Patent ID: 7169833

Claim:
A liquid epoxy resin composition comprising (A) 100 parts by weight of a liquid epoxy resin, (B) an aromatic amine curing agent comprising at least 5% by weight of at least one aromatic amine compound having a purity of at least 99% selected from compounds having the following general formulae (1) to (3): wherein each of R 1 to R 4 is hydrogen or a monovalent hydrocarbon group having 1 to 6 carbon atoms, the liquid epoxy resin (A) and the aromatic amine curing agent (B) being present in a molar ratio (A)/(B) from 0.7/1 to less than 0.9/1, (C) 100 to 1,000 parts by weight of an inorganic filler, and (D) an ester organic solvent having a boiling point of 130 to 250° C. and having the general formula (4): R 5 COO—[R 6 —O] n —R 7 (4) wherein R 5 and R 7 each are a monovalent hydrocarbon group having 1 to 6 carbon atoms, R 6 is an alkylene group having 1 to 6 carbon atoms, and n is an integer of 0 to 3 in an amount of 0.5 to 10 parts by weight per 100 parts by weight of components (A) and (B) combined, and the composition having a toughness K 1c of at least 3.5.