U.S. patent application number 11/783373 was filed with the patent office on 2007-08-09 for liquid crystal display device and method for manufacturing the same.
This patent application is currently assigned to Citizen Watch Co., Ltd. Invention is credited to Seigo Togashi.
Application Number | 20070182889 11/783373 |
Document ID | / |
Family ID | 33156564 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070182889 |
Kind Code |
A1 |
Togashi; Seigo |
August 9, 2007 |
Liquid crystal display device and method for manufacturing the
same
Abstract
A liquid crystal display device comprises: first and second
transparent substrates; a liquid crystal that is enclosed between
the first and second transparent substrates; a first color filter
that is formed on either the first or second transparent substrate;
a light reflective layer that has a plurality of openings and that
is formed on the second transparent substrate toward the liquid
crystal; and a second color filter that is formed on the second
transparent substrate on the side opposite to the liquid crystal.
The second color filter is fabricated by forming a layer of a color
photosensitive material such as a photosensitive emulsion and
illuminating and coloring this layer by light transmitting through
the first color filter using the reflective layer as an exposure
mask. As a result, a second color filter, that has a color dot
pattern the same as that of the first color filter, is formed by
one exposure and developing process.
Inventors: |
Togashi; Seigo; (Sakado-shi,
JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Citizen Watch Co., Ltd
|
Family ID: |
33156564 |
Appl. No.: |
11/783373 |
Filed: |
April 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10740864 |
Dec 22, 2003 |
7221417 |
|
|
11783373 |
Apr 9, 2007 |
|
|
|
Current U.S.
Class: |
349/106 |
Current CPC
Class: |
G02F 1/133516 20130101;
G02F 1/133555 20130101; G02F 1/136222 20210101; G02F 1/133514
20130101 |
Class at
Publication: |
349/106 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2002 |
JP |
2002-377005 |
Claims
1. A liquid crystal display device, comprising: first and second
transparent substrates; a liquid crystal that is enclosed between
said first and second transparent substrates; a first color filter
that is formed on either said first or second transparent
substrate; a light reflective layer that has a plurality of
openings and that is formed on said second transparent substrate
toward the liquid crystal; and a second color filter that is formed
on said second transparent substrate on the side opposite to said
liquid crystal, wherein said first color filter is formed on said
light reflective laver of said second substrate.
2. A liquid crystal display device according to claim 1, wherein
said second color filter is made of a color photosensitive
material.
3-4. (canceled)
5. A liquid crystal display device according to claim 1, wherein
said first color filter is formed of a plurality of dots comprised
of colors of red, green and blue and the center of each dot of said
first color filter agrees with the center of said openings of said
light reflective layer.
6. A liquid crystal display device according to claim 2, wherein
said color photosensitive material comprises a photosensitive
emulsion.
7. A liquid crystal display device according to claim 1, wherein a
backlight device is disposed below a surface of said second
transparent substrate and on the side opposite to said liquid
crystal.
8-16. (canceled)
17. A liquid crystal display device, comprising: first and second
transparent substrates; a liquid crystal that is enclosed between
said first and second transparent substrates; a first color filter
that is formed on either said first or second transparent
substrate; a light reflective layer that has a plurality of
openings and that is formed on said second transparent substrate
toward the liquid crystal; and a second color filter that is formed
on said second transparent substrate on the side opposite to said
liquid crystal, wherein said first and second color filters have
substantially equal optical densities.
18. A liquid crystal display device according to claim 17, wherein
said first color filter is formed of a plurality of dots comprised
of colors of red, green and blue and the center of each dot of said
first color filter agrees with the center of said openings of said
light reflective layer.
19. A liquid crystal display device according to claim 17, wherein
said second color filter is made of a color photosensitive
material.
20. A liquid crystal display device according to claim 19, wherein
said color photosensitive material comprises a photosensitive
emulsion.
