JP7655153B2 - Organic metal complex and its synthesis method, organic copper complex synthesis method, film, organic electronics device, and organic electroluminescence element - Google Patents

Description

The present invention relates to an organometallic complex and a method for synthesizing the same, a method for synthesizing an organocopper complex, a film, an organic electronics device, and an organic electroluminescence element. More specifically, the present invention relates to an organometallic complex having excellent optical or electronic functions and a method for synthesizing the same , a method for synthesizing an organocopper complex, a film and an organic electronics device containing the organometallic complex, and in particular to an organic electroluminescence element having a reduced driving voltage and improved external extraction efficiency.

Organic compounds with a ring structure consisting of approximately 10 or more atoms, such as porphyrins, macrolides, and crown ethers, are called macrocyclic compounds, and some of them can coordinate with metal atoms or ions at the center of the ring structure to form complexes.

Many of the organometallic complexes that have such macrocyclic compounds as ligands have excellent optical or electronic functions, and are used in a variety of fields. For example, phthalocyanine has a planar structure with little steric hindrance, so the π-electron conjugated system spreads throughout the molecule, and in complexes with copper, the color is excellent and clear, and it is also highly durable, so it is widely used in blue organic pigments, CD-Rs as recording media, organic electroluminescence elements, organic transistors, etc.

These macrocyclic compounds have various functions due to their unique structures, and are expected to be used in a wide range of fields. However, there are only a limited number of simple and efficient methods for producing (synthesizing) them. For this reason, research and development has been conducted into simple and efficient methods for producing macrocyclic compounds and organometallic complexes that have macrocyclic compounds as ligands.

Non-Patent Document 1 describes a method for synthesizing a cyclic compound in which six pyridines are bonded by single bonds. However, this synthesis method does not describe a method for selectively bonding both ends of the six bonded pyridines, and the yield of the cyclic compound was extremely low.

Non-Patent Documents 2 and 3 also do not describe a method for selectively synthesizing cyclic compounds, and the yield of cyclic compounds was extremely low. In addition, the technology described in Non-Patent Document 2 can only be used when the central metal atom or ion is sodium, and there is room for further study on technologies using other metal species.

Newkome, G. R. et al. J. Am. Chem. Soc. 1983, 105, 5956. Toner, J. L. Tetrahedron Lett. 1983.24.2707. Bell, T. W. et al. J. Am. Chem. Soc. 1986, 108, 8109

The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved by the present invention is to provide an organometallic complex having excellent optical or electronic engineering functions and a method for synthesizing the same , a method for synthesizing an organocopper complex, a film and an organic electronics device containing the organometallic complex, and in particular an organic electroluminescent element having a reduced driving voltage and improved external extraction efficiency.

In order to solve the above-mentioned problems, the present inventors have investigated the causes of the above-mentioned problems and have found that an organometallic complex having a structure represented by the following general formula (1) has excellent optical or electrical functions, thereby completing the present invention.
That is, the above-mentioned problems of the present invention are solved by the following means.

1. An organometallic complex having a structure represented by the following structural formulae MO-7, MO-8, MO-9, MO-10, MO-11, MO-16, MO-17, MO-18, MO-20, MO-23 and MO-24 .

2. A method for synthesizing an organometallic complex having a structure represented by the following general formula (3) ,
The method includes a step of cyclizing the ligand by a coupling reaction in the presence of a metal atom or ion,
The metal is Ni or Pd.
1. A method for synthesizing an organometallic complex comprising the steps of:
(In the formula, R ₁ to R ₃ each independently represent a hydrogen atom or a substituent. M represents a metal atom or ion other than sodium. n represents a natural number from 4 to 8, and the n R ₁ to R ₃ are each the same.)
3. After the step of cyclizing the ligand, a step of replacing the central metal atom or ion of the cyclized ligand by a reaction in the presence of a metal salt different from the metal used in the step of cyclizing the ligand,
3. The method for synthesizing the organometallic complex according to claim 2.
4. Using the method for synthesizing the organometallic complex described in Item 3.
1. A method for synthesizing an organocopper complex comprising the steps of:

5. A film comprising the organometallic complex according to claim 1 .

6. An organic electronics device having an organic functional layer containing the organometallic complex according to claim 1.

7. An organic electroluminescence device comprising an organic functional layer containing the organometallic complex according to claim 1.

The above-mentioned means of the present invention can provide an organometallic complex having excellent optical or electronic functions and a method for synthesizing the same, a method for synthesizing an organocopper complex, a film containing the organometallic complex, and an organic electronics device, in particular an organic electroluminescent element having a reduced driving voltage and improved external extraction efficiency.

Although the mechanism by which the effects of the present invention are expressed or acted upon has not been clarified, it is speculated as follows.

Many macrocyclic compounds have excellent functions and are expected to be used in a wide range of fields, but there are only a limited number of simple and efficient methods for their production (synthesis). For this reason, research and development has been conducted into simple and efficient methods for the production of macrocyclic compounds.

In general, in the cyclization reaction for synthesizing macrocyclic compounds, the probability of the desired reaction points meeting each other is low, so it is easy to produce compounds in which the reactants are bonded in a chain shape, and it is difficult to produce cyclic compounds. The high dilution method described below is used to improve the yield of cyclic compounds, but it requires a large amount of solvent, which is technically and costly.

After extensive research, the inventors found that by using the template reaction described below, cyclic compounds can be synthesized in high yields while minimizing technical and cost burdens. In addition, by using this template reaction, an organometallic complex with a macrocyclic compound as a ligand is formed, and it was found that this organometallic complex has excellent optical and electronic functions. Furthermore, the metal species of the organometallic complex formed here is the specific metal species used in the template reaction, but it was found that by replacing the central metal species after synthesizing the macrocyclic compound, organometallic complexes using other metal species can be synthesized.

FIG. 1 is a schematic diagram showing an example of the configuration of an organic EL element. Schematic diagram showing the mechanism of charge flow and light emission in an organic EL element A schematic diagram showing an example of a solar cell made of a bulk heterojunction type organic photoelectric conversion element.

The organometallic complex of the present invention is characterized by having a structure represented by the above general formula (1).
This feature is a technical feature common to or corresponding to the following embodiments.

In an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, it is preferable that the organometallic complex has a structure represented by the above general formula (2), and more preferably has a structure represented by the above general formula (3).

The method for synthesizing an organometallic complex of the present invention is characterized by having a step of cyclizing a ligand by a coupling reaction in the presence of a metal atom or ion.

The organometallic complex of the present invention is also preferably contained in a film.

Furthermore, the organometallic complex of the present invention is suitably contained in an organic functional layer that constitutes an organic electronics device or an organic electroluminescence element.

The present invention, its components, and the forms and modes for implementing the present invention are described in detail below. Note that in this application, "~" is used to mean that the numerical values before and after it are included as the lower and upper limits.

<<Summary of the organometallic complex of the present invention>>
The organometallic complex of the present invention is characterized by having a structure represented by the following general formula (1):

(In the formula, M represents a metal atom or ion other than sodium. Each Ar ₁ independently represents a divalent aromatic hydrocarbon group or aromatic heterocyclic group, which may have a substituent or may be condensed. m represents a natural number of 0 to 6. When m represents a natural number of 2 to 6, m Ar _1s may all be the same or all different. Each Ar ₂ independently represents a divalent aromatic heterocyclic group having at least one nitrogen atom bonded to a metal atom or ion M, which may have a substituent or may be condensed. n represents a natural number of 1 to 6. When n represents a natural number of 2 to 6, n Ar _2s may all be the same or all different. In addition, m and n satisfy 4≦m+n≦12. The bonding order of m Ar _1s and n Ar _2s is not particularly limited.)

In the present invention, the term "complex" refers to an atomic group formed by directional three-dimensional bonding of several other atoms, ions, molecules, or atomic groups (these are called "ligands") around one atom or ion at the center. The bond is represented by the dotted line connecting the metal atom or ion M and _Ar2 in the above general formula (1).

When the central atom or ion of a complex is a metal atom or ion, it is called a "metal complex," and when the ligand is an organic compound, it is called an "organometallic complex."

The organometallic complex of the present invention is formed by binding a macrocyclic compound composed of Ar1 _{and Ar2 ,} or _Ar2 alone, to a metal atom or ion M. Specifically, as shown by the dotted line in the above general formula (1), one nitrogen atom in _Ar2 is bound to a metal atom or ion M. Although the mechanism of this binding cannot be determined, it is believed to be bound by a coordinate bond. Note that the atom in _Ar1 and the metal atom or ion M may or may not be bound.

The term "coordinate bond" refers to a chemical bond in which bonding electrons are provided to a molecular orbital from only one of the two atoms forming the bond. In the present invention, it is considered that the unshared electron pair of one nitrogen atom in _Ar2 is provided to form a coordinate bond with a metal atom or ion M.

In the organometallic complex of the present invention, the macrocyclic compound as the ligand has a cyclic structure, and one nitrogen atom in _Ar2 which forms a coordinate bond with a metal atom or ion M is located inside the cyclic structure. By having the nitrogen atom located inside the cyclic structure, it becomes easier for a metal atom or ion to be coordinated to the center of the cyclic structure.

As shown by the curve of the above general formula (1), the macrocyclic compound according to the present invention has a structure in which m Ar ₁ 's and n Ar _2's are mutually bonded via one single bond, and among them, Ar ₂ contributes to a coordinate bond with a metal atom or ion M. Ar ₂ may contain two or more nitrogen atoms, but only one of them contributes to a coordinate bond with a metal atom or ion M. Therefore, the number of coordinate bonds between the macrocyclic compound and a metal atom or ion M is n, and n can be a natural number from 1 to 6, so that the number of coordinate bonds in the organometallic complex of the present invention is within the range of 1 to 6. By changing the number of coordinate bonds, the properties of the organometallic complex of the present invention can be changed.

As an example, consider the case where the metal atom or ion M is Ni. The coordination number of the metal atom or ion is specific to each metal, and for Ni, the coordination number can be 4 or 6. When the coordination number is 4, all four coordination bonds are on a plane, so it is preferable from the standpoint of stability to have four coordination bonds with the macrocyclic compound. On the other hand, when the coordination number is 6, it is preferable from the standpoint of stability to have four coordination bonds with the macrocyclic compound and two coordination bonds with other ligands.

The coordination number of the metal atom or ion M is not limited, and it may have five coordination bonds with the macrocyclic compound and two coordination bonds with chloride ions, as in MO-9 shown in the method for producing an organometallic complex of the present invention described later.

The number of coordinate bonds in the organometallic complex of the present invention can be selected depending on the types of Ar ₁ and Ar ₂ and the type of the central metal atom or ion.

m and n satisfy the relationship 4≦m+n≦12. If the value of m+n is 3 or less, a ring structure cannot be formed, or even if a ring structure can be formed, the metal atom or ion cannot enter the hole in the center of the ring, making it impossible to form an organometallic complex. Also, if the value of m+n is 13 or more, the hole becomes too large, and the distance between the metal atom or ion M and the nitrogen atom becomes large, making it difficult to form a coordinate bond.

It is preferable that m and n are 4≦m+n≦8, and more preferably 5≦m+n≦6. When the value of m+n is within the above range, the macrocyclic compound has a planar structure with little steric hindrance, so that the π-electron conjugated system spreads easily throughout the molecule. In addition, the size of the vacancy is neither too small nor too large, so that the metal atom or ion M and the nitrogen atom can easily form a coordinate bond.

Each Ar ₁ independently represents a divalent aromatic hydrocarbon group or aromatic heterocyclic group, which may have a substituent and may be condensed. Ar ₁ may or may not be bonded to a metal atom or ion M. Furthermore, m represents a natural number of 0 to 6. When m represents a natural number of 2 to 6, m Ar _1s may be the same or different.

