Solid State Bidirectional Light Sheet for General Illumination

Abstract

A solid state light sheet and method of fabricating the sheet are disclosed. In one embodiment, bare LED chips have top and bottom electrodes, where the bottom electrode is a large reflective electrode. The bottom electrodes of an array of LEDs (e.g., 500 LEDs) are bonded to an array of electrodes formed on a flexible bottom substrate. Conductive traces are formed on the bottom substrate connected to the electrodes. A transparent top substrate having conductors is then laminated over the bottom substrate. Various ways to connect the LEDs in series are described along with many embodiments. The light sheets may be formed to emit light from opposite surfaces of the light sheet, enabling it to be used in a hanging fixture to illuminate the ceiling as well as the floor. The light sheet provides a practical substitute for a standard 2×4 foot fluorescent ceiling fixture.

1 - 18 . (canceled) 
     
     
         19 . A bidirectional lighting device comprising:
 a first substrate comprising a first light emitting surface;   a second substrate comprising a second light emitting surface opposing the first light emitting surface;   a plurality of first non-packaged light emitting diode (LED) dies, and   a plurality of second non-packaged LED dies, the first and second non-packaged LED dies being disposed between the first and second substrates such that during operation of the bidirectional lighting device a peak intensity of light emitted by the first non-packaged LED dies is output from the first light emitting surface in a first direction, and a peak intensity of light emitted by the second non-packaged LED dies is output from the second light emitting surface in a second direction different from the first direction, wherein each die of the first and second non-packaged LED dies has a primary light output face with side walls adjacent the primary light output face;   a plurality of conductors configured to provide power to the first and second non-packaged LED dies, the first and second non-packaged LED dies connected to the conductors without wires, the conductors formed on at least one of the first and second substrate; and   an intermediate sheet between the first and second substrates, the intermediate sheet having holes corresponding to locations of the first and second non-packaged LED dies on the first and second substrates such that each of the first and second non-packaged LED dies is surrounded by walls of a corresponding hole, wherein the intermediate sheet includes a plurality of optical structures configured and arranged to redirect at least some light emitted through the side walls of the first and second non-packaged LED dies and at least some of the redirected light is output from the bidirectional lighting device through the first and second light emitting surfaces in the first and second directions.   
     
     
         20 . The bidirectional lighting device of  claim 19 , wherein the optical structures included in the intermediate sheet comprise reflecting structures. 
     
     
         21 . The bidirectional lighting device of  claim 20 , wherein the reflecting structures are prisms on a bottom or top surface of the intermediate sheet. 
     
     
         22 . The bidirectional lighting device of  claim 19 , wherein the first and second non-packaged LED dies are vertical light emitting diodes. 
     
     
         23 . The bidirectional lighting device of  claim 19 , wherein the first and second non-packaged LED dies are flip-chip light emitting diodes. 
     
     
         24 . The bidirectional lighting device of  claim 19 , wherein the first non-packaged LED dies and the second non-packaged LED dies are connected in series by the plurality of conductors. 
     
     
         25 . The bidirectional lighting device of  claim 19 , wherein the bidirectional lighting device is formed as a light sheet. 
     
     
         26 . The bidirectional lighting device of  claim 25 , wherein the light sheet is suspended from a ceiling so that the second light emitting surface faces the ceiling and the first light emitting surface faces away from the ceiling. 
     
     
         27 . The bidirectional lighting device of  claim 19 , further comprising a wavelength conversion material that fills the holes of the intermediate sheet to encapsulate the corresponding first and second non-packaged LED dies and to convert light emitted through side walls of the first and second non-packaged LED dies to white light. 
     
     
         28 . The bidirectional lighting device of  claim 27 , further comprising a plurality of tiles formed on the first and second substrates at locations corresponding to the first and second non-packaged LED dies, the tiles comprising a wavelength conversion material configured to convert at least some light emitted by the first and second non-packaged LED dies. 
     
     
         29 . The bidirectional lighting device of  claim 27 , further comprising
 a plurality of tiles formed on the first substrate at locations corresponding to the first non-packaged LED dies, the tiles comprising a wavelength conversion material,   wherein the bidirectional lighting device outputs white light in the first direction through the plurality of tiles, and unconverted light emitted by the second non-packaged LED dies in the second direction through the second light emitting surface.   
     
     
         30 . The bidirectional lighting device of  claim 29 , where the unconverted light emitted by the second non-packaged LED dies is blue. 
     
     
         31 . The bidirectional lighting device of  claim 29 , where the unconverted light emitted by the second non-packaged LED dies is UV. 
     
     
         32 . The bidirectional lighting device of  claim 19 , where a light level output by the bidirectional lighting device from the first light emitting surface is modulated differently from a light level output by the bidirectional lighting device from the second light emitting surface. 
     
