An improved photoimagable cationically polymerizable epoxy based coating material is provided, that is suitable for use on a variety of substrates. The material includes an epoxy resin system consisting essentially of between about 10% and about 80% by weight of a polyol resin which preferably is a condensation product of epichlorohydrin and bisphenol A having a molecular weight of between about 40,000 and 130,000; and between about 35% and 72% by weight of an epoxidized glycidyl ether of a brominated bisphenol A having a softening point of between about 60.degree. C. and about 110.degree. C. and a molecular weight of between about 600 and 2,500. A third resin, either an epoxy cresol novolak or a polyepoxy resin, is also added to the resin system. To this resin system is added about 0.1 to about 15 parts by weight per 100 parts of resin of a cationic photoinitiator capable of initiating polymerization of said epoxidized resin system upon exposure to actinic radiation; the system being further characterized by having an absorbance of light in the 330 to 700 nm region of less than 0.1 for a 2.0 mil thick film. Optionally a photosensitizer such as perylene and its derivatives or anthracene and its derivatives may be added.