The term "divalent aromatic hydrocarbon group (also called "arylene group")" refers to a divalent group obtained by removing two hydrogen atoms directly bonded to carbon atoms constituting a ring from an aromatic hydrocarbon, and a divalent group to which a plurality of such divalent groups (e.g., 2 to 5) are bonded. The number of carbon atoms in a divalent aromatic hydrocarbon group is usually 6 to 60, preferably 6 to 30, and more preferably 6 to 18.

Examples of divalent aromatic hydrocarbon groups include phenylene, naphthalene-diyl, anthracene-diyl, phenanthrene-diyl, dihydrophenanthrene-diyl, naphthacene-diyl, fluorene-diyl, pyrene-diyl, perylene-diyl, and chrysene-diyl groups.

The term "divalent aromatic heterocyclic group" refers to a divalent group obtained by removing two hydrogen atoms from the hydrogen atoms directly bonded to the carbon atoms or heteroatoms that constitute the ring of an aromatic heterocyclic compound, and a divalent group to which multiple (e.g., 2 to 4) such divalent groups are bonded.

Examples of divalent aromatic heterocyclic groups (also referred to as "heteroarylene groups") include pyridylene groups (pyridine-diyl groups), pyridazine-diyl groups, imidazole-diyl groups, thienylene (thiophene-diyl groups), quinolylene groups (quinoline-diyl groups), isoquinolylene groups (isoquinoline-diyl groups), oxazole-diyl groups, thiazole-diyl groups, oxadiazole-diyl groups, benzothiazole-diyl groups, benzothiadiazole-diyl groups, phthalimido-diyl groups, thienothiazole-diyl groups, thiazolothiazole-diyl groups, thienothiophene-diyl groups, thienoxazole-diyl groups, dibenzofuran-diyl groups, dibenzothiophene-diyl groups, and carbazole-diyl groups.

These aromatic groups (aromatic hydrocarbon groups and aromatic heterocyclic groups) may have a substituent at any position.
Examples of the substituent include aromatic groups such as a phenyl group, a pyridyl group, a pyrrole group, a thienyl group, a furyl group, an imidazolyl group, a pyrimidyl group, a pyrazyl group, a pyridazyl group, and a triazinyl group, and condensed aromatic groups obtained by further condensing these groups (e.g., a naphthyl group, a quinolyl group, an imidazolyl group, an indoloimidazolyl group, an imidazoimidazolyl group, a dibenzothienyl group, a dibenzofuryl group, an azadibenzofuryl group, a benzimidazolyl group, a quinazolyl group, a benzopi group, and the like). Examples of substituents include a radinyl group, an alkyl group, a branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, and the like; a cyano group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an amino group, a carbonyl group, an acyl group, an ester group, a ureido group, a urethane group, and the like; and a halogen atom such as a fluorine atom or a chlorine atom. Among these, an aromatic group (including a condensate), an aliphatic group, a cyano group, an alkoxy group, and a fluorine atom are preferable.

Each Ar ₂ independently represents a divalent aromatic heterocyclic group having at least one nitrogen atom bonded to a metal atom or ion M, and may have a substituent or may be a condensed ring. n represents a natural number of 1 to 6. When n represents a natural number of 2 to 6, the n Ar ₂ may be the same or different.

Accordingly, Ar ₂ is a divalent aromatic heterocyclic group having a nitrogen atom, and examples thereof include a pyridylene group (pyridine-diyl group), a pyridazine-diyl group, an imidazole-diyl group, a quinolylene group (quinoline-diyl group), an isoquinolylene group (isoquinoline-diyl group), an oxazole-diyl group, a thiazole-diyl group, an oxadiazole-diyl group, a benzothiazole-diyl group, a benzothiadiazole-diyl group, a phthalimido-diyl group, a thienothiazole-diyl group, a thiazolothiazole-diyl group, a thienoxazole-diyl group, and a carbazole-diyl group.

The metal atom or ion M is not particularly limited as long as it is not sodium, and examples thereof include Li, K, Mg, Ca, Sr, Ti, Cr, Mn, Fe, Co, Ni, Cu, Pd, Ag, Rh, Pt, Au, La, Ce, Er, and ions thereof, among which Pd, Pt, Ag, Ni, Au, Rh, Ir, Co, Cu, and ions thereof.

There are no particular limitations on the metal atom or ion M, but the metal that can be coordinated is selected depending on the size of the vacancy in the macrocyclic compound. In addition, the properties of the organometallic complex that is formed vary greatly depending on the metal that is coordinated.

Examples of the organometallic complex of the present invention are shown below. However, the present invention is not limited to these. In the following chemical structural formula, a bond between one nitrogen atom in _Ar2 and a metal atom or ion M is represented by a dotted line, and a bond between an atom in _Ar1 and a metal atom or ion is represented by a solid line. The * mark in R of MO-20 indicates the bond site with the Eu atom.

<Method for producing organometallic complex of the present invention>
The method for producing (synthesizing) an organometallic complex of the present invention is characterized by having a step of cyclizing a ligand by a coupling reaction in the coexistence of a metal atom or ion.

The method for producing an organometallic complex of the present invention further includes 1) a step of cyclizing a ligand by a coupling reaction in the presence of a metal atom or ion, and, if necessary, 2) a step of replacing the central metal atom or ion.

Normally, when attempting to synthesize a macrocyclic compound, the probability of the desired reaction points meeting each other is low, so compounds in which the reactants are linked in a chain are likely to be produced, and it is difficult to produce a cyclic compound. For this reason, a method (high dilution method) is used in which a much larger amount of solvent than usual is used to relatively increase the probability of the desired reaction points meeting each other, thereby improving the yield of the cyclic compound. However, the need for a large amount of solvent imposes a large technical and cost burden.

The organometallic complex of the present invention can synthesize cyclic compounds in high yields by inducing a coupling reaction under template reaction without using such a high dilution method.

The term "template reaction" refers to a reaction in which, in a method for synthesizing an organic compound, a reactant forms a coordinate bond with a metal atom or ion by coexistence of the metal atom or ion, and synthesis proceeds in a positional state suitable for cyclization. In the present invention, it is considered that the unshared electron pair of one nitrogen atom in _Ar2 in the above general formula (1) is provided and forms a coordinate bond with the metal atom or ion M.

However, since the template reaction only occurs in the presence of certain metal atoms or ions such as Ni or Pd, it is possible to synthesize organometallic complexes using other metal atoms or ions by cyclizing the ligand through a coupling reaction in the presence of metal atoms or ions such as Ni or Pd, and then replacing the central metal atom or ion.

An example of a method for producing the organometallic complex of the present invention is described below.

(Step of Cyclizing the Ligand by Coupling Reaction in the Presence of Metal Atoms or Ions)
To 2,2'-bipyridyl (23.4 g, 150.0 mmol), 1,5-cyclooctadiene (18.4 mL, 150.0 mmol), bis(1,5-cyclooctadiene)nickel(0) (41.3 g, 150.0 mmol), DMF (62.5 mL) and toluene (62.5 mL) were added and stirred at 80°C for 30 minutes. A solution of compound 2 (3.78 g, 15.0 mmol) in toluene (250 mL) was added dropwise to the mixture over 1 hour and stirring was continued at 80°C for another 16 hours. The reaction mixture was cooled to room temperature, 2M hydrochloric acid (300 mL) was added and stirred vigorously overnight under air. Extraction was performed with CH ₂ Cl ₂ (400 mL×3), and the organic layer was washed with saturated brine (200 mL), dried over Na ₂ SO ₄ , and then concentrated in vacuum. The crude product was passed through a silica gel short pass (eluent: CHCl ₃ :MeOH=20:1) and further purified by GPC (YMC T30000, T4000, T2000 columns, solvent: CHCl ₃ ) to obtain compound MO-9 as a yellow solid in a yield of 57% (1.77 g, 1.71 mmol). Mass spectrometry (MALDI-TOF MS) confirmed that the product was compound MO-9.

(Step of replacing central metal atom or ion)
Copper complex MO-11 was produced by synthesis in exactly the same manner as in Example 1, except that 10 equivalents of CuCl (14.9 g, 150 mmol) was added to a DMF/toluene solution of 2,2'-bipyridyl, 1,5-cyclooctadiene, and bis(1,5-cyclooctadiene)nickel(0). Mass spectrometry revealed that the product was compound MO-11.

<Film of the present invention>
The organometallic complex of the present invention has excellent optical or electronic functions, and can be used in various applications by forming it into a film, such as luminous plastics, luminescent color control films for displays, temperature-sensitive sheets, etc. The organometallic complex of the present invention has high stability because it can utilize thermodynamic stability by using a cyclic ligand, and is particularly useful as a color filter for displays.

The thickness of the film of the present invention is not particularly limited, but is preferably within the range of 10 to 1500 μm, and more preferably within the range of 20 to 1000 μm.

The film of the present invention may be formed as a single layer film on a substrate having a release layer and then peeled off. It may also be formed on a substrate and used as a laminate film having various functional layers.

The film of the present invention can be produced by blending an organometallic complex with a plastic material. The blending amount of the organometallic complex is preferably within the range of 1 to 50% by mass with respect to the total mass of the plastic material. The plastic material is not particularly limited, and examples thereof include polyethylene resin, polypropylene resin, polyvinyl chloride resin, urea resin, fluororesin, polyester resin, polyamide resin, polyacetal resin, polycarbonate resin, polyarylate resin, polysulfone resin, polyphenylene sulfide resin, polyethersulfone resin, polyarylsulfone resin, polytetrafluoroethylene resin, phenol resin, unsaturated polyester resin, epoxy resin, polyimide resin, polyamideimide resin, etc.

The method for producing the film is not particularly limited, and the film can be produced by a conventionally known method. The method described in the organic functional layer formation step in the method for producing an organic electroluminescent element described below may also be used.

A film can also be produced by polymerizing the macrocyclic compound, which is a ligand. A method for polymerizing a macrocyclic compound can be used that is described in a known synthesis method (Non-Patent Document: Polymer Chemistry, Synthesis, by Nakajo Yoshiki et al., Maruzen Publishing, published in June 2010). For example, there is a method in which a polymerizable substituent such as a vinyl group or an epoxy group is introduced into the molecule in advance, and a polymer is obtained by chain polymerization of the introduced substituent, or a method in which a halogen substituent (also called a "halogeno group") is introduced into the molecule, and condensation polymerization is carried out by dehalogenating the introduced substituent.

<Organic electronic device of the present invention>
The organic electronics device of the present invention is characterized by having an organic functional layer containing the organometallic complex of the present invention. The organometallic complex of the present invention has excellent optical or electronic functions, and its use as a material constituting the organic functional layer can improve the performance of the organic electronics device.

Examples of organic electronic devices include organic electroluminescence elements, organic solar cells, and organic transistors. Below, we will explain organic electroluminescence elements and organic solar cells.

[Organic electroluminescence element]
The organic electronics device of the present invention is characterized by having an organic functional layer containing the organometallic complex of the present invention. The organometallic complex of the present invention has excellent optical and electronic functions and can be suitably used as a material for an organic electroluminescence element (hereinafter also referred to as an "organic EL element").

