High incidence angle retroreflective sheeting

Abstract

A retroreflective sheeting is disclosed which comprises a top transmissive layer including a plurality of parallel channel formed perpendicular to a surface of the layer, and a reflective bottom layer including a specular surface or a corrugated transmitting surface. The corrugated surface includes a plurality of linear prismatic elements extending perpendicular to the channels of the top layer. The top and bottom layers reflect light in orthogonal directions and act cooperatively to retroreflect incident light back toward the source, particularly at high incidence angles. Various light management devices employing the retroreflective sheeting are also disclosed.

What is claimed is: 
     
         1 . A retroreflective sheet structure, comprising:
 a top layer of an optically transmissive material;   a bottom reflective layer; and   a plurality of channels formed within the optically transmissive material of said top layer and configured to reflect light by means of a total internal reflection.   
     
     
         2 . A retroreflective sheet structure as recited in  claim 1 , wherein each of said channels is defined by a pair of opposing walls extending between opposing major surfaces of said top layer parallel to each other and perpendicular to said major surfaces. 
     
     
         3 . A retroreflective sheet structure as recited in  claim 1 , wherein said optically transmissive material is selected from the group of polymeric materials consisting of optically clear or translucent plasticized polyvinyl chloride, thermoplastic elastomers, polyurethanes, and silicones. 
     
     
         4 . A retroreflective sheet structure as recited in  claim 1 , wherein said bottom reflective layer comprises a refractive material selected from the group of consisting of glass, poly(methyl methacrylate), polycarbonate, polystyrene, rigid polyvinyl chloride, polyester, and cyclic olefin copolymer. 
     
     
         5 . A retroreflective sheet structure as recited in  claim 1 , wherein said bottom reflective layer comprises a mirrored surface. 
     
     
         6 . A retroreflective sheet structure as recited in  claim 1 , wherein said bottom reflective layer comprises a linear array of isosceles prisms having substantially perpendicular sides arranged side-by-side to form a plurality of peaks and grooves, and wherein the perpendicular sides of said isosceles prisms make an angle of approximately 45° with a surface plane of said bottom reflective layer. 
     
     
         7 . A retroreflective sheet structure as recited in  claim 6 , wherein the orientation of said plurality of channels is perpendicular to the orientation of said isosceles prisms. 
     
     
         8 . A retroreflective sheet structure as recited in  claim 6 , wherein a depth of said channels is at least 5 times greater than a height of said isosceles prisms. 
     
     
         9 . A retroreflective sheet structure as recited in  claim 1 , wherein a depth of each said channel is at least ten times an average width of the channel. 
     
     
         10 . A retroreflective sheet structure as recited in  claim 1 , wherein a distance between adjacent channels is at least 6 times an average width of the channels. 
     
     
         11 . A light directing sheet material as recited in  claim 1 , wherein said plurality of channels is arranged into a parallel array. 
     
     
         12 . A retroreflective sheet structure as recited in  claim 1 , wherein said plurality of channels is arranged into a first parallel array and a second parallel array having an orientation perpendicular to said first parallel array. 
     
     
         13 . A retroreflective sheet structure as recited in  claim 12 , wherein said first and second array are disposed in a staggered arrangement. 
     
     
         14 . A retroreflective sheet structure as recited in  claim 1 , wherein sad plurality of channels is arranged into an parallel array in which said channels are spaced from each other by a distance that is greater than a depth of each channel by a factor of at least 1.2 and at most 1.8. 
     
     
         15 . A retroreflective sheet structure as recited in  claim 1 , wherein a root mean square surface profile roughness parameter of the walls of said channels is at most about 60 nanometers at a sampling length of between 20 and 100 micrometers. 
     
     
         16 . A retroreflective sheet structure as recited in  claim 1 , wherein a root mean square surface profile roughness parameter of at least a substantial portion of the surface of each of said channels is at least about 10 nanometers at a sampling length of between 20 and 100 micrometers. 
     
     
         17 . A retroreflective sheet structure as recited in  claim 1 , wherein the thickness of said top layer is between 100 micrometers and 1 millimeter. 
     
     
         18 . A retroreflective sheet structure as recited in  claim 1 , wherein at least one of the top and bottom layers comprises light diffusing features. 
     
     
         19 . A retroreflective sheet structure as recited in  claim 1 , wherein either one of said top and bottom layers has a predefined visually conspicuous color or tint. 
     
     
         20 . A retroreflective sheet structure as recited in  claim 1 , wherein at least one edge of said structure is made impermeable to moisture and/or air.