U.S. patent application number 09/467977 was filed with the patent office on 2002-01-03 for color filter and method of manufacturing the same.
Invention is credited to OKADA, TAKESHI, SHIBA, SHOJI, SOBUE, MASASHI, TAKAO, HIDEAKI, YOKOYAMA, RYUICHI.
Application Number | 20020001762 09/467977 |
Document ID | / |
Family ID | 26581498 |
Filed Date | 2002-01-03 |
United States Patent
Application |
20020001762 |
Kind Code |
A1 |
SHIBA, SHOJI ; et
al. |
January 3, 2002 |
COLOR FILTER AND METHOD OF MANUFACTURING THE SAME
Abstract
A color filter comprising a substrate, a shielding layer formed
on the substrate and having an opening, color mixing prevention
barriers formed on the shielding layer, and colored portions formed
between the color mixing prevention barriers, the optical density
of the colorants in the colored portions being raised toward the
substrate.
Inventors: |
SHIBA, SHOJI;
(SAGAMIHARA-SHI, JP) ; TAKAO, HIDEAKI; (TOKYO,
JP) ; YOKOYAMA, RYUICHI; (YOKOHAMA-SHI, JP) ;
SOBUE, MASASHI; (YOKOHAMA-SHI, JP) ; OKADA,
TAKESHI; (ZUSHI-SHI, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
26581498 |
Appl. No.: |
09/467977 |
Filed: |
December 21, 1999 |
Current U.S.
Class: |
430/7 ; 347/106;
349/106 |
Current CPC
Class: |
G02F 1/133516 20130101;
G02B 5/201 20130101; G02F 1/133514 20130101 |
Class at
Publication: |
430/7 ; 347/106;
349/106 |
International
Class: |
G02F 001/1335; G02B
005/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1998 |
JP |
10-363615 |
Dec 22, 1998 |
JP |
10-363616 |
Claims
What is claimed is:
1. A color filter comprising a substrate, a shielding layer formed
on the substrate and having openings, and colored portions formed
in said openings, the optical density of colorants in said colored
portions being raised toward the substrate.
2. A color filter according to claim 1, wherein said shielding
layer is made of a black resin.
3. A color filter according to claim 1, wherein said colorants are
dyes.
4. A color filter according to claim 1, wherein said colorants are
pigments.
5. A color filter according to claim 1, further comprising a
protection layer on the surface thereof.
6. A method of manufacturing a color filter, comprising the steps
of forming a shielding layer having openings on a substrate,
forming a photosensitive resin on said substrate and said shielding
layer, coloring said photosensitive resin, and rinsing said
photosensitive resin.
7. A method of manufacturing a color filter according to claim 6,
wherein said coloring step uses an ink-jet system.
8. A method of manufacturing a color filter, comprising the steps
of forming a shielding layer having openings on a substrate,
applying inks to said openings, producing colored portions by
curing said inks, and rinsing said colored portions.
9. A method of manufacturing a color filter according to claim 8,
wherein said coloring step uses an ink-jet system.
10. A color filter comprising a substrate, a shielding layer formed
on the substrate and having an opening, color mixing prevention
barriers formed on said shielding layer, and colored portions
formed between said color mixing prevention barriers, the optical
density of colorants in said colored portions being raised toward
the substrate.
11. A color filter according to claim 10, wherein said shielding
layer is made of metal.
12. A color filter according to claim 10, wherein said colorants
are dyes.
13. A color filter according to claim 10, wherein said colorants
are pigments.
14. A color filter according to claim 10, further comprising a
protection layer on the surface thereof.
15. A method of manufacturing a color filter, comprising the steps
of forming a shielding layer having openings on a substrate,
forming a photosensitive resin on said substrate and said shielding
layer, forming color mixing prevention barriers by patterning said
photosensitive resin by exposing it to light, coloring said
photosensitive resin between said color mixing prevention barriers,
and rinsing said photosensitive resin.
16. A method of manufacturing a color filter according to claim 15,
wherein said coloring step uses an ink-jet system.
17. A liquid crystal element substrate, comprising a transparent
electro-conductive film formed on the surface of the color filter
according to claim 1 or 10.
18. A liquid crystal element substrate according to claim 17,
further comprising a protection layer between said color filter and
said transparent electro-conductive film.
19. A liquid crystal element, comprising a liquid crystal element
substrate prepared having a transparent electro-conductive film
formed on the color filter according to claim 1 or claim 10, an
opposite substrate arranged vis-a-vis relative to said liquid
crystal element substrate, and a liquid crystal filled into the gap
between said liquid crystal substrate and said opposite substrate,
said liquid crystal substrate and said opposite substrate being
hermetically sealed.
20. A liquid crystal element according to claim 19, further
comprising a protection layer between said color filter and said
transparent electro-conductive film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a color filter to be suitably used
for a color television set or the display device of a personal
computer and also to a method of manufacturing the same. More
particularly, the present invention relates to a color filter
having colored portions of the three primary colors by means of an
ink-jet system. The present invention also relates to a liquid
crystal element substrate using such a color filter and a liquid
crystal element formed by using such a substrate.
[0003] 2. Related Background Art
[0004] The technological development in the field of personal
computers in recent years, portable personal computers in
particular, has produced an ever-increasing demand for liquid
display devices, particularly for color liquid crystal display
devices. However, the demand can be met only when such display
devices are supplied at reduced cost. In more specific terms, there
is a strong demand for less costly color filters that take a
significant part in the overall cost of manufacturing display
devices.
