JP4879114B2 - COMPOUND FOR ORGANIC ELECTROLUMINESCENT DEVICE, COMPOSITION FOR ORGANIC ELECTROLUMINESCENT DEVICE, AND ORGANIC ELECTROLUMINESCENT DEVICE - Google Patents

Description

  The present invention relates to a compound for an organic electroluminescence element used as a material for an organic electroluminescence element, a composition for an organic electroluminescence element, and an organic electroluminescence element.

An organic electroluminescence element (hereinafter also referred to as “organic EL element”) can be driven by a DC voltage, is a self-luminous element, has a wide viewing angle and high visibility, and a response speed. Therefore, it is expected as a next-generation display element and has been actively researched.
As such an organic EL element, one having a single layer structure in which a light emitting layer made of an organic material is formed between an anode and a cathode, one having a hole transport layer between the anode and the light emitting layer, A multilayer structure such as one having an electron transport layer between a cathode and a light emitting layer is known. Each of these organic EL elements emits light by recombination of electrons injected from the cathode and holes injected from the anode in the light emitting layer (see, for example, Patent Document 1). .

Conventionally, in an organic EL device, a hole transport layer is provided between an anode and a light emitting layer and an electron transport layer is provided between a cathode and a light emitting layer, and the structure of the hole transport layer and the electron transport layer is configured. Suitable materials as materials, specifically, low-molecular crystalline materials having a hole transporting property suitable as a constituent material for a hole transport layer, and electron transporting properties suitable as a constituent material for an electron transport layer High efficiency is achieved by using a low molecular crystalline material and a material having different characteristics.
Here, as a low molecular crystalline material exhibiting an electron transporting property, for example, BND (2,5-bis (1-naphthyl) -1,3,4-oxadiazole) is exemplified (FIG. 11 shows a B3LYP type general-purpose material). (The shape of LUMO and HOMO of BND calculated by the density functional method using the function is shown.)
In the organic EL device, electrons injected from the cathode move mainly along the intermolecular overlap of the lowest unoccupied orbit (LUMO) of the molecules constituting the electron transport layer. In general, the LUMO of a material having a property is a π ^* orbit that is spread and delocalized in a molecule, and its energy order is lowered (an electron affinity is increased), which may increase the electron injection efficiency and the electron transport property. Are known. Actually, the LUMO of BND is lower than the LUMO of molecules related to materials having hole transport properties, while the distribution shape of the highest occupied orbit (HOMO) of BND is also a typical π orbit. The range (spreading) of the distribution almost coincides with LUMO.
On the other hand, as a low molecular crystalline material having a hole transporting property, for example, α-NPD ([N, N′-di (naphthalen-1-yl) -N, N′-diphenylbenzidine] ) can be cited (FIG. 12 shows the LUMO and HOMO shapes of α-NPD calculated by the density functional method using the B3LYP type functional.
In the organic EL device, holes injected from the anode move mainly along the intermolecular overlap of HOMO molecules constituting the hole transport layer, but the hole transport property such as α-NPD. In general, HOMO of a material having π is a delocalized π orbital that spreads in the molecule, and the increase in the energy level (decrease in ionization potential) increases the hole injection efficiency and the hole transportability. Are known. Actually, the distribution shape of HOMO of α-NPD is a typical π orbit, and the range (spread) of the distribution is almost the same as LUMO.

  As described above, since the constituent materials of the hole transport layer and the electron transport layer are required to have mutually conflicting characteristics, it is not possible to form the hole transport layer and the electron transport layer using the same constituent material. It is considered difficult. In particular, the reason why it is difficult to form the hole transport layer and the electron transport layer from the same material is that either a material such as BND that exhibits electron transport properties or a material such as α-NPD that exhibits hole transport properties. Also, the distribution shape of HOMO and LUMO greatly overlaps in the whole molecule, and one-electron transition from HOMO to LUMO is an allowable transition having a large oscillator strength. According to time-dependent density functional theory (TD-DFT) calculation, the lowest energy one-electron excitation of BND is a transition from HOMO to LUMO (wavelength: 370 nm, oscillator strength: 0.479), and α− Since the lowest energy one-electron excitation of NPD is also a transition from HOMO to LUMO (wavelength: 399 nm, oscillator strength: 0.319), in organic compounds, HOMO and LUMO are spatially overlapped. When one-electron transition is allowed, electrons and holes are more likely to recombine in the compound or in the energy band formed by the compound assembly, resulting in the excitation energy of the molecule being organic. It is considered that it is difficult to efficiently transmit the phosphorescent material, which is a constituent material of the light emitting layer of the EL element. On the other hand, when the vibration intensity at one-electron transition from HOMO to LUMO is zero (forbidden transition) or very low, the probability of widthless deactivation is high, so it is suitable as a material for organic EL elements. It is thought that it is not something.

