JPH0920886A - Organic electroluminescence element material and organic electroluminescence element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject material comprising a specific metal complex, capable of being used for organic electroluminescence, easy in the production of films by a wet film-forming method and a dry film-forming method, having a high luminous efficiency and a high brightness, and enabling to easily produce long life organic electroluminescence elements. SOLUTION: An organic electroluminescence element material comprises a compound of formula I [A<1> -A<7> do not form each a ring structure or form each a six-membered aromatic ring structure; one or more of A<1> -A<2> may form the rings and have one or more substituents at the substitutive positions of the condensed rings; the substituents may further be combined with each other to form a six-membered aromatic ring structure; L is a 1-10C alkyl(R), a group of formula: -OR, a 6-20C (N-containing) aryl (Ar), a group of formula: -OAr; M is a metal such as Be, Zn, Mg, Co, Cu, Ni, Al, Ga or In; m is 1-3; n is 0 wherein m+n is a positive integer satisfying 2 or 3], e.g. a compound of formula II.

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 device using an organic substance is expected to be used as an inexpensive, large-area, full-color display device of a solid light emitting type, and many developments have been made. Generally EL
Is composed of a light-emitting layer and a pair of opposed electrodes sandwiching the 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, 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.

[0003] Conventional organic EL devices have a higher driving voltage and lower luminous brightness and luminous efficiency than inorganic EL devices.
In addition, the characteristic deterioration was remarkable, and it had not been put to practical use.
2. Description of the Related Art In recent years, an organic EL in which a thin film containing an organic compound having high fluorescence quantum efficiency that emits light at a low voltage of 10 V or less is laminated.
Devices have been reported and are of interest (see Applied Physics Letters, vol. 51, p. 913, 1987). In this method, the metal chelate complex is converted into a phosphor layer,
High brightness green light emission is obtained by using an amine compound for the hole injection layer, and the brightness is 100 c at a DC voltage of 6 to 7 V.
d / m ² and maximum luminous efficiency of 1.5 lm / W,
Has performance close to the practical range. However, organic EL devices up to now have improved light emission intensity due to the improved structure, but do not yet have sufficient light emission luminance.
In addition, there is a major problem that the stability upon repeated use is poor.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic compound having high luminous efficiency and excellent stability when used repeatedly.
L element. As a result of intensive studies by the present inventors,
The present invention has been found that the organic EL element using at least one organic EL element material of the compound represented by the general formula [1] has high luminous efficiency and excellent stability upon repeated use, and has led to the present invention. 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]

Embedded image [In the formula, A ^{1 to} A ⁷ each do not form a ring structure or represent a 6-membered aromatic ring structure (provided that at least one of A ^{1 to} A ⁷ forms a ring and a condensed ring can be substituted). It may have a substituent at any position, and these substituents may be bonded to each other to form a further 6-membered aromatic ring structure), L
Is represented by -R, -Ar, -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). Represents a ligand, M represents a metal atom, m represents an integer of 1 to 3, and n represents 0 or a positive integer constituting 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 a layer containing the organic electroluminescent device material according to claim 1. It is an organic electroluminescent element characterized by the fact that it is present.

Further, according to the present invention, in an organic electroluminescence device having a light emitting layer or a plurality of organic compound thin film layers including a light emitting layer between a pair of electrodes, at least one layer between the light emitting layer and the cathode is claimed. It is an organic electroluminescent element characterized by being a layer containing the described organic electroluminescent element material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As the aromatic ring represented by the general formula [1] in the present invention, a benzene ring is shown, which is a substituent group substituted on a condensed ring in which at least four aromatic rings are condensed. Specific examples include chlorine, bromine, iodine, halogen atoms of fluorine, methyl group, ethyl group, propyl group, butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, Substituted or unsubstituted alkyl group such as octyl group, stearyl group, trichloromethyl group, phenyl group, naphthyl group, 3-methylphenyl group, 3-methoxyphenyl group, 3-fluorophenyl group, 3-trichloromethylphenyl group, 3
-Substituted or unsubstituted aryl groups such as trifluoromethylphenyl group and 3-nitrophenyl group, methoxy group,
n-butoxy group, tert-butoxy group, trichloromethoxy group, trifluoroethoxy group, pentafluoropropoxy group, 2,2,3,3-tetrafluoropropoxy group, 1,1,1,3,3,3-hexa Fluoro-2-
Substituted or unsubstituted alkoxy group such as propoxy group, 6- (perfluoroethyl) hexyloxy group, phenoxy group, p-nitrophenoxy group, p-tert-butylphenoxy group, 3-fluorophenoxy group, pentafluorophenyl group A substituted or unsubstituted aryloxy group such as 3-trifluoromethylphenoxy group, a methylthio group, an ethylthio group, a tert-butylthio group, a hexylthio group, an octylthio group, a substituted or unsubstituted alkylthio group such as a trifluoromethylthio group, A substituted or unsubstituted arylthio group such as phenylthio group, p-nitrophenylthio group, p-tert-butylphenylthio group, 3-fluorophenylthio group, pentafluorophenylthio group, 3-trifluoromethylphenylthio group, Cyano group B group, amino group, methylamino group,
Mono- or di-substituted amino groups such as diethylamino group, ethylamino group, diethylamino group, dipropylamino group, dibutylamino group, diphenylamino group, bis (acetoxymethyl) amino group, bis (acetoxyethyl) amino group, bisacetoxypropyl ) Amino group, acylamino group such as bis (acetoxybutyl) amino group, hydroxyl group, siloxy group, acyl group, methylcarbamoyl group, dimethylcarbamoyl group, ethylcarbamoyl group, diethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, phenyl Carbamoyl group such as carbamoyl group, carboxylic acid group, sulfonic acid group, imide group, cyclopentane group, aliphatic ring group such as cyclohexyl group, carbocyclic aromatic group such as phenyl group, naphthyl group and biphenyl group, pyridine group , Pi Heterocyclic aromatic groups such as gin group, pyrimidine group, pyridazine group, triazine group, indole group, quinoline group, acridine group, etc., heterocyclic groups such as pyrrolidine group, dioxane group, piperidine group, morpholine group, piperazine group and trithian group There are ring groups, etc. Further, the above substituents may be bonded to each other to form a further 6-membered aromatic ring.

