Specification
5
1
D E S C R I P T I 0 N
Title of Invention
COLOR FILTER SUBSTRATE FOR LIQUID CRYSTAL
DISPLAY DEVICE AND LIQUID CRYSTAL DISPLAY DEVICE
Technical Field
The present invention relates to a color filter
substrate for a liquid crystal display device and a
10 liquid crystal display device including the color
filter substrate. In particular, the present invention
relates to a color filter substrate optimized for
driving liquid crystals by an oblique electric field
generated by applying_a voltage between a transparent
15 conducting film disposed on a color filter substrate
and first and second electrodes provided on an array
substrate side and a liquid crystal display device
including the color filter substrate.
Background Art
20 In recent years, still higher quality, lower
prices, and lower power consumption of slim display
devices such as liquid crystal displays are demanded.
Regarding color filters for liquid crystal display
devices, requests fitting to higher quality display
25 such as adequate color purity, high contrast, and
flatness are submitted.
The liquid crystal alignment method such as VA
(Vertically Alignment), HAN (Hybrid-aligned Nematic),
TN (Twisted Nematic), OCB (Optically Compensated Bend),
2
and CPA (Continuous Pinwheel Alignment) and the liquid
crystal drive method have been proposed and displays
with a wide angle of visibility/fast response have
thereby been commercialized.
5 In a liquid crystal display device of the VA
system that can more easily be adapted to a wide angle
of visibility and fast response by the liquid crystals
aligned in parallel with the substrate surface formed
of glass or the like or the HAN system that is
10 effective for a wide angle of visibility, still higher
levels of requests are made regarding flatness of color
filters (uniformity of thickness and reduction of
irregularities on the color filter surface) and
electric properties such as the dielectric constant.
15 For such a high-quality liquid crystal display, the
main subject is a technology to slim the thickness of
liquid crystal cells (thickness of the liquid crystal
layer) to reduce coloring in oblique direction visual
recognition. In the VA system, various improved modes
20 such as MVA (Multi-Domain Vertically Alignment), PVA
(Patterned Vertically Alignment), VAECB (Vertically
Alignment Electrically Controlled Birefringence), VAHAN
(Vertical Alignment Hybrid-aligned Nematic), and VATN
(Vertically Alignment Twisted Nematic) are under
25 development. In a liquid crystal display device of a
longitudinal electric field system like the VA system
in which a drive voltage is applied in the thickness
3
direction of liquid crystal, the main subject includes
a faster liquid crystal response, technology of a wider
angle of visibility, and higher transmittance. The MVA
technology is a technology to secure a wide angle of
5 visibility by providing a plurality of liquid crystal
alignment regulating structures called ribs or slits to
form liquid crystal domains between these ribs and also
to form domains in a plurality of alignment directions
to solve the problem of unstable vertically aligned
10 liquid crystals when a liquid crystal driving voltage
is applied (the direction of inclination in which
liquid crystals initially aligned vertically with
respect to the substrate surface is less likely to be
determined when a voltage is applied). Japanese Patent
15 No. 2947350 discloses a technology to form a liquid
crystal domain by using first and second or alignment
regulating structures (ribs).
If the liquid crystal has negative dielectric
constant anisotropy, more specifically, a liquid
20 crystal positioned between two ribs made of resin
formed on a color filter or the like attempts, for
example, to incline in a direction perpendicular to the
ribs to be aligned in parallel with the substrate
surface in a plane view when a drive voltage is
25 applied. However, the inclination direction in which
the liquid crystals in the center between two ribs is
not uniquely determined regardless of the application
4
of voltage and may take a spray alignment or bend
alignment. Such an alignment disorder of liquid
crystal leads to a rough liquid crystal display or
display unevenness. Also in the MVA system, it is
5 difficult to finely control the amount of inclining
liquid crystals by a drive voltage including the above
problem and also the halftone display has weaknesses.
To solve such problems, Japanese Patent
No. 2859093 and Japanese Patent No. 4459338 disclose a
10 technology that uses a transparent conducting film (a
transparent electrode, display electrode, or third
electrode) on the side of a filter substrate and first
and second electrodes on the side of an array substrate
to control a vertically aligned liquid crystal by an
15 oblique electric field generated by a voltage being
applied to these electrodes. Japanese Patent
No. 2859093 uses a liquid crystal of negative
dielectric constant anisotropy and Japanese Patent
No. 4459338 describes a liquid crystal of positive
20 dielectric constant anisotropy.
As shown in Japanese Patent No. 2859093 and
Japanese Patent No. 4459338, the method of using the
first, second, and third electrodes to control the
liquid crystal alignment by an oblique electric field
25 is very effective. The inclination direction of the
liquid crystals can be set by the oblique electric
field. Moreover, the oblique electric field makes the
5
control of the amount of the liquid crystal inclination
easier, which has an important effect on the halftone
display.
However, even such a technology has insufficient
5 measures against disclination of liquid crystal. The
disclination is a problem arising in a pixel (the pixel
is the minimum unit of liquid crystal display and is
synonymous with the pixel described in the present
invention) in which regions of different optical
10 transmittances arise due to an unintended alignment
disorder of liquid crystal or non-alignment.
According to Japanese Patent No. 2859093, an
alignment control window without transparent conducting
film is provided in the pixel center of the counter
15 electrode (third electrode) to fix the disclination in
the pixel center. However, no improvement proposal of
the disclination in the pixel periphery is disclosed.
Though the disclination in the pixel center can be
fixed, no proposal for minimizing the disclination is
20 shown. Further, no technology to improve
responsiveness of liquid crystal is described.
Japanese Patent No. 4459338 is preferable because
a dielectric layer is stacked on the transparent
conducting film (transparent electrode) and the effect
25 of the oblique electric field is enhanced for the
stacked dielectric layer. However, as shown in FIG. 7
of Japanese Patent No. 2859093, a vertically aligned
6
liquid crystal remains in the pixel center and pixel
periphery, causing a problem of lower transmittance or
aperture ratio. If a liquid crystal of positive
dielectric constant anisotropy is used (Japanese Patent
5 No. 2859093 does not disclose any
description/embodiment of a liquid crystal of negative
dielectric constant anisotropy), it is difficult to
improve transmittance due to the disclination in the
pixel center. Thus, the technology is hard to adopt
10 for a transflective liquid crystal display device.
The basic configuration of a liquid crystal
display device of the VA system or TN system is
normally a configuration in which a liquid crystal is
sandwiched between a color filter substrate including a
15 common electrode and an array substrate including a
plurality of pixel electrodes (for example, transparent
electrodes electrically connected to a TFT element and
formed in a comb-like pattern shape) driving the liquid
crystal. In this configuration, the liquid crystal is
20 driven by applying a drive voltage between the common
electrode on the color filter and the pixel electrodes
formed on the side of the array substrate. A thin film
of conductive metal-oxides such as ITO (Indium Tin
Oxide), IZO (Indium Zinc Oxide), and IGZO (Indium
25 Gallium Zinc Oxide) is used as the pixel electrode and
the transparent conducting film as the common electrode
on the color filter surface.
7
FIG. 2 of Jpn. Pat. Appln. Publication No. 5-26161
discloses a technology to disclose the configuration of
a color filter in which a blue pixel, green pixel, and
red pixel are formed on a transparent conducting film.
5 Also, a technology, though using a plurality of stripe
electrodes and a liquid crystal of positive dielectric
constant anisotropy, that forms a color filter on a
transparent electrode (transparent conducting film) is
described in Japanese Patent No. 2859093 (for example,
10 FIGS. 7 and 9 of the patent literature).
A technology to improve luminance or lightness or
extend the chromaticity range to obtain a higher
quality and more dynamic display is disclosed by Jpn.
Pat. Appln. KOKAI Publication No. 2010-9064, Japanese
15 Patent No. 4460849,·and Jpn. Pat. Appln. KOKAI
Publication No. 2005-352451. Also, a technology of 4-
color display by adding a yellow pixel or white pixel,
in addition to the blue pixel, green pixel, and red
pixel is known.
20 However, it is necessary for these technologies to
25
provide another pixel such as a yellow or white pixel
and an active element (TFT) to drive the pixel and
still one color layer to form a color filter are
needed, leading to higher costs due to increased
processes. In addition, it is necessary to inhibit or
turn off the display of white or yellow pixels in a
gradation display range in which the display of yellow
8
or white that is bright in intensity is not needed,
causing a problem of being unlikely to lead to an
effective increase in luminance. Further, in the
reflective type display, a problem that the display
5 takes on a yellow tinge is posed (to suppress the
yellow tinge, for example, a special blue filter
disclosed by Jpn. Pat. Appln. KOKAI Publication
No. 2005-352451 is needed).
Summary of Invention
10 Technical Problem
An object of the present invention is to provide a
color filter substrate for a liquid crystal display
device achieving improvements of both of the gradation
display and responsiveness at the same time and a
15 liquid crystal display device including the color
filter substrate.
Solution to Problem
In order to solve the above problem, according to
a first aspect of the present invention, a color filter
20 substrate for a liquid crystal display device,
comprising: a transparent substrate; a black matrix
formed on the transparent substrate and having an
opening for division into a plurality of pixels; a
transparent conducting film; and a color layer formed
25 on the pixel, wherein a linear projection is formed in
a center of the pixel and a recess is formed above the
black matrix is provided.
