U.S. patent application number 11/948810 was filed with the patent office on 2008-03-27 for colored composition for color filter and display using color filters formed of the colored composition.
This patent application is currently assigned to HITACHI DISPLAYS, LTD.. Invention is credited to Kotaro ARAYA, Hiroshi SASAKI, Yasushi TOMIOKA.
Application Number | 20080073625 11/948810 |
Document ID | / |
Family ID | 34209035 |
Filed Date | 2008-03-27 |
United States Patent
Application |
20080073625 |
Kind Code |
A1 |
ARAYA; Kotaro ; et
al. |
March 27, 2008 |
Colored Composition for Color Filter and Display Using Color
Filters Formed of the Colored Composition
Abstract
An object of the present invention is to obtain color filters
having a high contrast, a high color purity and an improved
transmittance for blue color, and a display using the color
filters. In the present invention, there is used a colored
composition for color filter comprising at least one coloring
agent, a base polymer and at least one solvent, said base polymer
containing a polyamicacid whose light transmittance decreases by 2%
or less in the visible region (wavelength: 400 nm to 800 nm).
Inventors: |
ARAYA; Kotaro; (Hitachiota,
JP) ; SASAKI; Hiroshi; (Mito, JP) ; TOMIOKA;
Yasushi; (Hitachi, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
1999 AVENUE OF THE STARS
SUITE 1400
LOS ANGELES
CA
90067
US
|
Assignee: |
HITACHI DISPLAYS, LTD.
3300, Hayano
Mobara-shi
JP
|
Family ID: |
34209035 |
Appl. No.: |
11/948810 |
Filed: |
November 30, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10916875 |
Aug 11, 2004 |
7311953 |
|
|
11948810 |
Nov 30, 2007 |
|
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Current U.S.
Class: |
252/586 |
Current CPC
Class: |
Y10T 428/10 20150115;
C09K 2323/00 20200801; H01L 51/0078 20130101; Y10T 428/1036
20150115; C09K 2323/031 20200801; C09B 1/005 20130101; C09B 5/62
20130101; C09B 5/48 20130101; C09B 47/26 20130101; H01L 27/322
20130101; C09B 68/443 20130101; C09B 47/16 20130101; C09B 57/004
20130101; C09B 48/00 20130101; C09B 19/02 20130101; Y10T 428/1041
20150115; G02F 1/133514 20130101; C09B 7/02 20130101; C09B 57/04
20130101; C09K 2323/03 20200801 |
Class at
Publication: |
252/586 |
International
Class: |
G02B 5/23 20060101
G02B005/23 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2003 |
JP |
2003-209591 |
Claims
1. A colored composition for color filter comprising a base polymer
containing a polyamicacid whose light transmittance decreases by 2%
or less in the visible region (wavelength: 400 nm to 800 nm), at
least one coloring agent and at least one solvent.
2-6. (canceled)
Description
INCORPORATION BY REFERENCE
[0001] The present application claims priority from Japanese
application JP2003-209591 filed on Aug. 29, 2003, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a colored composition for
color filter which permits color display, and a display using color
filters formed of the colored composition.
[0003] As thin and light color displays, flat panel displays such
as liquid crystal displays, organic light emission displays and
plasma display panels have been put to practical use or are under
study for their practical application. For example, the liquid
crystal displays have already been put to practical use as devices
which fundamentally comprise two glass substrates and a liquid
crystal layer (a liquid crystal composition) held between them and
display letters, figures, drawings, pictures and the like owing to
electro-optical effects. As to the driving mode of the liquid
crystal displays, there are known TN (twisted nematic) method, STN
(supertwisted nematic) method, FLC (ferroelectric liquid crystal)
method, IPS (in-plane switching) method and the like. In the liquid
crystal displays, color display is carried out by passing light
transmitted by a liquid crystal layer at each pixel through a color
filter. Leading displays as such liquid crystal displays have been
changed to displays for desktop monitors from conventional displays
for notebook-sized personal computers, and the liquid crystal
displays are indispensably used in large-screen televisions.
Therefore, it is increasingly desirable to improve the liquid
crystal displays in performance characteristics and reduce their
production cost.
[0004] The organic light emission displays are so-called
self-luminous displays in which organic light-emitting layers are
driven by application of an electric current to emit light. As the
organic light emission displays, there are displays in which color
display is carried out by utilizing the emission of lights having a
plurality of colors, respectively, depending on materials for the
organic light-emitting layers themselves, and displays in which
color display is carried out by forming all pixels by the use of a
whitely luminescent material and passing light emitted by the
luminescent material through color filters provided for two or more
colors, respectively.
[0005] In displays in which color display is carried out by the use
of color filters, among the above-mentioned displays, color display
is carried out by utilizing color filters of two or more colors
(typically, the three primary colors, i.e., red (R), green (G) and
blue (B), or complementary colors for the three primary colors,
i.e., cyan (C), magenta (M) and yellow (Y)). Materials for such
color filters, production processes and properties for display of
the color filters, and the like are explained below.
[0006] Although the explanation is given herein by taking the case
of the color filters of the liquid crystal display, it applies also
to the color filters of other displays. The color filters used in
the liquid crystal display are composed of a striped or dotted
pattern having the above-mentioned colors, i.e., red, green and
blue. The color development in each of these color filters is due
to a component obtained by dissolving or dispersing a dye or
pigment as a coloring agent in an acrylic base polymer, and the
color filter is formed by applying the base polymer containing the
coloring agent on a glass substrate to a thickness of about 1
micron. It will be increasingly desirable to improve the color
filters in performance characteristics and reduce their production
cost.
[0007] As the coloring agent of the color filter, a dye dissolved
as molecules in the base polymer is superior from the viewpoint of
contrast. However, a liquid crystal composition is contaminated in
some cases with the dye owing to the diffusion of the dye itself
into liquid crystals from the color filter, and the contamination
causes nonuniform display. Moreover, a color change caused by the
photo-deterioration of the dye is fatal to the color filter, and a
pigment superior in light resistance is unavoidably used in current
color filters at the cost of contrast. JP-A-2002-309135 discloses a
technique for improving contrast by reducing the particle size of a
pigment. The technique disclosed in this reference, however,
involves a pigment atomization step and only increases the
production cost by increasing the number of steps.
