Light-emitting element

Abstract

To provide a light emitting element reduced in drive voltage and excellent in durability.SOLUTION: In a light emitting element to emit light by electric energy, at least an organic thin film layer and a light emitting layer are present between an anode and a cathode, where the organic thin film layer contains a phenanthroline derivative represented by the general formula (1) in the figure and containing iodine.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to a light-emitting element. [Background technology]

[0002] Phenanthroline derivatives are useful compounds as light-emitting materials for, for example, display elements, flat panel displays, backlights, lighting, interiors, signs, billboards, electrophotographers, and optical signal generators. As a light-emitting element using a phenanthroline derivative, for example, a light-emitting element has been proposed in which a light-emitting material is present between a positive electrode and a negative electrode and emits light in response to electrical energy, and the element is characterized in that it contains an organic phosphor having a phenanthroline skeleton (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2001-267080 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, light-emitting elements such as organic electroluminescent elements have improved in durability and are becoming a replacement for liquid crystal elements in mobile applications such as smartphones, with the light-emitting element described in Patent Document 1 being one such example. However, display elements used for long-term applications such as in-car displays and televisions require even longer-term durability than those used in mobile applications, and further reduction of the driving voltage and improvement of durability are required for application in these fields. The invention described in Patent Document 1 is no exception in this regard. Under these circumstances, the present invention aims to further improve durability by discovering the hidden properties of iodine, which has conventionally been targeted for removal as an impurity in element materials.

[0005] In view of the problems of these prior art, the present invention aims to provide a light-emitting element with reduced driving voltage and excellent durability. [Means for solving the problem]

[0006] The present invention relates to a light-emitting element in which at least an organic thin film layer and a light-emitting layer are present between an anode and a cathode, and which emits light in response to electrical energy, wherein the organic thin film layer contains a phenanthroline derivative represented by the following general formula (1), which contains iodine.

[0007] [ka]

[0008] In the above general formula (1), R2 to R7 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryloxy group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkylthio group, an arylthio group, or a cyano group. R1 and R8 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group. However, at least one of R1 and R8 is a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group. [Effects of the Invention]

[0009] The present invention provides a light-emitting element with reduced driving voltage and even greater durability than conventional elements. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view of an example of a light-emitting element of the present invention. [Figure 2] This is a schematic cross-sectional view of another example of the light-emitting element of the present invention. [Figure 3] This is a schematic cross-sectional view of another example of the light-emitting element of the present invention. [Modes for carrying out the invention]

[0011] The present invention will be described below.

[0012] The light-emitting element of the present invention emits light in response to electrical energy, and at least an organic thin film layer and a light-emitting layer are present between the anode and the cathode. The light-emitting layer is a layer that emits light due to excitation energy generated by the recombination of holes and electrons. The organic thin film layer is a layer other than the light-emitting layer that contains the phenanthroline derivative represented by the general formula (1) above. Examples of such organic thin film layers include the n-type charge generation layer, electron transport layer, and electron injection layer described later. The n-type charge generation layer is a layer that generates or separates electrons by applying a voltage and supplies electrons to adjacent layers. The electron transport layer is a layer that transports electrons injected from the cathode or the n-type charge generation layer to the light-emitting layer. The electron injection layer is a layer that assists in the injection of electrons from the cathode to the electron transport layer. The n-type charge generation layer, electron transport layer, and electron injection layer may each have a stacked structure of two or more layers.

[0013] Figures 1 to 4 show examples of schematic cross-sectional views of the light-emitting element of the present invention. The light-emitting element 1 shown in Figure 1 has an organic thin film layer 6, an emissive layer 5, and a cathode 3 on an anode 2 in that order. The light-emitting element 1 shown in Figure 2 has an emissive layer 5, an organic thin film layer 6, and a cathode 3 on an anode 2 in that order. The light-emitting element 1 shown in Figure 3 has organic thin film layers 6 and emissive layers 5 alternately stacked on an anode 2, with a cathode 3 on the upper organic thin film layer 6. That is, the organic thin film layer 6 may be formed between the anode 2 and the emissive layer 5 (see Figure 1), or between the cathode 3 and the emissive layer 5 (see Figure 2). Also, in the case of a tandem structure in which multiple emissive layers 5 are formed, it may be formed between the emissive layers 5. Furthermore, the organic thin film layer 6 may also be formed between the anode 2 and the emissive layer 5, or between the cathode 3 and the emissive layer 5 (see Figure 3). Furthermore, the organic thin film layer 6 may be a layer formed by stacking multiple layers.

