Patent ID: 8114574

Claim:
A photosensitive resin composition, comprising an acid group-containing vinyl ester resin (A) and a photopolymerization initiator (B) as essential components, wherein; the acid group-containing vinyl ester resin (A) has a multiple-branched molecular structure obtained by the following steps; Step (1): reacting a polybasic anhydride (a3) with an epoxy vinyl ester resin (v1) that is a reaction product of a novolac-type epoxy resin (a1), and a radically-polymerizable unsaturated-double bond-containing monocarboxylic acid (a2) to give an acid group-containing vinyl ester resin (v2), which is represented by the following general formula (2), wherein R 1 represents a hydrogen atom or a methyl group; R 2 represents a hydrocarbon group having 2 to 6 carbon atoms; each 1 independently represents an integer of 0 to 6; R 3 represents a linear aliphatic hydrocarbon group or alicyclic hydrocarbon group having 2 to 10 carbon atoms; R 4 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms; and m represents an integer of 0 to 9, Step (2); subsequently reacting a radically-polymerizable unsaturated-double bond-containing monoepoxy compound (a4) with an acid group in the acid-group containing vinyl ester resin (v2) obtained by the Step (1) to give a vinyl ester compound (v3), and Step (3): subsequently reacting a polybasic anhydride (3) with a secondary hydroxyl group in the vinyl ester compound (v3) obtained by the Step (2); and the acid group-containing vinyl ester resin (A) contains 1.75 to 3.5 radically-polymerizable unsaturated double bonds per aromatic ring in the acid group, wherein the radically-polymerizable unsaturated double bonds are derived from the radically-polymerizable unsaturated-double bond-containing monocarboxylic acid (a2) and the radically-polymerizable unsaturated-double bond-containing monoepoxy compound (a4), and the acid groups within a range where the acid value of the acid group-containing vinyl ester resin (A) reaches 30 to 150 mg KOH/g.