The present invention provides a polymer compound which comprises both repeating unit “a” represented by the following general formula (1-1) and repeating unit “b” represented by the following general formula (1-2), and has a weight average molecular weight in the range of 1,000 to 500,000,
wherein R
1
represents a hydrogen atom or a methyl group, R
2
represents a single bond, an ester group, or a linear, branched, or cyclic hydrocarbon group having 1 to 12 carbon atoms which may have either or both of an ether group and an ester group, Z represents a phenylene group, a naphthylene group, or an ester group, and “a” and “b” satisfy 0