[0008] JP-A-8-6242 discloses a technique for improving contrast by
using latent pigments as coloring agents. In the technique
disclosed in JP-A-8-6242, pigments are solubilized by molecular
modification in a step of dispersing them in a base polymer and
each pigment modified is restored to its original state by removing
a substituent used for the molecular modification, by light and
heat treatments after forming the base polymer. However, in the
case of the latent pigments, the dissolution of an acrylic resin as
base polymer in a solvent is not sufficient. Therefore,
JP-A-2002-72465 discloses a method for making up for a deficiency
in coloring density by a combination of latent pigments and
pigments.
[0009] As the base polymer, an acrylic resin is generally used
because of a combination of a pigment dispersion method and
photo-etching. Not only the acrylic resin but also other polymers
used as the base polymer can absorb light in the vicinity of 400 nm
near the ultraviolet region, in the visible region (wavelength: 400
nm to 800 nm) and are often colored yellow. This coloring becomes
more remarkable owing to heat treatment such as post-baking. This
phenomenon of coloring causes a decrease in transmittance for blue
color in a color filter and hence is a problem to be solved for
realizing the improvement of the color filter in performance
characteristics.
[0010] There are base polymers which are transparent in the visible
region, but such base polymers are often unusable from the
viewpoint of compatibility with a solvent, for example, they are
often unusable because their solubility in a solvent for them,
which is absolutely necessary in a pigment dispersion method, is
low. In addition, even if they are soluble in the solvent, this
solubility does not result in the reduction of coloring owing to
the influence of, for example, a sensitizer necessary to
photo-setting base polymers. Such a phenomenon of coloring
remarkably affects the color purity of the color filters with
respect also to a combination of the color filters and a backlight.
That is, it is expectable to improve the color purity by replacing
a cold-cathode tube with a light emitting diode (LED) as a
backlight, but this replacement cannot be expected to be very
effective when there is the phenomenon of coloring.
[0011] As described above, production processes of color filters
are broadly divided into a pigment dispersion method and a method
using dyes, according to the kind of a coloring agent. In practice,
the former, i.e., the pigment dispersion method is adopted for mass
production in view of, for example, light resistance. In the
pigment dispersion method, a photosensitive base polymer solution
containing a red pigment dispersed therein is applied on a
substrate having a black matrix formed thereon and is dried, after
which etching is conducted by the use of a photomask to form red
colored portions in the form of stripes. Subsequently, the same
procedure as above is repeated except for using a blue pigment and
then a green pigment, to produce color filters. Therefore, the
number of steps for the production is large.
[0012] As described above, the production of color filters by the
pigment dispersion method involves many steps. This is a cause for
an increase of the production cost. When a coming increase in the
size of a liquid crystal display is considered, an increase in the
cost of a production apparatus itself is possible. JP-A-11-305032
discloses a process for producing color filters by adopting an ink
jet method. This production process can be adopted only when dyes
are used as coloring agents, and it is still disadvantageous, for
example, in that a nozzle for ink jet is choked when pigments are
used.
[0013] A first object of the present invention is to solve the
problems in color filters described in the case of the above prior
arts, i.e., the contrast decrease, the color purity decrease, the
decrease in transmittance for blue color, and the like, and provide
a colored composition for color filter which has made it possible
to improve productivity in the production of color filters and
achieve the improvement of the color filters in performance
characteristics and the reduction of their production cost at the
same time. A second object of the present invention is to provide a
display having a high contrast, a high color purity and an
increased transmittance for blue color.
SUMMARY OF THE INVENTION
[0014] In order to achieve the above first object, the following
colored composition for color filter is used in the present
invention. That is, as a colored composition for color filter
comprising at least one coloring agent, a base polymer and at least
one solvent, there is used a colored composition for color filter
containing as the aforesaid base polymer a polyamicacid whose light
transmittance decreases by 2% or less in the visible region
(wavelength: 400 nm to 800 nm). In order to achieve the above
second object, a display is constructed by the use of color filters
formed of the above-mentioned colored composition for color filter,
in the present invention.
[0015] Needless to say, the present invention is not limited to the
constitutions described above and the constitutions described in
the embodiments described hereinafter, and various changes and
modifications may be made without departing from the technical idea
for the invention.
[0016] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a cross-sectional view schematically illustrating
the structure near one pixel of a liquid crystal panel constituting
a liquid crystal display as one example of the display of the
present invention.
[0018] FIG. 2 is a cross-sectional view taken along the line A-A'
of FIG. 1.
[0019] FIG. 3 is a perspective view schematically illustrating an
outline of the whole structure of one embodiment of a liquid
crystal display according to the present invention.
[0020] FIG. 4 is a cross-sectional view schematically illustrating
the structure near one pixel of an organic light emission panel
constituting an organic light emission display as another example
of the display of the present invention.
[0021] FIG. 5 is a plan view of the vicinity of one pixel which
illustrates one example of the structure of circuit of the display
of the present invention shown in FIG. 4.
[0022] FIG. 6 is a plan view schematically illustrating one example
of the arrangement of circuits in an organic light emission display
using the pixels shown in FIG. 5.
[0023] TFT - - - thin-film transistor, DL - - - drain line (picture
signal line), GL, GLA and GLC - - - gate lines (scanning signal
lines), AS - - - semiconductor layer, GT - - - gate electrode, SD1
- - - source electrode, SD2 - - - drain electrode, PX - - - pixel
electrode, CN - - - contact hole, SUB1 - - - first substrate (pixel
electrode substrate), SUB2 - - - second substrate (color filter
substrate), GI - - - gate insulating film, PSV1 and PSV2 - - -
insulating layers (insulating protective films), ITO1 - - -
transparent electroconductive film constituting a pixel electrode
PX, ORI1 - - - an alignment layer on the first substrate side, ORI2
- - - an alignment layer on the second substrate side, LC - - -
liquid crystal layer (liquid crystal composition layer), E - - -
electric field, BM - - - black matrix, FIL - - - color filter, ITO2
- - - counter electrode, PX - - - pixel, OLE - - - organic
light-emitting layer, CF - - - color filter, CD - - - first
electrode layer (cathode), AD - - - second electrode layer
(anode).
