Self-aligned method for forming a color display screen

Abstract

For the manufacture of a color screen for a cathode ray tube a process is described which uses a single photolithographic mask for defining multiple patterns, so that said single mask may be used for determining the different areas where several different phosphor layers will be located. Masks used for conventional photolithographic processes normally comprise a pattern of regions that are either fully transparent or fully opaque to the radiation used for exposing the resist. The mask used as part of the present invention includes regions that are neither fully transparent nor fully opaque, having, instead, a grey scale of optical densities. Through careful control of both exposure and development time, selected parts of a layer of a positive photoresist, that were exposed through successively denser regions of the mask, can be successively removed. As each of these parts of the resist is removed, parts of an underlying layer of adhesive are uncovered and then serve as selective sites for the application of phosphor particles. The process may be used with or without the inclusion of a black matrix as part of the structure.