JP3465420B2 - Organic electroluminescent device material and organic electroluminescent device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (EL) element used for a flat light source or a display.

[0002]

2. Description of the Related Art An EL element using an organic substance is expected to be used as a solid-state light emitting type inexpensive large area full color display element, and many developments have been made. Generally EL
Is composed of a light emitting layer and a pair of counter electrodes sandwiching the light emitting layer. In light emission, when an electric field is applied between both electrodes, electrons are injected from the cathode side and holes are injected from the anode side. Further, this is a phenomenon in which the electrons are recombined with holes in the light emitting layer, and energy is emitted as light when the energy level returns from the conduction band to the valence band.

Conventional organic EL elements are more than inorganic EL elements.
The driving voltage was high, and the light emission luminance and light emission efficiency were low.
In addition, the deterioration of the characteristics was remarkable and it was not put to practical use.
In recent years, high fluorescence quantum efficiency of emitting light at a low voltage of 10 V or less
Organic EL layered with thin films containing organic compounds
The device has been reported and is of interest (Applied
Zix Letters, 51, 913 pages, 1987
reference). In this method, the metal chelate complex is added to the phosphor layer,
High brightness green by using amine compound in hole injection layer
It emits light and has a brightness of 1000 at a DC voltage of 6 to 7V.
cd / m ²Achieves maximum luminous efficiency of 1.5 lm / W
And has performance close to the practical range. However,
Up to the present, organic EL devices have improved luminescence intensity due to the improved structure.
Have been improved, but they still do not have sufficient emission brightness.
Yes. In addition, the stability is poor after repeated use.
There's a problem.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic E which has high emission brightness and excellent stability during repeated use.
It is to provide the L element. As a result of intensive studies by the present inventors,
The present inventors have found that an organic EL device using at least one organic EL device material of the compound represented by the general formula [1] has a high luminous efficiency and is excellent in stability even after repeated use. It was

[0005]

That is, the present invention relates to an organic electroluminescence device material comprising a compound represented by the following general formula [1].

General formula [1]

[Chemical 2] [In the formula, each of the rings A ^{1 to} A ³ represents a 6-membered aromatic ring structure which may be substituted and is condensed with each other (provided that the ring A ^{1 to} A ³ is
¹ or ring A ² contains at least one nitrogen atom, or ring A ³ is a heterocyclic aromatic ring group containing a further nitrogen atom, and adjacent substituents are bonded to each other to form a further condensed aromatic ring. You may form a ring. ), L is -R, -A
represents a ligand represented by r, -OR, -OAr (R is an alkyl group having 1 to 10 carbon atoms, and Ar is an aryl group having 6 to 20 carbon atoms and optionally containing a nitrogen atom). , M represents a metal atom, m represents an integer of 1 to 3,
n represents a positive integer constituting 0 or m + n = 2 or 3. ]

Furthermore, the present invention provides an organic electroluminescent device comprising an organic compound thin film layer including a light emitting layer between a pair of electrodes, wherein the light emitting layer is the organic electroluminescent device material represented by the general formula [1]. It is an organic electroluminescence element which is a layer to be contained.

Furthermore, the present invention is an organic electroluminescence device comprising a light emitting layer or a plurality of organic compound thin film layers including a light emitting layer between a pair of electrodes, wherein at least one layer between the light emitting layer or the light emitting layer and the cathode is provided. , An organic electroluminescent element which is a layer containing the organic electroluminescent element material represented by the general formula [1].

