Patent ID: 7042540

Claim:
An optical film in which a polarizing plate and a retardation film are laminated so that an absorbing axis of the polarizing plate and a slow axis of the retardation film may be perpendicular or may be parallel to each other, wherein a value Nz represented by Nz=(nx 1 −nz 1 )/(nx 1 −ny 1 ) of the retardation film satisfies a range of 0.4 through 0.6, and an in-plane retardation Re 1 =(nx 1 −ny 1 )×d 1 of the retardation film is 200 through 350 nm, where a direction of the retardation film in which an in-plane refractive index within the film surface concerned gives a maximum is defined as X-axis, a direction perpendicular to X axis is defined as Y-axis, a thickness direction of the film is defined as Z-axis, refractive indexes in axial direction are defined as nx 1 , ny 1 , nz 1 , respectively, and a thickness of the film is defined as d 1 (nm), and wherein, in the polarizing plate, a first transparent protective film is laminated on one side of a polarizer and a second transparent protective film is laminated on the other side of the polarizer, and the retardation film is laminated on one side of the polarizing plate, wherein an in-plane retardation Re 2 =(nx 2 −ny 2 )×d 2 of each transparent protective film is 20 nm or less, and a thickness direction retardation Rth={(nx 2 +ny 2 )/2−nz 2 }×d 2 of each transparent protective film is 30 nm or less, where a direction of each transparent protective film in which an in-plane refractive index within the film surface concerned gives a maximum is defined as X-axis, a direction perpendicular to X-axis is defined as Y-axis, a thickness direction of the film is defined as Z-axis, refractive indexes in axial direction are defined as nx 2 , ny 2 , and nz 2 , respectively, and a thickness of the film is defined as d 2 (nm).