Tri-color, white light LED lamps

• US 6,686,691 B1
• Filed: 09/27/1999
• Issued: 02/03/2004
• Est. Priority Date: 09/27/1999
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Mueller-Mach, Regina B, Mueller, Gerd O, Lowery, Christopher H
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): Guharay, Karabi
• Application Number:
  US09/405,947
• Time in Patent Office: 1,590 Days
• Field of Search: 313/501, 313/502, 313/503, 313/506, 313/487, 313/495, 313/496, 313/498, 362/293, 257/100, 257/99, 252/301.63
• US Class Current: 313/503
• CPC Class Codes: C09K 11/7718 with alkaline earth metals
• CPC Class Codes: C09K 11/7731 with alkaline earth metals
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

The present invention relates to a tri-color lamp for generating white light. In particular, the invention relates to a phosphor mixture comprising two phosphors having host sulfide materials that can absorb radiation emitted by a light emitting diode, particularly a blue LED. This arrangement provides a mixing of three light sources—light emitted from the two phosphors and unabsorbed light emitted from the LED. The phosphors can contain the same dopant, such as a rare earth ion, to allow matching of the phosphors in relation to the LED emitted radiation. Power fractions of each of the light sources can be varied to achieve good color rendering. The present invention also relates to an alternative to a green LED comprising a single green phosphor that absorbs radiation from a blue LED. A resulting device provides green light of high absorption efficiency and high luminous equivalent values.

Claims

1. A device comprising:

a light emitting diode, for emitting a pattern of light; and

a composition comprising a mixture of a first phosphor and a second phosphor, each phosphor comprising a host sulfide material and a rare earth dopant, the composition being positioned in the light pattern.

2. The device of claim 1, wherein the dopant is selected from the group consisting of Eu²⁺ and Ce³⁺.

3. The device of claim 2, wherein the dopant is the same in the first and second phosphor.

4. The device of claim 3, wherein the dopant is Eu²⁺.

5. The device of claim 3, wherein the dopant is Ce³⁺.

6. The device of claim 5, wherein the first phosphor is SrGa₂S₄:

Ce.

7. The device of claim 5, wherein the second phosphor is CaS:

Ce.

8. The device of claim 3, wherein the dopant is present in a concentration from about 0.1 mol % to about 8 mol %.

9. The device of claim 8, wherein the first phosphor comprises a SrGa₂S₄ host material and the dopant is present in a concentration from about 2 mol % to about 4 mol %.

10. The device of claim 9, wherein the second phosphor comprises a SrS host material and the dopant is present in a concentration from about 0.3 mol % to about 0.8 mol %.

11. The device of claim 1, wherein the sulfide is selected from the group consisting of CaS, SrS and a thiogallate.

12. The device of claim 11, wherein the thiogallate is Sra₂S₄.

13. The device of claim 1, wherein the first phosphor is capable of being excited by a light emitting diode and the second phosphor is capable of being excited by an emission of the first phosphor.

14. The device of claim 13, wherein each phosphor is capable of being excited by a blue light emitting diode.

15. The device of claim 14, wherein the first phosphor is a green phosphor and the second phosphor is a red phosphor.

16. The device of claim 1, wherein the light emitting diode has an emission at a wavelength from about 450 nm to about 480 nm.

17. The device of claim 16, wherein the device is a lamp.

18. The device of claim 17, wherein the lamp is a white light lamp.

19. The device of claim 18, wherein the lamp is capable of emitting radiation having a color rendering index, Ra of at least about 70 at a color temperature from about 2700 K to about 8000 K.

20. The device of claim 18, wherein the lamp is capable of emitting radiation having a color rendering index, Ra of at least about 80 at a color temperature from about 2700 K to about 8000 K.

21. The device of claim 18, wherein the lamp is capable of emitting radiation having a color rendering index, Ra of at least about 90 at a color temperature from about 2700 K to about 8000 K.

22. The device of claim 1, wherein the first phosphor is a green phosphor and the second phosphor is a red phosphor.

23. The device of claim 22, wherein the first phosphor is SrGa₂S₄:

Eu.

24. The device of claim 22, wherein the second phosphor is selected from the group consisting of SrS:

Eu and CaS;

Eu.

25. A light emitting device comprising:

a light emitting semiconductor device emitting a first light; and

a mixture capable of converting said first light into composite light, said mixture comprising a first phosphor capable of converting said first light from said light emitting semiconductor device into a second light having a second peak in a second spectral range, and a second phosphor capable of converting said first light from the light emitting semiconductor device into a third light having a third peak in a red spectral range; and

means for directing said composite light comprising said first light, said second light, and said third light in a predetermined direction.

26. The device of claim 25, wherein the first phosphor is a green phosphor and the second phosphor is a red phosphor.

27. The device of claim 26, wherein the first phosphor is SrGa₂S₄:

Eu.

28. The device of claim 26, wherein the second phosphor is selected from the group consisting of SrS :

Eu and CaS;

Eu.

29. The device of claim 25, wherein the light emitting semiconductor device is a blue light emitting diode.

30. The device of claim 29, wherein each phosphor is capable of being excited by radiation at a wavelength from about 450 nm to about 480 nm.

31. The light emitting device of claim 25 wherein the second phosphor comprises CaS.

32. The light emitting device of claim 25 wherein the second phosphor comprises SrS.