Patent ID: 8278389

Claim:
An epoxy resin composition comprising [A] to [D]: [A] 10 to 50 parts by weight, in 100 parts by weight of total epoxy resins, of an amine epoxy resin; [B] 40 to 90 parts by weight, in 100 parts by weight of total epoxy resins, of a bisphenol epoxy resin; [C] 1 to 10 parts by weight of dicyandiamide or a derivative thereof; and [D] 1 to 10 parts by weight of at least one block copolymer selected from the group consisting of S-B-M, B-M and M-B-M, each block of S, B and M being linked by covalent bonding or being bound to one block through formation of one covalent bond and linked to another block via an intermediate molecule bound through formation of another covalent bond, the block M being a homopolymer of methyl methacrylate or a copolymer containing methyl methacrylate in an amount of at least 50% by weight, the block B being incompatible with epoxy resin and the block M and having a glass transition temperature Tg of 20° C. or below, and the block S being incompatible with epoxy resin, the block B and the block M and having a glass transition temperature Tg higher than the glass transition temperature Tg of the block B, wherein the amine epoxy resin [A] has a reaction initiation temperature within a range of 130 to 150° C., measured under conditions such that one stoichiometric equivalent of dicyandiamide and three parts by weight of 3-(3,4-dichlorophenyl)-1,1-dimethylurea are blended with 100 parts by weight of the amine epoxy resin and the temperature is raised at a temperature-rising speed of 10° C./minute.