21. A liquid crystal display device according to claim 17, wherein
a backlight device is disposed below a surface of said second
transparent substrate and on the side opposite to said liquid
crystal.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of Japanese Patent
Application No. 2002-377005, filed on Dec. 26, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a transflective liquid
crystal display device that can be used in both transmissive and
reflective modes and a method for manufacturing the same.
[0004] 2. Prior Art
[0005] Transflective liquid crystal display devices, which operate
in a reflective mode utilizing ambient light in bright places and
operate in a transmissive mode utilizing backlight in dark places,
are broadly used, in particular, as display devices in portable
electronic equipment. For example, Japanese Unexamined Patent
Publication No. H10-282488 entitled "Liquid crystal display device"
proposes a liquid crystal display device in which holes for
transmitting light are provided on a reflective layer of a
reflective liquid crystal display device and, at the same time, a
backlight device is provided behind the reflective layer. When this
device is used in the reflective mode, an image is displayed by the
ambient light reflected by the reflective layer disposed behind a
liquid crystal layer and, when this device is used in the
transmissive mode, the image is displayed by guiding the light from
the backlight device to the liquid crystal cell through the holes
provided on the reflective layer.
[0006] However, the device disclosed in Japanese Unexamined Patent
Publication No. H10-282488 has a problem in that, in a color
display mode, color reproducibility is not optimized in both the
reflective mode and the transmissive mode. The reason of this
problem is as follows. When the device is used in the reflective
mode, the ambient light passes through the liquid crystal layer and
a color filter and is reflected by the reflective layer disposed on
the backside of the color filter and, then, passes through the
color filter and the liquid crystal cell again and, then, exits
from the cell and is observed by a user. Therefore, as the incident
light passes through the color filter twice before exiting from the
cell, the transmittance of the light and, thus, the brightness of
the display is reduced by the color filter. As the light passes
through the color filter twice, the color saturation of the light
is increased. In contrast to this, when the device is used in the
transmissive mode, as the light that is originated from the
backlight device disposed behind the cell passes through the holes
disposed on the reflective layer and, then, passes through the
color filter and liquid crystal cell and exits from the cell, the
light passes through the color filter only once. Therefore, the
brightness of the display is not reduced but the color saturation
is reduced. As described above, as the color reproducibility is not
optimized in both the transmissive mode and the reflective mode,
there is a problem in that, if the optical density of the color
filter is optimized for either the transmitting mode or the
reflective mode, the display in the other mode is not
optimized.
[0007] In order to solve the above problem of the liquid crystal
display device shown in Japanese Unexamined Patent Publication No.
H10-282488, other liquid crystal display devices have been proposed
in Japanese Unexamined Patent Publication No. 2000-298271 entitled
"Liquid crystal display element and method for manufacturing the
same", Japanese Unexamined Patent Publication No. 2001-33778
entitled "Liquid crystal display device and method for
manufacturing the same and electronic equipment" and the like. As
these liquid display devices are configured so that the thickness
of the color filter differs between the region above a reflective
layer and the region above openings of the reflective layer, the
same color reproducibility can be obtained in both the transmissive
and reflective modes. For example, by making the thickness of the
color filter above the openings of the reflective layer twice as
large as that of the color filter above the reflective layer, the
thickness the light passes through in the color filter is same in
both the transmissive and reflective modes and, as a result, the
same color reproducibility of the display can be obtained in both
modes.
[0008] However, in the devices described above, in order to provide
the color filter with different thickness between the region above
the reflective layer and the region above the openings, the
reflective layer must be thicker having a two-layer construction
comprised of a resin layer and a reflective layer and, further, two
layers of the color filter must be formed. In the case of a
three-color filter, in order to form the two layers of the color
filter, an exposure and developing process must be repeated six
times and, therefore, the manufacturing process becomes complicated
and the production cost of the liquid crystal display device itself
is increased.
SUMMARY OF THE INVENTION
[0009] In view of the above problems, it is an object of the
present invention to provide a transflective liquid crystal display
device of a novel construction that does not require a complicated
manufacturing process and that can obtain an appropriate color
reproducibility of a display in both a reflective mode and a
transmissive mode, and a method for manufacturing the transflective
liquid crystal display device.