[0005] While efforts have been paid to meet the demand while
satisfying the requirements for the performance of color filters,
no technology has been established to satisfy the requirements.
Firstly, typical known processes for preparing color filters will
be discussed.
[0006] First, a dyeing process is known. With this process, a
water-soluble polymeric material is formed on a glass substrate as
material to be colored and then it is patterned to show a desired
profile by photolithography. Thereafter, the obtained pattern is
immersed in a dye bath to produce a colored pattern. This dyeing
step is repeated three times for the three primary colors of red
(R), green (G) and blue (B) to obtain a colored layer of R, G and B
on the substrate.
[0007] Second, there is known a pigment dispersing process, which
is most popular in recent years. With this process, a
photosensitive resin layer containing a pigment in a dispersed
state is formed on a substrate and then the layer is patterned to
produce a mono-color pattern. Then, this pattern forming step is
repeated three times to obtain a layer colored to the three primary
colors of R, G and B.
[0008] Third, an electrodeposition process is known. With this
process, a transparent electrode is formed on a substrate by
patterning and a first color is produced by means of
electrodeposition of immersing the patterned electrode into an
electrodeposition coating solution containing a pigment, resin and
an electrolyte. Then, this step of producing a color is repeated
three times to form a colored layer of the three primary colors of
R, G and B. Finally, the formed layer is baked to complete the
process.
[0009] Fourth, there is known a process of dispersing pigments into
thermosetting resin, repeating a printing operation three times for
the three primary colors of R, G and B and curing the resin to
produce a colored layer.
[0010] With any of the above listed processes, a protection layer
is generally formed on the colored layer.
[0011] What is common to all the above listed processes is that a
same step has to be repeated three times for forming a colored
layer of the three primary color of R, G and B to consequently
raise the manufacturing cost. Additionally, a manufacturing method
involving a large number of steps is normally accompanied by a low
yield. Furthermore, patterns that can be formed by an
electrodeposition process are limited in terms of profile so that
such a process cannot be applied without difficulty to active
matrix type (so-called TFT type) liquid display devices comprising
TFTs (thin film transistors). On the other hand, a printing process
is not suited for finely pitched patterns because of the problem of
poor resolution that accompanies the process.
[0012] Japanese Patent Application Laid-Open Nos. 59-75205,
63-235901 and 1-217302 propose methods of manufacturing a color
filter by using an ink-jet system.
[0013] Methods of manufacturing a color filter by using an ink-jet
system provide the advantages of:
[0014] (1) simpleness of the manufacturing process;
[0015] (2) low manufacturing cost; and
[0016] (3) a wide choice of colorants because dyes can be used.
[0017] Dyes are much more abundant if compared with pigments so
that desired colors can be reproduced almost freely depending on
the application. Additionally, a color filter realized by using
dyes normally provides a high contrast if compared with a color
filter prepared by using pigments.
[0018] However, compared with pigments, dyes are normally
accompanied by the problems of:
[0019] (A) poor heat resistance, and
[0020] (B) high solubility to water and organic solvents.
[0021] Thus, a color filter prepared by using dyes typically
involves the following problems:
[0022] (A) When forming a protection layer on the colored portions
of the color filter by spin-coating, the dyes contained in the
colored portions can cause migration around the interface thereof
due to the organic solvent contained in the protection layer. Then,
the adhesion of the colored portions to the protection layer can be
deteriorated and/or the protection layer can become colored.
[0023] (B) When forming a transparent electro-conductive film on
the colored portions, the dyes contained in the colored portions
can become oxidized around the surface thereof because they are
exposed to an oxygen-containing atmosphere at high temperature.
When the dyes are oxidized, their color tones change and/or the
contrast of the color filter can be degraded.
SUMMARY OF THE INVENTION
[0024] In view of the above circumstances, it is therefore an
object of the present invention to provide a high performance color
filter that is free from the above identified problems and can
effectively prevent the problem of coloring the protection layer
and deteriorating the adhesion of the protection layer and the
problem of degradation of the contrast of the color filter when
forming a transparent electro-conductive film. Another object of
the present invention is to provide a highly reliable liquid
crystal element substrate comprising such a color filter and also a
liquid crystal element having excellent color display
characteristics.
[0025] According to the invention, the above objects are achieved
by providing a color filter comprising a substrate, a shielding
layer formed on the substrate and having openings, and colored
portions formed in the openings, the optical density of the
colorants in the colored portions being raised toward the
substrate.
[0026] According to the invention, there is also provided a color
filter comprising a substrate, a shielding layer formed on the
substrate and having an opening, color mixing prevention barriers
formed on the shielding layer, and colored portions formed between
the color mixing prevention barriers, the optical density of the
colorants in the colored portions being raised toward the
substrate.
[0027] According to the invention, there is also provided a method
of manufacturing a color filter, comprising the steps of forming a
shielding layer having openings on a substrate, forming
photosensitive resin on the substrate and the shielding layer,
coloring the photosensitive resin, and rinsing the photosensitive
resin.
[0028] According to the invention, there is also provided a method
of manufacturing a color filter, comprising the steps of forming a
shielding layer having openings on a substrate, applying inks to
the openings, producing colored portions by curing the inks, and
rinsing the colored portions.
[0029] According to the invention, there is also provided a method
of manufacturing a color filter, comprising the steps of forming a
shielding layer having openings on a substrate, forming
photosensitive resin on the substrate and the shielding layer,
forming color mixing prevention barriers by patterning the
photosensitive resin by exposing it to light, coloring the
photosensitive resin between the color mixing prevention barriers,
and rinsing the photosensitive resin.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G and 1H show a process
diagram of an embodiment of an method of manufacturing a color
filter according to the invention.
