Patent ID: 8779076

Claim:
A thermoplastic acrylic resin comprising: 10 to 70% by weight of a repeating unit derived from a methacrylate monomer represented by the following formula (1); 5 to 40% by weight of a repeating unit derived from a vinyl aromatic monomer represented by the following formula (2); 0.1 to 3% by weight of a repeating unit derived from an aromatic group-containing methacrylate monomer represented by the following formula (3); and 20 to 50% by weight of a cyclic acid anhydride repeating unit represented by the following formula (4) or (5), said thermoplastic acrylic resin as a weight-average molecular weight in the average of 10,000 to 400,000 and a molecular weight distribution in the range of 1.8 to 3.0 determined by a GPC measurement method: wherein R 1 represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms, wherein R 2 is a hydrogen and R 3 represents hydrogen, halogen, a hydroxyl group, an alkoxy group, a nitro group, or a linear or branched alkyl group having 1 to 12 carbon atoms, and I represents an integer of 1 to 3, wherein R 4 represents hydrogen, halogen, a hydroxyl group, an alkoxy group, a nitro group, or a linear or branched alkyl group having 1 to 12 carbon atoms, m represents an integer of 1 to 3, and n represents an integer of 0 to 2, wherein R 5 to R 8 may be the same or different and each represents hydrogen or a linear or branched alkyl group having 1 to 12 carbon atoms, and wherein the thermoplastic acrylic resin further satisfies the following optical property (iii): (iii) an absolute value of retardation (Re) in the in-plane direction is not higher than 30 nm.