DETAILED DESCRIPTION OF THE INVENTION
[0024] Embodiments of the present invention are explained below in
detail. At first, the constituents of the colored composition for
color filter of the present invention, i.e., the base polymer, the
coloring agent(s) and the solvent(s) are explained. The explanation
is made with reference to the following structural formulas (3-1),
(3-2) and (3-3): ##STR1##
[0025] A polyamicacid of the structural formula (3-3) used as the
base polymer can be synthesized by ring-opening polyaddition of a
tetracarboxylic acid dianhydride of the structural formula (3-1)
and a diamine derivative of the structural formula (3-2). As the
polyamicacid that is transparent in the visible region (wavelength:
400 nm to 800 nm), there can be exemplified polyamicacids obtained
by the following combination: each of R.sub.2 in the structural
formula (3-1) and R.sub.3 in the structural formula (3-2) is a
linear aliphatic group or a cyclic aliphatic group.
[0026] The transparency of the base polymer in the visible region
(wavelength: 400 nm to 800 nm) is affected by the thickness of the
base polymer, and the transmittance of the base polymer used in a
color filter has to be 98% or more at a thickness of the base
polymer of about 1 .mu.m (namely, the decrease of the light
transmittance is 2% or less). The effects of employment of the
polyamicacid as the base polymer are as follows. Not only the
transparency in the visible region but also the interaction of the
polyamicacid with the amino group or the like of the coloring agent
can be expected. Therefore, the employment is effective in
preventing the coloring agent from diffusing into liquid crystals.
Moreover, the employment is effective also in preventing the
coloring agent from diffusing and crystallizing to increase in
particle size and lower contrast.
[0027] As the basis for the effects of the above-mentioned
condition that the decrease of the transmittance of the base
polymer is 2% or less at a thickness of the base polymer of about 1
Mm in the visible region (wavelength: 400 nm to 800 nm), the
following data can be presented.
[0028] The transmittance in the visible region (wavelength: 400 nm
to 800 nm) of acrylic resins used in conventional color filters is
changed by about 5% to about 10%. In particular, the transmittance
at 400 nm is about 90%. This fact means that the transmittance for
blue color is decreased. Specifically, the above change of the
transmittance corresponds to a 2% to 3% loss of the light
transmittance of a liquid crystal display. Therefore, limiting the
decrease of the transmittance to 2% or less in the visible region
improves the light transmittance of the liquid crystal display and
is finally effective in reducing the electric power
consumption.
[0029] The tetracarboxylic acid dianhydride used in the present
embodiment includes, for example, tetracarboxylic acid dianhydrides
of chain alkanes, such as butanetetracarboxylic acid dianhydride,
n-hexanetetracarboxylic acid dianhydride, etc.; and alicyclic
tetracarboxylic acid dianhydrides such as
cyclopentanetetracarboxylic acid dianhydride,
cyclobutanetetracarboxylic acid dianhydride,
bicyclo[2,2,2]octanetetracarboxylic acid dianhydride,
1,4-cyclohexanedicarboxylic acid, etc. In addition, structures
containing an aromatic ring or two or more non-conjugated aromatic
rings are also effective. Tetracarboxylic acid dianhydrides having
such a structure include, for example, methylpyromellitic
dianhydride, 3,3',4,4'-diphenylmethanetetracarboxylic acid
dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic acid
dianhydride and 3,3',4,4'-diphenyl sulfone tetracarboxylic acid
dianhydride. Fluorine-substituted derivatives of these compounds
are also effective.
[0030] The diamine derivative used in the present invention
includes, for example, chain alkane diamine derivatives such as
1,6-diaminohexane, 1,8-diaminooctane, 1,10-diaminodecane,
1,12-diaminododecane, etc.; and alicyclic diamine derivatives such
as diaminocyclobutane, diaminocyclopentane, diaminocyclohexane,
diaminodecalin, diaminobicyclo[2,2,2]octane, etc. In addition,
structures containing an aromatic ring or two or more
non-conjugated aromatic rings are also effective. Diamine
derivatives having such a structure include, for example,
4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether,
4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane,
4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane,
4,4'-diaminodiphenyl sulfone and 3,3'-diaminodiphenyl sulfone.
[0031] Although the tetracarboxylic acid dianhydride and diamine
derivative used for synthesizing the polyamicacid which is
transparent in the visible region (wavelength: 400 nm to 800 nm)
are explained above by giving specific examples, they are not
limited to the above-exemplified tetracarboxylic acid dianhydrides
and diamine derivatives so long as the polyamicacid has a
transmittance of 98% or more in the visible region (wavelength: 400
nm to 800 nm).
[0032] As the coloring agent(s) used in the present invention,
there can be exemplified pigment derivatives having a structure
represented by the following general formula (I):
A(B).sub.x(C).sub.y (I) wherein x is a number of 0 to 4; Y is a
number of 0 to 8; A is a coloring group derived from quinacridone,
anthraquinone, dianthraquinone, perylene, indigo, quinophthalone,
indanthrone, isoindolinone, isoindoline, dioxazine or
diketopyrrolopyrrole; B is a substituent bonded to a nitrogen atom
contained in A, by the formation of a carbamate, namely, B is
represented by the following structural formula (1): ##STR2##
wherein R.sub.1 is selected from alkyl groups and substituted aryl
groups (as to the substituent for B, there is a detailed
description in Protective Groups in Organic Synthesis, John Wiley
& Sons, p. 223 (1981)); and C is a side chain group bonded to
an aromatic ring contained in A and is selected from hydrogen atom,
halogen atoms (e.g. chlorine atom), cyano group, alkyl groups
(--(CH.sub.2).sub.nCH.sub.3 wherein n is an integer of 0 to 20),
alkoxyl groups (--O--(CH.sub.2).sub.mCH.sub.3 wherein m is an
integer of 0 to 20) and oxymethylene groups
(--O--(CH.sub.2--O).sub.kCH.sub.3 wherein k is an integer of 0 to
20), and of these, the alkyl groups and the alkoxyl groups may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like.
[0033] Such introduction of a side chain group such as C makes it
possible to increase the solubility of the coloring agent. In
addition, by introducing a functional group for polymerization and
addition, such as a vinyl group, epoxy group or the like into the
alkyl group or alkoxyl group selected as the side chain group, the
coloring agent can be prevented from diffusing as molecules into
liquid crystals. This introduction is effective also in preventing
the coloring agent from diffusing and crystallizing to increase in
particle size and lower contrast.
[0034] As an example of the coloring agent used in the present
embodiment, a diketopyrrolopyrrole derivative is explained below in
detail with reference to the structural formulas (4-1), (4-2) and
(4-3): ##STR3##
[0035] The diketopyrrolopyrrole derivative of the structural
formula (4-3) can easily be synthesized by the reaction of a
diketopyrrolopyrrole (Pigment Red 254) of the structural formula
(4-1) with di-t-butyl carbonate of the structural formula
(4-2).
