U.S. patent application number 09/817191 was filed with the patent office on 2001-10-04 for color filter and method of making the same.
This patent application is currently assigned to Seiko Epson Corporation. Invention is credited to Kiguchi, Hiroshi, Kojima, Masaru, Nishikawa, Takao.
Application Number | 20010026896 09/817191 |
Document ID | / |
Family ID | 27275883 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010026896 |
Kind Code |
A1 |
Nishikawa, Takao ; et
al. |
October 4, 2001 |
Color filter and method of making the same
Abstract
A template (12) having a plurality of protrusions (13) in a
predetermined arrangement is fabricated to facilitate the formation
of ink filling concavities for forming a color pattern layer. An
ink filling layer precursor (11) is attached to the template (12)
and, after the ink filling layer precursor (11) has solidified to
form an ink filling layer (14), the ink filling layer (14) having a
plurality of ink filling concavities (15) is transfer-formed by
separating the ink filling layer (14) from the template (12). Ink
of previously determined colors are filled into these ink filling
concavities (15) to form a color pattern layer (16).
Inventors: |
Nishikawa, Takao;
(Shiojiri-shi, JP) ; Kiguchi, Hiroshi; (Suwa-shi,
JP) ; Kojima, Masaru; (Suwa-shi, JP) |
Correspondence
Address: |
Oliff & Berridge, PLC
P.O. Box 19928
Alexandria
VA
22320
US
|
Assignee: |
Seiko Epson Corporation
|
Family ID: |
27275883 |
Appl. No.: |
09/817191 |
Filed: |
March 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09817191 |
Mar 27, 2001 |
|
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09171527 |
Nov 12, 1998 |
|
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09171527 |
Nov 12, 1998 |
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PCT/JP98/00718 |
Feb 23, 1998 |
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Current U.S.
Class: |
430/7 |
Current CPC
Class: |
G02B 5/201 20130101;
G02B 5/223 20130101 |
Class at
Publication: |
430/7 |
International
Class: |
G02B 005/00; G02F
001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 1997 |
JP |
9-39583 |
Jan 9, 1998 |
JP |
10-3551 |
Jan 9, 1998 |
JP |
10-3552 |
Claims
1. A method of making a color filter comprising: a first step of
fabricating a template having a plurality of protrusions in a
predetermined array; a second step of transfer-forming an ink
filling layer having a plurality of ink filling concavities by
causing an ink filling layer precursor to adhere to said template,
solidifying said ink filling layer precursor to form said ink
filling layer, then separating said ink filling layer from said
template; and a third step of filling said ink filling cavities
with ink of previously determined colors, to form a color pattern
layer.
2. The method of making a color filter of claim 1, wherein said
first step comprises a step of forming a resist layer of a
predetermined pattern on a substrate, then forming said protrusions
on said substrate by etching to obtain said template.
3. The method of making a color filter of claim 2, wherein: said
substrate is a silicon wafer.
4. The method of making a color filter of claim 1, wherein: said
first step comprises a step of forming a resist layer of a
predetermined pattern on a base plate, then making said base plate
and said resist layer conductive, and further using
electrodeposition to deposit metal by an electroplating method to
form a metal layer, and finally separating said metal layer from
said base plate and said resist layer to obtain said template.
5. The method of making a color filter of claim 1, wherein: said
ink filling layer precursor used in said second step is a material
which can be hardened by application of energy.
6. The method of making a color filter of claim 5, wherein: said
energy is at least one of light and heat.
7. The method of making a color filter of claim 6, wherein: said
ink filling layer precursor is a resin which is hardened by
ultraviolet rays.
8. The method of making a color filter of claim 1, wherein: said
ink is injected by an inkjet method in said third step.
9. The method of making a color filter of any one of claims 1 to 8,
wherein: an opaque material is injected into concavities between
said protrusions of said template after said first step but before
said second step, to form an opaque layer; and said opaque layer is
integrated with said ink filling layer in said second step, by
using said template on which is formed said opaque layer.
10. The method of making a color filter of claim 9, wherein: said
opaque material is injected by an inkjet method.
11. The method of making a color filter of claim 9, wherein: an
inner side surface of each of said concavities of said template is
formed in a tapered shape in such a manner that area of an aperture
portion thereof is larger than area of a base surface thereof.
12. The method of making a color filter of claim 9, wherein: each
of said concavities of said template is formed in a tapered shape
at an aperture edge portion of an inner side surface thereof.
13. A method of making a color filter, comprising: a first step of
forming a plurality of colored layers; a second step of placing a
protective film precursor on said colored layers; and a third step
of forming a protective film precursor layer by flattening a
surface of said protective film precursor with a template having a
flat surface corresponding to at least an optically transparent
region of said colored layers, then hardening said protective film
precursor layer to form a protective film.
14. The method of making a color filter of claim 13, wherein: at
least one concavity is provided in a surface of said template
corresponding to a region other than an optically transparent
region of said colored layers; a shape of said concavities of said
template is transferred to said protective film precursor layer in
said third step, to form protrusions in said protective film
corresponding to said concavities; and said protrusions act as
support members for maintaining a constant spacing for injecting
liquid crystal into a liquid crystal panel.
15. The method of making a color filter of claim 14, wherein: said
second step causes said concavities of said template to be
positioned above and between said colored layers.
16. The method of making a color filter of claim 14, wherein: an
inner shape of each of said concavities is a circular cylindrical
shape.
17. The method of making a color filter of claim 13, wherein: said
protective film precursor is a material which can be hardened by
application of energy.
18. The method of making a color filter of claim 17, wherein: said
energy is at least one of light and heat.
19. The method of making a color filter of claim 13, wherein: said
protective film precursor is a resin which is hardened by
ultraviolet rays.
20. The method of making a color filter of any one of claims 13 to
19, wherein: a transparent electrode film is previously formed on
said template; and after said transparent electrode film is placed
in contact with said protective film precursor, said protective
film precursor layer is formed by said template, and said
protective film precursor is hardened to form a protective film in
said third step, then said template is separated from said
protective film precursor layer, leaving said transparent electrode
remaining on said protective film precursor layer.
21. The method of making a color filter of claim 20, wherein: a
separation layer is formed between said template and said
transparent electrode film, to promote separation of said two
components.
22. A color filter comprising an ink filling layer having a
plurality of ink filling concavities; and a color pattern layer
formed in said ink filling cavities, and wherein said ink filling
layer is formed by causing a template having a plurality of
protrusions in a predetermined array to adhere to an ink filling
layer precursor, then solidifying said ink filling layer
precursor.
23. A color filter comprising a plurality of colored layers; and a
protective film formed on said colored layers, and wherein said
protective film is formed by flattening a surface of protective
film precursor with a template having a flat surface corresponding
to at least an optically transparent region of said colored layers,
then hardening said protective film precursor layer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a color filter for use in a
liquid crystal display panel or the like, and a method of making
the same.
BACKGROUND ART
[0002] Methods of making a color filter for a liquid crystal
display panel or the like include dyeing, pigment dispersion,
printing, and electrodeposition methods. Of these fabrication
methods, the printing method has a drawback with respect to
accuracy, and the electrodeposition method has a drawback
concerning patterning restrictions, and for those reasons the
dyeing method and pigment dispersion method have been most widely
used in the art.
[0003] However, the dyeing method and the pigment dispersion method
each require a lithography step for forming the pixel regions for
each of the first color, second color, and third color, which is a
big obstacle to improving the efficiency of mass production. One
method for forming pixels without such a lithography step for each
color is an inkjet method of making a color filter, which is
disclosed in a number of publications, such as Japanese Patent
Application Laid-Open No. 59-75205 and Japanese Patent Application
Laid-Open No. 61-245106. Using an inkjet method to form the color
pattern improves the efficiency of use of materials and shortens
the process, and it is also possible to control the formation of
the color pattern and thus obtain a color filter that is
inexpensive but of a high quality.
[0004] In such a method of making a color filter using an inkjet
method, one means that has been proposed to prevent ink from
spreading outside of each colored region, and thus implement highly
precise coloring, is to use pixel delimiting regions that are
formed previously by photolithography on the substrate. Ink filling
concavities are thus formed on the substrate by the pixel
delimiting regions, to control the shape of a color pattern that is
formed by filling these ink filling concavities with ink.
[0005] These pixel delimiting regions are often formed of an opaque
material so that they also function as a black matrix (hereinafter
abbreviated to BM).
[0006] In this case, a high level of precision is required for the
formation of the pixel delimiting regions, but it is difficult to
perform such highly precise processing while improving the
mass-productivity of the process. In addition, flatness is required
when forming a transparent electrode on the color filter, but it
has been difficult to increase the precision of this flatness in
the past.
[0007] The present invention has been devised in order to solve the
above problems, and has the objective of providing a method of
making an inexpensive, highly precise color filter with a reduced
number of steps, as well as a color filter fabricated by that
method.
DISCLOSURE OF INVENTION
[0008] A method of making a color filter in accordance with the
present invention comprises: a first step of fabricating a template
having a plurality of protrusions in a predetermined array;
[0009] a second step of transfer-forming an ink filling layer
having a plurality of ink filling concavities by causing an ink
filling layer precursor to adhere to the template, solidifying the
ink filling layer precursor to form the ink filling layer, then
separating the ink filling layer from the template; and
[0010] a third step of filling the ink filling cavities with inks
of previously determined colors, to form a color pattern layer.
[0011] In other words, the present invention uses a template as a
mold to transfer-form an ink filling layer having ink filling
concavities. Once this template has been fabricated, it can be used
a number of times limited by the durability thereof. Therefore step
can be omitted from the process of forming the second and
subsequent color filters, thus reducing the number of steps and the
cost.
[0012] Specific methods of fabricating the template are described
below.
[0013] (1) A step of forming a resist layer of a predetermined
pattern on a substrate, then forming the protrusions on the
substrate by etching to obtain the template.
[0014] This step makes it possible to control the shape and surface
roughness of the protrusions in a highly precise and also
unrestricted manner, by varying the etching conditions.
[0015] A silicon wafer is preferably used as this substrate. The
technique of etching a silicon wafer is used as a technique in the
fabrication of semiconductor devices, and enables highly precise
processing.