Representative device configurations for an organic EL device produced using the organometallic complex of the present invention include the following configurations. Among them, the configuration (vii) is preferably used, but is not limited thereto.
(i) anode/light-emitting layer/cathode (ii) anode/light-emitting layer/electron transport layer/cathode (iii) anode/hole transport layer/light-emitting layer/cathode (iv) anode/hole transport layer/light-emitting layer/electron transport layer/cathode (v) anode/hole transport layer/light-emitting layer/electron transport layer/electron injection layer/cathode (vi) anode/hole injection layer/hole transport layer/light-emitting layer/electron transport layer/cathode (vii) anode/hole injection layer/hole transport layer/(electron blocking layer/)light-emitting layer/(hole blocking layer/)electron transport layer/electron injection layer/cathode

In the organic EL element of the present invention, the light-emitting layer is composed of a single layer or multiple layers. When multiple light-emitting layers are used, a non-light-emitting intermediate layer may be provided between each of the light-emitting layers. If necessary, a hole-blocking layer (also called a "hole-blocking layer") or an electron-injecting layer (also called a "cathode buffer layer") may be provided between the light-emitting layer and the cathode, and an electron-blocking layer (also called an "electron-blocking layer") or a hole-injecting layer (also called an anode buffer layer) may be provided between the light-emitting layer and the anode.

The electron transport layer according to the present invention is a layer that has the function of transporting electrons, and in a broad sense, the electron transport layer also includes an electron injection layer and a hole blocking layer. It may also be composed of multiple layers.

The hole transport layer according to the present invention is a layer that has the function of transporting holes, and in a broad sense, the hole injection layer and the electron blocking layer are also included in the hole transport layer. It may also be composed of multiple layers. In the above representative element configuration, the layers excluding the anode and cathode are called "organic functional layers."

The organic EL element of the present invention has an organic functional layer that contains the above-mentioned organometallic complex. That is, in the configurations (i) to (vii), the above-mentioned organometallic complex may be contained in any layer other than the anode and the cathode.

Figure 1 is an example of the configuration of an organic EL element, and is a schematic diagram corresponding to the configuration listed in (vi). In Figure 1, the hole injection layer 4, the hole transport layer 5, the light-emitting layer 6, and the electron transport layer 7 are organic functional layers F.

2 is a schematic diagram showing the mechanism of charge flow and light emission in an organic EL element. When a voltage is applied to the organic EL element 1, electrons (e ⁻ ) are injected from the cathode 9 to the electron injection layer 8, and holes (h ⁺ ) are injected from the anode 3 to the hole injection layer 4.

The electrons and holes are then transported to the adjacent organic layers on the opposite side of the electrode, the electron transport layer 7 and the hole transport layer 5, respectively.

Finally, the electrons and holes that meet in the light-emitting layer 6 recombine R to generate excitons, and the light (fluorescence/phosphorescence) L emitted when these return from the excited state to the ground state is used as a light-emitting element, which is an organic EL element. In Figure 2, the layers from the hole injection layer 4 to the electron injection layer 8 are the organic functional layer F.

The organic EL element of the present invention may also be an element having a so-called tandem structure in which a plurality of light-emitting units, each of which has at least one light-emitting layer, are stacked. Even in the tandem structure, all layers except the anode and cathode are referred to as the "organic functional layer."

A typical element configuration of the tandem structure is, for example, as follows.
Anode/first light-emitting unit/second light-emitting unit/third light-emitting unit/cathode Anode/first light-emitting unit/intermediate layer/second light-emitting unit/intermediate layer/third light-emitting unit/cathode

Here, the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit may all be the same or different. Also, two of the light-emitting units may be the same and the remaining one may be different. Furthermore, the third light-emitting unit may not be present, while a further light-emitting unit or intermediate layer may be provided between the third light-emitting unit and the electrode.

The multiple light-emitting units may be stacked directly or via an intermediate layer. The intermediate layer is generally called an intermediate electrode, intermediate conductive layer, charge generation layer, electron extraction layer, connection layer, or intermediate insulating layer. Any known material and configuration can be used as long as the layer has the function of supplying electrons to the adjacent layer on the anode side and holes to the adjacent layer on the cathode side.

The material used for the intermediate layer is not particularly limited, and examples thereof include conductive inorganic compound layers such as ITO (indium tin oxide), IZO (indium zinc oxide), _ZnO2 , TiN, ZrN, HfN, _TiOx , VOx, _CuI , InN, GaN, _CuAlO2 , _CuGaO2 , _SrCu2O2 , _LaB6 , _RuO2 , and Al, _bilayer films such as Au/ _Bi2O3 , and multilayer films such as _SnO2 /Ag/ _SnO2 , ZnO _/ Ag/ZnO, _Bi2O3 /Au/ _Bi2O3 , _TiO2 / _TiN / _TiO2 , _{and TiO2} /ZrN/ _TiO2 , and C. Examples of such conductive organic compounds include fullerenes such as ₆₀ and the like, conductive organic layers such as oligothiophenes, and conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, and metal-free porphyrins.

Preferred configurations within the light-emitting unit are not particularly limited, and include, for example, configurations (i) to (vii) listed above as typical element configurations, excluding the anode and cathode.

Specific examples of tandem-type organic EL elements are not particularly limited, and include, for example, U.S. Pat. No. 6,337,492, U.S. Pat. No. 7,420,203, U.S. Pat. No. 7,473,923, U.S. Pat. No. 6,872,472, U.S. Pat. No. 6,107,734, U.S. Pat. No. 6,337,492, International Publication No. 2005/009087, JP 2006-228712 A, JP 2006-24791 A, JP 2006-49393 A, JP 2006-49394 A, and JP 2006-49396 A. , JP 2011-96679 A, JP 2005-340187 A, JP 4711424 A, JP 3496681 A, JP 3884564 A, JP 4213169 A, JP 2010-192719 A, JP 2009-076929 A, JP 2008-078414 A, JP 2007-059848 A, JP 2003-272860 A, JP 2003-045676 A, WO 2005/094130 A, and the like.

<1. Components of an organic electroluminescence device>
Each layer constituting the organic EL element of the present invention will be described below.

(Light Emitting Layer)
The term "light-emitting layer" refers to a layer that provides a site where electrons and holes injected from an electrode or an adjacent layer recombine and emit light via excitons. The light-emitting portion may be within the light-emitting layer or at the interface between the light-emitting layer and an adjacent layer.

There may be multiple layers having the same emission spectrum or maximum emission wavelength. In this case, it is preferable to have a non-emissive intermediate layer between each of the light-emitting layers. The structure of the light-emitting layer according to the present invention is not particularly limited as long as it satisfies the requirements stipulated in the present invention.

The total thickness of the light-emitting layers is not particularly limited, but from the viewpoints of homogeneity of the layer to be formed, prevention of application of unnecessary high voltage during light emission, and improvement of stability of the emitted color with respect to the driving current, it is preferably within the range of 2 nm to 5 μm, more preferably within the range of 2 to 500 nm, and even more preferably within the range of 5 to 200 nm. Note that, if a non-light-emitting intermediate layer is present between the light-emitting layers, the thickness of the intermediate layer is also included in the total thickness of the light-emitting layers.

The light-emitting layer preferably contains a light-emitting dopant (hereinafter also referred to as a "light-emitting dopant compound", "dopant compound", or simply "dopant") and a host compound (hereinafter also referred to as a "matrix material", "light-emitting host compound", or simply "host"), and it is preferable that light is emitted from the light-emitting material.

(1) Light-emitting dopant As the light-emitting dopant, a fluorescent dopant (hereinafter also referred to as a "fluorescent dopant" or a "fluorescent compound") and a phosphorescent dopant (hereinafter also referred to as a "phosphorescent dopant" or a "phosphorescent compound") are preferably used. In the present invention, it is particularly preferable to use a thermally activated delayed fluorescent compound (TADF) among the phosphorescent dopants and fluorescent dopants.

The concentration of the light-emitting dopant in the light-emitting layer can be determined arbitrarily based on the particular dopant used and the requirements of the device, and may be uniform in concentration or have any concentration distribution across the thickness of the light-emitting layer.

In addition, multiple types of light-emitting dopants may be used in combination, or dopants with different structures may be combined, or a fluorescent dopant may be combined with a phosphorescent dopant. This allows any emission color to be obtained.

The color emitted by an organic EL element is determined by the color measured using a spectroradiometer CS-1000 (manufactured by Konica Minolta, Inc.) and applied to the CIE chromaticity coordinates in Figure 4.16 on page 108 of "New Color Science Handbook" (edited by the Color Science Association of Japan, University of Tokyo Press, 1985).

In the present invention, it is also preferable that the light-emitting layer or layers contain a plurality of light-emitting dopants that emit light of different colors and emit white light.
The combination of light-emitting dopants that exhibit white color is not particularly limited, and examples thereof include combinations of blue and orange, and blue, green and red.
The white color in the present invention is not particularly limited, and may be a white color leaning toward orange or a white color leaning toward blue. However, when the 2-degree viewing angle front luminance is measured by the above-mentioned method, it is preferable that the chromaticity in the CIE1931 color system at 1000 cd/ ^m2 is within the range of x=0.39±0.09, y=0.38±0.08.

(1.1) Phosphorescent Dopant The phosphorescent dopant according to the present invention (hereinafter, also referred to as "phosphorescent dopant") will be described.
A phosphorescent dopant is a compound in which light emission from an excited triplet state is observed, and specifically, is defined as a compound that emits phosphorescence at room temperature (25° C.) and has a phosphorescence quantum yield of 0.01 or more at 25° C., with the phosphorescence quantum yield being preferably 0.1 or more.

The phosphorescence quantum yield can be measured by the method described in Spectroscopy II, 4th Edition, Experimental Chemistry Lectures 7, p. 398 (1992 edition, Maruzen). The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescent dopant according to the present invention may be any solvent that achieves the phosphorescence quantum yield (0.01 or more).

There are two principles for the emission of phosphorescent dopants. One is the energy transfer type, in which carrier recombination occurs on the host compound to which the carriers are transported, generating an excited state of the host compound, and this energy is transferred to the phosphorescent dopant, resulting in emission from the phosphorescent dopant. The other is the carrier trap type, in which the phosphorescent dopant acts as a carrier trap, carrier recombination occurs on the phosphorescent dopant, resulting in emission from the phosphorescent dopant. In either case, the condition is that the energy of the excited state of the phosphorescent dopant is lower than the energy of the excited state of the host compound.

In the present invention, the above-mentioned organometallic complex (the organometallic complex having the structure represented by the above general formula (1)) can be used as the phosphorescent dopant. Among them, an organometallic complex in which the central metal atom or ion M is Ir or Pt is preferable.