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of the substituent of the ring represented by the general formula [1] include chlorine, bromine, iodine, a halogen atom of fluorine, a methyl group, an ethyl group, a propyl group,
Substituted or unsubstituted alkyl groups such as butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, stearyl group, trichloromethyl group, phenyl group, naphthyl group, 3-methylphenyl group A substituted or unsubstituted aryl group such as 3-methoxyphenyl group, 3-fluorophenyl group, 3-trichloromethylphenyl group, 3-trifluoromethylphenyl group, 3-nitrophenyl group, methoxy group, n-butoxy group, tert. -Butoxy group, trichloromethoxy group, trifluoroethoxy group, pentafluoropropoxy group, 2,2,3,3-tetrafluoropropoxy group,
Substituted or unsubstituted alkoxy groups such as 1,1,1,3,3,3-hexafluoro-2-propoxy group and 6- (perfluoroethyl) hexyloxy group, phenoxy group, p-nitrophenoxy group, p -Tert-butylphenoxy group, 3-fluorophenoxy group, pentafluorophenyl group, substituted or unsubstituted aryloxy group such as 3-trifluoromethylphenoxy group, methylthio group, ethylthio group, tert-butylthio group, hexylthio group, Substituted or unsubstituted alkylthio group such as octylthio group and trifluoromethylthio group, phenylthio group, p-nitrophenylthio group, p-tert-butylphenylthio group, 3-fluorophenylthio group, pentafluorophenylthio group, 3 -Substitution of trifluoromethylphenylthio group, etc. Properly is unsubstituted arylthio group,
Mono- or di-substituted amino groups such as cyano group, nitro group, amino group, methylamino group, diethylamino group, ethylamino group, diethylamino group, dipropylamino group, dibutylamino group, diphenylamino group, bis (acetoxymethyl) amino Groups, bis (acetoxyethyl) amino groups, bis (acetoxypropyl) amino groups, bis (acetoxybutyl) amino groups, and other acylamino groups, hydroxyl groups, siloxy groups, acyl groups, methylcarbamoyl groups, dimethylcarbamoyl groups, ethylcarbamoyl groups, diethyl Carbamoyl group, propylcarbamoyl group, butylcarbamoyl group, carbamoyl group such as phenylcarbamoyl group, carboxylic acid group, sulfonic acid group, imido group, cyclopentane group, aliphatic ring group such as cyclohexyl group, phenyl group, naphthyl group, B Carbocyclic aromatic group such as phenyl group, pyridine group, pyrazine group, pyrimidine group, pyridazine group, triazine group, indole group, quinoline group, heterocyclic aromatic group such as acridine group, pyrrolidine group, dioxane group, piperidine And a heterocyclic group such as a morpholine group, a piperazine group and a trithiane group. Further, the above substituents may be bonded to each other to form a further 6-membered aromatic ring.

Typical examples of the ligand L of the general formula [1] include an alkyl group which may have a substituent such as a methyl group, an ethyl group, a propyl group and a trifluoromethyl group, a phenyl group, a naphthyl group, An aryl group which may have a substituent such as anthranyl group and phenanthrenyl group, methoxy group, ethoxy group, isopropoxy group, butoxy group, 1,1,2,
An aryloxy group which may have a substituent such as a 2-tetrafluoroethoxy group and the like, a phenoxy group, a naphthyloxy group, an anthracenyl group, a pyrenyl group and the like, and 8-quinolinol An 8-quinolinol derivative which may have a substituent such as 2-methyl-8-quinolinol, 10-hydroxybenzoquinolinol,
Examples thereof include a 10-hydroxybenzoquinolinol derivative which may have a substituent such as 4-methyl-10-hydroxybenzoquinolinol.

The metal M may be any divalent or trivalent metal atom, but Be, Zn, Mg, Co, C
u, Ni, Al, Ga or In is preferred.

Examples of the method for synthesizing the compound of the general formula [1] of the present invention are shown below, but the invention is not limited thereto.
First, the ligand (Li et al., Chemistry Bulletin, 1984, 42
Vol., Page 823) and the like, and further by the method of (Yoshino et al., Journal of the Chemical Society of Japan, 1957, vol. 78, p. 108) and the like, with the above ligand, a metal or metal alkoxide, a metal halide, The metal complex represented by the general formula [1] can be obtained by reacting a metal compound such as a metal acetyl compound in an organic solvent such as toluene, alcohol, or ether.

