JP2012167028A - Substituted phenylpyridine iridium complex, luminescent material including the same, and organic el element employing the complex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an iridium complex, and a luminescent material and an organic EL element each including the same.SOLUTION: There is disclosed a substituted phenylpyridine iridium complex represented by formula (1) (in the formula, Rto Rrepresent a group each independently selected from the group consisting of hydrogen, and a 1C-4C straight chain or branched alkyl group; Rto Rrepresent a group each independently selected from the group consisting of hydrogen, a 1C-4C straight chain or branched alkyl group, a 1C-4C straight chain or branched alkoxy group, and fluorine; Prepresents a group selected from the group consisting of a 3-pyridyl group and a 4-pyridyl group each represented by a specific formula respectively; and Rto Rrepresent a group each independently selected from the group consisting of hydrogen, and a 1C-4C straight chain or branched alkyl group).

Description

  The present invention relates to a substituted phenylpyridine iridium complex, a light-emitting material comprising the complex, and an organic EL (electroluminescence) device using the complex.

The organic EL element emits light when excitation energy generated by recombination of holes and electrons injected from the electrode relaxes to a ground state through a light emission process. However, in the excited state generated by recombination of holes and electrons, there are two types of singlet excited state and triplet excited state in a ratio of 1: 3. In the past, fluorescent materials utilizing light emission from a singlet excited state have been used as light emitting materials. In this case, since the internal quantum efficiency is 25% at the maximum, if the light extraction efficiency is 20%, the maximum external quantum yield is theoretically limited to 5% (Non-patent Document 1).
In recent years, it has been reported that emission efficiency is improved by using light emission from a triplet excited state, that is, phosphorescence emission, using a complex compound utilizing a heavy atom effect such as iridium or platinum. In addition to the singlet excited state, the maximum internal quantum efficiency can theoretically reach 100% by utilizing light emission from the triplet excited state, and phosphorescent materials are attracting attention as light emitting materials ( Non-patent document 2).
In addition, since phosphorescent materials contribute to improving the light emission efficiency and electrical characteristics of organic EL elements, research on organic EL elements using the phosphorescent materials has been vigorously conducted (Patent Document 1, etc.).

For example, tris (2-phenylpyridinato) iridium (III) [Ir (ppy) ₃ ] represented by the following formula is widely used as a green light emitting material.
In addition, Adachi et al. Attracted attention as bis [2- (4,6-difluorophenyl) pyridinato] picolinatoiridium (III) (FIrpic) represented by the following formula, which is a blue light emitting material. High efficiency studies of organic EL elements using FIrpic and novel blue phosphorescent complex search studies have been actively conducted (Non-patent Document 3).
In view of such a situation, in the future development of organic EL lighting and organic EL display, development of new phosphorescent materials is expected to occupy a large weight.

JP 2010-254642 A

Toshio Higuchi: Electroluminescent display, p. 114, Industrial Books (1991) C. Adachi, R.A. C. Kwon, M .; A. Baldo, M .; E. Thompson, S.M. R. Forrest, Proc. 8th IDW'01, P.I. 1420 (2001) Appl. Phys. Lett. 79, 2082 (2001)

  An object of the present invention is to provide a substituted phenylpyridine iridium complex, a light-emitting material comprising the complex, and an organic EL device using the complex.

The above problems are solved by the following inventions 1) to 3).
1) A substituted phenylpyridine iridium complex represented by the following general formula (1).
[Wherein, R ^{1 to} R ⁴ are groups independently selected from the group consisting of hydrogen and a linear or branched alkyl group having 1 to 4 carbon atoms, and R ^{5 to} R ⁷ are hydrogen and 1 carbon atom. -4 linear or branched alkyl groups, C 1-4 linear or branched alkoxy groups, and groups independently selected from the group consisting of fluorine. Py is a group selected from the group consisting of a 3-pyridyl group or a 4-pyridyl group represented by the following formula, and R ^{8 to} R ¹⁵ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. Each independently selected from the group consisting of ]

2) A luminescent material comprising the substituted phenylpyridine iridium complex described in 1).
3) An organic EL device using the substituted phenylpyridine iridium complex described in 1).

  According to the present invention, a substituted phenylpyridine iridium complex, a light emitting material comprising the complex, and an organic EL device using the complex can be provided. Moreover, since the substituted phenylpyridine iridium complex of this invention shows favorable solubility with respect to cyclohexanone, 2-ethoxyethanol, and ethylbenzoic acid, the large area organic EL panel by the apply | coating method can be manufactured easily. Therefore, it can be said that it is extremely important industrially.