In addition to the above metal complexes, known phosphorescent dopants used in the light-emitting layer of an organic EL element can be used. The above metal complexes may also be used in combination with known phosphorescent dopants. Specific examples of known phosphorescent dopants include compounds described in the following documents:

Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19,739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17,1059 (2005), WO 2009/100991, WO 2008/101842, WO 2003/040257, U.S. Patent Publication No. 2006/835469, U.S. Patent Publication No. 2006/0202194, U.S. Patent Publication No. 2007/0087321, U.S. Patent Publication No. 2005/0244673, Inorg. Chem. 40,1704 (2001), Chem. Mater. 16,2480 (2004), Adv. Mater. 16,2003 (2004), Angew. Chem. Int. Ed. 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42,1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, U.S. Patent Publication No. 2002/0034656, U.S. Patent No. 7,332,232, U.S. Patent Publication No. 2009/0108737, U.S. Patent Publication No. 2009/0039776, U.S. Patent No. 6,921,915, U.S. Patent No. 6,687,266, U.S. Patent Publication No. 2007/01903 No. 59, U.S. Patent Publication No. 2006/0008670, U.S. Patent Publication No. 2009/0165846, U.S. Patent Publication No. 2008/0015355, U.S. Patent No. 7,250,226, U.S. Patent No. 7,396,598, U.S. Patent Publication No. 2006/0263635, U.S. Patent Publication No. 2003/0138657, U.S. Patent Publication No. 2003/0152802, U.S. Patent No. 7,090,928, Angew. Chem. Int. Ed. 47,1 (2008), Chem. Mater. 18,5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Appl. Phys. Lett. 74, 1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/009024, International Publication No. 2006/056418, International Publication No. 2005/019373, International Publication No. 2005/123873, International Publication No. 2007/004380, International Publication No. 2006/082742, U.S. Patent Publication No. 2006/0251923, U.S. Patent Publication No. 2005/0260441, U.S. US Patent No. 7,393,599, US Patent No. 7,534,505, US Patent No. 7,445,855, US Patent Publication No. 2007/0190359, US Patent Publication No. 2008/0297,033, US Patent No. 7,338,722, US Patent Publication No. 2002/0134,984, US Patent No. 7,279,704, US Patent Publication No. 2006/098120, US Patent Publication No. 2006 WO 2005/076380, WO 2010/032663, WO 2008/140115, WO 2007/052431, WO 2011/134013, WO 2011/157339, WO 2010/086089, WO 2009/113646, WO 2012/020327, WO 2011/05140 4, International Publication No. 2011/004639, International Publication No. 2011/073149, U.S. Patent Publication No. 2012/228583, U.S. Patent Publication No. 2012/212126, JP 2012-069737 A, JP 2012-195554 A, JP 2009-114086 A, JP 2003-81988 A, JP 2002-302671 A, JP 2002-363552 A, etc.

(1.2) Fluorescent Dopant The fluorescent dopant (hereinafter, also referred to as "fluorescent dopant") according to the present invention will be described.
The fluorescent dopant is a compound capable of emitting light from an excited singlet state, and is not particularly limited as long as light emission from the excited singlet state can be observed.

In the present invention, the above-mentioned organometallic complex (the organometallic complex having the structure represented by the above general formula (1)) can be used as the fluorescent dopant. Among them, an organometallic complex in which the central metal atom or ion M is Cu or Eu is preferable.

In addition to the above metal complexes, known fluorescent dopants used in the light-emitting layer of an organic EL element can be used. The above metal complexes may also be used in combination with known fluorescent dopants. Specific examples of known fluorescent dopants include compounds described in the following documents:

Fluorescent dopants according to the present invention include, for example, anthracene derivatives, pyrene derivatives, chrysene derivatives, fluoranthene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, arylamine derivatives, boron complexes, coumarin derivatives, pyran derivatives, cyanine derivatives, croconium derivatives, squarium derivatives, oxobenzanthracene derivatives, fluorescein derivatives, rhodamine derivatives, pyrylium derivatives, perylene derivatives, polythiophene derivatives, and rare earth complex compounds.

A thermally activated delayed fluorescent compound may also be used. Specific examples include compounds described in International Publication No. 2011/156793, JP-A No. 2011-213643, JP-A No. 2010-93181, etc., but the present invention is not limited to these.

(2) Host Compound The host compound according to the present invention is a compound that mainly injects and transports charges in the light-emitting layer, and does not substantially emit light by itself in the organic EL device. The host compound is preferably a compound having a phosphorescence quantum yield of phosphorescence emission at room temperature (25° C.) of less than 0.1, and more preferably a compound having a phosphorescence quantum yield of less than 0.01.

The content of the host compound is preferably 20% by mass or more based on the total mass of the compounds contained in the light-emitting layer. The excited state energy of the host compound is preferably higher than the excited state energy of the light-emitting dopant contained in the same layer.

In the present invention, the above-mentioned organometallic complex (the organometallic complex having the structure represented by the above general formula (1)) can be used as the host compound. Among them, an organometallic complex in which the central metal atom or ion M is Ir is preferable.

In addition to the above metal complexes, known host compounds used in the light-emitting layer of organic EL elements can be used. The above metal complexes can also be used in combination with known host compounds.

The host compound may be a low molecular weight compound, a polymeric compound having a repeating unit, or a compound having a reactive group such as a vinyl group or an epoxy group. The host compound may be used alone or in combination with multiple types. By using multiple types of host compounds in combination, the charge transfer can be adjusted, and the efficiency of the organic EL element can be increased.

In addition, from the viewpoint of having hole transporting ability or electron transporting ability, preventing the emission wavelength from becoming longer, and further enabling the organic EL element to operate stably against heat generation during high temperature operation or element operation, it is preferable that the host compound has a high glass transition temperature (Tg). The Tg is preferably 90°C or higher, and more preferably 120°C or higher. Here, the glass transition point (Tg) is a value determined by a method conforming to JIS-K-7121 using DSC (Differential Scanning Calorimetry).

Specific examples of known host compounds include compounds described in the following documents, but the present invention is not limited to these.
JP 2001-257076 A, JP 2002-308855 A, JP 2001-313179 A, JP 2002-319491 A, JP 2001-357977 A, JP 2002-334786 A, JP 2002-8860 A, JP 2002-334787 A, JP 2002-15871 A, JP 2002-334788 A, JP 2002-43056 A, JP 2002-334789 A, JP 2002-75645 A, JP 2002-338579 A, JP 2002-1 JP-A-05445, JP-A-2002-343568, JP-A-2002-141173, JP-A-2002-352957, JP-A-2002-203683, JP-A-2002-363227, JP-A-2002-231453, JP-A-2003-3165, JP-A-2002-234888, JP-A-2003-27048, JP-A-2002-255934, JP-A-2002-260861, JP-A-2002-280183, JP-A-2002-299060, JP-A-2002-302516 JP 2002-305083 A, JP 2002-305084 A, JP 2002-308837 A, U.S. Patent Publication No. 2003/0175553 A, U.S. Patent Publication No. 2006/0280965 A, U.S. Patent Publication No. 2005/0112407 A, U.S. Patent Publication No. 2009/0017330 A, U.S. Patent Publication No. 2009/0030202 A, U.S. Patent Publication No. 2005/0238919 A, International Publication No. 2001/039234 A, International Publication No. 2009/021126 A, International Publication No. 2008 /056746, WO 2004/093207, WO 2005/089025, WO 2007/063796, WO 2007/063754, WO 2004/107822, WO 2005/030900, WO 2006/114966, WO 2009/086028, WO 2009/003898, WO 2012/023947, JP 2008-074939 A, JP 2007-254297 A, EP 2034538 specification and the like.

As an example of the above, the host compound used in the present invention preferably has a partial structure of the general formula (a) or (b) shown below, and may have both partial structures.

(Heteroaromatic ring structure)

In the formula, C represents a carbon atom, and R ₁ to R ₁₂ represent a hydrogen atom or a substituent. At least one of CR ₁ to CR ₄ or CR ₅ R ₆ , or at least one of CR ₇ to CR _12, is substituted with a nitrogen atom, an oxygen atom, or a sulfur atom, and is substituted with a hydrogen atom or a substituent so as to satisfy the valence of each atom. Adjacent CR groups may form a ring. Examples of structures that satisfy this structure include pyrrole, furan, thiophene, imidazole, pyrazole, oxazole, isoxazole, thiazole, pyridine, quinoline, coumarin, benzofuran, indole, acridine, phenoxazine, carbazole, carboline, and dibenzofuran structures.

(Triarylamine structure)

Ar ₁ to Ar ₃ each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group, which may have a substituent.

(Electron Transport Layer)
The term "electron transport layer" refers to a layer made of a material having a function of transporting electrons and having a function of transmitting electrons injected from the cathode to the light emitting layer.
The total thickness of the electron transport layer is not particularly limited, but is preferably within the range of 2 nm to 5 μm, more preferably within the range of 2 to 500 nm, and even more preferably within the range of 5 to 200 nm.

The material used in the electron transport layer (hereinafter also referred to as "electron transport material") may have either the ability to inject or transport electrons or the ability to block holes.

In the present invention, the above-mentioned organometallic complex (the organometallic complex having the structure represented by the above general formula (1)) can be used as the electron transport material. Among them, an organometallic complex in which the central metal atom or ion M is Ir or Zn is preferable.

In addition to the above metal complexes, known materials used in the electron transport layer of organic EL elements can be used. The above metal complexes can also be used in combination with known materials.

Examples of known electron transport materials include nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one or more of the carbon atoms constituting the carbazole ring are replaced with nitrogen atoms), pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, pyridazine derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, azatriphenylene derivatives, oxazole derivatives, thiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, benzimidazole derivatives, benzoxazole derivatives, benzothiazole derivatives, etc.), dibenzofuran derivatives, dibenzothiophene derivatives, silole derivatives, aromatic hydrocarbon derivatives (naphthalene derivatives, anthracene derivatives, triphenylene, etc.), etc.

In addition, metal complexes having a quinolinol skeleton or a dibenzoquinolinol skeleton in the ligand, such as tris(8-quinolinol)aluminum ( _Alq ), tris(5,7-dichloro-8-quinolinol)aluminum, tris(5,7-dibromo-8-quinolinol)aluminum, tris(2-methyl-8-quinolinol)aluminum, tris(5-methyl-8-quinolinol)aluminum, bis(8-quinolinol)zinc (Znq), and metal complexes in which the central metal of these metal complexes is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb can also be used as the electron transport material.

In addition, metal-free and metal phthalocyanines, and those in which the terminals are substituted with an alkyl group, a sulfonic acid group, etc. can also be preferably used as the electron transport material. Distyrylpyrazine derivatives exemplified as materials for the light-emitting layer can also be used as the electron transport material, and inorganic semiconductors such as n-type Si and n-type SiC can also be used as the electron transport material, as in the hole injection layer and hole transport layer.
Furthermore, it is also possible to use polymer materials in which these materials are introduced into the polymer chain or in which these materials form the polymer main chain.

The electron transport layer according to the present invention may be doped with a dopant as a guest material to form an electron transport layer with high n-type (electron-rich) properties. Examples of the dopant include n-type dopants such as metal complexes and metal compounds such as metal halides. Specific examples of electron transport layers having such a configuration include those described in Japanese Patent Application Laid-Open Nos. 4-297076, 10-270172, 2000-196140, and 2001-102175, and J. Appl. Phys. 95, 5773 (2004).

Specific examples of known electron transport materials include compounds described in the following documents, but the present invention is not limited thereto.
U.S. Patent No. 6,528,187, U.S. Patent No. 7,230,107, U.S. Patent Publication No. 2005/0025993, U.S. Patent Publication No. 2004/0036077, U.S. Patent Publication No. 2009/011 5316, US Patent Publication No. 2009/0101870, US Patent Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132085, Appl. Phys. Lett. 75, 4 (1999), Appl. Phys. Lett. 79, 449 (2001), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81,162 (2002), Appl. Phys. Lett. 79,156 (2001), U.S. Pat. No. 7,964,293, U.S. Patent Publication No. 2009/030202, International Publication No. WO 2004/080975, International Publication No. WO 2004/063159, International Publication No. WO 2005/085387, International Publication No. WO 2006/067931, International Publication No. WO 2007/086552, International Publication No. WO 2008/114690, International Publication No. WO 2009/069442, International Publication No. WO 2009/066779, International Publication No. WO 2009/054253, International Publication No. WO 2011/08 6935, WO 2010/150593, WO 2010/047707, EP2311826, JP 2010-251675 A, JP 2009-209133 A, JP 2009-124114 A, JP 2008-277810 A, JP 2006-156445 A, JP 2005-340122 A, JP 2003-45662 A, JP 2003-31367 A, JP 2003-282270 A, WO 2012/115034 A, and the like.

