JP3767049B2 - Organic electroluminescence device material and organic electroluminescence device using the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an organic electroluminescence (EL) element used for a planar light source and display.
[0002]
[Prior art]
An EL element using an organic substance is considered to be promising for use as an inexpensive large-area full-color display element of a solid light emitting type, and many developments have been made. In general, an EL is composed of a light emitting layer and a pair of counter 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. Furthermore, this electron is 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 elements have a higher driving voltage and lower light emission luminance and light emission efficiency than inorganic EL elements. Further, the characteristic deterioration has been remarkably not put into practical use.
In recent years, organic EL devices in which thin films containing organic compounds with high fluorescence quantum efficiency that emit light at a low voltage of 10 V or less have been reported and attracted attention (Applied Physics Letters, Vol. 51, page 913). 1987).
In this method, a metal chelate complex is used as a phosphor layer and an amine compound is used as a hole injection layer to obtain high luminance green light emission. The luminance is 100 cd / m ² at a direct current voltage of 6 to 7 V, maximum The luminous efficiency is 1.5 lm / W, and the performance is close to the practical range. However, the organic EL elements up to now have improved light emission intensity due to the improvement of the structure, but do not yet have sufficient light emission luminance. Moreover, it has a big problem that it is inferior in stability during repeated use.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an organic EL device having high luminous efficiency and excellent stability during repeated use. As a result of intensive studies by the present inventors, the organic EL device using at least one layer of the organic EL device material of the compound represented by the general formula [1] has high luminous efficiency, and stability during repeated use. It was found that it was excellent and resulted in the present invention.
[0005]
[Means for Solving the Problems]
That is, the present invention is an organic electroluminescence element material represented by the following general formula [1].
General formula [1]
[Chemical 2]
[Wherein, X ^{1 to} X ³ each independently represent N, CH, or a carbon atom bonded to Ar ¹ or Ar ² , provided that at least one of X ^{1 to} X ³ is bonded to Ar ¹ or Ar ² . Represents a carbon atom. Z represents S or N—R ¹ . R ¹ represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group. Ar ¹ and Ar ² each independently represent a substituted or unsubstituted arylene group. Ar ^{3 to} Ar ⁵ are each independently a hydrogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group Represents. m or n represents an integer of 0 to 4, but m + n = 0 does not occur.
However,
Is
One of them. ]
[0006]
Furthermore, the present invention is an organic electroluminescence element in which a plurality of organic compound thin films including a light emitting layer are formed between a pair of electrodes, wherein at least one layer is a layer containing the organic electroluminescence element material. .
[0007]
Furthermore, this invention is an organic electroluminescent element whose light emitting layer is a layer containing the said organic electroluminescent element material.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
[0009]
X ^{1 to} X ³ in the hetero five-membered ring of the compound represented by the general formula [1] in the present invention independently represent N, CH, or a carbon atom bonded to Ar ¹ or Ar ² , provided that X ^{1 to} X ^At least one of ³ represents a carbon atom bonded to Ar ¹ or Ar ² . Z represents S or N—R ¹ . Here, R ¹ represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group. Examples of alkyl groups include methyl, ethyl, propyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, stearyl and trichloromethyl groups. Specific examples of cycloalkyl include a cyclopentane ring and a cyclohexane ring, and substituted or unsubstituted aryl groups include a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a fluorenyl group. A substituted or unsubstituted heterocyclic group includes a pyrrole group, a pyrroline group, a pyrazole group, a pyrazoline group, an imidazole group, a triazole group, a pyridine group, a pyridazine group, a pyrimidine group, a pyrazine group, and a triazine group. , Indole group, purine group, quinoline group, isoquinolyl Group, sinoline group, quinoxaline group, benzoquinoline group, fluorenone group, carbazole group, oxazole group, oxadiazole group, thiazole group, thiadiazole group, triazole group, imidazole group, benzoxazole group, benzothiazole group, benzotriazole group, Complex such as benzimidazole group, bisbenzoxazole group, bisbenzothiazole group, bisbenzoimidazole group, anthrone group, dibenzofuran group, dibenzothiophene group, anthraquinone group, acridone group, phenothiazine group, pyrrolidine group, dioxane group, morpholine group There are ring groups.