¹ H-NMR chart of tris [2- (3-bromophenyl) pyridine] iridium complex [Ir (Br-ppy) ₃ ] prepared in Example 1. ¹ H-NMR chart of tris {2- [3- (4-pyridyl) phenyl] pyridine} iridium complex [Ir (4Py-ppy) ₃ ] prepared in Example 1. _{3 is} a mass spectrum chart of Ir (4Py-ppy) ₃ produced in Example 1. FIG. The chart which performed the purity analysis with the high performance liquid chromatograph of Ir (4Py-ppy) ₃ produced in Example 1. FIG. ¹ H-NMR chart of {2- [3- (3-pyridyl) phenyl] pyridine} iridium complex [Ir (3Py-ppy) ₃ ] prepared in Example 2. The chart which performed the purity analysis with the high performance liquid chromatograph of Ir (3Py-ppy) ₃ produced in Example 2. FIG. The chart of the ultraviolet-visible absorption spectrum (UV-vis absorption spectrum) in the 1,2- dichloroethane solution of Examples 7-8 and the comparative example 2. FIG. The chart of the ultraviolet-visible absorption spectrum (UV-vis absorption spectrum) in the THF solution of Examples 7-8 and Comparative Example 2. The chart of the photoluminescence spectrum (PL spectrum) in the THF solution of Examples 9 to 10 and Comparative Example 3. The chart of the ultraviolet-visible absorption spectrum (UV-vis absorption spectrum) of the vapor deposition film which doped 8 wt% of iridium complexes of Examples 11-12 and Comparative Example 4 to CBP. The chart of the photoluminescence spectrum (PL spectrum) of the vapor deposition film which doped 8 wt% of iridium complexes of Examples 13-14 and Comparative Example 5 to CBP. The figure which shows the organic EL element structure produced in Examples 17-18 and the comparative example 7. FIG. The figure which shows the current density-voltage characteristic of Examples 17-18 and the comparative example 7. FIG. The figure which shows the luminance-voltage characteristic of Examples 17-18 and the comparative example 7. FIG. The figure which shows the power efficiency-luminance characteristic of Examples 17-18 and the comparative example 7. FIG. The figure which shows the current efficiency-luminance characteristic of Examples 17-18 and Comparative Example 7. The figure which shows the external quantum efficiency-luminance characteristic of Examples 17-18 and the comparative example 7. FIG. The figure which shows the EL spectrum of Examples 17-18 and the comparative example 7. FIG. The figure which shows the organic EL element structure produced in Examples 19-20 and the comparative example 8. FIG. The figure which shows the current density-voltage characteristic of Examples 19-20 and the comparative example 8. FIG. The figure which shows the luminance-voltage characteristic of Examples 19-20 and the comparative example 8. FIG. The figure which shows the power efficiency-luminance characteristic of Examples 19-20 and the comparative example 8. FIG. The figure which shows the current efficiency-luminance characteristic of Examples 19-20 and Comparative Example 8. The figure which shows the external quantum efficiency-brightness characteristic of Examples 19-20 and the comparative example 8. FIG. The figure which shows the EL spectrum of Examples 19-20 and the comparative example 8. FIG. The figure which shows the structural example of the organic EL element of this invention. The figure which shows the other structural example of the organic EL element of this invention. The figure which shows the other structural example of the organic EL element of this invention. The figure which shows the other structural example of the organic EL element of this invention. The figure which shows the other structural example of the organic EL element of this invention. The figure which shows the other structural example of the organic EL element of this invention. The figure which shows the other structural example of the organic EL element of this invention. The figure which shows the other structural example of the organic EL element of this invention.

Hereinafter, the present invention will be described in detail.
Examples of the linear or branched alkyl group having 1 to 4 carbon atoms of R ^{1 to} R ¹⁵ in the substituted phenylpyridine iridium complex of the present invention include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, and an isobutyl group. And a tertiary butyl group. Examples of the linear or branched alkoxy group having 1 to 4 carbon atoms of R ^{5 to} R ⁷ include a methoxy group, an ethoxy group, a normal propoxy group, an isopropoxy group, a normal butoxy group, an isobutoxy group, and a tertiary butoxy group. can do.

The substituted phenylpyridine iridium complex of the present invention can be prepared by the following two-step reaction.
<First reaction>

In the reaction formula, NBS is N-bromosuccinimide.

<Second reaction>
In the reaction formula, Pd (PPh ₃ ) ₄ is tetrakis (triphenylphosphine) palladium, and K ₂ CO ₃ aq is an aqueous potassium carbonate solution. R ^{1 to} R ⁴ are hydrogen, a group consisting of a linear or branched alkyl group having 1 to 4 carbon atoms, and R ^{5 to} R ⁷ are hydrogen, a linear or branched alkyl group having 1 to 4 carbon atoms, carbon number 1 to 4 linear or branched alkoxy groups and groups independently selected from the group consisting of fluorine, and R ^{8 to} R ¹⁵ are each composed of hydrogen and a linear or branched alkyl group having 1 to 4 carbon atoms. Each group independently selected from the group

  The first reaction is bromination of tris (2-phenylpyridine) iridium. As brominating agents used in bromination, bromine water, carbon tetrabromide, benzyl bromide, tetra-n-butylammonium tribromide, N-bromosuccinimide and the like can be used. Acid imides are preferred. The solvent used in the reaction is not particularly limited as long as it does not undergo bromination or is difficult to undergo bromination. Examples thereof include dichloromethane, chloroform, dichloroethane, chlorobenzene, dichlorobenzene and the like, but dichloromethane is preferable because of ease of handling.

