JP4961540B2 - COMPOUND, COMPOSITION FOR ORGANIC ELECTROLUMINESCENT DEVICE AND ORGANIC ELECTROLUMINESCENT DEVICE - Google Patents

Description

  The present invention relates to a triphenylamine compound useful as a material for an organic electroluminescence device, a composition containing the compound, and an organic electroluminescence device formed using the composition.

  Organic electroluminescent elements (hereinafter also simply referred to as “organic EL elements”) can be driven by a DC voltage, are self-luminous elements, have a wide viewing angle, high visibility, and response speed. Has excellent characteristics such as being fast. Therefore, it is expected as a next-generation display element, and research is actively conducted.

  As such an organic EL device, a single layer structure in which a light emitting layer made of an organic material is formed between an anode and a cathode, a device having a hole transport layer between an anode and a light emitting layer, a cathode A multilayer structure such as one having an electron transport layer between the light emitting layer and the light emitting layer is known. All of these organic EL devices emit light by recombination of electrons injected from the cathode and holes injected from the anode in the light emitting layer.

  In the organic EL element, the light emitting layer is required to have high luminous efficiency. Recently, in order to realize high luminous efficiency, an attempt has been made to use energy of triplet state molecules as an excited state for light emission of the organic EL element.

  According to the organic EL element having such a configuration, it has been reported that an external quantum efficiency of 8% is obtained which exceeds 5% which has been conventionally considered as a limit value of the external quantum efficiency of the organic EL element. (For example, refer nonpatent literature 1 and nonpatent literature 2.).

  However, this organic EL element is made of a low molecular weight material and is formed by a dry method such as a vapor deposition method. For this reason, there is a limit in forming a layer having a large area by this dry method, and there is a problem that it is difficult to apply to a large screen display device, for example.

In order to solve this problem, for example, a light emitting layer made of a composition made of an iridium complex compound and polyvinyl carbazole is formed by a wet method as an organic EL element made of a polymer material using energy such as triplet state molecules. Have been proposed (see, for example, Non-Patent Document 1). However, this organic EL device has a drawback of a short service life.
“Applied Physics Letters”, 1999, vol. 75, p. 4 “Chemical Materials”, 2004, Vol. 16, p. 1285

  The present invention has been made based on the above circumstances, and provides a compound excellent in solubility in a solvent, capable of easily forming a thin film, and suitable as a material for an organic electroluminescence element. With the goal.

Another object of the present invention is to provide a composition for an organic electroluminescence device, and an organic electroluminescence device formed using the composition and having excellent light emission characteristics and service life.

The present inventors diligently studied about the above problem. As a result, it has been found that the above problem can be solved by using a specific triphenylamine compound.
That is, the triphenylamine compound of the present invention is represented by the following general formula (1).

In the formula, R ¹ and R ² may be the same or different and are a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
The composition for organic electroluminescent elements of the present invention comprises the above triphenylamine compound, a triplet light-emitting metal complex compound, and a solvent.

The triplet light-emitting metal complex compound is preferably a complex compound of iridium and a nitrogen atom-containing aromatic compound.
The organic electroluminescent element of this invention has a light emitting layer formed using the said composition for organic electroluminescent elements.

  The triphenylamine compound of the present invention is suitable as a material for an organic electroluminescence device because it has excellent solubility in a solvent, can easily form a thin film, and has good carrier transportability.

  Moreover, since the composition for organic electroluminescent elements of the present invention contains the above triphenylamine compound and triplet luminescent metal complex compound, it forms an organic electroluminescent element having excellent luminescent properties and service life. Can do.

  Furthermore, since the organic electroluminescent element of the present invention uses the composition for an organic electroluminescent element as a material for the light emitting layer, the organic electroluminescent element is excellent in light emission characteristics and service life due to triplet light emission.

  The triphenylamine compound of the present invention, a composition for an organic electroluminescence device containing the compound, and an organic electroluminescence device formed using the composition will be described in detail below.

<Triphenylamine compound>
The compound represented by the above formula (1) (hereinafter also referred to as “triphenylamine compound (1)”) is suitable as a material for an organic electroluminescence element.

In the above formula (1), R ¹ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or 6 carbon atoms.
˜20 aryl groups. Of these, a hydrogen atom and a methyl group are preferable.
Preferable examples of the triphenylamine compound (1) include compounds represented by the following formulas (1-1) to (1-7) (hereinafter, for example, represented by the formula (1-1)). The compound is simply referred to as “triphenylamine compound (1-1)”).

  The triphenylamine compound (1) can be produced by a method as shown in the following reaction formula.

