Patent ID: 7309736

Claim:
An acrylic block copolymer (A) comprising a methacrylic polymer block (a) and an acrylic polymer block (b), wherein at least one of the polymer blocks contains, in its main chain, at least one acid anhydride group (c) represented by formula (1): (in which R 1 s each represent hydrogen or a methyl group and may be the same or different, n represents an integer of 1 to 3, and m represents an integer of 0 or 1), wherein the acrylic block copolymer contains 0.1% by weight to 99.9% by weight of the acid anhydride group (c), wherein the number-average molecular weight of the acrylic block copolymer is 30,000 to 500,000, wherein the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number-average molecular weight (Mn) according to gel permeation chromatographic measurement is 1 to 1.8, and wherein the acrylic polymer block (b) comprises n-butyl acrylate, ethyl acrylate, and 2-methoxyethyl acrylate.