Enhanced electroluminescent sign

Abstract

An enhanced electroluminescent sign containing a volumetric, anisotropic scattering element to control the angular spread of light from the sign and the spatial luminance uniformity of the sign. The anisotropic scattering element contains one or more regions of asymmetrically-shaped light scattering particles. The angular spread of light leaving a sign from a light emitting source can be efficiently controlled by using a thin, low cost, volumetric, anisotropic scattering elements to angularly and spatially distribute light, permitting the reduction in number of light sources, a reduction in power requirements, or a more tailored viewing angle.

1 . An electroluminescent sign comprising: 
 a) at least one light emitting source;    b) a first means for displaying a first set of images or indicia;    c) a light transmitting region comprising a first anisotropic scattering region comprising a first continuous phase material of refractive index n c1  and a first dispersed phase material of refractive index n d1  wherein |n c1 −n d1 |>0.001 and one or more of the first dispersed phase domains are non-spherical in shape disposed to receive light from the light emitting source and scatter light to the means for displaying images or indicia.    
   
   
       2 . The electroluminescent sign of  claim 1  wherein the anisotropic light scattering region increases the spatial luminous uniformity of the light pattern illuminating the means for displaying images or indicia.  
   
   
       3 . The electroluminescent sign of  claim 1  wherein the anisotropic light scattering region increases the spatial color uniformity of the light pattern illuminating the means for displaying images or indicia.  
   
   
       4 . The electroluminescent sign of  claim 2  wherein the spatial uniformity of the light pattern illuminating the means for displaying images or indicia is greater than or equal to 70%.  
   
   
       5 . The electroluminescent sign of  claim 1  wherein the sign emits anisotropic light radiation.  
   
   
       6 . The electroluminescent sign of  claim 1  wherein the light source is selected from the group consisting of fluorescent lamps, cylindrical cold-cathode fluorescent lamp, flat fluorescent lamp, light emitting diode, organic light emitting diode, field emissive lamp, gas discharge lamp, neon lamp, filament lamp, incandescent lamp, electroluminescent lamp, radiofluorescent lamp; halogen lamp; incandescent lamp; mercury vapor lamp; sodium vapor lamp; high pressure sodium lamp; metal halide lamp; tungsten lamp; carbon arc lamp; electroluminescent lamp; laser; photonic bandgap based light source; quantum dot based light source;  
   
   
       7 . The electroluminescent sign of  claim 5  containing more than one light emitting source with the light emitting sources arranged in an array.  
   
   
       8 . The electroluminescent sign of  claim 6  wherein the cross-sectional profile of the light source is substantially longer in the x direction than the y direction.  
   
   
       9 . The electroluminescent sign of  claim 7  wherein the array is a linear array.  
   
   
       10 . The electroluminescent sign of  claim 5  further comprising a reflective element.  
   
   
       11 . The electroluminescent sign of  claim 1  wherein the disperse phase domains are gaseous.  
   
   
       12 . The electroluminescent sign of  claim 4  further comprising a substantially planar output surface wherein the dispersed phase domains are arranged substantially parallel to the output surface.  
   
   
       13 . The electroluminescent sign of  claim 4  further comprising a substantially planar output surface wherein the dispersed phase domains are arranged substantially at an angle δ to the output surface.  
   
   
       14 . The electroluminescent sign of  claim 1  wherein the concentration of the dispersed phase domains varies spatially in the light scattering region.  
   
   
       15 . The electroluminescent sign of  claim 1  wherein the size or shape of the dispersed phase domains varies spatially in the light scattering region.  
   
   
       16 . The electroluminescent sign of  claim 1  wherein the orientation of the dispersed phase domains varies spatially in the light scattering region.  
   
   
       17 . The electroluminescent sign of  claim 1  wherein the light transmitting region further comprises substantially spherical particles.  
   
   
       18 . The electroluminescent sign of  claim 1  wherein the light transmitting region further comprises a light re-directing feature.  
   
   
       19 . The electroluminescent sign of  claim 18  wherein the light re-directing feature is a light collimating feature.  
   
   
       20 . The electroluminescent sign of  claim 19  wherein the light collimating feature is a linear array of prismatic structures.  
   
   
       21 . The electroluminescent sign of  claim 19  wherein the light collimating feature is an array of concave surface relief patterns on a light transmitting material.  
   
   
       22 . The electroluminescent sign of  claim 19  wherein the light collimating feature is a coating containing substantially spherical beads.  
   
   
       23 . The electroluminescent sign of  claim 1  wherein the light transmitting region further comprises a second scattering region disposed to receive light from the light emitting source and direct light to the means for displaying images or indicia, comprising a second continuous phase material of refractive index n c2  and a second dispersed phase material of refractive index n d2  wherein |n c2 −n d2 |>0.001 and one or more of the second dispersed phase domains are non-spherical in shape.  
   
   
       24 . The electroluminescent sign of  claim 23  wherein the first light scattering region is separated from the second light scattering region by a substantially non-scattering region.  
   
   
       25 . The electroluminescent sign of  claim 1  containing refractive materials with one or more refractive indexes selected from a group consisting of: n dx1 ≠n dy1 , n dx1 ≠n dz1 , n dy1 ≠n dz1 , n cx1 ≠n cy1 , n cx1 ≠n cz1 , n cy1 ≠n cz1 .  
   
   
       26 . The electroluminescent sign of  claim 1  wherein at least one light emitting source is disposed to direct light into the light transmitting region of refractive index n 1  such that the light transmitting region is capable of supporting multiple total internal reflections.  
   
   
       27 . The electroluminescent sign of  claim 26  wherein the first light scattering region is disposed such that one or more dispersed phase domains scatters incident light into an angle θ such that  
     
       
         
           
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       28 . The electroluminescent sign of  claim 1  wherein a first set of image or indicia is viewable at a first angle α and further comprising a second means for displaying a second set of image or indicia viewable from a second angle β such that α≠β.  
   
   
       29 . The electroluminescent sign of  claim 28  wherein 0°≦|α−β|≦180°.  
   
   
       30 . The electroluminescent sign of  claim 1  wherein the first means for displaying a first set of images or indicia is selected from a group consisting of: transparency, photograph, picture, graphic, print, painting, light directing channels arranged in the outline of indicia, reflective indicia, light absorbing indicia, light transmitting indicia, perforated material outlining an image or indicia, spatial light modulator, liquid crystal display, electrophoretic display.