Phosphor for down converting ultraviolet light of LEDs to blue-green light

• US 6,555,958 B1
• Filed: 05/15/2000
• Issued: 04/29/2003
• Est. Priority Date: 05/15/2000
• Status: Expired due to Term

• Current Assignee: Current Lighting Solutions, LLC (f/k/a GE Lighting Solutions, LLC) (American Industrial Partners)
• Original Assignee: General Electric Company
• Inventors: Doxsee, Dan Darcy, Srivastava, Alok Mani, Comanzo, Holly Ann, McNulty, Thomas Francis
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): Santiago, Mariceli
• Application Number:
  US09/571,382
• Time in Patent Office: 1,079 Days
• Field of Search: 252/301.4 F, 252/301.6 F, 252/301.4 R, 340/815.4, 340/815.45, 313/485, 313/486, 313/502, 257/89, 257/98, 257/102
• US Class Current: 313/506
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/12044 OLED
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: Y10S 502/503 Crush strength
• CPC Class Codes: Y10S 502/509 Nitrogen containing organic compound

Abstract

There is provided a blue-green illumination system, comprising a light emitting diode, and a luminescent material having emission CIE color coordinates located within an area of a of a pentagon on a CIE chromaticity diagram, whose corners have the following CIE color coordinates:

i) x=0.0137 and y=0.4831;

ii) x=0.2240 and y=0.3890;

iii) x=0.2800 and y=0.4500;

iv) x=0.2879 and y=0.5196; and

v) x=0.0108 and y=0.7220.

The light emitting diode may be a UV LED and the luminescent material may be a Ba₂SiO₄:Eu²⁺ phosphor, a Ba₂(Mg,Zn)Si₂O₇:Eu²⁺ phosphor and/or a Ba₂Al₂O₄:Eu²⁺ phosphor. The illumination system may be used as the green light of a traffic light or an automotive display.

Claims

1. A blue-green illumination system, comprising:

a light emitting diode; and

a luminescent material having emission CIE color coordinates located within an area of a pentagon on a CIE chromaticity diagram, whose corners have the following CIE color coordinates;

e) x=0.0137 and y=0.4831;

b) x=0.2240 and y=0.3890;

c) x=0.2800 and y=0.4500;

g) x=0.2879 and y=0.5196; and

h) x=0.0108 and y=0.7220.

2. The system of claim 1, wherein the light emitted by the system lacks any significant visible component emitted by the light emitting diode.

3. The system of claim 1, wherein the light emitting diode peak emission wavelength is between 360 and 420 nm.

4. The system of claim 1, wherein the luminescent material emission CIE color coordinates are x=0.1±

0.05 and y=0.52±

0.05.

5. The system of claim 4, wherein:

the light emitting diode peak emission wavelength is between 370 and 405 nm; and

the luminescent material emission CIE color coordinates are x=0.12 and y=0.49.

6. The system of claim 1, wherein the emission CIE color coordinates of the luminescent material are located within an area of a quadrilateral on a CIE chromaticity diagram, whose corners have the following CIE color coordinates:

a) x=0.000 and y=0.506;

b) x=0.224 and y=0.389;

c) x=0.280 and y=0.450; and

d) x=0.000 and y=0.730.

7. The system of claim 1, wherein the emission CIE color coordinates of the luminescent material are located within an area of a quadrilateral on a CIE chromaticity diagram, whose corners have the following CIE color coordinates:

e) x=0.0137 and y=0.4831;

f) x=0.2094 and y=0.3953;

g) x=0.2879 and y=0.5196; and

h) x=0.0108 and y=0.7220.

8. The system of claim 1, wherein:

the luminescent material comprises an A₂SiO₄;

Eu²⁺ phosphor; and

A comprises at least one of Ba, Ca, Sr or Mg.

9. The system of claim 8, wherein:

A comprises at least 80% Ba.

10. The system of claim 9, wherein:

the A₂SiO₄;

Eu²⁺ phosphor comprises an (A_1-xEu_x)₂SiO₄ phosphor; and

0<

x≦

0.2.

