Patent ID: 7504139
Filing Date: 2009-03-17
Classification: C08J,C08L,C09K,G02B,G02F

Abstract:
1. A cellulose acylate film, which comprises a cellulose acylate, wherein the cellulose acylate is a mixed fatty acid ester of a cellulose; a hydroxyl group of the cellulose is substituted by an acetyl group; and another hydroxyl group of the cellulose is substituted by an acyl group having 3 or more carbon atoms, wherein, the cellulose acylate satisfies formulae (I) and (II): wherein A is a degree of substitution by the acetyl group; and B is a degree of substitution by the acyl group having 3 or more carbon atoms; wherein the acyl group having 3 or more carbon atoms comprises a butanoyl group; and wherein Re(λ) and Rth(λ), which are defined by formulae (III) and (IV), satisfy formulae (V) and (VI): wherein Re(λ) is a retardation value in a film plane of the cellulose acylate film at a wavelength of λ nm, and the retardation value is expressed in nm; Rth(λ) is a retardation value in a direction perpendicular to the film plane at the wavelength of λ nm, and the retardation value is expressed in nm; nx is a refractive index along a slow axis in the film plane; ny is a refractive index along a fast axis in the film plane; nz is a refractive index along the direction perpendicular to the film plane; and “d” is a film thickness of the cellulose acylate film.