Representative examples of the compounds of the present invention are specifically shown in Table 1, but the invention is not limited thereto.

[0014]

[Table 1]

[0015]

[0016]

[0017]

[0018]

The organic EL element is an element in which a single-layer or multi-layer organic thin film is formed between an anode and a cathode. In the case of the single layer type, a light emitting layer is provided between the anode and the cathode. The light emitting layer contains a light emitting material, and may further contain a hole transport material or an electron transport material for transporting holes injected from the anode or electrons injected from the cathode to the light emitting material. The multilayer type is (anode / hole injection layer / light emitting layer /
There is an organic EL device having a multi-layer structure of (cathode), (anode / light emitting layer / electron injection layer / cathode), and (anode / hole injection layer / light emitting layer / electron injection layer / cathode). Since the compound of the general formula [1] is an electron-transporting compound, it can be used for an electron-injecting layer, an electron-transporting layer, an electron-transporting light-emitting layer and the like by utilizing its electron-transporting property. In addition, an organic EL element using an organic thin film containing this compound emits strong blue to green fluorescence when an electric field is applied, and thus can be used as a light emitting material, and has high emission brightness and emission wavelength. The optimal choice of became possible.

When the organic EL element has a multi-layered structure, it is possible to prevent deterioration of brightness and life due to quenching. Further, if necessary, two or more kinds of a light emitting material, a doping material, a hole transporting material for carrying carriers and an electron transporting material can be used in combination. Also,
The hole injecting layer, the light emitting layer, and the electron injecting layer may each be formed of a layer structure of two or more layers, and a device structure in which holes or electrons are efficiently injected from the electrode and transported in the layer is selected. It

The conductive material used for the anode of the organic EL device is preferably one having a work function larger than 4 eV, such as carbon, aluminum, vanadium, iron, cobalt,
Nickel, tungsten, silver, gold, platinum, palladium and their alloys, ITO substrates, metal oxides such as tin oxide and indium oxide called NESA substrates, and organic conductive resins such as polythiophene and polypyrrole are used. . The conductive material used for the cathode is preferably one having a work function smaller than 4 eV, such as magnesium, calcium, tin, lead, titanium, yttrium,
Lithium, ruthenium, manganese and the like and alloys thereof are used, but not limited to these. The anode and the cathode may be formed in a layered structure of two or more layers if necessary.

In the organic EL device, it is desirable that at least one of them is sufficiently transparent in the emission wavelength region of the device in order to emit light efficiently. It is also desirable that the substrate is transparent. The transparent electrode is set using the above-mentioned conductive material so as to ensure a predetermined translucency by a method such as vapor deposition or sputtering. The electrode on the light emitting surface preferably has a light transmittance of 10% or more. The substrate has mechanical and thermal strength and is not limited as long as it is transparent, but examples thereof include a transparent resin such as a glass substrate, a polyethylene plate, a polyether sulfone plate, and a polypropylene plate. .

For forming each layer of the organic EL device according to the present invention, any of dry film forming methods such as vacuum deposition and sputtering and wet film forming methods such as spin coating and dipping can be applied. The film thickness is not particularly limited, but each layer needs to be set to an appropriate film thickness. If the film thickness is too thick, a large applied voltage is required to obtain a constant light output, resulting in poor efficiency. If the film thickness is too thin, pinholes and the like will occur, and even if an electric field is applied, sufficient emission brightness cannot be obtained. Normal film thickness is 5nm to 10μ
The range of m is preferred, but the range of 10 nm to 0.2 μm is more preferred.

In the case of the wet film forming method, the material forming each layer is dissolved or dispersed in an appropriate solvent such as chloroform, tetrahydrofuran, dioxane to form a thin film.
The solvent may be any. Further, in any of the thin films, an appropriate resin or additive may be used in order to improve the film forming property and prevent pinholes in the film. Examples of such a resin include insulating resins such as polystyrene, polycarbonate, polyarylate, polyester, polyamide, polyurethane, polysulfone, polymethylmethacrylate, polymethylacrylate and cellulose, and poly-N-
Examples thereof include photoconductive resins such as vinylcarbazole and polysilane, and conductive resins such as polythiophene and polypyrrole. Examples of the additives include antioxidants, ultraviolet absorbers, plasticizers and the like.