[0010]
To display the example of the five-membered heterocyclic Table 1.
[0011]
[0012]
[0013]
[0014]
Specific examples of the arylene groups of Ar ¹ and Ar ² constituting the general formula [1] include phenylene group, naphthylene group, anthracenediyl group, pyrenidiyl group, triphenylene group, fluorenyl group, anthraquinone group, phenanthrenyl group, azulenyl group, and the like. There is. The aryl group may have a substituent. m or n represents an integer of 0 to 4, but m + n = 0 does not occur.
[0015]
Ar ^{3 to} Ar ^{5 in} the general formula [1] are each independently a hydrogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or substituted or unsubstituted Represents an unsubstituted heterocyclic group. Examples of the alkyl group, cycloalkyl group, substituted or unsubstituted aryl group, or substituted or unsubstituted heterocyclic group represented by Ar ^{3 to} Ar ⁵ include the groups described for R ¹ .
[0016]
Specific examples of the substituent for R ¹ or Ar ^{1 to} Ar ⁵ include chlorine, bromine, iodine, halogen atoms of fluorine, methyl group, ethyl group, propyl group, butyl group, sec-butyl group, tert- Substituted or unsubstituted alkyl groups such as butyl group, pentyl group, hexyl group, heptyl group, octyl group, stearyl group, trichloromethyl group, phenyl group, naphthyl group, 3-methylphenyl group, 3-methoxyphenyl group, 3-fluoro Substituted or unsubstituted aryl groups such as phenyl group, 3-trichloromethylphenyl group, 3-trifluoromethylphenyl group, and 3-nitrophenyl group, toxyl group, n-butoxy group, tert-butoxy group, trichloromethoxy group, trifluoro Ethoxy group, pentafluoropropoxy group, 2,2,3,3-tetrafluoropropo group Substituted or unsubstituted alkoxy groups such as xoxy group, 1,1,1,3,3,3-hexafluoro-2-propoxy group, 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, octylthio group, substituted or unsubstituted alkylthio group such as trifluoromethylthio group, phenylthio group, p-nitrophenylthio group, p-tert-butylphenylthio group, 3-fluorophenylthio group, pentafluorophenylthio Group, 3-trifluoromethylphenylthio group Mono- or di-substituted such as substituted or unsubstituted arylthio group, cyano group, nitro group, amino group, methylamino group, diethylamino group, ethylamino group, diethylamino group, dipropylamino group, dibutylamino group, diphenylamino group Acyl groups such as amino group, bis (acetoxymethyl) amino group, bis (acetoxyethyl) amino group, bisacetoxypropyl) amino group, bis (acetoxybutyl) amino group, hydroxyl group, siloxy group, acyl group, methylcarbamoyl group, Carbamoyl groups such as dimethylcarbamoyl group, ethylcarbamoyl group, diethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, phenylcarbamoyl group, carboxylic acid group, sulfonic acid group, imide group, cyclopentane group, cyclohexyl group, etc. Cycloalkyl group, phenyl group, tolyl group, naphthyl group, biphenyl group, o, m, p-terphenyl group, anthranyl group, phenanthrenyl group, fluorenyl group, 9-phenylanthranyl group, 9,10-diphenylanthranyl group, pyrenyl Aryl groups such as groups, pyrrole groups, pyrroline groups, pyrazole groups, pyrazoline groups, imidazole groups, triazole groups, pyridine groups, pyridazine groups, pyrimidine groups, pyrazine groups, triazine groups, indole groups, purine groups, quinoline groups, isoquinoline groups , Sinoline group, quinoxaline group, benzoquinoline group, fluorenone group, dicyanofluorene group, carbazole group, oxazole group, oxadiazole group, thiazole group, thiadiazole group, triazole group, imidazole group, benzoxazole group, benzo Thiazole group, benzotriazole group, benzimidazole group, bisbenzoxazole group, bisbenzothiazole group, bisbenzimidazole group, anthrone group, dibenzofuran group, dibenzothiophene group, anthraquinone group, acridone group, phenothiazine group, pyrrolidine group, dioxane group And heterocyclic groups such as a piperidine group, a morpholine group, and a piperazine group.
[0017]
In the present invention, the compound represented by the general formula [1] can be produced, for example, by the following method.