The second reaction is a coupling reaction between bromide and borate ester. In general, this is a method called Suzuki coupling, which is often used in organic synthesis reactions. The palladium catalyst used in the reaction is not particularly limited as long as it shows zero valence in the reaction system. Examples include tetrakis (triphenylphosphine) palladium (0), bis [1,2-bis (diphenylphosphino) ethane] palladium (0), bis (dibenzylideneacetone) palladium (0), bis (tri- tert-butylphosphine) palladium (0) and the like. Tetrakis (triphenylphosphine) palladium (0) is preferable because of ease of handling.
The base used for the reaction is not particularly limited, whether it is inorganic or organic. Examples of inorganic substances include carbonates such as sodium carbonate, potassium carbonate, and cesium carbonate; bicarbonates such as sodium bicarbonate and potassium bicarbonate; fluorides such as potassium fluoride and cesium fluoride; and organic substances such as sodium methylate. And alcoholate compounds such as sodium ethylate, and amine compounds such as triethylamine, diisopropylethylamine and tertiary butylamine. Potassium carbonate is preferred for ease of handling. When using an inorganic salt, it is preferable to use it as an aqueous solution in order to increase the dispersibility in the reaction system.
The reaction solvent is not particularly limited as long as it does not react with the palladium catalyst or the base used. For example, aromatic solvents such as toluene and xylene, ether solvents such as 1,4-dioxane and 1,2-dimethoxyethane can be used. In the case of an aromatic solvent, it can also be used in combination with an alcohol solvent such as methanol or ethanol.

  The specific example of the substituted phenyl pyridine iridium complex of this invention is shown. In addition, the methyl group in exemplary compounds can be replaced with other alkyl groups (ethyl group, propyl group, etc.).

The substituted phenylpyridine iridium complex of the present invention has high luminescence. Therefore, it can be used as a light emitting material. In use, it is desirable to form a layer by vapor deposition.
The substituted phenylpyridine iridium complex of the present invention is useful as a material for an organic EL device, but can be used in combination with an appropriate host material. Further, it can be used as a light emitting material in a light emitting layer of an organic EL device.

Next, the organic EL element of the present invention will be described.
The organic EL device of the present invention is a device in which a plurality of organic compounds are laminated between an anode and a cathode, and contains the substituted phenylpyridine iridium complex of the present invention as a light emitting material of the light emitting layer.
The light emitting layer is composed of a light emitting material and a host material. Examples of the configuration of the multilayer organic EL device include an anode (for example, ITO) / hole transport layer / light emitting layer / electron transport layer / cathode, ITO / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode, ITO / hole transport layer / light emitting layer / hole block layer / electron transport layer / cathode, ITO / hole transport layer / light emitting layer / hole block layer / electron transport layer / electron injection layer / cathode, ITO / hole injection layer (hole Injecting layer) / hole transporting layer / light emitting layer / hole blocking layer / electron transporting layer / electron injecting layer / cathode and the like laminated. Moreover, you may have a sealing layer on a cathode as needed.
Each of the hole transport layer, the electron transport layer, and the light emitting layer preferably has a multilayer structure in which the functions are separated. In addition, the hole transport layer and the electron transport layer can be provided separately with a layer responsible for the injection function (hole injection layer and electron injection layer) and a layer responsible for the transport function (hole transport layer and electron transport layer).

Hereinafter, the constituent elements of the organic EL element of the present invention will be described by taking as an example an element structure composed of an anode / hole transport layer / light emitting layer / electron transport layer / cathode. The organic EL element of the present invention is preferably supported on a substrate.
There is no restriction | limiting in particular about the raw material of a board | substrate, For example, what is conventionally used for the conventional organic EL element can be used, and what consists of glass, quartz glass, a transparent plastic, etc. can be used.

As the anode, an electrode material is preferably a single metal having a large work function (4 eV or more), an alloy of metals having a large work function (4 eV or more), a conductive substance, or a mixture thereof. Examples of such electrode materials include gold, silver, copper and other metals, ITO (indium-tin oxide), tin oxide (SnO ₂ ), zinc oxide (ZnO), and other conductive transparent materials, polypyrrole, polythiophene, etc. The conductive polymer material is mentioned. For the anode, these electrode materials can be formed by a method such as vapor deposition, sputtering, or coating. The sheet electrical resistance of the anode is preferably several hundred Ω / cm ² or less. The thickness of the anode depends on the material, but is generally about 5 to 1,000 nm, preferably 10 to 500 nm.

As the cathode, an electrode material is preferably a single metal having a low work function (4 eV or less), an alloy of metals having a low work function (4 eV or less), a conductive substance, or a mixture thereof. Examples of such electrode materials include lithium, lithium-indium alloy, sodium, sodium-potassium alloy, magnesium, magnesium-silver alloy, magnesium-indium alloy, aluminum, aluminum-lithium alloy, aluminum-magnesium alloy, and the like. It is done. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering.
The sheet electrical resistance of the cathode is preferably several hundred Ω / cm ² or less. The thickness of the cathode depends on the material, but is generally about 5 to 1,000 nm, preferably 10 to 500 nm.
In order to efficiently extract light emitted from the organic EL device of the present invention, at least one of the anode and the cathode is preferably transparent or translucent.

The hole transport layer is made of a hole transfer compound and has a function of transmitting holes injected from the anode to the light emitting layer. When a hole transfer compound is disposed between two electrodes to which an electric field is applied and holes are injected from the anode, a hole transfer material having a hole mobility of at least 10 ⁻⁶ cm ² / V · sec or more is preferable. The hole transfer material used for the hole transport layer of the organic EL device of the present invention is not particularly limited as long as it has the above-mentioned preferable performance. A photoconductive material that has been conventionally used as a hole charge injection material or a known material that is used for a hole transport layer of an organic EL element can be selected and used.

