Patent ID: 7098276

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 obtainable by curing the composition, wherein the W (wt %) is selected in range of 60<W≦95; the phenolic resin (B) is one or a mixture of two or more phenolic resins containing biphenyl derivative having no hydroxyl group in the molecule represented by formula (10): wherein n=0 to 10, the epoxy resin (A) is a mixture of a phenolbiphenylaralkyl epoxy resin containing a biphenyl derivative having no epoxy group in the molecule represented by formula (2): wherein n=0 to 10, and a tetraphenylolethane epoxy resin consisting essentially of an epoxy resin represented by formula (3): wherein the ratio of the tetraphenylolethane epoxy resin consisting essentially of an epoxy resin represented by formula (3) to the phenolbiphenylaralkyl epoxy resin of formula (2) is ⅕, the inorganic filler (C) is one or a mixture of two or more fillers selected from the group consisting of fused silica, crystalline silica, or silicon nitride, 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≦(OH/Ep)≦2.5; the moiety of the biphenyl derivative having no hydroxyl group 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≦95, and the cured article forms a foamed layer during thermal decomposition or at ignition to exert flame retardancy.