[0016] (2) A step of forming a resist layer of a predetermined
pattern on a base plate, then making the base plate and the resist
layer conductive, and further using electrodeposition to deposit
metal by an electroplating method to form a metal layer, and
finally separating the metal layer from the base plate and the
resist layer to obtain the template.
[0017] A metal template obtained by this step generally has
superlative durability and separability.
[0018] This ink filling layer precursor is preferably a material
which can be hardened by the application of energy. The use of such
a material makes it possible for the material that forms the ink
filling layer to easily fill as far as the most detailed parts of
the concavities in the template, so that the shape of the
protrusions on the template can be transferred accurately to form
the ink filling concavities.
[0019] The energy is preferably at least one of light and heat.
This makes it possible to use a general-purpose exposure apparatus,
baking oven, or hotplate, enabling reductions in equipment costs
and installation space.
[0020] A resin which is hardened by ultraviolet rays is an example
of such a material. An acrylic resin has superlative transparency
as a resin which is hardened by ultraviolet rays, and it is
suitable because various commercially available resins and
photosensitive materials can be used therefor.
[0021] Next, the ink is preferably injected by an inkjet method in
the third step. The use of an inkjet method enables rapid
application of the ink and there is also no waste of such ink.
[0022] In a further aspect of the present invention, an opaque
material may be injected into concavities between the protrusions
of the template after the first step but before the second step, to
form an opaque layer; and
[0023] the opaque layer is integrated with the ink filling layer in
the second step, by using the template on which is formed the
opaque layer.
[0024] This opaque material may also be injected by an inkjet
method.
[0025] The inner side surfaces of the concavities of the template
may be formed in a tapered shape in such a manner that the surface
area of aperture portions thereof are larger than base surfaces
thereof.
[0026] These concavities of the template may also be formed in a
tapered shape at aperture edge portions of inner side surfaces
thereof.
[0027] If the concavities are formed in a tapered shape in this
manner, the inks can be guided reliably into the concavities, thus
making the color filter particularly suitable for use in a
high-resolution liquid crystal panel. In addition, this
configuration reduces any difference in thickness of the color
pattern layer, thus reducing unevenness in color caused by factors
such as differences in color tone or brightness, and thus making it
possible to fabricate a color filter that provides a bright
image.
[0028] Another method of making a color filter in accordance with
the present invention comprises: a first step of forming a
plurality of colored layers;
[0029] a second step of placing a precursor of a protective film on
the colored layers; and
[0030] a third step of forming a protective film precursor layer by
flattening a surface of the protective film precursor with a
template having a flat surface corresponding to at least an
optically transparent region (filter element) of the colored
layers, then hardening the protective film precursor layer to form
a protective film. This method makes it possible to form the
surface of the protective film to be flat.
[0031] With the present invention, at least one concavity could be
provided in a surface of the template corresponding to a region
other than an optically transparent region of the colored
layers;
[0032] the shape of the concavities of the template is transferred
to the protective film precursor layer in the third step, to form
protrusions in the protective film corresponding to the
concavities; and
[0033] the protrusions act as support members (spacer) for
maintaining a constant spacing (cell gap) for injecting liquid
crystal into a liquid crystal panel (liquid crystal cell). This
method makes it possible to form support members simultaneously
with the protective film, and also easily adjust the positions at
which the support members are disposed.
[0034] In this aspect of the invention, the second step could cause
the concavities of the template to be positioned above and between
the colored layers.
[0035] This forms support members between the colored layers. In
addition, if an opaque layer (black matrix) is formed between the
colored layers, protrusions that act as support members could be
positioned on top of this opaque layer. For example, the opaque
layer could be formed as a lattice, with the support members formed
at intersection points of this lattice. Since this method makes it
possible to not form support members on the colored layers, it
enables an improvement in yield and also simplifies the fabrication
process.
[0036] The concavities could also be formed in a circular
cylindrical shape. This causes the protrusions that act as support
members to have a circular cylindrical shape, making it possible to
suppress disturbances in the orientation of the liquid crystal and
increase the contrast of the liquid crystal panel display.
[0037] It is preferable that the protective film precursor is a
material which can be hardened by the application of energy. This
energy may be at least one of light and heat, for example. The
protective film precursor could be a resin which is hardened by
ultraviolet rays.
[0038] With this aspect of the invention, a transparent electrode
film could be previously formed on the template; and
[0039] after the transparent electrode film is placed in contact
with the protective film precursor, the protective film precursor
layer is formed by the template, and the protective film precursor
is hardened to form a protective film in the third step, the
template is separated from the protective film precursor layer,
leaving the transparent electrode remaining on the protective film
precursor layer. This makes it possible to form the transparent
electrode film in a simple manner.
[0040] A separation layer could also be formed between the template
and the transparent electrode film, to promote the separation of
the two components. This facilitates the removal of the template
from the protective film precursor, leaving the transparent
electrode film.
[0041] A color filter in accordance with the present invention
comprises an ink filling layer having a plurality of ink filling
concavities; and a color pattern layer formed in the ink filling
cavities; and
[0042] wherein the ink filling layer is formed by causing a
template having a plurality of protrusions in a predetermined array
to adhere to an ink filling layer precursor, then solidifying the
ink filling layer precursor.
[0043] Another color filter in accordance with the present
invention comprises a plurality of colored layers; and a protective
film formed on the colored layers; and
[0044] wherein the protective film is formed by flattening a
surface of the protective film precursor with a template having a
flat surface corresponding to at least an optically transparent
region of the colored layers, then hardening the protective film
precursor layer.
BRIEF DESCRIPTION OF DRAWINGS
[0045] FIGS. 1A to 1F illustrate the process of making a template
of a first embodiment of the present invention;
[0046] FIGS. 2A to 2E illustrate the process of making a color
filter of the present embodiment of the invention;
[0047] FIG. 3 illustrates the process of making a color pattern
layer of the present embodiment of the invention;
[0048] FIGS. 4A to 4C illustrate the process of fabricating a
template of a second embodiment of the present invention;
[0049] FIGS. 5A to 5C illustrate the rest of the process of
fabricating the template of the second embodiment of the present
invention;
[0050] FIG. 6 is a plan view of a color filter made in accordance
with a third embodiment of the present invention;
[0051] FIGS. 7A to 7E illustrate the process of fabricating a
template of a third embodiment;
[0052] FIGS. 8A to 8D illustrate the process of fabricating a color
filter of the present invention;
[0053] FIG. 9 illustrates in detail the process of filling an
opaque material;
[0054] FIG. 10 illustrates in detail the process of filling colored
inks;
[0055] FIGS. 11A to 11C illustrate the process of fabricating a
template of a fourth embodiment;
[0056] FIGS. 12A to 12C illustrate the rest of the process of
fabricating the template of the fourth embodiment;
[0057] FIGS. 13A and 13B illustrate a state in which opaque ink
fills an ordinary template;
[0058] FIGS. 14A and 14B illustrate a state in which opaque ink
fills a template of a fifth embodiment;
[0059] FIGS. 15A and 15B illustrate a state in which opaque ink
fills a modification of the template of the fifth embodiment;
[0060] FIGS. 16A to 16C illustrate the process of fabricating a
color filter of a sixth embodiment;
[0061] FIGS. 17A to 17C further illustrate the process of
fabricating the color filter of the sixth embodiment;
[0062] FIGS. 18A to 18C further illustrate the process of
fabricating the color filter of the sixth embodiment;
[0063] FIGS. 19A to 19C illustrate the rest of the process of
fabricating the color filter of the sixth embodiment;
[0064] FIGS. 20A to 20C illustrate the process of fabricating a
color filter of a seventh embodiment;
[0065] FIGS. 21A to 21C illustrate the rest of the process of
fabricating the color filter of the seventh embodiment;
[0066] FIGS. 22A to 22C illustrate arrangement patterns of the
colored layers R, G, and B (filter elements);
[0067] FIGS. 23A to 23C illustrate the process of fabricating a
template provided with concavities in the surface thereof;
[0068] FIGS. 24A and 24B illustrate the rest of the process of
fabricating a template provided with concavities in the surface
thereof;
[0069] FIGS. 25A and 25B illustrate the process of fabricating a
color filter of an eighth embodiment;
[0070] FIGS. 26A and 26B illustrate a ninth embodiment of the
present invention;
[0071] FIGS. 27A to 27C illustrate separation states of the ninth
embodiment; and
[0072] FIG. 28 is a cross-sectional view through a liquid crystal
panel.
BEST MODE FOR CARRYING OUT THE INVENTION
[0073] Preferred embodiment of the present invention are described
below with reference to the accompanying drawings.
First Embodiment
[0074] The process of making a template of a first embodiment of
the present invention is shown in FIGS. 1A to 1E. This method is
described in detail below.
[0075] First of all, as shown in FIG. 1A, a resist layer 20 is
formed on a substrate 19.
[0076] The surface of the substrate 19 will be etched to form a
template, and a silicon wafer is used in this case. The technology
of etching a silicon wafer is established in the art of making
semiconductor devices and enables highly precise etching to be
carried out. It should be noted that as long as the substrate 19 is
of a material which can be etched, it is not restricted to being a
silicon wafer, and for example a plate or film of glass, quartz,
resin, metal, ceramic, or other material may be used therefor.
[0077] As the material forming the resist layer 20, it is possible
to use a commercially available positive resist such as that
generally used in the fabrication of semiconductor devices, being a
cresol novolac type resin to which a diazonaphthoquinone derivative
is added as a photosensitive material. Here, positive resist refers
to a substance which can be selectively removed by developer in an
area which is exposed to radiation in accordance with a
predetermined pattern.
[0078] As the method of forming the resist layer 20, it is possible
to use a spin-coating, dipping, spray-coating, roll-coating, or
bar-coating method, for example.
[0079] Next, as shown in FIG. 1B, a mask 21 is disposed on the
resist layer 20, and selected regions only of the resist layer 20
are exposed through the mask 21 to radiation 22 to form
radiation-exposed regions 23.
[0080] The mask 21 is patterned so as to pass the radiation 22 only
in those regions that do not correspond to protrusions 13 shown in
FIG. 1E.
