EL element using polythiophene

• US 5,540,999 A
• Filed: 09/09/1994
• Issued: 07/30/1996
• Est. Priority Date: 09/09/1993
• Status: Expired due to Term

• Current Assignee: Futaba Corporation
• Original Assignee: Takakazu Yamamoto, TDK Corporation
• Inventors: Yamamoto, Takakazu, Kanbara, Takaki, Inoue, Tetsushi, Nakaya, Kenji
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): YAMNITZKY, MARIE ROSE
• Application Number:
  US08/303,736
• Time in Patent Office: 690 Days
• Field of Search: 428/690, 428/917, 428/704, 428/212, 428/411.1, 428/457, 313/503, 313/504, 313/506, 252/301.32, 252/301.35
• US Class Current: 428/411.1
• CPC Class Codes: C08G 61/126 with a five-membered ring containing one sulfur atom in the ring
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• 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: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 85/113 Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: Y10S 428/917 Electroluminescent
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/31504 Composite [nonstructural laminate]
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

An electroluminescent element includes an organic compound layer formed of a thiophene polymer as a light emitting layer or a hole injection transport layer. The element emits light at high luminance and is reliable.

Claims

1. An electroluminescent element comprising at least one layer comprising at least one member selected from a thiophene polymer comprising a structural unit of the following formula (1):

##STR6## wherein each of R₁ and R₂, which may be identical or different, is a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, and a thiophene copolymer comprising a structural unit of formula (1) and a structural unit of the following formula (2);

##STR7## wherein each of R₃ and R₄, which may be identical or different, is a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, or R₃ and R₄ taken together may form a benzene ring,

the polymer and the copolymer having an average degree of polymerization of 4 to 100 and being terminated with a hydrogen or halogen atom, and

said at least one layer is formed by vacuum evaporation of said thiophene polymer or copolymer.

2. The electroluminescent element of claim 1 wherein said at least one layer is a light emitting layer.

3. The electroluminescent element of claim 2 wherein said light emitting layer also serves as a hole injection transport layer.

4. The electroluminescent element of claim 1 which comprises a hole injection transport layer and a light emitting layer, said hole injection transport layer comprising the thiophene polymer or copolymer.

5. The electroluminescent element of claim 4 which comprises an anode, a first hole injection transport layer, a second hole injection transport layer, a light emitting layer and a cathode in this order, and the first hole injection transport layer comprises the thiophene polymer or copolymer.

6. An electroluminescent element as claimed in claim 5,

wherein said light emitting layer comprises at least one thiophene polymer of the following formula (3):

##STR8## wherein each of R₃ and R₄, which may be identical or different, is a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, or R₃ and R₄ taken together may form a benzene ring,

each of X₁ and X₂, which may be identical or different, is a hydrogen or halogen atom,

letter n is a number from 4 to 100, and

said light emitting layer comprising at least one thiophene polymer is formed by vacuum evaporation of polymer.

7. The electroluminescent element of claim 6 wherein said light emitting layer also serves as a hole injection transport layer.

8. The electroluminescent element of claim 4 which further comprises an electron injection transport layer.

11. The electroluminescent element of any one of claims 4, 5 or 9 which comprises at least one layer containing an electron injection transport compound,

the difference in ionization potential Ip or the difference in electron affinity Ea between the thiophene polymer or copolymer and said electron injection transport compound being at least 0.2 eV.

12. The electroluminescent element of claim 11 wherein the thiophene polymer or copolymer has an ionization potential IP of up to 5.4 eV in absolute value.

13. The electroluminescent element of claim 11 wherein said electron injection transport compound is tris(8-quinolinolato)aluminum.

14. The electroluminescent element of claim 1 or 9 which further comprises at least one mix layer containing a mixture of a hole injection transport compound and an electron injection transport compound.

15. The electroluminescent element of claim 14 wherein said mix layer is a light emitting layer.

16. The electroluminescent element of claim 14 wherein the difference in ionization potential IP or the difference in electron affinity Ea between said hole injection transport compound and said electron injection transport compound in said mix layer is at least 0.2 eV.

17. The electroluminescent element of claim 1 or 9 which further comprises a layer doped with a fluorescent material.

18. The electroluminescent element of claim 17 wherein said fluorescent material is rubrene.

9. An electroluminescent element comprising an anode, a first hole injection transport layer, a second hole injection transport layer, a light emitting layer and a cathode in this order,

said first hole injection transport layer comprising at least one thiophene polymer of the following formula (3):

##STR9## wherein each of R₃ and R₄, which may be identical or different, is a hydrogen atom, an aromatic hydrocarbon group or an aliphatic hydrocarbon group, or R₃ and R₄ taken together may form a benzene ring,

each of X₁ and X₂, which may be identical or different, is a hydrogen or halogen atom,

letter n is a number from 4 to 100, and

said layer comprising at least one thiophene polymer is formed by vacuum evaporation of said polymer.

10. The electroluminescent element of claim 9 which further comprises an electron injection transport layer.