1. Field of the Invention
The present invention relates to a process for producing a transparent substrate having thereon transparent conductive pattern elements separated by a light-shielding insulating film, as well as to a process for producing a surface-colored material by utilizing said process.
2. Prior Art
As a conventional process for producing a surface-colored material for use in a color filter of a display device, a solid-state image sensor or the like, there is disclosed a process utilizing a polymer electrodeposition method, in Japanese Patent Application Kokai (Laid-Open) No. 115886/1984. This conventional process comprises forming a transparent conductive pattern on a transparent substrate, immersing the resulting substrate having a transparent conductive pattern thereon in a pigment-containing polymer bath for electrodeposition, and applying a voltage between the transparent conductive pattern used as an electrode and a counter electrode to form a colored layer on the transparent conductive pattern. The process has wide applications because the conditions of electrodeposition can be varied over a broad range, and moreover is simple to carry out.
In color filters where a high resolution is required, each of the blue-, green- and red-colored layer units has a very small area, which in some cases causes partial overlapping of light beams which have passed through the gap between two adjacent colored layer units or its vicinity, resulting in reduction in resolution of the color filter. The surface-colored material described in the above patent document has no means for prevention of said reduction in resolution and, when used in a color filter, is unable to avoid the reduction in resolution.
Hence, it has been carried out to form a light-shielding insulating film between the colored layer units of the surface-colored material in order to shield the unnecessary portion of the applied light. As the method for forming such a light-shielding insulating film, there are mentioned a printing method (e.g. silk screen printing, offset printing) and a photolithography method. The printing method enables only the formation of a transparent conductive pattern whose pattern-to-pattern distance is as narrow as about 100 .mu.m at best, and cannot be applied to the formation of a light-shielding insulating film for use in color filters of high resolution.
The photolithography method is described in, for example, Japanese Patent Application Kokai (Laid-Open) No. 247331/1987. The method described in this patent document comprises forming blue-, green- and red-colored layer units on transparent conductive pattern elements on a transparent substrate according to a polymer electrodeposition method, coating a pigment-containing photocurable resin on the whole surface of the transparent substrate including the colored layer units, applying a light to only the gaps between the transparent conductive pattern elements from the back side of the transparent substrate by using the colored layer units as a light-shielding mask to cure the photocurable resin present in said gaps, removing the photocurable resin portion which has not been irradiated with the light and remains uncured, and thereby forming a light-shielding insulating film consisting of a pigment-containing cured resin, in the gaps between the transparent conductive pattern elements.
The method described in the above Japanese Patent Application Kokai (Laid-Open) No. 247331/1987, however, has the following drawbacks. In the method, the colored layer formed on a transparent conductive pattern on a transparent substrate and having a function of a color filter in the final product has another function of a light-shielding film, but the light-shielding property is ordinarily insufficient; therefore, if the back side of the transparent substrate is irradiated with an ultraviolet light at a high irradiation dose of 75 J/cm.sup.2, the portion of a photocurable resin present on the colored layer causes an undesirable photocuring reaction and, if the back side of the transparent substrate is irradiated at a low irradiation dose of 50 J/cm.sup.2 in order to prevent the photocuring reaction, the photocurable resin portion on the colored layer is not cured but the intended curing of the photocurable resin portion present in the gaps between the transparent conductive pattern elements becomes insufficient resulting in no formation of an intended dense, light-shielding, insulating film between the pattern elements; thus, strict control of light exposure conditions is necessary in order to form an intended dense, light-shielding insulating film between the pattern elements.