Patent ID: 7666509

Claim:
A prepreg obtained by impregnating or applying a thermosetting resin composition into/to a glass woven fabric, wherein the thermo setting resin composition comprises: a bisphenol A type epoxy resin (a) having at least two epoxy groups per molecule and having a secondary hydroxyl group amount of 0.4 meq/g or less, a novolak type epoxy resin (b) having at least two epoxy groups per molecule, a cyanate ester resin (c) having at least two cyanate groups per molecule and spherical silica (d) having an average particle diameter of 4 μm or less, and wherein the amount of the bisphenol A type epoxy resin (a) per 100 parts by weight of a resin solid content in the resin composition is in the range of 15 to 40 parts by weight, the amount of the novolak type epoxy resin (b) per 100 parts by weight of a resin solid content in the resin composition is in the range of 20 to 55 parts by weight, and the equivalent ratio of cyanate groups/epoxy groups in the resin composition is in the range of 0.7 to 1.45.