9
According to a second aspect of the present
invention, a liquid crystal display device including
the color filter substrate for a liquid crystal display
device according to the above first aspect of the
5 present invention is provided.
According to a third aspect of the present
invention, a liquid crystal display device that
includes a black matrix having a plurality of pixels, a
transparent conducting film, and a linear resin layer
10 on a transparent substrate and includes a color filter
substrate including color pixels formed of a plurality
of color layers respectively on the pixels, an array
substrate on which drive elements for liquid crystals
are disposed in a matrix arrangement, and a liquid
15 crystal layer interposed between the color filter
substrate and the array substrate, wherein the linear
resin layer is disposed in a center of the pixel on the
transparent conducting film in a plane view, a linear
projection projecting to the side of the liquid crystal
20 is formed by laminating the linear resin layer and the
color layer, the array substrate includes a comb-like
first electrode and a comb-like second electrode, each
of which formed of a transparent conductive oxide in a
visible region, the second electrode is disposed below
25 the first electrode via an insulating layer, and the
second electrode protrudes from an end of the first
electrode in a direction toward the linear resin layer
10
or in a direction toward the center of the pixel in the
plane view.
Brief Description of Drawings
FIG. 1 is a schematic sectional view of a liquid
5 crystal display device according to an embodiment of
the present invention.
FIG. 2 is a sectional view showing an initial
alignment state of a vertically aligned liquid crystal
on a green pixel of the liquid crystal display device
10 shown in FIG. 1.
FIG. 3 is a diagram illustrating a motion of
liquid crystals beginning to incline immediately after
a drive voltage being applied in the liquid crystal
display device shown in FIG. 1.
15 FIG. 4 is a diagram showing an alignment state of
20
liquid crystal molecules during a white display (a
green pixel in the figure) after the drive voltage
being applied in the liquid crystal display device
shown in FIG. 1.
FIG. 5 is a diagram showing the alignment state of
liquid crystal molecules during high-luminance display
by a still higher voltage being applied to the liquid
crystal display device shown in FIG. 1.
FIG. 6 is a diagram showing liquid crystal
25 molecules vertically aligned near a first electrode
when a comb-like pattern is adopted for the first and
second electrode in the vertically aligned liquid
11
crystal display device shown in FIG. 1.
FIG. 7 is a diagram showing an operation of liquid
crystal molecules immediately after the voltage to
drive the liquid crystal of the vertically aligned
5 liquid crystal display device shown in FIG. 6 being
applied and also electric lines of force.
10
FIG. 8 is a diagram showing a comb-like pattern
whose alignment is changed by 90° in units of 1/4
pixel.
FIG. 9 is a partial sectional view showing a color
filter substrate according to Example 1.
FIG. 10 is a partial sectional view showing a
color filter substrate according to Example 2.
FIG. 11 is a partial sectional view showing a
15 liquid crystal display device according to Example 4.
FIG. 12 is a partial sectional view showing a
liquid crystal display device according to Example 5.
FIG. 13 is a partial sectional view showing a
liquid crystal display device according to Example 6.
20 FIG. 14 is a sectional view showing a liquid
crystal display device according to Example 7.
FIG. 15 is a diagram showing a pattern shape in a
plane view of a first electrode applicable to an
embodiment of the present invention.
25 FIG. 16 is a diagram showing a pattern shape in
the plane view of the first electrode applicable to an
embodiment of the present invention.
12
FIG. 17 is a diagram showing a pattern shape in
the plane view of the first electrode when a pixel
opening is parallelogrammic.
FIG. 18 is a diagram showing a pattern shape in
5 the plane view of the first electrode when the pixel
opening is parallelogrammic.
Description of Embodiments
The embodiments of the present invention will be
described later.
10 A color filter substrate for a liquid crystal
display device according to the first aspect of the
present invention includes a transparent substrate, a
black matrix formed on the transparent substrate and
having an opening for division into a plurality of
15 pixels, a transparent conducting film, and a color
layer formed on the pixel. A linear projection is
formed in a center of the pixel and a recess is formed
above the black matrix.
In a color filter substrate, a configuration in
20 which a linear resin layer is formed in the center of
the pixel, the linear projection is a laminated
constitution of the linear resin layer and the color
layer, and the recess is formed by a step between the
adjacent color layers can be adopted.
25 In this case, the transparent conducting film may
be formed on the black matrix or the black matrix may
be formed on the transparent conducting film. The
13
laminated constitution of the linear resin layer and
the color layer may be laminated in an order of the
linear resin layer and the color layer.
The laminated constitution of the linear resin
5 layer and the color layer is laminated in the order of
the color layer and the linear resin layer and the
thickness of the color layer of the laminated
constitution with the linear resin layer can be made
thinner than the thickness on the pixel excluding the
10 laminated constitution.
In such a case, a protective layer can further be
laminated to cover the black matrix and the color
layer.
A configuration in which a portion of the color
15 layer corresponding to the linear projection has a thin
thickness, a first resin layer is formed on the color
layer excluding a portion above the black matrix, a
second resin layer is formed in a portion of the first
resin layer corresponding to the thin portion of the
20 color layer, the linear projection is formed of the
second resin layer, and the recess is formed of a
portion above the black matrix where the first resin
layer is not present can be adopted.
In this case, the transparent conducting film can
25 be formed on the color layer.
In the above color filter substrate for a liquid
crystal display device, the color layer can include
14
three color layers formed of a red pixel, a green
pixel, and a blue pixel formed on the respective pixel.
A liquid crystal display device according to the
second aspect of the present invention includes the
5 above color filter substrate for a liquid crystal
display device according to the first aspect of the
present invention.
Such a liquid crystal display device is a liquid
crystal display device includes the color filter
10 substrate for a liquid crystal display device, an array
substrate on which driving elements for liquid crystals
are disposed in a matrix arrangement, and a liquid
crystal layer interposed between the color filter
substrate and the array substrate, and the array
15 substrate can be assumed to include first and second
electrodes to which different potentials are applied to
drive the liquid crystals.
When a drive voltage is applied between the first
electrode, and the second electrode and third
20 electrode, molecules of the liquid crystal in a pixel
region of the liquid crystal display device can be
caused to perform a inclining operation in opposite
directions symmetrically with respect to a straight
line dividing the pixel region into two parts.
25 The operation of the liquid crystal in the pixel
when the voltage to drive the liquid crystal is applied
can be made to be divided into four domains
15
symmetrically with respect to a point in a plane view.
A configuration in which the first electrode has a
comb-like pattern connected to an active element
driving the liquid crystal and the second electrode has
5 a comb-like pattern disposed below the first electrode
via an insulating layer and also the second electrode
protrudes from an end of the first electrode in a
direction toward the linear resin layer or in a
direction toward the pixel center in a plane view can
10 be adopted.
The first electrode and the second electrode can
be formed of a conductive metal-oxides that is
transparent in the visible range.
A liquid crystal display device according to the
15 third aspect of the present invention includes a black
matrix having a plurality of pixels, a transparent
conducting film, and a linear resin layer on a
transparent substrate and includes a color filter
substrate including color pixels formed of a plurality
20 of color layers on the pixels, an array substrate on
which drive elements for liquid crystals are disposed
in a matrix arrangement, and a liquid crystal layer
interposed between the color filter substrate and the
array substrate. The linear resin layer is disposed in
25 the pixel center on the transparent conducting film in
a plane view, a linear projection projecting to the
liquid crystal side is formed by laminating the linear
16
resin layer and the color layer, the array substrate
includes a comb-like first electrode and a comb-like
second electrode, each of which formed of a transparent
conductive oxide in the visible region, the second
5 electrode is disposed below the first electrode via an
insulating layer, and the second electrode protrudes
from an end of the first electrode in a direction
toward the linear resin layer or in a direction toward
the pixel center in a plane view.
10 Such a liquid crystal display device can be
configured in such a way that the first electrode is
not disposed in a position opposite to the linear resin
layer on the array substrate in a plane view.
Also in the above liquid crystal display device, a
15 liquid crystal having negative dielectric constant
anisotropy can be used as the liquid crystal.
According to the above aspects of the present
invention, a color filter substrate for a liquid
crystal display device achieving improvements of both
20 of the gradation display and responsiveness at the same
time and a liquid crystal display device including the
color filter substrate are provided. Particularly,
according to the aspects of the present invention, a
color filter substrate for a liquid crystal display
25 device capable of making a display full of liveliness
by emphasizing particularly brightness without
disturbing the color balance and increasing the number
17
of TFT elements and a liquid crystal display device
including the color filter substrate are provided.
According to the aspects of the present invention, when
applied to a reflective type liquid crystal display, a
5 reflective type display with excellent color balance
can be made without yellow tinge.
Further, according to the aspects of the present
invention, a dynamic and bright display can be obtained
without increasing pixels such as white pixels or
10 yellow pixels and thus, a liquid crystal display device
capable of making a brighter display than before is
provided without dead pixels like white pixels in a
normal gradation display and further without
disclination that lowers the transmittance of liquid
15 crystal.