[0031] FIGS. 2A, 2B, 2C, 2D and 2E show a process diagram of
another embodiment of a method of manufacturing a color filter
according to the invention.
[0032] FIGS. 3A, 3B, 3C, 3D, 3E, 3F and 3G show a process diagram
of still another embodiment of a method of manufacturing a color
filter according to the invention.
[0033] FIG. 4 is a schematic cross sectional view of an embodiment
of a liquid crystal element according to the invention.
[0034] FIG. 5 is a graph summarily illustrating the result of
measuring the dye densities of the R-colored portions of the color
filter prepared in Example 1.
[0035] FIG. 6 is a graph summarily illustrating the result of
measuring the dye densities of the G-colored portions of the color
filter prepared in Example 1.
[0036] FIG. 7 is a graph summarily illustrating the result of
measuring the dye densities of the B-colored portions of the color
filter prepared in Example 1.
[0037] FIG. 8 is a graph summarily illustrating the result of
measuring the dye densities of the R-colored portions of the color
filter prepared in Example 7.
[0038] FIG. 9 is a graph summarily illustrating the result of
measuring the dye densities of the G-colored portions of the color
filter prepared in Example 7.
[0039] FIG. 10 is a graph summarily illustrating the result of
measuring the dye densities of the B-colored portions of the color
filter prepared in Example 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] FIGS. 1A through 1H show a process diagram of an embodiment
of a first method of manufacturing a color filter according to the
invention and are schematic sectional views which correspond to the
respective manufacturing steps (a) through (h) that will be
described hereinafter. Step (a)
[0041] A shielding layer 2 (normally referred to as black matrix)
having openings is formed on a transparent substrate 1 by using
black resin. While a glass substrate may preferably be used for the
transparent substrate 1 of a color filter according to the
invention, the material of the substrate is not limited to glass
and it may alternatively made of a plastic material or some other
appropriate material provided that it has properties required for a
color filter to be used for a liquid crystal element particularly
in terms of transparency and mechanical strength.
[0042] The black resin to be used for forming the shielding layer 2
is preferably a resin composite containing one or more colorants to
make it appear black. The use of commercially available black
resist may be a recommended choice. The shielding layer 2 can be
produced by patterning black resist by means of photolithography,
by patterning a black resin composite serving as resist by means of
photolithography, or by patterning a black resin composite by means
of printing, and subsequently thermosetting the obtained pattern of
the shielding layer.
[0043] For the purpose of the invention, the height of the
shielding layer 2 may be determined within a range that can provide
a satisfactory shielding effect, however, it is preferably between
1 and 2 .mu.m from the viewpoint of forming a uniform
photosensitive resin composite layer, which will be described
hereinafter. Step (b)
[0044] A negative type photosensitive resin compound layer 3 that
shows a good ink absorptivity after the irradiation of light on the
entire surface of the transparent substrate 1. For the purpose of
the present invention, any photosensitive resin composite may be
used provided that it has a negative photo-reactivity, shows a good
ink absorptivity after the irradiation of light and can be cured by
heat treatment. Specific examples of the photosensitive resin
composite include a system obtained by adding a photo-initiating
agent such as ammonium dichromate to a natural polymer such as
gelatin or casein, a system obtained by adding a photo-initiating
agent such as bis-azide to a synthetic polymer and a system
obtained by adding a photo-polymerizable compound and a
photo-initiating agent such as benzophenone to a synthetic polymer.
Synthetic polymers not having any photo-reactivity per se that can
be used for the purpose of the invention include a copolymer of an
anionic dyeable monomer, such as (N, N-dimethylamino)
ethylmethacrylate and 3-(N, N-dimethylamino) propylacrylamide, and
a hydrophilic monomer, such as acrylic acid and
hydroxyethylmethacrylate. Polymers having a photo-reactivity that
can be used for the purpose of the invention non-limitatively
include copolymers of any of the above listed copolymers, which
further include vinylcinnamate, vinylpyrrolidone or
trimethylolpropanetrimethacrlate.
[0045] The photosensitive resin composite is applied onto the
substrate and the shielding layer by an appropriate application
technique selected from spin-coating, dye-coating roll-coating,
bar-coating, spray-coating and dip-coating, and the use of a
spin-coating technique is especially preferable from the viewpoint
of applying the composite uniformly on the substrate having
undulations produced by the shielding layer. Step (c)
[0046] The photosensitive resin composite layer 3 in the region of
the openings of the shielding layer 2 is irradiated with light to
cure the resin composite in the openings. While the photosensitive
resin composite layer 3 may be irradiated with light from the front
surface thereof, using a photomask, the shielding layer 2 can
preferably be utilized as a mask to eliminate the use of a
photomask and the need of aligning the photomask and the shielding
layer 2 to consequently improve the manufacturing efficiency and
the reliability of the color filter by irradiating the
photosensitive resin layer 3 with light from the rear surface of
the transparent substrate 1. Step (d)
[0047] Then, the photosensitive resin composite is subjected to a
development process to remove any part thereof that is not exposed
to light and remaining on the shielding layer 2. Thus, the cured
photosensitive resin composite is left in the openings of the
shielding layer 2 to form coloring portions 4. While an aqueous
solution type developer or an organic solvent type developer can be
used for the development process, water or an alkaline aqueous
solution may preferably be used from the viewpoint of easy handling
and safety of the process.