Japanese Patent Laid-Open No. 2001-257076

The present invention is based on the above circumstances, and as a result of repeated studies by the present inventors, as a condition for one material to have both electron transport properties and hole transport properties, (a) HOMO and LUMO (B) The aromatic rings in the molecule have a twisted structure rather than coplanar, and the separation between HOMO and LUMO is enhanced. (C) One-electron excitation from HOMO to LUMO is not a forbidden transition but allowed transition, and (d) HOMO is used to ensure a balance between electron transportability and hole transportability and transparency in the visible region. LUMO has been achieved by finding molecular design guidelines that each need to have an appropriate energy level and constructing a compound that satisfies the conditions. An object of the present invention is to provide a compound for an organic electroluminescence device and a composition for an organic electroluminescence device, both having a hole transporting property and an electron transporting property, and suitably used as a light emitting material for an organic electroluminescence device. .
Another object of the present invention is to provide an organic electroluminescence device having excellent light emission characteristics.
Here, the compound group constructed based on the above-mentioned molecular design guidelines is divided into “frontier molecular orbitals” named by Dr. Kenichi Fukui, that is, HOMO and LUMO, which are substantially separated in their distribution shape and one-electron excited state. As a result, since the transition from HOMO to LUMO is a transition in which electrons move in the molecule, it can be named “frontier separation type” organic EL compound.
The compound for an organic EL device of the present invention is based on the molecular design guidelines for frontier-separated organic EL compounds by the present inventors. It is constructed as a compound that satisfies the requirements of the design guideline (electronic state) while selecting sites having excellent properties and fusing them in one molecule.

  The compound for organic electroluminescence devices of the present invention is characterized by comprising a compound represented by the following general formula (I).

[Ar ¹ and Ar ^2, either one aromatic ring in its structure, a bivalent radical having either of the fused rings and heterocyclic, and the other represents a single bond. Ar ³ and Ar ⁴ are each independently an aromatic ring in its structure, a monovalent radical having one of the fused rings and heterocyclic, Ar ³ and Ar ⁴ which are attached to the same nitrogen atom, They may be bonded to each other to form a ring structure. R ¹ represents a monovalent organic group, a hydrogen atom or a fluorine atom. ]

  The composition for organic electroluminescent elements of the present invention is composed of 100 parts by mass of the above-mentioned compound for organic electroluminescent elements, 1-20 parts by mass of the phosphorescent compound, and 100-100,000 parts by mass of organic solvent. Part.

  The organic electroluminescence device of the present invention is characterized by having any of a hole injection / transport layer, an electron injection / transport layer, and a light emitting layer formed of the compound for organic electroluminescence device.

  The phosphorescent organic electroluminescent device of the present invention is characterized by having a light emitting layer comprising the above-mentioned compound for organic electroluminescent device and a phosphorescent compound.

  In the phosphorescent organic electroluminescence device of the present invention, the light emitting layer is preferably formed by using the above-mentioned composition for organic electroluminescence device.

The compound for an organic electroluminescence device of the present invention is useful as a material for an organic electroluminescence device because it has a good electron transport property and a hole transport property and also has a good light emission property.
In addition, the compound for an organic electroluminescence device of the present invention is useful as a material for an organic electroluminescence device because a thin film can be easily formed by either a dry method or a wet method. is there.

  According to the composition for an organic electroluminescence device of the present invention, a thin film can be easily formed by a wet method, and the phosphorescent compound having phosphorescence is contained as the first component. Since the organic electroluminescent element compound is contained as the second constituent component, an organic electroluminescent element having excellent light emission characteristics can be obtained.

  According to the organic electroluminescence device of the present invention, good light emission characteristics can be obtained by using the compound for an organic electroluminescence device as a constituent material of any of a hole injection transport layer, an electron injection transport layer, and a light emitting layer. be able to.

In addition, according to the phosphorescent organic electroluminescent device of the present invention, the above-mentioned compound for organic electroluminescent device is used as a constituent material of the light emitting layer together with the phosphorescent compound, thereby obtaining excellent light emission characteristics by phosphorescence. be able to.
This phosphorescent organic electroluminescent element can be produced by forming a light emitting layer using the composition for an organic electroluminescent element.

  Hereinafter, embodiments of the present invention will be described in detail.

<Compound for organic EL device>
The compound for organic EL devices of the present invention is represented by the above general formula (I) and is useful as a material for organic EL devices.

In general formula (I), Ar ¹ and Ar ² be shown independently an aromatic ring in its structure, a divalent group having any of the fused rings and heterocyclic, or a single bond.

Examples of the divalent group representing the group Ar ¹ and the group Ar ² include those containing an aromatic ring such as a phenylene group and a tolylene group in their constitution, for example, those containing a condensed ring such as a naphthylene group in its constitution, and For example, the structure includes a heterocyclic ring such as a thiophene group and a pyridylene group, and specific examples thereof include groups represented by the following formulas (i-1) to (i-5). .

Ar ³ and Ar ⁴ in the general formula (I) each independently represent a monovalent group having any of an aromatic ring, a condensed ring and a heterocyclic ring in the structure, and these Ar ³ and Ar ⁴ are These may be the same or different, but are preferably the same. Ar ³ and Ar ⁴ bonded to the same nitrogen atom may be bonded to each other to form a ring structure.