[0010] In order to achieve the above object, according to the
present invention, there is provided a liquid crystal display
device, comprising: first and second transparent substrates; a
liquid crystal that is enclosed between said first and second
transparent substrates; a first color filter that is formed on
either said first or second transparent substrate; a light
reflective layer that has a plurality of openings and that is
formed on said second transparent substrate toward the liquid
crystal; and a second color filter that is formed on said second
transparent substrate on the side opposite to said liquid
crystal.
[0011] When said device is used in the reflective mode, an incident
light that comes on this device from above the first transparent
substrate passes through the first color filter and is reflected by
the reflective layer, passes the first color filter again and exits
from this device and is observed by a user. Therefore, the incident
light passes the first color filter twice. On the other hand, when
this device is used in the transmissive mode, light that is
originated from a backlight device disposed on the backside of the
second transparent substrate passes through the second color filter
and further passes through the openings of the reflected plate and
the first color filter and, then, exits from this device and is
observed by the user. Therefore, as the light from the backlight
passes through the second and first color filters, if the first and
second color filters have the substantially same optical density,
an appropriate color reproducibility of the display can be obtained
in both the reflective and transmissive modes.
[0012] The liquid crystal display device of the present invention
described above is manufactured by a method comprising the steps
of: forming a reflective layer having a plurality of openings and
then a first color filter on a second transparent substrate
sequentially; applying a color photosensitive material on a surface
of said second transparent substrate on the side opposite to that
on which said reflective layer is formed; forming a second color
filter that has a color dot matrix pattern the same as that of said
first color filter by illuminating said color photosensitive
material from above said first color filter through the openings of
said reflective layer; disposing a first transparent substrate
opposed to the surface of said second transparent substrate on
which said first color filter is formed; and filling a liquid
crystal between said first and second transparent substrates.
[0013] According to the manufacturing method described above, the
second color filter mentioned above is formed by exposing and
coloring the color photosensitive material on the surface of said
second transparent substrate on the side opposite to said liquid
crystal by the light transmitting through said first color filter
and by using said reflective layer as an exposure mask. Therefore,
in contrast to the prior art wherein the same number of coloring
processes as the number of colors is needed, the coloring process
must be performed only one time for the second filter and,
therefore, the manufacturing process is simplified significantly
and the production cost of the device is reduced.
[0014] Further, the liquid crystal display device of the present
invention described above is manufactured by a method comprising
the steps of: forming a reflective layer having a plurality of
openings and then a first color filter on a second transparent
substrate sequentially; disposing a first transparent substrate
through a sealing member opposite to and above a surface of said
second transparent substrate on which said reflective layer and
first color filter are formed; applying a color photosensitive
material on a surface of said second transparent substrate on the
side opposite to that on which said first color filter is formed;
forming a second color filter by illuminating said color
photosensitive material from above said first transparent substrate
through said first color filter, said openings being provided on
said reflective layer and said second transparent substrate and
coloring the material; and filling a liquid crystal between said
first and second transparent substrates.
[0015] According to the manufacturing method described above, as
the process for forming the second color filter is performed after
the liquid crystal cell is constituted by the first and second
transparent substrates, there is an effect in that, when the second
color filter is formed, the contamination of the surfaces of the
liquid crystal cell and the damage of the substrates due to
handling of the substrates can be prevented and, therefore, the
liquid crystal cell can be handled easily.
[0016] Still further, the liquid crystal display device described
above is manufactured by a method comprising the steps of: forming
a reflective layer having a plurality of openings and then a first
color filter on a second transparent substrate sequentially;
disposing a first transparent substrate through a sealing member
opposite to and above a surface of said second transparent
substrate on which said reflective layer and first color filter are
formed; filling a liquid crystal between said first and second
transparent substrates; applying a color photosensitive material on
a surface of said second transparent substrate on the side opposite
to said liquid crystal; and forming a second color filter by
illuminating said color photosensitive material from above said
first transparent substrate through said liquid crystal, said first
color filter, said openings provided on said reflective layer and
said second transparent substrate, and coloring the material.