[0014] The light-emitting device of the present invention is characterized in that the organic thin film layer contains a phenanthroline derivative represented by the following general formula (1) and containing iodine.

[0015] [Chemical formula]

[0016] In the above general formula (1), R2 to R7 may be the same or different, and represent a hydrogen atom, a substituted or unsubstituted aryl group, heteroaryl group, alkyl group, cycloalkyl group, alkoxy group, aryloxy group, alkenyl group, cycloalkenyl group, alkynyl group, alkylthio group, arylthio group or cyano group. Among these, a hydrogen atom is preferable, and since the steric hindrance is small, the reaction at the position of R1 and / or R8 can proceed efficiently.

[0017] R1 and R8 may be the same or different, and represent a hydrogen atom, a substituted or unsubstituted aryl group, heteroaryl group, alkyl group or cycloalkyl group. However, at least one of R1 and R8 is a substituted or unsubstituted aryl group, heteroaryl group, alkyl group or cycloalkyl group. R1 and R@ are preferably a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, which has a high glass transition temperature and can improve heat resistance. Further, since the electron mobility increases, the driving voltage can be further reduced. A substituted or unsubstituted aryl group is more preferable, and a substituted or unsubstituted phenyl group is even more preferable.

[0018] In the general formula (1) above, the aryl group is an aromatic hydrocarbon group obtained by removing one hydrogen atom from the aromatic ring of an aromatic hydrocarbon compound, and may be either a monocyclic or fused ring. Examples of aryl groups include phenyl, naphthyl, fluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, anthracenyl, benzophenanthryl, benzoanthracenyl, chrysenyl, pyrenyl, fluoranthenyl, triphenylenyl, benzofluoranthenyl, dibenzoanthracenyl, perilenyl, and hericenyl groups. Among these, phenyl, naphthyl, fluorenyl, phenanthryl, anthracenyl, pyrenyl, fluoranthenyl, and triphenylenyl groups are preferred. The aryl group may be substituted or unsubstituted. Examples of substituents include phenyl, naphthyl, fluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, phenanthrolinyl, anthracenyl, benzophenanthryl, benzoanthracenyl, chrysenyl, pyrenyl, fluoranthenyl, triphenylenyl, benzofluoranthenyl, dibenzoanthracenyl, perilenyl, and hericenyl groups. Among these, phenyl, naphthyl, fluorenyl, phenanthryl, phenanthrolinyl, anthracenyl, pyrenyl, fluoranthenyl, and triphenylenyl groups are preferred. These substituents may be further substituted. In this invention, groups in which multiple phenyl groups are bonded via single bonds, such as biphenyl and terphenyl groups, are treated as phenyl groups having an aryl group as a substituent. The number of ring-forming carbon atoms in the aryl group is not particularly limited, but is preferably in the range of 6 to 40, more preferably 6 to 30. In the case of a phenyl group, if there are substituents on two adjacent carbon atoms in the phenyl group, these substituents may form a ring structure with each other. The resulting group may, depending on its structure, fall into one or more of the following categories: "substituted phenyl group," "aryl group having a fused ring structure of two or more rings," or "heteroaryl group having a fused ring structure of two or more rings."

