Anti-glare, privacy screen for windows or electronic device displays

Abstract

An array of microstructures or frustums on a substrate for reducing glare for electronic device displays or windows. The microstructures are designed to nearly perfectly align with the pixels on the display to avoid adverse viewing effects, such as Moiré effects. Substantially all light from the environment illuminating the front side of the film containing the microstructures from all angles is not reflected to the primary viewer (often viewing at an angle normal to the film). Light illuminating the microstructure from the environment will reflect off the microstructures at angles greater than a defined threshold outside the primary viewers field of view. Thus, glare to the primary viewer is minimized while glare to other views who view from other angles than the primary viewer is increased. This increased glare for other viewers adds privacy for the viewing by the primary viewer.

We claim: 
     
         1 . A privacy screen for a display or a window comprising an array of frustums positioned on a substrate wherein an index of refraction of the substrate is comparable to an index of refraction of the frustum, wherein an index of refraction of the spaces between the frustums is lower than the index of refraction of the frustums, and wherein incoming light is controlled in at least one direction. 
     
     
         2 . The privacy screen of  claim 1  wherein a base of the frustum is larger than the top of the frustum. 
     
     
         3 . The privacy screen of  claim 1  wherein the substrate and the frustums comprise the same material or different materials. 
     
     
         4 . The privacy screen of  claim 1  wherein the frustums are nearly perfectly aligned with pixels of a display. 
     
     
         5 . The privacy screen of  claim 1  comprising an anti-reflective coating, a transparent dielectric coating, or a combination thereof. 
     
     
         6 . The privacy screen of  claim 1  wherein the substrate is flexible, rigid, or a combination thereof. 
     
     
         7 . The privacy screen of  claim 1  wherein the frustums comprise conical frustums, square frustums, pentagonal frustums, hexagonal frustums, octagonal frustums, n-gon frustums, rectangular frustums, diamond frustums, rhombus frustums, quadrilateral frustums, star frustums, donut frustums, irregular polygon frustums, frustums hollowed out by removing a central region of the frustum of a certain shape, or any combination thereof. 
     
     
         8 . The privacy screen of  claim 1  wherein the height of the frustum is like the width of the frustum. 
     
     
         9 . The privacy screen of  claim 1  wherein one or more parameters of the frustums are varied to optimize optical performance, wherein the parameters include height, size, spacing from a center of one frustum to a center of an adjacent frustum, arrangement, rotation of the frustum about an axis normal to a surface of the substrate, angles between a side of the frustum and the base of the frustum, centeredness of the top surface of the frustums with respect to the base of the frustums, index of refraction of the frustums, and combinations thereof. 
     
     
         10 . The privacy screen of  claim 1  wherein a portion of the top surface of the frustum is raised up above the rest of the surface of the frustum or wherein the portion of the top surface of the frustum is raised up is a lip around the perimeter of the top surface of the frustum or a region within the top surface of the frustum, or a mixture thereof. 
     
     
         11 . The privacy screen of  claim 1  wherein the top surfaces of the frustums are co-planar with each other and parallel to the surface of the substrate or wherein the top surfaces of the frustums are parallel to each other but not parallel to the surface of the substrate or wherein a tilt of the top surfaces of the frustums vary by a gradient with respect to the surface of the substrate. 
     
     
         12 . The privacy screen of  claim 1  wherein the frustums comprise steep side walls having a steepness of about 80 degrees from a plane of the surface of the substrate, wherein light illuminating the substrate does not produce significant reflective glare into a primary viewing angle range of about +/−30 degrees with respect to normal to the surface of the substrate, but does produce glare outside of the primary viewing angle range. 
     
     
         13 . The privacy screen of  claim 1  wherein an internal angle of a side of the frustum to the base of the frustum is in the range of about 45 to 90 degrees. 
     
     
         14 . The privacy screen of  claim 1  wherein gaps or no gaps exist between the bases of adjacent frustums in the array. 
     
     
         15 . The privacy screen of  claim 14  wherein the gap between the bases of adjacent frustums comprises a size of about 0-5 times the width of the base of the frustums. 
     
     
         16 . The privacy screen of  claim 1  wherein the frustums are an inverse surface relief of frustums or a mixture of frustums and inverse surface relief of frustums and wherein the inverse surface relief structures have a lower index of refraction than surrounding material. 
     
     
         17 . The privacy screen of  claim 1  wherein a second substrate is bonded to the top surfaces of the frustums, wherein the top surfaces of the frustums are in contact with a surface of the second substrate, wherein the second substrate comprises a same index of refraction as the frustums and a first substrate that comprises the frustums, wherein there is no significant back-scattering of light passing through an interface between the top surfaces of the frustums and the surface of the second substrate, and wherein there is no significant degradation in transmission of light passing through the first substrate, the frustums, and second substrate due to the interfaces. 
     
     
         18 . The privacy screen of  claim 1  wherein a second substrate is in contact with a portion of the top surfaces of each frustum, and wherein the second substrate comprises a same index of refraction as the frustums and the first substrate. 
     
     
         19 . The privacy screen of  claim 1  wherein the frustums are rectangular frustums that extend over the entire privacy screen or beyond the edges of the privacy screen. 
     
     
         20 . A method of fabricating a substrate comprising an array of microstructures or nanostructures on one side of the substrate comprising a photolithography process or a mechanical process; which includes applying a rastering laser beam to develop and form a series of identical or non-identical microstructures or nanostructures wherein the microstructures or nanostructures comprise frustums or inverse frustums, and wherein the developed photoresist can be used to make molds, replicas, final parts, or mixtures thereof.