[0048] While the photosensitive resin composite may be dried after
the development process by spin-drying, by the use of an air knife
or by heating, the temperature of the drying process should be such
that it does not promote the thermosetting reaction of the
photosensitive resin composite. Step (e)
[0049] Coloring inks 5 of R, G and B are applied to the respective
coloring portions 4 by using an ink-jet recording apparatus (not
shown). While colorants that can be used for coloring inks for the
purpose of the invention may be dyes or pigments, dye-type inks are
preferably used in view of the fact the present invention is
intended to solve the problems of known color filters realized by
using dyes.
[0050] A preferable ink carrier to be used for an ink-jet recording
apparatus is a mixed solvent obtained by mixing water and a
water-soluble organic solvent. For the purpose of the invention,
not ordinary water containing various ions but ion-exchanged water
(de-ionized water) is preferably used.
[0051] Other water soluble organic solvents that can also be used
for the purpose of the invention include alkyl alcohols having 1 to
4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl
alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol and
tert-butyl alcohol, amides such as dimethylformamide and
dimethylacetamide, ketones such as acetone, keto alcohols such as
diacetone alcohol, ethers such as tetrahydrofuran and dioxane,
polyalkyleneglycols such as polyethyleneglycol and
polypropyleneglycol, alkyleneglycols having alkylene radicals with
2 to 4 carbon atoms such as ethyleneglycol, propyleneglycol,
butyleneglycol, triethyleneglycol, thiodiglycol, hexyleneglycol and
diethyleneglycol, glycerols, lower alkylethers of polyhydric
alcohols such as ethyleneglycolmonomethylether,
diethyleneglycolmethylether and triethyleneglycolmonomethylether,
N-methyl-2-pyrrolidone and 2-pyrrolidone. Of the above listed water
soluble organic solvents, polyhydric alcohols such as
diethyleneglycol, lower alkylethers of polyhydric alcohols such as
triethyleneglycolmonomet- hylether and N-methyl-2-pyrrolidone may
preferably be used.
[0052] In addition to the above ingredients, a surface active
agent, a defoaming agent and/or an antiseptic may also be added if
necessary for making the inks show desired physical properties.
[0053] Inks that can be used for the purpose of the invention may
be liquid at a room temperature or may be such that they are
solidified at or below a room temperature but softened or liquefied
at a room temperature or they are in a liquid state when ejected
from a nozzle in view of the fact than the ink temperature is
adjusted to be between 30 and 70.degree. C. in an ordinary ink-jet
recording apparatus in order to make the ink show a desired
viscosity level.
[0054] Ink-jet systems that can be used for the purpose of the
invention include those of the bubble jet type using electrothermal
converters as energy generating elements and those of the piezo-jet
type using piezoelectric elements. Such systems normally provide a
wide choice for the area to be colored and the coloring pattern.
Step (f)
[0055] After allowing the coloring inks 5 to disperse sufficiently
in the coloring portions 4, the inks are dried, if necessary, and
the coloring portions 4 that have been colored are cured by heat to
produce colored portions 6. Step (g)
[0056] The colored portions 6 are rinsed to remove the colorants on
the surface thereof. Rinsing solutions that can be used for the
purpose of the invention are those adapted to dissolve the
colorants. When the colorants are dyes, they can be removed
effectively by means of pure water or an alkaline aqueous solution.
Rinsing techniques that can be used for the purpose of the
invention non-limitatively include dip-rinsing, spin-rinsing and
shower-rinsing.
[0057] The colorants on the surface of the colored portions 6 are
rinsed and removed with this step. As a result, the colorants come
to show an optical density distribution along the depth of the
colored portions, the optical density of the colorants in said
colored portions being raised toward the transparent substrate 1.
Step (h)
[0058] A protection layer 7 is formed whenever necessary. Materials
that can be used for the protection layer 7 include resin materials
of the photo-setting type, the thermosetting type and the
photo-thermosetting type and inorganic films formed by evaporation
or sputtering. In other words, any materials that is satisfactorily
transparent when used for a color filter and can withstand the
subsequent process of forming a transparent electro-conductive film
and that of forming an oriented film can be used for the purpose of
the invention.
[0059] Since the optical density of the colored portions 6 is low
at the surface in a color filter according to the invention, the
migration of the colorants from the colored portions is minimized
and the protection layer 7 can be made to show an excellent
adhesion. If the protection layer 7 is not formed in a color filter
according to the invention and a transparent electro-conductive
film is formed directly on the colored portions 6 to prepare a
liquid crystal element, the color filter can minimize the
degradation of the color tone due to the oxidation of the dyes on
the surface of the colored portions 6 that can arise in the
oxygen-containing atmosphere in the step of forming the transparent
electro-conductive film because of the fact that the optical
density of the colored portions 6 is low at the surface.
[0060] Now, a second method of manufacturing a color filter
according to the invention will be described. FIGS. 2A through 2E
are schematic sectional views of a color filter being prepared in
the second method of manufacturing a color filter according to the
invention and correspond to the respective manufacturing steps (a)
through (e) that will be described hereinafter. The same components
as those of the color filter of FIGS. 1A through 1H are denoted
respectively by the same reference symbols and will not be
described any further. Step (a)
[0061] A shielding layer 2 is formed on a transparent substrate 1.
This step is identical with Step (a) in FIG. 1A and the members
involved in this step are also the same as those of FIG. 1A. Step
(b)
[0062] Curable type inks of R, G and B are applied to the openings
of the shielding layer 2 located at respective positions by means
of an ink-jet recording apparatus (not shown).
