| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical film with excellent humidity and heat resistance, high strength, few defects due to foreign matters and excellent viewing angle characteristics and a liquid crystal display device using the same. SOLUTION: The optical film is formed with an aliphatic acid cellulose ester film, which is composed of the aliphatic acid cellulose ester with acetyl and propionyl groups and is characterized by exhibiting 60-300 nm retardation value (Rt value) in the thickness direction defined with the formula 1. Rt value = ((nx+ny)/2-nz)×d (formula 1) (nx, ny, nz and d express the refractive index in the direction of the largest refractive index in the film plane, the refractive index in the film plane in the direction vertical to nx, the refractive index in the thickness direction of the film and the film thickness (nm) respectively). |