Examples of hole transfer materials include phthalocyanine derivatives such as copper phthalocyanine, N, N, N ′, N′-tetraphenyl-1,4-phenylenediamine, N, N′-di (m-tolyl) -N, N Triarylamine derivatives such as' -diphenyl-4,4-diaminophenyl (TPD), N, N'-di (1-naphthyl) -N, N'-diphenyl-4,4-diaminophenyl (α-NPD) , Polyphenylenediamine derivatives, polythiophene derivatives, and water-soluble PEDOT-PSS (polyethylenedioxathiophene-polystyrenesulfonic acid).
The hole transport layer may be composed of one or more of these other hole transport compounds, or may be a stack of hole transport layers composed of a compound different from the hole transport material. .

Examples of the hole injection material include PEDOT-PSS (polymer mixture) and DNTPD represented by the following chemical formula. N in the formula is the number of repeating units.

Examples of the hole transport material include TPD, DTASi, α-NPD represented by the following chemical formula.

The electron transport layer is made of an electron transport material and has a function of transmitting electrons injected from the cathode to the light emitting layer. When an electron transport material is arranged between two electrodes to which an electric field is applied and electrons are injected from the cathode, an electron transport material having an electron mobility of at least 10 ⁻⁶ cm ² / V · sec or more is preferable. The electron transport material is not particularly limited as long as it has the above-mentioned preferable performance. Any one of materials conventionally used as electron charge injection materials in photoconductive materials and known materials used for electron transport layers of organic EL elements can be selected and used.
Examples of electron transport materials include quinoline complexes such as tris (8-hydroxyquinolinolato) aluminum complex (Alq ₃ ), 1-N-phenyl-2- (p-biphenylyl) -5- (p-tert -Triazine derivatives such as butylphenyl) -1,3,5-triazine (TAZ), phenanthroline derivatives such as 1,4-di (1,10-phenanthroline-2-yl) benzene (DPB), lithium fluoride And alkali metal halides.
Following the Alq ₃ and TAZ formula.

In addition to the above, an electron transport material of a triazine derivative represented by the following chemical formula (TmPyPhTAZ, see Japanese Patent Application Laid-Open No. 2007-137829), an electron transport material of a bisphenol derivative (tetra-pPyPhBP, see Japanese Patent Application Laid-Open No. 2008-066322), etc. Can also be used.

The electron transport layer may be composed of one or more of the above electron transport materials, but may be a stack of electron transport layers composed of compounds different from these.

Examples of the electron injection material include lithium fluoride (LiF), 8-hydroxyquinolinolatolithium complex (Liq) represented by the following chemical formula, lithium complex of phenanthroline derivative (LiPB, see JP 2008-106015 A), A lithium complex of phenoxypyridine (LiPP, see JP 2008-195623 A) can be mentioned.

In the light emitting layer of the organic EL device of the present invention, the substituted phenylpyridine iridium complex of the present invention is used as a light emitting material, but any other light emitting material can be selected and used in combination with the complex.
Examples of the light-emitting material used in combination include perylene derivatives, naphthacene derivatives, quinacridone derivatives, coumarin derivatives (eg, coumarin 1, coumarin 540, coumarin 545), pyran derivatives (eg, DCM-1, DCM-2, DCJTB, etc.), organometallic complexes [For example, fluorescent materials such as tris (8-hydroxyquinolinolato) aluminum complex (Alq ₃ ), tris (4-methyl-8-hydroxyquinolinolato) aluminum complex (Almq ₃ ), [2- (4,6 -Difluorophenyl) pyridyl-N, C2 '] iridium (III) picolylate (FIrpic), tris {1- [4- (trifluoromethyl) phenyl] -1H-pyrazolate-N, C2'} iridium (III) (Irtfmpppz _3), bis [2- (4 ', 6'-difluoro-phenylene ) Pyridinato -N, C2 '] iridium (III) tetrakis (1-pyrazolyl) borate (FIr6), and the like tris (2-phenylpyridinato) iridium (III) (phosphorescent material Irppy _3), etc.] .

The light emitting layer is generally formed of a host material and a light emitting material (dopant) [Appl. Phys. Lett. , 65 3610 (1989)] requires a host material when the substituted phenylpyridine iridium complex of the present invention is used in the light-emitting layer. For example, 4,4′-di (N-carbazolyl) represented by the following chemical formula: -1,1'-biphenyl (CBP), 1,4-di (N-carbazolyl) benzene-2,2'-di [4 "-(N-carbazolyl) phenyl] -1,1'-biphenyl (4CzPBP) Etc. are used.
The substituted phenylpyridine iridium complex of the present invention is preferably 0.01 to 40% by weight, more preferably 0.1 to 20% by weight, based on the host material.