Examples of the light emitting material or doping material which can be used in the organic EL device of the present invention include anthracene, naphthalene, phenanthrene, pyrene, tetracene, coronene, chrysene, fluorescein, perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone,
Naphthaloperinone, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, pyrazine, cyclopentadiene, quinoline metal complex, aminoquinoline metal complex, imine, diphenylethylene, vinylanthracene, diaminocarbazole, pyran , Thiopyran, polymethine, merocyanine, imidazole chelated oxinoid compounds, quinacridone, rubrene and the like, and derivatives thereof, but are not limited thereto.

The hole-transporting material has the ability to transport holes, has an excellent hole-injecting effect on the light-emitting layer or the light-emitting material, and has an electron-injecting layer or electrons for excitons generated in the light-emitting layer. Examples thereof include compounds that prevent migration to transport materials and have excellent thin film forming ability. Specifically, phthalocyanine compounds, naphthalocyanine compounds, porphyrin compounds, oxadiazole, triazole, imidazole, imidazolone, imidazolethione, pyrazoline, pyrazolone, tetrahydroimidazole, oxazole, oxadiazole, hydrazone, acylhydrazone, poly Aryl alkane, stilbene, butadiene,
Benzidine-type triphenylamine, styrylamine-type triphenylamine, diamine-type triphenylamine, and their derivatives, and polyvinylcarbazole,
There are polymer materials such as polysilane and conductive polymers,
It is not limited to these.

The electron-transporting material has the ability to transport electrons, has an excellent electron-injecting effect on the light-emitting layer or the light-emitting material, and excites generated in the light-emitting layer in the hole-injecting layer or hole-transporting layer. Examples thereof include compounds that prevent transfer to the material and have excellent thin film forming ability. For example, there are fluorenone, anthraquinodimethane, diphenoquinone, thiopyran dioxide, oxadiazole, thiadiazole, tetrazole, perylene tetracarboxylic acid, fluorenylidene methane, anthraquinodimethane, anthrone and their derivatives. It is not limited to. Further, an electron accepting substance may be added to the hole transporting material and an electron donating substance may be added to the electron transporting material to sensitize.

The compound of the general formula [1] of the present invention can be used in a light emitting layer as a light emitting material.
At least one of the doping material, the hole transporting material and the electron transporting material may be contained in the same layer. In addition, since the compound of the general formula [1] has a high electron transporting ability, it can be used in the electron injecting layer or the electron transporting layer between the light emitting layer and the cathode.

In order to improve the stability of the organic EL device obtained by the present invention against temperature, humidity, atmosphere, etc., a protective layer is provided on the surface of the device or silicon oil or the like is enclosed to protect the entire device. It is also possible to do so.

As described above, in the present invention, since the compound of the general formula [1] is used for the organic EL device, the luminous efficiency can be increased. In addition, this device is extremely stable against heat and current, and because it can obtain practically usable light emission brightness at low voltage, deterioration and light emission time that have been a big problem until now Was greatly improved, and it was possible to contribute to the improvement of the life of the organic EL element. . The organic EL device of the present invention is a flat panel display such as a wall-mounted TV,
As a plane light emitter, it can be considered to be applied to a light source of a copying machine or a printer, a light source of a liquid crystal display or instruments, a display plate, a marker lamp, etc., and its industrial value is very large.

[0031]

The present invention will be described in more detail based on the following examples.

5 parts of 8-hydroxy-1,4-phenanthroline was dissolved in 100 parts of absolute ethanol by heating, and a solution prepared by dissolving 4 parts of zinc acetate in 100 parts of absolute ethanol was added thereto. By stirring this mixed solution at 50 ° C. for 2 hours, yellow fluorescent crystals are precipitated. The crystals were separated by filtration and washed with absolute ethanol to obtain 6 parts of yellow crystals. From the results of elemental analysis, molecular weight analysis, infrared absorption spectrum and NMR spectrum, it was confirmed to be the compound (6).