[0036] As the coloring group of the coloring agent used in the
present embodiment, an indigo represented by the following
structural formula (5) may be used besides the above-mentioned
diketopyrrolopyrrole: ##STR4## wherein each of R.sub.1, R.sub.2,
R.sub.3 and R.sub.4 is a side chain group bonded to each aromatic
ring and is selected from hydrogen atom, halogen atoms (e.g.
chlorine atom), cyano group, alkyl groups
(--(CH.sub.2).sub.nCH.sub.3 wherein n is an integer of 0 to 20),
alkoxyl groups (--O--(CH.sub.2).sub.mCH.sub.3 wherein m is an
integer of 0 to 20) and oxymethylene groups
(--O--(CH.sub.2--O).sub.kCH.sub.3 wherein k is an integer of 0 to
20), and of these, the alkyl groups and the alkoxyl groups may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like.
[0037] As the coloring group of the coloring agent used in the
present embodiment, a perylene derivative represented by the
following structural formula (6) may be used: ##STR5##
[0038] As the coloring group of the coloring agent used in the
present embodiment, a quinacridone represented by the following
structural formula (7) may be used: ##STR6## wherein each of
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is a side chain group bonded
to each aromatic ring and is selected from hydrogen atom, halogen
atoms (e.g. chlorine atom), cyano group, alkyl groups
(--(CH.sub.2).sub.nCH.sub.3 wherein n is an integer of 0 to 20),
alkoxyl groups (--O--(CH.sub.2).sub.mCH.sub.3 wherein m is an
integer of 0 to 20) and oxymethylene groups
(--O--(CH.sub.2--O).sub.kCH.sub.3 wherein k is an integer of 0 to
20), and of these, the alkyl groups and the alkoxyl groups may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like.
[0039] As the coloring group of the coloring agent used in the
present embodiment, an indanthrone represented by the following
structural formula (8) may be used: ##STR7## wherein each of
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is a side chain group bonded
to each aromatic ring and is selected from hydrogen atom, halogen
atoms (e.g. chlorine atom), cyano group, alkyl groups
(--(CH.sub.2).sub.nCH.sub.3 wherein n is an integer of 0 to 20),
alkoxyl groups (--O--(CH.sub.2).sub.mCH.sub.3 wherein m is an
integer of 0 to 20) and oxymethylene groups
(--O--CH.sub.2--O).sub.kCH.sub.3 wherein k is an integer of 0 to
20), and of these, the alkyl groups and the alkoxyl groups may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like.
[0040] As the coloring group of the coloring agent used in the
present embodiment, a dianthraquinone represented by the following
structural formula (9) may be used: ##STR8## wherein each of
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is a side chain group bonded
to each aromatic ring and is selected from hydrogen atom, halogen
atoms (e.g. chlorine atom), cyano group, alkyl groups
(--(CH.sub.2).sub.nCH.sub.3 wherein n is an integer of 0 to 20),
alkoxyl groups (--O--(CH.sub.2).sub.nCH.sub.3 wherein m is an
integer of 0 to 20) and oxymethylene groups
(--O--(CH.sub.2--O).sub.kCH.sub.3 wherein k is an integer of 0 to
20), and of these, the alkyl groups and the alkoxyl groups may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like.
[0041] As the coloring group of the coloring agent used in the
present embodiment, a dioxazine represented by the following
structural formula (10) may be used: ##STR9## wherein each of
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is a side chain group bonded
to each aromatic ring and is selected from hydrogen atom, halogen
atoms (e.g. chlorine atom), cyano group, alkyl groups
(--(CH.sub.2).sub.nCH.sub.3 wherein n is an integer of 0 to 20),
alkoxyl groups (--O--(CH.sub.2).sub.mCH.sub.3 wherein m is an
integer of 0 to 20) and oxymethylene groups
(--O--(CH.sub.2--O).sub.nCH.sub.3 wherein k is an integer of 0 to
20), and of these, the alkyl groups and the alkoxyl groups may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like.
[0042] As the coloring group of the coloring agent used in the
present embodiment, an isoindoline represented by the following
structural formula (11) may be used: ##STR10## wherein each of
R.sub.1 and R.sub.2 is a side chain group bonded to the aromatic
ring and is selected from hydrogen atom, halogen atoms (e.g.
chlorine atom), cyano group, alkyl groups (--(CH.sub.2).sub.nCH,
wherein n is an integer of 0 to 20), alkoxyl groups
(--O--(CH.sub.2).sub.nCH.sub.3 wherein m is an integer of 0 to 20)
and oxymethylene groups (--O--(CH.sub.2--O).sub.kCH.sub.3 wherein k
is an integer of 0 to 20), and of these, the alkyl groups and the
alkoxyl groups may contain a functional group for polymerization
and addition, such as a vinyl group, epoxy group or the like.
[0043] As the coloring group of the coloring agent used in the
present embodiment, a dioxazine derivative represented by the
following structural formula (12) may be used: ##STR11## wherein
each of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is a side chain group
bonded to each aromatic ring and is selected from hydrogen atom,
halogen atoms (e.g. chlorine atom), cyano group, alkyl groups
(--(CH.sub.2).sub.nCH.sub.3 wherein n is an integer of 0 to 20),
alkoxyl groups (--O--(CH.sub.2).sub.mCH.sub.3 wherein m is an
integer of 0 to 20) and oxymethylene groups
(--O--(CH.sub.2--O).sub.kCH.sub.3 wherein k is an integer of 0 to
20), and of these, the alkyl groups and the alkoxyl groups may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like.
