Retardation film, polarizing plate and liquid crystal display device

摘要

A retardation film, contains: a cellulose derivative; and an esterified compound in which all or a part of OH groups in a compounds (A) containing one of a furanose structure and a pyranose structure or in a compound (B) in which 2 to 12 of at lease of a furanose structure and a pyranose structure are bonded, are esterified.

主权项

1. A stretched retardation film, containing:
a cellulose ester having a total acyl substitution degree of 2.1 to 2.55, and an acetyl substitution degree of 1.0 to 2.1; and an esterified compound in which all or a part of OH groups in a compound (B) are esterified, wherein the compound (B) consists of two to three of at least one type of a furanose structure and a pyranose structure which are bonded in the compound (B), wherein the stretched retardation film has a thickness of 30 to 80 μm and is stretched 1.0 to 2.0 times in a width direction so as to exhibit the following retardation values for light having a wavelength of 590 nm under a condition of a temperature of 23° C. and a humidity of 55% RH: an in-plane retardation value Ro represented by a Formula (i) is 20 to 80 nm, a thickness-direction retardation value Rt represented by a Formula (ii) is 100 to 250 nm and a ratio of Rt/Ro is 2.0 to 5.0,
Ro=(nx−ny)×d,  Formula (i):Rt=((nx+ny)/2−nz)×d,  Formula (ii): wherein nx represents a refractive index in a film in-plane slow axis direction, ny represents a refractive index in a direction perpendicular to the slow axis, nz represents a refractive index in a film thickness direction, and d represents a film thickness in nm, wherein the retardation film has a variation of 3 to 20 nm in a thickness direction retardation value due to a humidity change between 20% RH and 80% RH at a temperature of 23° C. when the film has a thickness of 30 to 80 μm.