[0081] These protrusions 13 are intended to function as a means of
transferring ink filling concavities 15 for forming each color
pattern layer 16 (see FIG. 2E) for the color filter being
fabricated, and are formed to correspond to the form and layout of
the color pattern layer 16. For a 10-inch VGA type of liquid
crystal panel, for example, approximately 900,000 pixels (for
640.times.480.times.3 colors), or in other words approximately
900,000 protrusions 13, are formed at a pitch of approximately 100
.mu.m on the template.
[0082] Light of a wavelength in the region of 200 nm to 500 nm is
preferably used as this radiation. The use of light in this
wavelength region makes it possible to utilize photolithography
techniques and the equipment therefor that have been established
for the process of manufacturing liquid crystal panels or the like,
thus reducing costs.
[0083] After the resist layer 20 has been exposed to the radiation
22, developing is carried out under predetermined conditions, and,
as shown in FIG. 1C, the resist in the radiation-exposed regions 23
only is selectively removed, exposing the substrate 19, while other
regions remain covered by the resist layer 20.
[0084] When the resist layer 20 is patterned in this way, as shown
in FIG. 1D, with the resist layer 20 as a mask, the substrate 19 is
etched to a particular depth.
[0085] The method of etching may be wet etching or dry etching,
but, depending on the material of the substrate 19, the method of
etching and the conditions may be chosen to be optimum from a
consideration of the cross-sectional shape of the etching, the
etching rate, surface uniformity, and so forth. For
controllability, a dry method is superior, and a device using a
parallel flat plate reactive ion etching (RIE) method, inductive
coupled plasma (ICP) method, electron cyclotron resonance (ECR)
method, helicon wave excitation method, magnetron method, plasma
etching method, ion beam etching method, or the like may be used,
by way of example, and, by varying the type of etching gas, the gas
flow rate, the gas pressure, the bias voltage, and other
conditions, the protrusions 13 may be formed in an rectangular
shape, a taper may be applied, or the surface may be made rough, to
obtain any desired etching shape.
[0086] Next, after etching is completed, the resist layer 24 is
removed as shown in FIG. 1E, and the substrate 19 having the
protrusions 13 is obtained, and this forms a template 12. The
processing after the template 12 is obtained is shown in FIGS. 2A
to 2E.
[0087] First of all, a reinforcing plate 10 is attached to the
template 12 with an ink filling layer precursor 11
therebetween.
[0088] A glass substrate is generally used as the reinforcing plate
10, but it is not specifically limited thereto provided it can
satisfy conditions such as optical transmissivity and mechanical
strength that are required of a color filter. The reinforcing plate
10 may, for example, be a plate or film of a plastic material such
as a polycarbonate, polyarylate, polyether sulfone, amorphous
polyolefin, polyethylene terephthalate, or polymethyl
methacrylate.
[0089] The ink filling layer precursor 11 is not particularly
limited, provided it has sufficient optical transmissivity such
that the color characteristics of the color pattern layer 16 are
not lost at the thickness of color pattern layer formation regions
17 shown in FIG. 2E, and various materials may be used therefor,
but it is preferable that a material that can be hardened by the
application of energy is used. Such a material can be handled as a
low-viscosity liquid during the formation of a ink filling layer
14, and can readily flow into the most detailed portions of
concavities formed between the template 12 and the protrusions 13
at a normal temperature and a normal pressure.
[0090] The energy applied thereto is preferably at least one of
light and heat. This makes it possible to use a general-purpose
exposure apparatus, baking oven, or hotplate, enabling reductions
in equipment costs and installation space.
[0091] An example of this material is a resin which is hardened by
ultraviolet rays. Acrylic resins are suitable examples of such
resins that are hardened by ultraviolet rays. The use of various
commercially available resins and photosensitive materials makes it
possible to obtain an acrylic resin which has superlative
transparency and which can also be hardened by a short application
of ultraviolet rays.
[0092] As specific instances of the basic composition of acrylic
resins hardened by ultraviolet rays may be cited prepolymers,
oligomers, monomers, and optical polymerization initiators.
[0093] As prepolymers or oligomers may be used, for example,
acrylate-based substances such as epoxy acrylates, urethane
acrylates, polyester acrylates, polyether acrylates, and
spiroacetal acrylates; or methacrylate-based substances such as
epoxy methacrylates, urethane methacrylates, polyester
methacrylates, and polyether methacrylates.
[0094] As monomers may be used, for example, monofunctional
monomers such as 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate,
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
N-vinyl-2-pyrrolidone, carbitol acrylate, tetrahydrofurfuryl
acrylate, isobornyl acrylate, dicyclopentenyl acrylate, and
1,3-butanediol acrylate; bifunctional monomers such as
1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate,
neopentylglycol diacrylate, neopentylglycol dimethacrylate,
ethylene glycol diacrylate, polyethylene glycol diacrylate, and
pentaerythritol diacrylate; and polyfunctional monomers such as
trimethylol propane acrylate, trimethylol propanetri methacrylate,
pentaerythritol triacrylate, and dipentaerythritol hexacrylate.
[0095] As optical polymerization initiators may be used, for
example, acetophenones such as 2,2-dimethoxy-2- phenylacetophenone;
butylphenones such as .alpha.-hydroxyisobutylphenone and
p-isopropyl-.alpha.-hydroxyiso- butylphenone; halogenated
acetophenones such as p-tert-butyldichloroacetop- henone,
p-tert-butyltrichloroacetophenone, and .alpha.,.alpha.-dichloro-4--
phenoxyacetophenone; benzophenone compounds such as benzophenone
and N,N-tetraethyl-4,4-diaminobenzophenone; benzyl compounds such
as benzyl and benzyl dimethyl ketals; benzoin compounds such as
benzoin and benzoin alkylethers; oxime compounds such as
1-phenyl-1,2-propanedion-2-(o-ethoxy- carbonyl) oxime; xanthone
compounds such as 2-methylthioxanthone and 2-chlorothioxanthone;
benzoin ethers such as benzoin ether and isobutyl benzoin ether;
and radical generating compounds such as Michler's ketone.
[0096] It should be noted that, if necessary to prevent impairment
of hardening by oxygen, amines or other compounds may be added,
and, to facilitate the painting, a solvent ingredient may be
added.
[0097] There is no particular restriction on the solvent ingredient
added, and various organic solvents may be used either singly or in
combination, such as, for example, propylene glycol monomethyl
ether acetate, propylene glycol monomethyl ether, methoxy methyl
proprionate, ethyl cellosolve, ethyl cellosolve acetate, ethyl
lactate, ethyl pyruvinate, ethyl amyl ketone, cyclohexanone,
xylene, toluene, or butyl acetate.
[0098] A predetermined amount of the ink filling layer precursor
11, consisting of such an acrylic resin hardened by ultraviolet
rays or the like, is dropped onto the reinforcing plate 10, as
shown in FIG. 2A.
[0099] The template 12 is then pressed onto the reinforcing plate
10 with the ink filling layer precursor 11 therebetween, as shown
in FIG. 2B, and, after the ink filling layer precursor 11 has
spread over a predetermined region, ultraviolet rays are shone
thereon from the reinforcing plate 10 side for a predetermined time
to harden the ink filling layer precursor 11 and thus form the ink
filling layer 14 between the reinforcing plate 10 and the template
12, as shown in FIG. 2C.
[0100] To ensure that the ink filling layer precursor 11 spreads
over the predetermined region, a predetermined pressure may be
applied to the template 12 if necessary.
[0101] In the above case, the ink filling layer precursor 11 is
dropped onto the reinforcing plate 10, but it may equally well be
dropped onto the template 12 or onto both the reinforcing plate 10
and the template 12.
[0102] Alternatively, the ink filling layer precursor 11 may be
applied over one or both of the reinforcing plate 10 and the
template 12 by using a spin-coating method, dipping method,
spray-coating method, roll-coating method, bar-coating method, or
the like.
[0103] The reinforcing plate 10 and the ink filling layer 14 are
then removed from the template 12 as an integral unit, as shown in
FIG. 2D, to obtain the reinforcing plate 10 on which is formed ink
filling layer 14 having the ink filling concavities 15 in the
surface thereof.
[0104] After the ink filling concavities 15 is thus formed on the
reinforcing plate 10, each of the ink filling concavities 15 is
filled with a predetermined colored ink as shown in FIG. 2E, to
form the color pattern layer 16.
[0105] There are no particular restrictions on the method used to
fill the ink filling concavities 15 with colored inks, but an
inkjet method is preferred. With an inkjet method, the practical
technology that has been developed for inkjet printers can be
employed, enabling the filling operation to be carried out rapidly
and economically, with no ink waste.
[0106] FIG. 3 shows the ink filling concavities 15 being filled
with inks 26, such as red ink R, green ink G, and blue ink B, by an
inkjet head 25.
[0107] The head 25 is disposed facing the ink filling concavities
15 on the reinforcing plate 10, and the colored inks 26 are ejected
into the ink filling concavities 15 by the head 25.
[0108] The head 25 is for example one developed for an inkjet
printer, and may for example be a Piezo Jet Type employing a
piezoelectric element, or a Bubble Jet Type employing
electrothermal conversion as an energy producing element, and the
color areas and color pattern can be determined as required.
[0109] For example, if the head 25 has twenty ink-ejecting nozzles
for each of R, G, and B, and a drive frequency of 14.4 kHz (14400
ejection cycles per second), then if three drops of ink are ejected
into each of the ink filling concavities 29, to eject ink into the
ink filling concavities 15 of a 10-inch VGA type of color filter
having approximately 900,000 pixels, the time required is:
900,000.times.3 drops/(144000 cycles.times.20 nozzles.times.3
colors) =approximately 3 seconds
[0110] In this case, even when the time for the head 25 to move
from one ink filling concavity 15 to the next is included, all of
the ink filling concavities 15 can be filled with the colored inks
26 in about 2 or 3 seconds.
[0111] The inclusion of a solvent component in the colored inks 26
ensures that the solvent of the ink is evaporated by thermal
processing.
[0112] In this way, as shown in FIG. 2E, the color pattern layer 16
is formed on the reinforcing plate 10, to obtain the completed
product 18 of a color filter.
