ACTIVE ESTER RESIN, THERMOSETTING RESIN COMPOSITION, CURED PRODUCT OF SAME, SEMICONDUCTOR ENCAPSULATION MATERIAL, PREPREG, CIRCUIT BOARD, AND BUILD-UP FILM

摘要

A cured product exhibits good heat resistance and flame retardancy as well as low dielectric constant and low loss tangent. A phosphorus-containing compound (i) obtained by a reaction between an aromatic aldehyde (a1) having an alkoxy group as a substituent on a nucleus and an organic phosphorus compound (a2) having a P—H group or a P—OH group in a molecular structure is reacted with a phenolic substance (a3) to obtain a phosphorus-containing phenolic substance (A1). Then the phosphorus-containing phenolic substance (A1) is reacted with an aromatic dicarboxylic acid or an anhydride or dihalide of an aromatic dicarboxylic acid or a C2-6 saturated dicarboxylic acid or an anhydride or dihalide of a C2-6 saturated dicarboxylic acid (A2) so that all or some of hydroxyl groups of the phenolic substance (A1) form ester bonds.