yellow shift.
[0051] Accordingly, embodiments of the present invention provide
methods for fabricating a liquid crystal display, which improve
optical efficiency of an LCD by eliminating the gap causing the
color shift phenomenon in the white region.
[0052] While the present invention has been described by way of
example and in terms of the preferred embodiments, it is to be
understood that the present invention is not limited to the
disclosed embodiments. To the contrary, it is intended to cover
various modifications and similar arrangements (as would be
apparent to those skilled in the art). Therefore, the scope of the
appended claims should be accorded the broadest interpretation so
as to encompass all such modifications and similar
arrangements.
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