[0113] In the above embodiment, a positive resist is used when the
protrusions 13 are formed on the template 12, but equally a
negative resist, such that regions exposed to radiation are
rendered insoluble in a developer, and the regions not exposed to
radiation are selectively removed by the developer, may be used; in
that case, the mask used has a pattern which is the inverse of the
pattern of the mask 21. Alternatively, instead of using a mask, a
laser beam or electron beam may be used to directly expose the
resist in a pattern.
Second Embodiment
[0114] The process of fabricating a template of a second embodiment
of the present invention is shown in FIGS. 4A to 5C.
[0115] First, as shown in FIG. 4A, the resist layer 20 that forms a
predetermined pattern is formed on a base plate 27.
[0116] The base plate 27 is not restricted as long as it can
fulfill the role of a support during the patterning of the resist
layer 20 by lithography, it has properties such as the mechanical
strength and chemical resistance necessary for the processing, and
it has good wettability and adhesiveness with respect to the
material forming the resist layer 20; for example, a substrate of
glass, quartz, resin, silicon wafer, metal, ceramic, or other
material may be used as the base plate 27. A glass template is used
in this case, with the surface thereof being polished to a flat
using a cerium oxide type of polishing agent, then washed and
dried.
[0117] Since the material and method used for forming the resist
layer 20 can be the same as those described with reference to the
first embodiment, further description thereof is omitted.
[0118] Next, as shown in FIG. 4B, a mask 28 is disposed on the
resist layer 20 and predetermined regions only of the resist layer
20 are exposed through the mask 28 to the radiation 22 to form the
radiation-exposed regions 23.
[0119] The mask 28 is formed in a pattern such that the radiation
22 passes only through regions corresponding to the concavities 29,
as shown in FIG. 4C.
[0120] The concavities 29 act as indentations for forming the
protrusions 13 of the template 12 (see FIG. 1E). The protrusions 13
of the template 12 are designed as a transfer formation for the ink
filling concavities 15 (see FIG. 2D) for forming the color pattern
layer 16 of the color filter (see FIG. 2E). Therefore, the
concavities 29 have the same shape and arrangement as the ink
filling concavities 15, in other words, they are formed to
correspond to the shape and arrangement of the color pattern layer
16 of the color filter to be fabricated.
[0121] Light of a wavelength in the region of 200 nm to 500 nm is
preferably used as this radiation. The use of light in this
wavelength region makes it possible to utilize photolithography
techniques and the equipment therefor that have been established
for the process of manufacturing liquid crystal panels or the like,
thus reducing costs.
[0122] If development is performed under predetermined conditions
after the exposure to the radiation 22, only the resist on the
radiation-exposed regions 23 is selectively removed, as shown in
FIG. 4C, to pattern the resist layer 20 and thus form the
concavities 29 on top of the base plate 27.
[0123] Next, a conductive layer 30 is formed on the resist layer 20
and the base plate 27 as shown in FIG. 5A, to make the surfaces
thereof conductive.
[0124] As the conductive layer 30, Ni formed to a thickness of 500
to 1000 Angstroms (10.sup.-10m) may be used. for example. The
method of forming the conductive layer 30 may be a method such as
sputtering, CVD, vapor deposition, or nonelectrolytic plating.
[0125] Then, using the base plate 27 and the resist layer 20, which
have been made conductive by the conductive layer 30, as the
cathode and a tip-shaped or ball-shaped Ni as the anode,
electroplating is further carried out to electrically deposit Ni to
make a metal layer 31, as shown in FIG. 5B.
[0126] The following is a specific example of the electrolyte that
may be used:
1 Nickel sulfamate 900 g/l Boric acid 60 g/l Nickel chloride 8 g/l
Leveling agent 30 mg/l
[0127] Next, the conductive layer 30 and the metal layer 31 are
separated from the base plate 27, as shown in FIG. 5C, and are
washed if necessary, to form the template 12.
[0128] Note that the conductive layer 30 may be removed from the
metal layer 31 by performing separating processing, if
necessary.
[0129] Once the template 12 is obtained in this manner, the color
filter can then be obtained by the steps shown in FIG. 2
[0130] In the present embodiment too, a negative resist may also be
used, in which case a mask having a pattern that is the inverse of
the mask 28 may be used, in other words, a mask that is the same as
the mask 21 of FIG. 1B. Alternatively, no mask is used and the
resist is exposed directly in a pattern by laser light or an
electron beam.
[0131] Once the template 12 has been fabricated by the above
described method of making a color filter, it can be used a number
of times limited only by its endurance to fabricate two or more
color filters, thus reducing the number of steps and the cost.
[0132] A BM or over-coating layer is subsequently formed on top of
the color pattern layer 16 if necessary, a transparent electrode
and an orientation film are attached thereto, and it is installed
into an array
Third Embodiment
[0133] A third embodiment of the present invention is intended to
fabricate a color filter by a small number of steps, whereby an
opaque layer, in other words, a black matrix is formed by providing
ink filling layers after a template has been filled with an opaque
material.
Color Filter Fabrication
[0134] A plan view of a color filter fabricated by the method of
the present invention is shown in FIG. 6. As shown in this figure,
a color filter 101 of the present invention is provided with color
pattern layers 111R, 111G, and 111B within pixel aperture portions
that are separated by an opaque layer 115 formed on an ink filling
layer 110.
[0135] The ink filling layer 110 may be formed of a material such
as resin, for example, with the opaque layer 115 (see FIG. 10) that
is formed of an opaque material being provided on a surface thereof
(the surface that can be seen in FIG. 6).
[0136] The color pattern layers 111R, 111G, and 111B combine color
pattern layers of a plurality of primary colors to form individual
color pixels. In the present embodiment, pixels of a color pattern
layer (red) 111R, a color pattern layer (green) 111G, and a color
pattern layer (blue) 111B are arrayed to form individual color
pixels, to form color pixels from the three primary colors of red,
green, and blue. The color pixels in this figure are shown as an
array of five columns by four rows, to simplify the description,
but the pixel arrangement in a real-life product will match the
resolution of the liquid crystal panel.
[0137] These color pattern layers 111R, 111G, and 111B are formed
by injecting colored inks that are transparent. The pixels are
arrayed at a pitch of, for example, approximately 100 .mu.m.
[0138] Note that the arrangement of pixels and the pattern of the
ink filling layer 110 are not limited to those shown in FIG. 6;
they can be implemented in various different forms corresponding to
the pixel array of the liquid crystal panel.
[0139] If a color filter of the above described configuration is
installed in a liquid crystal panel, light from each pixel of the
liquid crystal panel will pass through and shine from one of the
color pattern layers 111R, 111G and 111B. A color display is
achieved by attaching the color filter to a liquid crystal panel
with the colors of the color pattern layers 111R, 111G, and 111B in
the color filter placed in correspondence with the color
disposition of pixels in the liquid crystal panel.
Fabrication Method
[0140] The method of making a color filter in accordance with the
present embodiment will now be described with reference to FIGS. 7A
to 10. These figures are schematic cross-sectional views of the
fabrication process, taken along the line A-A of FIG. 6.
Template Fabrication
[0141] When it comes to fabricating the color filter of the present
invention, a template used for transferring the shape of the color
pattern layers of the color filter is first formed. FIGS. 7A to 7E
are cross-sectional views of the fabrication process, illustrating
the method of fabricating the template.
Resist Layer Formation Step (FIG. 7A)
[0142] In a resist layer formation step, a resist layer 121 is
formed on a substrate 120. Silicon or quartz is preferably used as
the material of the substrate 120.
[0143] Of resist materials used to configure the resist layer 121,
a negative material is one that is converted into a hard film that
is made not soluble in a developer by illuminating it with light of
at least a certain strength, and a positive material is one that is
made readily soluble to a developer by illuminating it with light
of at least a certain strength. A positive resist material is used
in the present embodiment.
[0144] The method used for making the resist layer 121, is not
particularly limited. For example, a resist material could be
coated to a thickness of approximately 1 .mu.m on the substrate 120
by a spin-coating method, then it is fixed by thermal processing to
form the resist layer 121.
Exposure Step (FIG. 7B)
[0145] In an exposure step, the resist layer 121 is covered with a
mask 123 in accordance with a predetermined pattern, then light 122
is shone thereon to expose the resist.
[0146] The mask 123 is a screening member that is patterned in such
a manner that the light 122 passes therethrough only in regions
corresponding to light-exposed regions 124. This pattern is formed
in the shape of the ink filling layer 110 that separates the pixels
of the color filter 101.
Development Step (FIG. 7C)
[0147] In a development step, the resist material is removed from
the light-exposed regions 124 by development performed under fixed
conditions, after the resist layer 121 has been exposed by the
light 122. This processing selectively removes the resist material
from the light-exposed regions 124 that had been exposed to the
light 122, to reveal the substrate 120.
Etching Step (FIG. 7D)
[0148] In an etching step, concavities 114 are formed in the shape
of the ink filling layer 110, by etching the patterned resist layer
121 with an etchant 125.
[0149] A wet method or a dry method could be used as the etching
method. The optimal method and etching conditions are selected to
suit the material properties of the substrate 120 from the
viewpoints of factors such as etching cross-sectional shape,
etching rate, and surface uniformity. If control over etching depth
and shape is important, a dry method is superior.
Removal Step (FIG. 7E)
[0150] In a removal step the resist layer 121 is removed from the
substrate 120 after the etching. The concavities 114 corresponding
to the pattern shape of the mask 123 have been formed in the
substrate 120 once the resist layer 121 has been removed. In other
words, the substrate 120 becomes a template 102.
Color Filter Fabrication
[0151] The description now turns to the method of fabricating a
color filter using the template 102 formed as described above, with
reference to FIGS. 8A to 8D.
Opaque Layer Formation Step (FIG. 8A)
[0152] In a opaque layer formation step, the concavities 114 of the
template 102 are filled with an opaque material to form the opaque
layer 115 that acts as a black matrix. The opaque material could be
any of various different materials, provided it is not optically
transmissive and it is durable. For example, a black resin such as
negative resin black produced by Fuji Hanto, resist HRB-#01 for
highly insulating black matrices produced by Toppan Printing Co.,
Ltd., or resin black produced by Japan Synthetic Rubber (JSR) Co.,
Ltd. could be used dissolved in an organic solvent. In the present
embodiment, ink is ejected from an inkjet type of recording head,
so it is necessary to ensure the liquidity of the opaque material
to a certain extent. The type of organic solvent is not
particularly limited, so various different organic solvents could
be used. For example, propylene glycol monomethyl ether acetate,
propylene glycol monopropyl ether, methoxy methyl proprionate,
methoxy ethyl proprionate, ethyl cellosolve, ethyl cellosolve
acetate, ethyl lactate, ethyl pyruvinate, methyl amyl ketone,
cyclohexanone, xylene, toluene, or butyl acetate could be used
therefor, either singly on in a combination of a plurality of
substances.