[0017] According to the manufacturing method described above, after
the liquid crystal cell is constituted by the first and second
transparent cell and the liquid crystal is filled into the cell,
the process for forming the second color filter is performed using
the photosensitive emulsion. As a result, dust or other
contaminants can be prevented from being mixed into the liquid
crystal at the time of exposure and developing of the
photosensitive emulsion and, therefore, a liquid crystal display
device having high reliability can be obtained.
[0018] In this connection, said first color filter is formed by
either a photolithography, printing, electrodeposition or inkjet
method. Further, said color photosensitive material is a
photosensitive emulsion and the step of forming said second color
filter comprises the step of developing said photosensitive
emulsion that has been exposed. This photosensitive emulsion is,
for example, a silver chloride emulsion. As the silver chloride
emulsion is sensitive to ultraviolet (UV) light, it is preferable
that the polarizer has a UV screening function.
[0019] Further, the color filters may have three colors of red,
green and blue or three colors of cyan, magenta and yellow.
Further, it may have other combinations of colors. The reflective
layer can be formed by a film of aluminum or silver or alloys
including these metals and is provided with openings at positions
corresponding to regions of each color of the color filters.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 schematically shows a cross section of a liquid
crystal display device according to a first embodiment of the
present invention;
[0021] FIGS. 2(a)-2(f) show steps of a manufacturing process of the
device shown in FIG. 1;
[0022] FIGS. 3(a)-3(f) show steps of a manufacturing process of a
first color filter;
[0023] FIG. 4 shows one step of a manufacturing process of the
device shown in FIG. 1;
[0024] FIGS. 5(a)-5(c) show steps of a manufacturing process for a
plurality of liquid crystal display devices simultaneously
according to a manufacturing method for liquid crystal display
device; and
[0025] FIG. 6 schematically shows a cross section of a liquid
crystal display device according to another embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Hereinafter, preferred embodiments of the present invention
will be described with reference to the drawings.
[0027] FIG. 1 is a schematic cross-sectional view of a
transflective liquid crystal display device according to a first
embodiment of the present invention. The shown embodiment is an STN
liquid crystal display device, wherein transparent substrates 1 and
2, such as glass sheets, constitute a top substrate and a bottom
substrate of a liquid crystal cell, respectively. Then, signal
electrodes 3 are formed on a surface of the top substrate 1 facing
a liquid crystal layer and a common electrode 4 is formed on a
bottom substrate 2. Typically, these are comprised of transparent
electrodes. In this connection, a reflective layer and a first
color filter described below are disposed between the bottom
substrate 2 and the common electrode 4. Then, alignment layers 5
and 6 and a liquid crystal layer 7 are shown. The top substrate 1
is provided with a retardation film 8 and a polarizer 9 on the side
opposite to the liquid crystal layer 7 and the bottom substrate 2
is also provided with a retardation film 10 and a polarizer 11
similarly. Then, a backlight device 12 is shown. The bottom
substrate 2 is provided with the reflective layer 13 that is a
deposited film of aluminum or the like and the first color filter
15 on the side toward the liquid crystal layer 7. The color filter
15 is constituted by a plurality of repetitions of three color dots
of R, G, B. The reflective layer 13 has openings (holes) 16 at
positions corresponding to central positions of each dot of the
color filter 15. Further, a planarizing layer 17 is formed on the
first color filter 15 for planarizing a top surface of the color
filter 15.
[0028] In this device, the bottom substrate 2 is further provided
with a second color filter 18 on the side facing the backlight
device. This second color filter 18 is formed when a photosensitive
emulsion layer applied on the bottom substrate 2 is exposed and
developed by light applied from the direction of the first color
filter 15 by using the reflective layer 13, through which the
openings 16 are formed, as a mask, as described later.