[0063] Curable type inks 21 to be used for the purpose of the
invention are those that are cured when energy is applied thereto
preferably in the form of irradiation of light or heat treatment
and contain one or more bridgeable monomers and/or polymers that
can fix the dyes or pigments of the inks. Specific examples of the
bridgeable compound that can be used for the purpose of the
invention include polymerizable oligomers such as epoxyacrylate,
urethaneacrylate, polyesteracrylate and polyetheracrylate,
polymerizable monomers such as mono-functional acrylates and
multi-functional acrylates and polymers of such monomers. If
necessary, one or more bis-azido compounds, a radical type
initiating agent and/or a cation type initiating agent may be added
to the inks. Step (c)
[0064] The curable type inks 21 are cured by means of an
appropriate process such as irradiation of light or heat treatment
to produce colored portions 6. Step (d)
[0065] The colored portions 6 are rinsed to remove the colorants on
the surface thereof. This step corresponds to Step (g) of FIG. 1G
and any of the rinsing solutions and the rinsing methods described
above for Step (g) of FIG. 1G may also be used in this second
method. Step (e)
[0066] If necessary, a protection layer 7 is formed on the colored
portions 6 in a manner as described above by referring to the first
method.
[0067] FIGS. 3A through 3G are schematic sectional views of a color
filter being prepared in another embodiment of a method of
manufacturing a color filter according to the invention and
correspond to the respective manufacturing steps (a) through (g)
that will be described hereinafter. The same components as those of
the color filter of FIGS. 1A through 1H are denoted respectively by
the same reference symbols and will not be described any further.
Step (a)
[0068] A shielding layer 32 having openings is formed on a
transparent substrate 1.
[0069] More specifically, the shielding layer 32 is formed by
forming a film of chromium or the like by means of a sputtering or
evaporation technique and patterned to show a desired profile. The
metal shielding layer 32 preferably has a thickness between 0.1 and
0.5 .mu.m. Step (b)
[0070] An ink-receiving layer 3 of a photosensitive resin composite
that has ink absorptivity which changes by the irradiation of light
with or without heat treatment is formed on the surface of the
transparent substrate 1 including the shielding layer 32. The
photosensitive resin composite to be used in this embodiment may be
of the negative type that loses or reduces its ink absorptivity as
a result of irradiation of light with or without heat treatment or
of the positive type that reveals or increases its ink absorptivity
as a result of irradiation of light with or without heat
treatment.
[0071] Specific examples of base resin material that can be used
for negative type photosensitive resin composites include acrylic
resin, epoxy resin and silicone resin having functional groups,
such as hydroxy groups, carboxyl groups, alkoxy groups and amide
groups, cellulose derivatives such as hydroxypropylcellulose,
hydroxyethylcellulose methylcellulose and carboxymethylcellulose,
modified products of the cellulose derivatives,
polyvinylpyrrolidone, polyvinylalcohol and polyvinylacetal. A
bridging agent or a photo-initiating agent may also be used in
order to make such resin chemically react by irradiation of light
with or without heat treatment. Specific examples of the bridging
agent include melamine derivatives such as methylolmelamine,
whereas specific examples of the photo-initiating agent include
dichromate, bis-azide compounds, radial type initiating agents,
cation type initiating agents and anion type initiating agents. A
plurality of such photosensitizers may be combined or such a
photosensitizer may be combined with some other sensitizer for the
purpose of the invention.
[0072] Specific examples of the positive type photosensitive resin
composite include silicone type resins having disilane bonds such
as polysilane, mixtures of resin having hydroxy groups, such as
hydroxypropylcellulose, polyvinylalcohol, cresolnovolac resin and
polyparahydroxystyrene, and naphthoquinonediazide, and mixtures of
resin formed by blocking the hydroxy groups of the resin selected
from the above listed compounds having hydroxy groups by means of
acetyl groups or trimethylsilyl groups and a cation type
photo-initiator.
[0073] The selected photosensitive resin composite is then applied
onto the transparent substrate 1 by means of an appropriate
application technique such as spin-coating roll-coating,
bar-coating, spray-coating and dip-coating and, if necessary,
pre-baked to produce a ink-receiving layer 3. Any appropriate
process may be used for forming the ink-receiving layer 3. Step (c)
The ink-receiving layer 3 is patterned by irradiation of light,
using a photomask 34 to produce non-coloring portions 35 showing a
low ink absorptivity (or not showing any ink absorptivity) and
coloring portions 4 showing a high ink absorptivity (or showing an
ink absorptivity). The non-coloring portions 35 operate as a color
mixing prevention barrier. In the following description of this
mode of carrying out the invention, the ink-receiving layer is made
of a negative type photosensitive resin composite that loses its
ink absorptivity when exposed to light. As described above,
non-coloring portions 35 are formed on the shielding layer 32 in
this step. The non-coloring portions 35 prevent mixing of inks of
different colors between the coloring portions 4.
[0074] As the non-coloring portions 35 are formed on the shielding
layer 32 and made to have a width smaller than that of the
shielding layer 32, the colored portions 6, which will be described
hereinafter, can extend to overlap the shielding layer 32 to
eliminate any risk of color skip. Step (d)
[0075] Inks 5 of R, G and B are applied to the coloring portions 4
located in respective positions by means of an ink-jet recording
apparatus (not shown). Step (e)
[0076] When the colorant inks permeate satisfactorily into the
respective coloring portions 4, they are subjected to a drying
process, if necessary, and the coloring portions that have been
colored are cured by subjecting them to irradiation of light and/or
heat treatment to produce colored portions 6. Step (f)
[0077] The colored portions 6 are rinsed to remove the colorants
adhering to the surface thereof. Step (g)
[0078] If necessary, a protection layer 7 is formed on the
surface.
