Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-08-27
2003-08-05
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S417000, C428S447000, C525S100000, C525S102000, C525S119000, C525S117000
Reexamination Certificate
active
06602604
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to coating compositions useful for the formation of protective films, capable of providing smooth and transparent surfaces. More particularly, the present invention relates to coating compositions for forming protective films on color filters laid over glass or transparent materials.
2. Background Art
In recent years, liquid crystal display elements have been extensively used in audiovisual equipment, and electronic equipment such as personal computers. In particular, the demand for color displays is now rapidly increasing since they are excellent in visibility and amount of information. To produce color displays, color filters in the shape of mosaic, stripes, or the like are usually formed on transparent substrates such as glass by a dyeing, printing, pigment dispersing or electrode position process, or the like.
In general, these color filters are produced so that their thickness will be approximately 1 micron, where it is inevitable that the color filters have surface roughness in the submicron range. In color STN displays, this roughness affects the quality of display (unevenness in color, etc.). In order to eliminate unevenness in display, it is necessary to control the surface roughness of the color filters to 0.1 microns or less. To obtain such smooth surfaces, thermosetting acrylic resins have conventionally been applied to the surfaces of the color filters.
Not only in liquid crystal display elements but also in charge coupled devices (CCD), their color filters require surface protection. Protective films are thus needed to protect the color filters from severe conditions under which post-treatments are conducted, for example, from solvents, acidic or alkaline solutions, etc. that are used for dipping treatment, and from high-temperature heat that is generated while electrode layers are formed by sputtering. Such protective films are required to be smooth, strong, and excellent in transparency. They are also required to be excellent in resistance to heat and chemicals so that they will undergo no change in color and quality for a long period of time. To meet these requirements, thermosetting resins including epoxy copolymers have so far been used.
Many conventionally known coating compositions for forming protective films are of two-bottle type. In the case of two-bottle-type coating compositions, it is necessary to mix two liquids before use, and, once they are mixed, it is desirable to use the mixture immediately. In addition, the coating compositions can, depending on their compositions, produce sublimates while they are curing. These sublimates crystallize to give foreign particles, which can cause troubles during the production of liquid crystal panels. There have therefore been demanded coating compositions that never give crystallized materials.
Japanese Patent Laid-Open Publication No. 27348/1996, for instance, describes a coating composition useful for the formation of protective films suitable for the aforementioned purpose. This composition is a coating resin composition comprising (A) a copolymer resin containing (1) 10% by weight or more and less than 30% by weight of a methacrylic or acrylic acid ester in which an alicyclic group having 7 to 20 carbon atoms, containing tertiary carbon in its ring is attached to ester group, and (2) more than 60% by weight and 90% by weight or less of glycidyl methacrylate or acrylate, and (B) a copolymer resin containing, as essential components, (a) N-substituted maleimide and (b) acrylic or methacrylic acid. In this publication, it is suggested that a coupling agent having epoxy group be introduced to the coating composition in order to improve adhesion, a property essential for coating compositions. However, according to our investigations, there was still room for improvement in reliability in terms of the peeling of films of the coating composition.
SUMMARY OF THE INVENTION
We now found that coating compositions having high storage stability, capable of forming films excellent not only in transparency, smoothness, and resistance to sputtering, but also in adhesion, which is a property particularly important for coating compositions to be used to form protective films, can be obtained when specific polymers and specific additives are used in combination. The present invention was accomplished on the basis of this finding.
An object of the present invention is therefore to provide coating compositions that are essentially stable and that can form excellent protective films.
More specifically, an object of the present invention is to provide coating compositions having storage stability equal to or better than that of conventional coating compositions, capable of forming films having not only transparency, smoothness and sputtering resistance equal to or more excellent than those of films of conventional coating compositions, but also excellent adhesion properties.
A coating composition according to the present invention comprises:
(A) at least one polymer containing carboxyl group, having a weight-average molecular weight, as calculated in terms of styrene, of 5,000 to 200,000, an acid value KOH of 10 to 300 mg/g, and a glass transition temperature of 50 to 250° C.,
(B) as a crosslinking agent, a multifunctional epoxide-containing compound having at least one benzene ring or heterocycle, and two or more epoxy groups,
(C) an organic solvent, and
(D) at least one amino-containing silane coupling agent represented by the following general formula (I):
H
2
N—R
1
—Si—(OR
2
)
3
(I)
wherein, R
1
is an unsubstituted alkylene group, and R
2
's are independently an unsubstituted alkyl group.
DETAILED DESCRIPTION OF THE INVENTION
A coating composition according to the present invention basically contains (A) a polymer, (B) a crosslinking agent, (C) an organic solvent, and (D) an amino-containing silane coupling agent.
Polymer
In the present invention, the polymer (A) is defined as a polymer containing carboxyl group, having a weight-average molecular weight, as calculated in terms of styrene, of 5,000 to 200,000, an acid value KOH of 10 to 300 mg/g, and a glass transition temperature of 50 to 250° C. In a preferred embodiment of the present invention, the polymer has a weight-average molecular weight of approximately 10,000 to 100,000, and an acid value KOH of about 30 to 100 mg/g.
Preferable examples of such polymers are copolymers of compounds selected from acrylic acid, methacrylic acid, and esters thereof, and aromatic vinyl compounds. Examples of compounds selected from acrylic acid, methacrylic acid, and esters thereof include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, ethylhexyl methacrylate, and phenyl acrylate. Examples of aromatic vinyl compounds include styrene, &agr;-methylstyrene and p-methyl-styrene.
These copolymers may be of any type; they may be any of random copolymers produced by addition polymerization, block copolymers, and the like. Further, there is no particular limitation on the copolymerization process, and any one of the solution polymerization process, the emulsion polymerization process and the like can be adopted to produce the copolymers. In the present invention, the amount of the polymer to be used may be properly determined within such a range that the resulting coating composition can form excellent protective films. It is however preferable to use the polymer in an amount of approximately 5 to 30% by weight, more preferably about 10 to 25% by weight of the coating composition.
Crosslinking Agent
In the present invention, the crosslinking agent is a multifunctional epoxide-containing compound having, in one molecule, at least one benzene ring or heterocycle, and two or more epoxy groups. In one embodiment of the present invention, the epoxide-containing compound is preferably one having phenyl group and cyclohexyl group, more preferably one having two or more phenyl groups.
In a preferred embodiment of the present invention, th
Fukuzawa Junichi
Harada Takamasa
Kurisaki Minoru
Sakamoto Katsuyuki
Clariant Finance (BVI) Limited
Dawson Robert
Kass Alan
Keehan Christopher M.
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