In the organic EL device of the present invention, a hole injection layer composed of an organic conductor may be provided between the anode and the organic compound layer for the purpose of further improving the hole injection property. As the hole injection material used here, in addition to the substituted phenylpyridine iridium complex of the present invention, phthalocyanine derivatives such as copper phthalocyanine, polyphenylenediamine derivatives, polythiophene derivatives, PEDOT-PSS (polyethylenedioxythiophene-polystyrenesulfonic acid), etc. Is mentioned.
The formation method of the hole injection layer and the hole transport layer of the EL device containing the substituted phenylpyridine iridium complex of the present invention is not particularly limited. For example, a dry film forming method (vacuum vapor deposition method, ionization vapor deposition method, etc.), wet type A film method (solvent coating method: spin coating method, casting method, ink jet method, or the like) can be used. The film formation of the electron transport layer is limited to dry film formation methods (vacuum vapor deposition method, ionization vapor deposition method, etc.) because the lower layer may be eluted when the wet film formation method is used. For the production of the element, the above film forming method may be used in combination.
When forming each layer such as a hole transport layer, a light emitting layer, and an electron transport layer by a vacuum deposition method, the vacuum deposition conditions are not particularly limited. Usually, under a vacuum of about 10 ⁻⁵ Torr or less, a boat temperature (deposition source temperature) of about 50 to 500 ° C., a substrate temperature of about −50 to 300 ° C., and 0.01 to 50 nm / sec. Vapor deposition is preferred. When forming each layer of a positive hole transport layer, a light emitting layer, and an electron carrying layer using a some compound, it is preferable to co-evaporate the boat which put the compound, respectively controlling temperature.

When forming the hole injection layer and the hole transport layer by a solvent coating method, the components constituting each layer are dissolved or dispersed in a solvent to obtain a coating solution. Solvents include hydrocarbon solvents (heptane, toluene, xylene, cyclohexane, etc.), ketone solvents (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), halogen solvents (dichloromethane, chloroform, chlorobenzene, dichlorobenzene, etc.), ester solvents Solvents (ethyl acetate, butyl acetate, etc.), alcohol solvents (methanol, ethanol, butanol, methyl cellosolve, ethyl cellosolve, etc.), ether solvents (dibutyl ether, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc.) ), Aprotic solvents (N, N′-dimethylacetamide, dimethylsulfoxide, etc.), water and the like. The solvent may be used alone or in combination with a plurality of solvents.
The thickness of each layer such as a hole transport layer, a light emitting layer, and an electron transport layer is not particularly limited, but is usually set to 5 to 5,000 nm.

  The organic EL device of the present invention can be protected by providing a protective layer (sealing layer) for the purpose of blocking the contact of oxygen, moisture, etc., or encapsulating the device in an inert material. Examples of the inert substance include paraffin, silicon oil, and fluorocarbon. Examples of the material used for the protective layer include fluororesin, epoxy resin, silicone resin, polyester, polycarbonate, and photocurable resin.

26 to 33 show preferred configuration examples of the organic EL element of the present invention.
FIG. 26 shows a configuration in which an anode 2, a hole transport layer 5, a light emitting layer 3, an electron transport layer 6 and a cathode 4 are sequentially provided on a substrate 1. This is a separation of the functions of carrier transport and light emission, and the degree of freedom in material selection increases, so that the efficiency of light emission and the degree of freedom in light emission color increase.
FIG. 27 shows a structure in which an anode 2, a hole injection layer 7, a hole transport layer 5, a light emitting layer 3, an electron transport layer 6 and a cathode 4 are sequentially provided on a substrate 1. In this case, the provision of the hole injection layer 7 increases the adhesion between the anode 2 and the hole transport layer 5, improves the injection of holes from the anode, and is effective in lowering the voltage of the light emitting element.
FIG. 28 shows a structure in which an anode 2, a hole transport layer 5, a light emitting layer 3, an electron transport layer 6, an electron injection layer 8 and a cathode 4 are sequentially provided on a substrate 1. In this case, injection of electrons from the cathode 4 is improved, which is effective for lowering the voltage of the light emitting element.
FIG. 29 shows a structure in which an anode 2, a hole injection layer 7, a hole transport layer 5, a light emitting layer 3, an electron transport layer 6, an electron injection layer 8 and a cathode 4 are sequentially provided on a substrate 1. In this case, hole injection from the anode 2 is improved and electron injection from the cathode 4 is improved, which is the most effective for low voltage driving.

30 to 33 are configuration examples in which a hole block layer is inserted into an organic EL element.
The hole blocking layer has an effect of preventing holes injected from the anode or excitons generated by recombination in the light emitting layer 3 from escaping to the cathode 4, and is effective in improving the light emission efficiency of the organic EL element. . The hole blocking layer 9 can be inserted between the light emitting layer 3 and the cathode 4, between the light emitting layer 3 and the electron transport layer 6, or between the light emitting layer 3 and the electron injection layer 8. Preferred is between the light emitting layer 3 and the electron transport layer 6.
Each of the hole transport layer 5, the hole injection layer 7, the electron transport layer 6, the electron injection layer 8, the light emitting layer 3, and the hole block layer 9 may have a single layer structure or a multilayer structure.
26 to 33 are basic element configurations to the last, and the configuration of the organic EL element of the present invention is not limited to this.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.

Example 1
(1) Synthesis of tris [2- (3-bromophenyl) pyridine] iridium complex [Ir (Br-ppy) ₃ ]


To a 300 mL four-necked flask, 0.5 g (0.77 mmol) of Ir (ppy) ₃ , 115 mL of dichloromethane and 0.58 g (3.14 mmol) of N-bromosuccinimide were added, and the mixture was stirred at room temperature for 16 hours under a nitrogen stream. . The reaction solution was concentrated to several tens mL, suction filtered, and then washed with water and methanol. Then, it dried under reduced pressure at 60 degreeC for 7 hours, and obtained the yellow powder (0.68g, yield 99%). Identification was performed by ¹ H-NMR. A chart of ¹ H-NMR is shown in FIG.