Various embodiments of the present invention will
be described later with reference to the drawings.
An embodiment of the present invention is mainly
intended as a normally black-display liquid crystal
20 display device using a liquid crystal whose initial
alignment is vertically aligned or horizontally aligned
and assumes a liquid crystal display device configured
by opposing a color filter substrate and an array
substrate on which liquid crystal driving elements such
25 as TFT are formed while a liquid crystal layer being
sandwiched therebetween. Therefore, the technology
according to the present invention can be applied to a
18
liquid crystal display device using a liquid crystal
whose initial alignment is horizontal and which rises
in the vertically direction when a voltage is applied.
In addition, in the present embodiment, an oblique
5 electric field generated in an electrode configuration
in which the transparent conducting film as the third
electrode is disposed on the color filter substrate
with respect to the first electrode and the second
electrode whose potential is different from that of the
10 first electrode as pixel electrodes provided on the
array substrate side is utilized.
The inventors found that a recess formed by a step
created by overlapping adjacent color layers and a
projection provided in the center that makes a pixel
15 symmetric with respect to a line can be used for
controlling the alignment of liquid crystal. The
present invention proposes a new technology that adds
the above finding and the configuration of a third
electrode (transparent conducting film) .
20 In the present embodiment, the projection is
configured by a superimposed portion of a linear resin
layer as a transparent resin and a thin color layer and
light passing through the linear resin layer and the
thin color layer of the projection is used to increase
25 transmittance in the liquid crystal display. The main
action of the projection is to enable a dynamic display
in which light transmission is increased when a high
19
drive voltage is applied to the liquid crystal by being
utilized as a thick dielectric material. The
projection has a role adding a voltage gradient to the
liquid crystal layer. The projection as a laminated
5 constitution of the linear resin layer and the thin
color layer becomes a dynamic display area described
later. A color layer of an approximately uniform
thickness (about twice the thickness of the thin color
layer) is disposed in a normal transmissive display
10 area without projection formation in the pixel opening.
In contrast, the recess has, as will be described
next, a somewhat different role from the projection in
that a liquid crystal aligned obliquely in a shoulder
portion of the recess is utilized for the liquid
15 crystal to respond. It is better for the transparent
conducting film as the third electrode positioned in
the recess to have a thickness of the color layers
laminated at the site and other organic resins that is
as thin as possible so that the drive voltage can be
20 transmitted to the liquid crystal layer more easily.
The third electrode of the recess is desirably arranged
in a position close to the liquid crystal layer.
The recess is provided to use the tilt of the
liquid crystals in the shoulder portion for the
25 inclination of the liquid crystals. The operation of
liquid crystal will be described in detail in
subsequent embodiments. The preferable depth of the
20
recess is in the range of 0.5 pm to 2 pm. If the depth
is less than 0.5 pm, the effect as a "trigger of the
inclination of the liquid crystals" when a voltage is
applied is insufficient and if the depth exceeds 2 pm,
5 the flow of the liquid crystals during manufacturing of
liquid crystal cells may be hindered. The shoulder
portion of the projection can similarly be used when
the tilt of liquid crystal is used for the inclination
of liquid crystals.
10 The projection may have a round shape and the
semilunar, trapezoidal, and triangular shapes can be
illustrated as the sectional shape thereof. The angle
of gradient with the substrate surface of the
projection does not specifically have to be specified
15 because the whole height of the projection described
above only needs to exceed 0.5 pm. Though it is
necessary to consider the aperture ratio (transmittance
as a pixel), the angle of gradient may be a low angle
like 2° or 3° and any shape excluding an inverse
20 tapered shape (inverted trapezoidal shape with a larger
upper side) is allowed. However, the angle of gradient
is preferably in the range of effectively 30° to 80° to
obtain an appropriate aperture ratio. The flow of
liquid crystal when the liquid crystal is enclosed is
25 hindered if the height from the normal transmission
area surface of the height exceeds 2 pm and thus, the
height thereof is preferably 2 pm or less.
21
When a liquid crystal of negative dielectric
constant anisotropy is applied to the present
invention, as will be described later, the liquid
crystals on the surface of a color filter substrate for
5 a liquid crystal display device according to the
present invention performs an operation of inclining in
the direction of the linear resin layer of the
projection triggered by liquid crystal molecules near
the shoulder portion of the recess. To incline the
10 liquid crystals in symmetrical directions with the
linear resin layer of the projection, respective
differences in height of the bottom position of the
recess, the position of the top surface of the color
layers in the normal display area, and the position of
15 the apex of the projection from the surface of the
transparent substrate can be formed higher in this
order. The top surface of the normal display area is
either a protective layer by a transparent resin or a
color layer without formation of a protective layer.
20 Technical terms in the present embodiment will
briefly be described.
The black matrix is a light-shielding pattern
disposed around a picture element as the minimum unit
of display or on both sides of a picture element to
25 enhance contrast of the liquid crystal display. The
light-shielding layer is a light-shielding coating film
in which light-shielding pigments are dispersed in a
,-------
22
transparent resin, has generally photosensitivity
attached thereto, and is obtained by pattern formation
using the method of photolithography including
exposure/development.
5 The pixel refers to an opening of a black matrix
and is synonymous with the picture element. The pixel
normally has a polygonal shape, particularly a
polygonal shape in which opposite sides are parallel.
Polygons in which opposite sides are parallel include a
10 quadrangle like a rectangle shown in FIG. 15, a
parallelogram shown in FIGS. 17 and 18, a hexagon, and
a polygon bent in the center of a pixel shown in
FIG. 16.
The color layer is a coating film in which an
15 organic pigment described later is dispersed in a
transparent resin and is formed as a pattern on a
rectangular pixel by the method of photolithography. A
portion of a color pixel positioned above the linear
resin layer described above and a superimposed portion
20 on the black matrix are also called the color layer.
The liquid crystal that can be applied to the
present invention is a liquid crystal whose initial
alignment (when no drive voltage is applied) is
vertically aligned or horizontally aligned. Alignment
25 processing like rubbing can be omitted for a vertically
aligned liquid crystal whose dielectric constant
anisotropy is negative.
23
Conductive metal-oxides such as ITO described
above can be used as a material of the first electrode
and second electrode on the array substrate side of a
liquid crystal display device according to the present
5 embodiment. Alternatively, a metal whose conductivity
is higher than that of metal-oxides may be adopted.
Further, a thin film of aluminum or aluminum alloy may
be used for one of the first electrode and second
electrode for a reflective-type or semi-transflective
10 liquid crystal display device. As shown in FIG. 1, a
first electrode 1, a second electrode 2, and a metallic
wire of an active element are formed via an insulating
layer 22 such as silicon nitride (SiNx), silicon oxide
(SiOx) or the like. In FIG. 1, a TFT element and
15 metallic wires connected to the TFT element are
omitted. Incidentally, the technology to form each of
a gate wire and a source wire from a single layer of
aluminum alloy having a low contact property with ITO
as conductive metal-oxides is disclosed by Jpn. Pat.
20 Appln. KOKAI Publication No. 2009-105424.
In the present embodiment, the relative dielectric
constant of a color layer is a relatively important
property, but is almost uniquely determined by the
ratio of the organic pigment added as a coloring agent
25 to the transparent resin and it is difficult to change
the relative dielectric constant significantly. In
other words, the type of organic pigment and content in
24
the color layer are set from the color purity necessary
for a liquid crystal display device and also the
relative dielectric constant in the color layer is
thereby practically determined. The relative
5 dielectric constant can be increased to 4 or more by
increasing the ratio of the organic pigment and making
the color layer thinner. The relative dielectric
constant can be increased a little by using a high
refractive index material as the transparent resin.
10 The relative dielectric constant of a color layer using
the organic pigment generally falls within the range of
2.9 to 4.5.
The thickness of a color layer or resin layer may
be optimized in relation to a cell gap of the liquid
15 crystal to be used (thickness of the liquid crystal
layer). If, for example, the thickness of a color
layer or resin layer becomes thinner from the viewpoint
of necessary electric characteristics, the thickness of
the liquid crystal layer can be increased. If the
20 thickness of the former is thick, the thickness of the
liquid crystal layer can correspondingly be made
thinner. Incidentally, the resin layer is synonymous
with the protective layer formed of a transparent resin
such as an acrylic resin described later.
25 The linear resin layer as a component of a color
filter substrate or liquid crystal display device
according to the present embodiment is formed of a
25
transparent resin in the visible range. When a
coloring material is dispersed in such a linear resin
layer, the color balance during dynamic display of the
red pixel, green pixel, and blue pixel can be adjusted.
5 The thickness of the color layer in a laminated portion
with the linear resin layer only needs to be a thin
thickness necessary for dynamic display and can
appropriately be adjusted depending on the liquid
crystal display device or the liquid crystal to be
10 applied. Normally, the thickness of 1/3 to 1/4 the
pixel thickness (thickness of the color layer in the
normal display area) allows visual recognition of
coloring sufficiently and thus, the thickness about 1/4
the pixel thickness may be adopted.
15 By changing the relative dielectric constant or
thickness of the linear resin layer, responsiveness
(amount of inclination of alignment) to the applied
voltage to the liquid crystal near the projection above
the linear resin layer can be adjusted. The linear
20 resin layer can also be caused to contain particles of
a high refractive index or a material having dielectric
constant anisotropy.