The monovalent group represents a group Ar ³ and group Ar ^4, for example, a phenyl group, aromatic ring group containing in its structure, such as a tolyl group, for example, groups containing condensed rings such as a naphthyl group in its structure For example, a pyridyl group etc. are mentioned.
When the group Ar ³ and the group Ar ⁴ are bonded to each other to form a ring structure, these two groups form, for example, a carbazole group.

R ¹ in the general formula (I) represents a monovalent organic group, a hydrogen atom or a fluorine atom.
Examples of the monovalent organic group representing the group R ¹ include an alkyl group having 1 to 20 carbon atoms such as a methyl group and an ethyl group, for example, an aryl group having 6 to 20 carbon atoms such as a phenyl group and a tolyl group, such as tri C1-C20 fluorinated alkyl groups, such as a fluoromethyl group, etc. are mentioned, Among these, a phenyl group is preferable.

  Preferable specific examples of the compound for an organic EL device of the present invention include compounds represented by the following formulas (I-1) to (I-12).

  As an example of the method for synthesizing the compound for organic EL device of the present invention as described above, the synthesis process of the compound for organic EL device represented by the formula (I-8) is shown in the following reaction formula (1).

  The compound for an organic EL device of the present invention can easily form a film by a dry method such as a vacuum vapor deposition method, has excellent solubility in a solvent, and has a coating solution for forming a thin film. Since it can be easily prepared, a thin film can be easily formed by the coating solution. Therefore, the compound for an organic EL device is useful as a material for an organic EL device because it has a high thin film forming ability.

Specifically, since the compound for organic EL device of the present invention has both good electron transporting property and hole transporting property due to its structure, for example, a hole injecting and transporting layer of an organic EL device. In addition, the light-emitting layer of the phosphorescent organic EL element can be formed by combining with a phosphorescent compound described later having phosphorescence as a host compound. It can be suitably used as a material. Furthermore, since this compound for organic EL elements itself has a favorable light emission characteristic, it can be suitably used as a light emitting material constituting the light emitting layer of the organic EL element alone.
Thus, when using the compound for organic EL elements of this invention as a material for organic EL elements, it can be used 1 type or in combination of 2 or more types.
Here, in the organic EL device compound of the present invention, (a) in the distribution shape of HOMO and LUMO, the spatial overlap between them is as small as possible, and (b) a plurality of aromatic rings in the molecule are coplanar. A distorted structure, enhanced separation of HOMO and LUMO, (c) one-electron excitation from HOMO to LUMO is not a forbidden transition, and (d) an electron transport property and positive In order to ensure the balance of pore transportability and transparency in the visible range, HOMO and LUMO satisfy the molecular design guidelines provided that they are at appropriate energy levels. In the compound group constructed based on HOMO and LUMO, HOMO and LUMO are almost separated in their distribution shape and one-electron excited state. Characterized in that the transition of electrons is moved transitions within the molecule is a "frontier separated organic EL compounds." FIG. 8 to FIG. 10 show the LUMO and HOMO shapes calculated by the density functional method using the B3LYP functional for some examples of the organic EL device compound of the present invention which is a frontier separation type organic EL compound. Show.
That is, the compound for an organic EL device of the present invention satisfies the molecular design guideline of the frontier separation type organic EL compound, and has a portion excellent in electron transportability and a portion excellent in hole transportability. And they are compounds that are fused in one molecule.

<Composition for organic EL device>
The composition for an organic EL device of the present invention comprises 100 parts by mass of a component (hereinafter also referred to as “EL component component”) composed of the above-mentioned compound for an organic EL device and a component (hereinafter referred to as a phosphorescent compound). It is also referred to as “light emitting component.”) It contains 1 to 20 parts by mass and 100 to 100,000 parts by mass of an organic solvent.

  Examples of the phosphorescent compound constituting the light-emitting component include iridium complex compounds, platinum complex compounds, palladium complex compounds, rubidium complex compounds, osmium complex compounds, and rhenium complex compounds. Among these, iridium complexes are particularly preferred. Compounds are preferred.

Examples of the iridium complex compound include iridium, 2-phenylpyridine, 3-phenylpyridine, 2-phenylpyrimidine, 4-phenylpyrimidine, 5-phenylpyrimidine, bipyridyl, 1-phenylpyrazole, 2-phenylquinoline, 2- Phenylbenzothiazole, 2-phenyl-2-oxazoline, 2,4-diphenyl-1,3,4-oxadiazole, 5-phenyl-2- (4-pyridyl) -1,3,4-oxadiazole, And a complex compound with a nitrogen atom-containing aromatic compound such as a derivative thereof.
Specific examples of such iridium complex compounds include compounds represented by the following general formulas (1) to (6).

