Optical film having microreplicated structures; and methods

Abstract

An optical film for use in transparent displays, such as reflective LCDs. The optical film has three-dimensional, prismatic structures that reflect incoming light. The prismatic structures are configured so that the reflecting facets orient the reflected light in desired reflective light pattern. The pattern shape and intensity can be controlled by the shape and dimensions of the various reflecting facets. In one embodiment, the height of the prismatic structure varies along two dimensions of the structure.

What is claimed is:  
     
         1 . A light directing film having an x-axis, a y-axis, and a z-axis, the film comprising a first structured surface and an opposing surface, the structured surface comprising a plurality of three-dimensional prismatic structures thereon, the prismatic structures: 
 having a height along the z-axis; and    having a repeating height variation along the z-axis; the height variation along the z-axis extending along at least one of the x-axis and the y-axis.    
     
     
         2 . The light directing film according to  claim 1 , wherein the repeating height variation is defined by a repeating wave period along the y-axis.  
     
     
         3 . The light directing film according to  claim 2 , wherein the repeating height variation has a discontinuous slope.  
     
     
         4 . The light directing film according to  claim 1 , wherein the repeating height variation is defined by a repeating wave period along the x-axis.  
     
     
         5 . The light directing film according to  claim 4 , wherein the repeating height variation has a discontinuous slope.  
     
     
         6 . The light directing film according to  claim 1 , wherein the repeating height variation is defined by a repeating wave period along each of the x-axis and the y-axis.  
     
     
         7 . The light directing film according to  claim 6 , wherein the repeating height variation along the x-axis has a discontinuous slope and the repeating height variation along the y-axis has a discontinuous slope.  
     
     
         8 . The light directing film according to  claim 2 , further comprising a volume diffuser.  
     
     
         9 . The light directing film according to  claim 4 , further comprising a volume diffuser.  
     
     
         10 . The light directing film according to  claim 6 , further comprising a volume diffuser.  
     
     
         11 . A light directing film having a structured surfaced constructed to provide, upon introduction of normally incident collimated light, an annular pattern of reflectance on a polar reflectance plot.