ELECTROLUMINESCENT DEVICE HAVING IMPROVED LIGHT OUTPUT

• US 20070257608A1
• Filed: 05/05/2006
• Published: 11/08/2007
• Est. Priority Date: 05/05/2006
• Status: Active Grant

• Current Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Original Assignee: Eastman Kodak Company
• Inventors: Tyan, Yuan-Sheng, Farruggia, Giuseppe, Wang, Jin-Shan, Cushman, Thomas, Kesel, Raymond
• Granted Patent: US 7,851,995 B2
• Time in Patent Office: Days
• US Class Current: 313/506
• CPC Class Codes: C03C 17/38 at least one coating being a coating of an organic material
• CPC Class Codes: C03C 2217/48 having a specific function
• CPC Class Codes: C03C 2217/944 Layers comprising zinc oxide
• CPC Class Codes: C03C 2217/948 Layers comprising indium tin oxide [ITO]
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 59/877 comprising scattering means

Abstract

An electroluminescent device including a transparent substrate, a securing layer, a light scattering layer, an electroluminescent unit including a transparent electrode layer, a light emitting element including at least one light emitting layer, and a reflecting electrode layer in that order, wherein the light scattering layer includes one monolayer of inorganic particles having an index of refraction larger than that of the light emitting layer and wherein the securing layer holds the inorganic particles in the light scattering layer.

Claims

1. An electroluminescent device comprising a transparent substrate, a securing layer, a light scattering layer, an electroluminescent unit including a transparent electrode layer, a light emitting element including at least one light emitting layer, and a reflecting electrode layer in that order, wherein the light scattering layer includes one monolayer of inorganic particles having an index of refraction larger than that of the light emitting layer and wherein the securing layer holds the inorganic particles in the light scattering layer.

2. The electroluminescent device of claim 1 further including a surface smoothing layer between the light scattering layer and the transparent electrode layer.

3. The electroluminescent device of claim 1 further including a short reduction layer disposed in the electroluminescent unit between the transparent electrode layer and the light emitting element.

4. The electroluminescent device of claim 2 further including a short reduction layer disposed in the electroluminescent unit between the transparent electrode layer and the light emitting element.

5. The electroluminescent device of claim 1 wherein the securing layer includes a photo-polymerizable material, a heat-polymerizable material, an epoxy, or an adhesive.

6. The electroluminescent device of claim 4 wherein the securing layer includes a photo-polymerizable material, a heat-polymerizable material, an epoxy, or an adhesive.

7. The electroluminescent device of claim 1 wherein the inorganic particles in the light scattering layer includes titanium oxide, tantalum oxide, niobium oxide, zirconium oxide, aluminum oxide, tungsten oxide, antimony oxide, vanadium oxide, molybdenum oxide, or mixtures thereof.

8. The electroluminescent device of claim 4 wherein the inorganic particles in the light scattering layer includes titanium oxide, tantalum oxide, niobium oxide, zirconium oxide, aluminum oxide, tungsten oxide, antimony oxide, vanadium oxide, molybdenum oxide, or mixtures thereof.

9. The electroluminescent device of claim 1 wherein the size of the inorganic particles is between 0.1 μ

m and 10 μ

m.

10. The electroluminescent device of claim 4 wherein the size of the inorganic particles is between 0.1 μ

m and 10 μ

m.

11. The electroluminescent device of claim 1 wherein the light scattering layer further contains a binder material.

12. The electroluminescent device of claim 4 wherein the light scattering layer further contains a binder material.

13. The electroluminescent device of claim 11 wherein the binder material is polyurethane.

14. The electroluminescent device of claim 12 wherein the binder material is polyurethane.

15. The electroluminescent device of claim 2 wherein the refractive index of the surface smoothing layer is higher than that of the light emitting layer.

16. The electroluminescent device of claim 4 wherein the refractive index of the surface smoothing layer is higher than that of the light emitting layer.

17. The electroluminescent device of claim 2 wherein the surface smoothing layer includes nanoparticles of high index metal oxide materials dispersed in a polymer matrix.