In the halftone display of a liquid crystal
display device of initial vertical alignment or initial
25 horizontal alignment after the application of a drive
voltage, the display may take on a yellow tinge
depending on the viewing angle in the oblique
26
direction. In the present embodiment, such unintended
coloring can be reduced by simply fine-tuning the
thickness of the color layer laminated with the linear
resin layer or in contact with the linear resin layer.
5 To counter an increasing yellow tinge, the
transmittance of the blue pixel may be increased. As a
simple method of realizing the increased transmittance,
the blue transmitted light can relatively be increased
by increasing the width or height of the linear resin
10 layer formed in the blue pixel. Conversely, the width
or height of the linear resin layer formed in the red
pixel or green pixel may be decreased. The thickness
of the color layer formed on the linear resin layer or
the area of a dynamic display area described later is
15 varied by adjusting the width/height of the linear
resin layer and, as a result, the transmittance of the
color pixel can be adjusted so that the color balance
can be adjusted.
Normally, in a transmissive liquid crystal display
20 device, the white balance is optimized by tuning
optical characteristics of optical members such as a
phase difference layer and the thickness of a liquid
crystal under the assumption of light transmission from
a backlight. When a transmissive liquid crystal
25 display device is used as a reflective display or
transflective liquid crystal display device, there is
an optical path difference or a difference in incident
27
light and the double refraction factor of optical
members cannot be made the same as that of the
transmissive display and thus, a subtle color shift
arises. When a color filter substrate according to the
5 present embodiment is used not only for a transmissive
display, but also for a reflective display or
transflective liquid crystal display device, the color
balance can be adjusted by adjusting the width or
height of the linear resin layer by color to change the
10 thickness or area of the color layer.
The linear resin layer extends in a direction
perpendicular to the paper surface in FIG. 1 or the
like, but may also extend in a direction parallel to
the paper surface, that is, in a cross direction. In
15 such a case, also the comb-like first and second
electrodes need to be arranged in the cross direction.
Instead of the linear resin layer, a cross-shaped
resin layer in a plane view may also be provided.
In the present embodiment, liquid crystals of both
20 negative dielectric constant anisotropy and positive
dielectric constant anisotropy can be used. For
example, a nematic liquid crystal whose double
refraction factor near room temperature is about 0.1
can be used as a liquid crystal of negative dielectric
25 constant anisotropy. A liquid crystal of positive
dielectric constant anisotropy has a wide selection
range and thus, various liquid crystal materials can be
28
applied. The thickness of the liquid crystal layer is
not specifically limited, but to realize a liquid
crystal display of ultra high-speed response, a thin
liquid crystal layer of the thickness of 3.5 ~m or
5 less, preferably in the range of 1.5 ~m to 3.4 ~m can
be created. In the present invention using both an
oblique electric field and protruding electrode
technology, a liquid crystal display device whose power
consumption is lower than before can be provided by
10 optimizing the viscosity of liquid crystal, its
dielectric constant anisotropy, double refraction
factor, and elastic constant. ~nd of the liquid
crystal layer that can be effectively used in the
present embodiment is in the range of about 250 nm to
15 500 nm.
As an alignment layer whose illustration is
omitted, for example, a polyimide polymeric organic
film or a polymeric organic film having a polysiloxane
structure after being hardened by heating can be used.
20 Alternatively, one to three phase difference plates may
be used in a form of pasting to a polarizing plate.
The action in a configuration in which a
transparent conducting film is laminated as a third
electrode on a color filter substrate according to the
25 present embodiment and the action of a recess on a
black matrix and a superimposed portion of a linear
resin layer and a color layer will be described below.
29
FIG. 1 is a schematic sectional view of a liquid
crystal display device according to the first
embodiment of the present invention. The liquid
crystal display device has a configuration in which a
5 color filter substrate for a liquid crystal display
device (hereinafter, referred to as a color filter
substrate) 11 and an array substrate 21 are provided in
a form of sandwiching a liquid crystal 17 therebetween.
A color filter substrate 11 is configured by
10 sequentially forming a black matrix 5, a third
electrode 3 as a transparent conducting film, a linear
resin layer 4, a read pixel 15, a green pixel 14, a
blue pixel 16, and a protective layer 18 on a
transparent substrate lOa. A recess 23 is formed above
15 (below in FIG. 1) the black matrix 5. The array
substrate 21 has a first electrode 1 and a second
electrode 2 formed on a transparent substrate lOb via
an insulating layer 22. The illustration of an
alignment film, polarizing plate, phase difference
20 plate and the like is omitted.
FIG. 2 is a sectional view showing an alignment
state of a vertically aligned liquid crystal 17 on the
green pixel 14 as a rectangular pixel in a plane view
in FIG. 1. The polarizing plate is assumed to be a
25 cross Nicol prism and a normally black liquid crystal
display device is assumed. FIG. 2 shows alignment
states of liquid crystal molecules 17a, 17b, 17c, 17d
30
of the vertically aligned liquid crystal 17 when no
voltage is applied to the third electrode 3 as a
transparent conducting film provided on the color
filter substrate and the first electrode 1 and the
5 second electrode 2 provided on the array substrate 21.
While the liquid crystal in the center of the
green pixel 14 (1/2 pixel) is aligned perpendicularly
to the surface of the green pixel, the liquid crystal
molecules 17a, 17d of a shoulder portion 14a of the
10 recess 23 and the liquid crystal molecules 17b, 17c of
a shoulder portion 14b of the projection 24 are
slightly obliquely aligned.
If, as shown in FIG. 3, a liquid crystal driving
voltage is applied while the liquid crystal molecules
15 17a, 17b, 17c, 17d are obliquely aligned, the liquid
crystal molecules 17a, 17d incline in the direction of
an arrow A. Liquid crystal molecules near the recess
23 above the black matrix 5 are closer to the third
electrode 3 as a transparent conducting film due to the
20 recess, are more likely to be subject to an applied
voltage between the third electrode and the first
electrode as a pixel electrode, and start to incline
immediately after the voltage being applied. The
inclination of the liquid crystal molecules 17a, 17d
25 functions as a trigger and the inclination propagates
to adjacent liquid crystal molecules and, as shown in
FIG. 4, the liquid crystal inclines in a direction of
31
the center of the rectangular pixel where the linear
resin pixel 4 is formed to change to the green display
due to light transmission. That is, the normal
transmission area shown in FIG. 4 is in the green
5 display during normal gradation display.
FIG. 4 is a diagram showing an alignment state of
liquid crystal molecules during a white display (FIG. 4
is shown with a green pixel and thus, the color
specification is green) after the drive voltage being
10 applied. As shown in FIG. 4, liquid crystal molecules
in the normal display area are aligned almost in
parallel with the substrate surface. Liquid crystal
molecules above the projection 24 in the center of the
rectangular pixel with the linear resin layer as a core
15 remain vertically aligned or do not incline
sufficiently in the green display (normal display area
in FIG. 4) during gradation display and thus, the
dynamic display area in the pixel center becomes a
black or dark display. The liquid crystal molecules
20 17a, 17b, 17c, 17d in the shoulder portions of the
recess and the projection practically have a tilt
attached thereto when no voltage is applied without
performing alignment processing such as rubbing.
As shown in FIG. 4, the direction in which the
25 liquid crystals incline is reversed in the 1/2 pixel on
the opposite side (right side) of the green pixel 14.
This means that optical compensation in the halftone
32
display can be made only by the magnitude of the drive
voltage and a wide angle of visibility can be secured
without forming four multi-domains like an MVA liquid
crystal. In the halftone (for example, a state in
5 which each liquid crystal molecule is oblique), the
liquid crystal alignment in which the 1/2 green pixel
and the 1/2 green pixel on the opposite side have
inclination gradients in the opposite direction and
these 1/2 pixels facing with each other optically
10 average to widen the angle of visibility.
FIG. 5 is a diagram illustrating the alignment of
the liquid crystal when a still higher voltage is
applied. That is, with the application of a still
higher voltage, liquid crystal molecules 27a, 27b near
15 the projection 24 are aligned in a direction
perpendicular to an electric line of force 34 (aligned
in a direction parallel to the surface of the substrate
lOb) . Due to the alignment of the liquid crystal
molecules 27a, 27b described above, light is
20 transmitted through the dynamic display area. A thin
color layer is stacked on the linear resin layer 4 in
the dynamic display area and thus, bright green is
displayed in the state shown in FIG. 5. Because the
linear resin layer as a dielectric material and the
25 color layer are formed on the third electrode 3 thickly
in the projection 24, in contrast to the normal pixel
area, a voltage higher than that for normal display is
33
needed as a drive voltage to drive the liquid crystal
molecules 27a, 27b.
By disposing two TFT elements (active elements) in
one pixel and driving a set of first electrodes on the
5 inner side near the dynamic display area shown in
FIG. 5 by one TFT element separately, the brightness of
the dynamic display can advantageously be adjusted
independently.
