Light directing films

Abstract

Light directing films employing at least two layers forming a continuous corrugated boundary between major surfaces of the film. Light received by a major surface of the film is internally redirected by interacting with the facets of the corrugated inter-layer boundary and is emitted from the opposing major surface towards a new propagation direction which is different from the original propagation direction by up to 90 degrees. Light directing films may have additional layers and/or layer boundaries which may provide additional bend angles to light rays or otherwise diffuse the emitted beam.

What is claimed is: 
     
         1 . A light directing structure defined by two opposing broad-area surfaces, comprising:
 a first layer of an optically transmissive material having a first refractive index;
 a second layer of an optically transmissive material having a second refractive index different than the first refractive index; and 
 a corrugated optical interface formed between said first and second layers and characterized by a stepped change in a refractive index, 
 wherein said corrugated optical interface comprises a plurality of facets adjacent to each other and forming different dihedral angles between 0° and 90° with respect to a prevailing plane of said first layer, wherein at least one of said facets is configured to redirect light by means of at least refraction or a total internal reflection. 
   
     
     
         2 . A light directing structure as recited in  claim 1 , wherein said corrugated optical interface represents a boundary between said first and second layers. 
     
     
         3 . A light directing structure as recited in  claim 1 , wherein each of said plurality of facets is planar. 
     
     
         4 . A light directing structure as recited in  claim 1 , wherein at least one of said plurality of facets has a curved surface. 
     
     
         5 . A light directing structure as recited in  claim 1 , wherein said corrugated optical interface comprises a repeating pattern of prismatic structures. 
     
     
         6 . A light directing structure as recited in  claim 1 , wherein said plurality of facets forms a continuous prismatic pattern. 
     
     
         7 . A light directing structure as recited in  claim 1 , wherein said first layer of an optically transmissive material comprises prismatic surface structures. 
     
     
         8 . A light directing structure as recited in  claim 1 , wherein said corrugated optical interface comprises linear prismatic structures extending parallel to a reference line. 
     
     
         9 . A light directing structure as recited in  claim 1 , wherein a surface of said first layer of an optically transmissive material is mirrored. 
     
     
         10 . A light directing structure as recited in  claim 1 , wherein a surface of said first layer of an optically transmissive material is configured for an unimpeded transversal light passage. 
     
     
         11 . A light directing structure as recited in  claim 1 , wherein a surface of said first layer is made attachable to a surface of an optical waveguide. 
     
     
         12 . A light directing structure as recited in  claim 1 , wherein a surface of said first layer comprises a light diffusing surface texture. 
     
     
         13 . A light directing structure as recited in  claim 1 , wherein outer surfaces of said first and second layers are generally smooth and transparent. 
     
     
         14 . A light directing structure as recited in  claim 1 , wherein the material of one of said first and second layers is selected from low-n fluoropolymers or resins. 
     
     
         15 . A light directing structure as recited in  claim 1 , wherein the lower of the two refractive indices of said first and second layers is less than 1.49. 
     
     
         16 . A light directing structure as recited in  claim 1 , further comprising a third layer of an optically transmissive material adjacent to said first layer of an optically transmissive material and optically coupled to said first layer. 
     
     
         17 . A light directing structure as recited in  claim 1 , wherein said first and second layers are stacked on top of another structure having a corrugated optical interface formed between layers of different refractive index materials.