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.