[0044] As the coloring agent(s) used in the present embodiment,
there can be exemplified phthalocyanine derivatives having a
structure represented by the following general formula (II):
Pc(M)(C).sub.y(D).sub.z (II) wherein y is a number of 0 to 16; z is
a number of 0 to 2; Pc is phthalocyanine; M is H.sub.2, Ni, Zn, Cu,
Fe, V, Ti, Si or Ge; C is a side chain group bonded to an aromatic
ring contained in A and is a hydrogen atom, a chlorine atom, an
alkyl group (--(CH.sub.2).sub.nCH.sub.3 wherein n is a number of 0
to 20), an alkoxyl group (--O--(CH.sub.2).sub.mCH.sub.3 wherein m
is a number of 0 to 20), an oxymethylene group
(--O--(CH.sub.2--O).sub.kCH.sub.3 wherein k is a number of 0 to 20)
or an alkoxysilane residue (--Si(--O--
(CH.sub.2).sub.mCH.sub.3).sub.3 wherein m is an integer of 0 to
20), and of these, the alkyl group and the alkoxyl group may
contain a functional group for polymerization and addition, such as
a vinyl group, epoxy group or the like; and D is a substituent
bonded to M and having an oxygen atom as a spacer, namely, D is
represented by the following structural formula (2): ##STR12##
[0045] As the coloring agent of the general formula (II) used in
the present embodiment, a phthalocyanine derivative represented by
the following structural formula (13) may be used: ##STR13##
wherein M is H.sub.2, Ni, Zn, Cu, Fe, V, Si or Ge; and D is a
substituent bonded to M and having an oxygen atom as a spacer,
namely, D is represented by the following structural formula (2):
##STR14##
[0046] As the coloring agent used in the present embodiment, a
phthalocyanine derivative represented by the following structural
formula (14) may be used: ##STR15## wherein M is H.sub.2, Ni, Zn,
Cu, Fe, V, Si or Ge; and D is a substituent bonded to M and having
an oxygen atom as a spacer, namely, D is represented by the
following structural formula (2): ##STR16##
[0047] As the coloring agent used in the present embodiment, a
phthalocyanine derivative represented by the following structural
formula (15) may be used: ##STR17## wherein M is H.sub.2, Ni, Zn,
Cu, Fe, V, Si or Ge; each of R.sub.1, R.sub.2, R.sub.3 and R.sub.4
is a side chain group bonded to each aromatic ring and is a
hydrogen atom, a chlorine atom, an alkyl group
(--(CH.sub.2).sub.nCH.sub.3 wherein n is a number of 0 to 20), an
alkoxyl group (--O--(CH.sub.2).sub.mCH.sub.3 wherein m is a number
of 0 to 20), an oxymethylene group
(--O--(CH.sub.2--O).sub.nCH.sub.3 wherein k is a number of 0 to 20)
or an alkoxysilane residue
(--Si(--O--(CH.sub.2).sub.nCH.sub.3).sub.3 wherein m is an integer
of 0 to 20), and of these, the alkyl group and the alkoxyl group
may contain a functional group for polymerization and addition,
such as a vinyl group, epoxy group or the like; and D is a
substituent bonded to M and having an oxygen atom as a spacer,
namely, D is represented by the following structural formula
(2):
[0048] Although the coloring agent(s) is explained above by giving
specific examples, the coloring agent(s) is not particularly
limited to the above-exemplified coloring agents so long as it is a
pigment derivative soluble in a solvent for the polyamicacid. This
is explained with reference to the following structural formula
(2). ##STR18##
[0049] As a solvent(s) for the base polymer and coloring agent used
in the present embodiment, there can be used solvents having a
solubility parameter of 10 (cal/cm.sup.3).sup.0.5 or more, such as
N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl
sulfoxide, sulfolane, .gamma.-butyrolactone, cresol, phenol,
cyclohexanone, dioxane, tetrahydrofuran, ethylene glycol monobutyl
ether, ethylene glycol monobutyl ether acetate, acetophenone, etc.
In addition, solvents having a solubility parameter of 11
(cal/cm.sup.3).sup.0.5 or more are more preferable from the
viewpoint of the solubility of the base polymer and the coloring
agent(s). The above-exemplified solvents may be used singly or in
combination.
[0050] Thus, a solvent having a solubility parameter of 10
(cal/cm.sup.3).sup.0.5 or more has to be used for dissolving the
polyamicacid as base polymer, and the selection of such a solvent
having a solubility parameter of 10 (cal/cm.sup.3).sup.0.5 or more,
preferably 11 (cal/cm.sup.3).sup.0.5 or more, is preferable for
dissolving the above-mentioned coloring agent(s) in an amount of 5
wt % or more and demands primary consideration in the production of
color filters.
[0051] Specific embodiments of the colored composition for color
filter of the present invention, a process for production of color
filters, and a display using the color filters are explained below
in detail.
[Embodiment of a Colored Composition for Color Filter--1]
[0052] The colored composition for color filter according to this
embodiment is composed of the following base polymer, coloring
agent and solvent.
[0053] Base polymer: a polyamicacid of the structural formula (3-3)
in which R.sub.2 is cyclobutane and R.sub.3 is a hexyl group [10 wt
%].
[0054] Coloring agent: a diketopyrrolopyrrole derivative of the
structural formula (4-3) in which each of R.sub.1 and R.sub.2 is a
hydrogen atom and R.sub.3 is a cyano group [5 wt %].
[0055] Solvent: N-methylpyrrolidone [85 wt %].
[0056] A cyclobutanetetracarboxylic acid dianhydride of the
structural formula (3-1) in which R.sub.2 is cyclobutane and a
hexyldiamine of the structural formula (3-2) in which R.sub.3 is a
hexyl group were subjected to ring-opening polyaddition in 60 g of
N-methylpyrrolidone to obtain 10 g of the polyamicacid. After the
synthesis, the reaction solution was filtered through Millipore
Filter of 0.5 .mu.m. To the filtrate were added 5 g of the
diketopyrrolopyrrole derivative and then 25 g of
N-methylpyrrolidone to obtain a red colored composition for color
filter. The employment of N-methylpyrrolidone made it possible to
dissolve the coloring agent to such an extent that a sufficient
coloring density could be attained.
[Embodiment of a Colored Composition for Color Filter--2]
[0057] The colored composition for color filter according to this
embodiment is composed of the following base polymer, coloring
agents and solvents.
[0058] Base polymer: a polyamicacid of the structural formula (3-3)
in which R.sub.2 is cyclobutane and R.sub.3 is a hexyl group [10 wt
%]
[0059] Coloring agent 1: a phthalocyanine derivative of the
structural formula (14) in which M is copper and D is absent [4.5
wt %].
[0060] Coloring agent 2: a phthalocyanine derivative of the
structural formula (14) in which M is silicon and D is an ethoxy
group [0.5 wt %].
[0061] Solvent 1: N-methylpyrrolidone [44 wt %].