In the foregoing, behavior of liquid crystal
10 molecules near the color filter substrate has been
described, in a liquid crystal display device according
to another embodiment of the present invention, liquid
crystal molecules can be inclined in similar directions
also on the side of the array substrate like on the
15 side of the color filter substrate. Such an example
will be described below as a case when a liquid crystal
whose dielectric constant anisotropy is negative is
used.
In the liquid crystal display device shown in
20 FIG. 6, the first electrode is set as comb-like
electrodes la, lb, lc, ld and similarly, the second
electrode is set as comb-like electrodes 2a, 2b, 2c,
2d. Liquid crystal molecules 37a, 37b, 37c, 37d near
the first electrodes la, lb, lc, ld are aligned almost
25 vertically when no voltage is applied.
In the liquid crystal display device shown in
FIG. 6, the second electrodes 2a, 2b, 2c, 2d are
34
arranged by shifting so as to protrude from ends of the
first electrodes la, lb, lc, ld so that ends thereof
topple the liquid crystal 37a in the direction of a
projection 24 in the center of the rectangular pixel
5 when a drive voltage is applied. An amount of shift 28
can be adjusted in various ways by dimensions like
liquid crystal materials to be used, the drive voltage,
and the thickness of liquid crystal cells. A small
amount like 1 ~m to 5 ~m is sufficient as the amount of
10 shift 28. The width of an overlapping portion of the
first electrodes la, lb, lc, ld and the second
electrodes 2a, 2b, 2c, 2d respectively is indicated as
reference numeral 29. The illustration of an alignment
film is omitted. The overlapping portion can be used
15 as an auxiliary capacity when necessary.
FIG. 7 shows an operation of the liquid crystal
molecules 37a, 37b, 37c, 37d immediately after the
voltage to drive the liquid crystal being applied and
also electric lines of force 30a, 30b, 30c, 30d. The
20 liquid crystal molecules 37a, 37b, 37c, 37d incline in
the direction of electric lines of force after the
voltage application. The direction in which the liquid
crystal molecules incline is the same as the direction
in which the liquid crystal molecules 17a, 17b, 17c,
25 17d shown in FIG. 3 incline and thus, the liquid
crystal molecules in the illustrated green pixel 14
inclines instantaneously in the same direction so that
35
responsiveness of the liquid crystal can significantly
be improved.
The direction of shift (protruding portion) of the
second electrode is desirably symmetric with respect to
5 a point or line in the center of the rectangular pixel
and in the opposite directions. In addition, the shift
is desirably a pattern protruded in a direction toward
the linear resin layer in a plane view. The pattern of
a comb-like electrode may be a V shape or oblique.
10 Alternatively, as shown in FIG. 8, the pattern may be a
comb-like pattern whose alignment is changed by 90° in
units of 1/4 pixel. Accordingly, when the voltage to
drive the liquid crystal is applied, the inclinations
are divided into four domains symmetrically with
15 respect to a point in a plane view and the display area
of the rectangular pixel is divided into 4 domain
areas. In this case, the comb-like electrode can be
oblique in the direction of 45° with respect to the
center line of the rectangular pixel. Also, these
20 electrode patterns are desirably symmetric with respect
to a point or line when viewed from the pixel center.
The numbers of first electrodes and second electrodes
can appropriately be selected.
While the voltage to drive the liquid crystal is
25 applied to a first electrode 1, a common potential
(common) may be set to a second electrode 2 and a third
electrode 3. The overlapping portion 29 of the first
36
and second electrodes shown in FIG. 6 can be used as an
auxiliary capacity.
Other examples of the plane view pattern shape of
the first electrode 1 that can be applied to the above
5 embodiment are shown in FIGS. 15, 16, 17, and 18. In
FIGS. 15, 16, 17, and 18, reference numeral 25 shows an
opening (color pixel shape of a polygon) of a black
matrix 5 and reference numeral 9 shows the direction in
which the liquid crystals incline. FIGS. 17 and 18
10 illustrate the opening 25 in two pixels having
different angle of obliquity. That is, if the drive
voltage is applied to the first electrode 1 and the
common potential (common) is set to the second
electrode 2 and the third electrode 3, liquid crystal
15 molecules in these pixels incline in the direction 9 in
units of 1/2 pixels. In pixels in parallelogrammic
shapes having different angle of obliquity, for
example, in pixels in FIGS. 17 and 18, four different
directions in which the liquid crystals incline can be
20 set in total so that a liquid crystal display device
with a wide angle of visibility can be provided.
The liquid crystal operation has been described by
taking a liquid crystal of initial vertical alignment
having negative dielectric constant anisotropy as an
25 example, but a similar effect can be achieved by using
a liquid crystal of initial horizontal alignment having
positive dielectric constant anisotropy. Therefore,
37
the present invention can use a horizontally aligned
liquid crystal. In an initially horizontally aligned
liquid crystal, the liquid crystal rises vertically
from the surface of the substrate lOb after the
5 application of the drive voltage so that light is
transmitted. When a horizontally aligned liquid
crystal is used, rubbing treatment of the alignment
film is needed to uniquely determine the alignment
direction of the liquid crystal.
10 The first electrode and second electrode in
FIGS. 6 and 7 have a comb-like pattern, but may have,
instead of the comb-like pattern, a slit pattern
cutting an opening like a slit. Also the slit pattern
can obtain a similar effect by protruding the second
15 electrode from the end of the first electrode in the
direction of the linear resin layer.
The following method can be used to make the
direction of the inclination of liquid crystal
molecules above protruding portions of the second
20 electrodes 2a, 2b, 2c, 2d easier.
1) Attach a taper to the ends of the first
electrodes la, lb, lc, ld
2) Make the thickness of the first electrodes la,
lb, lc, ld thicker
25 3) Etch a portion of the insulating layer below
the first electrodes la, lb, lc, ld to make the
insulating layer on the second electrodes 2a, 2b, 2c,
38
2d thinner.
By attaching a small pre-tilt angle of, for
example, 0.1° to 1° to initially vertically aligned
liquid crystal molecules in this manner, inclining
5 liquid crystal molecules can be aligned and liquid
crystal molecules can be made more likely to incline at
a low voltage so that responsiveness is improved and
also improvements in low gradation display are made.
The pre-tilt angle is a pre-tilt amount when the
10 direction perpendicular to the substrate surface is set
to 0°.
By using, for example, an oxide semiconductor as a
channel material of the TFT as an active element
provided in a liquid crystal display device, the
15 aperture ratio of a pixel can be improved. Typical
examples of the oxide semiconductor include a compound
metal-oxides of indium, gallium, and zinc called IGZO.
A liquid crystal material (fluorine liquid
crystal) containing fluorine atoms in a molecular
20 structure can be used as a liquid crystal material. A
strong electric field is practically generated in a
protruding portion of the second electrode from the
first electrode when a voltage to drive the liquid
crystal is applied and thus, the liquid crystal can be
25 driven by using a liquid crystal material whose
dielectric constant is lower (dielectric constant
anisotropy is smaller) than that of a conventional
5
39
liquid crystal used for vertical alignment. In
general, a liquid crystal having small dielectric
constant anisotropy has a low viscosity and can make
the fall time when the drive voltage is turned off
shorter. In addition, a fluorine liquid crystal has a
small dielectric constant and thus, the captured amount
of ionic impurities is small and degradation in
performance such as lower voltage retention caused by
impurities is small, providing advantages of less
10 display irregularities and burn-in.
Transparent resins and organic pigments that can
be used for a color filter substrate according to the
embodiments described above will be illustrated below.
(Transparent resin)
15 A photosensitive coloring composition used for
forming a light-shielding layer or color layer
contains, in addition to pigment dispersion, a
polyfunctional monomer, photosensitive resin or nonphotosensitive
resin, polymerization initiator, solvent
20 and the like. Highly transparent organic resins that
can be used for the embodiments of the present
invention such as the photosensitive resin and nonphotosensitive
resin will generically be called
transparent resins.
25 Transparent resins include thermoplastic resins,
thermosetting resins, and photosensitive resins.
Thermoplastic resins include, for example, a butyral
40
resin, styreme-maleate copolymer, chlorinated
polyethylene, chlorinated polypropylene, polyvinyl
chloride, vinyl chloride-vinyl acetate copolymer,
polyvinyl acetate, polyurethane resin, polyester resin,
5 acrylic resin, alkyd resin, polystyrene resin,
polyamide resin, rubber resin, cyclorubber resin,
celluloses, polybutadiene, polyethylene, polypropylene,
and polyimide resin. Thermosetting resins include, for
example, an epoxy resin, benzoguanamine resin, rosin
10 modified maleic resin, rosin modified fumaric resin,
melamine resin, urea resin, and phenolic resin. A
resin obtained by allowing a melamine resin and a
compound containing an isocyanate group to react may be
used as a thermosetting resin.
15 (Alkali soluble resin)
It is preferable to use a photosensitive resin
composition capable of forming a pattern by
photolithography to form a light-shielding layer, light
scattering layer, color layer, and cell gap regulating
20 layer. Such transparent resins are preferably resins
to which alkali solubility is attached. Alkali soluble
resins are not specifically limited as long as a resin
contains a carboxyl group or hydroxyl group. For
example, an epoxy acrylate resin, novolac resin,
25 polyvinyl phenolic resin, acrylic resin, carboxyl group
containing epoxy resin, and carboxyl group containing
urethane resin. Among others, the epoxy acrylate
5
41
resin, novolac resin, and acrylic resin are preferable
and the epoxy acrylate resin and novolac resin are
particularly preferable.
