Patent ID: 7388636

Claim:
An optical film for a liquid crystal display obtained by laminating a polarizing plate and a retardation film so that an absorption axis of the polarizing plate and a slow axis of the retardation film are perpendicular or parallel to each other, wherein the optical film is applied to an IPS mode liquid crystal display comprising a liquid crystal cell driven in IPS mode, wherein the polarizing plate comprises a transparent protective film on both surfaces of a polarizer and if a direction on the transparent protective film in which an in-plane refractive index is maximized is X axis, a direction perpendicular to X axis is Y axis, a direction of the film thickness is Z axis; and refractive indexes at 550 nm in the respective axes directions are nx 1 , ny 1 and nz 1 ; and a thickness of the film is d 1 (nm) by definition, an in-plane retardation Re 1 =(nx 1 −ny 1 )×d 1 is 10 nm or less and a thickness direction retardation Rth={(nx 1 +ny 1 )/2−nz 1 }×d 1 is in the range of from 30 nm to 100 nm, and wherein if a direction on the retardation film in which an in-plane refractive index is maximized is X axis, a direction perpendicular to X axis is Y axis, a direction perpendicular to X axis is Y axis, a direction of the film thickness is Z axis; and refractive indexes at 550 nm in the respective axes directions are nx 2 , ny 2 and nz 2 ; and a thickness of the film is d 2 (nm) by definition, the following relations are satisfied: an Nz value represented by Nz=(nx 2 −nz 2 )/(nx 2 −ny 2 ) is in the range of from 0.25 to 0.8 and an in-plane retardation Re 2 =(nx 2 −ny 2 )×d 2 is in the range of from 60 to 300 nm.