18. The electroluminescent device of claim 17 wherein the nanoparticles include titanium oxide, tantalum oxide, niobium oxide, zirconium oxide, aluminum oxide, tungsten oxide, antimony oxide, vanadium oxide, molybdenum oxide, or mixtures thereof.

19. The electroluminescent device of claim 17 wherein the polymer matrix material includes polyvinylpyrrolidone.

20. The electroluminescent device of claim 2 wherein the surface smoothing layer includes polyvinylcarbazole.

21. The electroluminescent device of claim 2 wherein the thickness of the surface smoothing layer is less than 0.5 μ

m.

22. The electroluminescent device of claim 1 wherein the securing layer is an UV-curable polymer including polyurethanes, epoxies, polyesters, acrylates, or acrylics, or pressure sensitive adhesives.

23. The electroluminescent device of claim 1 wherein the securing layer is an acrylate based UV-curable polymer that further contains silane.

24. The electroluminescent device of claim 1 wherein the securing layer has an index of refraction equal to or less than that of the substrate.

25. The electroluminescent device of claim 3 wherein the short reduction layer has a thickness between 10 nm and 200 nm.

26. The electroluminescent device of claim 3 wherein the short reduction layer has a sheet resistivity between 1×

10⁶ ohms/square to about 1×

10¹² ohms/square.

27. The electroluminescent device of claim 3 wherein the material for the short reduction layer includes molybdenum oxide, vanadium oxide, antimony oxide, bismuth oxide rhenium oxide, tantalum oxide, tungsten oxide, niobium oxide, nickel oxide, or mixtures thereof.

28. The electroluminescent device of claim 3 wherein the material for the short reduction layer includes a mixture of a conductive oxide including indium oxide, gallium oxide, zinc oxide, tin oxide, aluminum doped zinc oxide, and mixtures thereof and an insulating material selected from oxides, fluorides, nitrides, sulfides and mixtures thereof.

29. The electroluminescent device of claim 3 wherein the material for the short reduction layer includes a mixture of indium-tin oxide and zinc sulfide or of indium-tin oxide and zinc sulfide-silicon oxide mixture.

30. The electroluminescent device of claim 3 wherein the material for the short reduction layer includes organic materials including PEDOT/PSS, polythiophene, or polyaniline.

31. The electroluminescent device of claim 1 wherein the electroluminescent unit is a stacked OLED device.

32. A method for providing the electroluminescent device of claim 1 includes:

(a) providing a carrier having at least one smooth surface;

(b) disposing a scattering layer comprising a monolayer of scattering particles over the smooth surface of the carrier;

(c) providing a substrate in relative position to the carrier and dispensing a quantity of the securing material between the substrate and the carrier;

(d) engaging the substrate and the securing material to form the securing material into a layer between the substrate and the scattering layer;

(e) separating the substrate with the attached securing layer and the scattering layer from the carrier; and

(f) forming the electroluminescent unit on the light scattering layer.

33. The method of claim 32 wherein the securing material is polymer precursor and further including the step of polymerizing the polymer precursor before step e.

34. The method of claim 32 wherein the securing material is a liquid.

35. The method of claim 32 wherein the securing material is pliable and is deposited on the light scattering layer and the process of engaging the substrate with the pliable securing material spreads the securing material across the surface of the light scattering layer.

36. The method of claim 32 further including providing a surface smoothing layer over the scattering layer.

37. The method of claim 32 further including providing a short reduction layer.

38. The method of claim 32 wherein the carrier is a rigid plate of glass or plastic.

39. The method of claim 32 wherein the carrier is a flexible sheet.

40. The method of claim 32 further including proving the carrier in a roll form and cutting the carrier into sheets after any of the process steps.

41. The electroluminescent device of claim 1 wherein the material for the reflecting electrode layer is selected from Ag, Au, Al, or alloys thereof.

42. The methods of claim 32 further including applying a release agent is to the surface of the carrier plate prior to the application of the scattering layer.