Patent ID: 8048612

Claim:
A polymer comprising a structural unit represented by the formula (Ia) or (Ib): wherein R 1 represents a hydrogen atom or a methyl group, R 2 represents a linear, branched chain or cyclic C1-C8 alkyl group, R 3 represents a methyl group, n represents an integer of 0 to 14, Z 1 represents a single bond or —[CH 2 ] k —COO—, k represents an integer of 1 to 4, R 4 and R 5 each independently represents a hydrogen atom or a C1-C8 monovalent hydrocarbon group which may have one or more heteroatoms, or R 4 and R 5 may be bonded to form a C1-C8 divalent hydrocarbon group which may have one or more heteroatoms and which forms a ring together with the adjacent carbon atoms to which R 4 and R 5 are bonded, or R 4 and R 5 may be bonded to form a carbon-carbon double bond between the carbon atom to which R 4 is bonded and the carbon atom to which R 5 is bonded, and m represents an integer of 1 to 3, a structural unit represented by the formula (II): wherein R 6 and R 7 each independently represents a hydrogen atom, a methyl group or a hydroxyl group, R 8 represents a methyl group, R 9 represents a hydrogen atom or a methyl group, n′ represents an integer of 0 to 12, Z 2 represents a single bond or —[CH 2 ] k′ —COO—, k′ represents an integer of 1 to 4, R 21 and R 22 each independently represents a hydrogen atom or a C1-C4 alkyl group, and R 23 represents a C1-C30 monovalent hydrocarbon group, and at least one structural unit selected from the group consisting of structural units represented by the formulae (IIIc), (IIIb), (IIIc), (IIId) and (IIIf): wherein R 10 represents a hydrogen atom or a methyl group, R 11 represents a methyl group, R 12 is independently in each occurrence a carboxyl group, a cyano group or a C1-C4 hydrocarbon group, j represents an integer of 0 to 3, a represents an integer of 0 to 5, b represents an integer of 0 to 3, c represents an integer of 0 to (2j+2), Z 3 represents a single bond or a —(CH 2 ) k″ —COO— group, and k″ represents an integer of 1 to 4.