  The triphenylamine compound (1) can form a film by a dry method such as a vapor deposition method. However, since it has excellent solubility in a solvent, a coating solution for forming a thin film can be easily prepared and applied. A thin film can be easily formed with a liquid.

  Moreover, since the said triphenylamine compound (1) has favorable carrier transportability, it combines with the luminescent material which has phosphorescence, for example as a material which comprises the light emitting layer of an organic EL element. It can be used suitably.

<Composition for organic EL device>
The composition for organic EL devices of the present invention comprises a component comprising the above triphenylamine compound (1) (hereinafter also referred to as “triphenylamine component”) and a component comprising a triplet luminescent metal complex compound (hereinafter referred to as “complex component”). And a solvent.

  Examples of the triplet light-emitting metal complex compound constituting the complex component include iridium complex compounds, platinum complex compounds, palladium complex compounds, rubidium complex compounds, osmium complex compounds, and rhenium complex compounds. Of these, iridium complex compounds are preferred.

  Examples of the iridium complex compound constituting the complex component include iridium, phenylpyridine, phenylpyrimidine, bipyridyl, 1-phenylpyrazole, 2-phenylquinoline, 2-phenylbenzothiazole, 2-phenyl-2-oxazoline, 2,4- A complex compound with a nitrogen atom-containing aromatic compound such as diphenyl-1,3,4-oxadiazole, 5-phenyl-2- (4-pyridyl) -1,3,4-oxadiazole or a derivative thereof; Can be mentioned.

  Examples of such iridium complex compounds include compounds represented by the following general formulas (2) to (7).

In the above formulas (2) to (7), R ¹⁶ , R ¹⁷ and R ¹⁸ each represent 1 to 20 alkyl groups, fluorine atoms or trifluoromethyl groups, and may be the same or different from each other. There may be. x is an integer of 0 to 4, and y is an integer of 0 to 4.

Examples of the alkyl group in the above substituted R ¹⁶ , R ¹⁷ and R ¹⁸ include methyl group, ethyl group, isopropyl group, t-butyl group, n-butyl group, isobutyl group, hexyl group and octyl group. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group.

Among the above, it is particularly preferable to use an iridium complex compound represented by the general formula (2) (hereinafter also referred to as “iridium complex compound (2)”).
Content of the complex component in the composition for organic EL elements of this invention is 0.1-30 mass parts with respect to 100 mass parts of triphenylamine components, Preferably it is 0.5-10 mass parts. When the content of the complex component is too small, it may be difficult to obtain sufficient light emission. On the other hand, when the content of the complex component is excessive, a phenomenon called concentration quenching, which is a decrease in luminous efficiency, may occur.

  If necessary, an additive such as a charge transporting compound can be added to the composition for an organic EL device of the present invention. Examples of the charge transporting compound include compounds having charge transporting properties represented by the following formulas (A-1) to (A-10), and electrons represented by the following formulas (A-1) to (A-20). Examples thereof include compounds having a transport property and compounds having a hole transport property represented by the following formulas (U-1) to (U-34).

  In the above formula (A-16), Y represents any of the groups represented by the following formulas (a) to (c).

    In the above formula (U-12), q represents an integer of 1 or more.

  The addition amount of the charge transporting compound in the composition for organic EL devices of the present invention is 0 to 500 parts by weight, preferably 0 to 100 parts by weight, and more preferably 0 to 50 parts by weight with respect to 100 parts by weight of the triphenylamine component. Part by mass.

The composition for organic EL elements of the present invention is usually prepared as a composition solution by dissolving a triphenylamine component and a complex component made of the above triphenylamine compound (1) in an organic solvent. Then, the composition solution is applied to the surface of the substrate on which the light emitting layer is to be formed, and the resulting coating film is subjected to a removal treatment with an organic solvent, thereby forming a light emitting layer in the organic EL element. it can. Examples of means for applying the composition solution include spin coating, dipping, roll coating, ink jet, and printing.

  Here, the organic solvent for preparing the composition solution is not particularly limited as long as it can dissolve the triphenylamine component and the complex component. Specifically, aromatic hydrocarbon solvents such as anisole, toluene, xylene and mesitylene; halogenated hydrocarbon solvents such as chloroform, chlorobenzene, tetrachloroethane and o-dichlorobenzene; N, N-dimethylformamide, N, Amide solvents such as N-dimethylacetamide and 1-methyl-2-pyrrolidone; cyclohexanone, ethyl lactate, propylene glycol methyl ether acetate, ethyl ethoxypropionate, methyl amyl ketone and the like. These organic solvents may be used alone or in combination of two or more.

