Patent ID: 7201955

Claim:
A privacy screen suitable for use in a non-polarized display comprising: a) an input polarizer having a polarizing axis to define a polarizing axis of the display; b) a first uniaxially birefringent film for transmitting light received through the input polarizer from the display wherein the light is substantially linearly polarized along the polarizing axis, the first birefringent film having a thickness d 1 and a retardation value R: R =( n e −n o ) d 1 /cosθ θ being the angle of light incident upon the screen from the display, and n o and n e being the refractive indices, respectively, along the ordinary and extraordinary axes of the first birefringent film, wherein d 1 is greater than 25 micrometers so that R is responsive to changes in θ; and (c) a first polarizing film having a polarizing axis positioned to receive the substantially linear polarized light transmitted from the first birefringent film.