Among these, the electron transport material of the present invention is more preferably a pyridine derivative, a pyrimidine derivative, a pyrazine derivative, a triazine derivative, a dibenzofuran derivative, a dibenzothiophene derivative, a carbazole derivative, an azacarbazole derivative, or a benzimidazole derivative.
The electron transporting materials may be used alone or in combination of two or more kinds.

(Hole Blocking Layer)
The term "hole blocking layer" refers to a layer having the function of an electron transport layer in a broad sense. It is preferably made of a material that has the function of transporting electrons but has a small ability to transport holes, and can improve the probability of recombination of electrons and holes by transporting electrons while blocking holes.
The above-mentioned configuration of the electron transport layer can be used as a hole blocking layer, if necessary. The hole blocking layer is preferably provided adjacent to the cathode side of the light emitting layer.

The thickness of the hole blocking layer is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm.

The materials used in the hole blocking layer are preferably the materials used in the electron transport layer and host compound described above.

(Electron Injection Layer)
The term "electron injection layer (also referred to as "cathode buffer layer")" refers to a layer provided between the cathode and the light-emitting layer in order to reduce driving voltage and improve luminance, and is described in detail in "Electrode Materials" (pp. 123-166, Chapter 2, Volume 2) of "Organic EL Elements and Their Industrialization Frontiers" (published by NTS Corporation on Nov. 30, 1998).

The electron injection layer is formed between the cathode and the light-emitting layer, or between the cathode and the electron transport layer, as described above, as necessary. The electron injection layer is preferably a thin film, and although it depends on the material, the thickness is preferably within the range of 0.1 to 5 nm. It may also be a non-uniform film in which the constituent materials are intermittently present.

In the present invention, the above-mentioned organometallic complex (the organometallic complex having the structure represented by the above general formula (1)) can be used as the material used in the electron injection layer. Among them, an organometallic complex in which the central metal atom or ion M is Ir or Zn is preferable.

In addition to the above metal complexes, known materials used in the electron injection layer of organic EL elements can be used. The above metal complexes can also be used in combination with known materials.

The electron injection layer is also described in detail in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, etc., and specific examples of materials preferably used in the electron injection layer include metals such as strontium and aluminum, alkali metal compounds such as lithium fluoride, sodium fluoride, potassium fluoride, etc., alkaline earth metal compounds such as magnesium fluoride and calcium fluoride, metal oxides such as aluminum oxide, and metal complexes such as lithium 8-hydroxyquinolate (Liq). The above-mentioned electron transport materials can also be used. These materials may be used alone or in combination.

(Hole transport layer)
The term "hole transport layer" refers to a layer made of a material having a function of transporting holes and having a function of transmitting holes injected from the anode to the light emitting layer.
The total thickness of the hole transport layer is not particularly limited, but is preferably in the range of 5 nm to 5 μm, more preferably in the range of 2 to 500 nm, and even more preferably in the range of 5 to 200 nm.

The material used in the hole transport layer (hereinafter referred to as the hole transport material) may have either hole injection or transport properties, or electron barrier properties.

In the present invention, the above-mentioned organometallic complex (the organometallic complex having the structure represented by the above general formula (1)) can be used as the hole transport material. Among them, an organometallic complex in which the central metal atom or ion M is Ir or Cu is preferable.

In addition to the above metal complexes, known materials used in the hole transport layer of organic EL elements can be used. The above metal complexes can also be used in combination with known materials.

Examples of known hole transport materials include porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polyvinylcarbazole, polymeric materials or oligomers with aromatic amines introduced into the main chain or side chain, polysilanes, conductive polymers or oligomers (e.g. PEDOT:PSS, aniline-based copolymers, polyaniline, polythiophene, etc.), etc.

Examples of triarylamine derivatives include benzidine types such as α-NPD, starburst types such as MTDATA, and compounds having fluorene or anthracene in the triarylamine linking core portion. Hexaazatriphenylene derivatives such as those described in JP-T-2003-519432 and JP-A-2006-135145 can also be used.

It is also possible to use a highly p-type hole transport material doped with impurities, such as those described in JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Appl. Phys., 95, 5773 (2004), etc.

Also usable are so-called p-type hole transport materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in JP-A-11-251067 and the document by J. Huang et al. (Applied Physics Letters 80 (2002), p. 139). Furthermore, ortho-metalated organometallic complexes having Ir or Pt as the central metal, as typified by Ir(ppy) ₃ , are also preferably used.

Among them, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, azatriphenylene derivatives, organometallic complexes, polymeric materials or oligomers in which aromatic amines are introduced into the main chain or side chain, etc. are preferably used. Specific examples include the compounds described in the documents listed above as well as the following documents, but the present invention is not limited to these. The hole transport material may be used alone or in combination of multiple types.

Appl. Phys. Lett. 69, 2160 (1996), J. Lumin. 72-74, 985 (1997), Appl. Phys. Lett. 78, 673 (2001), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 51, 913 (1987), Synth. Met. 87, 171 (1997), Synth. Met. 91, 209 (1997), Synth. Met. 111,421 (2000), SID Symposium Digest,37,923 (2006), J. Mater. Chem. 3,319 (1993), Adv. Mater. 6,677 (1994), Chem. Mater. 15,3148 (2003), U.S. Patent Publication No. 2003/0162053, U.S. Patent Publication No. 2002/0158242, U.S. Patent Publication No. 2006/0240279, U.S. Patent Publication No. 2008/0220265, U.S. Patent No. 5,061,569, WO 2007/002683, WO 2009/018009, EP 650955, U.S. These include Japanese Patent Publication No. 2008/0124572, U.S. Patent Publication No. 2007/0278938, U.S. Patent Publication No. 2008/0106190, U.S. Patent Publication No. 2008/0018221, International Publication No. 2012/115034, JP 2003-519432 A, JP 2006-135145 A, and U.S. Patent Application No. 13/585981.

(Electron Blocking Layer)
The term "electron blocking layer" refers, in a broad sense, to a layer having the function of a hole transport layer, and is preferably made of a material that has the function of transporting holes but has little ability to transport electrons, and can improve the probability of recombination of electrons and holes by blocking electrons while transporting holes.
If necessary, the above-mentioned hole transport layer may be used as an electron blocking layer according to the present invention. The electron blocking layer is preferably provided adjacent to the anode side of the light emitting layer.

The thickness of the electron blocking layer is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm.

In the present invention, the above-mentioned organometallic complex (organometallic complex having a structure represented by the above general formula (1)) can be used as the material used in the electron blocking layer. Among them, organometallic complexes in which the central metal atom or ion M is Ir, Fe, or Cu are preferred.

In addition to the above metal complexes, known materials used in the electron blocking layer of organic EL elements can be used. The above metal complexes may also be used in combination with known materials. As materials used in the electron blocking layer, materials used in the hole transport layer are preferably used, and materials used as the host compounds are also preferably used in the electron blocking layer.

(Hole Injection Layer)
The "hole injection layer (also referred to as "anode buffer layer")" refers to a layer provided between the anode and the light-emitting layer in order to reduce the driving voltage and improve the luminance of emitted light, and is described in detail in "Electrode Materials" (pp. 123-166, Chapter 2, Volume 2) of "Organic EL Elements and Their Industrialization Frontiers" (published by NTS Corporation on Nov. 30, 1998).
The hole injection layer is, if necessary, formed between the anode and the light emitting layer or between the anode and the hole transport layer as described above.

In the present invention, the above-mentioned organometallic complex (organometallic complex having a structure represented by the above general formula (1)) can be used as the material used in the hole injection layer. Among them, organometallic complexes in which the central metal atom or ion M is Ir, Fe, or Cu are preferred.

By using the organometallic complex of the present invention as a material for the hole injection layer, the driving voltage of the organic EL element can be reduced and the external extraction efficiency can be improved.

In addition to the above metal complexes, known materials used in the hole injection layer of organic EL elements can be used. The above metal complexes can also be used in combination with known materials.

The hole injection layer is described in detail in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, etc., and examples of materials used in known hole injection layers include the hole transport materials described above.

Among these, preferred are phthalocyanine derivatives such as copper phthalocyanine, hexaazatriphenylene derivatives such as those described in JP-T-2003-519432A and JP-A-2006-135145A, metal oxides such as vanadium oxide, amorphous carbon, conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometalated complexes such as tris(2-phenylpyridine)iridium complexes, and triarylamine derivatives. These materials may be used alone or in combination.

In the comparative examples in the following examples, copper phthalocyanine and polythiophene conductive polymer are used as materials for the hole injection layer, but when the organometallic complex of the present invention is used as a material for another layer, copper phthalocyanine and polythiophene conductive polymer are used as suitable materials for the hole injection layer.

The organic functional layer according to the present invention may contain other compounds.
Examples of other compounds include halogen elements such as bromine, iodine, and chlorine, halogenated compounds, alkali metals such as Pd, Ca, and Na, alkaline earth metals, and transition metal compounds, complexes, and salts.

The content of the other compounds can be determined as desired, but is preferably 1000 ppm or less, more preferably 500 ppm or less, and even more preferably 50 ppm or less, based on the total mass of the layer in which they are contained. However, the content may be outside this range depending on the purpose, such as improving the transportability of electrons or holes or facilitating the energy transfer of excitons.

(anode)
The anode is an electrode that functions to supply holes to the light-emitting layer, and is preferably optically transparent. The thickness of the anode, although depending on the material, is preferably within a range of 10 nm to 1 μm, and more preferably within a range of 10 to 200 nm.

The material used for the anode is preferably composed of an oxide semiconductor or a thin film of a metal or alloy, and examples thereof include metals such as Ag and Au or alloys mainly composed of metals, CuI, or indium-tin composite oxide (ITO), _SnO2 , ZnO, and other oxide semiconductors.

In the case of an anode having optical transparency, it is preferable that the main component is silver, and the purity of the silver is preferably 99% or more. In addition, palladium (Pd), copper (Cu), gold (Au), etc. may be added to ensure the stability of silver.

When the light-transmitting anode is a layer mainly composed of silver, it may be formed of silver alone or may be composed of an alloy containing silver (Ag). Examples of such alloys include silver-magnesium (Ag.Mg), silver-copper (Ag.Cu), silver-palladium (Ag.Pd), silver-palladium-copper (Ag.Pd.Cu), and silver-indium (Ag.In).

When the anode according to the present invention is a layer composed mainly of silver, the thickness of the anode is preferably within the range of 2 to 20 nm, and more preferably within the range of 4 to 12 nm. By making the thickness 20 nm or less, the absorption and reflection components of the light-transmitting anode are kept low, and a high light transmittance is maintained.

In the present invention, the term "layer mainly composed of silver" means that the silver content in the light-transmitting anode is 60% by mass or more. The silver content is more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 98% by mass or more.
The term "light transmissive" means that the light transmittance at a wavelength of 550 nm is 50% or more.

The layer composed mainly of silver may be divided into multiple layers and laminated as necessary.

When the anode is a layer mainly composed of silver and has optical transparency, it is preferable to provide an underlayer underneath it from the viewpoint of making the thickness of the film uniform. There are no particular limitations on the underlayer, but it is preferable that the underlayer be a layer containing an organic compound having nitrogen or sulfur atoms.

The nitrogen-atom-containing compound used in the underlayer is not particularly limited as long as it is a compound containing a nitrogen atom in the molecule, but is preferably a compound having a heterocycle with a nitrogen atom as the heteroatom. Examples of heterocycles with a nitrogen atom as the heteroatom include aziridine, azirine, azetidine, azeto, azolidine, azole, azinane, pyridine, azepane, azepine, imidazole, pyrazole, oxazole, thiazole, imidazoline, pyrazine, morpholine, thiazine, indole, isoindole, benzimidazole, purine, quinoline, isoquinoline, quinoxaline, cinnoline, pteridine, acridine, carbazole, benzo-C-cinnoline, porphyrin, chlorine, and choline.

