| abstract |
PROBLEM TO BE SOLVED: To provide an optical film having excellent wet heat durability, high strength, few foreign matter defects, and excellent viewing angle characteristics, and a liquid crystal display device using the same. SOLUTION: It has a fatty acid cellulose ester having an acetyl group and a propionyl group, and has a retardation value (Rt value) in a thickness direction defined by Formula 1 of 60 to 300 n. m, an optical film comprising a fatty acid cellulose ester film. In Rt value = ((n x + n y ) / 2-n z) × d ( wherein 1) (n x is a refractive index of the largest and the direction of the refractive index in the film plane, n y is the direction perpendicular to n x Refractive index in the film plane of nz represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film. ) |