Abstract: The present invention relates to a modified epoxy resin, a method for the preparation thereof and an epoxy resin composition using the modified epoxy resin. In particular, it relates to a modified epoxy resin of the general formula (I) which is prepared by incorporating a monomaleimide having a carboxy group useful as a heat resistance-improving agent of a resin composition containing an epoxy resin and maleimides into an epoxy resin, and an epoxy resin composition for sealing a semiconductor element having the improved heat resistance and moldability by the modified epoxy resin. ##STR1## wherein, R represents a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms (C.sub.1 to C.sub.10), andn is 0 to 100, and m is 1 to 100.

Abstract: An epoxy resin composition for sealing semiconductor elements comprising o-cresol-novolak type epoxy resins, curing agents, curing accelerators, inorganic fillers, plasticizers and imide-epoxy resins having the formula (I) is disclosed. Use of the imide-epoxy resin in an amount of 0.1 to 20.0% by weight improves the heat and moisture resistant properties of the epoxy resin composition. ##STR1## wherein, R.sub.1 and R.sub.2 denote independently H or (CH.sub.2)nCH.sub.3 radical,n denotes 0 or an integer of 1 above.

Abstract: An epoxy resin composition for sealing semiconductor elements comprising o-cresol-novolak type epoxy resins, curing agents, curing accelerators, plasticizer and a high performance epoxy resin selected from a group consisting of epoxy resins represented by the formulas (I-a), (I-b) and (I-c) is disclosed.Use of the high performance epoxy resin in an amount of from 0.1 to 20.0% by weight improves the heat and moisture resistance of the epoxy resin composition. ##STR1## wherein, R.sub.1 and R.sub.2 represent independently H or (CH.sub.2) nCH.sub.3 radical, andn represents 0 or an integer of 1 above.

Abstract: A modified epoxy resin of the general formula (I) is prepared by dissolving an epoxy resin in a solvent, adding the mixture to allyl magnesium halide at -70.degree. C. under a nitrogen atmosphere, and removing the solvent and salts from the resultant product. The modified epoxy resin is useful for epoxy maleimide resin compositions as a heat resistance enhancer. An epoxy resin composition for sealing semiconductor elements comprising the modified epoxy resin as a heat resistance enhancer is an amount of from 0.1 to 30% by weight, based on the total weight of the composition, is also provided. ##STR1## wherein, R represents H or C.sub.1 to C.sub.10 -alkyl group and m represents an integer of 0 to 100 and n represents an integer of 1 to 100.

Abstract: The present invention relates to novel epoxy resin compositions for sealing semiconductor elements, which comprise 0.1 to 20.0% by weight of imide-epoxy resins represented by the general formula (I) together with epoxy resins, curing agents, curing promoters and plasticizers, and which has improved heat resistant and moisture resistant properties: ##STR1## wherein, R.sub.1 and R.sub.2 represent H or --CH.sub.2).sub.n CH.sub.3 group, andn represents an integer of 0 or 1.