In addition, the nitrogen atom-containing compound used in the underlayer is preferably an aromatic heterocyclic compound having a nitrogen atom with an unshared electron pair that is not involved in aromaticity.

Specific examples of these nitrogen atom-containing compounds include exemplified compounds No. 1 to No. 134 described in paragraphs (0097) to (0221) of JP 2015-046364 A.

The anode may be formed by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering, and then forming a pattern of the desired shape using a photolithography method, or, if high pattern precision is not required (approximately 100 μm or more), a pattern may be formed using a mask of the desired shape when vapor depositing or sputtering the electrode materials.

When using a coatable material such as an organic conductive compound, wet film formation methods such as printing and coating can also be used. When emitting light from this anode, it is desirable to make the transmittance greater than 10%, and the sheet resistance of the anode is preferably several hundred Ω/sq. or less.

(cathode)
The cathode is an electrode that functions to supply electrons to the light-emitting layer, and is preferably an electrode that is light-reflective or light-transmissive.

Materials used for the cathode include metals, alloys, organic or inorganic conductive compounds, or mixtures thereof, such as gold, aluminum, silver, magnesium, lithium, magnesium/copper mixtures, magnesium/silver mixtures, magnesium/aluminum mixtures, magnesium/indium mixtures, indium, lithium/aluminum mixtures, rare earth metals, ITO, ZnO, oxide semiconductors such as _TiO2 and _SnO2 , and among these, thin films of metals or alloys are preferred.

When the light-transmitting cathode is a layer mainly composed of silver, the same materials as those described in the above description of the anode can be used. Specifically, the cathode can be made of silver alone or an alloy containing silver (Ag). Examples of such alloys include silver-magnesium (Ag.Mg), silver-copper (Ag.Cu), silver-palladium (Ag.Pd), silver-palladium-copper (Ag.Pd.Cu), and silver-indium (Ag.In).

The cathode can be produced by forming a thin film of these electrode materials by methods such as vapor deposition or sputtering. The sheet resistance of the cathode is preferably several hundred Ω/sq. or less, and the thickness is preferably within the range of 10 nm to 5 μm, and more preferably within the range of 50 to 200 nm.

From the viewpoint of transmitting the emitted light and improving the luminance of the emitted light, it is preferable that either the anode or the cathode is transparent or semi-transparent. By preparing the above metal with a thickness in the range of 1 to 20 nm and preparing the conductive transparent material described in the description of the anode on top of it, a transparent or semi-transparent cathode can be produced. Furthermore, by applying this, an organic EL element in which both the anode and cathode are transparent can be produced.

(substrate)
The substrate used in the organic EL element of the present invention is not particularly limited, and may be transparent or opaque. When light is extracted from the substrate side, the substrate is preferably transparent. Examples of transparent substrates include glass, quartz, and transparent resin films. In addition, from the viewpoint of imparting flexibility to the organic EL element, a resin film having flexibility is more preferable.

Examples of resin films include polyesters such as polyethylene terephthalate (abbreviated as PET) and polyethylene naphthalate (abbreviated as PEN), polyethylene, polypropylene, cellophane, cellulose esters such as cellulose diacetate, cellulose triacetate (abbreviated as TAC), cellulose acetate butyrate, cellulose acetate propionate (abbreviated as CAP), cellulose acetate phthalate, and cellulose nitrate, and derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate (abbreviated as PC), norbornene resin, polymethylpentene, polyether ketone, polyimide, polyether sulfone (abbreviated as PES), polyphenylene sulfide, polysulfones, polyetherimide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylics and polyarylates, and cycloolefin resins.

Commercially available cycloolefin resins can be used, such as Arton (registered trademark) manufactured by JSR Corporation and Apel (registered trademark) manufactured by Mitsui Chemicals, Inc.

Among these resin films, polyethylene terephthalate (abbreviated as PET), polybutylene terephthalate, polyethylene naphthalate (abbreviated as PEN), polycarbonate (abbreviated as PC), etc. are preferably used as flexible resin films in terms of cost and availability.

The above resin film may be either an unstretched film or a stretched film.

The resin film can be produced by a conventional film-making method. For example, a substantially amorphous and unoriented unstretched resin film can be produced by melting the resin material in an extruder, extruding it through a circular die or a T-die, and quenching it. In addition, a stretched resin film can be produced by stretching an unstretched resin film in the conveying direction of the resin film (longitudinal axis direction, MD direction) or in a direction perpendicular to the conveying direction of the resin film (horizontal axis direction, TD direction) using a known method such as uniaxial stretching, tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, or tubular-type simultaneous biaxial stretching. In this case, the stretching ratio can be appropriately selected according to the resin that is the raw material of the resin film, but it is preferable that it is within the range of 2 to 10 times in each of the longitudinal and transverse directions.

The thickness of the resin film is preferably within the range of 3 to 200 μm, more preferably within the range of 10 to 100 μm, even more preferably within the range of 20 to 80 μm, and particularly preferably within the range of 20 to 50 μm. By reducing the thickness, light can be effectively shielded without increasing the size of the light shielding portion.

Examples of glass that can be used as a transparent substrate include soda-lime glass, barium-strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, and barium borosilicate glass.

Examples of opaque substrates include metal plates such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.

The external extraction quantum efficiency of the organic EL element of the present invention at room temperature is preferably 1% or more, and more preferably 5% or more. The external extraction quantum efficiency is represented by the following formula.
External extraction quantum efficiency (%)=number of photons emitted outside the organic EL element/number of electrons flowing into the organic EL element×100.

It is also possible to use a hue improving filter such as a color filter, or a color conversion filter that uses phosphors to convert the emitted color from the organic EL element into multiple colors.

(Gas Barrier Layer)
In the organic EL device of the present invention, a gas barrier layer may be provided on the substrate described above, if necessary. In particular, when the substrate is a resin film, it is preferable to provide a gas barrier layer.

The resin film on which the gas barrier layer is formed is preferably a barrier film having a water vapor permeability (25±0.5°C, relative humidity (90±2)% RH) of 0.01 g/( ^m2 ·24 h) or less, measured by a method in accordance with JIS K 7129-1992, and more preferably a high-barrier film having an oxygen permeability of ^10-3 mL/( ^m2 ·24 h·atm) or less and a water vapor permeability of ^10-5 g/( ^m2 ·24 h) or less, measured by a method in accordance with JIS K 7126-1987.

The material for forming the gas barrier layer may be any material that has the function of suppressing the intrusion of moisture, oxygen, and other substances that cause deterioration of the organic EL element, and examples of such materials that can be used include inorganic substances such as silicon oxide, silicon dioxide, and silicon nitride. From the viewpoint of improving brittleness, it is more preferable to have a laminated structure of these inorganic layers and organic layers made of an organic material. There are no particular restrictions on the order in which the inorganic layers and organic layers are laminated, but it is preferable to laminate the two layers alternately multiple times.

There are no particular limitations on the method for forming the gas barrier layer, and thin film formation methods such as vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric plasma polymerization, plasma CVD, laser CVD, thermal CVD, and coating can be used, but atmospheric plasma polymerization as described in JP-A-2004-68143 is particularly preferred. In addition, a method is also preferably used in which a polysilazane-containing liquid is applied by a wet coating method to form a coating film, which is then dried, and the coating film is irradiated with vacuum ultraviolet light (VUV light) having a wavelength of 200 nm or less to modify the coating film formed, thereby forming a gas barrier layer.

The thickness of the gas barrier layer is preferably within the range of 1 to 500 nm, and more preferably within the range of 10 to 300 nm. If the thickness of the gas barrier layer is 1 nm or more, the desired gas barrier performance can be exhibited, and if the thickness is 500 nm or less, deterioration of the film quality, such as the occurrence of cracks in the dense silicon oxynitride film, can be prevented.

(Sealing)
The materials used for the organic functional layer and the electrodes have low moisture resistance and are easily oxidized, that is, decomposition and oxidation occur due to water, oxygen, etc. in the environment, so it is preferable to seal the organic functional layer and the electrodes to prevent moisture from entering them. As a sealing means, for example, a method of bonding a sealing member to the electrodes and the substrate with an adhesive can be mentioned. The sealing member may be a concave plate or a flat plate as long as it is arranged so as to cover the display area of the organic EL element. In addition, the transparency and electrical insulation are not particularly limited.

Specific examples include glass plates, polymer plates/films, and metal plates/films. Examples of glass plates include soda-lime glass, barium-strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of polymer plates include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of metal plates include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, from the viewpoint of thinning the organic EL element, a polymer film or a metal film is preferred. The polymer film preferably has an oxygen permeability of 1×10 ⁻³ mL/m ² /24 h or less as measured by a method conforming to JIS K 7126-1987, and a water vapor permeability of 1×10 ⁻³ g/(m ² /24 h) or less as measured by a method conforming to JIS K 7129-1992 (25±0.5° C., relative humidity (90±2)%).

Methods used to process the sealing member into a concave shape include sandblasting and chemical etching.

Examples of adhesives include photocurable and heat-curable adhesives with reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, moisture-curable adhesives such as 2-cyanoacrylic esters, heat- and chemical-curable (two-part mixture) adhesives such as epoxy-based adhesives, hot-melt adhesives such as polyamide, polyester, and polyolefin, and cationic curable UV-curable epoxy resin adhesives.

Since organic EL elements may deteriorate due to heat treatment, it is preferable to use an adhesive that can be cured at temperatures ranging from room temperature to 80°C. A desiccant may also be dispersed in the adhesive. The adhesive may be applied to the sealing portion using a commercially available dispenser, or may be printed, such as by screen printing.

It is also preferable to form a sealing film by covering the electrode and the organic functional layer on the outside of the electrode facing the substrate with the organic layer and forming an inorganic or organic layer in contact with the substrate. In this case, the material for forming the sealing film may be any material that has the function of preventing the intrusion of moisture, oxygen, and other substances that cause deterioration of the element, and examples of materials that can be used include silicon oxide, silicon dioxide, and silicon nitride.

Furthermore, from the viewpoint of improving the fragility of the sealing film, it is preferable to form a laminate structure of these inorganic layers and organic layers. There are no particular limitations on the method for forming the sealing film, and for example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma polymerization, plasma CVD, laser CVD, thermal CVD, coating, etc. can be used.

In the gas and liquid phase, it is preferable to inject an inert gas such as nitrogen or argon, or an inert liquid such as fluorohydrocarbon or silicone oil into the gap between the sealing member and the display area of the organic EL element. It is also possible to create a vacuum, or to seal a hygroscopic compound inside.

Examples of hygroscopic compounds include metal oxides (e.g., sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide, etc.), sulfates (e.g., sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate, etc.), metal halides (e.g., calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), and perchlorates (e.g., barium perchlorate, magnesium perchlorate, etc.), and anhydrous salts are preferably used for sulfates, metal halides, and perchlorates.

(Protective film, protective plate)
A protective film or protective plate may be provided on the outer side of the sealing member or sealing film on the side facing the substrate with the organic functional layer sandwiched therebetween in order to enhance the mechanical strength of the element. In particular, when a sealing film is used, it is preferable to provide such a protective film or protective plate, since its mechanical strength is not necessarily high. As materials used for the protective film and protective plate, glass plates, polymer plates/films, metal plates/films, etc. can be used as in the sealing member and sealing film, but it is preferable to use polymer films from the viewpoint of light weight and thinness.