[0062] Solvent 2: .gamma.-butyrolactone [41 wt %]
[0063] A cyclobutanetetracarboxylic acid dianhydride of the
structural formula (3-1) in which R.sub.2 is cyclobutane and a
hexyldiamine of the structural formula (3-2) in which R.sub.3 is a
hexyl group were subjected to ring-opening polyaddition in a mixed
solvent of 24 g of N-methylpyrrolidone and 40 g of
.gamma.-butyrolactone to obtain 10 g of the polyamicacid. After the
synthesis, the reaction solution was filtered through Millipore
Filter of 0.5 .mu.m. To the filtrate were added 5 g each of the
phthalocyanine derivatives as the coloring agent 1 and the coloring
agent 2 and then 20 g of N-methylpyrrolidone to obtain a green
colored composition for color filter. Owing to the effect of the
sufficient dissolution of the coloring agent 1 in the solvent for
the polyamicacid, the dispersibility of the coloring agent 2 was
improved.
[Embodiment of a Colored Composition for Color Filter--3]
[0064] The colored composition for color filter according to this
embodiment is composed of the following base polymer, coloring
agents and solvent.
[0065] Base polymer: a polyamicacid of the structural formula (3-3)
in which R.sub.2 is cyclobutane and R.sub.3 is a hexyl group [10 wt
%].
[0066] Coloring agent 1: a phthalocyanine derivative of the
structural formula (13) in which M is copper and D is absent [4.5
wt %].
[0067] Coloring agent 2: a phthalocyanine derivative of the
structural formula (15) in which each of R.sub.1, R.sub.2 and
R.sub.3 is a hydrogen atom, R.sub.4 is a propyl group, M is copper
and D is absent [0.5 wt %].
[0068] Solvent 1: N-methylpyrrolidone [84 wt %].
[0069] A cyclobutanetetracarboxylic acid dianhydride of the
structural formula (3-1) in which R.sub.2 is cyclobutane and a
hexyldiamine of the structural formula (3-2) in which R.sub.3 is a
hexyl group were subjected to ring-opening polyaddition in a mixed
solvent of 24 g of N-methylpyrrolidone and 40 g of
.gamma.-butyrolactone to obtain 10 g of the polyamicacid. After the
synthesis, the reaction solution was filtered through Millipore
Filter of 0.5 .mu.m. To the filtrate were added 5 g each of the
phthalocyanine derivatives as the coloring agent 1 and the coloring
agent 2 and then 20 g of N-methylpyrrolidone to obtain a blue
colored composition for color filter. It was confirmed that owing
to the effect of the sufficient dissolution of the coloring agent 1
in the solvent for the polyamicacid, the dispersibility of the
coloring agent 2 had been improved.
[Embodiment of a Process for Production of Color Filters--1]
[0070] In the process for production of color filters according to
this embodiment, there was used a 1.1-mm-thick transparent glass
substrate with polished surfaces having substrate sizes of 320 mm
(long side).times.240 mm (short side) and a display portion of
15-inch size (a nominal width across corners). After a black matrix
was formed on the glass substrate, the red colored composition for
color filter described in "Embodiment of a colored composition for
color filter--1" was applied thereon by screen printing. After the
application, the red colored composition for color filter was dried
and then heated at 200.degree. C. to convert the polyamicacid to
polyimide. In this case, the yellow color of the composition after
the application and drying was changed to red color by the heating.
Thereafter, the same procedure as above was repeated except for
using each of the green colored composition and the blue colored
composition described in "Embodiment of a colored composition for
color filter--2" and "Embodiment of a colored composition for color
filter--3", respectively.
[0071] Thus, owing to the employment of the polyamicacid, a
conventional vacuum irradiator for photo-etching became
unnecessary, so that a marked reduction of the production cost has
become possible.
[Embodiment of a Process for Production of Color Filters--2]
[0072] In the process for production of color filters according to
this embodiment, there was used a 1.1-mm-thick transparent glass
substrate with polished surfaces having substrate sizes of 320 mm
(long side).times.240 mm (short side) and a display portion of
15-inch size (a nominal width across corners). After a black matrix
was formed on the glass substrate, the red, green and blue colored
compositions for color filter described in "Embodiment of a colored
composition for color filter--1", "Embodiment of a colored
composition for color filter--2" and "Embodiment of a colored
composition for color filter--3", respectively, were pored onto and
applied on the corresponding portions of the black matrix at the
same time by ink jet printing. After the application, the
compositions were dried and then heated at 200.degree. C. to
convert the polyamicacid to polyimide.
[0073] Thus, owing to the employment of the polyamicacid, there
could be obtained the colored compositions for color filter which
were excellent in the solubility and dispersibility of their
components, and it has become possible to conduct printing without
clogging which tends to be caused in ink jet printing. A
conventional vacuum irradiator for photo-etching became
unnecessary, so that a marked reduction of the production cost has
become possible. Moreover, since the red, green and blue color
filters could be formed at the same time, the process could be
greatly shortened.
[Embodiment of a Process for Production of Color Filters--3]
[0074] In the process for production of color filters according to
this embodiment, a pixel electrode substrate was used. There was
used a 1.1-mm-thick transparent glass substrate with polished
surfaces having pixel electrode substrate sizes of 320 mm (long
side).times.240 mm (short side) and a display portion of 15-inch
size (a nominal width across corners). Common electrodes, signal
electrodes, pixel electrodes and the like were formed on the glass
substrate to obtain the pixel electrode substrate.
[0075] The red, green and blue colored compositions for color
filter described in "Embodiment of a colored composition for color
filter--1", "Embodiment of a colored composition for color
filter--2" and "Embodiment of a colored composition for color
filter--3", respectively, were pored onto and applied on the
corresponding pixels of the pixel electrode substrate at the same
time by ink jet printing. After the application, the compositions
were dried and then heated at 200.degree. C. to convert the
polyamicacid to polyimide.
[0076] Thus, owing to the employment of the polyamicacid, there
could be obtained the colored compositions for color filter which
were excellent in the solubility and dispersibility of their
components, and it has become possible to conduct printing without
clogging which tends to be caused in ink jet printing. A
conventional vacuum irradiator for photo-etching became
unnecessary, so that a marked reduction of the production cost has
become possible. Moreover, since the red, green and blue color
filters could be formed at the same time, the process could be
greatly shortened.
[0077] Furthermore, since the color filters were directly formed on
the pixel electrode substrate to obtain a lower substrate, the
alignment of the lower substrate with an upper substrate becomes
easy.
