Patent ID: 8848132

Claim:
A backlight, comprising: a front reflector and a back reflector that form a hollow light recycling cavity having an output surface, the front reflector comprising: a first directional recycling film comprising a smooth surface and a structured surface opposite the smooth surface, wherein the structured surface comprises an array of prisms elongated along a first axis, and wherein the prisms face away from the back reflector; and a second directional recycling film disposed such that the first directional recycling film is between the second directional recycling film and the back reflector, the second directional recycling film comprising an array of prisms elongated along a second axis; a third directional recycling film disposed such that the second directional recycling film is between the third directional recycling film and the first directional recycling film; a fourth directional recycling film disposed such that the third directional recycling film is between the fourth directional recycling film and the second directional recycling film; a fifth directional recycling film disposed such that the fourth directional recycling film is between the fifth directional recycling film and the third directional recycling film; a semi-specular diffuser disposed between the front reflector and the back reflector; and one or more light sources disposed to emit light into the light recycling cavity over a limited angular distribution related to an emission axis having an average deviation angle from 0° to 45° from a transverse plane parallel to the output surface; and wherein the first axis is substantially parallel to the emission axis.