Examples 1 to 30 On a cleaned glass plate with ITO electrodes, N, N '-(4
-Methylphenyl) -N, N '-(4-n-butylphenyl) -phenanthrene-9,10-diamine was vacuum-deposited to obtain a hole injection layer having a film thickness of 50 nm. Next, the compounds shown in Table 2 were vacuum-deposited to form a light-emitting layer having a thickness of 50 nm, and an electrode having a thickness of 150 nm was formed on the light-emitting layer having a thickness of 50: 1. Thus, an organic EL device was obtained. The hole injection layer, the light emitting layer and the cathode were vapor-deposited in a vacuum of 10 ⁻⁶ Torr and at a substrate temperature of room temperature. With this device, the emission luminance shown in Table 2 was obtained at a DC voltage of 5V.

[0034]

[Table 2]

Comparative Example 1 An organic EL device was prepared in the same manner as in Examples 1 to 30, except that the metal complex of the light emitting layer was changed from the compound of Example to 10-hydroxybenzo [h] quinoline beryllium complex. The luminescence brightness was measured. This element has a DC voltage of 5V
In this way, an emission luminance of 950 cd / m ² was obtained.

Example 31 Compound (2) was added onto a washed glass plate with an ITO electrode.
Poly-N-vinylcarbazole was dissolved and dispersed in chloroform at a ratio of 3: 5, and a light emitting layer having a film thickness of 100 nm was obtained by a spin coating method. An electrode having a film thickness of 150 nm was formed on it with an alloy in which magnesium and silver were mixed at a ratio of 10: 1 to obtain an organic EL element. The light emitting layer and the cathode are
Deposition was performed under the conditions of a substrate temperature of room temperature in a vacuum of 10 ⁻⁶ Torr. This device provided a light emission luminance of 350 cd / m ² at a DC voltage of 5V.

Example 32 On a washed glass plate with an ITO electrode, compound (4),
2- (4-tert-butylphenyl) -5- (biphenyl) -1,3,4-oxadiazole and poly-N-vinylcarbazole were dissolved and dispersed in chloroform at a ratio of 3: 2: 5, and spin coating was performed. Film thickness of 100
A light emitting layer of nm was obtained. On top of that, add 1 magnesium and 1 silver
An electrode having a thickness of 150 nm was formed from the alloy mixed at 0: 1 to obtain an organic EL device. The light emitting layer and the cathode are 10 ⁻⁶ T
Deposition was performed under the conditions of a substrate temperature of room temperature in a vacuum of orr.
This device provided a light emission luminance of 510 cd / m ² at a DC voltage of 5V.

Example 33 N, N '-(4
-Methylphenyl) -N, N '-(4-n-butylphenyl) -phenanthrene-9,10-diamine was dissolved and dispersed in chloroform, and a hole injection layer having a thickness of 30 nm was obtained by spin coating. Then, the compound (7) is vapor-deposited to form a light-emitting layer having a thickness of 30 nm, and further 2- (4-tert-butylphenyl) -5 is formed by a vacuum vapor deposition method.
An electron injection layer having a thickness of 20 nm of-(biphenyl) -1,3,4-oxadiazole was obtained. An electrode having a film thickness of 150 nm was formed on it with an alloy in which magnesium and silver were mixed at a ratio of 10: 1 to obtain an organic EL element. The hole injecting layer, the light emitting layer, the electron injecting layer, and the cathode were vapor-deposited under the conditions of the substrate temperature and room temperature in a vacuum of 10 ⁻⁶ Torr. This device provided a luminescent brightness of 1400 cd / m ² at a DC voltage of 5V.

