OPTICAL FILM, POLARIZING PLATE CONTAINING SAME AND VERTICAL ALIGNMENT LIQUID CRYSTAL DISPLAY DEVICE

摘要

[Problem] To provide an optical film which can achieve a desired retardation value suitable for a vertical alignment (VA) liquid crystal display device while decreasing Rt fluctuations caused by humidity. [Solution] An optical film containing a cellulose ester and a cellulose ether, wherein: the cellulose ester satisfies equations (1) 2.0≤X+Y≤3.0 and (2) 0≤Y≤1.6 (where X is an acetyl group, and Y is a propionyl group and/or a butyryl group); the mixing ratio (cellulose ester : cellulose ether) of the cellulose ester and the cellulose ether is 99.0 : 1.0 to 55.0 : 45.0 (mass ratio); and retardations Ro and Rt expressed in equations (3) Ro=(nx-ny)×d and (4) Rt={(nx+ny)/(2-nz)}×d (where nx is the in-plane refractive index of the film in the slow axis direction, ny is the in-plane refractive index of the film in the fast axis direction, nz is the refractive index of the film in the thickness direction, and d is the thickness (nm) of the film) are 20 to 130 nm and 100 to 300 nm respectively.