Patent ID: 8349921

Claim:
An optical film made from a composition comprising: (a) a mixed cellulose ester having: (i) at least one acetyl group and at least one non-acetyl ester group, (ii) a ratio of the degree of substitution of non-acetyl ester groups to the degree of substitution of hydroxyl groups of 10 or greater, and (iii) a non-acetyl ester degree of substitution of 1.1 to 1.75; and (b) a plasticizer selected from the group consisting of xylitol pentaacetate (XPA), xylitol pentapropionate (XPP), arabitol pentapropionate (APP), a polyester comprising succinic acid residues and diethylene glycol residues, and a polyester comprising adipic acid residues and diethylene glycol residues, wherein the film has an optical retardation value in the thickness direction (R th ) of +50 to +130 nm measured at a film thickness of 80 μm or less and at a light wavelength of 633 nm.