D E S C R I P T I O N !
Title of Invention: |
COLOR FILTER SUBSTRATE AND I
5 LIQUID CRYSTAL DISPLAY DEVICE I
Technical Field ;
' •
The present invention relates to a color filter [
substrate and to a liquid crystal display device
10 provided with the color filter substrate. In
particular, the present invention relates to a color
filter substrate suitable for driving liquid crystal by
means of oblique electric field caused by applying
voltage between a transparent conductive film formed
15 for the color filter substrate and first and second i
electrodes formed for an array substrate, and a liquid
crystal display device provided with the color filter
substrate.
Background Art
20 In recent years, thin display devices such as a I
liquid crystal display device are increasingly demanded
to enhance the picture quality and power-saving thereof
and to reduce the manufacturing cost thereof. In the
case of the color filter to be employed in such display
25 devices, it is demanded to exhibit sufficient color
purity, high contrast, and flatness in order to obtain
high image quality.
In liquid crystal display device having high image i
quality, various alignment systems and driving systems ':
I
iof
liquid crystal are proposed. Liquid crystal cells
employing these systems includes VA (Vertically
Aligned), HAN (Hybrid Aligned Nematic), TN (Twisted
Nematic), OCB (Optically Compensated Bend), and CPA
5 (Continuous Pinwheel Alighnment). Display device of a
wide viewing angle and high speed response are realized
•
by these liquid crystal cells.
In liquid crystal display devices of VA system
which is easily applicable to high speed response in a
10 wide viewing angle and in which liquid crystal
molecules are aligned vertical to a surface of a
substrate made of glass, and of HAN system which is
effective in wide viewing angle, it is demanded to
obtain further high level flatness in regard to color
15 filter (uniformity of film thickness and evenness of
the surface of color filter) and electric properties
such as dielectric constant. In such liquid crystal
display devices having high image quality, it is a
problem to decrease a film thickness of liquid crystal
20 cell (liquid crystal layer) in order to suppress
coloring of image in oblique viewing direction. In the
liquid crystal display devices of VA system, various
improved modes have been developed in order to solve
such problem, the modes including multi-domain
25 vertically alignment (MVA) mode, patterned vertically
alignment (PVA) mode, vertically alignment electrically
controlled birefringence (VAECB) mode, vertically
i
3
alignment hybrid-aligned nematic (VAHAN) mode, and
vertically alignment twisted nematic (VATN) mode. In i
the liquid crystal display devices of vertical electric I
field system such as VA system in which driving voltage t
• 5 is applied in thickness direction of liquid crystal
layer, it is demanded to obtain higher response of
liquid crystal, wider viewing angle, and higher
permeability. MVA is a technique to attain wide
viewing angle. In this technique, a plurality of
10 structures named as ribs or slits for restricting
alignment of liquid crystal molecules arranged, and
•
domaims of liquid crystal in a plurality of alignment
directions are formed between the ribs in order to
solve the problem of unstable vertical alignment of
15 liquid crystal molecules on application of voltage for
driving liquid crystal (a tilt direction of liquid
crystal molecules on application of voltage, which are
vertically aligned at initial stage, is undeterminate).
JP-A 2005-167243 disclosed a technique of forming
20 domaims of liquid crystal using first and second
structures for restricting alignment (ribs).
When liquid crystal of negative dielectric
anisotropy is employed, liquid crystal molecules
between ribs made of resin tilts in a direction
25 perpendicular to the ribs as viewed from the front on
application of voltage, and are aligned parallel to the
surface of the substrate. In this case, tilt direction
i
^^ 4
of liquid crystal molecules positioned at a center of a
region between the ribs is indeterminate irrespective
of application of voltage, and these liquid crystal
molecules act in spraying alignment or bending I
5 alignment. These alignment turbulence bring about |
i.
rough or uneven display. In the case of MVA system, it t
I
is difficult to minutely control the tilt amount of I
liquid crystal molecules by driving voltage. For that [
reason, a half gray scale display has a difficult t
I
10 point. I
In order to solve the problem, the technique of I
controlling vertical aligned liquid crystal molecules I
by means of oblique electric field caused by applying I
voltage between a transparent electrode on the color I
15 filter substrate side (transparent electrode or third I
electrode) and first and second electrodes on the array I
substrate side is disclosed in Japanese Patent t
Nos. 2859093 and 4459338. The technique disclosed in I
Japanese Patent No. 2859093 employs liquid crystal of I
20 negative dielectric anisotropy, and the technique I
disclosed in Japanese Patent No. 4459338 employs liquid |
crystal of positive dielectric anisotropy. |
The technique of controlling vertical aligned I
liquid crystal molecules by means of oblique electric I
25 field caused by applying voltage between a transparent I
electrode and first and second electrodes as described I
in Japanese Patent Nos. 2859093 and 4459338 is very f
5
effective. It is possible to set a tilt direction of i
liquid crystal molecules by oblique electric field. !;
Since a tilt amount of liquid crystal molecules can be
easily control, it is effective in a halfgray scale i
5 display. |
Even these techniques are, however, insufficient I
in preventive measures against disclination of liquid
crystal. "Disclination" is a phenomenon in which
regions having different transmittances are generated
10 in a pixel (minimum unit in display) by undesirous
alignment disorder.
In the technique disclosed in Japanese Patent i
s
No. 2859093, an alignment controlling window in which a |
transparent conductive film is not formed is arranged
15 in the center of the portion of the opposing electrode
corresponding to a pixel in order to fix the l
disclination in the center of the pixel. The document,
however, dose not disclose the preventive measures
against disclination around the pixel. Though the
20 document discloses the fixing of the disclination in
the center of the pixel, does not disclose the measures
for minimizing the disclination and improving the
response property of liquid crystal.
The technique disclosed in Japanese Patent
25 No. 4459338 is a preferable technique since a
dielectric layer formed on a transparent conductive I
film (transparent electrode) promotes effects of I
oblique electric field. The technique disclosed in I
Japanese Patent No. 4459338, however, has a problem of I
lowering of transmittance or aperture ratio since I
vertically aligned liquid crystal molecules are I
5 remained in the center of the pixel and around the t
pixel even after application of voltage as shown in t
FIG. 7 of Japanese Patent No. 4459338. Where liquid |
crystal of a positive dielectric anisotropy is employed I
(Japanese Patent No. 4459338 does not disclose liquid I
10 crystal of a negative dielectric anisotropy in the I
;,
•r
description and Examples.), it is difficult to raise
transmittance owing to disclination in the center of 1
the pixel. For that reason, it is difficult to employ i
I
the technique disclosed in Japanese Patent No. 4459338 f
i I
15 in transflective liquid crystal display devices. i
Generally, liquid crystal display devices of VA
system or TN system have a fundamental structure in
which liquid crystal is sandwiched between a color •
filter substrate having a common electrode and an array I
20 substrate having a plurality of pixel electrodes for ';
-
driving liquid crystal (for example, transparent [
electrodes having a combteeth shaped pattern and i
connected to TFT elements). In this structure, liquid I
I
crystal is driven by applying voltage between the I
25 common electrode on the color filter substrate and the t
pixel electrode formed on the array substrate side. ;
The pixel electrode and the common electrode are formed •
•
.