(Light extraction improvement technology)
The organic EL element of the present invention generally emits light inside a layer having a refractive index higher than that of air (within the range of a refractive index of 1.6 to 2.1), and only about 15% to 20% of the light generated in the light-emitting layer can be extracted. This is because light that is incident on an interface (interface between a substrate and air) at an angle θ equal to or greater than the critical angle is totally reflected and cannot be extracted to the outside of the organic EL element, and because light is totally reflected between an electrode or a light-emitting layer and a substrate, and the light is guided through the electrode or the light-emitting layer, resulting in the light escaping in the direction of the side of the organic EL element.

Methods for improving light extraction efficiency include, for example, forming irregularities on the substrate surface to prevent total reflection at the substrate-air interface (e.g., U.S. Pat. No. 4,774,435 specification), improving efficiency by giving the substrate light-collecting properties (e.g., JP-A-63-314795), forming a reflective surface on the side of the organic EL element (e.g., JP-A-1-220394), introducing a flat layer with an intermediate refractive index between the substrate and the light-emitting layer to form an anti-reflection film (e.g., JP-A-62-172691), introducing a flat layer with a lower refractive index than the substrate between the substrate and the light-emitting layer (e.g., JP-A-2001-202827), and forming a diffraction grating between or within the substrate, electrode, and light-emitting layer (JP-A-11-283751).

In the present invention, it is preferable to use a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light-emitting layer, or a method of forming a diffraction grating between or within any of the layers of the substrate, the electrode, and the light-emitting layer.

By forming a flat layer with a low refractive index (hereinafter also referred to as a "low refractive index layer") between the substrate and the electrode with a thickness longer than the wavelength of light, the lower the refractive index of the low refractive index layer, the higher the efficiency of extracting light to the outside. By combining these means, the present invention can obtain an organic EL element with even higher brightness or excellent durability.

Materials used to form the low refractive index layer include, for example, aerogel, porous silica, magnesium fluoride, and fluorine-based polymers. Generally, the refractive index of the substrate is within the range of 1.5 to 1.7, so the refractive index of the low refractive index layer is preferably 1.5 or less, and more preferably 1.35 or less.

In addition, in order to prevent the electromagnetic waves leaking out due to evanescent effects from penetrating into the substrate and weakening the effect of the low refractive index layer, it is preferable that the thickness of the low refractive index layer is at least twice the wavelength in the low refractive index layer.

The method of forming a diffraction grating utilizes the property of a diffraction grating to change the direction of light to a specific direction different from refraction through so-called Bragg diffraction, such as first-order diffraction and second-order diffraction, and aims to diffract the light generated from the light-emitting layer that cannot escape due to total reflection between layers by introducing a diffraction grating between or within the substrate, electrode, or light-emitting layer, and extract the light to the outside.

Since the light emitted from the light-emitting layer is generated randomly in all directions, a typical one-dimensional diffraction grating that has a periodic refractive index distribution only in one direction diffracts only light traveling in a specific direction, and the light extraction efficiency does not improve significantly. However, by making the refractive index distribution two-dimensional, light traveling in all directions is diffracted, improving the light extraction efficiency.

The diffraction grating may be formed between or within any of the substrate, electrode, and light-emitting layer, but is preferably formed near the light-emitting layer where light is generated. In this case, the period of the diffraction grating is preferably within the range of about 1/2 to 3 times the wavelength of the light in the medium. The diffraction grating is preferably arranged two-dimensionally, such as in a square lattice, triangular lattice, or honeycomb lattice pattern.

(Light collecting sheet)
The organic EL element of the present invention can be processed to have, for example, a microlens array structure on the light extraction side of the substrate, or can be provided with a light-collecting sheet, thereby enabling light to be collected in a specific direction, for example, in the front direction relative to the light-emitting surface of the organic EL element, and thus enabling the brightness in the specific direction to be increased.

An example of a microlens array is a two-dimensional array of square pyramids with a side length of 30 μm and a apex angle of 90 degrees on the light extraction side of the substrate. It is preferable that each side is within the range of 10 to 100 μm. By being within the above range, it is possible to provide a light-collecting function and make the thickness sufficiently thin.

The light-collecting sheet may be, for example, one that is in practical use in LED backlights for liquid crystal display devices, specifically, brightness enhancement film (BEF) manufactured by Sumitomo 3M. The shape of the prism sheet may be, for example, a base material with triangle-shaped stripes with an apex angle of 90 degrees and a pitch of 50 μm, or a shape with rounded apex angles, a shape with randomly varying pitch, or other shapes.

In addition, a light diffusion plate or film may be used in combination with the light collecting sheet to control the light radiation angle from the organic EL element. For example, a diffusion film (Light Up) manufactured by Kimoto Co., Ltd. can be used.

<2. Manufacturing method of organic electroluminescence element>
The method for producing the organic EL element of the present invention will be described below.

(Anode Formation Process)
The anode may be formed by forming a thin film by a method such as deposition or sputtering using a material capable of producing an amorphous transparent conductive film, such as a metal such as Ag or Au or an alloy mainly composed of a metal, CuI, or an indium _- tin composite oxide (ITO), an oxide semiconductor such as _{SnO 2} and ZnO, or IDIXO (In 2 O 3 -ZnO), and forming a pattern of a desired shape by a photolithography method. When pattern precision is not required very much (about 100 μm or more), a pattern may be formed through a mask of a desired shape during deposition or sputtering of the electrode material. In addition, when a coatable material such as an organic conductive compound is used, a wet film formation method such as a printing method or a coating method may be used.

(Formation process of organic functional layer)
A method for forming the organic functional layers (hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) according to the present invention will be described.
The method for forming the organic functional layer is not particularly limited, and any conventionally known forming method such as a vacuum deposition method or a wet method (also called a wet process) can be used.

Examples of wet methods include printing methods such as gravure printing, flexographic printing, and screen printing, as well as spin coating, casting, inkjet printing, die coating, blade coating, bar coating, roll coating, dip coating, spray coating, curtain coating, doctor coating, and LB (Langmuir-Blodgett) methods. From the viewpoint of high productivity, inkjet printing using an inkjet head is more preferable because it allows the coating liquid to be applied easily and accurately. Details of inkjet printing will be described later. Also, a different film formation method may be used for each layer.

The coating liquid used in the wet method may be a solution in which the material forming the organic functional layer is uniformly dissolved in the liquid medium, or a dispersion in which the material is dispersed as a solid in the liquid medium. Examples of dispersion methods include ultrasonic dispersion, high shear dispersion, and media dispersion.

The liquid medium is not particularly limited, and examples thereof include halogen-based solvents such as chloroform, carbon tetrachloride, dichloromethane, 1,2-dichloroethane, dichlorobenzene, and dichlorohexanone; ketone-based solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, n-propyl methyl ketone, and cyclohexanone; aromatic solvents such as benzene, toluene, xylene, mesitylene, and cyclohexylbenzene; aliphatic solvents such as cyclohexane, decalin, and dodecane; ester-based solvents such as ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, and diethyl carbonate; ether-based solvents such as tetrahydrofuran and dioxane; amide-based solvents such as dimethylformamide and dimethylacetamide; alcohol-based solvents such as methanol, ethanol, 1-butanol, and ethylene glycol; nitrile-based solvents such as acetonitrile and propionitrile; dimethyl sulfoxide, water, and mixtures thereof.

The boiling point of these liquid media is preferably lower than the temperature of the drying process in order to quickly dry the liquid media, and more specifically, is preferably within the range of 60 to 200°C, and more preferably within the range of 80 to 180°C.

The coating solution may contain a surfactant to control the coating area or to suppress liquid flow associated with the surface tension gradient after coating (e.g., liquid flow that causes a phenomenon called coffee ring).

Examples of surfactants that can be used include anionic or nonionic surfactants, taking into consideration the effect of moisture contained in the solvent, leveling properties, wettability to the substrate, etc. Specifically, fluorine-containing surfactants and surfactants listed in WO 08/146681, JP 2-41308 A, etc. can be used.

The viscosity and thickness of the coating film can be appropriately selected depending on the function required for the organic functional layer and the solubility or dispersibility of the organic material. Specifically, the viscosity of the coating film is preferably within the range of 0.3 to 100 mPa·s, and the thickness is preferably within the range of 1 to 90 μm.

After forming the coating film by the wet method, it is preferable to have a drying process in which the liquid medium is removed. The temperature in the drying process is not particularly limited, but is preferably a temperature that does not damage the organic functional layer, electrodes, substrate, etc. Although it varies depending on the composition of the coating liquid, for example, the temperature in the drying process is preferably within the range of 80 to 300°C, and the time is preferably within the range of 10 seconds to 10 minutes. By being within the above range, rapid drying can be achieved.

When a vapor deposition method is adopted as a method for forming the organic functional layer, the vapor deposition conditions vary depending on the type of compound used, etc., but for example, it is preferable that the boat heating temperature is within the range of 50 to 450° C., the degree of vacuum is within the range of 1×10 ⁻⁶ to 1×10 ⁻² Pa, the vapor deposition rate is within the range of 0.01 to 50 nm/sec, and the substrate temperature is within the range of −50 to 300° C. In addition, the total thickness of the organic functional layer is preferably within the range of 0.1 nm to 5 μm, and more preferably within the range of 5 to 200 nm.

It is preferable to form the organic functional layer from the hole injection layer to the cathode in a single vacuum pull, but it is also possible to remove the layer midway and apply a different film formation method. In this case, it is preferable to perform the work in a dry inert gas atmosphere.

(Cathode Formation Process)
After the organic functional layer is formed in this manner, a thin film made of the above-mentioned electrode material is formed on the organic functional layer by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably in the range of 10 to 200 nm, to form a cathode. At the same time, a portion for connecting to an external power source is formed at the end of the cathode. After the cathode is formed, the substrate, anode, organic functional layer, and cathode are sealed with the above-mentioned sealing member.

<3. Uses of organic EL elements>
The organic EL element of the present invention can emit dot light to reproduce patterns or characters, or emit multiple colors to provide a color organic EL device. Examples of light emitting sources include household lighting, car lighting, backlights for clocks and liquid crystal displays, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copiers, light sources for optical communication processors, and light sources for optical sensors. Although not limited thereto, the organic EL element can realize high-definition pixels, and is therefore suitable for electronic devices such as micro LEDs in which the R (red), G (green), and B (blue) constituting the subpixels of the above-mentioned display are each an independent LED.

[Organic solar cell]
3 is a schematic diagram showing an example of a solar cell having a single structure (one layer of bulk heterojunction layer) made of a bulk heterojunction type organic photoelectric conversion element. In Fig. 3, a bulk heterojunction type organic photoelectric conversion element 10 has a transparent electrode (anode) 12, a hole transport layer 17, a bulk heterojunction layer photoelectric conversion part 14, an electron transport layer 18, and a counter electrode (cathode) 13 laminated in this order on one side of a substrate 11.

The substrate 11 is a member that holds the transparent electrode 12, the photoelectric conversion section 14, and the counter electrode 13, which are stacked in this order. Since light to be photoelectrically converted is incident from the substrate 11 side, the substrate 11 is preferably a member that can transmit the light to be photoelectrically converted, that is, a member that is transparent to the wavelength of the light to be photoelectrically converted. For example, glass or a resin film is used as the substrate 11.

The photoelectric conversion section 14 is a layer that converts light energy into electrical energy, and is configured to have a bulk heterojunction layer in which p-type semiconductor material and n-type semiconductor material are uniformly mixed. The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor). Here, the electron donor and electron acceptor are "electron donors and electron acceptors that, when light is absorbed, electrons move from the electron donor to the electron acceptor, forming a hole-electron pair (charge-separated state)" and do not simply donate or accept electrons like an electrode, but donate or accept electrons through a photoreaction.