(2) Synthesis of tris {2- [3- (4-pyridyl) phenyl] pyridine} iridium complex Ir (4Py-ppy) ₃
In a 100 mL four-necked flask, 0.20 g (0.22 mmol) of Ir (Br-ppy) ₃ , 0.46 g (2.24 mmol) of 4-pyridineboronic acid pinacol ester, 20 mL of dioxane, 10 mL of 2M K ₂ CO ₃ aq In addition, nitrogen bubbling was performed for 1 hour, 13 mg (0.011 mmol) of Pd (PPh ₃ ) ₄ [tetrakis (triphenylphosphine) palladium] was added, and the mixture was refluxed for 19 hours under a nitrogen stream (85 ° C.). The progress of the reaction was confirmed by thin layer chromatography, and when the consumption of the raw material was confirmed, the reaction solution was extracted with dichloromethane and washed with water. Subsequently, silica gel column chromatography was performed using dichloromethane: methanol = 24: 1 to obtain 0.18 g (yield 91%) of a yellow solid. Identification was performed by ¹ H-NMR and Mass spectrum. A chart of ¹ H-NMR is shown in FIG. 2, and a chart of Mass spectrum is shown in FIG.
Moreover, the high vacuum sublimation purification of the obtained yellow solid was performed 5 times, changing sublimation conditions. Table 1 shows each sublimation condition and yield.
Table 2 shows the results of elemental analysis of the obtained sublimation product.

Purity analysis was also performed using a high performance liquid chromatograph. A THF solution having a sample concentration of 0.10 g / L was prepared and measured at an injection amount of 5.0 μL, mobile phase THF: water = 1: 2, a flow rate of 1.000 mL / min, a column oven temperature of 40 ° C., and a detection wavelength of 340 nm. The obtained chart is shown in FIG. As a result of the measurement, the purity was 99.8%, and it was found that the purity did not hinder device evaluation.

Example 2
Synthesis of tris {2- [3- (3-pyridyl) phenyl] pyridine} iridium complex Ir (3Py-ppy) ₃
In a 100 mL four-necked flask, 0.30 g (0.34 mmol) of Ir (Br-ppy) ₃ , 0.70 g (3.4 mmol) of 3-pyridineboronic acid pinacol ester, 30 mL of dioxane, 15 mL of 2M K ₂ CO ₃ aq In addition, nitrogen bubbling was performed for 1 hour, 19.6 mg (0.017 mmol) of Pd (PPh ₃ ) ₄ was added, and the mixture was refluxed for 20 hours under a nitrogen stream (85 ° C.). The progress of the reaction was confirmed by thin layer chromatography, and when the consumption of the raw material was confirmed, the reaction solution was extracted with dichloromethane and washed with water. Subsequently, silica gel column chromatography was performed with dichloromethane: methanol = 32: 1 to obtain 0.29 g (yield 96%) of a yellow solid. Identification was performed by ¹ H-NMR. Regarding the mass spectrum, the material did not fly and no peak could be detected. ^{The 1} H-NMR chart is shown in FIG.
Moreover, the high vacuum sublimation purification of the obtained yellow solid was performed 4 times, changing sublimation conditions. Table 3 shows each sublimation condition and yield.
Table 4 shows the results of elemental analysis of the obtained sublimation product.

Purity analysis was also performed using a high performance liquid chromatograph. A THF solution having a sample concentration of 0.10 g / L was prepared, and measurement was performed at an injection amount of 5.0 μL, a mobile phase THF: water = 1: 2, a flow rate of 1.000 mL / min, a column oven temperature of 40 ° C., and a detection wavelength of 284 nm. The obtained chart is shown in FIG. As a result of the measurement, the purity was 99.3%, and it was found that the purity did not hinder device evaluation.

Examples 3-4
Was thermogravimetric test of Example 1 synthesized Ir _{(4Py-ppy) 3} and synthesized Ir in Example 2 _{(3Py-ppy) 3.} Since the thermal decomposition temperature can be estimated by measuring the thermogravimetry, the 5% weight decay temperature was determined as the thermal decomposition start temperature.
Table 5 shows the measurement results.
While third place replacement of Ir _{(3Py-ppy) 3} those of the four-substituted of Ir _{(4Py-ppy) 3} than has become higher "Td5%", which is more of a four-substituted third place than replacement This is thought to be due to easy hydrogen bonding.

Examples 5-6, Comparative Example 1
The solubility test of Ir (4Py-ppy) ₃ synthesized in Example 1 and Ir (3Py-ppy) ₃ (Example 6) synthesized in Example 2 was performed. The solubility results of Ir (4Py-ppy) ₃ (Example 5) are shown in Table 6, and the solubility results of Ir (3Py-ppy) ₃ (Example 6) are shown in Table 7. For comparison, a solubility test of Ir (ppy) ₃ which is a raw material of the compound of the present invention was also conducted (Comparative Example 1). The results are shown in Table 8.
In the solubility test, each solvent was added to 5.0 mL in increments of 0.5 mL with respect to 1.0 mg of the compound, and heating was not performed.
〔Evaluation criteria〕
×: When not dissolved at all △: When dissolved even a little ○: When almost dissolved ◎: When completely dissolved