[0018]
By reacting the compound represented by the following general formula [2] with the trialkyl phosphite or triphenyl phosphite represented by the following general formula [3], the compound of the general formula [4] can be produced.
[0019]
General formula [2-4]
[Chemical 3]
[Wherein, X represents a halogen atom of fluorine, chlorine, bromine or iodine, and R ² represents an alkyl group such as a methyl group, an ethyl group or an isopropyl group, or an aryl group such as a phenyl group or a naphthyl group. X ¹ , X ² , X ³ , Z, and Ar ^{1 to} Ar ⁵ are the same as described above. ]
[0020]
The compound represented by the general formula [1] can be obtained by reacting the obtained compound represented by the general formula [4] with a ketone or aldehyde represented by the following general formula [5] in the presence of a base. As the reaction solvent used here, hydrocarbons, alcohols, and ethers are used. Specific examples include methanol, ethanol, isopropanol, 2-methoxyethanol, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, dioxane, tetrahydrofuran, toluene, xylene, dimethyl sulfoxide, N, N-dimethylformamide. N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Examples of the base include sodium hydroxide, potassium hydroxide, sodium amide, sodium hydride, n-butyllithium, sodium methylate, and potassium t-butoxide. Among them, sodium methylate and potassium t -An alcoholate such as butoxide is preferred. The reaction temperature cannot be uniquely determined depending on the type and conditions of the reaction raw material to be used, but usually a wide range from room temperature to about 100 ° C. can be selected, and room temperature is particularly preferred.
[0021]
General formula [5]
[Formula 4]
[Wherein Ar ³ and Ar ⁴ are the same as defined above. ]
[0022]
The compound represented by the general formula [1] is obtained by reacting an aldehyde or ketone represented by the following general formula [6] with a phosphonic acid ester represented by the following general formula [7] in the presence of a base. Can also be obtained. The reaction conditions at this time are the same as described above.
[0023]
General formula [6-7]
[Chemical formula 5]
[X ¹ , X ² , X ³ , Z, Ar ^{1 to} Ar ⁵ and R ² are the same as described above. ]
[0024]
Specific examples of the compounds of the present invention are specifically shown in Table 2 below, but the present invention is not limited to the following representative examples.
[0027]
[Table 2]
[0028]
[0029]
[0030]
[0031]
[0032]
[0035]
The compound represented by the general formula [1] has two olefin sites (> C = C <) in one molecule. Depending on the geometric isomer of the olefin moiety, the compound represented by the general formula [1] has a combination of a cis isomer and a trans isomer, but the compound of the present invention may be either of them or a mixture thereof. Good.
[0036]
An organic EL element is an element in which a single-layer or multilayer 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 contain a hole injecting material or an electron injecting material in addition to transporting holes injected from the anode or electrons injected from the cathode to the light emitting material. The multilayer type is a multilayer of (anode / hole injection layer / light emitting layer / cathode), (anode / light emitting layer / electron injection layer / cathode), and (anode / hole injection layer / light emitting layer / electron injection layer / cathode). There are organic EL elements stacked in a configuration. Since the compound represented by the general formula [1] of the present invention is a compound having strong fluorescence in a solid state and excellent in electroluminescence, it can be used as a light emitting material in a light emitting layer. Moreover, since the compound of general formula [1] can transport carriers such as holes or electrons, it can also be used for a hole injection layer or an electron injection layer of an organic EL device.
[0037]
By making the organic EL element have a multi-layer structure, it is possible to prevent a decrease in luminance and lifetime due to quenching. Further, if necessary in each layer, a light emitting material, a doping material, a hole injecting material for transporting carriers, and an electron injecting material can be used in combination. In addition, a light emitting layer can be doped with a doping material to improve light emission luminance and light emission efficiency, and light emission of other colors can be obtained with the doping material. In addition, the hole injection layer, the light emitting layer, and the electron injection layer may each be formed of two or more layers, and there is an element structure in which holes or electrons are efficiently injected from the electrode and transported in the layer. Selected.
