Optical element, polarizing element, lighting device, and liquid crystal display

摘要

An optical element of the invention comprises at least two laminated layers of at least one kind of reflective polarizer (a); and at least one layer of at least one kind of retardation layer (b) for changing polarization properties laminated between the reflective polarizers (a), 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 at least one layer of the reflective polarizer (a) is a circular polarization type reflective polarizer (a1) capable of transmitting a certain circularly polarized light and selectively reflecting an oppositely circularly polarized light; at least one layer of the reflective polarizer (a) is a linear polarization type reflective polarizer (a2) capable of transmitting one of perpendicular linearly polarized lights and selectively reflecting the other of the perpendicular linearly polarized lights; and the retardation layer (b) is a layer (b1) having a front (in the normal direction) retardation value of about lambda/4 and having a retardation value of at least lambda/8 with respect to an incident light inclined by at least 30° to the normal direction. The optical element can effectively shield transmitted lights with respect to obliquely incident lights and can control coloring.