[0079] A liquid crystal element substrate according to the
invention is prepared by forming a transparent electro-conductive
film on a color filter as shown in FIG. 1G or 1H, FIG. 2D or 2E or
FIG. 3F or 3G. As described above, a color filter according to the
invention shows a low optical density on the surface thereof as the
colorants on the surface of the colored portions are rinsed and
removed. Thus, the liquid crystal element substrate prepared by
forming a transparent electro-conductive film thereon is hardly
affected by the colorants and hence can provide a good adhesion
between the protection layer and the colored portions. In other
words, the liquid crystal element substrate can minimize the
degradation of the color tone of the colored portions due to the
oxidation of the colorants on the surface of the colored portions 6
that can arise when the transparent electro-conductive film is
formed.
[0080] Now, a liquid crystal element comprising a color filter
according to the invention will be described. FIG. 4 is a schematic
cross sectional view of an embodiment of a liquid crystal element
according to the invention, which is an active matrix type liquid
crystal element. In FIG. 4, there are shown a common electrode 22,
an oriented film 23, a substrate 30, pixel electrodes 32, another
oriented film 33 and a liquid crystal layer 24. The components same
as those of FIGS. 1A through 1H are denoted respectively by the
same reference symbols.
[0081] A liquid crystal element for color display is prepared
generally by combining the substrate 1 on the side of a color
filter and the TFT substrate 30 vis-a-vis, filling the gap between
the two substrates with a liquid crystal compound 24 and
hermetically sealing the substrates. TFTs (not shown) and
transparent pixel electrodes 32 are formed on the inner surface of
one of the substrates of the liquid crystal element, while a color
filter layer is formed on the inner surface of the other substrate
1 with the colored portions 6 of R, G and B arranged at positions
opposite to the respective pixel electrodes 32 and a transparent
common electrode 22 is formed thereon to cover the entire surface.
Then, the substrates are covered by the respective oriented films
23, 33 and the molecules of the liquid crystal can be oriented in
one direction by rubbing the films.
[0082] A pair of polarizing plates (not shown) are bonded
respectively to the outer surfaces of the substrates 1, 30 and the
combination of a fluorescent lamp (not shown) and a scattering
plate (not shown) is used as back light. Then, the liquid crystal
compound is used as an optical shutter with a variable
transmittivity for rays of light from the back light in order to
display desired images.
[0083] While a liquid crystal element according to the invention
comprises a color filter prepared according to the invention, known
techniques can be used for all the other components, their
materials and the methods of preparing them.
Examples
Example 1
[0084] Black resist (available from Shinnittetsu Chemical) was
applied onto a glass substrate ("1737": tradename, available from
Coning) and a latticework of a shielding layer (black matrix) was
produced as a result of a process of exposure to light, development
and post-baking. The obtained shielding layer had a height of 1.2
.mu.m. Then, a photosensitive resin composite having the
composition as listed below is applied thereto by spin-coating and
pre-baked at 50.degree. C. for 3 minutes to produce a 1.0 .mu.m
thick layer of the photosensitive resin composite. photosensitive
resin composite.
1 [photosensitive resin composite] copolyer having the following
composition 20 phr hydroxyethylmethacrylate 80 phr vinylcinnamate
10 phr acrylic acid 10 phr bis-azide type photosensitizing agent
0.5 phr ("A-066H": tradename, available from Sinko Giken) 79.5 phr
ethylcellosolve
[0085] The composite was entirely exposed to light having a
wavelength of 365 nm and irradiated from the rear surface of the
substrate at a rate of 200 mJ/cm.sup.2 Then, it was developed in an
alkaline aqueous solution (pH=10), rinsed with pure water and dried
by means of a spin-drier to obtain a substrate having a black
matrix and imbedded with coloring portions of the photosensitive
resin composite in the openings of the black matrix.
[0086] Thereafter, inks of colorants of R, G and B were applied to
the respective coloring portions by a predetermined amount by means
of an ink-jet recording apparatus and it was confirmed that the
inks had permeated satisfactorily into the coloring portions. Then,
the portions that were already colored were subjected to heat
treatment at 90.degree. C. for 5 minutes and subsequently at
230.degree. C. for 30 minutes to cure the colored portions.
2 (ink compositions) R ink C. I. acid orange 148 6 phr C. I. acid
red 289 1 phr diethyleneglycol 30 phr ion-exchanged water 63 phr G
ink C. I. acid yellow 23 3 phr zinc phthalocyaninesulfonamide 3 phr
ditheylenglycol 30 phr ion-exchanged water 64 phr B ink C. I.
direct blue 199 6 phr diethyleneglycol 30 phr ion-changed water 64
phr
[0087] Subsequently, the colored portions were rinsed with pure
water by means of a spin-rinsing technique. FIGS. 5 through 7 are
graphs summarily illustrating the result of measuring the dye
densities of the colored portions of the color filter prepared in
Example 1 as observed along the thickness of the colored portions
before and after the rinsing process. A SIMS (secondary ion mass
spectrograph) was used for measuring the dye densities. The amounts
of metal atoms (chromium atoms for R, zinc atoms for G and copper
atoms for B) contained in each dye molecule were determined and
compared with the amount of carbon atoms to obtain standardized
respective densities. As clearly seen from FIGS. 5 through 7, all
the dye densities of R, G and B of the colored portions were
reduced on the surface as a result of the rinsing process.