•-
I
:•
;:
of a conductive metal thin film made of indium tin
oxide (ITO), indium zinc oxide (IZO), or indium gallium
zinc oxide (IGZO). I
Color filter structure, in which blue, green, and |
5 red pixels are formed above a transparent conductive |
film, is disclosed in FIG. 2 of JP-A 5-26161. The |
technique of forming a color filter on a transparent I
electrode (transparent conductive film) is disclosed in I
the above-described Japanese Patent No. 4459338 (for I
10 example, in FIGS. 7 and 9), though it employs a |
plurality of stripe electrodes and liquid crystal of a I
positive dielectric anisotropy. I
As a technique of improving a brightness and I
luminosity in order to obtain a dynamic display of a |
15 higher picture quality and to extend a range of |
chromaticity, a technique performing four-color display |
in which a yellow pixel or white pixel is added to a |
red pixel, green pixel, and blue pixel. |
These techniques, however, necessitate another I
20 pixel such as a yellow pixel and white pixel together |
with a red pixel, green pixel, and blue pixel, and a i
further active element for driving the other pixel or |
color filter layer for forming a color filter, and thus i
bring about high cost owing to increase in number of |
25 manufacturing steps. Further, these techniques |
necessitate suppression or inactivation of yellow or I
white display in the gradation display range in which
"
I
8
yellow or white display having high brightness is not I
necessary, and do not bring about effective rise of I
brightness. Furthermore, these techniques necessitate I
control of color temperature of a backlight and I
5 adjustment of pixel areas of different colors for I
obtaining a white balance. In addition, there is a I
problem that yellowish tone is strengthened in a I
reflective display. For example, a special blue filter I
shown in Jpn. Pat. Appln. KOKAI Publication No. 2005- I
10 352451 is necessary to suppress the yellowish tone. I
Disclosure of Invention I
Problem to be solved by the Invention I
The present invention has been accomplished in I
view of the aforementioned circumstances and hence I
15 objects of the present invention are to provide a color I
filter substrate which has an improved gray scale I
display together with an improved response property, |
and enables a high brightness display, and to provide a I
liquid crystal display device which is equipped with I
20 such a color filter substrate. |
Solution to the Problems I
According to a first aspect of the present I
invention, there is provided a color filter substrate I
for a liquid crystal display device performing an •
25 ordinary display for a gray scale display and a dynamic ;
display for a bright display, which comprises a
transparent substrate; a transparent conductive film
^
;
® 9
formed above the transparent substrate; a black matrix
formed above the transparent conductive film and having [
a pixel region which is an opening partitioned into a
polygonal pixel shape having two parallel sides; a
5 first transparent resin layer formed so as to cover :
portions corresponding to the two lateral sides of the I
black matrix; a color layer formed for the pixel
region; and a second first transparent resin layer
formed above the color layer and having a linear
10 depression passing a center of the pixel region.
According to a second aspect of the present invention, there is provided a liquid crystal display
device which is equipped with the above described color [
filter substrate.
15 According to a third aspect of the present |
invention, there is provided a liquid crystal display
device which comprises a color filter substrate l
• including a transparent substrate, a transparent f
j
conductive film formed above the transparent substrate, \ I 20 a black matrix formed on the transparent substrate and f
having pixel regions which are openings partitioned I
into polygonal pixel shapes respectively having two I
parallel sides, a first transparent resin layer, and |
color pixels formed of a plurality of color layers I
25 formed above the pixel regions; an array substrate I,
arranged to oppose to the color filter substrate and |
provided with elements for driving liquid crystal, the
I
elements being arranged in a matrix form; and a liquid
crystal layer interposed between the color filter
substrate and the array substrate, wherein the first
transparent resin layer and color layer overlap along 5 the black matrix in the pixel region, the array
substrate includes a first electrode and a second
electrode, which are of combteeth shape, made of
conductive metal oxide, and are transparent in visible [
light range, the second electrode are arranged beneath I
10 the first electrode with an insulating layer interposed l
therebetween, and the second electrode protrudes from j
I
an edge of the first electrode toward the first
transparent resin layer in a plane view. I
i
Brief Description of Drawings i
i.
15 FIG. 1 is a cross-sectional view schematically
illustrating a liquid crystal display device according I
to one embodiment of the present invention;
FIG. 2 is a cross-sectional view illustrating an
i
initial alignment state of vertically aligned liquid f
20 crystal molecules on a green pixel of the liquid I
crystal display device shown in FIG. 1; '.
FIG. 3 is a view explaining a motion of liquid crystal molecules which begin to tilt immediately after application of driving voltage in the liquid crystal
I
25 display device shown in FIG. 1; |
I
FIG. 4 is a view illustrating an alignment state | I
of liquid crystal molecules in white display (green I
I
i
I
•ift r
color display in the figure) after application of i
driving voltage in the liquid crystal display device i
shown in FIG. 1; j
FIG. 5 is a view illustrating an alignment state
5 of liquid crystal molecules in high brightness display ;
after application of higher driving voltage in the
liquid crystal display device shown in FIG. 1;
FIG. 6 is a view.illustrating vertically aligned I
liquid crystal molecules near a first electrode of the I
10 liquid crystal display device shown in FIG. 1 in which
the first and second electrodes have combteeth shaped
pattern; [
FIG. 7 is a view illustrating motions of liquid •
crystal molecules and electric lines of force :
15 immediately after application of driving voltage in the '•
liquid crystal display device shown in FIG. 6; ^
FIG. 8A is a plan view illustrating the pattern of
the first electrode for dividing into four motion
directions of liquid crystal molecules;
20 FIG. 8B is a view illustrating the first and
second electrodes;
FIG. 9 is a plan view illustrating one pixel
portion of the first electrode shown in FIG. 6; I
I
FIG. lOA is a sectional view illustrating a part f
I
25 of the color filter substrate according to Example 1;
FIG. lOB is a plan view illustrating a part of the color filter substrate according to Example 1; [
J
•
:
;
12
FIG. IIA is a sectional view illustrating a part
of the color filter substrate according to Example 2; I
FIG. IIB is a plan view illustrating a part of the
color filter substrate according to Example 2;
5 FIG. 12 is a sectional view illustrating a part of
a liquid crystal display device according to Example 4;
FIG. 13 is a view explaining an embodiment in i
i
which two TFT elements are arranged in one pixel, and a
luminosity of dynamic display is adjusted independently
10 for each TFT element;
FIG. 14 is a plan view illustrating a pattern of a
i
first electrode having an aperture of parallelogram
shape;
FIG. 15 is a plan view illustrating a pattern of a
15 first electrode having an aperture of parallelogram j
shape; and
FIG. 16 is a plan view illustrating a pattern of a
first electrode applicable to one embodiment of the
L
present invention.
20 Best Mode for Carrying Out the Invention A color filter substrate according to a first
t
aspect of the present invention is a color filter substrate for a liquid crystal display device :
performing an ordinary display for a gray scale display 25 and a dynamic display for a bright display, and
comprises a transparent substrate, a transparent conductive film formed above the transparent substrate, :
:
a black matrix formed above the transparent conductive I
film and having a pixel region which is an opening
partitioned into a polygonal pixel shape having two
parallel sides, a first transparent resin layer formed
5 so as to cover portions corresponding to the two
parallel sides of the black matrix, a color layer E
formed for the pixel region, and a second transparent
resin layer formed above the color layer and having a
linear depression passing a center of the pixel region.
10 In the color filter substrate described above, the
color layer may be partitioned into a ordinary display
region formed directly above the transparent conductive
film at the center of the pixel region, and a dynamic
display region formed above the first transparent resin
15 layer formed so as to cover portions corresponding to I
the two parallel sides of the black matrix. l
A thickness A of the first transparent resin layer f
between the surface of the transparent conductive film ^
formed above the transparent substrate and a bottom of
20 the linear depression, a total thickness B of the color |
i.
layer and the second transparent resin layer in the I
I I
ordinal display region, and a total thickness C of the r
first transparent resin layer, the color layer and the I
second transparent resin layer in the dynamic display
25 region may satisfy a relationship of A>B>C. ;
Further, a total thickness from the black matrix I
to the second transparent resin layer above the black
•
•
I
s
^^ 14
i
matrix may be larger than the thickness C in the
dynamic display region. ;
A liquid crystal display device according to a
second aspect of the present invention includes the
5 color filter substrate described above. >
The liquid crystal display device described above
may include the color filter substrate, an array
substrate arranged to oppose to the color filter f
substrate and provided with elements for driving liquid
i
10 crystal, said elements being arranged in a matrix form,
I
and a liquid crystal layer interposed between the color
filter substrate and the array substrate. The array
substrate may include a first electrode and a second electrode to which different voltages are applied in
15 order to drive liquid crystal. l
Liquid crystal molecules in two regions formed by l
t
symmetrically dividing the pixel region with a straight
line may act to tilt to opposite directions to each I
other when an operating voltage is applied between the r
20 first electrode and the second and third electrodes,
ithe
third electrode being the transparent. j^
i
The pixel region may be point-symmetrically ;
i-
Idivided
into four operating regions with regard to a i
center of the pixel region in a plane view when the |
25 liquid crystal molecules act depending on a driving
voltage applied thereto. IThe
first electrode may have a combteeth shaped ;
15
pattern and connected to active elements driving liquid
crystal, the second electrode may have a combteeth
shaped pattern and arranged beneath the first electrode
with an insulating layer interposed therebetween, and
5 the second electrode protrudes from an edge of the
first electrode toward a side of a pixel in a plane i
view.
