TECHNOLOGY FOCUS - POLYMERS - Preferred Parameter: The absolute value of refractive index difference of rubber-like polymer comprised from graft copolymer and matrix comprised from heat-resistant acrylic resin is less than or equal to 0.01. The weight average particle diameter of rubber-like polymer is 0.05-0.35 (preferably 0.05-0.15) mu m. The in-plane retardation (Re) of retardation film which satisfies formula nx=ny not greater than nz in which nx is refractive index of slow axis direction in film plane, ny is refractive index of direction perpendicular to slow axis direction in film plane and nz is refractive index of film thickness direction is 40-1100 nm. The retardation film has in-plane retardation (Re) of not greater than 40 nm and thickness direction retardation (Rth) of less than or equal to - 20 nm. The in-plane retardation (Re) of retardation film which satisfies formula ny not greater than nx=nz is not greater than 40 nm. Preferred Composition: The content of unsaturated nitrile compound in acetone soluble component in each of graft copolymer and unsaturated nitrile type copolymer is 15-30 mass%. The aromatic vinyl compound in rubber-like polymer of graft copolymer is conjugated diene type rubber. The unsaturated nitrile compound in rubber-like polymer of graft copolymer is styrene acrylonitriles. The unsaturated nitrile compound is acrylonitrile. The aromatic vinyl compound of unsaturated nitrile type copolymer is styrene. The heat-resistant acrylic resin has methacrylic ester unit and/or acrylic ester units (40-90 mass%), aromatic vinyl compound units (5-40 mass%) and compound units of formula (1) as heat-resistant acrylic resin (C-1) (5-20 mass%). The ratio of copolymerization ratio of aromatic vinyl compound unit with respect to copolymerization ratio of compound unit is 1-3. The quantity of rubber-like polymer with respect to 100 mass parts of resin compositions is 0.5-15 mass parts.X=O or N-R; andR=H, alkyl group, aryl group or cycloalkane group.