Optical film, and lighting device and image viewing display using the same

Abstract

An optical film in which at least one layer of a cholesteric liquid crystal layer (1) and a retardation layer (2) are laminated, wherein an in-plane retardation of the retardation layer (2): (nx1−ny1)×Dre is 5 nm or less, and a virtual thickness direction retardation: RZch, and a thickness direction retardation: RZre have a relationship of RZre/(−RZch)=0.05 through 0.35, can be used as a brightness enhancement film, and further that provides an excellent visibility satisfactory also when observed not only from a front direction but from an oblique direction in image viewing displays, such as liquid crystal displays.

Dependencies are inferred from the claim text.