The first and second electrodes may be made of ;
conductive metal oxide that is transparent in a visible
10 light range.
A liquid crystal display device according to a
third aspect of the present invention which comprises a color filter substrate including a transparent -
substrate, a transparent conductive film formed above <
i
•
15 the transparent substrate, a black matrix formed on the transparent substrate and having a pixel regions which
are openings partitioned into polygonal pixel shapes ;
r
respectively having two parallel sides, a first r
f
transparent resin layer, and color pixels formed of a •
20 plurality of color layers formed above the pixel [
regions, an array substrate arranged to oppose to the s
color filter substrate and provided with elements for !
driving liquid crystal, said elements being arranged in
a matrix form, and a liquid crystal layer interposed
25 between the color filter substrate and the array
substrate, wherein the first transparent resin layer
and color layer overlap along the black matrix in the
i
16
pixel region, the array substrate includes a first
electrode and a second electrode, which are of
combteeth shape, made of conductive metal oxide, and
are transparent in visible light range, the second
5 electrode are arranged beneath the first electrode with
an insulating layer interposed therebetween, and the
second electrode protrudes from an edge of the first
electrode toward the first transparent resin layer in a :
plane view.
10 The first electrode may not be arranged in that a
position above the array substrate in which the first
transparent resin layer is arranged in the plane view.
The liquid crystal having a negative dielectric •
anisotropy may be employed. ;
15 According to aspects of the present invention
described above, there is provided a color filter
substrate which has an improved gray scale display •
together with an improved response property, and
enables a high brightness display, and a liquid crystal
20 display device which is equipped with such a color i
filter substrate. In particular, according to aspects ;
of the present invention, there is provided a color I
filter substrate which enables vibrant display by |
strengthening luminosity without upsetting color 25 balance and increasing number of TFT elements, and a I
liquid crystal display device which is equipped with i
such a color filter substrate. |
I
i
^ 17
:
r
Further, according to aspects of the present
invention, there is provided a liquid crystal display <
i
device that enables reflective type display of well- I
;
balanced color without exhibiting yellowish tone. [
t
5 Furthermore, according to aspects of the present
t
invention, there is provided a liquid crystal display |
device which can display a bright image without
increase in number of pixels such as a white pixel or
yellow pixel, so that it enables bright display in
10 comparison with prior devices by canceling
••
disclination, which lowers transmittance factor of
liquid crystal, without a dead pixel such as a white J
pixel at ordinary gray scale display.
I
There will be described various embodiments of the I
f.
I
15 present invention as follows.
I
The target of one embodiment of the present
t
invention is a liquid crystal display device of a
normally black display type. The premise of one
embodiment of the present invention is a liquid crystal
20 display device including a color filter substrate, an [
array substrate provided with driving elements such as
TFT and opposed to the color filter substrate, and a !
liquid crystal layer interposed between the color -
filter substrate and array substrate which are bonded
25 to each other. The technique of the embodiment can be
applied to the liquid crystal display device employing
liquid crystal which orientates in parallel with the I
i
^ 18
substrate at an initial stage and perpendicularly with
the substrate on application of driving voltage. In
addition, the present embodiment utilizes an oblique
electric field generated in the electrode arrangement [
I
5 including first and second electrodes formed on the I
side of the array substrate, on which different
voltages are applied, and a transparent electrode
acting as a third electrode and formed on the color
filter substrate. The first electrode may have a
10 combteeth shaped pattern, and the longitudinal :
direction of the pattern may be in parallel with the
first transparent layer. Where one pixel is divided
into four alignment direction, the pattern may be an ;
oblique combteeth shaped pattern so that the four ;
15 alignment direction has point symmetry in regard to the
center of the pixel as shown in FIGS. 8A and SB.
FIG. 8A shows the arrangement of the combteeth shaped |
electrode, and FIG. 8B is the enlarged view of the l
I
combteeth shaped electrode. As shown in FIG. 8B, the I
20 second electrode protrudes from an edge of the first |
f
electrode in the direction of the first transparent f
f'
layer. I
I
The present inventors have found that the >
symmetric inclination of liquid crystal molecules in :
25 regard to the center of the pixel can be generated by "
utilizing alignment of the liquid crystal molecules at >
the step formed in the color filter symmetrically in
•
19
regard to the center of the pixel. In addition, the
present inventors have found that, by utilizing the
oblique electric field described above, there is
provided liquid crystal display devices which show
5 rapid response of liquid crystal and high transmittance
factor due to no disclination.
It is necessary to form the step in the color
t, filter or color pixel symmetrically and in one ;
direction in regard to the center of the pixel. That
•
10 is to say, it is necessary to form the step having a f
thick portion or thin portion in one direction so that
the inclination direction of liquid crystal molecules
are symmetric about the center of the pixel. The step
portion is formed to utilize the alignment of liquid
15 crystal in the shoulder portion for the inclination of liquid crystal. Incidentally, the operation of liquid
crystal will be explained in Examples described below.
Difference in height at the step ranges preferably
!
•
between 0.5 ]im and 2 ]jm. When the difference in height
20 is less than 0.5 \im, sufficient effect as a trigger for I
the inclination of liquid crystal may no be obtained. i
I
When the difference in height is more than 2 \im, liquid j
f
crystal may not flow smoothly in the manufacturing !
process of liquid crystal cells. The step can be |
25 easily formed by forming the black matrix or first
transparent resin layer before coating of the color
layer.
20
The linear depression of the first resin layer can
be formed linearly and in parallel with a side of a
polygonal pixel shape having two lateral sides.
Alternatively, it can be formed in the shape of a cross
5 as viewed from above. Though it is not necessary to
limit the method of forming the linear depression, a optical method using a photomask (photolithography) is
preferably employed due to its simplicity. The f
combteeth shaped pattern of the first electrode can be i
{
10 arranged in parallel with the linear depression.
•
In order to form the step enabling the alignment ;
of liquid crystal described above, it is desirable that I
thickness A of the first transparent resin layer I
•f between the surface of the transparent conductive film }
15 formed on the transparent substrate and the bottom of
the linear depression of the first resin layer, total
thickness B of the color layer and the second
transparent resin layer in the ordinal display region, j
and total thickness C of the first transparent resin |
20 layer, the color layer and the second transparent resin '
layer in the dynamic display region satisfy an i
>
inequality of A>B>C. '
t
Further, it is desirable that the total thickness '
between the surface of the black matrix and the surface ;
25 of the second transparent resin layer is larger than
[
thickness C in the dynamic display region.
Incidentally, "ordinary display" in the present '•
'-
21
invention means a gray scale display in which a wellknown
color filter having a color layer containing
organic pigment dispersed therein is applied to a
liquid crystal display device. On the other hand, in j
5 dynamic display, a color layer having a thickness
smaller than that of the color layer in the ordinary
display is employed. Thus, in dynamic display, a color
layer having a transmittance factor higher than that of
the color layer in the ordinary display is formed. In
10 dynamic display, for example, it is an additional condition to display by applying driving voltage higher •
than that in ordinal display to liquid crystal. In
other word, the dynamic display can be performed when
it is necessary to obtain more bright display effect 15 than that in the ordinary display, or to supplement brightness under a bright atmosphere out of doors.
There will now be explained in brief technical ;
terms used in the specification.
"Black matrix" is a light-shielding pattern '
i,
20 arranged around a picture cell or on the both side of a
i
picture cell, which is a minimum unit of display, in
order to increase a contrast of display. "Lightshielding
layer" is a light-shielding coating
containing a transparent resin and light-shielding
25 pigment dispersed in the transparent resin, and has a
photo-sensitivity. The light-shielding layer is :
patterned by means of photolithography including .
Q I
22 I
light-exposure and development. |
"Pixel" is formed in an opening of the black |
matrix and is the same term with picture element. In I
general, the pixel has a polygonal shape with two I
5 opposed lateral sides. The polygon with two opposed I
lateral sides includes, for example, a quadrilateral i
such as rectangle, a parallelogram as shown in FIGS. 14
and 15, a hexagon, a polygon having a bend in the
center of the pixel as shown in FIG. 16.
10 "Color layer" is formed in the pixel by patterning
I
a coating containing a transparent resin and organic
pigment dispersed in the transparent resin by means of
photolithography. The portion of the color layer
positioned on the linear resin layer and the overlap
15 portion on the black matrix are also called color
layer.
