A copolymer includes the structure unit represented by the following Chemical formula 1 and the structure unit represented by the following Chemical formula 2,
where R 1 and R 2 each, independently represent hydrogen atoms or methyl groups, and n represents a value in the range of from 1 to 90,
where R 3 represents a hydrogen atom or a methyl group and L represents an alkylene group having 2 to 18 carbon atoms.