In the general formula (1) to general formula (6), R ^{2 to} R ⁴ are each independently a fluorine atom, a trifluoromethyl group, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. And may be the same as or different from each other. x is an integer of 0 to 4, y is an integer of 0 to 4, z is an integer of 0 to 3, and w is an integer of 0 to 2.

In the above, specific examples of the alkyl group having 1 to 20 carbon atoms related to the substituents R ^{2 to} R ⁴ include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl. Group, t-butyl group, n-hexyl group, n-octyl group and the like.
Specific examples of the aryl group having 6 to 20 carbon atoms related to the substituents R ^{2 to} R ⁴ include phenyl group, o-tolyl group, m-tolyl group, p-tolyl group, 2,3-xylyl group, Examples include 2,4-xylyl group, 2,5-xylyl group, 2,6-xylyl group, 3,4-xylyl group, 3,5-xylyl group, 4-biphenyl group, 1-naphthyl group, and the like. .

  In the composition for an organic EL device of the present invention, as the iridium complex compound, it is preferable to use an iridium complex compound in which x and y are both 0 in the general formula (1).

The content rate of the light emitting component in the composition for organic EL devices of the present invention is 1 to 20 parts by mass, preferably 1 to 10 parts by mass with respect to 100 parts by mass of the compound component for EL elements.
When the proportion of the light emitting component is excessive, there is a possibility that a phenomenon of concentration quenching in which the light emission luminance decreases instead.

  The organic solvent dissolves the compound for organic EL device of the present invention constituting the compound component for EL device and the phosphorescent compound constituting the light emitting component, thereby containing the compound component for EL device and the light emitting component. It is for preparing a solution.

The organic solvent is not particularly limited as long as it can dissolve the compound for organic EL device and the phosphorescent compound of the present invention, and specific examples thereof include aromatic hydrocarbons such as toluene, xylene and mesitylene; Halogenated hydrocarbons such as chloroform, dichloroethane, tetrachloroethane, chlorobenzene, o-dichlorobenzene; amides such as N, N-dimethylformamide, N, N-dimethylacetamide, 1-methyl-2-pyrrolidone, 2- Examples include heptanone, cyclohexanone, propylene glycol methyl ether acetate, ethyl lactate, ethyl 3-ethoxypropionate and anisole. These organic solvents can be used alone or in combination of two or more.
Among these, it is preferable to use an organic solvent having an appropriate evaporation rate, specifically, an organic solvent having a boiling point of about 70 to 200 ° C. in that a thin film having a uniform thickness can be easily obtained.

Although the content rate of the organic solvent in the composition for organic EL elements of this invention changes with kinds of the compound component for EL elements and the light emitting component, it is 100-100,000 mass parts with respect to 100 mass parts of compound components for EL elements. Yes, preferably 1,000 to 10,000 parts by mass.
When the content ratio of the organic solvent is within the above range, the compound for an organic EL device and the phosphorescent compound of the present invention can be dissolved uniformly, and a film can be formed in a preferable film thickness.

  If necessary, any additive such as a charge transporting compound can be added to the composition for an organic EL device of the present invention.

  Specific examples of the charge transporting compound include compounds having a charge transporting property represented by the following formulas (A-1) to (A-10), and the following formulas (B-1) to (B-20). And a compound having an electron transporting property and a compound having a hole transporting property represented by the following formulas (C-1) to (C-34).

Here, in the formula (B-16), R ⁵ represents any group represented by the following formulas (A) to (C).

  Here, in the formula (C-12), m represents an integer of 1 or more.

  The content of the charge transporting compound in the organic EL device material composition of the present invention is preferably 0 to 200 parts by weight, more preferably 0 to 100 parts by weight, based on 100 parts by weight of the EL component compound component. It is.

According to such a composition for an organic EL device, a phosphorescent organic EL device that emits light with sufficiently high emission luminance and has a light emitting layer with good durability can be obtained, and the light emitting layer Can be easily formed by a wet method.
As a method of forming a light emitting layer with this composition for organic EL elements, it can form by applying the said composition for organic EL elements to the surface of a suitable base | substrate, and removing an organic solvent.
As a method for applying the composition for an organic EL device, for example, an appropriate method such as a spin coating method, a dipping method, a roll coating method, an ink jet method, or a printing method can be employed.
Although the thickness of the light emitting layer formed is not specifically limited, Usually, 10-200 nm, Preferably it selects in the range of 30-100 nm.

<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 the organic EL element of this example, an anode 2 as an electrode for supplying holes is provided on a transparent substrate 1 by, for example, a transparent conductive film, and a hole injecting and transporting layer 3 is provided on the anode 2. A light emitting layer 4 is provided on the hole injecting and transporting layer 3, a hole blocking layer 8 is provided on the light emitting layer 4, and an electron injecting and transporting layer 5 is provided on the hole blocking layer 8. A cathode 6 which is an electrode for supplying electrons is provided on the top. The anode 2 and the cathode 6 are electrically connected to a DC power source 7.