In the present embodiment, it is possible to f
employ both liquid crystal of negative dielectric anisotropy and liquid crystal of positive dielectric !;
20 anisotropy. For example, it is possible to employ
nematic liquid crystal having a birefringence of about [
I
0.1 at a room temperature as liquid crystal of negative
dielectric anisotropy. Since liquid crystal of I
positive dielectric anisotropy can be selected within a
25 wide range, various liquid crystals can be employed as '
liquid crystal of positive dielectric anisotropy.
Though it is not necessary to limit the thickness of I
J^ I
23 j
the liquid crystal layer. And of the liquid crystal I
layer, which can be effectively used in the present I
embodiment, ranges between about 300 nm and 500 nm. I
Furthermore, the present invention employs liquid I
5 crystal molecules which orientate in parallel with a I
substrate. In the case of the liquid crystal molecules I
which orientate in parallel with a substrate at the
initial stage, the liquid crystal molecules start to
rise vertically with the substrate and thus light
10 permeate through the liquid crystal layer. Where the !
Jliquid
crystal orientating in parallel with a substrate i
is employed, it is necessary to rubbing-treat an
alignment film in order to unitarily set the alignment
direction of the liquid crystal molecules. On the
15 other hand, where the liquid crystal orientating
vertically with a substrate is employed, rubbing
treatment can be omitted. From this viewpoint, the
f
liquid crystal orientating vertically with a substrate f
[
can be preferably employed. l
|.
20 It is possible to employ liquid crystal having a
fluorine atom in a molecular structure (called fluorine
based liquid crystal hereinafter). Since a high [
electric field is generated in the protruded portion of >
the first and second electrodes when a driving voltage '
25 is applied therebetween, it is possible to employ !
liquid crystal having a dielectric constant lower than I
that of the liquid crystal employed in the prior I
«
24 I
vertical alignment system (liquid crystal having a |
small dielectric anisotropy), such as fluorine based |
liquid crystal. In general, liquid crystal having a I
small dielectric anisotropy has a low viscosity and I
5 brings about a high-speed response on applying electric
field of the same strength. Further, since fluorine
based liquid crystal has a low dielectric constant, it
draws only small amount of ionic impurities. For that
reason, such liquid crystal does not bring about
10 deterioration of performance such as drop of voltage
;^ t
keeping factor due to ionic impurities, and has a merit
i
that irregular display is hardly caused.
In the liquid crystal display device of the i
present embodiment, conductive metal oxide such as ITO
15 described above can be employed as a material of the (
first and second electrode on the array substrate side.
I
Alternatively, metal having conductivity higher than J
that of metal oxide can be employed. Further, in the
case of the reflective or transflective type liquid
•
20 crystal display device, it is possible to use a thin
film made of aluminum or aluminum alloy as either one I
of the first electrode and second electrode. As shown ;
f
in FIG. 1, the fist electrode 1, second electrode 2, f
and metal wiring of active elements are formed through i
25 a insulating layer 22 made of silicon nitride (SiNx) or ;
silicon oxide (SiOx). In FIG. 1, TFT and metal wiring I
connected to TFT are omitted. Incidentally, The I
;
(
25 I
technique of forming a gate wiring and source wiring by i
a single layer made of aluminum alloy having a low contact resistance with ITO of conductive metal oxide
is disclosed in JP A-2009-105424.
5 It is possible to increase aperture ratio of a
pixel by forming a thin film of TFT, which is an active
element, by for example, oxide semiconductor. Such
oxide semiconductor includes complex metal oxide of
Indium, gallium, and zinc (IGZO).
I
10 In the present embodiment, though relative ji
dielectric constant of the color layer is a relatively
important property, it is unitarily determined
depending on a ratio of amount of organic pigment to be
added as a colorant to amount of transparent resin.
15 For that reason, it is difficult to alter greatly [
relative dielectric constant. In other word, species
and content of the organic pigment are set in
i
consideration of color purity necessary for the liquid
crystal display device, whereby relative dielectric i
20 constant of the color layer is almost determined. Incidentally, it is possible to obtain the color layer having relative dielectric constant of 5.0 or more by ]
increasing the content of the organic pigment in the I
I
I
color layer and thinning the color layer. Further, it I
25 is possible to elevate the relative dielectric constant
of the color layer in some degree by employing high '
refractive index material as a transparent resin. The •
26 j
relative dielectric constant of the color layer |
containing organic a pigment ranges between about 2.9 I
and 4.5. I
The thickness of the color layer or transparent I
5 resin layer may be optimized in relation to a cell gap I
of the liquid crystal display device (thickness of the
i
liquid crystal layer). From the viewpoint of necessary ;
electric property, it is possible to thicken the liquid
crystal layer when the color layer or transparent resin
10 layer becomes thin. When the color layer or
transparent resin layer becomes thick, it is possible
to thin accordingly the liquid crystal layer.
Incidentally, the transparent resin layer is the same
member with a protective layer made of acrylic resin,
15 etc. in Examples described later.
In the present invention, the liquid crystal
display device is applied to dynamic display, and area
ratio between the ordinary display region and dynamic l
display region in one pixel is adjusted, thereby ;
20 providing the liquid crystal display device of low I
electricity consumption. By controlling the dielectric
constant and thickness of the color layer and
Itransparent
resin layer, it is possible to make a I
difference in driving voltage of ordinary display and r
25 dynamic display. The driving of liquid crystal by
means of oblique electric field in the present
invention has a large effect on the dynamic display.
G I
27 I
It is not necessary to limit the thickness of the I
color layer in the dynamic display region. When the I
thickness of color layer in the dynamic display region |
is one-third to one-fourth of that in the ordinary l
5 display region, coloring can be sufficiently I
recognized. I
In the liquid crystal display device of initial I
vertical (perpendicularity) alignment type or initial j
horizontal alignment type, when driving voltage is t
10 applied in order to display intermediate tone image, r.
yellowish image may appear. In the present embodiment,
this undesirable coloring can be reduced by finely I
i
adjusting the thickness of the color layer formed on
the first transparent resin layer. In order to reduce
15 appearance of the yellowish image, transmittance factor
of the blue pixel may be raised. A simple method for
realizing the raising of transmittance factor of the •
blue pixel is to increase the width or height of the i
first transparent resin layer formed in the blue pixel,
>,
20 thereby to increase relatively the amount of blue
transmitted light. In reverse, it may be possible to
decrease the width or height of the first transparent '
resm layer formed m the red pixel and green pixel. [
Where the width or height of the first transparent
25 resin layer is adjusted to alter the area of the I
dynamic display region, the transmittance factor of the I
color layer can be adjusted to control color balance. I
28 i
The color balance can be controlled also by adding a
small amount of colorant to the first transparent resin
layer.
Where a retardation layer is incorporated in the
5 color filter substrate of the present embodiment, the
retardation layer can be formed of a polymerizable
liquid crystal compound having retardation and
containing a curing agent such as a photosensitive
polymerization initiator and photosensitizer. The
10 first transparent resin layer or a part of the first
transparent resin layer can be formed of the I
retardation layer. I
There will be described the functions of the I
transparent conductive film as a third electrode, |
15 linear depression of a second transparent resin layer, j
and step formed by laminate of the first transparent I
resin layer color layer as follows. |
FIG. 1 is a model view showing a liquid crystal |
display device according to one embodiment of the |
20 present invention. This liquid crystal display device |
includes a color filter substrate for liquid crystal |
display device (abbreviated to color filter substrate I
hereinafter) 11 and an array substrate 21 which are |
bonded to the each other with liquid crystal 17 I
25 interposed therebetween. The color filter substrate 11 I
includes a third electrode 3 of transparent conductive |
film, a black matrix 5, a first transparent resin layer I
;
•
^ 29
I
[
4, a green pixel 14, a red pixel 15, a blue pixel 16,
and a second transparent resin layer 18 which are !
:•
formed on a transparent substrate 10a, respectively. |
The second transparent resin layer 18 has a linear
5 depression 23 passing a center of a pixel region
partitioned by the black matrix 5.
The array substrate 21 is constructed such that a ,
first electrode 1 and a second electrode 2 are formed ;
on a transparent substrate 10b with an insulating layer
10 22 interposed therebetween. In FIG. 1, an alignment r
layer, polarizer, and retardation plate are omitted.
The omitted alignment layer may be formed of a •
polyimide based organic polymer film that is cured by |
heating. One to three retardation plates laminated on {
•
15 the polarizer may be used.