[0153] The method of applying the opaque material involves ejecting
from an inkjet head 103 an opaque ink 115a consisting of an opaque
material that is dissolved or dispersed in an organic solvent, as
shown in FIG. 9. During this time, the position at which the opaque
ink 115a hits is controlled by controlling the movement of the head
103 in the direction shown by the arrows in the figure, for
example, in such a manner that a uniform quantity of the ink 115a
fills each of the concavities 114 formed in the template 102. Once
all of the concavities 114 have been filled uniformly with the ink
115a, the filling ends. If an ink 115a comprising a solvent
component is used, that solvent component is removed by thermal
processing. Note that, since the opaque layer 115 contracts due to
the removal of the solvent component, it is necessary to apply a
sufficient quantity of the ink 115a to ensure that the thickness
that remains after the contraction can ensure the required
opacity.
Ink Filling Layer Formation Step (FIG. 8B)
[0154] In an ink filling layer formation step, an ink filling layer
precursor is coated onto the template 102 on which is formed the
opaque layer 115, to form the ink filling layer 110. First of all,
the ink filling layer precursor is coated onto the surface of the
template 102 that is provided with the concavities 114. Next, after
a reinforcing plate 116 has been attached to the ink filling layer
precursor coated on the template 102, hardening processing is
performed to correspond to the ink filling layer precursor that is
used, to form the ink filling layer 110. If, for example, a resin
that is hardened by ultraviolet rays is used for the ink filling
layer precursor, ultraviolet rays are shone from the reinforcing
plate 116 side for a predetermined time to cause the resin to
harden and thus form the ink filling layer 110.
[0155] Any well-known method can be used for coating the ink
filling layer precursor, such as a spin-coating method,
dipping-method, spray-coating method, roll-coating method, or
bar-coating method.
[0156] In this case, it is preferable that the ink filling layer
precursor that is coated onto the template 102 is a material that
is hardened by the application of at least one of light and heat.
This makes it possible to use a general-purpose exposure apparatus,
baking oven, or hotplate, enabling reductions in equipment costs
and installation space.
[0157] A resin that is hardened by ultraviolet rays is particularly
preferable as the material of the ink filling layer 110. More
specifically, it is preferable to use an acrylic resin that is
hardened by ultraviolet rays, as it is commercially available on
the market and a photosensitive material is easy to obtain.
[0158] Since the reinforcing plate 116 is used with the objective
of reinforcing the color filter, it is selected in accordance with
the color filter that is to be fabricated. A substance that has a
suitable mechanical strength and also has a high level of optical
transmissivity to enable sufficient light from the display panel to
pass therethrough may be used as the reinforcing plate 116. For
example, a glass substrate or a substrate or film of a plastic such
as a polycarbonate, polyacrylate, polyether sulfone, amorphous
polyolefin, polyethylene terephthalate, or polymethyl methacrylate
could be used as the reinforcing plate 116.
[0159] Note that, if the reinforcing plate 116 is not necessary for
strengthening the color filter, it may be separated therefrom.
Separation Step (FIG. 8C)
[0160] In a separation step, the hardened ink filling layer 110 is
separated from the template 102. Once the ink filling layer 110 is
sufficiently hardened, the ink filling layer 110 is firmly attached
to the reinforcing plate 116 and the ink filling layer 110 is also
firmly attached to the opaque layer 115. Therefore, if the
reinforcing plate 116 is peeled off from the template 102, the
reinforcing plate 116, the ink filling layer 110, and the opaque
layer 115 will be removed as an integral assembly.
Color Pattern Layer Formation Step (FIG. 8D)
[0161] In a color pattern layer formation step, the ink filling
concavities 117 of the ink filling layer 110 that has been
separated from the template 102 are filled with colored inks 111a,
to form a color pattern layer 111.
[0162] The method used for applying the colored inks 111a is not
particularly limited, but an inkjet method that ejects inks from a
head could be used therefor. The colored inks ejected from the head
may be those that are transparent when dry. When ejected from a
head, it is particularly preferable that these inks have a low
viscosity and a high density, and they are fabricated of colored
pigments or dyestuffs that are mixed into an organic solvent or
water.
[0163] With an inkjet method, the inkjet head 103 ejects the
colored inks 111a corresponding to the primary colors, as shown in
FIG. 10, so that the colored inks 111a fill the ink filling
concavities 117 for forming the pixels allocated to each of the
colors. In this figure, a red colored ink R, a green colored ink G,
and a blue colored ink B each hit neighboring columns, by way of
example. In an example of the sequence of this filling, the inks
fill one column of color pixels while the head reciprocates from in
front of this figure towards the rear thereof, then the head moves
in the direction of the arrows in the figure and inks fill the
neighboring column of color pixels. Repetition of this sequence
makes it possible to form the color pattern layer 111 in the ink
filling concavities 117.
[0164] Once the colored inks 111a have been applied, the solvent
component within the colored inks 111a is evaporated by thermal
processing to solidify them. This thermal processing is done by
using a heater, for example, to heat the reinforcing plate 116 to a
predetermined temperature (such as approximately 70.degree. C.).
The volume of the color pattern layer 111 formed by the evaporation
of the solvent from the colored inks 111a is less than before the
solvent was evaporated, as shown in FIG. 8D. If this decrease in
volume is too dramatic, the process of ejecting and heating the
colored inks 111a can be repeated until the thickness of the ink
film is sufficient for a color filter. This processing ensures that
the solvent evaporates from the colored inks 111a until finally
only the solid portions of the colored inks 111a, to form the color
pattern layer 111.
[0165] After the color pattern layer 111 has been formed, heating
is performed at a predetermined temperature (for example,
120.degree. C.) for a predetermined time (for example,
approximately 20 minutes) in order to dry out the colored inks 111a
completely, then a predetermined resin is used to form a protective
film (not shown in the figure) to protect and flatten the filter
surface. Finally, if transparent electrode are provided on the
protective film, the color filter 101 of the present invention is
completed.
[0166] Note that colored inks in three primary colors are used in
the above embodiment to fabricate the color filter, but other
primary colors could also be used, depending on factors such as
whether an additive color process or a subtractive color process is
employed. In addition, instead of a color filter, this process can
be used to fabrication a single-color display filter or a display
filter that blocks the effects of ultraviolet rays or the like, by
using a colored ink of a single color or an ink in which is mixed a
material that has the effect of blocking ultraviolet rays or the
like.
[0167] The resist layer 121 was described above as being formed of
a positive resist, but a negative resist could equally well be
used. In such a case, a mask is used wherein the relationship
between exposed portions and non-exposed portions is the inverse of
that of the mask 123.
[0168] The exposure method could be such that no mask is used and
the resist is exposed directly in a pattern by laser light or an
electron beam.
[0169] Since the ink filling layer 110 that separates the pixels of
the color filter 101 is formed in the present embodiment by a
transfer method after the opaque ink 115a has been applied, as
described above, the opaque layer 115 and the ink filling layer 110
(the separating member) can be fabricated simultaneously. This
means that the efficiency of use of materials is higher than that
of the conventional art, and also the number of steps can be
reduced. It is therefore possible to reduce the cost of the color
filter to less than that in the conventional art.
[0170] In addition, once the template 102 has been fabricated, it
can be used repeatedly within the limits of its durability, so that
the process of making the template 102 can be omitted for the
second and subsequent filters, further reducing the number of steps
and thus making it possible to reduce the cost of color filters
even further.
Fourth Embodiment
[0171] A fourth embodiment of the present invention provides
another method of fabricating the template for the above described
third embodiment.
[0172] In the present embodiment, the fabrication process other
that the steps for forming the template are the same as those of
the third embodiment, so further description thereof is
omitted.
[0173] Cross-sectional views illustrating the method of fabricating
the template in accordance with this fourth embodiment are shown in
FIGS. 11A to 12C.
Resist Layer Formation Step (FIG. 11A)
[0174] In the resist layer formation step, a resist layer 131 is
formed on a base plate 130. The material of the base plate 130 is
not restricted so long as it can fulfill the role of a support
during the patterning of the resist layer 131 by lithography, it
has properties such as the mechanical strength and chemical
resistance necessary for the processing, and has good wettability
and adhesiveness with respect to the resist layer 131. For example,
a material such as glass, quartz, silicon wafer, resin, metal, or
ceramic could be used as the base plate 130. A glass template is
used in the present embodiment, with the surface thereof being
polished to a flat using a cerium oxide type of polishing agent,
then washed and dried.
[0175] Since the material and formation method of the resist layer
131 can be considered to be the same as in the above described
third embodiment, further description thereof is omitted.
Exposure Step (FIG. 11B)
[0176] In the exposure step, the resist layer 131 is covered with a
mask 133 in accordance with a predetermined pattern, then light 132
is shone thereon to expose the resist.
[0177] The mask 133 is a screening member that is formed in a
pattern such that the light 132 passes therethrough only in regions
corresponding to light-exposed regions 134. This pattern is formed
in to allow the light 132 to pass through in regions corresponding
to the ink filling concavities 117 of the pixel region. In other
words, the relationship between the regions through which light
passes and the regions through which light does not pass is the
inverse of that of the above third embodiment. Of course, if a
negative resist is used, this relationship is again inverted.
Development Step (FIG. 11C)
[0178] In the development step, the resist material is removed from
the light-exposed regions 134 by development performed under fixed
conditions, after the resist layer 131 has been exposed by the
light 132. This processing selectively removes the resist material
from the light-exposed regions 134 that had been exposed to the
light 132, to reveal the base plate 130.
Conductivity Step (FIG. 12A)
[0179] In a conductivity step, a conductive layer 135 is formed on
the base plate 130 to make the surface thereof conductive.
[0180] A material that is provided with electrical conductivity for
promoting the growth of a plated (metal) layer 136 as shown in FIG.
12B is sufficient as the material of the conductive layer 135, such
as Ni formed to a thickness of 500 to 1000 Angstrom (10.sup.-10m).
Any of various methods could be used for forming the conductive
layer 135, such as sputtering, CVD, vapor deposition, or
nonelectrolytic plating. Note that if it is possible to grow the
plated layer 136 without using the conductive layer 135, this step
is unnecessary.
Plated (Metal) Layer Formation Step (FIG. 12B)
[0181] In a plated layer formation step, the plated layer 136 is
grown. First of all, the resist layer 131 and the base plate 130,
which have been made conductive by the conductive layer 135 are
used as the anode and a tip-shaped or ball-shaped Ni is used as the
anode, connected to the electrodes of a plating device that is not
shown in the figures. Ni is electrodeposited by this electroplating
method to form the plated layer 136.
[0182] A plating liquid of the following composition may be used as
the electrolyte:
2 Nickel sulfamate 500 g/l Boric acid 30 g/l Nickel chloride 5 g/l
Leveling agent 10 mg/l
Separation Step (FIG. 12C)
[0183] In the separation step, the conductive layer 135 and the
plated layer 136 are separated from the base plate 130 and the
resist layer 131. After the separation, a template 102b can be
completed by washing it if necessary. Note that the conductive
layer 135 could be removed from the plated layer 136 by separation
processing, if necessary.
[0184] If the template 102b that has been fabricated as described
above is used as the template of the third embodiment, the color
filter of the present invention can be fabricated therefrom.
Details of the method of fabricating this color filter are similar
to those of the third embodiment.
[0185] Note that the resist layer 131 was described above as being
formed of a positive resist, but a negative resist could equally
well be used. In such a case, a mask is used wherein the
relationship between exposed portions and non-exposed portions is
the inverse of that of the mask 133
[0186] In addition, the exposure method could be such that no mask
is used and the resist is exposed directly in a pattern by laser
light or an electron beam
[0187] With the present embodiment as described above, a template
suitable for forming a color filter can be fabricated by
electroplating. The form of this template is similar to that of the
third embodiment, so it can achieve effects similar to those of the
third embodiment as described above. In addition, since the
template fabricated by the present embodiment is of metal and thus
is rigid, it is durable and also has the effect of reducing
fabrication costs even further.
Fifth Embodiment
[0188] In the above described third embodiment, the concavities 114
formed in the template 102 have inner side surfaces that are shaped
to descend at right angles, parallel to each other. In addition, if
the concavities 114 are filled with an opaque material and resin to
form the opaque layer 115 and the ink filling layer 110, the shape
of the resultant concavities 117 is also such that the inner side
surfaces thereof descend at right angles, as shown in FIG. 13B.
[0189] With concavities 114 and 117 of this shape, increasing the
pixel density of the liquid crystal panel will restrict the surface
area of aperture portions, which is thought to make it difficult
for the ink 115a forming the opaque layer 115 or the colored inks
111a (see FIG. 10) forming the color pattern layer 111 to hit
them.
[0190] Thus the inner side surface of concavities provided in the
template of the present embodiment are formed inclined, in a
tapered shape. For example, concavities 114b formed in a template
102c shown in FIG. 14A are tapered so that the inner side surfaces
thereof are inclined. If these concavities 114b have inner side
surfaces that are inclined in this manner, the surface area of each
aperture portion thereof is broader than the base surface, so that
the concavities 114b can be filled reliably with the opaque ink
115a even when the pixel density is increased. This also
facilitates the separation of an opaque layer 115b and an ink
filling layer 110b from the template 102c.
[0191] If such a template 102c is used to form the opaque layer
115b and the ink filling layer 110b, the shape of resultant
concavities 117b will also be tapered.
[0192] The configuration could also be such that tapering is
provided only at the aperture edge portions of the inner side
surfaces of the concavities 114b in the template 102c. For example,
a tapered shape could be formed only at aperture edge portions of
concavities 114c in a template 102d, as shown in FIG. 15A. If the
concavities 114c are formed in this manner so that the aperture
edge portions are tapered, the surface area of each aperture
portion of the concavities 114c is broader than the base surface
thereof, so that the concavities 114c can be filled reliably with
the opaque ink 115a even when the pixel density is increased.
[0193] In particular, if the concavities 114c provided with
tapering only at aperture edge portions are used, this has the
effect of making it difficult for color unevenness to occur at
peripheral regions of a color pattern layer 111c within the side
walls of an ink filling layer 110c transferred from these
concavities 114c. In other words, the ink filling layer 110c that
is transferred from the concavities 114c provided with a tapered
shape only in aperture edge portions thereof will have tapering
only at the bases of the side walls thereof, as shown in FIG. 15B.
If this color pattern layer 111c is viewed from the observation
direction (from above, in these figures), there is only a small
difference between the thickness d2 of the color pattern layer 111c
at portions that are tapered and the thickness d1 thereof at
portions some distance from the bases of the side walls. Since any
difference in thickness in the color pattern layer 111c is observed
as a difference in color tone or brightness, minimizing this
difference in thickness controls any color irregularities due to
differences in color tone or brightness to be as small as possible.
If the slope of the tapering at the aperture edge portions of the
concavities 114c is made gentle enough that the opaque ink 115a
(see FIG. 13A) is guided into the concavities 114c, this difference
in thickness can be reduced even further so that there is
substantially no color unevenness.
[0194] If the present embodiment is configured as described above,
the side surfaces of the concavities of the template are inclined
to form a tapered shape so that the opaque ink can be guided
reliably and easily into the concavities. This facilitates control
over the head, which has the effect of improving the yield during
manufacture. In particular, if only the aperture edge portions of
the concavities are provided with a tapered shape, this makes it
possible to suppress any color unevenness in the color filter to a
minimum.
Sixth Embodiment
[0195] The present embodiment involves a method of making a color
filter wherein a surface of a protective film is flattened to
correspond to an optically transmissive region of a colored layer
by forming a protective film with the aid of a template provided
with a surface that is flat in at least a predetermined region,
when that protective film is formed on a colored layer after that
colored layer has been formed by a pigment dispersion method. Note
that the present embodiment is not limited to a case in which the
colored layer is formed by a pigment dispersion method; it can also
be applied to color pattern layers formed in accordance with any of
the previous embodiments. In other words, the present embodiment
can be used regardless of the method used for forming the colored
layer (color pattern layer).
Color Filter Fabrication Process
[0196] The present embodiment is described below with reference to
FIGS. 16A to 16c. In this case, FIGS. 16A to 19 C are
cross-sectional views of the process of fabricating the color
filter.
Black Matrix Formation Step (FIG. 16A)
[0197] A layer that is opaque, such as a layer of chrome, is formed
to a predetermined thickness (such as 0.15 .mu.m) by a method such
as sputtering on a transparent reinforcing plate 211 that acts as a
foundation for the color filter, then a resist layer (not shown in
the figure) is further formed thereon. Next, this resist layer is
exposed in accordance with a predetermined pattern, then the resist
layer is developed to pattern. The thus patterned resist layer is
used as a mask for etching the chrome layer, then the resist layer
is removed to form an opaque patterned layer, in other words, an
opaque layer (black matrix) 213.
[0198] Note that opaque layer 213 can be configured as a deposition
of chrome and chrome oxide so that it reduces reflection by means
of light interference effect.
[0199] A polyimide resin or an acrylic resin in which is dispersed
a black dyestuff, black pigment, carbon black, or the like could be
used as the material of the opaque layer 213.
Colored Photosensitive Resin Layer R Coating Step (FIG. 16B)
[0200] A photosensitive resin that is colored red R, by dispersing
a pigment used as a coloring material in a resin such as a
polyimide, is coated on the reinforcing plate 211 on which is
formed the opaque layer 213, to form a colored photosensitive resin
layer 215a. A spin-coating method, roll-coating method, or dipping
method could be used as this coating method. The thickness of the
colored photosensitive resin layer 215a is determined by the color
characteristics that are required, and is on the order of 1 to 2
.mu.m.
Exposure Step (FIG. 16C)
[0201] Predetermined regions of the colored photosensitive resin
layer 215a are exposed through a mask 212, as shown in FIG. 16C.
The mask 212 is patterned in such a manner that light passes
therethrough only in regions corresponding to a red color pattern
of the color filter being fabricated.
Development Step (FIG. 17A)
[0202] Regions other than the light-exposed regions of the exposure
step are removed by a developer, to form a colored layer R. An
alkaline aqueous solution of tetramethyl ammonium hydroxide, sodium
hydroxide, potassium hydroxide, calcium hydroxide, or trisodium
phosphate mixed with sodium silicate could be used as the
developer.
Colored Layers G and B Formation Steps (FIG. 17B)
[0203] Colored layers G and B are formed in a similar manner to the
formation of the colored layer R, by repeating each of the colored
photosensitive resin layer coating step, exposure step, and the
development step, as shown in FIG. 178.
Protective Film Precursor Layer Formation Step (FIGS. 17C to
18B)
[0204] A protective film precursor 217a is dropped on top of the
colored layers R, G, and B, as shown in FIG. 17C. The composition
of the protective film precursor 217a is not particularly limited,
provided it can function as a protective film without affecting the
optical transmissivity and color characteristics required of the
color filter, once it is turned into the protective film, and thus
various different resin, glass, or ceramic materials can be used
therefor.
[0205] In addition, the protective film precursor 217a is
preferably of a material which can be hardened by the application
of energy. With such a property, the protective film precursor 217a
will form a solid film when turned into the protective film,
increasing the reliability of this protective film.
[0206] The energy applied thereto is preferably one or both of
light and heat. This makes it possible to use a general-purpose
exposure apparatus, baking oven, or hotplate, enabling a reduction
in equipment cost and improving the mass-productivity. The
protective film precursor 217a could be selected from the materials
that can be used for the ink filling layer precursor 11 of the
first embodiment.
[0207] A protective film precursor layer 217b is formed within a
predetermined region by attaching a template 219, which has a flat
surface corresponding at least to the colored layers R, G, and B
(filter elements), to the protective film precursor 217a that has
been dropped on the colored layer, and pressing down so as to
spread the precursor, as shown in FIG. 18B. In this case, it is
desirable that the flatness of the surface of the template 219 is
highly precise. More specifically, the roughness of the template
219 should be within .+-.0.1 .mu.m.
[0208] In this step, the protective film precursor could be
attached to the template 219 by using a method such as spin-coating
or roll-coating to apply it beforehand to either the colored layers
R, G, and B or the template 219.
Protective Film Precursor Layer Hardening Step (FIG. 18C)
[0209] After the protective film precursor layer 217b has been
formed over the predetermined region, the protective film precursor
layer 217b is hardened by processing appropriate to the material
thereof, to obtain a protective film 217c. Since an acrylic resin
hardened by ultraviolet rays is used in the present embodiment, the
protective film precursor layer 217b is hardened by illuminating it
with ultraviolet rays under predetermined conditions.
Template Separation Step (FIG. 19A)
[0210] After the protective film 217c has been formed, the template
219 is separated from the reinforcing plate 211, as shown in FIG.
19A.
Transparent Electrode Formation Step (FIG. 19B)
[0211] Next, a transparent electrode 221a is formed over the entire
surface of the protective film 217c by a well-known method such as
sputtering or vapor deposition. A material provided with both
optical transmissivity and electrical conductivity can be used as
the material of the transparent electrode 221a, such as indium tin
oxide (ITO) or a composite oxide such as indium oxide and zinc
oxide.
Patterning Step (FIG. 19C)
[0212] If metal-insulator-metal (MIM) technology, using alternate
layers of metal and an insulator, is employed as the method of
driving the liquid crystal panel, the transparent electrode 221a is
then patterned.
[0213] Alternatively, if a method such as thin film transistors
(TFTs) is used for driving the liquid crystal panel, this step is
not necessary.
[0214] The configuration of the present embodiment makes it
possible to flatten the surface of the protective film in a highly
precise manner, so that the voltage applied to common electrodes
formed on that protective film can be made uniform. If a simple
matrix drive method is used for the liquid crystal panel,
therefore, the occurrence of crosstalk can be suppressed.
[0215] In addition, the present embodiment makes it possible to
suppress variations in the surface resistance of common electrodes
(ITO film) formed on the protective film, thus making it possible
to prevent display variations in the liquid crystal panel.
Seventh Embodiment
[0216] In the present embodiment, a protective film and spacers for
a color filter are formed integrally by a template provided with
concavities at predetermined positions on a surface, and the
spacers are disposed at suitable positions.
Color Filter Formation Step
[0217] The present embodiment is described below with reference to
FIGS. 20A to 21C. In this case, FIGS. 20A to 21C are
cross-sectional views of steps in the formation of the color
filter. It should be noted, however, that since the steps up until
the formation of the opaque layer (black matrix) and the colored
layer on the substrate are the same as those of the sixth
embodiment, further description thereof is omitted.
Protective Film Precursor Layer Formation Step (FIG. 20A and FIG.
20B)
[0218] A protective film precursor 218a is dropped onto the colored
layers R, G, and B, as shown in FIG. 20A. The composition of the
protective film precursor 218a must fulfill the function of a
protective film without affecting the optical transmissivity and
color characteristics required of the color filter, when it has
been hardened in the subsequent step (to form the protective film).
Damage to other components such as a TFT array can be prevented by
also providing this protective film with the suitable strength and
elasticity required of spacers 218d (see FIG. 21A). It is
preferable that the coefficient of thermal expansion thereof is
determined from consideration of volumetric changes due to any
difference in the coefficients of thermal expansion, to ensure that
the reliability of the liquid crystal panel is not affected by
damage to the orientation film or the colored layer. The
composition of the protective film precursor 218a having such
characteristics is the same as that of the sixth embodiment.
[0219] Next, as shown in FIG. 20B, a template 220 provided with
concavities 220b at predetermined positions in a flat surface
thereof (details of the fabrication of this template will be given
later) is attached to the protective film precursor 218a that has
been dropped on the colored layers R, G, and B, then is pressed to
form a protective film precursor layer 218b. The depth of the
concavities 220b formed in the template 220 corresponds to the
height of the spacers 218d (see FIG. 21A) and is processed in
accordance with the liquid crystal panel being fabricated. For a
VGA type of liquid crystal panel using TFTs as drive elements, for
example, this depth is on the order of 2 to 6 .mu.m. The
concavities 220b are preferably located at positions that cross the
lattice-like opaque layer (black matrix) 214, as shown in FIGS. 22A
to 22C. Such a configuration makes it possible for the spacers 218d
to be provided protruding easily at positions crossing the
lattice-like opaque layer 214. Therefore, the spacers 218d are not
disposed on the colored layers R, G, and B (filter elements),
making it possible to improve the yield of manufactured color
filters. In addition, the effects on orientation variations of the
liquid crystal and the polarization characteristics of the liquid
crystal panel caused by the spacers 218d can be reduced by
providing the spacers 218d protruding above the opaque layer 214,
so that the image quality of the liquid crystal panel can be
maintained in a desirable state.
[0220] Any shape such as circular cylindrical or square cylindrical
can be used as the shape of the concavities 220b, but a circular
cylindrical shape is particularly preferable. Disturbances in the
orientation of the liquid crystal can be suppressed by forming the
spacers 218d of a circular cylindrical shape.
[0221] Furthermore, it is not necessary to dispose the spacers 218d
at all of the lattice points of the opaque layer (black matrix)
214; they may be disposed at only a few desired lattice points. It
should be noted, however, that it is necessary to dispose the
spacers 218d in such a manner that a necessary strength is
achieved, in order to maintain a uniform cell gap. The disposition
of the spacers 218d is preferably within a range of 100 to 200
.mu.m, for example.
[0222] The pattern in which the colored layers R, G, and B (filter
elements) are disposed is not limited to a mosaic array as shown in
FIG. 22A, but it could also be a triangular array as shown in FIG.
22B or a strip array as shown in FIG. 22C. In such a case, the
spacers 218d can be disposed protruding from any desired position
on the opaque layer (black matrix) 214. Note that the disposition
patterns of the spacers 218d are shown in these figures by way of
example and the present invention is not limited thereto.
Protective Film Precursor Layer Hardening Step (FIG. 20C)
[0223] After the protective film precursor layer 218b has been
formed over the predetermined region, the protective film precursor
layer 218b is hardened in accordance with the composition thereof.
This step causes the protective film precursor layer 218b to harden
to form a protective film 218c. If an acrylic resin which is
hardened by ultraviolet rays is used as the protective film
precursor layer 218b, for example, ultraviolet rays are shone onto
the protective film precursor layer 218b under predetermined
conditions to harden it.
Template Separation Step (FIG. 21A)
[0224] After the protective film precursor layer 218b has hardened,
the template 220 is separated from the protective film 218c. The
protective film 218c on which the spacers 218d are formed
integrally above the colored layers R, G, and B can thus be
obtained.
Transparent Electrode Formation Step (FIG. 21B)
[0225] Next, transparent electrodes 222 are formed on the
protective film 218c. This step uses a well-known method such as
sputtering or vapor deposition to form the transparent electrodes
222 over the entire surface of the protective film 218c. A material
provided with both optical transmissivity and electrical
conductivity can be used as the material of the transparent
electrodes 222, such as indium tin oxide (ITO) or a composite oxide
such as indium oxide and zinc oxide.
Patterning Step (FIG. 21C)
[0226] If metal-insulator-metal (MIM) technology, using alternate
layers of metal and an insulator, is employed as the method of
driving the liquid crystal panel, resist (not shown in the figure)
is coated over the transparent electrodes 222 and the transparent
electrodes 222 are patterned to a desired shape by etching.
[0227] Alternatively, if a method such as thin film transistors
(TFTs) is used for driving the liquid crystal panel, this step is
not necessary.
[0228] If the transparent electrodes 222 on the spacers 218d cause
problems, the transparent electrodes 222 are removed from the tops
of the spacers 218d by etching, using a method similar to those
described above. Note that the transparent electrodes 222 need not
be removed from on top of the spacers, but only if no problems are
caused by leaving the transparent electrodes 222 on top of the
spacers 218d.
Template Fabrication Process
[0229] The process of fabricating the template 220 used in the
present embodiment will now be described, with reference to FIGS.
23A to 23C.
Resist Layer Formation Step (FIG. 23A)
[0230] Resist is coated over a substrate 220a made of quartz, to
form a resist layer 226. As long as the substrate 220a is of a
material which can be etched, it is not restricted to quartz, and
glass, silicon single crystal, metal, ceramic, resin, or other
material may be used therefor. The composition of the resist layer
226 could be one that is generally used in the fabrication of
semiconductor devices, for example, a commercially available
positive resist which is a cresol novolac type resin to which a
diazo-naphthoquinone derivative is added as a photosensitive
material. In this case, the positive resist is a material that can
be selectively removed by a developer in exposed regions. The
thickness of the resist layer 225 is sufficient to provide the
necessary thickness to enable it to act as an etching mask in the
subsequent etching step, which is roughly 1 to 3 .mu.m.
Resist Layer Exposure Step (FIG. 23B)
[0231] A mask 212a is placed on the resist layer 226, then the
resist layer 226 is exposed in a desired pattern through the mask
212a. The mask 212a is formed in a pattern such that light passes
therethrough only in regions corresponding to the concavities 220b
shown in FIG. 20B, in other words, the previously described spacers
218d.
Development Step (FIG. 23C)
[0232] If development with a developer is done after the exposure,
the resist is selectively removed only in regions that were exposed
in the exposure step, to reveal the substrate 220a as shown in FIG.
23C, with the other regions remaining covered by the resist layer
226. An alkaline aqueous solution of tetramethyl ammonium
hydroxide, sodium hydroxide, potassium hydroxide, calcium
hydroxide, or trisodium phosphate mixed with sodium silicate could
be used as the developer.
Etching Step (FIG. 24A)
[0233] The substrate 220a is etched to a predetermined depth, using
the patterned resist layer 226 as a mask. Details of the etching
method are as previously described for the first step, and the
concavities 220b could be made square or tapered. The depth of the
etching corresponds to the depth of the spacers to be formed. which
is roughly 2 to 6 .mu.m.
Resist Layer Separation (FIG. 24B)
[0234] When the depth of the concavities 220b has reached a
predetermined depth, the etching is stopped and the resist layer
226 is peeled off.
[0235] In this manner, the depth of the concavities 220b of the
template 220 can be controlled very accurately by the etching
technique. For example, etching errors are .+-.0.05 .mu.m for a
concavity depth of 3 .mu.m. Therefore, the height of the spacers,
in other words, the cell gap, can be kept constant and thus it can
easily be maintained at a value that is suitable for the
retardation of the liquid crystal.
[0236] If, for example, natural light is incident on an STN liquid
crystal panel from above, light passing through a first
polarization film is polarized linearly and light passing through a
second polarization film is polarized circularly by the multiple
refractions due to the liquid crystal molecules. The shift in this
phase depends on the retardation and which is the product of the
difference an between the refractive indices along the long and
short axes of the liquid crystal molecules and the thickness (cell
gap spacing) d of the liquid crystal layer. The magnitude of this
retardation is an important factor in the design of the liquid
crystal panel. With normally-black mode, for example, it is known
that if the magnitude of the retardation falls to 0.48 .mu.m or
less with light of 550 nm, the contrast will suddenly deteriorate
due to leakage of this light. With the present embodiment, not only
can the positions of the spaces be adjusted easily, but also the
height of the spacers (cell gap spacing) d can be made uniform, so
that the magnitude of the retardation can be maintained at a
suitable value. It is therefore possible to easily adjust the
display characteristics of the liquid crystal, such as optical
transmissivity, contrast ratio, and response speed.
[0237] In addition, since the protective film and spacers of the
present embodiment can be formed as an integral assembly, there is
no danger of impurities (particularly impurities such as ions)
becoming mixed into the liquid crystal due to dispersion of the
spacers, as in the conventional art. Therefore, when a voltage is
applied to the liquid crystal sandwiched between a transparent
electrode and a common electrode, to change the arrangement of the
liquid crystal, the lack of impurities mixed into the liquid
crystal makes it possible to ensure good drive characteristics for
the liquid crystal.
Eighth Embodiment
[0238] The process of fabricating a color filter in accordance with
an eighth embodiment is shown in FIGS. 25A and 25B.
[0239] The present embodiment is applicable instead of the step of
the sixth embodiment shown in FIG. 18A. In other words, the steps
shown in FIGS. 16A to 17C are performed in the same manner as in
the sixth embodiment, then the step shown in FIG. 25A is performed.
The step shown in FIG. 25A differs from that shown in FIG. 18A in
that a transparent electrode film 300 is formed on a template 302
beforehand. A color filter with attached transparent electrode film
300 is obtained by separating the template 302 from the transparent
electrode film 300, as shown in FIG. 25B.
[0240] Note that the combination of materials configuring the
template 302 and the transparent electrode film 300 may cause
problems such as increasing the adhesive forces therebetween so
that it is difficult for the transparent electrode film 300 to
separate from the template 302. This increases the defective
product ratio due to faults such as errors or cracking in the
transparent electrode film 300, reducing the mass-productivity
because of the time required for the separation, or reducing the
durability of the template 302.
[0241] To this end, radiation 306 is shone through the template 302
onto the interface between the transparent electrode film 300 and
the template 302, as shown in FIG. 25A. This reduces or even
destroys the adhesive forces between the transparent electrode film
300 and the template 302, so that the transparent electrode film
300 can separate easily from the template 302, as shown in FIG.
25B.
[0242] More specifically, the various bonding forces between atoms
or molecules are weakened or destroyed at the interface between the
transparent electrode film 300 and the template 302, so that
phenomena such as ablation occur, leading to interface separation.
Alternatively, the radiation 306 vaporizes and releases components
within the transparent electrode film 300, which activates a
separation effect and may even help the interface separation.
[0243] To cause this interface separation due to the illumination
of the radiation 306, it is necessary to make the material of the
template 302 transparent to the radiation 306 and also form the
transparent electrode film 300 of a material that absorbs the
energy of the radiation 306.
[0244] In this case, the transmissivity of the template 302 with
respect to the radiation 306 is preferably at least 10%, more
particularly at least 50%. It is preferable that the transmissivity
of the radiation 306 through the template 302 is made high, to
reduce the attenuation of the illuminated radiation 306 as it
passes through the template 306. Quartz glass may be cited as an
example of the template 302. Quartz glass is highly transparent to
light in the short wavelength region and has a superlative
mechanical strength and thermal resistance.
[0245] Deep UV light could be cited as an example of the radiation
306. The source of this radiation could be an excimer laser, for
example, which is used to output a high level of energy in the
short wavelength region. If an excimer laser is used, ablation is
induced only in the vicinity of the interface within an extremely
short time, and the template 302 and the transparent electrode film
300 are subjected to substantially no temperature shock.
[0246] The surface of the transparent electrode film 300 that has
been separated from the template 302 is then preferably washed to
remove any portions that have been damaged by the radiation
306.
[0247] The above processing makes it possible to obtain the color
filter shown in FIG. 25B. With the present embodiment, the
transparent electrode film 300 is formed beforehand on the template
302, so that the protective film 217c and the colored layers R, G,
and B are not damaged by processes such as annealing. In addition,
the flexibility with which materials are selected is increased
because the protective film 217c and the colored layers R, G, and B
are not exposed to high temperatures during annealing.
Ninth Embodiment
[0248] A ninth embodiment of the present invention will now be
described with reference to FIGS. 26A and 26B. In the present
embodiment, a separation layer 304 is formed between the template
302 and the transparent electrode film 300, as shown in FIG. 26A.
In other words, the separation layer 304 is first formed on the
template 302, then the transparent electrode film 300 is formed on
top of the separation layer 304. The rest of the structure is the
same as that of the eighth embodiment.
[0249] When the radiation 306 illuminates the separation layer 304
through the template 302, as shown in FIG. 26B, the template 302
and the transparent electrode film 322 separate readily.
[0250] Various materials can be used as the material of the
separation layer 304, such as various oxide ceramics such as
non-crystalline silicon, silicon oxide, silicate compounds,
titanium oxide, titanium oxide compounds, zirconium oxide, zircon
oxide, lanthanum oxide, or lanthanum oxide compounds; (strong)
dielectric materials or semiconductors; nitride ceramics such as
silicon nitride, aluminum nitride, or titanium nitride; organic
high-molecular materials such as acrylic resins, epoxy resins,
polyamides, or polyimides; or alloys of one or more metals selected
from the group of Al, Li, Ti, Mn, In, Sn, Y, La, Ce, Nd, Pr, Gd,
and Sm; by way of example. Materials are selected as appropriate
therefrom to suit factors such as processing conditions and the
materials of the template 32 and the transparent electrode film
300.
[0251] The method of making the separation layer 304 is not
particularly limited, and can be selected as appropriate to suit
the composition and the film thickness thereof. More specifically,
various vapor-phase methods such as CVD, deposition, sputtering, or
ion plating could be used therefor, or a method such as
electro-plating, nonelectrolytic plating, a Langmuir blow-jet (LB)
method, spin-coating, dipping, spray-coating, roll-coating, or
bar-coating.
[0252] If the separation layer 304 is too thin, damage to the
transparent electrode film 300 will be greater; but if it is too
thick, the amount of energy of the radiation 306 that must be
applied to ensure good separability of the separation layer 304
will have to be increased. To that end, the thickness of the
separation layer 304 will differ according to the separation
objective and composition, but it is preferably on the order of 1
nm to 20 .mu.m, more preferably on the order of 10 nm to 20 .mu.m,
and even more preferably on the order of 40 nm to 1 .mu.m. Note
that the thickness of the separation layer 304 is preferably as
uniform as possible.
[0253] If the radiation 306 is shone onto the thus-configured
separation layer 304 as shown in FIG. 26B, it can be separated from
the template 302. Different separation states are shown in FIGS.
27A to 27C.
[0254] FIG. 27A shows an example in which the bonding forces at the
interface between the template 302 and the separation layer 304 are
reduced, so that separation occurs at that interface. In this case,
it is preferable to wash the assembly, to remove the separation
layer 304 from the transparent electrode film 300.
[0255] FIG. 27B shows an example in which the bonding forces at the
interface between the transparent electrode film 300 and the
separation layer 304 are reduced, so that separation occurs at that
interface. In this case too, it is preferable to wash the surface
of the transparent electrode film 300, because fragments of the
separation layer 304 will adhere to the transparent electrode film
300.
[0256] FIG. 27C shows an example in which the bonding forces
between molecules or atoms are reduced within the separation layer
304, so separation occurs there. In this case too, it is preferable
to wash the assembly, to remove fragments of the separation layer
304 from the transparent electrode film 300.
[0257] Note that the separation state is not limited to the above
described three examples; it is also possible for combinations of
these separations to occur locally.
[0258] A cross-sectional view through a thin-film transistor (TFT)
color liquid crystal panel that is combined with a color filter 210
is shown in FIG. 28. This color liquid crystal panel is provided
with a glass substrate 204a facing the color filter 210, with a
liquid crystal compound 202a injected therebetween. The color
filter 210 is provided with red (R), green (G), and blue (B)
colored layers 206 on a glass substrate 204b to correspond to
primary-color display elements of the liquid crystal panel, and is
an essential filter for displaying colors by the liquid crystal
panel. An opaque layer (black matrix) 209 is formed between the
colored layers 206, to improve the contrast and prevent mixing of
the coloring materials. A protective layer 207 and a common
electrode 208 are formed in sequence on the colored layers 206.
Transparent pixel electrodes 203 and TFTs (not shown in the figure)
are formed on the matrix on the inner side of the glass substrate
204a. Orientation films 201a and 201b are formed on the inner
surfaces of the two glass substrates 204a and 204b, and the liquid
crystal molecules can be orientated in fixed directions by
subjecting those films to rubbing. Spacers 202b for keeping the
cell gap spacing constant are inserted into the region (call gap)
bounded by the orientation films 201a and 201b. Spheres of silica,
polystyrene, or the like are used as these spacers 202b. A color
display can be achieved by shining a backlight onto this liquid
crystal panel and causing the liquid crystal compound 202a to
function as an optical shutter that varies the transmissivity of
the backlight.
* * * * *