| abstract |
An object of the present invention is to provide an optical film having a large retardation value, a small humidity variation of the retardation value, a small photoelastic coefficient, and excellent bonding property with a polarizer. The optical film of the present invention comprises a cellulose ester (A) and a vinyl polymer (B) satisfying the following formulas (1) and (2) regarding the average total substitution degree of the acyl group and the average total carbon number of the acyl group: (B) = 95: contained in a mass ratio of 5 to 50: 50, wherein the vinyl-based polymer, a solubility parameter of 17.5 (MPa 1/2) more than 20.0 (MPa 1/2) is less than consisting of a non-aromatic vinyl monomer It is a polymer, It is characterized by the weight average molecular weight of the said vinyl-type polymer in the range of 500-10,000. Equation (1): 1.0≤X + ΣY i <2.0 Equation (2): 4.0≤2 × X + Σ (n i × Y i ) <6.0 |