| 摘要 |
A cellulose ester film exhibiting: a free volume radius of 0.25 to 0.31 nm and a half-width of 0.04 to 0.1 nm, the free volume radius and the half-width being determined by positron annihilation lifetime spectroscopy; and Ro of 0 to 10 nm and Rt of -30 to ⇄20 nm, Ro and Rt being defined by the following equations: Equation (a): Ro=(nx-ny)xd; Equation (b): Rt=((nx+ny)/2-nz)xd (Ro: in-plane retardation, Rt: retardation in the thickness direction of the film, nx: in-plane refractive index in slow axis direction, ny: in-plane refractive index in fast axis direction, nz: refractive index in the thickness direction of the film (refractive indexes being measured at wavelength of 590 nm), d: thickness of the film (nm)).
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