  As the organic solvent, an organic solvent having an appropriate evaporation rate, specifically, an organic solvent having a boiling point of about 70 to 200 ° C. is preferable because a thin film having a uniform thickness can be formed.

  The proportion of the organic solvent used varies depending on the types of the triphenylamine component and the complex component, but the proportion of the total concentration of the triphenylamine component and the complex component in the composition solution is usually 0.5 to 10% by mass. It is preferable that

  According to the composition for an organic EL device as described above, an organic EL device having a light emitting layer that emits light with sufficiently high luminance can be obtained, and the light emitting layer can be easily formed by a wet method such as an inkjet method. can do.

<Organic EL device>
FIG. 1 is an explanatory cross-sectional view showing an example of the configuration of the organic EL element of the present invention.
In FIG. 1, an organic EL element has an anode 2 as an electrode for supplying holes provided on a transparent substrate 1 by, for example, a transparent conductive film, and a hole injecting and transporting layer 3 provided on the anode 2. A light emitting layer 4 is provided on the hole injection transport layer 3, a hole blocking layer 8 is provided on the light emitting layer 4, and an electron injection layer 5 is provided on the hole blocking layer 8. There is provided a cathode 6 which is an electrode for supplying electrons. The anode 2 and the cathode 6 are electrically connected to a DC power source 7.

In such an organic EL element, as the transparent substrate 1, a glass substrate, a transparent resin substrate, a quartz glass substrate, or the like can be used.
As a material constituting the anode 2, a material having a high work function, for example, a transparent material having a work function of 4 eV or more is preferably used. Here, the work function refers to the minimum work required to extract electrons from a solid in a vacuum. As the anode 2, an ITO (Indium Tin Oxide) film, a tin oxide (SnO ₂ ) film, a copper oxide (CuO) film, a zinc oxide (ZnO) film, or the like can be used.

  The hole injection transport layer 3 is provided to efficiently supply holes to the light emitting layer 4 and has a function of receiving holes from the anode 2 and transporting them to the light emitting layer 4. . As a material constituting the hole injection / transport layer 3, for example, a charge injection / transport material such as poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate can be suitably used. Moreover, the thickness of the hole injection transport layer 3 is, for example, 10 to 200 nm.

The light emitting layer 4 has a function of combining electrons and holes and emitting the binding energy as light. In the organic EL device of the present invention, the light emitting layer 4 is formed using the composition for organic EL devices. Although the thickness of the light emitting layer 4 is not specifically limited, Usually, 5-20.
It is selected in the range of 0 nm.

  The hole blocking layer 8 suppresses intrusion of holes supplied to the light emitting layer 4 through the hole injecting and transporting layer 3 into the electron injecting layer 5, and recombines holes and electrons in the light emitting layer 4. It has a function of promoting and improving luminous efficiency. Moreover, the thickness of the hole block layer 8 is 10-30 nm, for example.

  Examples of the material constituting the hole blocking layer 8 include 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (basocuproin: BCP) represented by the following formula (I) and the following formula (II) 1,3,5-tri (phenyl-2-benzimidazolyl) benzene (TPBI) represented by

  The electron injection layer 5 has a function of transporting electrons received from the cathode 6 to the light emitting layer 4 through the hole blocking layer 8. The material constituting the electron injection layer 5 includes a co-evaporation system (BCP, Cs) of a bathophenanthroline-based material and cesium, an alkali metal and a compound thereof (for example, lithium fluoride and lithium oxide), an alkaline earth metal, and Such compounds (for example, magnesium fluoride and strontium fluoride) can be used. The electron injection layer 5 has a thickness of, for example, 0.1 to 100 nm.

  As a material constituting the cathode 6, a material having a low work function, for example, a material having a work function of 4 eV or less is used. As a specific example of the cathode 6, a metal film made of aluminum, calcium, magnesium, indium, or the like, or an alloy film of these metals can be used. Although the thickness of the cathode 6 changes with kinds of material, it is 10-1000 nm normally, Preferably it is 50-200 nm.

The organic EL element of the present invention is manufactured, for example, as follows.
First, the anode 2 is formed on the transparent substrate 1. As a method of forming the anode 2, a vacuum deposition method, a sputtering method, or the like can be used. A commercially available material in which a transparent conductive film such as an ITO film is formed on the surface of a transparent substrate such as a glass substrate can also be used.

