Aluminum oxide and aluminum oxynitride layers for use with phosphors for electroluminescent displays

• US 20060017381A1
• Filed: 07/19/2005
• Published: 01/26/2006
• Est. Priority Date: 07/22/2004
• Status: Active Grant

• Current Assignee: iFire IP Corporation, Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: iFire IP Corporation
• Inventors: Acchione, Joe, Xin, Yongbao, Yoshida, Isao, Hamada, Hiroki
• Granted Patent: US 7,812,522 B2
• Time in Patent Office: Days
• US Class Current: 313/509
• CPC Class Codes: C09K 11/7718 with alkaline earth metals
• CPC Class Codes: C09K 11/7731 with alkaline earth metals
• CPC Class Codes: C09K 11/7734 Aluminates
• CPC Class Codes: C09K 11/7786 with alkaline earth metals
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers

Abstract

A novel laminate is provided to improve the operating stability of thioaluminate based phosphors used in ac thick film dielectric electroluminescent displays. The novel structure comprises a rare earth activated alkaline earth thioaluminate phosphor thin film layer and an aluminum oxide or aluminum oxynitride layer provided directly adjacent and in contact with the bottom of the phosphor thin film layer. The invention is particularly applicable to phosphors used in electroluminescent displays that employ thick dielectric layers subject to high processing temperatures to form and activate the phosphor films.

Claims

1. A phosphor laminate for a thick dielectric film electroluminescent device, said laminate comprising:

,

a rare earth activated alkaline earth thioaluminate phosphor thin film layer;

an aluminum oxide or aluminum oxynitride layer provided directly adjacent and in contact with a bottom of said phosphor thin film layer; and

a thick film dielectric layer adjacent said aluminum oxide or aluminum oxynitride layer

2. The laminate of claim 1, wherein said phosphor thin film layer is represented by AB_xC_y:

RE wherein

A is at least one of Mg, Ca, Sr or Ba;

B is at least one of Al or In;

C is least one of S or Se; and

2≦

x≦

4 and 4≦

y≦

7.

3. The laminate of claim 2, wherein RE is one or more rare earth activator species selected from the group consisting of Eu and Ce.

4. The laminate of claim 3, wherein said phosphor is barium thioaluminate with a ratio of aluminum to barium between about 2 to about 2.5.

5. The laminate of claim 3, wherein said phosphor is magnesium barium thioaluminate with a ratio of the atomic concentration of magnesium to barium plus magnesium is in the range of about 0.001 to 0.2.

6. The laminate of claim 3, wherein the phosphor is activated with trivalent europium or cerium and the atomic ratio of europium or cerium to barium or barium plus magnesium is in the range of about 0.005 to about 0.094.

7. The laminate of claim 3, wherein the phosphor is activated with trivalent europium or cerium and the atomic ratio of europium or cerium to barium or barium plus magnesium is in the range of about 0.015 to 0.035.

8. The laminate of claim 3, wherein said phosphor additionally comprise oxygen at a relative atomic concentration that is less than 0.2 of the combined S and Se concentrations.

9. The laminate of claim 1, wherein said aluminum oxide or aluminum oxynitride layer has a thickness of about 20 nm to about 50 nm.

10. The laminate of claim 1, wherein said aluminum oxide or aluminum oxynitride layer is adhered to the phosphor thin film structure.

11. The laminate of claim 1, wherein said aluminum oxide or aluminum oxynitride layer is deposited by a vacuum deposition process.

12. The laminate of claim 11, wherein said vacuum deposition process is sputtering.

13. The laminate of claim 12, wherein sputtering is conducted in a low pressure nitrogen atmosphere where the ratio of argon to nitrogen is within the range of about 4:

1 to 1;

1 and the working pressure is maintained within the range of about 8×

10<sup>−

4</sup> mbar to 6×

10<sup>−

3</sup> mbar.

14. The laminate of claim 12, wherein sputtering is conducted in a low pressure oxygen-containing atmosphere.

15. The laminate of claim 12, wherein sputtering is conducted in a low pressure oxygen and nitrogen-containing atmosphere.

