Patent ID: 7611760

Claim:
A cellulose acylate film having an elasticity modulus of 4,800 MPa to 10,000 MPa in at least one direction of a machine direction MD in producing of the cellulose acylate film and a transverse direction TD perpendicular to the machine direction, the cellulose acylate film having an in-plane retardation Re(λ) satisfying Expression: 20 nm ≦Re(590)≦200 nm and a thickness-direction retardation Rth(λ) satisfying Expression: 70 nm≦Rth(590)≦350 nm, and the cellulose acylate film having a thickness of 40 μm to 150 μm; wherein the cellulose acylate film comprises mixed fatty acid ester of cellulose, wherein a hydroxyl group of the cellulose is substituted by an acetyl group, another hydroxyl group of the cellulose is substituted by an acyl group having 3 or more carbon atoms, and the cellulose acylate film satisfies Expressions (I) and (II): 2.0≦ A+B≦ 3.0 (I) 0<B (II) wherein A represents a substitution degree of the acetyl group, and B represents a substitution degree of the acyl group having 3 or more carbon atoms; and wherein the mixed fatty acid ester of cellulose is a cellulose acylate comprising a glucose unit, wherein a hydroxyl group of the glucose unit is substituted by the acetyl group or the acyl group having 3 or more carbon atoms, and the cellulose acylate film satisfies Expressions (III) and (IV): 2.0 ≦DS 2 ≦DS 3 ≦DS 6≦2.85 (III) DS 6/( DS 2 +DS 3 DS 6)≧0.315 (IV) wherein DS2 represents a substitution degree of the acyl group for a 2-position hydroxyl group of the glucose unit, DS3 a substitution degree of the acyl group for a 3- position hydroxyl group of the glucose unit, and DS6 a substitution degree of the acyl group for a 6-position hydroxyl group of the glucose unit.