Patent ID: 7247356

Claim:
A privacy screen for a display comprising: a) a first uniaxially birefringent film for transmitting light received from the display that is linearly polarized along a display 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; b) a first polarizing film having a polarizing axis positioned to receive linear polarized light transmitted from the first birefringent film; and wherein: the privacy screen exhibits the following relationship ( n e −n o ) d 1 =(2 n −1)λ/2 where λ is a wavelength of light incident upon the screen from the display, (n e −n o )d 1 is the retardation value R of the first birefringent film for light incident upon the screen normal to the display and n is an integer.