It showed good solubility in 2-ethoxyethanol, cyclohexanone, and ethyl benzoate. The order of solubility is shown below.
2-ethoxyethanol>cyclohexanone> ethyl benzoate>toluene>1-butanol>tetralin>m-xylene>mesitylene> 2-propanol

Good solubility in cyclohexanone and ethyl benzoate. The order of solubility is shown below.
Cyclohexanone, ethyl benzoate>tetralin>2-ethoxyethanol>mesitylene>m-xylene>toluene>2-propanol> 1-butanol

Toluene and cyclohexanone showed a certain degree of solubility, but the others were hardly soluble. The order of solubility is shown below.
Toluene = cyclohexanone>m-xylene> ethyl benzoate>tetralin>2-ethoxyethanol>mesitylene> 1-butanol = 2-propanol

As a result of the test, it was found that Ir (4Py-ppy) ₃ and Ir (3Py-ppy) ₃ of the present invention have better solubility than Ir (ppy) ₃ .

Examples 7-8, Comparative Example 2
Synthesized in Example 1 was Ir _{(4Py-ppy) 3} and Ir synthesized in Example 2 _{(3Py-ppy) 3} of the UV - to measure the visible absorption spectrum (UV-vis absorption spectra) (Example 7 and Example 8). For comparison, the ultraviolet-visible absorption spectrum of Ir (ppy) ₃ as these raw materials was also measured (Comparative Example 2).
A solution sample was prepared by preparing a 1,2-dichloroethane solution for ^10-5 mol / L spectroscopic analysis and a THF solution, and using a quartz cell. FIG. 7 shows the measurement result of the 1,2-dichloroethane solution, and FIG. 8 shows the measurement result of the THF solution.
Compared with Ir (ppy) ₃ , Ir (3Py-ppy) ₃ and Ir (4Py-ppy) ₃ have a larger absorption in the pyridine ring.

Examples 9 to 10, Comparative Example 3
Photoluminescence spectra (PL spectra) in a solution of Ir (4Py-ppy) ₃ synthesized in Example 1 and Ir (3Py-ppy) ₃ synthesized in Example 2 were measured (Examples 9 and 10). ). For comparison, the PL spectrum of Ir (ppy) ₃ as these raw materials was also measured (Comparative Example 3). As a solution sample, a THF solution for 10 ⁻⁵ mol / L spectroscopic analysis was prepared and measured using a quartz cell. The measurement was performed after the solution was purged with nitrogen. The measurement result of the THF solution is shown in FIG.
The peak wavelength (λmax) of the PL spectrum in a THF solution of Ir (ppy) ₃ , Ir (3Py-ppy) ₃ and Ir (4Py-ppy) ₃ was 514 nm, 513 nm, and 504 nm, respectively.

Examples 11-12, Comparative Example 4
Synthesized Ir _{(4Py-ppy) 3} and Ir synthesized in Example 2 _(3Py-ppy) Ultraviolet at ₃ thin film in Example 1 - was determined visible absorption spectrum (UV-vis absorption spectra) (Example 11, Example 12). For comparison, the ultraviolet-visible absorption spectrum of Ir (ppy) ₃ as these raw materials was also measured (Comparative Example 4). The measurement was performed by preparing a deposited film in which 8 wt% of each iridium complex was doped into CBP. The results are shown in FIG.

Examples 13-14, Comparative Example 5
Synthesized in Example 1 was Ir _{(4Py-ppy) 3} and Example 2 with synthesized Ir _{(3Py-ppy) 3} of the photoluminescence spectrum of a thin film form a (PL spectrum) was measured (Example 13, Example 14 ). For comparison, a photoluminescence spectrum (PL spectrum) of Ir (ppy) ₃ as these raw materials was also measured (Comparative Example 5). The measurement was performed by preparing a deposited film in which 8 wt% of each iridium complex was doped into CBP.
The results are shown in FIG.
The peak wavelengths (λmax) of PL spectra in Ir (ppy) ₃ , Ir (3Py-ppy) ₃ , and Ir (4Py-ppy) ₃ CBP 8 wt% doped films are 519 nm, 511 nm, and 508 nm, respectively. There was little change in the emission wavelength.

Examples 15-16, Comparative Example 6
Ir synthesized in Example 1 _{(4Py-ppy) 3} and Example 2 with synthesized Ir _{(3Py-ppy) 3} of the photoluminescence quantum yield (PLQY) was measured (Example 15, Example 16). For comparison, the photoluminescence quantum yield of Ir (ppy) ₃ as these raw materials was also measured (Comparative Example 6). The measurement was performed using a integrating sphere manufactured by Hamamatsu Photonics by preparing a deposited film in which 4 wt% and 8 wt% of each iridium complex were doped in CBP. The results are shown in Table 9.
As can be seen from the results in the table, each iridium complex showed a high value comparable to Ir (ppy) ₃ , and concentration dependency could not be confirmed.

