ACTIVE ESTER RESIN, THERMOSETTING RESIN COMPOSITION, CURED PRODUCT THEREOF, SEMICONDUCTOR SEALING MATERIAL, PREPREG, CIRCUIT BOARD, AND BUILD-UP FILM

摘要

PROBLEM TO BE SOLVED: To provide a cured product having excellent heat resistance and flame retardancy while ensuring a low dielectric constant and a low dielectric loss tangent.SOLUTION: A cured product uses an active ester resin having a resin structure obtained by reacting a phenolic resin having a structural moiety represented by structural formula (I) [wherein Ar represents a benzene ring or a naphthalene ring; Fc represents a hydrogen atom or a hydroxyl group; and Z represents 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide residue] with an aromatic monocarboxylic acid or a halide thereof, or a 2-6C saturated fatty acid, a halide thereof or an acid anhydride of the saturated fatty acid in such a way that at least one of hydroxyl groups present in the phenolic resin forms an ester bond.