NOVEL COPOLYMER

An object of the present invention is to provide a novel copolymer useful as a pigment dispersing agent in the field of color liquid crystal displays and the like. A copolymer of the present invention contains a block chain (A) comprising at least one repeating unit selected from the group consisting of a repeating unit having a tertiary amino group and a repeating unit having a quaternary ammonium base; and a block chain (B) comprising a repeating unit represented by formula (I) (wherein R 1 represents a hydrogen atom or the like, R 2 and R 3 each independently represent a hydrogen atom or the like, Q represents an oxygen-containing saturated heterocyclic group optionally having an alkyl group as a substituent or the like, and n represents an integer of 0 to 6), and a repeating unit represented by formula (II) (wherein R 4 represents a hydrogen atom or the like and R 5 represents a saturated aliphatic hydrocarbon group or the like), and a copolymerization ratio of the repeating unit represented by formula (II) is 90 wt% or more in the block chain (B) excluding the repeating unit represented by formula (I).