  A hole injection transport layer 3 is formed on the anode 2 formed as described above. As a method for forming the hole injecting and transporting layer 3, for example, a hole injecting and transporting layer forming liquid is prepared by dissolving a charge injecting and transporting material in an appropriate solvent. The hole injecting and transporting layer 3 can be formed by applying to the surface of 2 and subjecting the obtained coating film to a solvent removal treatment.

  Next, the composition for organic EL device of the present invention is used as a light emitting layer forming liquid, this light emitting layer forming liquid is applied onto the hole injecting and transporting layer 3, and the obtained coating film is heat-treated, whereby the light emitting layer 4 is obtained. Form. As a method for applying the light emitting layer forming liquid, a spin coating method, a dip method, a roll coating method, an ink jet method, a printing method, or the like can be used.

  A hole block layer 8 is formed on the light emitting layer 4 formed as described above, an electron injection layer 5 is formed on the hole block layer 8, and a cathode 6 is formed on the electron injection layer 5. Thus, an organic EL element having the configuration shown in FIG. 1 is obtained. In addition, as a method for forming the hole block layer 8, the electron injection layer 5, and the cathode 6, a dry method such as a vacuum deposition method can be used.

  In the organic EL element, when a DC voltage is applied between the anode 2 and the cathode 6 by the DC power source 7, the light emitting layer 4 emits light, and this light is emitted from the hole injection transport layer 3, the anode 2 and the transparent substrate 1. Radiated to the outside via

  According to the organic EL element having the above-described configuration, since the light emitting layer 4 is formed of the composition for organic EL elements of the present invention, high light emission luminance and light emission efficiency can be obtained. Further, since the hole blocking layer 8 is provided, the coupling between the holes from the anode 2 and the electrons from the cathode 6 is realized with high efficiency, and as a result, high emission luminance and luminous efficiency can be obtained. .

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples at all.

  [Synthesis Example 1] Synthesis of phenylimidazole compound (i-1)

  In a 50 ml round bottom flask, 4.389 g of 4-bromobenzoyl chloride and 3.684 g of N-phenyl-o-phenylenediamine were weighed and dissolved in 30 ml of N, N-dimethylformamide (DMF) under a nitrogen atmosphere. Stir at room temperature for 15 hours. After completion of the reaction, the reaction solution was poured into 500 ml of water, the resulting precipitate was filtered, and further washed thoroughly with water. The obtained compound was purified by recrystallization using N, N-dimethylformamide / methanol to obtain 4.410 g of 4-bromo-N- [2- (phenylamino) phenyl] benzamide.

  Subsequently, 2.200 g of 4-bromo-N- [2- (phenylamino) phenyl] benzamide and 30 g of polyphosphoric acid were weighed into a 50 ml round bottom flask and stirred at 160 ° C. for 12 hours in a nitrogen atmosphere. After completion of the stirring, the reaction solution was poured into 500 ml of water, and the resulting precipitate was filtered and further washed thoroughly with water. The obtained compound was purified by recrystallization using methanol to obtain 1.670 g of yellow 2- (4-bromophenyl) -1-phenyl-1H-benzimidazole.

  Subsequently, 2.100 g of 2- (4-bromophenyl) -1-phenyl-1H-benzimidazole was weighed into a 50 ml three-necked flask and dissolved in 25 ml of tetrahydrofuran under an argon atmosphere. After placing the flask in a −78 ° C. cool bath, 4.50 ml of n-butyllithium was added dropwise to the reaction solution over 2 hours. The reaction solution was stirred at −78 ° C. for 1 hour, and then the reaction temperature was raised to −50 ° C. and further stirred for 1 hour. Again, after adjusting to −78 ° C., 2 ml of trimethyl boronate was added dropwise to the reaction solution over 1 hour. The reaction solution was stirred overnight, and then slowly raised to room temperature. After completion of the reaction, the reaction solution was poured into acidic water (water: hydrochloric acid = 100 ml: 20 ml) and stirred at room temperature for 5 hours. Subsequently, diethyl ether was added for extraction, and the organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. Next, the obtained solid was boiled and washed with hexane to obtain 1.510 g of yellow 4- (1-phenyl-1H-benzimidazol-2-yl) phenylboronic acid (phenylimidazole compound (i-1)). Obtained.