In the present invention, represented by the general formula [1],
Typical examples of the ligand L 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 anthranyl group and a 9-chloro-anthranyl group. An aryl group which may have a substituent such as methoxy group, an ethoxy group, an isopropoxy group, a butoxy group, an alkoxy group which may have a substituent such as 1,1,2,2-tetrafluoroethoxy group, a phenoxy group Group, an naphthyloxy group, an anthracenyl group, an aryloxy group which may have a substituent such as a pyrenyl group, and an 8-oxyquinolinol, a 2-methyl-8-quinolinol which may have a substituent such as 8- Quinolinol derivative, 4-
Mention may be made of 10-hydroxybenzoquinolinol derivatives which may have a substituent such as 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.

The method of synthesizing the compound of the general formula [1] of the present invention comprises reacting a corresponding ligand with a metal alkoxide, a metal halide, a metal acetyl compound or the like in a solvent such as toluene or alcohol. These metal complexes are synthesized, but are not limited thereto.

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 an anode or electrons injected from a 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 multilayer 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. Further, since the thin film layer containing this compound has strong fluorescence under an electric field, it can be used as a light emitting material, and high emission efficiency and optimum selection of emission wavelength have become 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 injection layer, the light-emitting layer, and the electron injection layer may each be formed in a layer structure of two or more layers, and an element structure in which holes or electrons are efficiently injected from the electrode and transported in the layer is selected. You.

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 of less 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 thereto. The anode and the cathode may be formed by 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. Further, it is desirable that the substrate is also transparent. The transparent electrode is set so as to secure a predetermined translucency by a method such as vapor deposition or sputtering using the above conductive material. The electrode on the light emitting surface desirably has a light transmittance of 10% or more. The substrate is not limited as long as it has mechanical and thermal strength and 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 small, pinholes and the like are generated, and sufficient light emission luminance cannot be obtained even when an electric field is applied. Normal thickness is 5nm to 10μ
The range of m is suitable, but the range of 10 nm to 0.2 μm is more preferable.

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, polymethyl methacrylate, polymethyl acrylate, and cellulose, and poly-N-.
Examples include photoconductive resins such as vinyl carbazole and polysilane, and conductive resins such as polythiophene and polypyrrole. Examples of the additive include an antioxidant, an ultraviolet absorber, and a plasticizer.

Examples of the light emitting material or doping material that 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 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 Arylalkane, stilbene, butadiene,
Benzidine-type triphenylamine, styrylamine-type triphenylamine, diamine-type triphenylamine and the like, and derivatives thereof, and polyvinyl carbazole,
Although there are polymer materials such as polysilane and conductive polymer,
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, thiopyrandioxide, oxadiazole, thiadiazole, tetrazole, perylenetetracarboxylic acid, fluorenylidenemethane, anthraquinodimethane, anthrone and the like, and derivatives thereof. However, the present invention is not limited to this. 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 is preferably used in a light emitting layer as a light emitting material, and at least one of a light emitting material, a doping material, a hole transporting material and an electron transporting material is provided in the same layer. It may be contained. Also,
Since the compound of the general formula [1] has an electron transporting ability, it can be used in the electron injection layer.

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 element of the present invention can be used for flat panel displays such as wall-mounted televisions,
The flat illuminant can be applied to light sources such as copiers and printers, light sources such as liquid crystal displays and instruments, display boards, and sign lamps, and its industrial value is very large.