[0019] A heteroaryl group is a cyclic aromatic group having one or more atoms other than carbon and hydrogen, i.e., heteroatoms, within its ring, and may be either a monocyclic or fused ring. Nitrogen, oxygen, and sulfur atoms are preferred as heteroatoms. Examples of heteroaryl groups include pyridyl, furanyl, thienyl, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidyl, pyridadinyl, triazinyl, naphthilidinyl, synnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzothienyl, indolyl, dibenzofuranyl, dibenzothienyl, carbazolyl, benzocarbazolyl, carbolinyl, indrocarbazolyl, benzoflocarbazolyl, benzothienocarbazolyl, dihydroindenocarbazolyl, benzoquinolinyl, acridinyl, dibenzoacridinyl, benzimidazolyl, imidazopyridyl, benzoxazolyl, benzothiazolyl, and phenanthrolinyl. Heteroaryl groups may be substituted or unsubstituted. Examples of substituents that may be substituted include the aforementioned aryl group, heteroaryl group, and alkyl group described later. The number of ring-forming carbon atoms in the heteroaryl group is not particularly limited, but is preferably in the range of 2 to 40, and more preferably 2 to 30.

[0020] Alkyl groups refer to saturated aliphatic hydrocarbon groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, and pentyl groups, and may be substituted or unsubstituted. Examples of substituents when substituted include the aforementioned aryl groups, heteroaryl groups, and alkoxy groups described later. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 1 to 20, and more preferably 1 to 8.

[0021] A cycloalkyl group refers to a saturated alicyclic hydrocarbon group such as a cyclopropyl group, cyclohexyl group, norbornyl group, or adamantyl group, and may be substituted or unsubstituted. Examples of substituents when substituted include the aforementioned aryl group, heteroaryl group, and alkoxy group, which will be described later. The number of ring-forming carbon atoms in a cycloalkyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0022] An alkoxy group refers to a functional group in which an aliphatic hydrocarbon group is bonded via an ether linkage, such as a methoxy group, ethoxy group, or propoxy group, and the aliphatic hydrocarbon group may be substituted or unsubstituted. Examples of substituents that can be substituted include the aforementioned aryl group, heteroaryl group, and alkoxy group. The number of carbon atoms in the alkoxy group is not particularly limited, but is preferably in the range of 1 to 20.

[0023] An aryloxy group refers to a functional group in which an aromatic hydrocarbon group is bonded via an ether bond, such as a phenoxy group, and the aromatic hydrocarbon group may be substituted or unsubstituted. Examples of substituents when substituted include the groups exemplified as substituents for aryl groups. The number of ring-forming carbon atoms in the aryloxy group is not particularly limited, but is preferably in the range of 6 to 40.

[0024] An alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group or a butadienyl group, which may be substituted or unsubstituted. Examples of substituents that can be substituted include the aforementioned aryl group, heteroaryl group, and alkoxy group. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0025] A cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, cyclopentadienyl group, or cyclohexenyl group, which may be substituted or unsubstituted. Examples of substituents that can be substituted include the aforementioned aryl group, heteroaryl group, and alkoxy group. The number of ring-forming carbon atoms in a cycloalkenyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0026] An alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, and may be substituted or unsubstituted. Examples of substituents that can be substituted include the aforementioned aryl group, heteroaryl group, and alkoxy group. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0027] An alkylthio group is a group in which the oxygen atom of the ether bond of an alkoxy group is replaced by a sulfur atom. The aliphatic hydrocarbon group of the alkylthio group may be substituted or unsubstituted. Examples of substituents that can be substituted include the groups exemplified as substituents for alkyl groups. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0028] An arylthio group is formed in which the oxygen atom in the ether bond of an aryloxy group is replaced by a sulfur atom. The aromatic hydrocarbon group in the arylthio group may be substituted or unsubstituted. Examples of substituents that can be substituted include those exemplified as substituents for aryl groups. The number of ring-forming carbon atoms in the arylthio group is not particularly limited, but is preferably in the range of 6 to 40.

[0029] A cyano group is a functional group whose structure is represented by -C≡N. In this case, it is bonded to a carbon atom.

[0030] Examples of phenanthroline derivatives represented by the above general formula (1) include the compounds listed below.