11. The system of claim 10, wherein A comprises barium.

12. The system of claim 1, wherein:

the luminescent material comprises an A₂DSi₂O₇;

Eu²⁺;

A comprises at least one of Ba, Ca or Sr; and

D comprises at least one of Mg or Zn.

13. The system of claim 12, wherein:

the ADSiO;

Eu²⁺ phosphor comprises a Ba₂MgSi₂O₇;

Eu²⁺ phosphor.

14. The system of claim 12, wherein:

the A₂DSi₂O₇;

Eu²⁺ phosphor comprises an (A_1-xEux)₂ DSi₂O₇ phosphor; and

0<

x≦

0.2.

15. The system of claim 14, wherein:

A comprises Ba; and

D comprises Mg.

16. The system of claim 1, wherein:

the luminescent material comprises an AAl₂O₄;

Eu²⁺ phosphor; and

A comprises at least one of Ba, Sr or Ca.

17. The system of claim 16, wherein:

A comprises at least 80% Ba.

18. The system of claim 17, wherein:

the AAl₂O₄;

Eu²⁺ phosphor comprises an (A_1-xEu_x) Al₂O₄ phosphor; and

0<

x≦

0.2.

19. The system of claim 16, wherein A comprises at least one of Ba or Sr.

20. The system of claim 1, wherein:

the light emitting diode peak emission wavelength is between 370 and 405 nm; and

the luminescent material comprises one or more of the following phosphors;

i) (A_1-xEu_x)₂SiO₄, where A comprises at least one of Ba, Sr, Ca or Mg; and

0<

x≦

0.2;

ii) (A_1-xEu_x)₂ DSi₂O₇, where A comprises at least one of Ba, Sr or Ca;

D comprises at least one of Mg or Zn; and

0<

x≦

0.2;

or

iii) (A_1-xEu_x) Al₂O₄, where A comprises at least one of Ba, Sr or Ca; and

0<

x≦

0.2.

21. The system of claim 20, wherein the luminescent material comprises two or three phosphors selected from i), ii) and iii).

22. The system of claim 20, further comprising:

a shell containing the light emitting diode;

an encapsulating material between the shell and the light emitting diode; and

wherein;

a) the phosphor is coated over a surface of the light emitting diode;

b) the phosphor is interspersed in the encapsulating material;

or

c) the phosphor is coated onto the shell.

23. The system of claim 22, further comprising:

a traffic signal housing containing the blue-green illumination system; and

a traffic light lens in front of the blue-green illumination system.

24. The system of claim 22, further comprising an automotive display containing the blue-green illumination system.

25. A traffic signal, comprising:

a housing;

at least one lens;

a radiation source having a peak emission wavelength of 420 nm and below; and

a luminescent material having emission CIE color coordinates located within an area of a quadrilateral on a CIE chromaticity diagram, whose corners have the following CIE color coordinates;

a) x=0.000 and y=0.506;

b) x=0.224 and y=0.389;

c) x=0.280 and y=0.45; and

d) x=0.000 and y=0.730.

26. The traffic signal of claim 25, wherein the radiation source comprises a light emitting diode or a fluorescent lamp.

27. The traffic signal of claim 26, wherein the luminescent material comprises one or more of the following phosphors having emission CIE color coordinates of x=0.1±

0.05 and y=0.52±

0.05;

i) (A_1-xEu_x)₂SiO₄, where A comprises at least one of Ba, Sr, Ca or Mg; and

0<

x≦

0.2;

ii) (A_1-xEu_x)₂ DSi₂O₇, where A comprises at least one of Ba, Sr or Ca;

D comprises at least one of Mg or Zn; and

0<

x≦

0.2;

or

iii) (A_1-xEu_x) Al₂O₄, where A comprises at least one of Ba, Sr or Ca; and

0<

x≦

0.2.

