Light directing film

Abstract

A light directing film and an optical system incorporating same are disclosed. The light directing film includes a first major surface and a microstructured second major surface. The microstructured second major surface has at least two periodic microstructured patterns. The first periodic pattern is arranged along a first direction. The second periodic pattern is arranged along a second direction different from the first direction.

1 . A light directing film comprising a first major surface and a second major surface, the second major surface having a two-dimensional microstructured pattern superimposed on a one-dimensional periodic microstructured pattern. 
     
     
         2 . The light directing film of  claim 1 , wherein the two-dimensional microstructured pattern is periodic along at least one direction. 
     
     
         3 . The light directing film of  claim 1 , wherein the two-dimensional microstructured pattern is periodic along at least two different directions. 
     
     
         4 . The light directing film of  claim 1 , wherein each microstructure in the one-dimensional and two-dimensional patterns has a peak and a peak height measured from the peak to a common reference plane disposed between the first and second major surfaces, and wherein the heights of the microstructures in the one-dimensional periodic microstructured pattern are different than the heights of the microstructures in the two-dimensional microstructured pattern. 
     
     
         5 . The light directing film of  claim 4 , wherein at least two microstructures in the two-dimensional microstructured pattern have different heights. 
     
     
         6 . The light directing film of  claim 1 , wherein at least two microstructures in the two-dimensional microstructured pattern have different shapes. 
     
     
         7 . The light directing film of  claim 1 , wherein the microstructures in the one- and two-dimensional patterns extend along a same direction. 
     
     
         8 . The light directing film of  claim 1 , wherein at least some of the microstructures in the one- and two-dimensional patterns are prismatic. 
     
     
         9 . A light guide assembly for use in a liquid crystal display, the light guide assembly comprising at least one light directing film of  claim 1 . 
     
     
         10 . A light directing film comprising a first major surface and a second major surface, the second major surface having a two-dimensional regularly-spaced pattern of discrete elements disposed on a one-dimensional periodic microstructured pattern. 
     
     
         11 . The light directing film of  claim 10 , wherein at least some of the discrete elements are microstructured.