[Embodiment of a Display--1]
[0078] In the liquid crystal display according to this embodiment,
the color filter substrate SUB 2 described in "Embodiment of a
process for production of color filters--2" was used as a first
substrate (an upper substrate) and the pixel electrode substrate
SUB1 described below was used as a second substrate (a lower
substrate). There was used a 1.1-mm-thick transparent glass
substrate with polished surfaces having pixel electrode substrate
SUB1 sizes of 320 mm (long side).times.240 mm (short side) and a
display portion of 15-inch size (a nominal width across corners).
Common electrodes, signal electrodes, pixel electrodes and the like
were formed on the glass substrate, and an alignment layer was
formed on the outermost surface of the thus treated glass
substrate. The same alignment layer as above was formed on the
color filter substrate described in "Embodiment of a process for
production of color filters--2". A polyimide was used as the
alignment layers. The polyimide was applied with a printer so that
its thickness after baking might be approximately 0.07 .mu.m to 0.1
.mu.m. Then, the surfaces of the alignment layers were subjected to
alignment treatment for orientation of liquid crystals. The
alignment treatment was carried out with a rubbing machine by using
rayon buff on rubbing rolls.
[0079] The upper and lower substrates were adhered to each other as
follows. A proper amount of polymer beads were mixed with a sealing
agent (an epoxy resin) and the resulting mixture was printed on the
substrates by the use of a seal mask. Then, the sealing agent was
tentatively cured to combine the upper and lower substrates.
Thereafter, the sealing agent was cured while pressing the two
substrates by the use of a press. Inside the panel surface,
spherical polymer beads were held between the substrates so that
the size of the gap between them for a liquid crystal layer might
be 6.0 .mu.m when liquid crystals were enclosed in the gap. The
angle of rubbing for the alignment layers was 45.degree. to the
short side of each substrate, and the direction of rubbing on the
upper substrate was perpendicular to that on the lower substrate.
The width of an opening for injecting liquid crystals was 30 mm.
Subsequently, liquid crystals were injected into the gap with a
liquid crystal injector to produce a liquid crystal display. In
this case, columnar spacers fixed on the substrate surfaces by
photolithography may also be used in place of the beads. This
applies also to the following embodiments.
[0080] Although a conventional cold-cathode tube was used as a
backlight in the present embodiment, the contrast was improved by
about 10% as compared with conventional liquid crystal displays, in
spite of the cold-cathode tube because the transparent polyamicacid
had been used as a base polymer in the color filter substrate. In
addition, the transmittance at a wavelength of 400 nm was improved
by 5% or more. An embodiment of a liquid crystal display as an
example of the display of the present invention is explained
below.
[0081] FIG. 1 is a cross-sectional view schematically illustrating
the structure near one pixel of a liquid crystal panel constituting
the liquid crystal display as an example of the display of the
present invention. FIG. 2 is a cross-sectional view taken along the
line A-A' of FIG. 1. The reference symbols are as follows: TFT
denotes a thin-film transistor, DL a drain line (a picture signal
line), CL, GLA and GLC gate lines (scanning signal lines), AS a
semiconductor layer, GT a gate electrode, SD1 a source electrode,
SD2 a drain electrode, PX a pixel electrode, and CN a contact
hole.
[0082] In addition, GI denotes a gate insulating film, PSV1 and
PSV2 insulating protective films, ITO1 a transparent
electroconductive film constituting a pixel electrode PX, ORI1 an
alignment layer on the first substrate side, i.e., the pixel
electrode substrate SUB1 side, ORI2 an alignment layer on the
second substrate side, i.e., the color filter substrate SUB2 side,
LC a liquid crystal layer (liquid crystal composition layer), and E
an electric field. BM denotes a black matrix, FIL a color filter,
and ITO2 a counter electrode. The reference symbols marked with
denote the components of an adjacent pixel. The parenthesized
symbols (0, d1 and g1) denote constituent layers, namely, members
accompanied with the same parenthesized symbol are formed of the
same constituent layer.
[0083] In the liquid crystal display panel according to the present
embodiment, when a thin-film transistor TFT for a pixel selected by
a scanning line, i.e., a gate line and a drain line as signal line
or data line assumes an "on" state, an electric field E is formed
between the pixel electrode PX (ITO1) connected to the source
electrode SD1 and the counter electrode ITO2 on the color filter
substrate SUB2 side. Owing to this electric field, molecules of a
liquid crystal composition constituting the liquid crystal layer LC
stand up, and light for illumination introduced from the deflector
POLL of the first substrate SUB1 comes out of the deflector POL2 of
the second substrate SUB2.
[0084] FIG. 3 is a perspective view schematically illustrating an
outline of the whole structure of one embodiment of a liquid
crystal display according to the present invention. A tape carrier
package TCP1 mounted with scanning line driving circuit (gate line
driving circuit or gate driving circuit) chips GDR is connected to
one side of one of the substrates (usually the first substrate) of
a liquid crystal display panel PNL. A tape carrier package TCP2
mounted with signal line driving circuit (drain line driving
circuit, drain driving circuit or data line driving circuit) chips
GDR is connected to another side adjacent to the above-mentioned
side.
[0085] The tape carrier package TCP2 is connected to the tape
carrier package TCP1 on the gate side by a flexible printed circuit
board FPC and is connected also to an interface circuit board (not
shown). The individual driving circuit chips may be directly
mounted on the corresponding side of the first substrate in place
of the tape carrier package TCP1 and the tape carrier package
TCP2.
[0086] A backlight composed of a light-guiding plate GLB and a
linear lamp CFL such as a cold-cathode fluorescent lamp (a
cold-cathode tube) is set at the back of the liquid crystal display
panel PNL. The linear lamp CFL is driven by an inverter INV. The
liquid crystal display panel PNL and the backlight are held by an
upper case (not shown) and a lower case (not shown) to be made into
a product as a so-called liquid crystal display module, i.e., a
liquid crystal display. A plurality of cold-cathode tubes may be
directly set at the back of the liquid crystal display panel as a
backlight without using the light-guiding plate GLB.
[Embodiment of a Display--2]
[0087] This embodiment is an organic light emission display. The
same color filter substrate as described as a second substrate in
"Embodiment of a display--1" was used as an upper substrate and the
following organic light-emitting pixel substrate as a second
substrate was used as a lower substrate. There was used a
1.1-mm-thick transparent glass substrate with polished surfaces
having organic light-emitting pixel substrate sizes of 320 mm (long
side).times.240 mm (short side) and a display portion of 15-inch
size (a nominal width across corners). Common electrodes, signal
electrodes, white organic light-emitting pixels and the like were
formed on the glass substrate. The upper and lower substrates were
adhered to each other as follows. A proper amount of polymer beads
were mixed with a sealing agent (an epoxy resin) and the resulting
mixture was printed on the substrates by the use of a seal mask.