[0038]
Examples of the light emitting material or doping material that can be used for the light emitting layer include anthracene, naphthalene, phenanthrene, pyrene, tetracene, coronene, chrysene, fluorescein, perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone, naphthaloperinone, diphenylbutadiene, tetraphenylbutadiene, coumarin, Oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, pyrazine, cyclopentadiene, triphenylamine, benzidine type triphenylamine, styrylamine type triphenylaminediamine type triphenylamine pyran, quinoline metal complex, aminoquinoline metal complex, Imine, diphenylethylene, vinylanthracene, diaminocarbazole, pyran, thiopyran, polymethine, Cyanine, imidazole chelated oxinoid compounds, quinacridone, phthalocyanine, and rubrene and have their derivatives, are not limited thereto.
[0039]
As the conductive material used for the anode, those having a work function larger than 4 eV are suitable. Metals such as Au, Pt, Ag, Cu, and Al, metal alloys, organic materials such as ITO, NESA, polythiophene, and polypyrrole. A conductive resin is used.
[0040]
As the conductive material used for the cathode, a material having a work function smaller than 4 eV is suitable. Examples of the material include metals such as Al, In, Mg, Li, and Ca, and alloys such as Mg / Ag, Li / Al, and Mg / In. If necessary, the anode and the cathode may be formed of two or more layers. The anode and the cathode are produced by a known film forming method such as vapor deposition, sputtering, ion plating, plasma gun or the like.
[0041]
In the organic EL device, in order to efficiently emit light, it is desirable that at least one of the anode and the cathode is sufficiently transparent in the light emission wavelength region of the device. The substrate is also preferably transparent. The transparent electrode is set so as to ensure a predetermined translucency by a method such as vapor deposition, sputtering, or ion plating using the above-described conductive material. The electrode on the light emitting surface desirably has a light transmittance of 10% or more.
[0042]
The substrate may be any material that has mechanical and thermal strength and is transparent, but examples thereof include a glass substrate, a plate or film such as polyethylene, polyethersulfone, polypropylene, and polyimide.
[0043]
For the formation of each layer of the organic EL device of the present invention, any of dry deposition methods such as vacuum deposition, sputtering, ion plating and plasma gun, and wet deposition 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 or the like are generated in the thin film, and sufficient light emission luminance cannot be obtained even when an electric field is applied. The normal film thickness is suitably in the range of 5 nm to 10 μm, but more preferably in the range of 10 nm to 0.2 μm.
[0044]
In the case of the wet film-forming method, the material for forming each layer is dissolved or dispersed in a solvent such as chloroform, tetrahydrofuran, or dioxane to form a thin film, and any solvent may be used. In any organic layer, an appropriate resin or additive is used for improving film formability and preventing pinholes in the film. Examples of such resins include insulating resins such as polystyrene, polycarbonate, polyarylate, polyester, polyamide, polyurethane, polysulfone, polymethyl methacrylate, polymethyl acrylate, and cellulose, and photoconductivity such as poly-N-vinylcarbazole and polysilane. Examples thereof include conductive resins such as conductive resins, polythiophene, and polypyrrole. Examples of the additive include an antioxidant, an ultraviolet absorber, and a plasticizer.
[0045]
As a hole injection material, it has the ability to transport holes, has an excellent hole injection effect on the light emitting layer or light emitting material, and is an electron injection layer or electron transport material for excitons generated in the light emitting layer. And a compound having an excellent ability to form a thin film. Specifically, phthalocyanine, naphthalocyanine, porphyrin, oxadiazole, triazole, imidazole, imidazolone, imidazolethione, pyrazoline, pyrazolone, tetrahydroimidazole, oxazole, oxadiazole, hydrazone, acylhydrazone, polyarylalkane, stilbene, butadiene Benzidine-type triphenylamine, styrylamine-type triphenylamine, diamine-type triphenylamine, and their derivatives, and polymer materials such as polyvinylcarbazole, polysilane, and conductive polymers. It is not something.
[0046]
The electron injecting material has the ability to transport electrons, has an excellent electron injecting effect on the light emitting layer or light emitting material, and excitons generated in the light emitting layer are injected into the hole injecting layer or hole transporting material. Examples thereof include compounds that prevent migration and have excellent thin film forming ability. For example, there are fluorenone, anthraquinodimethane, diphenoquinone, thiopyran dioxide, oxadiazole, thiadiazole, tetrazole, perylenetetracarboxylic acid, fluorenylidenemethane, anthraquinodimethane, anthrone, and their derivatives. It is not limited to. Further, sensitization can be performed by adding an electron accepting material to the hole injecting material and an electron donating material to the electron injecting material.
