LAMINATED THICK FILM DIELECTRIC STRUCTURE FOR THICK FILM DIELECTRIC ELECTROLUMINESCENT DISPLAYS

• US 20080315762A1
• Filed: 04/25/2008
• Published: 12/25/2008
• Est. Priority Date: 04/30/2007
• Status: Active Grant

• Current Assignee: iFire IP Corporation, Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: iFire IP Corporation, Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Hamada, Hiroki, Yoshida, Isao, Stiles, James Alexander Robert, Peter, Manuela, Pugliese, Vincent Joseph Alfred
• Granted Patent: US 7,915,803 B2
• Time in Patent Office: Days
• US Class Current: 313/509
• CPC Class Codes: H01B 3/004 with conductive additives or conductive layers
• CPC Class Codes: H01B 3/10 metallic oxides ceramics H01B3/12
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A novel and improved composite thick film dielectric structure is provided to improve the operating stability of phosphors used in thick dielectric ac electroluminescent displays. The novel structure comprises one or more aluminum oxide layers disposed between the composite thick dielectric layer and the bottom of the phosphor layer of these displays.

Claims

1. An improved composite thick film dielectric structure, said structure comprising;

a composite thick film dielectric layer;

one or more layers of a material provided on the top surface of said composite thick film dielectric layer, said material sufficiently thick to act as a barrier to deleterious ions and also be minimally electrically conductive;

a thin film phosphor layer;

wherein at least of one said one or more layers of said material is not in direct contact with said phosphor layer.

2. The improved structure of claim 1, said structure further comprising one or more thin film dielectric layers of a non lead-containing composition on top of said one or more layers of material.

3. The improved structure of claim 2, wherein said one or more layers of said material are provided on and/or in between said one or more thin film dielectric layers.

4. The improved structure of claim 3, wherein said one or more thin film dielectric layers are selected from barium titanate and barium tantalate.

5. The improved structure of claim 1, wherein said material is aluminum oxide.

6. The improved structure of claim 5, wherein said structure comprises in sequence a composite thick film dielectric layer, a layer of aluminum oxide, a layer of barium titanate and a thin film phosphor layer.

7. The improved structure of claim 5, wherein said structure comprises in sequence a composite thick film dielectric layer, a layer of aluminum oxide, a layer of barium titanate, a layer of barium tantalate and a thin film phosphor layer.

8. The improved structure of claim 5, wherein said structure comprises in sequence a composite thick film dielectric layer, a layer of aluminum oxide, a layer of barium titanate, a layer of barium tantalate, a layer of aluminum oxide and a thin film phosphor layer.

9. The improved structure of claim 5, wherein said structure comprises in sequence a composite thick film dielectric layer, a layer of aluminum oxide, a layer of barium titanate, a layer of aluminum oxide, a layer of barium tantalate, a layer of aluminum oxide and a thin film phosphor layer.

10. The improved structure of claim 5, wherein said structure comprises in sequence a composite thick film dielectric layer, a layer of aluminum oxide, a layer of barium titanate, a layer of aluminum oxide, a layer of barium tantalate and a thin film phosphor layer.

11. The improved structure of claim 5, wherein said aluminum oxide layer has a thickness of about 25 to about 50 nm.

12. The improved structure of claim 5, wherein said aluminum oxide layer has a thickness of up to about 50 nm.

13. The improved structure of claim 12, wherein said aluminum oxide layer has a thickness of up to about 25 nm.

14. The improved structure of claim 13, wherein said phosphor layer is a thioaluminate.

15. The improved structure of claim 14, wherein said phosphor layer is represented by AB_xC_y:

RE, where

A is one or more of Mg, Ca, Sr or Ba

B is at least one of Al or In;

C is at least one of S or Se;

RE is a rare earth species;

x is between 2-4 and y is between 4-7.

16. The improved structure of claim 15, wherein said rare earth species is selected from Eu and Ce.

17. The improved structure of claim 16, wherein said phosphor is BaAl₂S₄ activated with europium.

18. The improved structure of claim 1, wherein said structure further comprises a layer of aluminum nitride on said phosphor layer.

19. The improved structure of claim 18, wherein said structure further comprises an ITO transparent layer on said aluminum nitride layer.

20. An electroluminescent display comprising a thick film dielectric structure, said structure comprising:

(a) a composite thick film dielectric layer;

(b) a layer of aluminum oxide provided on top adjacent to said composite thick film dielectric structure;

(c) a layer of barium titanate on top of (b);

(d) an optional layer of barium tantalate on top of (c); and

(e) optionally a further layer of aluminum oxide provided on top of (c) and/or on top of (d).

21. The display of claim 20, wherein said aluminum oxide layer has a thickness of about 25 to about 50 nm.

22. The display of claim 20, wherein said aluminum oxide has a thickness of up to about 50 nm.

23. The display of claim 20, wherein said display comprises a thioaluminate phosphor layer.

24. The display of claim 23, wherein said phosphor layer is represented by AB_xC_y:

RE, where

A is one or more of Mg, Ca, Sr or Ba

B is at least one of Al or In;

C is at least one of S or Se;

RE is Eu or Ce;

x is between 2-4 and y is between 4-7.

25. The display of claim 24, wherein said phosphor is BaAl₂S₄ activated with europium.

26. The display of claim 23, wherein said structure further comprises a layer of aluminum nitride on said phosphor layer.

27. The display of claim 26, wherein said structure further comprises an ITO transparent layer on said aluminum nitride layer.

28. The display of claim 20, wherein said display comprises a substrate with a metal electrode layer beneath said composite thick film dielectric layer.

29. An ac electroluminescent display comprising a composite thick film dielectric layer and a rare earth activated alkaline-earth phosphor deposited over the composite thick film dielectric layer, wherein at least one vacuum-deposited aluminum oxide layer is provided directly a top surface of the composite thick film dielectric layer and further wherein said composite thick film dielectric layer is formed on a substrate with a formed electrode pattern by the sequential steps of:

depositing a high constant dielectric layer by printing a paste containing dielectric powder and then sintering the printed layer and depositing a smoothing layer formed using a metal organic deposition (MOD) method over the printed and sintered layer thereby forming a composite thick film dielectric layer;

vacuum depositing an aluminum oxide layer on said composite thick film dielectric layer; and

depositing at least one lead-free high dielectric constant layer over the aluminum oxide layer using a sputtering or MOD method.

30. The ac electroluminescent display of claim 29, wherein a second vacuum deposited aluminum oxide layer is deposited over the lead-free high dielectric constant layer of said dielectric structure and a second lead-free high dielectric constant layer is deposited over the second vacuum deposited aluminum oxide layer.

31. The ac electroluminescent display of claim 29, wherein the lead-free high dielectric constant material comprises barium titanate.

32. The ac electroluminescent display of claim 29, wherein the second lead-free high dielectric constant layer comprises barium tantalate.

33. The ac electroluminescent display of claim 29, wherein an additional aluminum oxide layer is vacuum deposited over the high dielectric layers prior to deposition of the phosphor film.

34. The ac electroluminescent display of claim 29, wherein the lead free high dielectric constant layers are deposited using a sputtering method.

35. The ac electroluminescent display of claim 32, wherein the lead free high dielectric constant layer is deposited using a MOD method.

36. The ac electroluminescent display of claim 29, wherein said aluminum oxide layer has a thickness of about 25 to about 50 nm.

37. The ac electroluminescent display of claim 29, wherein said aluminum oxide layer has a thickness of up to about 50 nm.