Radiation imagery chemistry: process – composition – or product th – Liquid crystal process – composition – or product
Patent
1992-02-06
1993-08-17
Bowers, Jr., Charles L.
Radiation imagery chemistry: process, composition, or product th
Liquid crystal process, composition, or product
430 7, 430321, 430325, 430961, 359 68, G02B 104, G03L 172
Patent
active
052367932
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a material for forming an overcoat on a color filter and a material for forming a color filter to be used for liquid crystal display devices, a process for forming the overcoat, and a process for forming the color filter.
BACKGROUND ART
Liquid crystal display devices have the features of, e.g., being electrically operated at a low voltage and operated with a low electric power, having color display and providing a display area in the range of from several millimeters square to tens meters square. In recent years, research and development have been in rapid progress to put to practical use liquid crystal display devices with color display and large-size display. These liquid crystal display devices are required to have a high picture element density, the formation of fine patterns of transparent electrode having a pitch of about 100 .mu.m, a high reliability, etc.
An electrode plate having a transparent electrode formed on a color filter in a color liquid crystal display device is excellent in the operability of liquid crystal and the quality of display. In such display devices, an overcoat of organic resin is usually formed between a color filter and a transparent electrode in patterning the transparent electrode by etching.
The overcoat is formed to make the color filter flat and to protect the filter, and thus must have a high adhesion to a transparent electrode, compatibility with the process of patterning a transparent electrode, resistance to heat, resistance to acids, resistance to alkalis, etc.
Conventional overcoats are usually formed from a resin of the same type as used for a color filter in view of the adhesion to the color filter. However, substantially all species of resins used for color filters have the drawbacks of, for example, exhibiting low resistance to heat in the formation of transparent electrode, thereby causing wrinkles and blisters.
Known among methods of forming a patterned overcoat is a method in which an overcoat is produced from a photosensitive resin and then developed with an organic solvent. This method employs an organic solvent as a developer, which is difficult to handle and makes the working environment unfavorable. Also known is a method in which an overcoat of photosensitive resin is exposed to light and developed with an aqueous solution of alkali. The overcoats formed from photosensitive resins conventionally used in such method are not fully satisfactory in properties such as resistance to water and heat.
DISCLOSURE OF THE INVENTION
In view of the foregoing problems of the prior art, the inventors conducted research and found the following. Using a material for overcoat comprising a water-soluble photopolymerizable substance, a cationically polymerizable, water-insoluble photopolymerizable substance, a photopolymerization initiator and a precursor of photo-setting catalyst, a patterned overcoat can be easily formed by applying the material to the surface of a filter, curing the overcoat by exposure to light, and developing the unexposed portion of overcoat with an aqueous solution of alkali. The overcoat thus formed is excellent in the adhesion to the transparent electrode and the color filter and is improved in the resistance to water, acids, alkalis and heat without impairing the spectral characteristics nor the color of color filter. A further discovery was that when the development is conducted by a method using an aqueous solution of organic alkali or by a method comprising dipping in an aqueous solution of organic alkali after development with an aqueous solution of inorganic alkali, the overcoat thus obtained is further improved in the resistance to heat and chemicals.
Another finding was that when a coloring agent is incorporated into the foregoing material for overcoat, a material for a color filter can be obtained which is capable of easily forming a color pattern having high resistance to water, acids, alkalis and heat.
The present invention provides a material for overcoat on a color filter
REFERENCES:
patent: 4357415 (1982-11-01), Hartman
patent: 4934791 (1990-06-01), Shimizu et al.
patent: 5045418 (1991-09-01), Fukuyoshi
Fukuyoshi Kenzo
Matsushima Shuji
Nishimoto Toyoshi
Nishiwaki Kenichi
Bowers Jr. Charles L.
McPherson John A.
Okuno Chemical Industries Co. Ltd.
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