-
FIG. 2 is a sectional view showing an alignment ^
state of vertical-aligned liquid crystal 17. ;
Incidentally, the polarizer is arranged in crossed I•
•
Nicols, thereby to provide a normally black type liquid
20 crystal display device. FIG. 2 shows an alignment ^
state of liquid crystal molecules 17a, 17b, 17c, and
17d of the vertical-aligned liquid crystal 17. :
r
Almost liquid crystal molecules are aligned
vertically with the surface of the green pixel 14 in
25 the ordinal display region and dynamic display region.
•
However, the liquid crystal molecules 17b and 17c near i
r
the shoulder potion 18b and 18c of the linear ;
•
30
depression 23, and the liquid crystal molecules 17a,
17b, 17c, 17d, 17e and 17f near the shoulder potion
18a, 18b, 18c, 18d, 18e and 18f are somewhat obliquely
aligned at initial stage.
5 When a driving voltage is applied to the
i
electrodes in a state in which the liquid crystal
molecules 17a, 17b, 17c, and 17d are obliquely
inclined, the liquid crystal molecules 17a, 17b, 17c,
and 17d tilts in the direction of the arrow as shown in
10 FIG. 3. Since the liquid crystal molecules near the '•
linear depression 23 of the second transparent resin layer 18 is near the third electrode 3 of a transparent
conductive film due to the presence of the linear
depression 23, voltage is easily applied, and those 15 liquid crystal molecules start to incline immediately •
t
after application of voltage. This inclination of the
liquid crystal molecules trigger the inclination of the
neighboring liquid crystal molecules, and the liquid J
crystal molecules incline in the direction of the
20 center of the pixel on which the first transparent
resin layer is formed, as shown in FIG. 4, whereby ]
•
light transmits to cause green display. Since the
liquid crystal molecules 17a, 17b are obliquely
inclined at initial stage, they are apt to incline in ;
25 the direction of the arrow on application of driving
voltage. That is, the ordinary display region shown in
FIG. 4 causes green display in the ordinary gray scale
•
i
31
display.
FIG, 4 is a view showing an alignment state of the
liquid crystal molecules in white display (since FIG. 4
shows the green pixel, display color is green) after
5 driving voltage is applied. As shown in FIG. 4, the
liquid crystal molecules in the ordinary display region ;
are inclined nearly in parallel with the surface of the
substrate. The liquid crystal molecules in the dynamic
display region remain aligned vertically with the
10 surface of the substrate in green display in the I
ordinary gray scale display (in FIG. 4, ordinary
display region), or do not sufficiently tilt. "The
dynamic display region including the first transparent i
r
resin layer, therefore, cause black or dark display.
15 Incidentally, even if an alignment treatment such as
rubbing is not performed, the liquid crystal molecules ;
r
17a, 17b, 17c, and 17d near the shoulder portions 18a,
18b, 18c, and 18d of the linear depression 23 and the
convex portion tilt virtually. I
t
20 A light-shielding layer may be arranged on the I
•
shoulder portions of the linear depression, convex i-
•
portion and transparent resin layer in advance. The
light-shielding layer may be formed in the same forming ;
step with that of the black matrix. Alternatively, a
25 metal wiring on the array substrate side may be used as
the light-shielding layer.
Incidentally, inclination directions of the liquid
•
32
crystal molecules are reverse in the half opposite side
(right side) of the green pixel 14. This means that it
is possible to optical-compensate symmetrically in the
pixel in the intermediate tone display, and to secure a
5 wide viewing angle without forming four domains like an
MVA liquid crystal device. In the intermediate tone
(the state in which the liquid crystal molecules are
obliquely inclined), the liquid crystal molecules in a
half part of the pixel and in another half part of the
10 pixel are obliquely inclined in the opposite direction.
These half parts of the pixel are optically leveled to
extend a viewing angle.
FIG. 5 is a view showing alignment of liquid I
crystal on application of higher driving voltage. That ;
15 is, the liquid crystal molecules in the dynamic display '
region are inclined vertically with line of electric f
[
force (in parallel with the substrate 10b) with •
i
application of high voltage. According to the '
alignment of liquid crystal molecules, light transmits ;
20 the liquid crystal layer in the dynamic display region.
The color layer having a high transmittance factor is |.
formed on the first transparent resin layer 4 in the
dynamic display region, and therefore, a bright green :
image is displayed in the dynamic display region.
25 Incidentally, since the transparent resin layer 4 and ;
the color layer 14, 15, 16 are thickly formed on the
third electrode in the first in the dynamic display
!
I
region, it is necessary to apply voltage higher than
that in the ordinary display region.
The driving voltage applied to the first and
second electrodes may be shifted in order to ease image
5 persistence. Where one pixel is driven by two or more
active elements, timing of driving voltage and waveform
of applying voltage to one active element may be
controlled.
The behavior of the liquid crystal molecules near
10 the color filter substrate is described above. In the
<
liquid crystal display device according to another
embodiment of the present invention, the liquid crystal :
molecules on the array substrate side also inclines in I
the same direction with that on the color filter I
15 substrate side. Those examples using liquid crystal I
having negative dielectric anisotropy is explained as I
follows. I
In the liquid crystal display device shown in I
FIG. 6, the first electrode is constituted by combteeth
20 shaped electrode la, lb, Ic, Id, and the second
electrode is constituted by combteeth shaped electrode
2a, 2b, 2c, 2d. The liquid crystal molecules 37a, 37b, ;
37c, 37d near the first electrode la, lb, Ic, Id are I
aligned vertically with the substrate when no voltage
25 is applied. ;
In the liquid crystal display device shown in
FIG. 6, the second electrode 2a, 2b, 2c, 2d is
.
i
i
34
protrudes from an edge of the first electrode la, lb,
Ic, Id in order to tilt the liquid crystal molecules
37a in the direction of the protrusion in the center of
the pixel during application of the driving voltage.
5 Length 28 of the projection can be controlled by
adjusting kind of liquid crystal material, driving
voltage, thickness of liquid crystal cell, etc. Small
width of 1 to 5 \im suffices for width 28 of the
projection. Overlapping width of the first electrode
10 la, lb, Ic, Id and second electrode 2a, 2b, 2c, 2d is i
denoted by 29. Alignment film is omitted in the
figures. If necessary, the overlapped portion can be
used as an auxiliary capacitor.
i
FIG. 7 shows motions of the liquid crystal
15 molecules 37a, 37b, 37c, 37d, and the lines 30a, 30b,
30c, 30d of electric force, immediately after applying i
•
of driving voltage on liquid crystal molecules. The i
;
liquid crystal molecules 37a, 37b, 37c, 37d are ;
inclined in the direction of the lines of electric
20 force when voltage is applied. Since the tilting I
direction of those liquid crystal molecules are the I
same as that of the liquid crystal molecules 17a, 17b, |
17c, 17d shown in FIG. 3, the liquid crystal molecules I
in the green pixel 14 shown in the figure I
25 instantaneously tilt in the same direction, and thus |
greatly improving a response property of liquid |
crystal. |
Incidentally, the directions of projections of the
second electrodes from an edge of the first electrode
are preferably symmetric with respect to a point or a
line of the center of the pixel, that is, are reverse
5 to each other. Further, it is desirable that
projections of the second electrodes trend toward the
first transparent resin layer 4 or the protrusion 24.
The combteeth shaped electrode may have a pattern of
V-shape or oblique shape. Alternatively, the first and
10 second electrodes may have a combteeth shaped pattern
in which the direction of the combteeth are altered in
one-fourth parts of the pixel at an angle of 5° to 45°.
Thus, when the driving voltage is applied to the liquid
crystal layer, motions of the liquid crystal molecules ''
15 are classified into four motions that are symmetric
!
;
with respect to a center point, and the display region
of the pixel is divided into four display regions. In
;
this case, the combteeth of the combteeth shaped
electrodes can be inclined in the direction of 45° from I
20 the center line of the pixel. It is desirable that I
these electrode patterns are symmetric with respect to •
;
a point or a line of the center of the pixel. Number
of the combteeth of the first and the second i
r
electrodes, a pitch between the combteeth, and a width i
25 of the combteeth can be properly selected. FIG. 9 i
shows an example of a pattern of the first electrode
that is applicable to the present invention.
