Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
2001-07-11
2003-02-25
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
06524757
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color filter which is used in color liquid crystal displays, color scanners and solid image pick-up elements, and, more particularly, to a color filter having excellent durability, suitable for uses which require durability after passing through the step of forming a pattern by means of exposure and development.
2. Description of Related Art
As one of the photocurable colored compositions using coloring materials such as pigments and dyes, for example, there has hitherto been known a photocurable colored composition obtained by adding a photopolymerizable monomer and a photopolymerization initiator to a colored composition in which a coloring material is dispersed by using a binder and/or a dispersant. There has also been known a method of forming a colored image by means of a method of coating the photocurable colored composition to a substrate, drying the photocurable colored composition, exposing the coated substrate to light through a mask, developing to form a colored pattern, and fixing the colored pattern by baking. One of industrial applications of these photocurable colored compositions include, for example, a color filter used in color liquid crystal displays, color scanners and solid image pick-up elements. The color filter is formed by arranging coloring materials on each pixel to selectively transmit the three primary colors (red, green, and blue) of light or to selectively reflect the three primary colors (cyan, magenta, and yellow) of color, on a transparent substrate provided with a black matrix.
Characteristics required of materials for color filters often originate in the process of manufacturing color liquid crystal displays, and examples thereof include heat resistance required in the deposition or sputtering processes of a transparent electrode and baking process of a color filter, and solvent resistance required in the cleaning and alignment film coating processes. Furthermore, light resistance is also required because light transmitted through the color filter becomes image information during the display of the image.
To meet these requirements, pigments have mainly been used as the coloring material. As the manufacturing method, for example, a “pigment dispersion method” has popularly been used (LCD Panel Elements and Technology, pp. 23-25, Press Journal Inc., issued on Mar. 20, 1999). Acrylic binder resins having comparatively superior heat resistance, light resistance, transparency, and chemical resistance have mainly been used as the binder resin in the method.
As the developer used in the development process after the exposure process in the processes of manufacturing a color filter by means of the “pigment dispersion method”, an aqueous alkaline solution is more preferable than an organic solvent in view of environmental problems. To impart the development aptitude in an aqueous alkaline solution to a photocurable colored composition, the solubility to alkaline solution is also required of the binder resin used to disperse the pigment, and an acrylic binder resin having a carboxyl group is generally used as an alkaline developing type photocurable colored composition.
However, the acrylic resin having a carboxyl group had a drawback in that it is liable to be decomposed when the temperature exceeds 200° C.
For the purpose of overcoming the drawback, a resist material comprising an alkali-soluble resin, a photo acid generator, and a melamine resin (Japanese Patent Application, First Publication No. Hei 8-292564) and a negative type-photosensitive composition for a color filter, comprising an acrylic resin having a carboxyl group, a photo acid generator, and a crosslinking agent capable of curing by an action of the acid (Japanese Patent Application, First Publication No. Hei 9-203806) are disclosed.
In these substances, the melamine resin is crosslinked by an action of an acid generated from the photo acid generator under light irradiation and is to be insoluble in an alkaline developer, thereby making it possible to form a pattern.
When using the photo acid generator, however, the acid attributable to the photo acid generator remains in the color filter, thereby causing deterioration of the color filter, or causing diffusion of the acid into a liquid crystal, resulting in increasing of the conductivity of the liquid crystal. Therefore, it is not preferred.
It has been required to develop a color filter, which has excellent heat resistance and does not cause color change due to heat during post-baking, with the increase of the temperature during the deposition of a transparent electrode, sputtering or baking after the development.
Under these circumstances, it is required to develop a color filter, which has both physical properties of the coating (e.g., good heat resistance and solvent resistance) and alkali developing properties, and is free from residual impurities that causes degradation of the liquid crystal.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a color filter which is capable of forming a pattern using an alkaline developer and has excellent heat resistance, solvent resistance, and chemical resistance, especially heat resistance, and is also suitable for practical use.
To attain the object described above, the present invention provides a color filter comprising a transparent substrate and a pixel formed on the transparent substrate, wherein the pixel is made of a coating layer of a curable colored composition containing (a) a coloring material, (b) a compound having a photopolymerizable functional group, and (c) an amino resin having a carboxyl group and/or a phenolic hydroxyl group and the coating layer is photocured, followed by heat curing.
To attain the object described above, the present invention also provides a method for producing a color filter, which comprises forming a coating layer on a transparent substrate using a curable colored composition containing (a) a coloring material, (b) a compound having a photopolymerizable functional group, and (c) an amino resin having a carboxyl group and/or a phenolic hydroxyl group, exposing the coating layer to light via a mask having a pixel pattern for a color filter, thereby curing the coating, developing the coating to form a pixel, and heating the pixel, thereby heat-curing the pixel.
Since the color filter of the present invention contains, as an alkali-soluble binder resin, an amino resin having a carboxyl group or a phenolic hydroxyl group, the resulting coating film has an excellent capability of forming a pattern using an alkaline developer. According to the method for producing a color filter of the present invention, since a photopolymerizable colored resin composition containing a compound having a photopolymerizable functional group is used, the resulting coating is photopolymerized by means of photolithography, thus making it possible to form a pixel having excellent heat resistance, solvent resistance, and chemical resistance and to provide a color filter suitable for practical use.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described in more detail.
The transparent substrate used in the present invention is a transparent substrate which is used in the color filter and has enough heat resistance to endure heat curing. Such a transparent substrate is, for example, a glass substrate.
As the coloring material (a) used in the present invention, for example, dyes and pigments used usually in the color filter can be used without any problem, but pigments are preferably used in view of heat resistance and light resistance.
The average particle diameter of the pigment is preferably within a range from 0.005 to 3 &mgr;m, and more preferably from 0.01 to 1 &mgr;m. When the average particle diameter is smaller than the above range, thixotropy is liable to appear, and therefore, good applicability cannot be obtained. On the other hand, when the average particle diameter is larger than the above range, the resulting coating has poor
Hirota Yasunobu
Koike Junichiro
Tokuda Hiroyuki
Yonehara Hisatomo
Dainippon Ink and Chemicals Inc.
McPherson John A.
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