Patent ID: 7112636

Claim:
An epoxy resin composition comprising an epoxy resin, an acid anhydride hardening agent and a hardening accelerator as indispensable ingredients, wherein said hardening accelerator is a phosphonium compound represented by the following formula (I): wherein X represents a halogen atom, SbF 6 , AsF 6 , PF 6 , BF 4 or BPh 4 , and R 1 to R 4 are the same or different, and are an optionally substituted alkyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, an optionally substituted diarylmethyl group or a group represented by the following formula (II): wherein R 5 to R 7 are the same or different, and are an optionally substituted alkyl group, an optionally substituted aryl group, an optionally substituted aralkyl group or an optionally substituted diarylmethyl group, R 8 to R 11 are the same or different, and are a hydrogen atom, an optionally substituted alkyl group or an optionally substituted aryl group, A is an optionally substituted aromatic hydrocarbon ring, n is an integer of 1 to 5, m is 0 or 1, and X is as defined in the formula (I); provided that at least one of R 1 to R 4 is a group represented by the formula (II), and when m is 1, any one of R 1 to R 4 and any one of R 5 to R 7 are combined together to form a lower alkylene group which forms a heterocyclic ring containing two phosphorus atoms.