Patent ID: 7799852

Claim:
A flame retardant epoxy resin composition comprising an epoxy resin (A), a phenolic resin (B), an inorganic filler (C) and a curing accelerator (D): wherein said composition is composed of the inorganic filler (C) and resin components other than the inorganic filler (C) that are comprising the epoxy resin (A), the phenolic resin (B) and the curing accelerator (D), but said composition comprises no flame retardant material nor flame retardant auxiliary; said composition contains the inorganic filler (C) in the equal amount to a content of W (wt %) for the inorganic filler (C) in a cured article being obtained by curing the composition, wherein the W (wt %) is selected in range of 60<W<84.5; the epoxy resin (A) is a combinational mixture of biphenyl-4,4′-diglycidyl ether epoxy resin and 3,3′,5,5′-tetramethylbiphenyl-4,4′-diglycidyl ether epoxy resin represented by formula (4): and the phenolic resin (B) is a phenolbiphenylaralkyl resin represented by formula (10): wherein n=0 to 10; the inorganic filler (C) is one or a mixture of two or more fillers selected from the group consisting of fused silica, and a ratio (OH/Ep) of a phenolic hydroxyl group number (OH) of the total phenolic resin to an epoxy group number (Ep) of the total epoxy resin is 1.0; the moiety of the biphenyl derivative having no hydroxyl group of the phenolic resin is included in a crosslinked structure of the cured article; and a flexural modulus E (kgf/mm 2 ) at 240±20° C. of the cured article is a value satisfying 0.30 W−13≦E≦3.7 W−184 in the case of 60<W<84.5, and the cured article forms a foamed layer during thermal decomposition or at ignition to exert flame retardancy, wherein the level of the resulted flame retardancy is UL94 V-0 in accordance with UL-94 standard for flame retardancy.