[0031]

The present invention will be described in more detail based on the following examples. Method for synthesizing compound (4) 7-cyano-12-hydroxy-naphtho [2,3-h]
Dissolve 8 parts of quinoline in 200 parts of ethanol by heating.
To this, a solution of 5 parts of beryllium sulfate in 50 parts of water was added dropwise, and the mixture was heated with stirring at 60 ° C. for 2 hours, and the precipitated crystals were separated by filtration, washed with methanol and dried to give yellow crystals 5.5.
Got a part. Furthermore, 5 parts of this crystal was added to 10 ^-5 Toor,
1. By purifying by sublimation at 300 ° C., a yellow solid 2.
8 parts were obtained. It was confirmed to be the compound (4) by elemental analysis, molecular weight analysis, infrared absorption spectrum and NMR spectrum.

Examples 1 to 30 On a cleaned glass plate with an ITO electrode, N, N '-(4
-Methylphenyl) -N, N '-(4-n-butylphenyl) -phenanthrene-9,10-diamine was vacuum-deposited to obtain a 50 nm-thick hole injection layer. 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.

[0033]

[Table 2]

Comparative Example 1 The metal complex of the light emitting layer was prepared from the compound of the example by 10-hydroxide.
Roxybenzo [h] quinoline beryllium complex
Except for the above, organic EL devices were manufactured in the same manner as in Examples 1 to 30.
It was manufactured and the emission brightness was measured. This element has a DC voltage of 5V
950 cd / m ^TwoThe emission luminance of was obtained.

Example 31 Compound (3) was added on a washed glass plate with an ITO electrode.
Poly-N-vinylcarbazole was dissolved and dispersed in chloroform at a ratio of 3: 5, and spin coating was performed to obtain a light emitting layer having a film thickness of 100 nm. An electrode having a thickness of 150 nm was formed thereon with an alloy of magnesium and silver mixed at a ratio of 10: 1 to obtain an organic EL device. 1 for the light emitting layer and the cathode
Vapor deposition was performed at a substrate temperature of room temperature in a vacuum of 0 ^-6 Torr. This device provided a light emission luminance of 400 cd / m ² at a DC voltage of 5V.

Example 32 On a washed glass plate with an ITO electrode, the compound (6),
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 is 100n
m light emitting layers were 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
Vapor deposition was performed at a substrate temperature of room temperature in a vacuum of orr.
This device provided a light emission luminance of 520 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 (9) is vapor-deposited to form a light-emitting layer having a thickness of 30 nm, and then 2- (4-tert-butylphenyl)-is formed by a vacuum vapor deposition method.
An electron injection layer having a thickness of 20 nm of 5- (biphenyl) -1,3,4-oxadiazole was obtained. An electrode having a film thickness of 100 nm was formed thereon 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 and the light emitting layer were deposited in a vacuum of 10 ^-6 Torr at a substrate temperature of room temperature. This device has a DC voltage of 5V and a voltage of 1350c
An emission luminance of d / m ² was obtained.

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 thickness of 30 nm. Then, the compound (11) 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-oxa is formed by a vacuum vapor deposition method. An electron injection layer having a film thickness of 20 nm of diazole was obtained. An electrode having a thickness of 150 nm was formed thereon with an alloy of magnesium and silver mixed at a ratio of 10: 1 to obtain an organic EL device.
The hole injection layer, the light emitting layer, the electron injection layer and the cathode are 10 ^−6.
Deposition was performed in a Torr vacuum at a substrate temperature of room temperature. This device provided a light emission luminance of about 1550 cd / m ² 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 (16) was used in place 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 1620 cd / m ² at a DC voltage of 5 V.
The emission luminance of was obtained.

All the organic EL devices shown in this example obtained an initial maximum brightness of 10,000 cd / m ² or more. Furthermore, all of the organic E's shown in this example are
When the L element was made to continuously emit light at 3 mA / cm ² , it was possible to observe stable light emission for 1000 hours or more. However, the organic EL element of Comparative Example produced under the same conditions was 50
When the light emission time was 0 hours or less, it became less than half of the initial light emission luminance. The organic EL device of the present invention achieves improvement of luminous efficiency, luminous luminance and long life, and is used together with a luminescent material, a doping material, a hole transport material, an electron transport material, a sensitizer, and a resin. It does not limit the electrode material, etc., and the element manufacturing method.

[0041]

According to the present invention, it is possible to obtain an organic EL device having higher luminous efficiency, higher luminance and longer life than the conventional one. This is because by using the compound shown in the present invention in an organic EL device, wet and dry film formation methods are easy, and an organic EL device having high emission brightness and high emission efficiency can be easily produced. Became.

Claims (3)

[Claims] 1. An organic electroluminescence element material represented by the following general formula [1]. General formula [1] [In the formula, A ^{1 to} A ⁷ each do not form a ring structure or represent a 6-membered aromatic ring structure (provided that at least one of A ^{1 to} A ⁷ forms a ring and a condensed ring can be substituted). It may have a substituent at any position, and these substituents may be bonded to each other to form a further 6-membered aromatic ring structure), L
Is represented by -R, -Ar, -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). Represents a ligand, M represents a metal atom, m represents an integer of 1 to 3, and n represents 0 or a positive integer constituting 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 electroluminescent 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 and the cathode is an organic electroluminescent device. An organic electroluminescence device, which is a layer containing a luminescence device material.