Novel phosphor systems for a white light emitting diode (LED)

• US 20060027781A1
• Filed: 08/04/2004
• Published: 02/09/2006
• Est. Priority Date: 08/04/2004
• Status: Active Grant

• Current Assignee: Intematix Corporation
• Original Assignee: Intematix Corporation
• Inventors: Dong, Yi, Cheng, Shifan, Li, Yi-Qun, Wang, Ning
• Granted Patent: US 7,267,787 B2
• Time in Patent Office: Days
• US Class Current: 252/62.520
• CPC Class Codes: C09K 11/592 Chalcogenides
• CPC Class Codes: C09K 11/7734 Aluminates
• CPC Class Codes: C09K 11/77342 Silicates
• 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

Novel phosphor systems for a white LED are disclosed. The phosphor systems are excited by a non-visible to near-UV radiation source having an excitation wavelength ranging from about 250 to 420 nm. The phosphor system may comprise one phosphor, two phosphors, and may include optionally a third and even a fourth phosphor. In one embodiment of the present invention, the phosphor is a two phosphor system having a blue phosphor and a yellow phosphor, wherein the long wavelength end of the blue phosphor is substantially the same wavelength as the short wavelength end of the yellow phosphor. Alternatively, there may be a wavelength gap between the yellow and blue phosphors. The yellow phosphor may be phosphate or silicate-based, and the blue phosphor may be silicate or aluminate-based. Single phosphor systems excited by non-visible radiation are also disclosed. In other embodiments of present invention, a single phosphor is used to produce white light illumination, the single phosphor having a broad emission spectrum with a peak intensity ranging from about 520 to 560 nm.

Claims

1. A white LED comprising:

a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;

a yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 530 to 590 nm; and

a blue phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with peak intensity in a wavelength ranging from about 470 to 530 nm.

2. The white LED of claim 1, wherein a 250 to 400 nm portion of the radiation emitted by the radiation source is substantially non-visible ultraviolet (UV) radiation, and a 400 to 420 nm portion is near-UV.

3. The white LED of claim 1, wherein the radiation source comprises a light emitting diode (LED).

4. The white LED of claim 3, wherein the radiation source comprises at least one semiconductor layer selected from the group consisting of GaN, ZnSe, and SiC, and at least one active region comprising ap-n junction selected from the group consisting of GaN, AlGaN, InGaN, and InAlGaN.

5. The white LED of claim 1, wherein the yellow phosphor is selected from the group consisting of silicate-based phosphors and phosphate-based phosphors.

6. The white LED of claim 5, wherein the yellow phosphor has the formula A₂SiO₄:

Eu²⁺F, and wherein A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd.

7. The white LED of claim 6, wherein the yellow phosphor has the formula Sr_1-x-yBa_xCa_ySiO₄:

Eu⁺²F; and

where

0≦

x≦

0.8; and

0≦

y≦

0.8.

8. The white LED of claim 6, wherein the yellow phosphor has the formula Sr_1-x-yBa_xCa_ySiO₄:

Eu²⁺F; and

where

0≦

x≦

0.5; and

0≦

y≦

0.3.

9. The white LED of claim 6, wherein the yellow phosphor has the formula Sr_1-x-yBa_xCa_ySiO₄:

Eu²⁺F; and

where

0.5≦

x≦

0.7; and

0.2≦

y≦

0.5.

10. The white LED of claim 5, wherein the yellow phosphor has the formula (Sr_1-x-yEu_xMn_y)₂P_2+zO₇;

and where

0.03≦

x≦

0.08;

0.06≦

y≦

0.16; and

0<

z≦

0.05.

11. The white LED of claim 1, wherein the blue phosphor is selected from the group consisting of silicate-based phosphors and aluminate-based phosphors.

12. The white LED of claim 11, wherein the blue phosphor has the formula Sr_1-x-yMg_xBa_ySiO₄:

Eu²⁺F; and

where

0.5≦

x≦

1.0; and

0≦

y≦

0.5.

13. The white LED of claim 11, wherein the blue phosphor has the formula Sr_1-xMgEu_xAl₁₀O₁₇;

and where

0.01<

x≦

1.0.

14. The white LED of claim 11, wherein the blue phosphor has the formula Sr_xAl₁₄O₂₅:

Eu⁺², and where

x<

4.

36. The white light illumination system of claim 1, wherein the ratio of the yellow phosphor to the blue phosphor ranges from about 9 to 1.

38. White light illumination produced by the white LED of claim 1.

41. The white light illumination according to claim 38, wherein the white light illumination comprises about 10 to 50 percent light emitted by the blue phosphor and about 50 to 90 percent light emitted by the yellow phosphor.

43. The white light illumination according to claim 1, wherein the white light illumination has a color temperature ranging from about 3000 to 6500 K.

46. The white light illumination according to claim 1, wherein the white light illumination has a color rendering index (CRI) greater than about 70.

15. A white LED comprising:

a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;

a yellow phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with a peak intensity in a wavelength ranging from about 550 to 590 run; and

a blue phosphor configured to absorb at least a portion of the radiation from the radiation source and emit light with a peak intensity in a wavelength ranging from about 480 to 510 nm.

16. The white LED of claim 15, wherein a 250 to 400 nm portion of the radiation emitted by the radiation source is substantially non-visible ultraviolet (UV) radiation, and a 400 to 420 nm portion is near-UV.

