The modified advanced epoxide resins described, having an average molecular weight of up to 50,000, can be photopolymerized without the need to include photosensitizers. They may be prepared by reaction of a diepoxide ##STR1## with a keto group-containing dihydric phenol ##STR2## to form the advanced epoxide resin ##STR3## followed by condensation with an aldehyde RCHO to yield ##STR4## In the above formulae, R is an organic group which preferably has ethylenic unsaturation or heterocyclic aromaticity in conjugation with the indicated ethylenic double bond; R.sup.1 is the divalent residue linking two epoxide groups; R.sup.2 is preferably a hydrogen atom but may be an organic group, halogen, or cyano; R.sup.3 is a trivalent aromatic or heterocyclic group, especially a group ##STR5## If desired, other dihydric phenols can be employed with that containing a keto group, and condensation with the aldehyde may be carried out so that only some groups --COCH.sub.2 R.sup.2 undergo reaction.