[0029] When the first color filter 15 described above is formed,
the optical density of the color filter is optimized solely with
respect to the color filter 15 so as to obtain proper color
reproducibility when displaying in a reflective mode. The optical
density of the second color filter 18 is optimized to be
substantially similar to that of the first color filter 15. As a
consequence, the transmittance of the light passing through the
second color filter 18 and the first color filter 15 is equal to
that of the light that is reflected by the first color filter 18
and returns toward the user and, therefore, an appropriate color
reproducibility can be obtained in both transmissive and reflective
modes.
[0030] Here, the openings 16 are not necessarily formed at the
central positions of the respective dots (each of which corresponds
to one pixel of the liquid crystal display device) on the
reflective layer 13 and the openings 16 may be offset from the
central positions. Further, each dot does not necessarily
correspond to one opening and a plurality of openings may be formed
in each dot. The ratio of the total area of the opening(s) in one
dot to the area other than the opening(s), or the opening/dot
(pixel) ratio is often about 30-60%.
[0031] Further, an insulating layer may be provided in at least one
of the regions between the top substrate 1 and the alignment layer
5 and between the bottom substrate 2 and the alignment layer 6 to
prevent short circuits between the transparent electrodes on the
top substrate 1 and the transparent electrode on the bottom
substrate 2 due to dust. The configuration of the retardation films
8 and 10, the polarizer 9 and 11 and the material of the liquid
crystal layer 7 may be those that are typically used for STN liquid
crystal display devices, for example, the specific description of
which is omitted here.
[0032] FIGS. 2(a)-2(f) are diagrams showing a process for forming
the first and second color filters 15 and 18, described above, on
the bottom substrate 2 according to a method of the present
invention. First, on a top surface of the bottom substrate 2 shown
in FIG. 2(a), the reflective layer 13 is formed as shown in FIG.
2(b). Next, as shown in FIG. 2(c), a plurality of openings 16 are
formed on the reflective layer 13. The openings 16 are disposed at
positions corresponding to respective regions of each color of the
second color filter to be formed later. Then, as shown in FIG.
2(d), the first color filter 15 is formed on the reflective layer
13. Though the color filter 15 may be formed by any manufacturing
process, an example will be shown in FIG. 3.
[0033] The example of a method for manufacturing the first color
filter 15 will be described with reference to FIGS. 3(a)-3(f).
Here, in FIGS. 3(a)-3(f), for simplicity of description, the
reference numeral 2' indicates the bottom substrate in the step
shown in FIG. 2(d) and, therefore, the reflective layer 13 is
formed on the substrate 2', though not shown, and the openings 16
are formed on the reflective layer 13. First, on the substrate 2'
shown in FIG. 3(a), a layer 150 of a color filter raw material,
which will be developed and patterned later, is formed as shown in
FIG. 3(b). This layer 150 contains a pigment or a dye having a
color such as red. Next, as shown in FIG. 3(c), the layer 150 is
covered by an exposure mask 152 and, then, is exposed to light so
that it is colorized and patterned. Then, the exposure mask 152 is
removed as shown in FIG. 3(d) and, then, unnecessary portions of
the layer 150 are removed by developing or other processes so as to
form one color portion (for example, a red portion) as shown in
FIG. 3(e). Then, a portion of another color of the color filter is
formed by forming a base layer containing a pigment or a dye of the
another color on the bottom substrate 2' and performing the
exposure and developing in a manner similar to the above process.
By repeating this process further once again, a color filter 15, on
which a plurality of dots of red (R), green (G) and blue (B) colors
are formed, is formed as shown in FIG. 3(f).
[0034] FIG. 2(d) shows the first color filter 15 formed on the
bottom substrate 2 as described above. Here, as exemplary
structural values of the color filter 15 and the reflective layer
13, for example, the size of the pixel is 180 .mu.m.times.60 .mu.m
and the diameter of each opening 16 is about 40 .mu.m. The
thickness of the first color filter 15 is about 0.8 .mu.m. The
reflective layer 13 is formed of aluminum by the sputtering method
and its thickness is about 0.15 .mu.m, but the thickness may be
increased to about 0.8 .mu.m by forming the reflective layer of
other materials or disposing a resin film under the reflective
layer. Further, as discussed above, the ratio of the total area A
of the opening(s) in one dot to the area B other than the
opening(s), or the opening (A)/dot (pixel) (A+B) ratio is often in
the range of 30-60%.