•
Incidentally, though a driving voltage is applied
to the first electrode, the second electrode and the
third electrode can be connected with common potential.
The overlapped portion 29 of the first electrode and
5 the second electrode shown in FIG. 6 can be used as an i
auxiliary capacitor. ;
The other examples of the patterns of the first ;
electrode viewed from above are shown in FIGS. 9, 14,
• 15, and 16. In FIGS. 9, 14, 15, and 16, reference [
10 numeral 25 denotes an opening (polygonal shape of the
colored pixel) of the black matrix 5, and reference =
numeral 9 denotes a tilt direction of the liquid
crystal molecules. FIGS. 14 and 15 show two openings • of the pixels having different tilt angles. When a
'•
15 driving voltage is applied to the first electrode 1, J
and the second electrode and the third electrode are [
connected with common potential, the liquid crystal :
r
molecules incline in the direction 9 in every half
r
pixel. Further, In parallelogram pixels having
20 different tilt angle shown in FIGS. 14 and 15, four
different tilt direction of liquid crystal can be set, f
and thus providing a liquid crystal display device of
;
I
wide viewing angle. :
Number of the combteeth members of the first and
25 the second electrodes in the width direction of the
opening of the pixel, density of the combteeth shaped
members, and a space of the combteeth shaped members •
•
37
can be properly selected depending on a size of the
liquid crystal display device.
Further, in order to easily direct inclining of
the liquid crystal molecules above the projected
5 portion of the second electrode from the edge of the
first electrode, it is possible to slope the edge of
the first electrode, to increasing the thickness of the
first electrode, and to etch the insulating layer on
the second electrode to decrease the thickness thereof.
10 Thus, since small pre-tilt angle of 0.1° to 1° is added [
to the liquid crystal molecules, it is possible to •
easily incline the liquid crystal molecules even at a
low driving voltage, and to direct the inclining of the ;
liquid crystal molecules. As a result, it is possible
15 to improve a response property of the liquid crystal
molecules in low gray scale.
Though, in the above description, the motion of the liquid crystal molecules of a negative dielectric
anisotropy in an initial vertical alignment is '
20 explained, it is possible to employ liquid crystal
molecules of a positive dielectric anisotropy in an :
initial horizontal alignment with the same advantage. i
;
i
Therefore, liquid crystal of a horizontal alignment
type can be employed in the present invention. In the
•
25 case of liquid crystal of an initial horizontal •
alignment type, liquid crystal molecules rise '
vertically with the substrate 10b on application of a ]
i
;
i
38
driving voltage to transmit light. When the liquid
crystal of an initial horizontal alignment type is
employed, it is necessary to subject an alignment film
to rubbing-treatment in order to definitely establish
5 the alignment direction of the liquid crystal
molecules.
Though the first and the second electrodes have
combteeth shaped patterns as shown in FIGS. 6 and 7,
they may have slit patterns. Also in the case of the
10 slit pattern, the same advantage can be obtained by
projecting the second electrode from the edge of the
first electrode.
Next, transparent resin, pigment, and etc., which
can be employed in the color filter substrate according '.
15 to the embodiment described above will be exemplified
as follows.
(Transparent resin) ;
r
;
The photosensitive color composition employed in ;
forming a light-shielding layer or coloring layer may
•
20 contains polyfunctional monomer, photosensitive resin
-
or non-photosensitive resin, photo-polymerization
initiator, solvent, etc., in addition to pigment ;
dispersion. Organic resins such as photosensitive •
resin and non-photosensitive resin, which have high ;
25 transparency and can be employed in the embodiments of [
the present invention, are collectively called
transparent resin.
•
39
As for specific examples of the transparent resin,
they include thermoplastic resin, thermosetting resin
and photosensitive resin. Examples of the
thermoplastic resin include, for example, butyral
5 resin, styrene-maleic acid copolymer, chlorinated
polyethylene, chlorinated polypropylene, polyvinyl
chloride, vinyl chloride-vinyl acetate copolymer,
polyvinyl acetate, polyurethane resin, polyester resin,
acrylic resin, alkyd resin, polystyrene, polyamide
10 resin, rubber type resin, cyclized rubber-based resin,
celluloses, polybutadien, polyethylene, polypropylene, |
polyimide, etc. Examples of the thermosetting resin
include, for example, epoxy resin, benzoguanamine
resin, rosin-modified maleic resin, rosin-modified
15 fumaric acid resin, melamine resin, urea resin, phenol
resin, etc. It is also possible to employ, as i
thermosetting resin, compounds obtained through a I
reaction between melamine resin and a compound having I
isocyanate group. |
20 (Alkali-soluble resin) I
A photosensitive resin composition that can be ;
patterned by photolithography is preferably used in ;
-
forming a light-shielding layer, light-scattering
layer, and cell-gap restricting layer in the
25 embodiments described above. As the transparent resins ;
contained in the photosensitive resin composition,
resins having alkali-solubility are preferably used.
40
As the alkali-soluble resin, any resins having
carboxylic group or hydroxyl group may be preferably
employed. As for specific examples of the alkalisoluble
resin, they include epoxyacrylate resin,
5 novolak resin, polyvinyl phenol resin, acrylic resin,
carboxylic group-containing epoxy resin, and carboxylic
group-containing urethane resin. Among these
alkali-soluble resin, epoxyacrylate resin, novolak I
resin, and acrylic resin are preferable. In f
10 particular, epoxyacrylate resin and novolak resin are
preferable.
(Acrylic resin) |
As for specific examples of the acrylic resin, I
they include following materials. |
15 Acrylic resins include polymers obtained from the I
monomers, for example, (metha)acrylic acid; alkyl |
(metha)acrylate such as methyl (metha)acrylate, ethyl f
(metha)acrylate, propyl (metha)acrylate, butyl I
(metha)acrylate, t-butyl (metha)acrylate, benzyl |
20 (metha)acrylate, lauryl (metha)acrylate, etc.; hydroxyl
group-containing (metha)acrylate such as hydoxyethyl
(metha)acrylate, hydoxypropyl (metha)acrylate, etc.;
r
ether group-containing (metha)acrylate such as
ethoxyethyl (metha)acrylate, glycidyl (metha)acrylate, ^
25 etc.; and alicyclic (metha)acrylate such as cyclohexyl •
(metha)acrylate, isobornyl (metha)acrylate,
dicyclopentenyl (metha)acrylate, etc. :
1
41
Incidentally, these monomers can be used singly or
in combination of two or more kinds. Further, there
may be used copolymers of these monomers and other
kinds of compounds such as styrene, cyclohexyl
5 maleimide, phenyl maleimide, etc., which can be
co-polymerized with these monomers. i
It is also possible to obtain photosensitive
• resins through the reaction of a copolymer of
carboxylic acid having an ethylenic unsaturated group
10 such as (metha)acrylic acid and a compound having epoxy
group and unsaturated double bond such as glycidyl
methacrylate, or through the addition of a carboxylic acid-containing compound such as (metha)acrylic acid to
r
i
a polymer of epoxy group-containing (metha)acrylate
15 such as glycidyl methacrylate or to a copolymer of epoxy group-containing (metha)acrylate with other kinds [
of (metha)acrylate.
It is also possible to obtain a photosensitive
resin through the reaction between polymer having
20 hydroxyl group and obtained by using a monomer such as
hydroxyethyl methacrylate and a compound having an r
isocyanate group and an ethylenic unsaturated group ;
such as methacryloyloxyethyl isocyanate. ;
i
Further, a resin having carboxylic group can be ; •
25 obtained through a reaction between a copolymer of
hydroxyethyl methacrylate having a plurality of
hydroxyl groups and a polybasic acid anhydride, thereby •
•
42
introducing carboxylic group into the copolymer. The
manufacturing method thereof may not be limited to the
above-described method.
As for specific examples of the acid anhydride to
5 be employed in the aforementioned reaction, they
include, for example, malonic anhydride, succinic
anhydride, maleic anhydride, itaconic anhydride,
phthalic anhydride, tetrahydrophthalic anhydride,
hexahydrophthalic anhydride, methyltetrahydrophthalic
10 anhydride, trimellitic anhydride, etc.
The acid value of solid content of above-described
acrylic resin may preferably be confined to
•
20-180 mgKOH/g. If this acid value is less than
20 mgKOH/g, the developing rate of the photosensitive
15 resin composition may become to slow, thereby taking a
lot of time for executing the development thereof, thus
I
leading to the decrease of productivity. On the other {
•
i
hand, if the acid value of solid content is larger than •
180 mgKOH/g, the developing rate of the photosensitive l
I
20 resin composition may become to fast on the contrary, !