[0047]
In order to improve the stability of the organic EL device obtained by the present invention with respect to temperature, humidity, atmosphere, etc., a protective layer may be provided on the surface of the device, or silicon oil or the like may be sealed to protect the entire device. Is possible.
[0048]
【Example】
Hereinafter, the present invention will be described in more detail based on examples.
Synthesis method of compound (1) (reference synthesis example)
Compound (1)
[Chemical 6]
In a flask, 24.7 g of α-diphenylbromomethane and 16.6 g of triethyl phosphite are added and stirred at 150 ° C. for 3 hours. The reaction solution is concentrated under reduced pressure, 400 g of n-hexane is added, and then cooled overnight at 5 ° C. to precipitate crystals. The obtained crystals were filtered and dried to obtain 22.7 g of a phosphate ester represented by the following chemical structure. Then, 16.3 g of the phosphoric acid ester synthesized as described above, 50 g of 2,5-di (4-formylphenyl) -thiophene, 18.5 g of potassium t-butoxide, and 150 g of N, N-dimethylformamide were placed in the flask. Stir at 40 ° C. for 5 hours. After cooling, it was washed in order with ethanol and purified water, filtered, and then purified using a silica gel column to obtain 20 g of a yellowish white powder. As a result of performing infrared absorption spectrum, NMR spectrum, and mass spectrometry analysis of this powder, it was confirmed to be compound (1).
[0049]
[Chemical 6]
[0052]
Example 16
N, N '-(3-methylphenyl) -N, N'-diphenyl-1,1-biphenyl-4,4-diamine (TPD) is vacuum-deposited on the cleaned glass plate with an ITO electrode to form a film. A hole injection layer having a thickness of 20 nm was obtained. Subsequently, the compound (16) was vapor-deposited to produce a light-emitting layer having a thickness of 40 nm, and a tris (8-hydroxyquinoline) aluminum complex was vapor-deposited to obtain an electron injection layer having a thickness of 30 nm. On top of that, an electrode having a thickness of 100 nm was formed from 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 emitted light with a direct current voltage of 5V and an emission luminance of 320 (cd / m ² ), a maximum emission luminance of 12000 (cd / m ² ), and a luminous efficiency of 1.4 (lm / W) at 5V. Next, as a result of a life test in which the device was continuously emitted at a current density of 3 (mA / cm ² ), emission of 1/2 or more of the initial luminance was maintained for 5000 hours or more.
[0053]
Examples 17, 19, 22, 28-34, 39, 40
An organic EL device was produced in the same manner as in Example 16 except that the compounds shown in Table 3 were used for the light emitting layer. This device exhibited the light emission characteristics shown in Table 3.
[0054]
[Table 3]
[0055]
[0065]
【The invention's effect】
According to the present invention, it was possible to obtain an organic EL device having higher luminous efficiency and higher luminance than the conventional one and having a long lifetime.

Claims (3)

An organic electroluminescence element material represented by the following general formula [1].
General formula [1]
[Wherein, X ^{1 to} X ³ each independently represent N, CH, or a carbon atom bonded to Ar ¹ or Ar ² , provided that at least one of X ^{1 to} X ³ is bonded to Ar ¹ or Ar ² . Represents a carbon atom. Z represents S or N—R ¹ . R ¹ represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group. Ar ¹ and Ar ² each independently represent a substituted or unsubstituted arylene group. Ar ^{3 to} Ar ⁵ are each independently a hydrogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group Represents. m or n represents an integer of 0 to 4, but m + n = 0 does not occur.
However,
Is
One of them. ] The organic electroluminescent element in which at least one layer is a layer containing the organic electroluminescent element material according to claim 1, wherein a plurality of organic compound thin films including a light emitting layer are formed between a pair of electrodes. The organic electroluminescent element which formed the organic compound thin film of the multiple layer containing a light emitting layer between a pair of electrodes, and this light emitting layer is a layer containing the organic electroluminescent element material of Claim 1.