In this organic EL element, as the transparent substrate 1, a soda glass substrate, a transparent resin substrate, a quartz glass substrate, or the like can be used.
As a material constituting the anode 2, a transparent material having a high work function, for example, 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, for example, an ITO (indium-tin oxide) film, a tin (IV) oxide film, a copper (II) oxide film, a zinc oxide film, or the like can be used.
Moreover, although the thickness of the anode 2 changes with kinds of material, it is normally selected in the range of 10-1,000 nm, Preferably it is 50-200 nm.

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. Is.
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 preferably used. A compound for EL device can also be used.
The thickness of the hole injecting and transporting layer 3 is not particularly limited, but is usually selected in the range of 10 to 200 nm.

The light emitting layer 4 has a function of combining electrons and holes and emitting the binding energy as light. The light emitting layer 4 is a compound for an organic EL device of the present invention or an organic EL device of the present invention. It is formed by the composition for use. Here, those in which the light emitting layer 4 is formed using the composition for organic EL elements of the present invention, and those composed of the compound for organic EL elements of the present invention and a phosphorescent compound are particularly phosphorescent organic EL. It is considered as an element.
The thickness of the light emitting layer 4 is not particularly limited, but is usually selected in the range of 5 to 200 nm.

  The hole blocking layer 8 prevents the holes supplied to the light emitting layer 4 from entering the electron injecting and transporting layer 5 through the hole injecting and transporting layer 3, and recombines holes and electrons in the light emitting layer 4. It has a function of promoting light emission and improving luminous efficiency.

Examples of the material constituting the hole blocking layer 8 include 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (basocproin: BCP) represented by the following formula (a), and the following formula (b). 1,3,5-tri (phenyl-2-benzimidazolyl) benzene (TPBI) represented by the formula can be preferably used.
Moreover, the thickness of the hole block layer 8 is normally selected in the range of 10 to 100 nm.

  The electron injecting and transporting 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. As a material constituting the electron injecting and transporting layer 5, a co-evaporation system (BPCs) of a bathophenanthroline-based material and cesium is preferably used. As other materials, alkali metals and compounds thereof (for example, lithium fluoride, Lithium oxide), alkaline earth metals and compounds thereof (for example, magnesium fluoride and strontium fluoride) can be used, and the compound for an organic EL device of the present invention can also be used. The thickness of the electron injecting and transporting layer 5 is usually selected in the range of 0.1 to 100 nm.

As a material constituting the cathode 6, a material having a small work function, for example, 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.
The thickness of the cathode 6 varies depending on the type of material, but is usually selected in the range of 10 to 1,000 nm, preferably 50 to 200 nm.

In the present invention, the organic EL element is manufactured as follows, for example.
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 thus formed.
As a method for forming the hole injection transport layer 3, specifically, a hole injection transport layer forming liquid is prepared by dissolving the charge injection transport material in an appropriate solvent. A method of forming the hole injection transport layer 3 by applying to the surface of the anode 2 and subjecting the obtained coating film to solvent removal treatment can be used.

Next, the light emitting layer 4 is formed on the formed hole injecting and transporting layer 3.
As a method for forming the light emitting layer 4, for example, the composition for organic EL elements of the present invention is used as a light emitting layer forming liquid, and this light emitting layer forming liquid is applied onto the hole injecting and transporting layer 3, and the resulting coating film is obtained. A method of forming the light emitting layer 4 by performing a solvent removal treatment on the substrate can be used.
Moreover, as a method of forming a light emitting layer with the compound for organic EL elements of this invention, a vacuum evaporation method etc. can be utilized and the solution which melt | dissolved the said compound for organic EL elements in the organic solvent is hole injection. A method of forming the light emitting layer 4 by applying on the transport layer 3 and heat-treating the obtained coating film can also be used. Furthermore, the light emitting layer 4 can also be formed by co-evaporating the compound for an organic EL device of the present invention and the phosphorescent compound, and the phosphorescent organic EL can be formed by forming the light emitting layer 4 by this technique. An element can be obtained.

  Then, a hole blocking layer 8 is formed on the light emitting layer 4 formed in this way, and an electron injecting and transporting layer 5 is formed on the hole blocking layer 8. By forming the cathode 6 thereon, an organic EL element having the configuration shown in FIG. 1 can be obtained.

  In the above, as a method of forming the hole block layer 8, the electron injection transport layer 5, and the cathode 6, a dry method such as a vacuum evaporation method can be used.

In the above 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. Then, the light is emitted to the outside through the transparent substrate 1.
According to the organic EL element having such a configuration, since the light emitting layer 4 is formed of the above-mentioned compound for organic EL element or composition for organic EL element, excellent durability is obtained and high luminance is obtained. High luminous efficiency is also obtained. In particular, when the light-emitting layer 4 is formed of the composition for organic EL elements or the compound for organic EL elements and a phosphorescent compound, further excellent light emission Luminance and luminous efficiency are 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. As a result, higher emission luminance and higher light emission can be obtained. Efficiency is obtained.

  In the organic EL element having such a configuration, the hole block layer 8 is preferably formed, but the hole block layer 8 may not be provided.

