Polymer film, optically-compensatory film, process for producing the same, polarizing plate and liquid-crystal display device

摘要

A polymer film that has: a ratio R (VT/VM) of a sound velocity in a transverse direction VT to a sound velocity in a machine direction VM of from 1.05 to 1.50; and an in-plane retardation Re(λ) and a thickness-direction retardation Rth(λ) satisfying formula (I): (I) 0≦Re(630)≦10, and |Rth(630)|≦25, wherein Re(λ) represents an in-plane retardation at a wavelength of λ (nm); and Rth(λ) represents a thickness-direction retardation at a wavelength of λ (nm).

主权项

1. A polymer film which is a protecting film for a polarizing plate and that has: a ratio R (VT/VM) of a sound velocity in a transverse direction VT to a sound velocity in a machine direction VM of from 1.05 to 1.50;
a tensile modulus in a transverse direction of from 453 kgf/mm2 to 600 kgf/mm2 (4.44 GPa to 5.88 GPa), a tensile modulus in the machine direction of from 230 kgf/mm2 to 480 kgf/mm2 (2.25 GPa to 4.70 GPa); a ratio of a tensile modulus in a transverse direction to a tensile modulus in a machine direction of from 1.15 to 1.22; an in-plane retardation Re(λ) and a thickness-direction retardation Rth(λ) satisfying formula (I):
0≦Re(630)≦10, and |Rth(630)|≦25  (I) wherein Re(λ) represents an in-plane retardation at a wavelength of λ (nm); and Rth(λ) represents a thickness-direction retardation at a wavelength of λ (nm); and an in-plane retardation Re (λ) and a thickness-direction retardation Rth(λ) satisfying formula (II):
(II) |Re(400)−Re(700)|≦10, and |Rth(400)−Rth(700)|≦14;  (II) wherein Re(λ) represents an in-plane retardation at a wavelength of λ (nm); and Rth(λ) represents a thickness-direction retardation at a wavelength of λ (nm); and Re(n) satisfying formula (III):
|Re(n)−Re(0)|/n≦1.0  (III) wherein Re(n) means the in-plane retardation (nm) of the film having been stretched by n(%), while Re(0) means the in-plane retardation (nm) of the unstretched film, and wherein the polymer film comprises a cellulose acylate which comprises at least two of the acyl substituents consisting of acetyl, propionyl and butanoyl groups, and a total degree of acyl substitution thereof is from 2.50 to 3.00.