In a color filter used for a liquid crystal display device (LCD) or an image sensor (CCD, CMOS), a pattern of a transparent resin layer is sometimes formed according to respective purposes.
In the case of a color filter for liquid crystal display devices, a pattern of a transparent resin layer is formed, for example, to provide a photospacer (see, for example, FIG. 4 and Patent Documents 1 and 2) used for holding a fixed cell gap defined between a color filter layer and a TFT layer or produce a color filter of an MVA (multi-domain vertical alignment) liquid crystal display device (see, for example, Patent Documents 3 and 4). The photospacer is formed on a display screen, that is, on RGB in some cases.
On the other hand, in the case of a color filter for image sensors, a pattern is formed using a photosensitive transparent resin composition and out of a plurality of colors of a color filter, one color is sometimes made white (transparent) so as to increase the sensitivity (see, for example, FIG. 3 and Patent Document 5). This is because the recent progress in increasing the number of pixels to enhance the resolution and forming a micropixel forces a small opening that leads to sensitivity reduction, and for the purpose of compensating the sensitivity reduction, one color of a color filter is made white (transparent) to thereby raise the sensitivity.
The characteristics, shape and the like required in the pattern formation of the transparent resin layer may vary, but there is a common problem. That is, the transparent resin film is liable to transmit light such as active energy ray (e.g., i line) and this disadvantageously allows the pattern line width of the transparent resin layer to be readily thickened and makes bad the resolution and pattern profile.
In particular, the color filter for image sensors is often faced with a problem in the pattern resolution of the transparent resin layer due to halation at the exposure, because the pattern formation is performed on a wafer.
Examples of the measure heretofore taken to solve the problem above, specifically, to obtain excellent resolution and adequate line width, include a method of adjusting the amount of an active radical generated, that is, adjusting the kind or amount of the photopolymerization initiator. For example, in the case of line width thickening and/or bad resolution, a method of using an initiator with low sensitivity or decreasing the amount of the initiator used, thereby reducing the amount of an active radical and obtaining an adequate line width, is known. However, in recent years, the latitude in the product specification is increasingly becoming strict and under these conditions, it is required to reduce the variation in the line width, film thickness and the like due to exposure illuminance dependency. The problem of exposure illuminance dependency can be hardly solved only by adjusting the kind or amount of the initiator particularly when the coating film has an i-line transmittance. In order to improve the exposure illuminance dependency, a method of increasing the amount of the initiator is usually used, but this conversely brings about excessive thickening of the line width, worsening of the resolution, or generation of a peripheral scum due to halation at the exposure.
As a method for solving these problems, a technique of using an antioxidant and thereby achieving improvement of the resolution of a pattern and reduction in the illuminance dependency of an exposure machine has been disclosed (see, for example, Patent Document 6). Also, a technique of adding a pigment or a dye to decrease the transmittance at the exposure wavelength and thereby achieving improvement of the resolution of a pattern has been disclosed (see, for example, Patent Documents 7 and 8).    Patent Document 1: JP-A-2000-171786    Patent Document 2: JP-A-2001-92128    Patent Document 3: JP-A-2000-122065    Patent Document 4: JP-A-2004-361448    Patent Document 5: JP-A-2007-53153    Patent Document 6: JP-A-2006-11397    Patent Document 7: JP-A-2000-171786    Patent Document 8: JP-A-2006-276488