[0088] Thereafter, a double-solution type thermosetting resin
composite ("SS6699G": tradename, available from JSR) was applied
onto the colored portions to a thickness of 1 .mu.m by spin-coating
and prebaked at 90.degree. C. for 30 minutes. Then, the applied
resin composite was subjected to heat treatment at 250.degree. C.
for 60 minutes to produce a protection layer.
[0089] The prepared color filter was then observed for the
chromaticity of the colored portions by means of a
microspectrometric analyzer (available from Olympus) to find no
abnormality in the chromaticity. The protection layer was not
exfoliated when subjected to a cross-cut peeling test.
[0090] Finally, a 0.12 .mu.m thick ITO film was formed on the
protection layer to complete the operation of preparing a liquid
crystal element substrate. The chromaticity of the colored portions
of the substrate were once again observed by means of a
microspectrometric analyzer to find no abnormality in the
chromaticity. The protection layer was not exfoliated when
subjected to another cross-cut peeling test.
Example 2
[0091] The above described procedure of Example 1 was followed to
obtain a color filter except that an alkaline aqueous solution
(pH=11) was used as rinsing solution in this example. The
chromaticity of the colored portions was measured by means of a
microspectrometric analyzer as in Example 1 to find no abnormality.
The protection layer was not exfoliated as a result of a cross-cut
peeling test.
Example 3
[0092] The above described procedure of Example 1 was followed to
obtain a liquid crystal element substrate except that an ITO film
was formed directly on the colored portions without forming a
protection layer in this example. The chromaticity of the colored
portions was measured by means of a microspectrometric analyzer as
in Example 1 to find no abnormality. The ITO film was not
exfoliated as a result of a cross-cut peeling test.
Comparative Example 1
[0093] The above described procedure of Example 1 was followed to
obtain a liquid crystal element substrate except that no rinsing
operation was conducted in this example. The chromaticity of the
colored portions was measured by means of a microspectrometric
analyzer as in Example 1 to find a phenomenon of spectral change
due to the migration of dyes into the protection layer.
Additionally, the protection layer was exfoliated as a result of a
cross-cut peeling test.
Comparative Example 2
[0094] The above described procedure of Example 3 was followed to
obtain a color filter in this example except that no rinsing
operation was conducted in this example. The chromaticity of the
colored portions was measured by means of a microspectrometric
analyzer as in Example 1 to find a phenomenon of spectral change
due to the oxidation of dyes. Additionally, the ITO film was
exfoliated as a result of a cross-cut peeling test.
Example 4
[0095] A black matrix was formed on a glass substrate as in Example
1 and then curable inks of R, G and B were applied to the
respective coloring portions by a predetermined amount. Then, the
portions that were already colored were subjected to heat treatment
at 90.degree. C. for 5 minutes and subsequently at 230.degree. C.
for 30 minutes to cure the colored portions.
3 (compositions of curable inks) R ink R dye 4 phr pure water 56
phr diethyleneglycol 30 phr curable type acryl resin 10 phr G ink G
dye 3 phr pure water 57 phr ditheylenglycol 30 phr curable type
acryl resin 10 phr B ink B dye 5 phr pure water 45 phr
diethyleneglycol 40 phr curable type acryl resin 10 phr
[0096] Subsequently, the colored portions were rinsed with pure
water by means of a spin-rinsing technique. Then, as in Example 1,
a SIMS (secondary ion mass spectrograph) was used for measuring the
dye densities to find that all the dye densities of R, G and B of
the colored portions had been reduced on the surface as a result of
the rinsing process.
[0097] Thereafter, a protection layer was formed on the colored
portions as in Example 1.
[0098] Then, as in Example 1, the prepared color filter was then
observed for the chromaticity of the colored portions by means of a
microspectrometric analyzer to find no abnormality in the
chromaticity. The protection layer was not exfoliated when
subjected to a cross-cut peeling test.
[0099] Finally, a 0.12 .mu.m thick ITO film was formed on the
protection layer as in Example 1 to complete the operation of
preparing a liquid crystal element substrate. The chromaticity of
the colored portions of the substrate were once again observed by
means of a microspectrometric analyzer to find no abnormality in
the chromaticity. The protection layer was not exfoliated when
subjected to another cross-cut peeling test.
Example 5
[0100] The above described procedure of Example 4 was followed to
obtain a color filter except that an isalkaline aqueous solution
(pH=11) was used as rinsing solution in this example. The
chromaticity of the colored portions was measured by means of a
microspectrometric analyzer as in Example 4 to find no abnormality.
The protection layer was not exfoliated as a result of a cross-cut
peeling test.
Example 6
[0101] The above described procedure of Example 4 was followed to
obtain a liquid crystal element substrate except that an ITO film
was formed directly on the colored portions without forming a
protection layer in this example. The chromaticity of the colored
portions was measured by means of a microspectrometric analyzer as
in Example 1 to find no abnormality. The ITO film was not
exfoliated as a result of a cross-cut peeling test.
Comparative Example 3
[0102] The above described procedure of Example 4 was followed to
obtain a liquid crystal element substrate except that no rinsing
operation was conducted in this example. The chromaticity of the
colored portions was measured by means of a microspectrometric
analyzer as in Example 4 to find a phenomenon of spectral change
due to the migration of dyes into the protection layer.
Additionally, the protection layer was exfoliated as a result of a
cross-cut peeling test.
Comparative Example 4
[0103] The above described procedure of Example 6 was followed to
obtain a color filter in this example except that no rinsing
operation was conducted in this example. The chromaticity of the
colored portions was measured by means of a microspectrometric
analyzer as in Example 6 to find a phenomenon of spectral change
due to the oxidation of dyes. Additionally, the ITO film was
exfoliated as a result of a cross-cut peeling test.