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] Among these, basocproine, 1,3-bis(1,10-phenanthrolin-9-yl)benzene, 1,3-bis[(1,10-phenanthrolin-2-yl)methyl]-2,4,6-triethylbenzene, 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline, and 2-[4-(9-phenantrenyl)-1-naphthalenyl]-1,10-phenanthroline are preferred due to their ease of synthesis and availability of raw materials, with 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline and 2-[4-(9-phenantrenyl)-1-naphthalenyl]-1,10-phenanthroline being more preferred.

[0036] The present invention is characterized in that the phenanthroline derivative represented by general formula (1) contains iodine. However, "containing iodine" means that it is included as a useful additive, not as part of the structure of the phenanthroline derivative. By containing iodine in the phenanthroline derivative, the driving voltage of the light-emitting element can be reduced and its durability improved due to the element trapping effect and conductivity improvement effect.

[0037] Halogens such as iodine are generally considered to be impurities generated during the reaction process of the host material contained in the light-emitting layer. It is common knowledge among those skilled in the art to keep the mass concentration of halogens such as iodine as low as possible, and in order to increase the luminescence brightness and efficiency and extend the lifespan, halogens are removed as much as possible by separation treatments such as crystallization and high-performance liquid chromatography. Such treatments are also performed in the invention of Patent Document 1, which forms layers other than the light-emitting layer, but in the present invention, we focus on the above-mentioned effects of iodine and include it in the phenanthroline derivative as a useful additive.

[0038] The iodine content of the phenanthroline derivative represented by general formula (1) is preferably 60 ppm or more, which can further reduce the driving voltage and improve durability. On the other hand, the iodine content is preferably 10,000 ppm or less, which can suppress electrode corrosion such as alkali migration, further reduce the driving voltage, and further improve durability.

[0039] Here, the iodine content of phenanthroline derivatives can be measured by X-ray fluorescence analysis. Specifically, the phenanthroline derivative is compressed using a press, and the surface is covered with a polypropylene film to suppress volatilization from the surface, and this is used as the measurement sample. The obtained measurement sample is irradiated with primary X-rays using an X-ray fluorescence analyzer, and the intensity of the iodine fluorescence X-rays that appear when the iodine returns from the excited state to the ground state is measured. The iodine content is calculated from a calibration curve prepared in advance using samples with known iodine content.

[0040] The iodine content of the phenanthroline derivative represented by general formula (1) can be determined, for example, by adding an appropriate amount of iodine compound according to the weight of the phenanthroline derivative, or by using iodine as an oxidizing agent in the method for producing the phenanthroline derivative described later. In the latter case, the iodine content can be easily adjusted to a desired range by adjusting the washing conditions of the crude product of the oxidized phenanthroline derivative.

[0041] Methods for producing phenanthroline derivatives represented by general formula (1) include, for example, a method in which a phenanthroline derivative represented by general formula (1) is synthesized by a coupling reaction of a palladium-based aryl halide derivative and an arylboronic acid derivative, and then an appropriate amount of iodine or an iodine compound is added to adjust the iodine content, or a flow reaction method using a narrow-tube type reaction vessel (reactor) with iodine as the oxidizing agent. In the former case, it is preferable to add a solution in which iodine or an iodine compound is dissolved in a solvent. Examples of solvents include tetrahydrofuran and ethanol. Flow reactions using iodine as the oxidizing agent are preferred because they are highly productive and do not require the addition of iodine later.

[0042] In a method for producing phenanthroline derivatives, when iodine is used as an oxidizing agent, it is preferable to wash the crude product of the phenanthroline derivative after oxidation. For washing, it is preferable to use an aqueous sodium thiosulfate solution. More specifically, the crude product of the phenanthroline derivative after oxidation is washed with an aqueous sodium thiosulfate solution and then rinsed with water to remove the iodine contained therein by the reducing agent sodium thiosulfate. In addition, if an iodide salt (lithium iodide) is formed in the reaction system, this is also removed by rinsing with water. Since the amount of iodine removed changes depending on the concentration of the aqueous sodium thiosulfate solution, the number of washes, and the number of rinses with water, it is preferable to select these conditions according to the desired iodine content.