In the organic EL device having such a configuration, an electron blocking layer may be formed between the hole injection transport layer 3 and the light emitting layer 4 as necessary.
This electron blocking layer has a function of suppressing electrons from entering the hole injecting and transporting layer 3, promoting the bonding of electrons and holes in the light emitting layer 4, and further improving the light emission efficiency.
Examples of the material constituting the electron blocking layer include electrons such as amine compounds and polyvinyl carbazole represented by the above formulas (C-1) to (C-34), and polymers represented by the following general formula (7). Materials having a hole transporting property as compared with the transporting property can be used, and a solvent-insoluble electron blocking layer can be obtained by adding a crosslinking agent such as a silane coupling agent to these materials. The thickness of this electronic block is usually selected in the range of 1 to 100 nm.

[Wherein R ⁶ represents an alkyl group having 1 to 20 carbon atoms. p is the number of repetitions. ]

  Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

(Synthesis Example 1 of Compound for Organic EL Device)
First, in a 100 mL two-necked flask equipped with a nitrogen inlet tube and a condenser tube, 5.02 g (30 mmol) of carbazole, 10.62 g (45 mmol) of 1,3-dibromobenzene, 1.71 g (4.5 mmol) of copper iodide. , Potassium carbonate 12.44 g (90 mmol), 18-crown-6-ether 0.37 g (1.4 mmol) and 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone 35 mL (hereinafter referred to as “DMPU”) was added, and the reaction was carried out under a nitrogen atmosphere at a temperature of 170 ° C. for 6 hours. After completion of the reaction, the reaction mixture was extracted with ethyl acetate and purified with a silica column using hexane as a developing solvent to obtain 4.74 g of 9- (3-bromophenyl) -9H-carbazole.
Next, 1.16 g (3.6 mmol) of 9- (3-bromophenyl) -9H-carbazole was charged into a 100 mL two-necked flask equipped with a nitrogen introduction tube, 40 mL of dry diethyl ether was added, and nitrogen atmosphere was added. The solution was dissolved at a temperature of 0 ° C. Thereafter, 1.52 mL (3.96 mmol) of a 2.6 Mn-butyllithium hexane solution was added dropwise and stirred for 4 hours. Next, 0.5 g (1.5 mmol) of bathophenanthroline dissolved in 20 mL of dry toluene was added, and the mixture was stirred at room temperature for 48 hours. After completion of the reaction, the reaction product is extracted with methylene chloride, purified with a silica column using a mixed solvent of hexane: methylene chloride = 1: 1, and recrystallized with a mixed solvent of chloroform / hexane. 0.6 g of white crystals was obtained. The synthesis step according to Synthesis Example 1 of the compound for organic EL element is shown in the above reaction formula (1).
When the ¹ H-NMR spectrum and ¹³ C-NMR spectrum of the obtained reaction product were measured, the compound represented by the above formula (I-8) (hereinafter referred to as “Compound (1) for organic EL device”). .).
FIG. 2 shows a ¹ H-NMR spectrum diagram, and FIG. 3 shows a ¹³ C-NMR spectrum diagram.

(Synthesis Example 2 of Compound for Organic EL Device)
In Synthesis Example 1 of Compound for Organic EL Device, yellow was used as the reaction product in the same manner as in Synthesis Example 1 of Compound for Organic EL Device except that 1,4-dibromobenzene was used instead of 1,3-dibromobenzene. 0.68 g of crystals was obtained.
When the ¹ H-NMR spectrum and the ¹³ C-NMR spectrum of the obtained reaction product were measured, the compound represented by the above formula (I-7) (hereinafter referred to as “Compound (2) for organic EL device”). .).
FIG. 4 shows a ¹ H-NMR spectrum diagram, and FIG. 5 shows a ¹³ C-NMR spectrum diagram.

(Synthesis Example 3 of Compound for Organic EL Device)
First, in a 100 mL two-necked flask equipped with a nitrogen introduction tube and a cooling tube, 5.08 g (30 mmol) of diphenylamine, 10.62 g (45 mmol) of 1,3-dibromobenzene, 1.71 g (4.5 mmol) of copper iodide. , Potassium carbonate 12.44 g (90 mmol), 18-crown-6-ether 0.37 g (1.4 mmol) and 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone 35 mL was added, and the reaction was carried out under a nitrogen atmosphere at a temperature of 170 ° C. over 6 hours. After completion of the reaction, the reaction mixture was extracted with ethyl acetate and purified with a silica column using hexane as a developing solvent to obtain 5.0 g of white crystals of 3-bromo-N, N-diphenylaminobenzene.
Next, 3.24 g (10.0 mmol) of 3-bromo-N, N-diphenylaminobenzene was charged into a 200 mL three-necked flask equipped with a nitrogen introduction tube, and 80 mL of dry diethyl ether was added, And dissolved at 0 ° C. Thereafter, 4.6 mL (12.0 mmol) of a 2.6 Mn-butyllithium hexane solution was added dropwise and stirred for 4 hours. Next, 0.997 g (3.0 mmol) of bathophenanthroline dissolved in 40 mL of dry toluene was added, and the mixture was stirred at room temperature for 48 hours. After completion of the reaction, the reaction product is extracted with methylene chloride, purified with a silica column using a mixed solvent of hexane: methylene chloride = 1: 1, and recrystallized with a mixed solvent of chloroform / hexane. 1.30 g of pale yellow crystals were obtained.
When the ¹ H-NMR spectrum and the ¹³ C-NMR spectrum of the obtained reaction product were measured, the compound represented by the above formula (I-2) (hereinafter referred to as “compound for organic EL device (3)”). .).
FIG. 6 shows a ¹ H-NMR spectrum diagram, and FIG. 7 shows a ¹³ C-NMR spectrum diagram.

