Abstract: A coating composition, which is suitable for the production of photopolymerizable coatings on circuit boards for the production of solder resists, comprises:(a) an ethylenically unsaturated polymerizable reaction product of a polyepoxide and an ethylenically unsaturated carboxylic acid, which product is solid or semisolid in nature;(b) an inert inorganic filler, the filler and reaction product (a) having present in a weight ratio of from 20 to 65 parts of filler to from 80 to 35 parts of reaction product;(c) a photopolymerization initiator for the polymerizable reaction product; and(d) a volatile organic solvent for the polymerizable reaction product.The compositions are applied to substrates, such as circuit boards, and allowed to dry by evaporation of organic solvent to produce a photopolymerizable coating on the substrate which coating may be cured by exposure to actinic radiation, for example through a patterned mask.