[
thereby inviting the generation of problems such as
peeling of pattern after the development thereof or the t
chip-off of pattern. r
r
Further, in the case where the aforementioned
25 acrylic resin is photosensitive, the double-bond
equivalent of the acrylic resin may preferably be not [
less than 100, more preferably 100-2000, most
43
preferably 100-1000. If the double-bond equivalent
thereof is higher than 2000, it may become difficult to
secure sufficient photo-curing properties.
(Photopolymerizable monomer)
5 As for specific examples of the photopolymerizable
monomer, they include various kinds of acrylic esters
and methacrylic esters such as
2-hydroxyethyl(metha)acrylate,
2-hydroxypropyl(metha)acrylate,
10 cyclohexyl(metha)acrylate, polyethyleneglycol
di(metha)acrylate, pentaerythritol tri(metha)acrylate,
trimethylolpropane tri(metha)acrylate,
dipentaerythritol hexa(metha)acrylate, tricyclodecanyl
(metha)acrylate, melamine (metha)acrylate, i
15 epoxy(metha)acrylate; (metha)acrylic acid; styrene;
vinyl acetate; (metha)acryl amide; N-hydroxymethyl i
(metha)acryl amide; acrylonitrile, etc.
i
Further, it is preferable to employ polyfunctional
urethane acrylate having (metha)acryloyl group which =
[
20 can be obtained through the reaction between ;
(metha)acrylate having hydroxyl group and ;
polyfunctional isocyanate. Incidentally, the ;•
combination between the (metha)acrylate having hydroxyl
group and polyfunctional isocyanate may be optionally '•
25 selected and hence there is not any particular
limitation. Further, only one kind of polyfunctional
urethane acrylate may be used singly or polyfunctional
-
44
urethane acrylate may be used in a combination of two
or more kinds thereof.
(Photo-polymerization initiators)
As for specific examples of the photo-
5 polymerization initiator, they include an acetophenonebased
compound such as 4-phenoxy dichloroacetophenone,
4-t-butyl-dichloroacetophenone, diethoxyacetophenone,
1-{4-isopropylphenyl)-2-hydroxy-2-methylpropan-l-one,
1-hydroxycyclohexylphenyl ketone, 2-benzyl-2-
10 dimethylamino-1-(4-morpholinophenyl)-butan-1-one; a
I
benzoin-based compound such as benzoin, benzoin methyl
ether, benzoin ethyl ether, benzoin isopropyl ether,
benzyldimethyl ketal, etc.; a benzophenone-based
compound such as benzophenone, benzoylbenzoic acid,
15 benzoylmethyl benzoate, 4-phenyl benzophenone,
hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-
4'-methyldiphenyl sulfide, etc.; a thioxanthone-based i
I
compound such as thioxanthone, 2-chlorothioxanthone, 2- i
I
methylthioxanthone, isopropylthioxanthone, 2,4-
20 diisopropylthioxanthone, etc.; a triazine-based
compound such as 2,4,6-trichloro-s-triazine, 2-phenyl-
4,6-bis(trichloromethyl)-s-triazine, 2-(p- '.
methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-
(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-
25 piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4- •
bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphtho-1-
yl)-4,6-bis(trichloromethyl)-s-triazine,
!
r ;
45
2-(4-methoxynaphtho-l-yl)-4,6-bis(trichloromethyl)-striazine,
2,4-trichloromethyl-(piperonyl)-6-triazine,
2,4-trichloromethyl(4'-methoxystyryl)-6-triazine, etc.;
an oxime ester-based compound such as 1,2-octanedione,
5 1-[4-(phenylthio)-2-(0-benzoyloxime)], 0-(acetyl)-N-(1-
phenyl-2-oxo-2-(4'-methoxynaphthyl)ethylidene) hydroxyl
amine, etc.; a phosphine-based compound such as
bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide,
2,4,6-trimethylbenzoyl diphenylphosphine oxide, etc.; a
10 quinine-based compound such as 9,10-phenanthrene
quinine, camphor quinine, ethyl anthraquinone, etc.; a
borate-based compound; a carbazol-based compound; an
imidazole-based compound, a titanocene-based compound,
etc. Oxime derivatives are suitable to increase
15 sensitivity. These photo-polymerization initiators can
be employed singly or in combination of two or more |
;
kinds thereof. ;
(Photo-sensitizer) ;
It is preferable to use these photo-polymerization
20 initiators in combination with a photo-sensitizer.
r
Specific examples of the photo-sensitizer include a- acyloxy ester, acylphosphine oxide, methylphenyl J
glyoxylate, benzyl-9,10-phenanthrene quinone, camphor l
quinine, ethylanthraquinone, 4,4'-diethyl :
25 isophthalophenone, 3,3',4,4'-tetra(t-butyl
peroxycarbonyl)benzophenone, 4,4'-diethyl
aminobenzophenone, etc. •
These sensitizers can be employed at a ratio of
0.1 to 60 parts by mass based on 100 parts by mass of
the photo-polymerization initiator.
(Ethylenic unsaturated compound)
5 It is preferable to use these photo-polymerization
initiators in combination with an ethylenic unsaturated
compound. "Ethylenic unsaturated compound" means a
compound having at least one ethylenic unsaturated bond
in one molecule. In particular, it is preferable to
10 use a compound having two ethylenic unsaturated bonds
in one molecule in consideration of polymerizability,
crosslinkability, and accompanying expandability of
difference in solubility by developing solution between
the exposed portion and unexposed portion. Further, it
15 is preferable to use (metha)acrylate having an
unsaturated bond originating from (metha)acryloyloxy ;
i
l
group. ;
Compound having one ethylenic unsaturated bond in the molecule includes for example, unsaturated I
20 carboxylic acid such as (metha)acrylic acid, crotonic •
acid, isocrotonic acid, maleic acid, itaconic acid, ;.
citraconic acid, and alkyl ester thereof; =
(metha)acrylonitrile; (metha)acrylamide; stylene, etc. |
Compound having at least two ethylenic unsaturated 1-
25 bonds in the molecule includes for example, ester of I
unsaturated carboxylic acid and polyhydroxy compound, I
(metha)acryloyloxy-containing phosphate, urethane I
I
(metha)acrylate of (metha)acrylate compound and
polyisocyanate compound, and epoxy(metha)acrylate of
(metha)acrylic acid or hydroxy(metha)acrylate and
polyepoxy compound.
5 Where a retardation layer is formed in a part of
the color filter structure of the color filter
substrate according to the present embodiment, the
retardation layer is formed of a composition containing
polymerizable liquid crystal compound, to which the
10 above-described photo-polymerization initiator,
sensitizer, photo-sensitizer and ethylenic unsaturated
compound are added. Specific measures to give a
function for altering retardation to the color filter
include a coating method using polymer liquid crystal
15 or cross-linkable polymer liquid crystal solution, a
method of adding a birefringence-controlling agent to
alkali-soluble transparent resin, and a method using
:
polymerizable liquid crystal compound. As the
polymerizable liquid crystal compound, discotheque 20 polymerizable liquid crystal compound having a discshaped
molecular structure or rod-shaped polymerizable
liquid crystal compound can be used. It is possible to I
combine theses methods and materials described above. |
(Polyfunctional thiol) I
25 The photosensitive resin composition may contain I
polyfunctional thiol which is capable of acting as a I
chain-transfer agent. The polyfunctional thiol is |
useful as long as it has two or more thiol groups.
Specific examples of the polyfunctional thiol include
hexane dithiol, decane dithiol, 1,4-butanediol
bisthiopropionate, 1,4-butanediol bisthioglycolate,
5 ethyleneglycol bisthioglycolate, ethyleneglycol
bisthiopropionate, trimethylolpropane
tristhioglycolate, trimethylolpropane
tristhiopropionate, trimethylolpropane tris{3-
mercaptobutylate), pentaerythritol
10 tetrakisthioglycolate, pentaerythritol
tetrakisthiopropionate, trimercaptopropionate tris(2-
hydroxyethyl)isocyanulate, 1,4-dimethylmercaptobenzene,
2,4,6-trimercapto-s-triazine, 2-(N,N-dibutylamino)-4,6-
dimercapto-s-triazine, etc.