(Acrylic resin)
The following acrylic resins can be illustrated as
representative transparent resins that can be adopted
for the above embodiments.
Acrylic resins include as monomers, for example,
(meta) acrylic acid; alkyl (meta) acrylate such as
10 methyl (meta) acrylate, ethyl (meta) acrylate, propyl
(meta) acrylate, butyl (meta) acrylate, t-butyl (meta)
acrylatebenzyl (meta) acrylate, and lauryl (meta)
acrylate; hydroxyl group containing (meta) acrylate
such as hydroxylethyl (meta) acrylate and
15 hydroxylpropyl (meta) acrylate; ether containing (meta)
acrylate such as ethoxyethyl (meta) acrylate and
glycidyl (meta) acrylate; and a polymer obtained by
using alicyclic (meta) acrylate such as cyclohexyl
(meta) acrylate, isobornyl (meta) acrylate, and
20 dicyclopentenyl (meta) acrylate.
The monomers cited above can be used alone or
combining two or more monomers. Further, a copolymer
obtained by copolymerizing these monomers with a
compound such as styrene, cyclohexyl maleimide, and
25 phenyl maleimide that can be copolymerized may be used.
A resin having photosensitivity can also be
obtained by causing to react a copolymer obtained by
42
copolymerizing, for example, carboxylic acid having an
ethylene unsaturated group such as (meta) acrylic acid
and a compound containing an epoxy group and
unsaturated double bonds such as glycidyl methacrylate
5 or adding a carboxylic acid containing compound such as
(meta) acrylic acid to a polymer of epoxy group
containing (meta) acrylate such as glycidyl
methacrylate or a copolymer of epoxy group containing
(meta) acrylate and other (meta) acrylate.
10 Further, a resin having photosensitivity can also
be obtained by causing, for example, a polymer having a
hydroxyl group of a monomer such as hydroxylethyl
methacrylate to react with a compound having an
isocyanate group and ethylene unsaturated group such as
15 methacryloyl oxyethylisocyanate.
Also, as described above, a resin having a
carboxyl group can be obtained by causing a copolymer
having a plurality of hydroxyl groups such as
hydroxylethyl methacrylate and polybasic acid anhydride
20 to introduce a carboxyl group into a copolymer.
However, the method of producing a resin having a
carboxyl group is not limited to the above method.
Examples of anhydride used for the above reaction
include, for example, malonic anhydride, succinic
25 anhydride, maleic anhydride, itaconic anhydride,
phthalic anhydride, tetrahydrophthalic anhydride,
hexahydrophthalic anhydride, methyl tetrahydrophthalic
43
anhydride, and trimellitic anhydride.
The solid content acid value of the above acrylic
resins is preferably 20 to 180 mgKOH/g. If the acid
value is less than 20 mgKOH/g, the developing speed of
5 a photosensitive resin composition is too slow and a
more time is needed for development, which tends to
result in low productivity. If the solid content acid
value is more than 180 mgKOH/g, conversely the
developing speed is too fast, which tends to result in
10 pattern peeling or missing pattern after development.
Further, if the above acrylic resin has
photosensitivity, the double-bond equivalent of the
acrylic resin is desirably 100 or more, more desirably
100 to 2000, and most desirably 100 to 1000. If the
15 double-bond equivalent exceeds 2000, adequate photosetting
properties may not be obtained.
(Photopolymerization monomer)
Examples of the photopolymerization monomer
include various kinds of acrylate such as 2-
20 hydroxylethyl (meta) acrylate, 2-hydroxylpropyl (meta)
acrylate, cyclohexyl (meta) acrylate,
polyethyleneglycol di (meta) acrylate, pentaerythritol
(meta) acrylate, trimethylolpropan tri (meta) acrylate,
dipentaerythritol hexa (meta) acrylate, tricyclodecanyl
25 (meta) acrylate, melamine (meta) acrylate, and epoxy
(meta) acrylate, and methacrylate, (meta) acrylic acid,
styrene, vinyl acetate, (meta) acrylamide,
44
N-hydroxymethyl (meta) acrylamide, and acrylonitrile.
It is preferable to use polyfunctional urethane
acrylate obtained by causing (meta) acrylate having a
hydroxyl group and polyfunctional isocyanate to react
5 and having a (meta) acryloyl group. The combination of
(meta) acrylate having a hydroxyl group and
polyfunctional isocyanate is arbitrary and is not
specifically limited. Also, one type of polyfunctional
urethane acrylate may be used alone or two types or
10 more may be combined.
(Photopolymerization initiator)
As photopolymerization initiators, an acetophenone
compound such as 4-phenoxy dichloroacetophenone, 4-tbutyl-
dichloroacetophenone, diethoxyacetophenone, 1-(4-
15 isopropyl phenyl)-2-hydroxy-2-methylpropane-1-on, 1-
hydroxycyclohexyl phenyl. ketone, and 2-benzyl-2-
dimethylamino-1-(4-morpholino phenyl)-butane-1-on; a
benzoin compound such as benzoin, benzoin methyl ether,
benzoin ethyl ether, benzoin isopropyl ether, and
20 benzyl dimethylketal; a benzophenone compound such as
benzophenone, benzoylbenzoate, methyl benzoylbenzoate,
4-phenylbenzophenone, hydroxybenzophenone, acrylic
benzophenone, and 4-benzoyl-4'-methyldiphenylsulfide; a
thioxanthene compound such as thioxanthene, 2-
25 chlorothioxanthene, 2-methylthioxanthene,
isopropylthioxanthene, and 2, 4-
diisopropylthioxanthene; a triazine compound such as 2,
45
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-pipenyl-4, 6-bis
5 (trichloromethyl)-s-triazine, 2, 4-bis
(trichloromethyl)-6-styryl s-triazine, 2-(naphtho-1-
yl)-4, 6-bis (trichloromethyl)-s-triazine, 2-(4-
methoxy-naphtho-1-yl)-4, 6-bis (trichloromethyl)-striazine,
2, 4-trichloromethyl-(piperonyl)-6-triazine,
10 and 2, 4-trichloromethyl (4'-methoxystyryl)-6-triazine,
an oxime ester compound such as 1,2-octanedione, 1-[4-
(phenylthio)-, 2-(0-bemzoyloxime)] and 0-(acetyl)-N-(1-
phenyl-2-oxo-2-(4'-methoxy naphthyl) ethylidene)
hydroxylamine; a phosphine compound such as bis (2, 4,
15 6-trimethylbenzoyl) phenylphosphine·oxide and 2, 4, 6-
trimethylbenzoyl diphenylphosphine oxide; a quinone
compound such as 9, 10-phenanthrene quinone, camphor
quinone, and ethyl anthraquinone; a borate compound; a
carbazole compound; an imidazole compound; and a
20 titanocene compound can be cited. Oxime derivatives
(oxime compounds) are effective to improve sensitivity.
These photopolymerization initiators can be used alone
or by combining two or more.
25
(Sensitizer)
It is preferable to use photopolymerization
initiators and sensitizers in combination. As
sensitizers, compounds such as a-acyloxy ester,
46
acylphosphine oxide, methylphenyl glyoxylate, benzyl-9,
10-phenanthrene quinone, camphor quinone, ethyl
anthraquinone, 4, 4'-diethyl isophthalophenone, 3, 3',
4, 4'-tetra (t-butylperoxy carbonyl) benzophenone, and
5 4, 4'-diethylamino benzophenone.
An quantity of 0.1 to 60 mass parts of sensitizers
to 100 mass parts of photopolymerization initiators can
be contained.
(Ethylene unsaturated compound)
10 The above photopolymerization initiators are
preferably used by being combined with ethylene
unsaturated compounds. The ethylene unsaturated
compound means a compound having at least one ethylene
unsaturated bond in the molecule. Among others, an
15 ethylene unsaturated compound having two ethylene
unsaturated bonds in the molecule or more is preferably
from the viewpoint of being able to increase
differences in polymerizability, cross linkage, and
developer solubility between an exposed portion and a
20 non-exposed portion accompanying the polymerizability
and cross linkage. Particularly, a (meta) acrylate
compound whose unsaturated bond is derived from a
(meta) acryloyloxy group is preferable.
Compounds containing at least one ethylene
25 unsaturated bond in the molecule include, for example,
unsaturated carboxylic acid such as (meta) acrylic
acid, crotonic acid, isocrotonic acid, maleic acid,
47
itaconic acid, and citraconic acid and acrylate
thereof; (meta) acrylonitrile; (meta) acrylamide; and
styrene. Compounds containing two ethylene unsaturated
bonds or more in the molecule typically include, for
5 example, esters of unsaturated carboxylic acid and
polyhydroxyl compounds, (meta) acryloyloxy group
containing phosphates, urethane (meta) acrylates of
hydroxyl (meta) acrylate compounds and polyisocyanate
compounds, and epoxy (meta) acrylates of hydroxyl
10 (meta) acrylate compounds and polyepoxy compounds.