Then, the sealing agent was tentatively cured to combine the upper
and lower substrates.
[0088] FIG. 4 is a cross-sectional view illustrating the structure
near one pixel of an organic light emission panel constituting an
organic light emission display as another example of the display of
the present invention. In this example, a thin-film transistor
composed of a semiconductor layer PSI, a scanning line (i.e. a gate
line) GL insulated with an insulating layer IS or PSV, and a
source* drain electrode SD is formed on the first substrate, i.e.,
the organic light-emitting pixel substrate. A first electrode layer
(in this case, a cathode) CD formed of a thin metal film is
connected to the source* drain electrode SD, and an organic
light-emitting layer OLE capable of emitting white light is formed
over the first electrode CD. In addition, a second electrode layer
(in this case, an anode) AD formed of a transparent
electroconductive film such as ITO is formed on the organic
light-emitting layer OLE.
[0089] On the other hand, the second substrate, i.e., the color
filter substrate SUB2 is made of transparent glass and has red,
green and blue color filters CF formed in its inner surface which
are divided according to a black matrix BM and are arranged so as
to correspond to pixels, respectively, of the organic
light-emitting layer present in the first substrate. In the organic
light emission display, emitted light LW comes out in the direction
of the second substrate SUB2, namely, light LW emitted by the
organic light-emitting layer OLE comes out toward the second
substrate SUB2 from the second electrode layer AD. This emitted
light LW is converted to light LCF of a predetermined color by each
of the above-mentioned color filters CF of the present invention
formed in the inner surface of the second substrate SUB2, and then
comes out toward an observer.
[0090] FIG. 5 is a plan view of the vicinity of one pixel which
illustrates one example of the structure of circuit of the display
of the present invention shown in FIG. 4. The pixel is formed in a
region surrounded by a gate line GL and a drain line DL.
[0091] In this display, an opening DE for accommodating an organic
light-emitting layer OLE need not be formed in a portion other than
a pixel circuit having a thin-film transistor and various wirings,
so that pixels having a high aperture ratio and a large area can be
formed. Therefore, a display having a collectively bright picture
can be obtained. Moreover, there can be obtained an organic light
emission display that consumes a lower electric power and has a
longer life though it has the same brightness.
[0092] FIG. 6 is a plan view schematically illustrating one example
of the arrangement of circuits in an organic light emission display
using the pixels shown in FIG. 5. Each pixel is formed in a portion
surrounded by a gate line GL driven by a scanning driving circuit
GDR and a drain line (a data line) DL driven by a signal line
driving circuit DDR, and the pixels are arranged in the form of a
matrix. Current-supplying lines CSL branch off from a
current-supplying bus line CSB outside a display region AR and are
set for the pixels, respectively, in parallel with the drain lines
DL.
[0093] The symbol PAD denotes a pad for supplying signals and
electric power to the organic light emission display from the
outside through a flexible printed circuit board or the like. The
symbol PAD1 denotes a pad for data driving circuit, the symbol PAD2
a pad for scanning driving circuit, and the symbol PAD2 a pad for
current supply. Also in each of these pads, an opening is formed in
the insulating layer or protective film of the pad.
[0094] In the organic light emission display, since the transparent
polyamicacid was thus used as a base polymer for the color filters
formed in the color filter substrate SUB2, the contrast was
improved by 5% or more as compared with conventional organic light
emission displays.
[Embodiment of a Display--3]
[0095] This embodiment is a liquid crystal display. The same color
filter substrate as described in "Embodiment of a display--1" was
used as an upper substrate and the pixel electrode substrate
described below was used as a lower substrate (pixel electrode
substrate). There was used a 1.1-mm-thick transparent glass
substrate with polished surfaces having pixel electrode substrate
sizes of 320 mm (long side).times.240 mm (short side) and a display
portion of 15-inch size (a nominal width across corners). Common
electrodes, signal electrodes, pixel electrodes and the like were
formed on the glass substrate, and an alignment layer was formed on
the outermost surface of the thus treated glass substrate. The same
alignment layer was formed on the same color filter substrate as
described in "Embodiment of a display--1". A polyimide was used as
the alignment layers. The polyimide was applied with a printer so
that its thickness after baking might be approximately 0.07 .mu.m
to 0.1 .mu.m. Then, the surfaces of the alignment layers were
subjected to alignment treatment for orientation of liquid
crystals. The alignment treatment was carried out with a rubbing
machine by using rayon buff on rubbing rolls.
[0096] The upper and lower substrates were adhered to each other as
follows. A proper amount of polymer beads were mixed with a sealing
agent (an epoxy resin) and the resulting mixture was printed on the
substrates by the use of a seal mask. Then, the sealing agent was
tentatively cured to combine the upper and lower substrates.
Thereafter, the sealing agent was cured while pressing the two
substrates by the use of a press. Inside the panel surface,
spherical polymer beads were held between the substrates so that
the size of the gap between them might be 6.0 .mu.m when liquid
crystals were enclosed in the gap. The angle of rubbing for the
alignment layers was 45.degree. to the short side of each
substrate, and the direction of rubbing on the upper substrate was
perpendicular to that on the lower substrate. The width of an
opening for injecting liquid crystals was 30 mm. Subsequently,
liquid crystals were injected into the gap with a liquid crystal
injector to produce a liquid crystal display.
[0097] In the present embodiment, a light-emitting diode (LED) was
used as a backlight. The contrast and the transmittance at a
wavelength of 400 nm were improved by about 10% and about 5%,
respectively, as compared with liquid crystal displays using a
cold-cathode tube, because of not only the effect of the employment
of LED as a backlight but also the effect of the employment of the
transparent polyamicacid as a base polymer in the color filter
substrate. Moreover, the color purity was also improved by the
employment of LED.
[0098] As explained above, according to the present invention, not
only the contrast, color purity and transmittance for blue color of
color filters but also the productivity of a process for production
of the color filters are improved by using a polyamicacid whose
light transmittance decreases by 2% or less in the visible region
(wavelength: 400 nm to 800 nm), as a base polymer in a colored
composition for color filter comprising the base polymer, at least
one coloring agent and at least one solvent. Furthermore, a display
having a high contrast, a high color purity and an improved
transmittance for blue color can be provided by using such color
filters.
[0099] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *