Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
1999-06-25
2001-10-23
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Screen other than for cathode-ray tube
Reexamination Certificate
active
06306550
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
This invention relates to dyes for color filters suitable for use in liquid crystal television sets, color image pickup tubes and color copying machines, photosensitive resist resin compositions containing the dyes, and color filters fabricated by curing the resin compositions.
2) Related Art of the Invention
Known fabrication processes of color filters include printing processes utilizing the principle of printing, dyeing processes and pigment printing processes, both making use of photolithography, and electrodeposition processes involving electrochemical deposition of a dye (“Nikkei New Material”, 48-56 (Feb. 25, 1991)).
Fabrication of a filter by a dyeing process comprises, as shown in
FIG. 1
by way of example, the following steps: (1) coating a glass substrate with a coating formulation which is formed of a water-soluble dyeable high-molecular material, such as gelatin or casein, and to which has been imparted photosensitivity by the addition of a bichromate, (2) exposing the thus-formed coating to ultraviolet rays through a photomask, (3) developing the thus-exposed coating to form a pattern, (4) coloring the pattern with an acid dye, (5) subjecting the thus-colored pattern to color-mixing protection, and (6) repeating steps (1) to (5) until the other two colors are applied to the glass substrate. The color filter obtained by the dyeing process has excellent pattern resolution and dimensional accuracy, superb light transmission and high lightness. Such a dyeing process is, however, accompanied by the following drawbacks:
(1) If the glass substrate is dyed with the second color without applying color protection subsequent to its coloration with the first color, the dye for the second color migrates into the filter layer of the first color so that the spectral characteristics are deteriorated. To avoid this problem, it is necessary to apply a color protection film with an acryl, urethane or epoxy resin or to subject the surface of the dyed medium to chemical treatment with tannic acid or the like.
(2) The heat resistance is insufficient due to the use of gelatin or casein as the base of the photosensitive resin.
On the other hand, fabrication of a filter by a pigment printing process makes use of a pigment which is employed for heat-resistant paints or for the coloration of plastics, and as depicted in
FIG. 2
by way of example, comprises the following steps: (1) coating a glass substrate with a photosensitive resin containing a pigment uniformly dispersed therein, (2) exposing the thus-coated glass substrate to ultraviolet rays, (3) developing the thus-exposed coating to form a colored pattern, and (4) repeating the steps (1) to (3) until the other two colors are applied to the glass substrate. The color filter obtained by the pigment printing process has pattern accuracy as high as that obtained by the dyeing process and is also excellent in heat resistance and light resistance, but is accompanied by the following drawbacks:
(1) Its light transmission is inferior and its contrast is low, because light is scattered by the pigment particles.
(2) Prior to coating the photosensitive resin in which the pigment is uniformly dispersed, the resin should be passed through a filter to eliminate dust and large particles. Processing troubles therefore occur including clogging of the filter by coagulated pigment particles.
If the process shown in
FIG. 2
is followed to fabricate a filter by using “M/P Pink REL” (trade name; product of Mitsui Toatsu Dyes, Ltd.) or “PS Green B” (trade name; product of Mitsui Toatsu Dyes, Ltd.), a resin-soluble conventional dye, instead of a pigment, the conventional dye is not immobilized in a matrix because its molecular weight is lower than 500. As a consequence, the dye may move to an adjacent matrix and cause color mixing. Further, the solubility of the conventional dye is insufficient so that the color filter must have a great film thickness in order to obtain a desired color density.
It is conceivable to immobilize a dye in a matrix resin using, as the dye, a reactive dye containing a monochlorotriazinyl group or a sulfatoethylsulfone group. Such reactive groups are however of the heat reactive type, thereby making it extremely difficult to fabricate micro-matrices like color filters. In addition, a salt remains in the resin after the reaction so that the electrical insulating property is impaired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel dye for a color filter, which is free of problems such as the above-mentioned filter clogging, requires no treatment for the prevention of mixing of individual colors and can furnish a color filter which has good transmission characteristics and is excellent in durability such as heat resistance, light resistance and moistureproofness.
Another object of the present invention is to provide a photosensitive resist resin composition containing the above-described novel dye for a color filter.
A further object of the present invention is to provide a color filter having good transmission characteristics and excellent durability such as heat resistance, light resistance and moistureproofness.
To attain the above objects, the present inventors have proceeded with an extensive investigation. As a result, it has been found that a dye meeting at least one of the below-described two requirements can be stably immobilized in a filter matrix and can hence provide a color filter free of dye color mixing and excellent in transmission characteristics and durability. These requirements are:
(1) Possession of a photopolymerizable substituent; and
(2) Molecular weight of at least 500 but not greater than 4000. Use of a dye capable of satisfying at least either one of these requirements makes it possible to stably immobilize the dye in a filter matrix.
The present invention therefore provides dyes represented by the below-described formula (1),
D—(A—Y
n
1
)
n
2
(1)
wherein D represents a chromophoric nucleus, A denotes a connecting group, Y means the photopolymerizable group, n
1
is 1-10000, and n
2
stands for an integer of 1-10.
The present invention also provides dyes having a molecular weight of at least 500 but not greater than 4000 and represented by the below-described formula (8) or (9),
D—(B—Z)
m
(8)
D—E—D (9)
wherein D in each formula represents a chromophoric nucleus, and B and E each denotes a connecting group, Z is —COOR
9
, CONR
10
R
11
, —OCOR
12
, —OCOOR
13
, —OCONHR
14
, —NHR
15
or —NR
16
R
17
, R
9
and R
12
to R
17
independently representing a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted aralkyl group and R
10
and R
11
independently representing a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group or a hydrogen atom, and m stands for an integer of 1-10.
The present invention also provides photosensitive resist resin compositions comprising the aforesaid dyes, and LCD color filters fabricated by curing the photosensitive resist resin compositions.
The dyes according to the present invention are suitable as dyes for color filters for the following reasons:
(1) The dyes according to this invention are soluble in a resin. Especially, the dyes containing one or more ester, amido, acyl, carbamoyl, amino and/or like groups in their molecules have excellent compatibility with a resin so that they do not develop clogging or coating irregularities when they are coated upon fabrication of color filters having red, green and blue matrices with a photosensitive resist resin.
(2) The dyes according to this invention contain one or more photopolymerizable substituents. Upon photo-setting a resist resin composition, each dye and a photosensitive resist resin are copolymerized or polymerization takes place between molecules of each dye so that t
Itoh Hisato
Karasawa Akio
Sugimoto Kenichi
McPherson John A.
Millen White Zelano & Branigan P.C.
Mitsui Chemicals Inc.
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