(Preparation Example 1 of Composition for Organic EL Device)
0.1 g of the compound for organic EL device (2) and an iridium complex compound represented by the following formula (c) in which x and y are both 0 in the general formula (1) (hereinafter, “iridium complex compound (1) The organic EL element composition (A-1) was obtained by dissolving 0.004 g in 3.4 g of chlorobenzene.

(Preparation Example 2 of Composition for Organic EL Device)
The organic EL element composition (A-2) was obtained by dissolving 0.1 g of the organic EL element compound (3) and 0.004 g of the iridium complex compound (1) in 3.4 g of chlorobenzene.

[Example 1]
(Production Example 1 of Organic EL Element)
An ITO substrate in which an ITO film is formed on a transparent substrate is prepared, and this ITO substrate is ultrasonically cleaned using a neutral detergent, ultrapure water, isopropyl alcohol, ultrapure water, and acetone in this order, and further UV-ozone (UV / O ₃ ) cleaning was performed.
Next, a poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate aqueous solution was applied on the ITO substrate by a spin coating method, and the resulting 65 nm thick coating film was formed at 250 ° C. in a nitrogen atmosphere at 250 ° C. A hole injecting and transporting layer was formed by drying for a minute.
On this hole injecting and transporting layer, the composition for organic EL elements (A-1) was applied as a light emitting layer forming liquid by a spin coating method, and the resulting 40 nm thick coating film was applied at 150 ° C. in a nitrogen atmosphere. The light emitting layer was formed by drying for 10 minutes.
Next, the laminate in which the hole injecting and transporting layer and the light emitting layer are laminated in this order on the ITO film is fixed in a vacuum apparatus, the inside of the vacuum apparatus is reduced to 1 × 10 ⁻² Pa or less, and the TPBI is 30 nm thick Then, a hole blocking layer is formed by evaporation, and then lithium fluoride is evaporated to a thickness of 0.5 nm to form an electron injecting and transporting layer. Further, a calcium metal layer having a thickness of 30 nm and an aluminum having a thickness of 100 nm are formed. Metal layers were deposited in this order to form the cathode. Then, the organic EL element (1) was produced by sealing with glass.

(Characteristic evaluation of organic EL elements)
With respect to the obtained organic EL element (1), when the light emitting layer was caused to emit light and the maximum light emission luminance and light emission efficiency were measured, the maximum light emission luminance was 300 Cd / m ² and the light emission efficiency was 8.0 Cd / A. .

[Example 2]
(Production Example 2 of Organic EL Element)
Example 1 for producing an organic EL element in Example 1 for producing an organic EL element in Example 1, except that the composition for organic EL element (A-2) was used instead of the composition for organic EL element (A-1). In the same manner as in Example 1, an organic EL device (2) was produced.

(Characteristic evaluation of organic EL elements)
With respect to the obtained organic EL device (2), when the light emitting layer was made to emit light and the maximum light emission luminance and light emission efficiency were measured, the maximum light emission luminance was 200 Cd / m ² and the light emission efficiency was 0.3 Cd / A. .

Example 3
(Production Example 3 of Organic EL Element)
An ITO substrate in which an ITO film is formed on a transparent substrate is prepared, and this ITO substrate is ultrasonically cleaned using a neutral detergent, ultrapure water, isopropyl alcohol, ultrapure water, and acetone in this order, and further UV-ozone (UV / O ₃ ) cleaning was performed.
Next, a poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate aqueous solution was applied on the ITO substrate by a spin coating method, and the resulting 65 nm thick coating film was formed at 250 ° C. in a nitrogen atmosphere at 250 ° C. A hole injecting and transporting layer was formed by drying for a minute.
On the hole injecting and transporting layer, the organic EL device compound (2) and the iridium complex compound (1) are mixed at a concentration of 6 mol% of the iridium complex compound (1) with respect to the organic EL device compound (2). Thus, a 40 nm thick light emitting layer was formed by co-evaporation.
Next, the laminate in which the hole injecting and transporting layer and the light emitting layer are laminated in this order on the ITO film is fixed in a vacuum apparatus, the inside of the vacuum apparatus is reduced to 1 × 10 ⁻² Pa or less, and the TPBI is 30 nm thick. Then, a hole blocking layer is formed by evaporation, and then lithium fluoride is evaporated to a thickness of 0.5 nm to form an electron injecting and transporting layer. Further, a calcium metal layer having a thickness of 30 nm and an aluminum having a thickness of 100 nm are formed. Metal layers were deposited in this order to form the cathode. Then, the organic EL element (3) was produced by sealing with glass.

