Epoxy resin containing silicone-modified epoxy resin and polyvalent carboxylic acid compound, and cured product thereof

An epoxy resin composition comprising the following components (A) to (C):

• (A) a silicone-modified epoxy resin represented by the formula (1),
• wherein R1 represents a monovalent aliphatic hydrocarbon group having 1 to 6 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms;
• X is selected from a group consisting of a 3,4-epoxycyclohexylethyl group and a 3-glycidoxypropyl group;
• n represents an integer of 1 to 3;
• and a plurality of groups R1 or X present in the formula are the same or different from each other;
• (B) a silicone-modified epoxy resin represented by the formula (2),
• wherein R1 and X are each as defined above;
• and a plurality of groups R1 or X present in the formula are the same or different from each other;
• and
• (C) an epoxy resin curing agent containing a polyvalent carboxylic acid represented by the formula (3) and a carboxylic anhydride compound:
• wherein R is selected from the group consisting of methyl, COOH and H, wherein the components (A) to (C) are contained at the following ratios:
• the amount of the component (A) is 20 to 80% by mass with respect to the total amount of the component (A) and the component (B),
• the amount of the component (B) is 20 to 80% by mass with respect to the total amount of the component (A) and the component (B), and
• wherein the mixing ratio is set such that the total number of carboxyl groups and carboxylic anhydride groups in the epoxy resin curing agent (C) is 0.4 to 0.7 mol with respect to 1 mol of the total number of epoxy groups in the whole epoxy resin composition.