Patent ID: 8309631

Claim:
An epoxy resin composition comprising the following [A], [B], [C], and [D]: [A] a diglycidyl ether-type epoxy resin having a molecular weight of 1,500 or more; [B] an epoxy resin in which the solubility parameter value of a structural unit thereof is greater by 1.5 to 6.5 (cal/cm 3 ) 1/2 than the solubility parameter value of a structural unit of [A]; [C] a diglycidyl ether-type epoxy resin having a molecular weight of 500 to 1,200; and [D] an epoxy resin curing agent, in a content ratio that satisfies the following formulas (1) to (4): 0.2 ≦A /( A+B+C+E )≦0.6; (1), 0.2 ≦B /( A+B+C+E )≦0.6; (2), 0.15 ≦C /( A+B+C+E )≦0.4; and (3), 0 ≦E /( A+B+C+E )≦0.2, (4) wherein A, B, and C represent weights of [A], [B], and [C], respectively, and E represents a weight of an epoxy resin other than [A], [B], and [C].