(Characteristic evaluation of organic EL elements)
With respect to the obtained organic EL element (3), when the light emitting layer was caused to emit light and the maximum light emission luminance and light emission efficiency were measured, the maximum light emission luminance was 1200 Cd / m ² and the light emission efficiency was 0.2 Cd / A. .

Example 4
(Production Example 4 of Organic EL Element)
In the organic EL element production example 3 in Example 3, the organic EL element compound (1) was used in the same manner as in the organic EL element production example 1 except that the organic EL element compound (1) was used instead of the organic EL element compound (2). An EL element (4) was produced.

(Characteristic evaluation of organic EL elements)
With respect to the obtained organic EL element (4), when the light emitting layer was caused to emit light and the maximum light emission luminance and light emission efficiency were measured, the maximum light emission luminance was 1700 Cd / m ² and the light emission efficiency was 0.3 Cd / A. .

Example 5
(Production Example 5 of Organic EL Element)
In the organic EL element production example 3 in Example 3, the organic EL element compound (3) was used in the same manner as in the organic EL element production example 1 except that the organic EL element compound (3) was used instead of the organic EL element compound (2). An EL element (4) was produced.

(Characteristic evaluation of organic EL elements)
With respect to the obtained organic EL element (4), when the light emitting layer was caused to emit light and the maximum light emission luminance and light emission efficiency were measured, the maximum light emission luminance was 200 Cd / m ² and the light emission efficiency was 0.2 Cd / A. .

It is sectional drawing for description which shows an example of a structure of the organic electroluminescent element of this invention. It is ¹ H-NMR spectrum diagram according to Synthesis Example 1 of compound for organic EL device. It is a < ¹³ > C-NMR spectrum figure which concerns on the synthesis example 1 of the compound for organic EL elements. It is a < ¹ > H-NMR spectrum figure concerning the synthesis example 2 of the compound for organic EL elements. It is a < ¹³ > C-NMR spectrum figure which concerns on the synthesis example 2 of the compound for organic EL elements. It is a < ¹ > H-NMR spectrum figure concerning the synthesis example 3 of the compound for organic EL elements. It is a ¹³ C-NMR spectrum according to Synthesis Example 3 of a compound for an organic EL device. It is explanatory drawing which shows the shape of LUMO and HOMO of the compound for organic EL elements of this invention represented by Formula (I-8) calculated by the density functional method using a B3LYP type functional. It is explanatory drawing which shows the shape of LUMO and HOMO of the compound for organic EL elements of this invention represented by Formula (I-2) calculated by the density functional method using a B3LYP type functional. It is explanatory drawing which shows the shape of LUMO and HOMO of the compound for organic EL elements of this invention represented by Formula (I-7) calculated by the density functional method using a B3LYP type functional. B3LYP KataHiroshi function was calculated by the density functional method using, is a diagram showing the BND (2,5-bis (1-naphthyl) -1,3,4-oxadiazole) of LUMO and HOMO of the shape . The LUMO and HOMO shapes of α-NPD ([N 1 , N′-di (naphthalen-1-yl) -N 1 , N′-diphenylbenzidine]) calculated by the density functional method using the B3LYP type functional It is explanatory drawing shown.

Explanation of symbols

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

Claims (5)

The compound for organic electroluminescent elements characterized by consisting of a compound represented by the following general formula (I).
[Ar ¹ and Ar ^2, either one aromatic ring in its structure, a bivalent radical having either of the fused rings and heterocyclic, and the other represents a single bond. Ar ³ and Ar ⁴ are each independently an aromatic ring in its structure, a monovalent radical having one of the fused rings and heterocyclic, Ar ³ and Ar ⁴ which are attached to the same nitrogen atom, They may be bonded to each other to form a ring structure. R ¹ represents a monovalent organic group, a hydrogen atom or a fluorine atom. ]   100 mass parts of components which consist of the compound for organic electroluminescent elements of Claim 1, 1-20 mass parts of components which consist of a phosphorescent compound, and 100-100,000 mass parts of organic solvents are contained. The composition for organic electroluminescent elements characterized by these.   An organic electroluminescence device comprising any one of a hole injecting and transporting layer, an electron injecting and transporting layer, and a light emitting layer formed of the compound for organic electroluminescence device according to claim 1.   A phosphorescent organic electroluminescent device comprising a light emitting layer comprising the organic electroluminescent device compound according to claim 1 and a phosphorescent compound.   The phosphorescent organic electroluminescence device according to claim 4, wherein the light emitting layer is formed by using the composition for an organic electroluminescence device according to claim 2.