  [Example 1] Synthesis of triphenylamine compound (1-1)

  Next, in a 50 ml round bottom flask, 0.700 g of the phenylimidazole compound (i-1) obtained in Synthesis Example 1, 0.318 g of tris- (4-bromophenyl) amine, 3.3 ml of 2 mol / l potassium carbonate aqueous solution. Then, 0.022 g of tetrakis (triphenylphosphine) palladium was weighed out and dissolved in 25 ml of tetrahydrofuran under an argon atmosphere, followed by heating under reflux for 48 hours. After completion of the reaction, dichloromethane was added to the reaction solution for extraction. The organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. The resulting compound was purified by column chromatography using dichloromethane / diethyl ether (v / v, 10/1) as an eluent, and 0.310 g of the target triphenylamine compound (1-1) was obtained. Obtained.

The obtained triphenylamine compound (1-1) was subjected to spectrum measurement by ¹ H-NMR and ¹³ C-NMR, and confirmed to be a compound having triphenylamine having an N-phenylimidazole group as a basic skeleton. . The ¹ H-NMR spectrum of the obtained triphenylamine compound (1-1) is shown in FIG. 2, and the ¹³ C-NMR spectrum is shown in FIG.

  [Synthesis Example 2] Synthesis of triphenylamine compound (i-4)

After weighing 100.000 g of 4-bromo-3-methylbenzoic acid into a 100 ml round bottom flask, 70 ml of thionyl chloride and 2 drops of pyridine were added and heated under reflux for 12 hours. After completion of the reaction, excess thionyl chloride was distilled off under reduced pressure to obtain 9.400 g of white 4-bromo-3methylbenzoyl chloride.

  In a 50 ml round bottom flask, 6.433 g of 4-bromo-3-methylbenzoyl chloride and 5.078 g of N-phenyl-o-phenylenediamine were weighed and dissolved in 40 ml of N, N-dimethylformamide under a nitrogen atmosphere. And stirred at room temperature for 15 hours. After completion of the reaction, the reaction solution was poured into 500 ml of water, the resulting precipitate was filtered, and further washed thoroughly with water. The resulting compound was purified by recrystallization using N, N-dimethylformamide / methanol, and 7.880 g of 4-bromo-3-methyl-N- [2- (phenylamino) phenyl] benzamide (BPBA). Got.

  Next, 5.000 g of 4-bromo-3-methyl-N- [2- (phenylamino) phenyl] benzamide (BPBA) and 70 g of polyphosphoric acid (PPA) were weighed into a 50 ml round bottom flask, and 160 ° C. under a nitrogen atmosphere. For 12 hours. After completion of the stirring, the reaction solution was poured into 800 ml of water, and the resulting precipitate was filtered and further washed thoroughly with water. The obtained compound was purified by recrystallization using methanol to obtain 3.900 g of yellow 2- (4-bromo-3-methylphenyl) -1-phenyl-1H-benzimidazole.

  Subsequently, 5.158 g of 2- (4-bromo-3-methylphenyl) -1-phenyl-1H-benzimidazole was weighed into a 200 ml three-necked flask and dissolved in 100 ml of tetrahydrofuran under an argon atmosphere. After placing the flask in a −78 ° C. cool bath, 4.73 ml of n-butyllithium was added dropwise to the reaction solution over 2 hours. The reaction solution was stirred at −78 ° C. for 1 hour, and then the reaction temperature was raised to −50 ° C. and further stirred for 1 hour. The reaction solution was again lowered to −78 ° C., and 4.73 ml of trimethyl boronate was added dropwise over 2 hours. The reaction solution was stirred overnight, and then slowly raised to room temperature. After completion of the reaction, the reaction solution was poured into acidic water (water: hydrochloric acid = 200 ml: 40 ml) and stirred at room temperature for 5 hours. Subsequently, diethyl ether was added for extraction, and the organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. Subsequently, the obtained solid was boiled and washed with hexane to give yellow 2-methyl-4- (1-phenyl-1H-benzimidazol-2-yl) phenylboronic acid (phenylimidazole compound (i-4)). 3.860 g was obtained.

  [Example 2] Synthesis of triphenylamine compound (1-4)

  In a 50 ml round bottom flask, 1.970 g of phenylimidazole compound (i-4) obtained in Synthesis Example 2, 0.723 g of tris- (4-bromophenyl) amine, 7.5 ml of 2 mol / l aqueous potassium carbonate solution and tetrakis ( 0.052 g of triphenylphosphine) palladium was weighed and dissolved in 35 ml of tetrahydrofuran under an argon atmosphere, and then heated to reflux for 48 hours. After completion of the reaction, dichloromethane was added to the reaction solution for extraction. The organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. The resulting compound was purified by column chromatography using dichloromethane / diethyl ether (v / v, 10/1) as an eluent, and 0.820 g of the target triphenylamine compound (1-4) was obtained. Obtained.