[0043] Next, toluene is added and the slurry is washed by heating. Then, ethanol, which has high solubility for iodine and iodide salts (lithium iodide), is added and the slurry is washed by heating. After that, purification by crystallization and sublimation is preferable. For crystallization, anisole / toluene solution is preferred, and after sublimation, a tetrahydrofuran / methanol solution is preferred.

[0044] For example, if the iodine content of the crude product of the phenanthroline derivative after oxidation is tens of thousands of ppm, washing the solution twice with a 0.5 M sodium thiosulfate aqueous solution, followed by rinsing with water, then adding 50 ml of ethanol per 1 g of sample, heating at 80°C for 1 hour to wash the slurry, and then crystallizing and sublimating using the method described above, the iodine content will be approximately 1 ppm to 60 ppm. If only rinsing with water, crystallization, and sublimation are performed without washing with sodium thiosulfate aqueous solution, the iodine content will be approximately 60 ppm to 600 ppm. If only crystallization and sublimation are performed, the iodine content will be approximately 600 ppm to 1,000 ppm.

[0045] The organic thin film layer preferably contains alkali metal atoms and / or rare earth metal atoms in addition to the aforementioned phenanthroline derivative. By including alkali metal atoms and / or rare earth metal atoms, the reaction between iodine and other components can be suppressed, stabilizing iodine as a metal salt, and the effects of the present invention can be more significantly realized. Furthermore, the conductivity of alkali metal atoms and / or rare earth metal atoms contributes to the transfer of electrons and holes. Therefore, if the organic thin film layer is a charge generation layer, electron transport layer, electron injection layer, hole transport layer, or hole generation layer related to the transfer of electrons and holes, it is particularly preferable to include alkali metal atoms and / or rare earth metal atoms.

[0046] The configuration of the light-emitting element of the present invention will be described in more detail. The layer configuration between the anode and cathode in the light-emitting element of the present invention can be a stacked configuration such as 1) light-emitting layer / electron transport layer, 2) hole transport layer / light-emitting layer / electron transport layer, 3) hole injection layer / hole transport layer / light-emitting layer / electron transport layer, 4) hole transport layer / light-emitting layer / electron transport layer / electron injection layer, 5) hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer, or 6) hole injection layer / hole transport layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer.

[0047] Furthermore, the above-described laminated configuration may be a tandem type in which multiple layers are stacked with an intermediate layer in between. The intermediate layer is generally also called an intermediate electrode, intermediate conductive layer, charge generation layer, electron extraction layer, connecting layer, or intermediate insulating layer. Specific examples of the tandem type include, for example, 7) hole transport layer / light-emitting layer / electron transport layer / charge generation layer / hole transport layer / light-emitting layer / electron transport layer, and 8) hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer / charge generation layer / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer, which include a charge generation layer as an intermediate layer between anode 2 and cathode 3.

[0048] Furthermore, each of the above layers may be a single layer or multiple layers, and may be doped. In particular, the electron injection layer and charge generation layer are preferably metal-doped layers, which can improve electron transport capability and electron injection capability to adjacent layers. In addition, a protective layer (cap layer) may be further included in addition to the above layers, which can further improve luminescence efficiency through optical interference effects. The aforementioned organic thin film layer in the present invention may be used in any of the above layers except for the light-emitting layer, but is particularly suitable for use in the electron transport layer, charge generation layer, and electron injection layer. For example, a configuration in which at least an electron transport layer and a light-emitting layer are provided between the anode and cathode, and the aforementioned organic thin film layer is used as the electron transport layer; a configuration in which at least a charge generation layer and a light-emitting layer are provided between the anode and cathode, and the aforementioned organic thin film layer is used as the charge generation layer; and a configuration in which at least an electron injection layer and a light-emitting layer are provided between the anode and cathode, and the aforementioned organic thin film layer is used as the electron injection layer. The aforementioned organic thin film layer may also be used in two or more layers excluding the light-emitting layer.