[0035] Next, a process for forming the second color filter 18 will
be described. As shown in FIG. 2(e), a photosensitive emulsion
layer 18' is formed by turning the bottom substrate 2 upside down
and applying a silver-halide emulsion to its upper surface by a
spinner, a squeegee or a printing method. Then, as shown in FIG.
2(f), the silver-halide emulsion layer 18' is exposed by using a
white light source, wherein the light from the white light source
is transmitted through the first color filter 15 and passes through
the openings 16 of the reflective layer 13 to impinge on the
photosensitive emulsion layer 18' and expose it. Then, by
developing the photosensitive emulsion layer, the regions
corresponding to the openings 16 are colored according to the color
pattern of the first color filter so that the photosensitive
emulsion layer acts as the second color filter. Here, light sources
other than a white light source may be used for the exposure. For
example, separate light sources may be provided for each of red,
green, blue colors and lit simultaneously or a three wavelength
light source tube may be used.
[0036] As described above, by using the reflective layer 13 as the
light shielding mask (exposure mask) and exposing the
photosensitive emulsion layer 18' to the light passing through the
first color filter 15, the second color filter 18 having a
three-color pattern is formed by one exposure and developing
process. Therefore, the manufacturing process of the second color
filter 18 is simplified significantly in comparison with that of
the first color filter. In this connection, some portions of the
photosensitive emulsion 18' below the reflective layer 13 existing
between the adjacent openings 16 may not be exposed and developed
but, even if there are such portions that are not exposed
adequately, the appearance and display quality of the liquid
crystal display device is not degraded because such portions are
covered by the reflective layer 13 from the viewpoint of the
user.
[0037] After the bottom substrate 2 having the two layers of the
color filters shown in FIG. 2(f) has been formed as described
above, the planarizing layer 17 is formed on the color filter 15
and, then, the common electrode and the alignment layer 6 are
formed in a typical manner. The bottom substrate 2 in this state is
opposed to the top substrate 1, on which the signal electrodes and
the alignment layer are formed separately, so that each electrode
forms the respective pixels and, further, the both substrates are
coupled together through a frame-like sealing member to constitute
the liquid crystal cell. Next, after a liquid crystal is filled
into the cell and the retardation films, the polarizers and the
backlight device are provided appropriately, the liquid crystal
display device of the construction shown in FIG. 1 can be
obtained.
[0038] FIG. 4 is a diagram for describing an alternative
manufacturing method of the second color filter 18 of FIG. 2. In
this manufacturing method, the bottom substrate 2, on which the
reflective layer having holes and the first color filter 15 have
been formed and the electrodes and the alignment layer have been
provided appropriately, is coupled with the top substrate 1, on
which the electrodes and the alignment layer are provided, to
constitute the liquid crystal panel. After or before the liquid
crystal is filled into the liquid crystal panel, the second color
filter 18 is formed on the back of the bottom substrate 2. More
specifically, the photosensitive emulsion layer 18' is formed on
the back of the bottom substrate 2 and, then, light is allowed to
impinge on the panel from the side of the top substrate 1 to expose
the photosensitive emulsion layer 18' through the first color
filter 15 and the openings 16. As a result, the photosensitive
emulsion layer 18' is exposed to have a color pattern identical to
that of the first color filter 15 and, thus, the second color
filter 18 is formed. By providing the retardation films, the
polarizers and the backlight device to the second color filter 18
that has been formed as described above, the liquid crystal display
device shown in FIG. 1 is completed.
