Backlight with optical film, illumination device therewith, and display screen

Abstract

A backlight extending in a planar manner, emits light and has an optical film for controlling and limiting a viewing angle range of a viewer. The optical film includes a first polarization layer with a first absorption axis, which forms an angle of from 0° to 30°, inclusive, with a surface normal of the optical film, at least one phase-shifting compensation layer for improving the limiting of the viewing angle range, and a second polarization layer with a second absorption axis oriented parallel to the surface of the optical film. Different configurations and combinations of compensation layers are provided which are formed to be spatially homogeneous and comprise uniaxially or biaxially birefringent materials. The materials and thicknesses of the compensation layers are such that luminance is minimal in a specified solid angle range which does not comprise the entire half-space except for a cone cut out along the viewing direction.