| abstract |
The present invention provides a thermosetting resin composition exhibiting excellent heat resistance and flame retardancy while maintaining a low dielectric constant and low dielectric loss tangent when formed into a cured product, a cured product thereof, an active ester resin which develops these properties, and a semiconductor encapsulating material, a prepreg, a circuit board, and a build-up film which are produced using the composition. A thermosetting resin composition contains an active ester resin (A) and an epoxy resin (B) as essential components, the active ester resin (A) having a resin structure which includes a polyaryleneoxy structure (I) and in which aromatic carbon atoms in a plurality of the polyaryleneoxy structures (I) are linked through a structural site (II) represented by a structural formula 1 (wherein Ar represents a phenylene group, a phenylene group nuclear-substituted by 1 to 3 alkyl groups each having 1 to 4 carbon atoms, a naphthylene group, or a naphthylene group nuclear-substituted by 1 to 3 alkyl groups each having 1 to 4 carbon atoms). |