The obtained triphenylamine compound (1-4) was subjected to spectrum measurement by ¹ H-NMR and ¹³ C-NMR, and confirmed to be a compound having triphenylamine having an N-phenylimidazole group as a basic skeleton. . FIG. 4 shows the ¹ H-NMR spectrum of the obtained triphenylamine compound (1-4), and FIG. 5 shows the ¹³ C-NMR spectrum.

  [Synthesis Example 3] Synthesis of phenylimidazole compound (i-2)

In a 50 ml round-bottomed flask, weigh out 5.4865 g of 3-bromobenzoyl chloride and 4.606 g of N-phenyl-o-phenylenediamine and dissolve them in 40 ml of N, N-dimethylformamide under a nitrogen atmosphere. Stir for 15 hours. After completion of the reaction, the reaction solution was poured into 600 ml of water, the resulting precipitate was filtered, and further washed thoroughly with water. The obtained compound was purified by recrystallization using tetrahydrofuran / methanol to obtain 5.510 g of 3-bromo-N- [2- (phenylamino) phenyl] benzamide (BPBA).

  Subsequently, 3.6724 g of 3-bromo-N- [2- (phenylamino) phenyl] benzamide (BPBA) and 45 g of polyphosphoric acid were weighed into a 50 ml round bottom flask and stirred at 160 ° C. for 12 hours in a nitrogen atmosphere. After completion of the stirring, the reaction solution was poured into 500 ml of water, and the resulting precipitate was filtered and further washed thoroughly with water. The obtained compound was purified by recrystallization using methanol to obtain 2.62 g of yellow 2- (3-bromophenyl) -1-phenyl-1H-benzimidazole.

  Subsequently, 1.046 g of 2- (3-bromophenyl) -1-phenyl-1H-benzimidazole, 0.8380 g of bis (pinacolato) diboron, 0.8833 g of potassium acetate and 1,1-bis (( 0.073 g of diphenylphosphino) ferrocene) palladium (II) dichloride was weighed out and dissolved in 18 ml of dimethyl sulfoxide under an argon atmosphere and stirred at 80 ° C. for 6 hours. Next, the reaction solution was extracted with ethyl acetate, and the organic layer was dried over anhydrous sodium sulfate. The obtained compound was purified by column chromatography using ethyl acetate / hexane (v / v, 1/3) as an eluent, and the desired product 3- (1-phenyl-1H-benzimidazole-2) was obtained. -Il) -1- (4,4,5,5-tetramethyl-1,3,2-dioxaboron-2-yl) benzene (phenylimidazole compound (i-2) white powder 1.07 g was obtained.

  [Example 3] Synthesis of triphenylamine compound (1-2)

  In a 50 ml round bottom flask, 1.020 g of phenylimidazole compound (i-2) obtained in Synthesis Example 2, 0.3753 g of tris- (4-bromophenyl) amine, 3.85 ml of 2 mol / l aqueous potassium carbonate solution and tetrakis ( 0.0356 g of triphenylphosphine) palladium was weighed out and dissolved in 20 ml of tetrahydrofuran under an argon atmosphere, followed by heating under reflux for 48 hours. After completion of the reaction, dichloromethane was added to the reaction solution for extraction. The organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. The obtained compound was purified by column chromatography using dichloromethane / diethyl ether (v / v, 10/1) as an eluent, and 0.40 g of the target triphenylamine compound (1-2) was obtained. Obtained.

The obtained triphenylamine compound (1-2) was subjected to spectrum measurement by ¹ H-NMR and ¹³ C-NMR, and confirmed to be a compound having a triphenylamine having an N-phenylimidazole group as a basic skeleton. . FIG. 6 shows the ¹ H-NMR spectrum of the obtained triphenylamine compound (1-2), and FIG. 7 shows the ¹³ C-NMR spectrum.

  [Synthesis Example 4] Synthesis of triphenylamine raw material compound (ii-5)

  To a 50 mL round bottom flask equipped with a Dean-Stark tube and a nitrogen inlet tube was added 15.2620 g of 3-iodotoluene, 2.6788 g of 3-toluidine, 0.1952 g of bipyridyl, 16.8333 g of potassium hydroxide, 0.179 g of copper bromide and 20 mL of decane was added and refluxed. The reaction solution was extracted with methylene chloride and purified by column chromatography using hexane / ethyl acetate (v / v, 10/1) as an eluent to obtain 4.45 g of the desired product, tri-m-tolylamine. It was.

