Patent ID: 7633678
Filing Date: 2009-12-15
Classification: G02B,G02F

Abstract:
1. An optical element, comprising: at least two laminated layers of reflective polarizer; and at least one retardation layer for changing polarization properties laminated between the reflective polarizers, the combination of the layers being designed so as to provide a incident-light transmittance depending on an incident angle of an incident light and designed such that a shielded light is not absorbed but reflected, wherein a first layer of the reflective polarizer is a circular polarization type reflective polarizer capable of transmitting a certain circularly polarized light and selectively reflecting an oppositely circularly polarized light; a second layer of the reflective polarizer is a linear polarization type reflective polarizer capable of transmitting one of perpendicular linearly polarized lights and selectively reflecting the other of the perpendicular linearly polarized lights; and the retardation layer is a layer having a front in a direction normal to the surface of the retardation layer with a retardation value of about λ/4 and having a retardation value of at least λ/8 with respect to an incident light inclined by at least 30° to the normal direction; wherein the retardation layer is a laminate of: a C-plate and a uniaxial retardation layer, wherein the C-plate is a layer having a front in a direction normal to the surface of the C-plate layer with a retardation value of about zero and having a retardation value of at least λ/8 with respect to an incident light inclined by at least 30° to the normal direction; and the uniaxial retardation layer is a layer having a front in a direction normal to the surface of the uniaxial retardation layer with a retardation value of about λ/4 and an Nz coefficient of 1.0, wherein the Nz coefficient is defined by the formula: (nx−nz)/(nx−ny), where nx and ny are each principal in-plane refractive indices, and nz is a principal refractive index in the thickness direction, and the uniaxial retardation layer has a slow axis whose direction is set to make an angle of 45°±5° or −45°±5° with a polarization axis of the linear polarization type reflective polarizer.