The above photopolymerization initiators,
sensitizers, and ethylene unsaturated compounds may be
added to a composition containing polymerization liquid
crystal compounds used for forming a phase difference
15 layer described later.
(Polyfunctional thiol)
Polyfunctional thiol acting as a chain transfer
agent can be contained in a photosensitive coloring
composition. Polyfunctional thiol may be any compound
20 having two thiol groups or more and includes, for
example, hexanedithiol, decanedithiol, 1, 4-
butanediolbisthio propionate, 1, 4-butanediolbisthio
glycolate, ethyleneglycolbisthio glycolate,
ethyleneglycolbisthio propionate,
25 trimethylolpropanetristhio glycolate,
trimethylolpropanetristhio propionate,
trimethylolpropanetris (3-mercaptobutyrate),
48
pentaerythritoltetrakisthio glycolate,
pentaerythritoltetrakisthio propionate, trimercapto
propionate tris (2-hydroxyethyl) isocyanurate, 1, 4-
dimethylmercaptobenzene, and 2, 4, 6-trimercapto-s-
5 triazine, 2-(N, N-dibutylamino)-4, 6-dimercapto-striazine.
The above polyfunctional thiol can be used alone
or by combining two types or more. Polyfunctional
thiol can be used in a photosensitive coloring
10 composition in a quantity of preferably 0.2 to 150 mass
parts, particularly preferably 0.2 to 100 mass parts to
100 mass parts of pigment.
(Storage stabilizer)
Storage stabilizers can be contained in a
15 photosensitive coloring composition to stabilize the
viscosity with time of the composition. Storage
stabilizers include, for example, quaternary ammonium
chloride such as benzyltrimethyl chloride and
diethylhydroxyamine, organic acid such as lactic acid
20 and oxalic acid and methyl ether thereof, organic
phosphine such as t-butylpyrocatechol, triethyl
phosphine, and triphenyl phosphine, and phosphite.
Storage stabilizers can be contained in a quantity of
0.1 to 10 mass parts to 100 mass parts of pigment in
25 the photosensitive coloring composition.
(Close contact improver)
Close contact improvers such as a silane coupling
49
agent can be contained in a photosensitive coloring
composition to enhance close contact with a substrate.
Silane coupling agents include vinylsilanes such as
vinyltris (~-methoxyethoxy) silane, vinylethoxysilane,
5 and vinyltrimethoxysilane, (meta) acrylsilanes such as
y-methacryloxypropyl trimethoxysilane, epoxysilanes
such as ~-(3, 4-epoxycyclohexyl) ethyltrimethoxysilane,
~-(3, 4-epoxycyclohexyl) methyltrimethoxysilane, ~-(3,
4-epoxycyclohexyl) ethyltriethoxysilane, ~-(3, 4-
10 epoxycyclohexyl) methyltriethoxysilane, yglycidoxypropyl
trimethoxysilane, and y-glycidoxypropyl
triethoxysilane, aminesilanes such as N-~(
aminoethyl)y-aminopropyl trimethoxysilane, N-~(
aminoethyl)y-aminopropyl triethoxysilane, N-~-
15 (aminoethyl)y-aminopropyl methyldiethoxysilane, yaminopropyl
triethoxysilane, y-aminopropyl
trimethoxysilane, N-phenyl-y-aminopropyl
trimethoxysilane, and N-phenyl-y-aminopropyl
triethoxysilane, and thiosilanes such as y-
20 mercaptopropyl trimethoxysilane and y-mercaptopropyl
triethoxysilane. The silane coupling agent can be
contained in a quantity of 0.01 to 100 mass parts to
100 mass parts of pigment in the photosensitive
coloring composition.
25 (Solvent)
Solvents such as water and organic solvents are
mixed into a photosensitive coloring composition to
50
enable uniform coating on a substrate. When the
composition used for the present embodiment is a color
layer of a color filter, the solvent also has a
function to disperse the pigment uniformly. Solvents
5 include, for example, cyclohexanone, ethylcellosolve
acetate, butylcellosolve acetate, 1-methoxy-2-propyl
acetate, diethyleneglycol dimethyl ether, ethylbenzene,
ethyleneglycol diethyl ether, xylene, ethylcellosolve,
methyl-n amylketone, propyleneglycol monomethyl ether,
10 toluene, methylethyl ketone, ethyl acetate, methanol,
ethanol, isopropyl alcohol, butanol, isobutyl ketone,
and a petroleum solvent and these solvents may be used
alone or by combining two or more. Solvents can be
contained in a photosensitive coloring composition in a
15 quantity of 800 to 4000 mass parts, preferably 1000 to
2500 mass parts to 100 mass parts of pigment.
(Organic pigment)
As red pigments, for example, C. I. Pigment Red 7,
9, 14, 41, 48:1, 48:2, 48:3, 48:4, 81:1, 81:2, 81:3,
20 97, 122, 123, 146, 149, 168, 177, 178, 179, 180, 184,
185, 187, 192, 200, 202, 208, 210, 215, 216, 217, 220,
223, 224, 226, 227, 228, 240, 246, 254, 255, 264, 272,
279 or the like can be used.
As yellow pigments, for example, C. I. Pigment
25 Yellow 1, 2, 3, 4, 5, 6, 10, 12, 13, 14, 15, 16, 17,
18, 20, 24, 31, 32, 34, 35, 35:1, 36, 36:1, 37, 37:1,
40, 42, 43, 53, 55, 60, 61, 62, 63, 65, 73, 74, 77, 81,
51
83, 86, 93, 94, 95, 97, 98, 100, 101, 104, 106, 108,
109, 110, 113, 114, 115, 116, 117, 118, 119, 120, 123,
125, 126, 127, 128, 129, 137, 138, 139, 144, 146, 147,
148, 150, 151, 152, 153, 154, 155, 156, 161, 162, 164,
5 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176,
177, 179, 180, 181, 182, 185, 187, 188, 193, 194, 199,
213, 214 or the like can be cited.
As blue pigments, for example, C. I. Pigment Blue
15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 60, 64, 80 or
10 the like can be used. Among others, C. I. Pigment Blue
15:6 is preferable.
As violet pigments, for example, C. I. Pigment
Violet 1, 19, 23, 27, 29, 30, 32, 37, 40, 42, 50 or the
like can be used. Among others, C. I. Pigment Violet
15 23 is preferable.
As green pigments, for example, C. I. Pigment
Green 1, 2, 4, 7, 8, 10, 13, 14, 15, 17, 18, 19, 26,
36, 45, 48, 50, 51, 54, 55, 58 or the like can be used.
Among others, C. I. Pigment Green 58 is preferable.
20 In the description of pigment types of C. I.
25
Pigment below, abbreviations like PB (Pigment Blue), PV
(Pigment Violet), PR (Pigment Red), PY (Pigment
Yellow), and PG (Pigment Green) may be described.
(Coloring material of the light-shielding layer)
A color material contained in the light-shielding
layer or black matrix is a coloring material exhibiting
a light-shielding function by having absorption in a
52
visible light wavelength region. In the. present
embodiment, for example, organic pigments, inorganic
pigments, dyes and the like can be cited as the
coloring material. Inorganic pigments include, for
5 example, carbon black and titanium oxide. As dyes, for
example, azo dyes, anthraquinone dyes, phthalocyanine
dyes, quinine imine dyes, quinoline dyes, nitro dyes,
carbonyl dyes, and methine dyes can be cited. Organic
pigments described above can be adopted as organic
10 pigments. One light-shielding component may be used
alone or two or more light-shielding components may be
used in any combination and ratio. Higher volume
resistance may be achieved by resin coating with the
surface of these color materials or conversely, lower
15 volume resistance may be achieved by increasing the
content ratio of the coloring material to the base
material of the resin to provide a little conductivity.
However, the volume resistance of such light-shielding
materials is approximately in the range of 1 X 108 to
20 1 X 1015 Q·cm, which is a level that does not affect
the resistance of the transparent conducting film.
Similarly, the relative dielectric constant of the
light-shielding layer can be adjusted to the range of 3
to 11 by the selection of the color material and the
25 content ratio.
(Dispersant/dispersing agent)
Using a macromolecular dispersant as a pigment
53
dispersant is preferable because of superiority of
dispersion stability with time. As the macromolecular
dispersant, for example, a urethane dispersant,
polyethyleneimine dispersant, polyoxyethylene alkyl
5 ether dispersant, polyoxyethylene glycol diester
dispersant, sorbitan aliphatic ester dispersant, and
aliphatic modified polyester dispersant can be cited.
Among others, a dispersant made of a graft copolymer
containing particularly nitrogen atoms is preferable
10 for a light-shielding photosensitive resin composition
used in the present embodiment containing a large
quantity of pigment in terms of development.
Concrete examples of these dispersants include as
trade names EFKA (manufactured by EFKA Chemicals BV),
15 Disperbik (manufactured by BYK Japan K.K.), DISPARLON
(manufactured by Kusumoto Chemicals Ltd.), SOLSPERSE
(manufactured by Lubrizol Corporation), KP
(manufactured by Shin-Etsu Chemical Co. Ltd.), and
POLYFLOW (manufactured by Kyoeisha Chemical Co. Ltd.)
20 can be cited. One dispersant of these dispersants may
be used alone or two or more dispersants may be used in
any combination and ratio.
