Optical film, illuminator and display

摘要

An optical film is provided for use in a light source or display to provide rapid cut-off of illumination with angle. The film comprises a light-transmissive substrate of a material having a refractive index greater than one and having first and second major surfaces. A surface relief is formed on at least one of the major surfaces and includes a mirror structure. The mirror structure comprises a groups of specularly reflective surfaces alternating in at least one direction with groups of transmissive surfaces. All of the reflective surfaces are non-parallel to the plane in which the surface relief extends and at least some of the reflective surfaces are non-perpendicular to that plane. Light propagating through the film in a first angular input range passes without reflection into a desired angular output range. Light propagating through the film and reflected by the reflective structure passes into the same or an overlapping or adjacent output angular range. Light reflected back by the mirror structure is returned to a light source for recycling to enhance display brightness.