[0039] According to the manufacturing method of the liquid crystal
display device as shown in FIG. 4, the operation to form the second
color filter 18 can be performed after the top substrate 1 and the
bottom substrate 2 are coupled together. Therefore, in contrast to
the embodiment shown in FIG. 2, the substrate 2 can be handled
easily when the second color filter is formed. Further, if the
process of application, exposure, developing and the like of the
photosensitive emulsion is performed after the liquid crystal is
filled into the cell, as it is possible to minimize the possibility
that dust or other contaminants are mixed into the liquid crystal
cell while the second color filter is manufactured, the degradation
of image quality due to the dust can be prevented, the probability
of the short circuit between electrodes can be lowered even if the
insulating layer is not provided and, therefore, the reliability of
the liquid crystal display device can be improved.
[0040] FIGS. 5(a)-5(c) are diagrams showing an alternative
manufacturing method of the liquid crystal display device of the
present invention shown in FIG. 4. This manufacturing method is
characterized in that the second color filter is formed
simultaneously for a plurality of liquid crystal cells without
contaminating the inside of the liquid crystal cell before filling
the liquid crystal. Hereinafter, with reference to FIGS. 5(a)-5(c),
this embodiment will be described.
[0041] FIG. 5(a) shows a plurality of cells, each of which
corresponds to one liquid crystal display device, formed on a large
substrate. In FIG. 5(a), two large substrates corresponding to the
top substrate 1 and the bottom substrate 2 are coupled together
through a first sealing member 110 and second sealing members 120
to form a large-sized cell 101. In this state, the liquid crystal
is not filled into each cell 200 enclosed by the second sealing
members 120. These sealing members provide a dual seal and, in each
of the cells 200, the second sealing member 120 with a filling hole
125 is disposed so as to form a cell space 130. The plurality of
cells 200 are encircled by the first sealing member 110, wherein
the first sealing member 110 is provided with a circulation path
connecting the inside and outside of the substrates so that air is
circulated therebetween. In order to form this circulation path,
two openings 121 are provided on the outside and inside of the
first sealing member 110. The first sealing member 110 must be
configured to have a region where portions of the first sealing
member 110 itself are disposed in parallel. Here, functions of the
openings 121 and the first sealing member 110 the portions of which
are disposed in parallel will be described. When the large
plate-like top substrate and the bottom substrate are coupled
together by thermocompression process, with a spacing provided by
the first sealing member 110 and the second sealing members 120, so
as to form the large-sized cell 101, if the space between the top
and bottom substrates is sealed completely, the air at the central
part (inside) of the large-sized cell substrate 101 cannot escape
to the outside and, therefore, the substrate 101 will be destroyed
by the expansion of the internal air due to the heat from the
thermocompression process. The openings 121 are provided to prevent
this problem. On the other hand, the sealing sections 122 and 124,
that are the portions of the first sealing member 110 disposed in
parallel, are provided to prevent liquids, which are used for
cleaning or wet developing in the process after the two substrates
are coupled, from entering into the cells 200.
[0042] FIG. 5(b) shows a strip-like substrate into which said large
plate-like cell 101 is cut along lateral cutting lines X (X1, X2,
X3, X4). In this strip-like substrate, as a plurality of cells are
arranged in a lateral direction and the filling holes 125 of all
the cells are opened in one direction, the liquid crystal can be
filled into all the cells at one time by using a vacuum filling
method. FIG. 5(c) shows one liquid crystal cell 200 into which said
strip-like substrate is cut along vertical cutting lines Y (Y1, Y2,
Y3, Y4).
[0043] Hereinafter, steps of the manufacturing process shown in
FIGS. 5(a)-5(c) will be described. In the state shown in FIG. 5(a),
in each cell 200, the processes shown in FIGS. 2(a)-2(d) have been
completed and, further, the electrodes and the alignment layers
have been disposed on the top and bottom substrates and the top and
bottom substrates are coupled together through the sealing members.