Examples 17-18, Comparative Example 7
Organic EL devices using Ir (4Py-ppy) ₃ synthesized in Example 1 and Ir (3Py-ppy) ₃ synthesized in Example 2 were prepared (Examples 17 and 18). TAPC {di- [4- (N, N-ditolylamino) -phenyl] cyclohexane} represented by the following formula [Chemical Formula 24] is represented in the hole transport layer, and the following formula [Chemical Formula 25] is represented in the electron transport layer. B3PyPB [3,3 ", 5,5" -tetra (pyridin-3-yl) -1,1 ', 3', 1 "-terphenyl] was used for comparison. An organic EL device using (ppy) ₃ was also produced (Comparative Example 7).
The produced organic EL element structure is shown in FIG. Each iridium complex was doped with CBP at 4 wt%. The structure of the produced organic EL element is as follows.
Example 17: ITO (anode) / TAPC (hole transport layer) (50 nm) / CBP: 4 wt%, Ir (4Py-ppy) ₃ (light emitting layer) (10 nm) / B3PyPB (electron transport layer) (50 nm) / LiF (Electron injection layer) (1 nm) / Al (cathode) (80 nm)
Example 18: ITO (anode) / TAPC (hole transport layer) (50 nm) / CBP: 4 wt%, Ir (3Py-ppy) ₃ (light emitting layer) (10 nm) / B3PyPB (electron transport layer) (50 nm) / LiF (Electron injection layer) (1 nm) / Al (cathode) (80 nm)
Comparative Example 7: ITO (anode) / TAPC (hole transport layer) (50 nm) / CBP: 4 wt%, Irppy ₃ (light emitting layer) (10 nm) / B3PyPB (electron transport layer) (50 nm) / LiF (electron injection layer) (1 nm) / Al (cathode) (80 nm)

FIG. 13 shows the current density-voltage characteristics of each organic EL element, FIG. 14 shows the brightness-voltage characteristics, FIG. 15 shows the power efficiency-luminance characteristics, FIG. 16 shows the current efficiency-luminance characteristics, and FIG. 17 and FIG. 18 shows the EL spectrum.
Table 10 shows the voltage, power efficiency, current efficiency, and external quantum efficiency at 100 cd / m ² and 1000 cd / m ² of each organic EL element.

Examples 19-20, Comparative Example 8
Organic EL devices using Ir (4Py-ppy) ₃ synthesized in Example 1 and Ir (3Py-ppy) ₃ synthesized in Example 2 were prepared (Example 19 and Example 20). For comparison, devices using these raw materials Ir (ppy) ₃ were also produced (Comparative Example 8).
The produced organic EL element structure is shown in FIG. Each iridium complex was doped with CBP at 8 wt%. The structure of the produced organic EL element is as follows.
Example 19: ITO (anode) / TAPC (hole transport layer) (50 nm) / CBP: 8 wt%, Ir (4Py-ppy) ₃ (light emitting layer) (10 nm) / B3PyPB (electron transport layer) (50 nm) / LiF (Electron injection layer) (1 nm) / Al (cathode) (80 nm)
Example 20: ITO (anode) / TAPC (hole transport layer) (50 nm) / CBP: 8 wt%, Ir (3Py-ppy) ₃ (light emitting layer) (10 nm) / B3PyPB (electron transport layer) (50 nm) / LiF (Electron injection layer) (1 nm) / Al (cathode) (80 nm)
Comparative Example 8: ITO (anode) / TAPC (hole transport layer) (50 nm) / CBP: 8 wt%, Irppy ₃ (light emitting layer) (10 nm) / B ₃ PyPB (electron transport layer) (50 nm) / LiF (electron injection layer) (1 nm) / Al (cathode) (80 nm)

FIG. 20 shows the current density-voltage characteristics of each organic EL element, FIG. 21 shows the brightness-voltage characteristics, FIG. 22 shows the power efficiency-luminance characteristics, FIG. 23 shows the current efficiency-luminance characteristics, and FIG. FIG. 24 shows the EL spectrum and FIG. 25 shows the EL spectrum.
Table 11 shows the voltage, power efficiency, current efficiency, and external quantum efficiency at 100 cd / m ² and 1000 cd / m ² of each organic EL element.

Further, the organic EL device of the present invention can be used as a normal DC drive device. When a DC voltage is applied, light emission is usually observed when about 1.5 to 20 V is applied with the positive polarity of the anode and the negative polarity of the cathode. It can also be used as an AC drive element. When an AC voltage is applied, light is emitted when the anode is in a positive state and the cathode is in a negative state.
The organic EL element of the present invention includes, for example, a flat light emitter such as an electrophotographic photosensitive member and a flat panel display, a copying machine, a printer, a backlight of a liquid crystal display, a light source such as an instrument, various light emitting elements, various display devices, various signs It can be used for various sensors and various accessories.

1 Substrate 2 Anode (ITO)
DESCRIPTION OF SYMBOLS 3 Light emitting layer 4 Cathode 5 Hole transport layer 6 Electron transport layer 7 Hole injection layer 8 Electron injection layer 9 Hole block layer

Claims (3)

A substituted phenylpyridine iridium complex represented by the following general formula (1).
[Wherein, R ^{1 to} R ⁴ are groups independently selected from the group consisting of hydrogen and a linear or branched alkyl group having 1 to 4 carbon atoms, and R ^{5 to} R ⁷ are hydrogen and 1 carbon atom. -4 linear or branched alkyl groups, C 1-4 linear or branched alkoxy groups, and groups independently selected from the group consisting of fluorine. Py is a group selected from the group consisting of a 3-pyridyl group or a 4-pyridyl group represented by the following formula, and R ^{8 to} R ¹⁵ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. Each independently selected from the group consisting of ]
  A luminescent material comprising the substituted phenylpyridine iridium complex according to claim 1.   An organic EL device using the substituted phenylpyridine iridium complex according to claim 1.