Example 34 N, N '-(4
-Methylphenyl) -N, N '-(4-n-butylphenyl) -phenanthrene-9,10-diamine was vacuum-deposited to obtain a hole injection layer having a film thickness of 30 nm. Then, the compound (7) is vapor-deposited to form a light-emitting layer having a film thickness of 30 nm, and further 2- (4-tert-butylphenyl) -5- (biphenyl) -1,3,4-by vacuum vapor deposition. An electron injection layer having a film thickness of 20 nm of oxadiazole was obtained. An electrode having a film thickness of 150 nm was formed on it with an alloy in which magnesium and silver were mixed at a ratio of 10: 1 to obtain an organic EL element. The hole injection layer, the light emitting layer, the electron injection layer and the cathode are 10 ⁻⁶ T
Deposition was performed under the conditions of a substrate temperature of room temperature in a vacuum of orr.
With this device, an emission luminance of 1510 cd / m ² was obtained at a DC voltage of 5V.

Example 35 [2- (4-Tert-butylphenyl) was used for the electron injection layer.
Example 2 except that the compound (15) is used instead of [-5- (biphenyl) -1,3,4-oxadiazole].
An organic EL device was prepared in the same manner as in Example 0 and the emission brightness was measured. This element is 1550 cd / m ² at DC voltage 5V.
The emission luminance of was obtained.

All the organic EL devices shown in this example obtained an initial maximum emission luminance of 10,000 cd / m ² or more. Furthermore, when all the organic EL devices shown in this example were made to continuously emit light at 3 mA / cm ² , stable light emission could be observed for 1000 hours or more, but in the comparative example produced under the same conditions. In the organic EL device, the emission luminance was reduced to less than half of the initial emission luminance in the emission time of 500 hours or less. INDUSTRIAL APPLICABILITY The organic EL device of the present invention achieves improvement of luminous efficiency, luminous brightness and prolongation of life, and is used together with a luminescent substance, doping material, hole transporting material, electron transporting material, sensitizer, resin. There is no limitation on the electrode material, etc. and the method for manufacturing the element.

[0042]

According to the present invention, it is possible to obtain an organic EL device having higher luminous efficiency, higher luminance and longer life than ever before. By using the compound shown in the present invention for the organic EL device, the wet and dry film formation methods are easy, and the organic EL device having high luminous efficiency can be easily produced.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-95620 (JP, A) JP-A-8-301877 (JP, A) JP-A-7-133281 (JP, A) JP-A-7- 97568 (JP, A) JP 7-48385 (JP, A) JP 6-322362 (JP, A) JP 8-315982 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09K 11/06 H05B 33/14 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. An organic electroluminescence element material represented by the following general formula [1]. General formula [1] [In the formula, each of the rings A ^{1 to} A ³ represents a 6-membered aromatic ring structure which may be substituted and is condensed with each other (provided that the ring A ^{1 to} A ³ is
¹ or ring A ² contains at least one nitrogen atom, or ring A ³ is a heterocyclic aromatic ring group containing a further nitrogen atom, and adjacent substituents are bonded to each other to form a further condensed aromatic ring. You may form a ring. ), L is -R, -A
represents a ligand represented by r, -OR, -OAr (R is an alkyl group having 1 to 10 carbon atoms, and Ar is an aryl group having 6 to 20 carbon atoms and optionally containing a nitrogen atom). , M represents a metal atom, m represents an integer of 1 to 3,
n represents a positive integer constituting 0 or m + n = 2 or 3. ] 2. An organic electroluminescent device comprising an organic compound thin film layer including a light emitting layer between a pair of electrodes, wherein the light emitting layer is a layer containing the organic electroluminescent device material according to claim 1. And an organic electroluminescent device. 3. An organic electroluminescence device comprising a light emitting layer or a plurality of organic compound thin film layers including a light emitting layer between a pair of electrodes, wherein at least one layer between the light emitting layer or the light emitting layer and the cathode is provided. 2. An organic electroluminescent device, which is a layer containing the organic electroluminescent device material described above.