A vinyl resin (V1) obtainable by polymerizing monomer components including a monomer (X) represented by the formula : wherein M 1 is a residue of an active hydrogen-containing organic compound having a valence of 1 to 20 from which c number of active hydrogen atoms are removed; c is an integer satisfying 1 ≤ c ≤ (valence of M 1 ); R 1 is an ethylenic unsaturated bond-containing group, and when the formula includes multiple R 1 's, they may be the same as or different from each other; M 2 is a residue of an active hydrogen-containing organic compound having a valence of 1 to 20 from which one active hydrogen atom is removed, and when the formula includes multiple M 2 's, they may be the same as or different from each other, and M 2 and M 1 may be the same as or different from each other; L is a residue of an aromatic polycarboxylic acid having 3 or more carboxyl groups from which all the carboxyl groups are removed, the aromatic ring of L is constituted by carbon atoms, and each of the carbon atoms may optionally have a halogen atom and/or a substituent which is not a carboxyl group, but at least one of the carbon atoms has a hydrogen atom; a and b are each an integer of 0 or greater and they satisfy 2 ≤ (a + b) ≤ (d - 2), when the formula includes multiple a's, they may be the same as or different from each other and at least one of c number of a's is not 0, and when the formula includes multiple b's, they may be the same as or different from each other; and d is the number of hydrogen atoms bonded to the carbon atoms constituting the aromatic ring assuming that all the substituents including the carboxyl groups of the aromatic polycarboxylic acid are replaced by hydrogen atoms, in other words, the number of moieties capable of being replaced by a substituent on the aromatic ring. M 1 is a residue of an active hydrogen-containing organic compound having a valence of 1 to 20 from which c number of active hydrogen atoms are removed; c is an integer satisfying 1 ≤ c ≤ (valence of M 1 ); R 1 is an ethylenic unsaturated bond-containing group, and when the formula includes multiple R 1 's, they may be the same as or different from each other; M 2 is a residue of an active hydrogen-containing organic compound having a valence of 1 to 20 from which one active hydrogen atom is removed, and when the formula includes multiple M 2 's, they may be the same as or different from each other, and M 2 and M 1 may be the same as or different from each other; L is a residue of an aromatic polycarboxylic acid having 3 or more carboxyl groups from which all the carboxyl groups are removed, the aromatic ring of L is constituted by carbon atoms, and each of the carbon atoms may optionally have a halogen atom and/or a substituent which is not a carboxyl group, but at least one of the carbon atoms has a hydrogen atom; a and b are each an integer of 0 or greater and they satisfy 2 ≤ (a + b) ≤ (d - 2), when the formula includes multiple a's, they may be the same as or different from each other and at least one of c number of a's is not 0, and when the formula includes multiple b's, they may be the same as or different from each other; and d is the number of hydrogen atoms bonded to the carbon atoms constituting the aromatic ring assuming that all the substituents including the carboxyl groups of the aromatic polycarboxylic acid are replaced by hydrogen atoms, in other words, the number of moieties capable of being replaced by a substituent on the aromatic ring. <EOS>