| 摘要 |
A phase difference film used as an optical film 13 for a polarizing plate 5 includes a cellulose ester and a retardation increasing agent, has a photoelastic coefficient in the range of 7.0×10-13-25.0×10-13 cm2/dyn at a measurement wavelength of 590 nm in an environment at a temperature of 23°C and relative humidity of 55% RH, and has a phase difference Ro in the in-plane direction of 10-150 nm, a phase difference Rth in the thickness direction of 30-400 nm, and a film thickness of 20-45 µm. With regard to degree of substitution, the cellulose ester satisfies both the expressions 1.8 ≤ X + Y ≤ 2.9 and 0.03 ≤ Y ≤ 0.8 (where X represents the degree of substitution of acetyl groups and Y represents the degree of substitution of butyryl groups). |