15 These polyfunctional thiols can be employed singly
or in combination of two or more kinds. The content of
these polyfunctional thiols may preferably be confined
to 0.2-150 parts by mass, more preferably 0.2-100 parts j
by mass based on 100 parts by mass of the pigment in
20 the color composition. I
(Storage stabilizing agent) i
The photosensitive resin composition may further I
contain a storage-stabilizing agent for stabilizing the I
variation with time in viscosity of the composition. I
25 Specific examples of the storage stabilizing agent l
include, for example, quaternary ammonium chlorides I
such as benzyltrimethyl chloride, diethylhydroxy amine, I
49
etc.; organic acids such as lactic acid, oxalic acid,
etc. and methyl ethers thereof; t-butyl pyrocatechol; I
organic phosphine such as triethyl phosphine, triphenyl
phosphine, etc.; phosphite; etc. The storage
5 stabilizing agent can be employed at a ratio of 0.1-10
parts by mass based on 100 parts by mass of the
pigments in a coloring composition.
(Adherence improver)
Further, the photosensitive resin composition may
10 contain an adherence improver such as a silane coupling
agent for the purpose of enhancing the adhesion thereof
to a substrate. As for specific examples of the silane
coupling agent, they include vinyl silanes such as
vinyl tris(p-methoxyethoxy) silane, vinylethoxy silane,
15 vinyltrimethoxy silane, etc.; (metha)acrylsilanes such
as Y~iTiethacryloxypropyltrimethoxy silane, etc.; epoxy
silanes such as (3-(3, 4-epoxycyclohexyl) ethyltrimethoxy
silane, (3-(3, 4-epoxycyclohexyl) methyltrimethoxy silane, (3-(3, 4-epoxycyclohexyl) ethyltriethoxy silane, (3-(3, 4- i
20 epoxycyclohexyl)methyltriethoxy silane, Y~ •
glycidoxypropyl trimethoxy silane, ygly^idoxypropyl
triethoxy silane, etc.; amino silanes such as N- I
(3 (aminoethyl) Y~3niiriop^opyl trimethoxy silane, N- ;
(3 (aminoethyl) Y'^r^iii^op^opyl triethoxy silane, N-
25 (3 (aminoethyl) y^^niij^opropyl methyldiethoxy silane, Y~
aminopropyl triethoxy silane, y^n^inopropyl trimethoxy
•
silane, N-phenyl-y-aminopropyl trimethoxy silane,
I
:
50
N-phenyl-Y-arainopropyl triethoxy silane, etc.; and
i
thiosilanes such as Y~i^srcaptopropyl trimethoxy silane,
Y-mercaptopropyl triethoxy silane, etc. These silane
coupling agents can be used at a ratio of 0.01-10 parts
5 by mass based on 100 parts by mass of the pigments in a
coloring composition.
(Solvents)
The photosensitive resin composition may further
contain a solvent such as water, organic solvents, etc.
10 so that the surface of a substrate is uniformly coated
therewith. Further, in the case where the
photosensitive resin composition of the present
invention is to be used for constituting the color
layer of color filter, the solvent acts to enable
15 pigments to be uniformly dispersed in the color layer.
Specific examples of the solvent include, for example,
cyclohexanone, ethyl Cellosolve acetate, butyl
Cellosolve acetate, l-methoxy-2-propyl acetate,
diethyleneglycol dimethyl ether, ethyl benzene,
f
20 ethyleneglycol diethyl ether, xylene, ethyl Cellosolve, methyl-n amyl ketone, propyleneglycol monomethyl ether,
toluene, methylethyl ketone, ethyl acetate, methanol, I
ethanol, isopropyl alcohol, butanol, isobutyl ketone, J

petroleum solvent, etc. These solvents may be employed ;
25 singly or in combination of two or more kinds. The
mixing ratio of these solvents may be confined to the range of 4000 parts by mass, preferably 1000 to 2500 parts by mass based on 100 parts by mass of the pigments in the color composition.

C L A I M S
1. A color filter substrate for a liquid crystal
display device performing an ordinary display for a
gray scale display and a dynamic display for a bright
5 display, which comprises:
a transparent substrate;
a transparent conductive film formed above the
transparent substrate;
a black matrix formed above the transparent
10 conductive film and having a pixel region which is an
opening partitioned into a polygonal pixel shape having
two parallel sides;
a first transparent resin layer formed so as to
cover portions corresponding to the two parallel sides
15 of the black matrix;
a color layer formed for the pixel region; and
a second transparent resin layer formed above the
color layer and having a linear depression passing a
center of the pixel region.
20 2. The color filter substrate according to
claim 1, characterized in that the color layer is
partitioned into a ordinary display region formed
directly above the transparent conductive film at the
center of the pixel region, and a dynamic display
25 region formed above the first transparent resin layer
formed so as to cover portions corresponding to the two
parallel sides of the black matrix.
74
3. The color filter substrate according to
claim 2, characterized in that a thickness A of the
first transparent resin layer between a surface of the
transparent conductive film formed above the
5 transparent substrate and a bottom of the linear
depression, a total thickness B of the color layer and
the second transparent resin layer in the ordinal
display region, and a total thickness C of the first
transparent resin layer, the color layer and the second
10 transparent resin layer in the dynamic display region
satisfy a relationship of A>B>C.
4. The color filter substrate according to
claim 3, characterized in that a total thickness from
the black matrix to the second transparent resin layer
15 above the black matrix is larger than the thickness C
in the dynamic display region.
5. A liquid crystal display device characterized
by comprising:
the color filter substrate recited in any one of
20 claims 1 to 4.
6. The liquid crystal display device according to
claim 5,
characterized in that the liquid crystal display
device comprises
25 the color filter;
an array substrate arranged to oppose to the color
filter substrate and provided with elements for driving
75
liquid crystal, said elements being arranged in a
matrix form; and
a liquid crystal layer interposed between the
color filter substrate and the array substrate, and
5 wherein the array substrate comprises a first
electrode and a second electrode to which different
voltages are applied in order to drive liquid crystal.
7. The liquid crystal display device according to
claim 6, characterized in that liquid crystal molecules
10 in two regions formed by symmetrically dividing the
pixel region with a straight line act to tilt to
opposite directions to each other when an operating
voltage is applied between the first electrode and the
second and third electrodes, the third electrode being
15 the transparent.
8. The liquid crystal display device according to
claim 6, characterized in that the pixel region is
point-symmetrically divided into four operating regions
with regard to a center of the pixel region in a plane
20 view when the liquid crystal molecules act depending on
a driving voltage applied thereto.
9. The liquid crystal display device according to
claim 6, characterized in that the first electrode has
a combteeth shaped pattern and connected to active
25 elements driving liquid crystal, the second electrode
has a combteeth shaped pattern and arranged beneath the
first electrode with an insulating layer interposed
76
therebetween, and the second electrode protrudes from
an edge of the first electrode toward a side of a pixel
in a plane view.
10. The liquid crystal display device according
5 to claim 6, characterized in that the first and second
electrodes are made of conductive metal oxide which is
transparent in a visible light range.
11. A liquid crystal display device which
comprises:
10 a color filter substrate including a transparent
substrate, a transparent conductive film formed above
the transparent substrate, a black matrix having pixel
regions which are openings partitioned into polygonal
pixel shapes respectively having two parallel sides, a
15 first transparent resin layer, and color pixels formed
of a plurality of color layers formed above the pixel
regions;
an array substrate arranged to oppose to the color
filter substrate and provided with elements for driving
20 liquid crystal, said elements being arranged in a
matrix form; and
a liquid crystal layer interposed between the
color filter substrate and the array substrate,
characterized in that the first transparent resin
25 layer and color layer overlap along the black matrix in
the pixel region, the array substrate includes a first
electrode and a second electrode, which are of
77
combteeth shape, made of conductive metal oxide, and
are transparent in visible light range, the second
electrode are arranged beneath the first electrode with
an insulating layer interposed therebetween, and the
5 second electrode protrudes from an edge of the first
electrode toward the first transparent resin layer in a
plane view.
12. The liquid crystal display device according
to claim 11, characterized in that the first electrode
10 is not arranged in that a position above the array
substrate which the first transparent resin layer is
arranged in the plane view.
13. The liquid crystal display device according
to claim 12, characterized in that the liquid crystal
has a negative dielectric anisotropy.