[0049] In the light-emitting element according to an embodiment of the present invention, the anode and cathode serve to supply a sufficient current for the element to emit light, and it is desirable that at least one of them be transparent or semi-transparent in order to extract light. Typically, the anode 2 formed on the substrate is a transparent electrode.

[0050] (substrate) To maintain the mechanical strength of the light-emitting element, it is preferable to form the light-emitting element on a substrate. Examples of substrates include glass substrates such as soda glass or alkali-free glass, and plastic substrates. The thickness of the glass substrate only needs to be sufficient to maintain mechanical strength; 0.5 mm or more is sufficient. Regarding the glass material, it is preferable that there are few ions eluted from the glass, and alkali-free glass is preferred. Soda-lime glass coated with a barrier coating such as SiO2 is also commercially available and can be used.

[0051] (anode) The material used for the anode is preferably capable of efficiently injecting holes into the light-emitting layer. Furthermore, it is preferable that it be transparent or semi-transparent in order to extract light. Examples of materials for the anode include conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver, and chromium; inorganic conductive substances such as copper iodide and copper sulfide; and conductive polymers such as polythiophene, polypyrrole, and polyaniline. Among these, ITO glass and Nesa glass are preferred. These electrode materials may be used individually, or multiple materials may be laminated or mixed. The resistance of the transparent electrode should be sufficient to supply enough current for the device to emit light, but from the viewpoint of the device's power consumption, low resistance is preferable. For example, an ITO substrate with a resistance of 300 Ω / □ or less will function as an element electrode, but since substrates of approximately 10 Ω / □ are now available, it is preferable to use a substrate with a low resistance of 20 Ω / □ or less. The thickness of ITO can be arbitrarily selected to match the resistance value, and is usually used in the range of 45 to 300 nm.

[0052] (cathode) The material used for the cathode is not particularly limited as long as it is a substance that can efficiently inject electrons into the light-emitting layer. Examples of materials used for the cathode include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, or alloys or multilayer structures of these metals with low-work-function metals such as lithium, sodium, potassium, calcium, and magnesium. Among these, aluminum, silver, and magnesium are preferred as the main components in terms of electrical resistance, ease of film formation, film stability, and luminescence efficiency, and aluminum is more preferred because it facilitates electron injection into the electron transport layer and electron injection layer.

[0053] (protective layer) To protect the cathode, it is preferable to laminate a protective layer (capping layer) on the cathode. The material constituting the protective layer (capping material) is not particularly limited, but examples include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium; alloys using these metals; inorganic materials such as silica, titania, and silicon nitride; and organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon polymer compounds. However, if the light-emitting element has a top-emission structure that extracts light from the cathode side, it is preferable that the capping material has light transmittance in the visible light region.

[0054] (Hole injection layer) The hole injection layer is a layer inserted between the anode and the hole transport layer. The hole injection layer can be a single layer or multiple layers stacked together. The presence of a hole injection layer between the hole transport layer and the anode is preferable because it allows for lower voltage operation, improves durability, and further enhances the carrier balance of the device, thereby improving luminous efficiency.

[0055] The material used in the hole injection layer is not particularly limited, but from the viewpoint of smoothly injecting and transporting holes from the anode to the hole transport layer, phenanthroline derivatives represented by general formula (1) containing iodine, 4,4'-bis(N-(3-methylphenyl)-N-phenylamino)biphenyl (TPD), 4,4'-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (NPD), 4,4'-bis(N,N-bis(4-biphenylyl)amino)biphenyl (TB) are recommended. Benzidine derivatives such as DB), bis(N,N'-diphenyl-4-aminophenyl)-N,N-diphenyl-4,4'-diamino-1,1'-biphenyl (TPD232), and starburst arylamine materials such as 4,4',4”-tris(3-methylphenyl(phenyl)amino)triphenylamine (m-MTDATA) and 4,4',4”-tris(1-naphthyl(phenyl)amino)triphenylamine (1-TNATA) are preferred.

