Abstract: To provide a novel fumaric acid diester-cinnamic acid ester-based copolymer having a high molecular weight, which is expected to maintain excellent strength or ensures excellent toughness even when formed into a film, a method for efficiently producing the copolymer, and a film using the same. The fumaric acid diester-cinnamic acid ester-based copolymer contains a fumaric acid diester residue unit, a cinnamic acid ester residue unit having an alkyl group with a carbon number of 1 to 6, and a residue unit of a polyfunctional monomer having two or more radical polymerizable functional groups.

Abstract: A resin composition containing a specific cellulose-based resin and a specific fumaric acid diester polymer in a specific blending ratio or containing, as the resin component, a specific cellulose-based resin and a specific fumaric acid diester polymer in a specific blending ratio and containing the resin component and an additive having an aromatic hydrocarbon ring or the like in a specific blending ratio. An optical compensation film can be produced using the resin composition.

Abstract: A fumaric acid diester based resin containing a dipropyl fumarate residue unit and a fumaric acid diester residue unit having a C1 or C2 alkyl group, wherein in a retardation film composed of the resin, when a refractive index in the fast axis direction within the film plane is designated as nx, a refractive index in the film in-plane direction orthogonal thereto is designated as ny, and a refractive index in the thickness direction of the film is designated as nz, the respective refractive indices are satisfied with a relationship of (nx?ny<nz) and a relationship between a film thickness and an out-of-plane retardation measured at a wavelength of 550 nm and expressed by the specific equation is 4.5 nm/film thickness (?m) or more in terms of an absolute value.

Abstract: To provide a novel fumaric acid diester-cinnamic acid ester-based copolymer having a high molecular weight, which is expected to maintain excellent strength or ensures excellent toughness even when formed into a film, a method for efficiently producing the copolymer, and a film using the same. The fumaric acid diester-cinnamic acid ester-based copolymer contains a fumaric acid diester residue unit, a cinnamic acid ester residue unit having an alkyl group with a carbon number of 1 to 6, and a residue unit of a polyfunctional monomer having two or more radical polymerizable functional groups.

Abstract: A resin composition containing a specific cellulose-based resin and a specific fumaric acid diester polymer in a specific blending ratio or containing, as the resin component, a specific cellulose-based resin and a specific fumaric acid diester polymer in a specific blending ratio and containing the resin component and an additive having an aromatic hydrocarbon ring or the like in a specific blending ratio. An optical compensation film can be produced using the resin composition.

Abstract: A fumaric acid diester based resin containing a dipropyl fumarate residue unit and a fumaric acid diester residue unit having a C1 or C2 alkyl group, wherein in a retardation film composed of the resin, when a refractive index in the fast axis direction within the film plane is designated as nx, a refractive index in the film in-plane direction orthogonal thereto is designated as ny, and a refractive index in the thickness direction of the film is designated as nz, the respective refractive indices are satisfied with a relationship of (nx?ny<nz) and a relationship between a film thickness and an out-of-plane retardation measured at a wavelength of 550 nm and expressed by the specific equation is 4.5 nm/film thickness (?m) or more in terms of an absolute value.