16. The laminate of claim 1, wherein said thick film dielectric layer comprises a bottom, layer of lead magnesium niobate (PMN) or lead magnesium niobate titanate (PMN-PT) and a top layer of lead zirconate titanate (PZT) as a smoothing layer.

17. The laminate of claim 16, wherein a layer of barium titanate is provided on top of said smoothing layer.

18. The laminate of claim 17, wherein a further layer of barium tantalate is provided on said barium titanate layer, said barium tantalate being directly adjacent to said aluminum oxide or aluminum oxynitride layer.

19. The laminate of claim 17, wherein said layer of barium titanate has a thickness of about 100 nm to about 200 nm.

20. The laminate of claim 18, wherein said layer of barium tantalate has a thickness of about 30 nm to about 70 nm.

41. A method for improving the luminance and operating life of a alkaline earth thioaluminate phosphor doped with a rare earth activator species in a thick film dielectric electroluminescent device, the method comprising:

providing the laminate of claim 1 within said device.

21. A thick film dielectric electroluminescent device comprising:

a thioaluminate phosphor;

a layer of aluminum oxide or aluminum oxynitride directly adjacent a bottom surface of the phosphor; and

a thick film dielectric layer adjacent said layer of aluminum oxide or aluminum oxynitride.

22. The device of claim 21, wherein said phosphor is represented by AB_xC_y:

RE wherein

A is at least one of Mg, Ca, Sr or Ba;

B is at least one of Al or In;

C is least one of S or Se; and

2≦

x≦

4 and 4≦

y≦

7.

23. The device of claim 22, wherein RE is one or more rare earth activator species selected from the group consisting of Eu and Ce.

24. The device of claim 23, wherein said phosphor is barium thioaluminate with a ratio of aluminum to barium between about 2 to about 2.5.

25. The device of claim 23, wherein said phosphor is magnesium barium thioaluminate with a ratio of the atomic concentration of magnesium to barium plus magnesium is in the range of about 0.001 to 0.2.

26. The device of claim 23, wherein the phosphor is activated with trivalent europium or cerium and the atomic ratio of europium or cerium to barium or barium plus magnesium is in the range of about 0.005 to about 0.094.

27. The device of claim 23, wherein the phosphor is activated with trivalent europium or cerium and the atomic ratio of europium or cerium to barium or barium plus magnesium is in the range of about 0.015 to 0.035.

28. The device of claim 23, wherein said phosphor additionally comprise oxygen at a relative atomic concentration that is less than 0.2 of the combined S and Se concentrations.

29. The device of claim 21, wherein said layer of aluminum oxide or aluminum oxynitride has a thickness of about 20 nm to about 50 nm.

30. The device of claim 21, wherein said layer of aluminum oxide or aluminum oxynitride is adhered to the phosphor.

31. The device of claim 21, wherein said layer of aluminum oxide or aluminum oxynitride is deposited by a vacuum deposition process.

32. The device of claim 31, wherein said vacuum deposition process is sputtering.

33. The device of claim 32, wherein sputtering is conducted in a low pressure nitrogen atmosphere where the ratio of argon to nitrogen is within the range of about 4:

1 to 1;

1 and the working pressure is maintained within the range of about 8×

10<sup>−

4</sup> mbar to 6×

10<sup>−

3</sup> mbar.

34. The device of claim 32, wherein sputtering is conducted in a low pressure oxygen-containing atmosphere.

35. The device of claim 32, wherein sputtering is conducted in a low pressure oxygen and nitrogen-containing atmosphere.

36. The device of claim 21, wherein said thick film dielectric layer comprises a bottom layer of lead magnesium niobate (PMN) or lead magnesium niobate titanate (PMN-PT) and a top layer of lead zirconate titanate (PZT) as a smoothing layer.

37. The device of claim 36, wherein a layer of barium titanate is provided on top of said smoothing layer.

38. The device of claim 37, wherein a further layer of barium tantalate is provided on said barium titanate layer, said barium tantalate being directly adjacent to said layer of aluminum oxide or aluminum oxynitride.

39. The device of claim 37, wherein said layer of barium titanate has a thickness of about 100 nm to about 200 nm.

40. The device of claim 38, wherein said layer of barium tantalate has a thickness of about 30 nm to about 70 nm.