Example 7
[0104] A latticework of a 0.15 .mu.m thick shielding layer (black
matrix) of chromium was formed on a glass substrate. Then, a
photosensitive resin composite obtained by dissolving 97 phr of an
acryl type copolymer having the composition as listed below
4 methylmethacrylate 50 phr; hydroxyethylmethacrylate 30 phr; and
N-methylolacrylamide 20 phr
[0105] and 3 phr of triphenylsulfoniumtriflate dissolved in
ethylcellosolve was applied thereto by spin-coating to a film
thickness of 2 .mu.m and pre-baked at 90.degree. C. for 20 minutes
to produce an ink-receiving layer.
[0106] Thereafter, the ink-receiving layer on the black matrix was
partly exposed to light with a photomask having stripe-shaped
openings of a width smaller than that of the black matrix
interposed therebetween to produce a pattern, which was then
subjected to heat treatment on a hot plate at 120.degree. C. for 1
minute to produce coloring portions and non-coloring portions in
the ink-receiving layer.
[0107] Thereafter, inks of colorants of R, G and B were applied to
the respective coloring portions by a predetermined amount by means
of an ink-jet recording apparatus.
[0108] After allowing the inks to satisfactorily permeate into the
coloring portions, the portions that had been already colored were
subjected to heat treatment at 90.degree. C. for 5 minutes and
subsequently at 200.degree. C. for 60 minutes to cure the colored
portions.
[0109] Subsequently, the colored portions were rinsed with pure
water by means of a spin-rinsing technique. FIGS. 8 through 10 are
graphs summarily illustrating the result of measuring the dye
densities of the colored portions of the color filter prepared in
Example 7 as observed along the thickness of the colored portions
before and after the rinsing process in a manner as described for
Example 1. As clearly seen from FIGS. 8 through 10, all the dye
densities of R, G and B of the colored portions were reduced on the
surface as a result of the rinsing process.
[0110] Thereafter, a double-solution type thermosetting resin
composite ("SS6699G": tradename, available from JSR) was applied
onto the colored portions to a thickness of 1 .mu.m by spin-coating
and prebaked at 90.degree. C. for 30 minutes. Then, the applied
resin composite was subjected to heat treatment at 250.degree. C.
for 60 minutes to produce a protection layer.
[0111] The prepared color filter was then observed for the
chromaticity of the colored portions by means of a
microspectrometric analyzer (available from Olympus) to find no
abnormality in the chromaticity. The protection layer was not
exfoliated when subjected to a cross-cut peeling test.
[0112] Finally, a 0.12 .mu.m thick ITO film was formed on the
protection layer to complete the operation of preparing a liquid
crystal element substrate. The chromaticity of the colored portions
of the substrate were once again observed by means of a
microspectrometric analyzer to find no abnormality in the
chromaticity. The protection layer was not exfoliated when
subjected to another cross-cut peeling test.
Example 8
[0113] The above described procedure of Example 7 was followed to
obtain a color filter except that an alkaline aqueous solution
(pH=11) was used as rinsing solution in this example. The
chromaticity of the colored portions was measured by means of a
microspectrometric analyzer as in Example 7 to find no abnormality.
The protection layer was not exfoliated as a result of a cross-cut
peeling test.
Example 9
[0114] The above described procedure of Example 7 was followed to
obtain a liquid crystal element substrate except that an ITO film
was formed directly on the colored portions without forming a
protection layer in this example. The chromaticity of the colored
portions was measured by means of a microspectrometric analyzer as
in Example 7 to find no abnormality. The ITO film was not
exfoliated as a result of a cross-cut peeling test.
Comparative Example 5
[0115] The above described procedure of Example 7 was followed to
obtain a liquid crystal element substrate except that no rinsing
operation was conducted in this example. The chromaticity of the
colored portions was measured by means of a microspectrometric
analyzer as in Example 7 to find a phenomenon of spectral change
due to the migration of dyes into the protection layer.
Additionally, the protection layer was exfoliated as a result of a
cross-cut peeling test.
Comparative Example 6
[0116] The above described procedure of Example 9 was followed to
obtain a color filter in this example except that no rinsing
operation was conducted in this example. The chromaticity of the
colored portions was measured by means of a microspectrometric
analyzer as in Example 7 to find a phenomenon of spectral change
due to the oxidation of dyes. Additionally, the ITO film was
exfoliated as a result of a cross-cut peeling test.
[0117] As described above in detail, since the optical density of
the colored portions is made low on the surface in a color filter
according to the invention, the migration of the colorants from the
colored portions is minimized along the interface of the colored
portions and the protection layer, if such a protection layer is
formed; and the protection layer can be prevented from the
deterioration of adhesion and from being colored with dyes.
Additionally, when a transparent electro-conductive film is formed
on the colored portions, the phenomenon of change of the color tone
of the colorants due to oxidation can be effectively suppressed to
minimize the possible degradation of the contrast of the color
filter because the exposure to the oxygen containing atmosphere of
the colorants is minimized in the step of forming a transparent
electro-conductive film.
[0118] Thus, the present invention provides a color filter
comprising colored portions and a protection layer that firmly
adhere to each other, while minimizing the possible coloring of the
protection layer and a liquid crystal element substrate that is
free from any change of color tone and shows an excellent contrast
as well as a liquid crystal element showing excellent color display
characteristics and high reliability.
* * * * *