OPTICAL FILM, AND POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE EACH USING THE OPTICAL FILM

摘要

Disclosed is an optical film which can be melt-casted, rarely causes retardation, and has excellent surface quality and physical properties. Disclosed is an optical film which comprises a cellulose ester film having a residual solvent content of 0.01 mass% or less, an in-plane retardation (Ro) of 0 to 10 nm (inclusive), and a thicknesswise retardation (Rth) of-20 to 20 nm (inclusive). In the cellulose ester contained in the cellulose ester film, the types of substituents and the degree of substitution per one glucose unit of the cellulose ester meet all of the requirements represented by the following formulae (1) to (3). 6.7 <= 2×X+3×Y <= 7.4 Formula (1) 2.86 <= X+Y <= 3.00 Formula (2) 1.0 <= Y <= 1.4 Formula (3) wherein X represents the degree of substitution of an acetyl group; and Y represents the degree of substitution of a propionyl group.