Organic EL element

Details Organic EL element Organic EL element

1996-05-16

2001-03-20

Yamnitzky, Marie (Department: 1774)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S917000, C313S502000, C313S504000, C313S506000

Reexamination Certificate

active

06203933

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an organic electroluminescent (EL) element.
2. Background Art
Doping is one technique for producing light emission of any desired color from EL elements. It was reported in Jpn. J. Appl. Phys., 10, 527 (1971) to change emission color from blue to green by doping anthracene crystals with a minor amount of tetracene. With respect to organic thin film EL elements having a multilayer structure, it was reported in JP-A 264692/1988 to incorporate in a host material having a light emitting function a minor amount of a fluorescent dye capable of emitting light different from that of the host material in response to light emission from the host material as a dopant to form a light emitting layer, thereby changing the color of light emission from green to orange or red.
With respect to long wavelength light emission of yellow to red, known light emitting materials or dopant materials include laser dyes capable of red oscillation (EP 0281381), compounds capable of exciplex emission (JP-A 255788/1990), perylene compounds (JP-A 791/1991), coumarin compounds (JP-A 792/1991), dicyanomethylene compounds (JP-A 162481/1991), thioxanthene compounds (JP-A 177486/1991), mixtures of a conjugated polymer and an electron transporting compound (JP-A 73374/1994), squalirium compounds (JP-A 93257/1994), oxadiazole compounds (JP-A 136359/1994), oxynate derivatives (JP-A 145146/1994), and pyrene compounds (JP-A 240246/1994).
Other light emitting materials disclosed heretofore include condensed polycyclic aromatic compounds (JP-A 32966/1993 and 214334/1993). Also dopant materials proposed heretofore include various condensed polycyclic aromatic compounds (JP-A 258859/1993).
These light emitting systems, however, do not provide high luminance or stable light emitting performance. A further improvement in luminance or durability is thus desired.
DISCLOSURE OF THE INVENTION
A primary object of the invention is to provide an organic EL element which produces light emission of satisfactory luminance, especially at long wavelength and is durable in that improved light emitting performance lasts for a long time.
This and other objects of the invention are attained by the construction defined below as (1) to (13).
(1) An organic EL element comprising at least one organic compound layer containing a compound of the following general formula (I):
(Ar)
m
-L  (I)
wherein Ar is an aromatic-bearing group, m is an integer of 2 to 6, the Ar groups may be the same or different, and L is a m-valent residue of a condensed polycyclic aromatic compound having 3 to 10 rings, with the proviso that where L is a di- or trivalent residue derived from anthracene, at least one Ar is an aromatic residue derived from an alkynylarene, and that where L is a tetravalent residue derived from naphthacene and Ar groups are attached at the 5-, 6-, 11- and 12-positions thereof, all the four Ar groups are not phenyl groups at the same time.
(2) The organic EL element of (1) wherein Ar is an aromatic hydrocarbon residue, and L is a di-, tri- or tetravalent residue derived from a condensed polycyclic aromatic hydrocarbon.
(3) The organic EL element of (2) wherein said condensed polycyclic aromatic hydrocarbon is naphthacene, pentacene or hexacene.
(4) The organic EL element of (1) wherein L is a trivalent residue derived from anthracene, two Ar groups are arylalkynyl groups, and one Ar group is a bis(arylalkynyl)anthryl group.
(5) The organic EL element of (1) wherein said organic compound layer containing said compound of the general formula (I) is a light emitting layer.
(6) The organic EL element of (5) wherein said light emitting layer contains a quinoline derivative.
(7) The organic EL element of (6) wherein said quinoline derivative is tris(8-quinolinolato)aluminum.
(8) The organic EL element of (5) wherein said light emitting layer is a mix layer of at least one hole injecting and transporting compound and at least one electron injecting and transporting compound.
(9) The organic EL element of (5) wherein said compound of the general formula (I) is contained in said light emitting layer in a concentration of 0.01 to 20% by weight.
(10) The organic EL element of (5) further comprising at least one hole injecting and transporting layer.
(11) The organic EL element of (10) wherein said hole injecting and transporting layer includes at least one hole injecting layer and at least one hole transporting layer, said light emitting layer adjoining the hole transporting layer.
(12) The organic EL element of (5) further comprising at least one electron injecting and transporting layer.
(13) The organic EL element of (12) wherein said electron injecting and transporting layer includes at least one electron injecting layer and at least one electron transporting layer, said light emitting layer adjoining the electron transporting layer.
FUNCTION AND EFFECT
According to the invention, a compound of the general formula (I) is contained in an organic compound layer, especially a light emitting layer. This results in an organic EL element capable of light emission in the wave-length range of about 460 to 700 nm, especially having the maximum wavelength of light emission in the long wavelength range. Particularly when the compound of the general formula (I) is used in a light emitting layer as a dopant for a host material having a light emitting function in itself or as a dopant in a mix layer with a light emitting function formed from a mixture of an electron injecting and transporting compound and a hole injecting and transporting compound, light emission of blue to red, especially long wavelength light emission is possible at sufficient luminance and the light emitting performance lasts long.
Although a variety of condensed polycyclic aromatic compounds are disclosed in JP-A 264692/1988, 32966/1993, 198377/1993, 214334/1993, and 258859/1993, their structure is apparently different from the compounds of the general formula (I) according to the invention.


REFERENCES:
patent: 4720432 (1988-01-01), Van Slyke et al.
patent: 4769292 (1988-09-01), Tang et al.
patent: 5077142 (1991-12-01), Sakon et al.
patent: 5151629 (1992-09-01), Vanslyke
patent: 5294869 (1994-03-01), Tang et al.
patent: 5393614 (1995-02-01), Nakada
patent: 5540999 (1996-07-01), Yamamoto et al.
patent: 5635308 (1997-06-01), Inoue et al.
patent: 63-264692 (1988-11-01), None
patent: 5-32966 (1993-02-01), None
patent: 5-178810 (1993-07-01), None
patent: 5-198377 (1993-08-01), None
patent: 5-214334 (1993-08-01), None
patent: 5-258859 (1993-10-01), None
patent: 6-220437 (1994-08-01), None
patent: 6-228555 (1994-08-01), None
patent: 6-271846 (1994-09-01), None

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