Then, though not shown, a photosensitive emulsion layer is applied
on the back of the large-sized substrate 101 and is exposed
according to the exposure method shown in FIG. 4. Here, it is to be
noted that the liquid crystal is not yet filled into the cell
spaces 130. Then, the wet developing process of the large
plate-like substrate 101 is performed. At this time, the first
sealing member 110, which is made of a sealing material the same as
that of the second sealing members 120 and is provided in advance,
effectively prevents a developer from entering into the spaces 130
through the filling holes 125 of each cell 200. The first sealing
member 110 may have any shape to prevent the developer from
entering. In FIG. 5(a), the first sealing member is configured so
that it makes 1+1/4 turns around the large substrate. It may
alternatively be configured so that it makes 1+ 2/4, 1+3/4 or 2
turns.
[0044] In the processes described above, the second color filter is
formed on all the cells 200 in the large-sized substrate 101 at a
time by once forming, exposing and developing the photosensitive
emulsion layer. Then, after the developing process, the substrate
101, on which the second color filter 18 (see FIG. 1) is formed, is
cut along the lateral cutting lines X1-X4. At this time, the
filling holes 125 are opened on the cutting planes of the cutting
lines X2, X3 and X4. The strip-like substrate shown in FIG. 5(b)
can be obtained by this cutting operation. In this state, a
plurality of filling holes 125 of a plurality of cells are made to
contact with the liquid crystal material and the liquid crystal is
filled into the spaces 130 by controlling the air pressure in the
spaces. After the liquid crystal is filled, the filling holes are
sealed by sealing members made of a resin material. Then, the
strip-like cells are cut along the cutting lines Y1-Y4 shown in
FIG. 5(b) into the liquid crystal cell 200 shown in FIG. 5(c). The
retardation films, the polarizers and the backlight device are
attached to the cell 200 appropriately to obtain the transflective
liquid crystal display device.
[0045] FIG. 6 shows a construction of a liquid crystal display
device according to another embodiment of the present invention. In
contrast to the device shown in FIG. 1, this device is
characterized in that the first color filter 15' is disposed on the
top substrate 1 toward the liquid crystal. Here, the surface of the
color filter 15' is planarized by the planarizing layer 17'. In
this device, the reflective layer 13 is formed on a surface of the
bottom substrate 2 toward the liquid crystal, the photosensitive
emulsion layer that is to be turned into the second color filter 18
is formed on another surface of the bottom substrate 2 on the side
opposite to the liquid crystal and, then, the second color filter
18 is formed by illuminating the photosensitive emulsion layer from
above the first color filter 15' using the reflective layer 13
having the openings 16 as the exposure mask.
[0046] It is to be noted that the retardation film, the polarizer,
the planarizing layer, the backlight device and the like set forth
in the above embodiments are not essential elements to constitute
the liquid crystal display device according to the present
invention and these may be omitted as appropriate depending on the
object, design specification and other conditions of the device.
The relationship of the signal and common electrodes to the top and
bottom substrates may be inverted from the shown example. Further,
though a passive matrix liquid crystal display device is
illustrated in the above embodiments, the present invention may
also be applied to active matrix (TFT, MIM, TDF) devices, of
course. In the case of the TFT liquid crystal display device, one
retardation film may suffice.
[0047] Further, though a cross section of one liquid crystal cell
is shown in the above embodiments, a plurality of cells may be
formed between a pair of transparent substrates.
[0048] As described above in various embodiments, in the device of
the present invention, an appropriate color reproducibility of the
display can be obtained easily in both transmissive and reflective
modes. Therefore, a transflective liquid crystal display device
having high display quality can be obtained. Further, when the
photosensitive emulsion is exposed to light to form the second
color filter, as the patterning exposure is performed by using the
reflective layer on which the openings are provided as the light
shielding mask, the process for forming the second color filter can
be simplified significantly in comparison with the prior art. In
particular, as it is not necessary to change the exposure mask or
perform etching at the time of the patterning process, the
patterning can be performed in a short time and working efficiency
can be improved. As a result, a liquid crystal display device
having high reliability can be obtained at low cost.
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