Led array between flexible and rigid substrates

Abstract

A light source can include a transparent flexible substrate. A sparse array of light-emitting diodes (LEDs) can be disposed on the transparent flexible substrate. A rigid substrate can be adhered to the transparent flexible substrate such that the sparse array of LEDs is located between the rigid substrate and the transparent flexible substrate. The rigid substrate can be adhered to the transparent flexible substrate with an adhesive layer. The sparse array of LEDs can be encapsulated in an adhesive of the adhesive layer. The adhesive can have a refractive index that is between a refractive index of the transparent flexible substrate and a refractive index of the rigid substrate, inclusive. The sparse array of LEDs can have a light-emitting area that is less than or equal to a specified fraction of a surface area of the sparse array, such as 5 percent or 1 percent.

What is claimed is: 
     
         1 . A light source, comprising:
 a transparent flexible substrate;   a sparse array of light-emitting diodes (LEDs) disposed on the transparent flexible substrate; and   a rigid substrate adhered to the transparent flexible substrate such that the sparse array of LEDs is located between the rigid substrate and the transparent flexible substrate.   
     
     
         2 . The light source of  claim 1 , wherein the rigid substrate is adhered to the transparent flexible substrate with an adhesive layer, the sparse array of LEDs being encapsulated in an adhesive of the adhesive layer. 
     
     
         3 . The light source of  claim 2 , wherein:
 the rigid substrate is substantially transparent; and   the adhesive has a refractive index that is between a refractive index of the transparent flexible substrate and a refractive index of the rigid substrate, inclusive.   
     
     
         4 . The light source of  claim 1 , wherein the rigid substrate is substantially transparent. 
     
     
         5 . The light source of  claim 1 , wherein the sparse array of LEDs has a light-emitting area that is less than or equal to 5% of a surface area of the sparse array. 
     
     
         6 . The light source of  claim 1 , wherein the sparse array of LEDs has a light-emitting area that is less than or equal to 1% of a surface area of the sparse array. 
     
     
         7 . The light source of  claim 1 , further comprising transparent electrical traces configured to electrically power the LEDs of the sparse array of LEDs. 
     
     
         8 . The light source of  claim 1 , wherein the sparse array of LEDs includes two or more LEDs that emit light at a same wavelength. 
     
     
         9 . The light source of  claim 1 , wherein the sparse array of LEDs includes two or more LEDs that emit light at different wavelengths. 
     
     
         10 . The light source of  claim 1 , wherein the rigid substrate is specularly reflective. 
     
     
         11 . The light source of  claim 1 , wherein the rigid substrate is substantially flat. 
     
     
         12 . The light source of  claim 1 , wherein the rigid substrate is curved. 
     
     
         13 . The light source of  claim 1 , wherein the rigid substrate is a single unitary element. 
     
     
         14 . The light source of  claim 1 , wherein the rigid substrate includes multiple rigid substrate elements. 
     
     
         15 . A method for fabricating a light source, the method comprising:
 providing a transparent flexible substrate;   disposing a sparse array of light-emitting diodes (LEDs) on the transparent flexible substrate; and   adhering a rigid substrate to the transparent flexible substrate such that the sparse array of LEDs is located between the rigid substrate and the transparent flexible substrate.   
     
     
         16 . The method of  claim 15 , wherein the rigid substrate is adhered to the transparent flexible substrate with an adhesive layer, the sparse array of LEDs being encapsulated in an adhesive of the adhesive layer. 
     
     
         17 . The method of  claim 16 , wherein the adhesive has a refractive index that is between a refractive index of the transparent flexible substrate and a refractive index of the rigid substrate, inclusive. 
     
     
         18 . A light source, comprising:
 a transparent flexible substrate;   a sparse array of light-emitting diodes (LEDs) disposed on the transparent flexible substrate, the sparse array of LEDs having a light-emitting area that is less than or equal to 10% of a surface area of the sparse array; and   a rigid substrate adhered with an adhesive layer to the transparent flexible substrate such that the sparse array of LEDs is encapsulated in an adhesive of the adhesive layer.   
     
     
         19 . The light source of  claim 18 , wherein the sparse array of LEDs includes two or more LEDs that emit light at a same wavelength. 
     
     
         20 . The light source of  claim 18 , wherein the sparse array of LEDs includes two or more LEDs that emit light at different wavelengths.