In FIG. 3, light incident from the transparent electrode 12 through the substrate 11 is absorbed by the electron acceptor or electron donor in the bulk heterojunction layer of the photoelectric conversion section 14, and electrons move from the electron donor to the electron acceptor, forming pairs of holes and electrons (charge separation state). The generated charges are transported to different electrodes, with the electrons passing between the electron acceptors and the holes passing between the electron donors due to the internal electric field, for example, the potential difference between the transparent electrode 12 and the counter electrode 13 when the work functions of the transparent electrode 12 and the counter electrode 13 are different, and a photocurrent is detected. For example, when the work function of the transparent electrode 12 is larger than that of the counter electrode 13, the electrons are transported to the transparent electrode 12 and the holes are transported to the counter electrode 13. If the magnitudes of the work functions are reversed, the electrons and holes are transported in the opposite direction. In addition, the transport direction of the electrons and holes can be controlled by applying a potential between the transparent electrode 12 and the counter electrode 13.

The organometallic complex of the present invention is a compound that is easy to conduct carriers because it is polarized within the molecule and has advantages in charge separation. Therefore, it is effective to apply it as a heterojunction type n-type material in solar cells, especially organic solar cells.

The organometallic complex of the present invention can also be used in heterojunction solar cells, such as organic EL elements, in which an n-type layer and a p-type layer are stacked, or in bulk heterojunction solar cells in which an n-type compound and a p-type compound coexist in the photoelectric conversion section 14, creating a sea-island structure that increases the area of the p/n interface.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

Example 1
[Method for synthesizing metal complex MO-9 by template reaction]

To 2,2'-bipyridyl (23.4 g, 150.0 mmol), 1,5-cyclooctadiene (18.4 mL, 150.0 mmol), bis(1,5-cyclooctadiene)nickel(0) (41.3 g, 150.0 mmol), DMF (62.5 mL) and toluene (62.5 mL) were added and stirred at 80°C for 30 minutes. A solution of compound 2 (3.78 g, 15.0 mmol) in toluene (250 mL) was added dropwise to the mixture over 1 hour and stirring was continued at 80°C for another 16 hours. The reaction mixture was cooled to room temperature, 2M hydrochloric acid (300 mL) was added and stirred vigorously overnight under air. Extraction was performed with CH ₂ Cl ₂ (400 mL×3), and the organic layer was washed with saturated brine (200 mL), dried over Na ₂ SO ₄ , and then concentrated in vacuum. The crude product was passed through a silica gel short pass (eluent: CHCl ₃ :MeOH=20:1) and further purified by GPC (YMC T30000, T4000, T2000 columns, solvent: CHCl ₃ ) to obtain compound MO-9 as a yellow solid in a yield of 57% (1.77 g, 1.71 mmol). The obtained MO-9 is in the state of a high-spin complex, and its magnetic properties can also be utilized.

Example 2
[Method of synthesizing metal complex MO-11: exchange of central metal]
Synthesis was carried out in exactly the same manner as in Example 1, except that 10 equivalents of CuCl (14.9 g, 150 mmol) was added to a DMF/toluene solution of 2,2'-bipyridyl, 1,5-cyclooctadiene, and bis(1,5-cyclooctadiene)nickel(0). Mass spectrometry revealed that copper complex MO-11 was produced. It was found that by replacing the copper salt used in Example 2 with various metal salts and carrying out a reaction in the presence of these salts, metal species exchange occurred after the C-C coupling/cyclization reaction by template reaction, making it possible to convert to other metals.

Example 3
[Preparation of thin film (glowing plastic film) containing MO-9]
10 mg of PMMA (polymethyl methacrylate, Mw: 15,000, manufactured by Aldrich) and 0.1 mg of MO-9 were added to 1.0 mL of chloroform to prepare a solution in which the content of MO-9 relative to PMMA was 1 mass %. This solution was applied to a 3 cm square quartz substrate, and a thin film containing MO-9 was formed by spin coating. When the obtained thin film was irradiated with 254 nm UV light, pale light emission resulting from the emission of MO-9 in chloroform (353 nm) was observed.

Example 4
[Organic Electronics Devices]
(Preparation of Comparative Organic EL Element 4-1)
A glass plate on which a 100 nm ITO (indium tin oxide) film was formed as a first electrode (anode) was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas and cleaned with UV ozone, and fixed to a substrate holder of a vacuum deposition apparatus. Next, copper phthalocyanine was evaporated to a thickness of 10 nm to provide a hole injection layer, and α-NPD (4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) was evaporated on the hole injection layer to provide a hole transport layer having a thickness of 40 nm.

A host material, CBP (4,4'-bis[9H-carbazol-9-yl]biphenyl), and a light-emitting material, Ir(ppy) ₃ (tris[2-phenylpyridinato]iridium(III)), were co-evaporated to have volume percentages of 94% and 6%, respectively, to provide a light-emitting layer having a thickness of 30 nm.

After that, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was evaporated to form an electron transport layer with a thickness of 330 nm. Furthermore, aluminum was evaporated to form a second electrode (cathode) with a thickness of 100 nm.

Next, the following gas barrier film was produced as a sealing member for the entire organic EL element.

An inorganic gas barrier layer made of _SiOx was formed to a thickness of 500 nm on the entire surface of a polyethylene naphthalate film (manufactured by Teijin Film Solutions Limited) using an atmospheric pressure plasma discharge treatment device having the configuration described in JP 2004-68143 A, to produce a flexible gas barrier film having gas barrier properties of an oxygen permeability of 0.001 mL/( ^m2 ·24 h) or less and a water vapor permeability of 0.001 g/( ^m2 ·24 h) or less.

A thermosetting liquid adhesive (epoxy resin) was formed to a thickness of 25 μm as a sealing resin layer on one side of the gas barrier film. Then, the gas barrier film with this sealing resin layer was superimposed on the organic EL element prepared above. At this time, the sealing resin layer-forming surface of the gas barrier film was continuously superimposed on the sealing surface side of the organic EL element so that the ends of the extraction parts of the anode and cathode were exposed.

Next, the sample with the gas barrier film attached was placed in a vacuum device and pressed at 90°C and 0.1 MPa for 5 minutes. The sample was then returned to an atmospheric pressure environment and heated at 90°C for a further 30 minutes to harden the adhesive.

(Preparation of Organic EL Element 4-2 of the Invention)
Organic EL element 4-2 was produced in the same manner as in Organic EL element 4-1 produced above, except that the copper phthalocyanine used as the hole injection material was changed to MO-9 synthesized in Example 1.
The voltage at the start of light emission of the produced organic EL elements was measured at a temperature of 23° C. The driving voltage was the voltage value at which the current density reached 2.5 mA/ ^cm2 , and when a relative evaluation was performed with Organic EL Element 4-1 set at 100, Organic EL Element 4-2 was 95, confirming a decrease in driving voltage and clearly demonstrating the superiority of the material of the present invention.

Example 5
[Organic Electronics Devices]
(Preparation of Comparative Organic EL Element 5-1)
A glass substrate on which a 100 nm ITO (Indium Tin Oxide) film was formed as a first electrode (anode) was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and cleaned with UV ozone. Next, a solution of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT/PSS) (Heraeus, CLEVIOS P VP AI 4083) diluted to 70% with pure water was spin-coated at 3000 rpm for 30 seconds, and then dried at 200° C. for 1 hour to provide a hole injection layer with a film thickness of 30 nm. Next, α-NPD (4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) was evaporated onto the hole injection layer to provide a hole transport layer with a thickness of 40 nm.

CBP (4,4'-bis[9H-carbazol-9-yl]biphenyl) as a semiconducting host material and Ir(ppy) ₃ (tris[2-phenylpyridinato]iridium(III)) as a light-emitting material were co-evaporated to a volume percentage of 94% and 6%, respectively, to provide a light-emitting layer having a thickness of 30 nm.

Thereafter, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was evaporated to provide an electron transport layer having a thickness of 330 nm.
Furthermore, aluminum was further evaporated to a thickness of 100 nm to provide a second electrode (cathode).

Next, the following gas barrier film was prepared as a sealing member for the entire organic EL element.
An inorganic gas barrier layer made of SiOx was formed to a thickness of 500 nm on the entire surface of a polyethylene naphthalate film (manufactured by Teijin Film Solutions Co., Ltd.) using an atmospheric pressure plasma discharge treatment device with the configuration described in JP- _A -2004-68143. This produced a flexible gas barrier film with gas barrier properties of oxygen permeability of 0.001 mL/( ^m2 ·24 h) or less and water vapor permeability of 0.001 g/( ^m2 ·24 h) or less.

A thermosetting liquid adhesive (epoxy resin) was formed to a thickness of 25 μm as a sealing resin layer on one side of the gas barrier film. Then, the gas barrier film with this sealing resin layer was superimposed on the organic EL element prepared above. At this time, the sealing resin layer-forming surface of the gas barrier film was continuously superimposed on the sealing surface side of the organic EL element so that the ends of the extraction parts of the anode and cathode were exposed.

Next, the sample with the gas barrier film attached was placed in a vacuum device and pressed at 90°C and 0.1 MPa for 5 minutes. The sample was then returned to an atmospheric pressure environment and heated at 90°C for a further 30 minutes to harden the adhesive.

(Preparation of Organic EL Element 5-2 of the Invention)
Organic EL element 5-2 was produced in the same manner as above, except that a hole injection layer having a thickness of 30 nm was provided by vacuum deposition using MO-11 instead of PEDOT/PSS used in the organic EL element 5-1 produced above.
The voltage at the start of light emission of the produced organic EL elements was measured at a temperature of 23° C. The driving voltage was defined as the voltage value at which the current density reached 2.5 mA/ ^cm2. When a relative evaluation was performed with Organic EL Element 5-1 set at 100, Organic EL Element 5-2 was 96, confirming a decrease in driving voltage and clearly demonstrating the superiority of the material of the present invention.

REFERENCE SIGNS LIST 1 organic EL element 2 substrate 3 anode 4 hole injection layer 5 hole transport layer 6 light emitting layer 7 electron transport layer 8 electron injection layer 9 cathode F organic functional layer R recombination L light 10 bulk heterojunction type organic photoelectric conversion element 11 substrate 12 transparent electrode (anode)
13 Counter electrode (cathode)
14 Photoelectric conversion section (bulk heterojunction layer)
17 hole transport layer 18 electron transport layer

Claims (7)

An organometallic complex having a structure represented by the following structural formulae: MO-7, MO-8, MO-9, MO-10, MO-11, MO-16, MO-17, MO-18, MO-20, MO-23, and MO-24 .
A method for synthesizing an organometallic complex having a structure represented by the following general formula (3) , comprising the steps of:
The method includes a step of cyclizing the ligand by a coupling reaction in the presence of a metal atom or ion,
The metal is Ni or Pd.
1. A method for synthesizing an organometallic complex comprising the steps of:
(In the formula, R ₁ to R ₃ each independently represent a hydrogen atom or a substituent. M represents a metal atom or ion other than sodium. n represents a natural number from 4 to 8, and the n R ₁ to R ₃ are each the same.) After the step of cyclizing the ligand, a step of replacing a central metal atom or ion of the cyclized ligand by a reaction in the presence of a metal salt different from the metal used in the step of cyclizing the ligand,
The method for synthesizing an organometallic complex according to claim 2 . The method for synthesizing an organometallic complex according to claim 3 is used.
1. A method for synthesizing an organocopper complex comprising the steps of: A film comprising the organometallic complex according to claim 1 . An organic electronic device comprising an organic functional layer containing the organometallic complex according to claim 1 . An organic electroluminescence device comprising an organic functional layer containing the organometallic complex according to claim 1 .

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