17. The white LED of claim 15, wherein the radiation source comprises a light emitting diode (LED).

18. The white LED of claim 17, wherein the radiation source comprises at least one semiconductor layer selected from the group consisting of GaN, ZnSe, and SiC, and at least one active region comprising ap-n junction selected from the group consisting of GaN, AlGaN, InGaN, and InAlGaN.

19. The white LED of claim 15, wherein the yellow phosphor is selected from the group consisting of silicate-based phosphors and phosphate-based phosphors.

20. The white LED of claim 19, wherein the yellow phosphor has the formula A₂SiO₄:

Eu²⁺F, and wherein A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd.

21. The white LED of claim 20, wherein the yellow phosphor has the formula Sr_1-x-yBa_xCa_ySiO₄:

Eu⁺²F; and

where

0≦

x≦

0.8; and

0≦

y≦

0.8.

22. The white LED of claim 20, wherein the yellow phosphor has the formula Sr_1-x-yBa_xCa_ySiO₄:

Eu²⁺F; and

where

0≦

x≦

0.5; and

0≦

y≦

0.3.

23. The white LED of claim 20, wherein the yellow phosphor has the formula Sr_1-x-yBa_xCa_ySiO₄:

Eu²⁺F; and

where

0.5≦

x≦

0.7; and

0.2≦

y≦

0.5.

24. The white LED of claim 19, wherein the yellow phosphor has the formula (Sr_1-x-yEu_xMn_y)₂P_2+zO₇;

and where

0.03≦

x≦

0.08;

0.06≦

y≦

0.16; and

0<

z≦

0.05.

25. The white LED of claim 15, wherein the blue phosphor is selected from the group consisting of silicate-based phosphors and aluminate-based phosphors.

26. The white LED claim 25, wherein the blue phosphor has the formula Sr_1-x-yMg_xBa_ySiO₄:

Eu₂₊F; and

where

0.5≦

x≦

1.0; and

0≦

y≦

0.5.

27. The white LED of claim 25, wherein the blue phosphor has the formula Sr_1-xMgEu_xAl₁₀O₁₇;

and where

0.01<

x≦

1.0.

28. The white LED of claim 25, wherein the blue phosphor has the formula Sr_xAl₁₄O₂₅:

Eu⁺², and where

x≦

4.

37. The white light illumination system of claim 15, wherein the ratio of the yellow phosphor to the blue phosphor ranges from about 9 to 0.2.

39. White light illumination produced by the white LED of claim 15.

42. The white light illumination according to claim 39, wherein the white light illumination comprises about 20 to 50 percent light emitted by the blue phosphor and about 50 to 80 percent light emitted by the yellow phosphor.

44. The white light illumination according to claim 15, wherein the white light illumination has a color temperature ranging from about 3000 to 6500 K.

47. The white light illumination according to claim 15, wherein the white light illumination has a color rendering index (CRI) greater than about 70.

29. A single phosphor system for a white LED, the phosphor system comprising:

a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;

a phosphor configured to absorb at least a portion of the radiation from the radiation source and emit a broad spectrum light with a peak intensity in a wavelength ranging from about 520 to 560 nm.

30. The white LED of claim 29, wherein the 250 to 400 nm portion of the ratiation emitted by the radiation source is substantially non-visible ultraviolet (UV) radiation, and the 400 to 420 nm portion is substantially purple light from the visible range of the electromagnetic spectrum.

31. The white LED of claim 29, wherein the radiation source comprises a light emitting diode (LED).

32. The white LED of claim 31, wherein the radiation source comprises at least one semiconductor layer selected from the group consisting of GaN, ZnSe, and SiC, and at least one active region comprising a p-n junction selected from the group consisting of GaN, AlGaN, InGaN, and InAlGaN.

33. The white LED of claim 29, wherein the single phosphor is selected from the group consisting of silicate-based phosphors.

34. The white LED of claim 29, wherein the single phosphor has the formula A₂SiO₄:

Eu⁺²F, wherein A is at least one of a divalent metal selected from the group consisting of Sr, Ca, Ba, Mg, Zn, and Cd.

35. The white LED of claim 29, wherein the single phosphor has the formula Sr_1-x-yBa_xCa_ySiO₄:

Eu⁺²F; and

where

0.3≦

x≦

0.8; and

0.1≦

y≦

0.5.

40. White light illumination produced by the single phosphor system of claim 29.

45. The white light illumination according to claim 29, wherein the white light illumination has a color temperature ranging from about 3000 to 6500 K.

48. The white light illumination according to claim 29, wherein the white light illumination has a color rendering index (CRI) greater than about 70.

49. A method of producing white light illumination from a two-phosphor system, the method comprising:

providing a radiation source configured to emit radiation having a wavelength ranging from about 250 to 420 nm;

exposing a yellow phosphor to at least a portion of the radiation from the radiation source to produce light having a wavelength ranging from about 530 to 590 nm;

exposing a blue phosphor to at least a portion of the radiation from the radiation source to produce light having a wavelength ranging from about 470 to 530 nm; and

mixing the light from the yellow phosphor with the light from the blue phosphor to produce the white illumination.

50. The white light illumination produced by the method of claim 49.

51. The white light illumination of claim 50, wherein the white light illumination comprises about 10 to 50 percent of the visible radiation from the blue region of the spectrum and about 50 to 90 percent of the visible radiation from the yellow region of the spectrum.

52. The white light illumination of claim 50, wherein the white light illumination has a color temperature ranging from about 3000 to 6500 K.

53. The white light illumination of claim 50, wherein the white light illumination has a color rendering index (CRI) greater than about 70.