28. A method of making a blue-green light illumination system, comprising:

mixing a plurality of starting powders to form a starting powder mixture;

firing the starting powder mixture to form a calcined-body;

converting the calcined body into a phosphor powder having emission CIE color coordinates located within an area of a pentagon on a CIE chromaticity diagram, whose corners have the following CIE color coordinates;

e) x=0.0137 and y=0.4831;

b) x=0.2240 and y=0.3890;

c) x=0.2800 and y=0.4500;

g) x=0.2879 and y=0.5196; and

h) x=0.0108 and y=0.7220;

placing the phosphor powder into the illumination system; and

placing a light emitting diode into the illumination system.

29. The method of claim 28, wherein:

the light emitting diode peak emission wavelength is between 370 and 405 nm;

the phosphor powder emission CIE color coordinates are x=0.1±

0.05 and y=0.52±

0.05; and

the phosphor powder comprises at least one of;

i) (A_1-xEu_x)₂SiO₄, where A comprises at least one of Ba, Sr, Ca or Mg; and

0<

x≦

0.2;

ii) (A_1-x,Eu_x)₂ DSi₂O₇, where A comprises at least one of Ba, Sr or Ca;

D comprises at least one of Mg or Zn; and

0<

x≦

0.2;

or

iii) (A_1-x,Eu_x)Al₂O₄, where A comprises at least one of Ba, Sr or Ca; and

0<

x≦

0.2.

30. The method of claim 29, wherein the step of placing the phosphor powder into the illumination system comprises placing any two or three phosphor powders selected from i), ii) and iii) into the illumination system.

31. The method of claim 29, wherein:

the step of mixing comprises mixing a SiO₂*H₂O powder, a Eu₂O₃ powder, a BaCO₃ powder and a flux selected from at least one of BaF₂ or EuF₃ to form the starting powder mixture; and

the step of firing comprises firing the starting powder mixture in a charcoal atmosphere for 5-7 hours at 1200 to 1400°

C. and then in a reducing atmosphere at about 900 to 1200°

C. for 2-6 hours.

32. The method of claim 29, wherein:

the step of mixing comprises mixing a SiO₂*H₂O powder, a Eu₂O₃ powder a BaCO₃ powder and one of a MgCO₃ or a MgO powders to form the starting powder mixture; and

the step of firing comprises firing the starting powder mixture in a charcoal atmosphere for 5-7 hours at 900 to 1250°

C. and then in a reducing atmosphere at about 900 to 1200°

C. for 2-6 hours.

33. The method of claim 29, wherein:

the step of mixing comprises mixing at least one of an Al(OH)₃ powder and an Al₂O₃ powder, a Eu₂O₃ powder, and at least one of a SrCO₃ powder and a BaCO₃ powder to form the starting powder mixture; and

the step of firing comprises firing the starting powder mixture in a charcoal atmosphere for 5-7 hours at 1300 to 1500°

C. and then in a reducing atmosphere at about 900 to 1200°

C. for 2-6 hours.

34. The method of claim 29, further comprising:

placing the light emitting diode into a shell; and

filling the shell with an encapsulating material.

35. The method of claim 34, further comprising:

a) coating a suspension of the phosphor powder and a solvent over a surface of the light emitting diode and drying the suspension;

b) interspersing the phosphor powder in the encapsulating material;

or

c) coating a suspension of phosphor powder and a solvent onto the shell and drying the suspension.

36. The method of claim 28, wherein the emission CIE color coordinates of the phosphor are located within an area of a quadrilateral on a CIE chromaticity diagram, whose corners have the following CIE color coordinates:

a) x=0.000 and y=0.506;

b) x=0.224 and y=0.389;

c) x=0.280 and y=0.450; and

d) x=0.000 and y=0.730.

37. The method of claim 36, further comprising placing the illumination system into a traffic signal housing.

38. The method of claim 28, wherein the emission CIE color coordinates of the phosphor are located within an area of a quadrilateral on a CIE chromaticity diagram, whose corners have the following CIE color coordinates:

e) x=0.0137 and y=0.4831;

f) x=0.2094 and y=0.3953;

g) x=0.2879 and y=0.5196; and

h) x=0.0108 and y=0.7220.

39. The method of claim 36, further comprising placing the illumination system into an automotive display.