     
         33 . A bidirectional lighting device comprising:
 a dielectric sheet having a first surface and a second surface opposing the first surface;   a plurality of first non-packaged light emitting diode (LED) dies;   a first substrate sandwiching the first non-packaged LED dies between the first surface of the dielectric sheet and the first substrate, an outer surface of the first substrate forming a first light emitting surface of the bidirectional lighting device through which light is output from the bidirectional lighting device in a first direction;   a plurality of second non-packaged LED dies, wherein each die of the first and second non-packaged LED dies has a primary light output face with side walls adjacent to the primary light output face;   a second substrate sandwiching the second non-packaged LED dies between the second surface of the dielectric sheet and the second substrate, an outer surface of the second substrate forming a second light emitting surface of the bidirectional lighting device through which light is emitted from the bidirectional lighting device in a second direction different from the first direction;   a plurality of first conductors configured to provide power to the first non-packaged LED dies, and a plurality of second conductors configured to provide power to the second non-packaged LED dies, the first and second non-packaged LED dies connected to the first and second conductors without wires, the first conductors formed on at least one of the first substrate and the first surface of the dielectric sheet, and the second conductors formed on at least one of the second substrate and the second surface of the dielectric sheet;   a first intermediate sheet between the first substrate and the dielectric sheet, the first intermediate sheet having first holes corresponding to locations of the first non-packaged LED dies on the first surface of the dielectric sheet, such that each of the first non-packaged LED dies is surrounded by walls of a corresponding first hole, wherein the first intermediate sheet includes a plurality of first optical structures configured and arranged to redirect at least some light emitted through side walls of the first non-packaged LED dies and at least some of the redirected light is output from the bidirectional lighting device through the first light emitting surface in the first direction; and   a second intermediate sheet between the second substrate and the dielectric sheet, the second intermediate sheet having second holes corresponding to locations of the second non-packaged LED dies on the second surface of the dielectric sheet, such that each of the second non-packaged LED dies is surrounded by walls of a corresponding second hole, wherein the second intermediate sheet includes a plurality of second optical structures configured and arranged to redirect at least some light emitted through side walls of the second non-packaged LED dies and at least some of the redirected light is output from the bidirectional lighting device through the second light emitting surface in the second direction.   
     
     
         34 . The bidirectional lighting device of  claim 33 , wherein the dielectric sheet is reflective. 
     
     
         35 . The bidirectional lighting device of  claim 33 , wherein the dielectric sheet is transparent. 
     
     
         36 . The bidirectional lighting device of  claim 33 , wherein
 the first optical structures included in the first intermediate sheet comprise first reflecting structures, and   the second optical structures included in the second intermediate sheet comprise second reflecting structures.   
     
     
         37 . The bidirectional lighting device of  claim 36 , wherein
 the first reflecting structures are first prisms on a surface of the first intermediate sheet adjacent to the first surface of the dielectric sheet, and   the second reflecting structures are second prisms on a surface of the second intermediate sheet adjacent to the second surface of the dielectric sheet.   
     
     
         38 . The bidirectional lighting device of  claim 33 , wherein the first and second non-packaged LED dies are vertical light emitting diodes. 
     
     
         39 . The bidirectional lighting device of  claim 33 , wherein the first and second non-packaged LED dies are flip-chip light emitting diodes. 
     
     
         40 . The bidirectional lighting device of  claim 33 , wherein the first non-packaged LED dies are connected in series by the plurality of first conductors and the second non-packaged LED dies are connected in series by the plurality of second conductors. 
     
     
         41 . The bidirectional lighting device of  claim 33 , wherein the bidirectional lighting device is formed as a light sheet. 
     
     
         42 . The bidirectional lighting device of  claim 41 , wherein the light sheet is suspended from a ceiling so that the second light emitting surface faces the ceiling and the first light emitting surface faces away from the ceiling. 
     
     
         43 . The bidirectional lighting device of  claim 33 , further comprising a wavelength conversion material that
 fills the first holes of the first intermediate sheet to encapsulate the corresponding first non-packaged LED dies,   fills the second holes of the second intermediate sheet to encapsulate the corresponding second non-packaged LED dies, and   converts light emitted through side walls of the first and second non-packaged LED dies to white light.   
     
     
         44 . The bidirectional lighting device of  claim 43 , further comprising multiple tiles formed on the first and second substrates at locations corresponding to the locations of the first and second non-packaged LED dies, respectively, each of the multiple tiles comprising a wavelength conversion material to convert light emitted through the primary light output face of the first and second non-packaged LED dies. 
     
     
         45 . The bidirectional lighting device of  claim 43 , further comprising
 a plurality of tiles formed on the first substrate at locations corresponding to the first non-packaged LED dies, the tiles comprising a wavelength conversion material,   wherein the bidirectional lighting device outputs white light in the first direction through the plurality of tiles, and unconverted light emitted by the second non-packaged LED dies in the second direction through the second light emitting surface.   
     
     
         46 . The bidirectional lighting device of  claim 45 , where the unconverted light emitted by the second non-packaged LED dies is blue. 
     
     
         47 . The bidirectional lighting device of  claim 45 , where the unconverted light emitted by the second non-packaged LED dies is UV. 
     
     
         48 . The bidirectional lighting device of  claim 33 , where a light level output by the bidirectional lighting device from the first light emitting surface is modulated differently from another light level output by the bidirectional lighting device from the second light emitting surface.