Thin film electroluminescence device

• US 4,975,338 A
• Filed: 04/12/1989
• Issued: 12/04/1990
• Est. Priority Date: 04/12/1988
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Ohseto, Seiichi, Deguchi, Hiroshi, Kameyama, Kenji, Kageyama, Yoshiyuki
• Primary Examiner(s): SEIDLECK, JAMES J
• Application Number:
  US07/337,160
• Time in Patent Office: 601 Days
• Field of Search: 428/690, 428/691, 313/503, 313/509
• US Class Current: 428/690
• CPC Class Codes: H05B 33/145 Arrangements of the electroluminescent material
• CPC Class Codes: H05B 33/18 characterised by the nature or concentration of the activator
• 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: H05B 33/26 characterised by the composition or arrangement of the conductive material used as an electrode
• CPC Class Codes: H05B 33/28 of translucent electrodes

Abstract

A thin film EL device is disclosed which comprises (a) a substrate, (b) a transparent electrode layer formed on the substrate, (c) one or more insulating layers formed on the transparent electrode layer, with at least one of the insulating layers comprising a crystalline nitride, (d) an electroluminescent emitting layer comprising a luminescent host material consisting of an alkali earth calcogen compound formed on the insulating layers, and (e) a back electrode layer. In the above thin film EL device, it is preferable that the insulating layer in contact with the electroluminescent layer comprise a crystalline aluminum nitride or boron nitride, and that the transparent electrode layer comprise a host material consisting of a C-axis oriented zinc oxide.

Claims

1. A thin film electroluminescence device comprising:

a substrate,

a transparent electrode layer formed on said substrate,

an insulating layer consisting of one or more constituent layers formed on said transparent electrode layer, at least one of said constituent insulating layers comprising a crystalline aluminum nitride or boron nitride wherein the crystallinity of said crystalline nitride is 1 or more when indicated by a reciprocal number of the half width of the X-ray diffraction pattern,

an electroluminescence emitting layer comprising an electroluminescence host material and an activator, formed on said constituent insulating layer comprising a crystalline nitride, said electroluminescence host material being an alkali earth chalcogen compound, and said activator being a rare earth element, and

a transparent back electrode layer formed on said electroluminescence layer.

2. The thin film electroluminescence device as claimed in claim 1, further comprising a second insulating layer comprising one or more constituent layers between said electroluminescence emitting layer and said transparent back electrode layer, at least one of said constituent insulating layers comprising a crystalline nitride and being in contact with said electroluminescence emitting layer.

3. The thin film electroluminescence device as claimed in claim 2, wherein the thickness of said second insulating layer is in the range of from 1,000 Å

to 2 μ

m.

4. The thin film electroluminescence device as claimed in claim 2, wherein said constituent insulating layer other than said constituent layer comprising a crystalline nitride comprises a dielectric compound selected from the group consisting of SiO₂, Al₂ O₃, Ta₂ O₅, SrTiO₃ and PbTiO₃.

5. The thin film electroluminescence device as claimed in claim 4, wherein the thickness of said constituent layer comprising said dielectric compound is in the range of from 500 Å

to 3,000 Å

.

6. The thin film electroluminescence device as claimed in claim 1, wherein said transparent back electrode layer comprises a C-axis oriented zinc oxide as a host material.

7. The thin film electroluminescence device as claimed in claim 1, wherein said crystalline nitride is a crystalline aluminum nitride.

8. The thin film electroluminescence device as claimed in claim 1, wherein said crystalline nitride is a crystalline boron nitride.

9. The thin film electroluminescence device as claimed in claim 1, wherein said alkali earth chalcogen compound is an alkali earth metal sulfide selected from the group consisting of SrS, CaS and BaS.

10. The thin film electroluminescence device as claimed in claim 1, wherein said alkali earth chalcogen compound is an alkali earth metal selenide selected from the group consisting of SrSe, CaSe and BaSe.

11. The thin film electroluminescence device as claimed in claim 1, wherein said rare earth element is selected from the group consisting of Ce, Pr, Sm, Eu, Tb and Tm.

12. The thin film electroluminescence device as claimed in claim 1, wherein said substrate is made of a material selected from the group consisting of soda-lime glass, borosilicate glass, aluminosilicate glass and quartz glass.

13. The thin film electroluminescence device as claimed in claim 1, wherein said transparent electrode layer is made of a material selected from the group consisting of Al, ITO, Sb-doped SnO₂, Al-doped ZnO, and Si-doped ZnO.

14. The thin film electroluminescence device as claimed in claim 11, wherein said Al-doped ZnO and said Si-doped ZnO are of a C-axis oriented crystalline type.

15. The thin film electroluminescence device as claimed in claim 1, wherein the thickness of said transparent electrode layer is in the range of from 1,000 Å

to 5,000 Å

.

16. The thin film electroluminescence device as claimed in claim 1, wherein the thickness of said insulating layer is in the range of from 1,000 Å

to 2 μ

m.

17. The thin film electroluminescence device as claimed in claim 1, wherein said constituent insulating layer other than said constituent layer comprising a crystalline nitride comprises a dielectric compound selected from the group consisting of SiO₂, Al₂ O₃, Ta₂ O₅, SrTiO₃ and PbTiO₃.

18. The thin film electroluminescence device as claimed in claim 17, wherein the thickness of said constituent layer comprising said dielectric compound is in the range of from 500 Å

to 3,000 Å

.

19. The thin film electroluminescence device as claimed in claim 1, wherein the thickness of said electroluminescence emitting layer is in the range of from 5,000 Å

to 15,000 Å

.

20. The thin film electroluminescence device as claimed in claim 1, wherein said back electrode layer is made of a material selected from the group consisting of Al, ITO, Sb-doped SnO₂, Al-doped ZnO and Si-deoped ZnO.

21. The thin film electroluminescence device as claimed in claim 1, wherein the thickness of said back electrode layer is in the range of from 1,000 Å

to 10,000 Å

.