As the dispersing agent, for example, a pigment
derivative can be used. As pigment derivatives, for
25 example, azo, phthalocyanine, quinacridone,
benzimidazolone, quinophthalone, isoindrinone,
dioxazine, anthraquinone, indanthrene, perylene,
54
perinone, diketopyrrolopyrrole, and dioxazine
derivatives can be cited and, among others,
quinophthalone derivatives are preferable.
As the substituent group of a pigment derivative,
5 for example, a sulfonic group, sulfonamide group or
quaternary salt thereof, phthalimidemethyl group,
dialkylamino alkyl group, hydroxyl group, carboxyl
group, or amide group bonded directly to pigment
skeletons or via an alkyl group, aryl group, or
10 heterocyclic group can be cited. Among others, the
sulfonic group is preferable. These substituent groups
may be substituted in a plurality of sites.
Concrete examples of the pigment derivatives
include a sulfonic acid derivative of phthalocyanine,
15 sulfonic acid derivative of quinophthalone, sulfonic
acid derivative of anthraquinone, sulfonic acid
derivative of quinacridone, sulfonic acid derivative of
diketopyrrolopyrrole, and sulfonic acid derivative of
dioxazine.
20 One dispersing agent or pigment derivative may be
used alone or two or more dispersing agents or pigment
derivatives may be used in any combination and ratio.
Various examples of the present invention will be
described below.
25 Example 1
The color filter substrate 11 shown in FIG. 9 is
produced as shown below.
55
[Formation of a black matrix]
(Dispersant for black matrix formation)
20 mass parts of carbon pigment #47 (manufactured
by Mitsubishi Chemical Corporation), 8.3 mass parts of
5 macromolecular dispersant BYK-182 (BYK Japan K.K.), 1.0
mass part of copper phthalocyanine derivative (Toyo Ink
Co. Ltd.), and 71 mass parts of propyleneglycol
monomethylether acetate are stirred by a bead mill
dispersion machine to prepare a carbon black
10 dispersant.
(Photoresist for black matrix formation)
A resist for black matrix formation is prepared by
using the following materials:
Carbon black dispersant: Pigment #47 (Mitsubishi
15 Chemical Corporation)
20
Transparent resin: V259-ME (Nippon Steel Chemical
Co., Ltd. ) (solid portion: 56. 1% by weight)
Photopolymerization monomer: DPHA (Nippon Kayaku
Co. Ltd.)
Initiator: OXE-02 (Ciba Specialty Chemicals K.K.)
OXE-01 (Ciba Specialty Chemicals K.K.)
Solvent: Propyleneglycol monomethylether acetate
Ethyl-3-ethoxypropionate
Leveling agent: BYK-330 (manufactured by BYK Japan
25 K.K.)
The above materials are mixed and stirred in the
following composition ratio to prepare a resist for
5
56
black matrix formation (pigment concentration in the
solid portion: about 20%).
parts
parts
Carbon black dispersant
Transparent resin
Photopolymerization monomer
Photopolymerization initiator
Photopolymerization initiator
3.0 mass parts
1.4 mass parts
0.4 mass parts
OXE-01 0.67 mass
OXE-02 0.17 mass
10 Propyleneglycol monomethylether acetate
15
14 mass parts
Ethyl-3-ethoxypropionate 5.0 mass parts
Leveling agent 1.5 mass parts
(Conditions for black matrix formation)
The transparent substrate lOa made of glass is
spin-coated with the above photoresist and the
photoresist is dried to produce a coated film of
thickness 1.5 ~m. The coated film is dried at 100°C
for 3 minutes and then 200 mJ/cm2 is shone by using an
20 exposure photo mask with an opening of 24.5 ~min
pattern width (corresponding to the streak width of a
black matrix) as a black matrix and an extra-high
pressure mercury lamp as a light source.
Next, the photoresist is developed by a 2.5%
25 sodium carbonate solution for 60 seconds and is well
washed with water after the development and further
dried and then heated at 230°C for 60 minutes for
57
pattern fixation to form the black matrix 5 on the
transparent substrate lOa. The black matrix 5 has a
streak width of about 24 ~m and is formed in the
periphery (four sides) of the rectangular pixel. The
5 angle of gradient of the end of the black matrix streak
with the surface of the transparent substrate is set to
about 45 degrees.
10
15
[Film formation of the transparent conducting
film]
The transparent conducting film 3 (third
electrode) made of ITO (metal-oxides film of indium and
tin) is formed to a thickness of 0.14 ~m like covering
the entire surface of the black matrix 5 described
above by using a sputtering apparatus.
[Formation of the linear resin layer]
(Synthesis of the resin A)
686 mass parts of propyleneglycol monomethylether
acetate, 332 mass parts of glycidyl methacrylate, and
6.6 mass parts of azobis isobutyro nitrile are added
20 into a separable flask, which is heated at 80°C for
6 hours in a nitrogen atmosphere to obtain a resin
solution.
Next, 168 mass parts of acrylic acid, 0.05 mass
parts of methoquinone, and 0.5 mass parts of triphenyl
25 phosphine are added to the obtained resin solution and
the solution is heated at 100°C for 24 hours while
blowing an air to obtain an acrylic acid added resin
58
solution.
Further, 186 mass parts of tetrahydrophthalic
anhydride is added to the obtained acrylic acid added
resin solution and the solution is heated at 70°C for
5 10 hours to obtain a resin A solution.
10
(Preparation of the photosensitive resin solution
A)
A negative photosensitive resin solution A is
prepared in the following composition:
Resin A
Photopolymerization monomer
dipentaerythritol hexaacrylate
Photopolymerization initiator
200 mass parts
100 mass parts
15 (manufactured by Ciba Specialty Chemicals
K.K., Irgacure 907) 100 mass parts
Solvent (propyleneglycol monomethylether acetate)
400 mass parts
A linear resin layer is formed in the center of
20 the rectangular pixel by the publicly known
photolithography method using the photosensitive resin
solution A and the photo mask as a pattern (opening) of
the linear resin layer. The height (thickness) of the
linear resin layer is set to 2.5 pm.
25 [Formation of the color pixel]
<>
The following organic pigments to be dispersed to
59
the color layers are used:
Red pigment: C. I. Pigment Red 254 ("Irga for Red
B-CF" manufactured by Ciba Specialty Chemicals K.K.),
C. I. Pigment Red 177 ("Cromophtal Red A2B"
5 manufactured by Ciba Specialty Chemicals K.K.)
10
Green pigment: C. I. Pigment Green 58
(manufactured by DIC Corporation), C. I. Pigment Yellow
150 ("Fanchon First Yellow Y-5688" manufactured by
Bayer AG)
Blue pigment: C. I. Pigment Blue 15 ("Ryanol Blue
ES" manufactured by Toyo Ink Co. Ltd.), C. I. Pigment
Violet 23 ("Variogen Violet 5890" manufactured by BASF
AG)
Using the above pigments, a dispersant of each
15 color of red, green, and blue is produced.
20
25
Red pigment: C. I. Pigment Red 254 18 mass parts
Red pigment: C. I. Pigment Red 177 2 mass parts
Acryl varnish (solid portion: 20% by weight)
108 mass parts
After the mixture of the above composition being
stirred uniformly, the mixture is dispersed by a sand
mill for 5 hours using a glass bead and filter by a
5-pm filter to produce a red pigment dispersed liquid.
Green pigment: C. I. Pigment Green 58
16 mass parts
5
10
60
Green pigment: C. I. Pigment Yellow 150
8 mass parts
Acryl varnish (solid portion: 20% by weight)
102 mass parts
A green pigment dispersant is produced from the
mixture of the above composition by using the same
production method as that of the red pigment
dispersant.
Blue pigment: C. I. Pigment Blue 15
50 mass parts
Blue pigment: C. I. Pigment Violet 23
2 mass parts
Dispersant ("SOLSPERSE 20000" manufactured by
15 AstroZeneca K.K.) 6 mass parts
Acryl varnish (solid portion: 20% by weight)
200 mass parts
A blue pigment dispersant is produced from the
mixture of the above composition by using the same
20 production method as that of the red pigment
dispersant.
<>
A color layer is formed by using a color pixel
forming color resist of the composition shown in Table
25 1 below.
Table 1
Color resist For red pixel For green pixel
Pigment dispersant Red dispersant Green dispersant
_____________ JE~E!_~ ___ ex __ ~~~-~~!:L ______________ 42.5 43.5
------------------------------------------------ ----------------------------------------------------
Acryl resin solution 6.7 5.7
Monomer 4.0 4.8
Photopolymerization initiator 3.4 2.8
Sensitizer 0.4 0.2
Organic solvent 43.0 43.0
Total 100 100
For blue pixel
Blue dispersant
35 --------------------------------------------------
14.2
5.6
2.0
0.2
43.0
100
f)
C1
f-'
~. ~.~ ...... ~."":""~,,__~·•,.tJUNR!li»i$11'1<"W*'I.tA,'"i WJ_j'i'!ig'-11"'4'''¥{!!\i!lifl'*ii.1*1$1i'W#¥t!'dif!l$1L -~lfJ¥.'Rilgii1"":
Documents