Light emitting device incorporating a luminescent material

• US 6,967,116 B2
• Filed: 05/26/2004
• Issued: 11/22/2005
• Est. Priority Date: 02/14/2003
• Status: Expired due to Term

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Negley, Gerald H.
• Primary Examiner(s): THAI, LUAN C
• Application Number:
  US10/853,921
• Publication Number:
  US 20040214358A1
• Time in Patent Office: 545 Days
• Field of Search: 438/22, 438/29, 438 46- 47
• US Class Current: 438/22
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder

Abstract

A light emitting device uses a source of exciting radiation such as an light emitting diode to excite a photo luminescent material to provide a source of visible light. The photo luminescent material is loaded into a low density material such as a xerogel or an aerogel which is adjacent the source of exciting radiation.

Claims

1. A method for forming a light emitting device, the method comprising:

loading a sol with a substance which emits a responsive radiation upon interaction with exciting radiation;

forming a porous matrix from the loaded sol; and

placing the porous matrix adjacent a light emitting diode which provides a source of exciting radiation.

2. A method according to claim 1 comprising placing the porous matrix directly on the diode.

3. A method according to claim 1 comprising loading the substance in the sol at a concentration sufficient to produce a desired emission of visible light at a desired level of exciting radiation while avoiding overloading resulting the porous matrix to the point of structural disadvantage.

4. A method according to claim 1 wherein the sol comprises particles of silica.

5. A method according to claim 1 wherein comprising loading the sol with methacryloxypropyltrimethoxysilane.

6. A method according to claim 1 wherein the step of forming the porous matrix comprises forming a xerogel.

7. A method according to claim 1 wherein the step of forming the porous matrix comprises forming an aerogel.

8. A method according to claim 1 wherein the step of loading the sol comprises loading a sol that includes an alcohol as a solvent.

9. A method according to claim 8 wherein the alcohol is selected from the group consisting of ethanol and glycerol.

10. A method according to claim 1 wherein the step of placing the porous matrix adjacent a light emitting device is selected from the group consisting of molding and casting the sol on the light emitting diode.

11. A method according to claim 1 comprising spin coating the sol on the light emitting diode.

12. A method according to claim 1 comprising spray coating the sol on the light emitting diode.

13. A method according to claim 1 comprising dip coating the sol on the light emitting diode.

14. A method according to claim 1 wherein the step of forming the porous matrix comprises drying the sol under supercritical conditions.

15. A method according to claim 1 wherein the step of forming the porous matrix comprises drying the sol gel material under non-supercritical conditions.

16. A method according to claim 1 comprising loading the sol with a phosphor.

17. A method according to claim 16 comprising loading the sol with a phosphor is in the form of particles between about 0.001 microns and about 20 microns.

18. A method according to claim 16 comprising loading the sol with a phosphor is selected from the group consisting of oxides of silicon, aluminum, boron, titanium, zirconium, vanadium, yttrium, magnesium, molybdenum, and iron;

and SiO₂, Si(OCH₃)₄, Si(OC₂H₅)₄, AlOOH, Al(OC₄H₉)₃, B(OC₄H₉)₃, Ti(OC₃H₇)₄, Zr(OC₃H₇)₄, TiO₂, and ZrO₂, YAG, garnet-based phosphors and mixtures of two or more of these.

19. A method according to claim 1 comprising loading the sol by loading the luminescent material in a stock solution in an amount of between about 0.005 and 1.0 gram per cc of stock solution, and then forming the sol from the loaded stock solution.

20. A method according to claim 1 wherein the step of placing the porous matrix adjacent the light emitting diode comprises forming the porous matrix separate from the diode then mechanically placing the porous matrix adjacent the light emitting diode.