  Next, 1.100 g of tri-m-tolylamine was dissolved in 20 mL of methylene chloride under nitrogen at −5 ° C. in a 50 mL flask. Next, 1.838 g of bromine was added dropwise over 30 minutes, and the mixture was stirred as it was for 30 minutes. After removing the solvent, 50 mL of methanol was added and refluxed for 1 hour. The obtained compound was recrystallized from methanol / tetrahydrofuran to obtain 0.70 g of tris (4-bromo-3-methylphenyl) amine (triphenylamine raw material (ii-5)).

  [Example 4] Synthesis of triphenylamine compound (1-5)

In a 50 mL flask, 1.900 g of phenylimidazole compound (i-1) obtained in Synthesis Example 1, 0.8984 g of triphenylamine raw material (ii-5) obtained in Synthesis Example 4, tetrakis (triphenylphosphine) palladium 0.079 g, 2M potassium carbonate 8.55 mL and 35 mL tetrahydrofuran 35 mL were added and refluxed in argon for 48 hours. After completion of the reaction, dichloromethane was added to the reaction solution for extraction. The organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. The obtained compound was purified by column chromatography using dichloromethane / diethyl ether (v / v, 10/1) as an eluent, and 0.99 g of the target triphenylamine compound (1-5) was obtained. Obtained. The obtained triphenylamine compound (1-5) was subjected to spectrum measurement by ¹ H-NMR and ¹³ C-NMR, and confirmed to be a compound having an N-phenylimidazole group-containing triphenylamine as a basic skeleton. . ¹ H- of the obtained triphenylamine compound (1-5)
The NMR spectrum is shown in FIG. 8, and the ¹³ C-NMR spectrum is shown in FIG.

  [Example 5] Synthesis of triphenylamine compound (1-6)

  In a 100 ml round bottom flask, 3.9629 g of phenylimidazole compound (i-2) obtained in Synthesis Example 3, 1.5414 g of triphenylamine raw material (ii-5) obtained in Synthesis Example 4, 2 mol / l potassium carbonate 14.7 ml of an aqueous solution and 0.1359 g of tetrakis (triphenylphosphine) palladium were weighed and dissolved in 60 ml of tetrahydrofuran under an argon atmosphere, followed by heating under reflux for 48 hours. After completion of the reaction, dichloromethane was added to the reaction solution for extraction. The organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. The resulting compound was purified by column chromatography using dichloromethane / tetrahydrofuran (v / v, 20/1) as an eluent to obtain 1.57 g of the target triphenylamine compound (1-6). It was.

  [Example 6] Synthesis of triphenylamine compound (1-7)

  In a 100 ml round bottom flask, 2.4778 g of the phenylimidazole compound (i-4) obtained in Synthesis Example 2, 1.1630 g of the triphenylamine raw material (ii-5) obtained in Synthesis Example 4, 2 mol / l potassium carbonate 11.1 ml of an aqueous solution and 0.1026 g of tetrakis (triphenylphosphine) palladium were weighed and dissolved in 50 ml of tetrahydrofuran under an argon atmosphere, and then heated to reflux for 48 hours. After completion of the reaction, dichloromethane was added to the reaction solution for extraction. The organic layer was dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure. The resulting compound was purified by column chromatography using dichloromethane / tetrahydrofuran (v / v, 30/1) as an eluent to obtain 1.23 g of the target triphenylamine compound (1-7). It was.

<Comparative synthesis example>
To a 100 mL three-necked flask, 15 g of 9-vinylcarbazole, 0.0125 g of azobisisobutyronitrile and 30 g of distilled N, N-dimethylformamide were added, and after bubbling with nitrogen for 15 minutes, the temperature was raised to 80 ° C. Raised and polymerized for 4 hours. Thereafter, the reaction solution is dropped into 400 mL of methanol, and the resulting precipitate is collected by filtration, washed with methanol, and dried under reduced pressure to obtain poly (9-vinylcarbazole) (hereinafter referred to as “polymer (a)”). ) Mw of the polymer (a) was 30,000.

[Example 7]
(A) Preparation of composition for organic EL device 1.0 g of the triphenylamine compound (1-1) obtained in Example 1 and an iridium complex in which x is 0 and y is 0 in the above general formula (2) 37.4 mg was dissolved in chlorobenzene to prepare an organic EL device composition solution (hereinafter also referred to as “composition solution (1)”) having a total concentration of 3% by mass of the triphenylamine component and the complex component.

(B) Production of organic EL element An ITO substrate formed by forming an ITO film on a glass transparent substrate was washed in this order using a neutral detergent, ultrapure water, isopropyl alcohol, ultrapure water and acetone as washing liquids. After ultrasonic cleaning, UV-ozone (UV / O ₃ ) cleaning was further performed.

A poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS) solution was applied onto the cleaned ITO substrate by a spin coating method, and the obtained coating film with a thickness of 65 nm was applied in a nitrogen atmosphere. The hole injection transport layer was formed by drying at 250 ° C. for 30 minutes.

  The composition solution (1) is applied as a light-emitting layer forming liquid to the surface of the obtained hole injecting and transporting layer by a spin coating method, and the obtained coating film having a thickness of 70 nm is applied at 150 ° C. in a nitrogen atmosphere. The light emitting layer was formed by drying for 10 minutes.

Next, after fixing the laminated body in which the hole injecting and transporting layer and the light emitting layer are laminated in this order on the ITO substrate in the vacuum device, the inside of the vacuum device is reduced to 1 × 10 ⁻³ Pa or less. , 3,5-tri (phenyl-2-benzimidazolyl) benzene (TPBI) was vapor-deposited with a thickness of 30 nm to form a hole blocking layer made of a TPBI film.

  On the obtained hole block layer, lithium fluoride was deposited with a thickness of 0.5 nm to form an electron injection layer made of a lithium fluoride film. On the obtained electron injection layer, calcium was vapor-deposited with a thickness of 30 nm, and then aluminum was vapor-deposited with a thickness of 100 nm to form a cathode made of a calcium / aluminum film. Then, the organic EL element (henceforth "the organic EL element (1)") was manufactured by sealing with a glass material.

(3) Characteristic evaluation of organic EL element About the obtained organic EL element (1), when the light emitting layer was caused to emit light using the ITO film as an anode and the calcium / aluminum film as a cathode, from the organic EL element (1), Light emission with a wavelength near 515 nm derived from a specific iridium complex was obtained. Moreover, the light emitting layer of the organic EL element (1) was made to emit light, and the maximum light emission luminance and light emission efficiency were measured. The results are shown in Table 1.

  Further, the organic EL element (1) was turned on at 100 Cd, the current at that time was kept flowing constantly, and the time until the luminance reached 50 Cd (hereinafter simply referred to as “half-life”) was measured. Next, in the same manner as in the organic EL device (1) except that the polymer (a) obtained in the comparative synthesis example was used instead of the triphenylamine compound (1-1), a comparative organic material was used. An EL element (a) was produced, and the half-life of the organic EL element (a) was measured. The relative half life of the organic EL device (1) when the half life of the organic EL device (a) was 100 was defined as “service life”. The results are shown in Table 1.

[Examples 8 to 11]
In Example 7, a composition was prepared in the same manner as in Example 7, except that the triphenylamine compound shown in Table 1 was used instead of the triphenylamine compound (1-1). An organic EL element was produced using the product and evaluated. The results are shown in Table 1.

It is sectional drawing for description which shows an example of a structure of the organic electroluminescent element of this invention. 1 is a ¹ H-NMR spectrum of a triphenylamine compound (1-1) obtained in Example 1. 3 is a ¹³ C-NMR spectrum of the triphenylamine compound (1-1) obtained in Example 1. FIG. 2 is a ¹ H-NMR spectrum of a triphenylamine compound (1-4) obtained in Example 2. 3 is a ¹³ C-NMR spectrum of a triphenylamine compound (1-4) obtained in Example 2. 2 is a ¹ H-NMR spectrum of a triphenylamine compound (1-2) obtained in Example 3. 3 is a ¹³ C-NMR spectrum of a triphenylamine compound (1-2) obtained in Example 3. 2 is a ¹ H-NMR spectrum of a triphenylamine compound (1-5) obtained in Example 4. 3 is a ¹³ C-NMR spectrum of a triphenylamine compound (1-5) obtained in Example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Anode 3 Hole injection transport layer 4 Light emitting layer 5 Electron injection layer 6 Cathode 7 DC power supply 8 Hole block layer

Claims (4)

A triphenylamine compound represented by the following general formula (1):

(In formula, R < ¹ > and R < ² > may be same or different and are a hydrogen atom, a C1-C20 alkyl group, or a C6-C20 aryl group.)   An organic electroluminescent element composition comprising the triphenylamine compound, a triplet luminescent metal complex compound, and a solvent.   The composition for an organic electroluminescence device according to claim 2, wherein the triplet light-emitting metal complex compound is a complex compound of iridium and a nitrogen atom-containing aromatic compound.   It has a light emitting layer formed using the composition for organic electroluminescent elements of Claim 2 or 3, The organic electroluminescent element characterized by the above-mentioned.

Images