[0056] These materials may be used individually or in combination of two or more materials. Alternatively, multiple materials may be laminated to form a hole injection layer. Furthermore, it is preferable that this hole injection layer be composed solely of an acceptor compound, or that the hole injection material described above be doped with an acceptor compound, as this more pronounced the aforementioned effects. An acceptor compound is a material that, when used as a single layer, forms a charge transfer complex with the adjacent hole transport layer, and when used as a dope, forms a charge transfer complex with the material constituting the hole injection layer. Using such a material improves the conductivity of the hole injection layer, contributing to a reduction in the driving voltage of the light-emitting element, and further improving luminous efficiency and durability.

[0057] Examples of acceptor compounds include metal chlorides such as iron(III) chloride, aluminum chloride, gallium chloride, indium chloride, and antimony chloride; metal oxides such as molybdenum oxide, vanadium oxide, tungsten oxide, and ruthenium oxide; charge transfer complexes such as tris(4-bromophenyl)aminium hexachloroantimonate (TBPAH); organic compounds having a nitro group, cyano group, halogen, or trifluoromethyl group in the molecule; quinone compounds; acid anhydride compounds; and fullerenes. Among these, metal oxides and cyano group-containing compounds are preferred because they are easy to handle and can be easily deposited, thus easily obtaining the effects described above. Whether the hole injection layer is composed of an acceptor compound alone or the hole injection layer is doped with an acceptor compound, the hole injection layer may be a single layer or composed of multiple layers stacked on top of each other.

[0058] (Hole transport layer) The hole transport layer is the layer that transports holes injected from the anode to the light-emitting layer. The hole transport layer can be a single layer or composed of multiple layers stacked on top of each other.

[0059] Examples of materials used in the hole transport layer include those exemplified for use in the hole injection layer. From the viewpoint of smoothly injecting and transporting holes to the light-emitting layer, triarylamine derivatives and benzidine derivatives are more preferred.

[0060] (Emitting layer) The light-emitting layer may be a single layer or multiple layers, each formed from a light-emitting material (host material, dopant material), which may be a mixture of the host material and the dopant material, the host material alone, or a mixture of two types of host materials and one type of dopant material. In other words, in the light-emitting element 1 of the embodiment of the present invention, each light-emitting layer 5 may emit light from only the host material or the dopant material, or both the host material and the dopant material may emit light. From the viewpoint of efficiently utilizing electrical energy and obtaining light emission with high color purity, it is preferable that the light-emitting layer consists of a mixture of the host material and the dopant material. Furthermore, the host material and the dopant material may each be one type or a combination of multiple types. The dopant material may be contained throughout the host material or partially contained therein. The dopant material may be laminated or dispersed. The color of the emitted light can be controlled by the dopant material. From the viewpoint of suppressing the concentration quenching phenomenon, the amount of dopant material is preferably 30% by weight or less, and more preferably 20% by weight or less, relative to the host material. The doping method can be achieved by co-deposition with the host material, or by pre-mixing with the host material and then simultaneously depositing the doping material.

[0061] Examples of luminescent materials include condensed ring derivatives such as anthracene and pyrene, which are known as luminescent materials; metal chelated oxynoide compounds such as tris(8-quinolinolate)aluminum; bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives; tetraphenylbutadiene derivatives; indene derivatives; coumarin derivatives; oxadiazole derivatives; pyrrolopyridine derivatives; perinone derivatives; cyclopentadiene derivatives; oxadiazole derivatives; thiadiazolopyridine derivatives; dibenzofuran derivatives; carbazole derivatives; indrocarbazole derivatives; and polymers such as polyphenylenevinylene derivatives, polyparaphenylene derivatives, and polythiophene derivatives.

[0062] The host material contained in the luminescent material is not limited to just one compound; multiple compounds may be mixed and used. They may also be used in a laminated configuration. The host material is not particularly limited, but may include compounds having condensed aryl rings such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluorantene, fluorene, and indene, as well as their derivatives; aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine; metal chelated oxynoide compounds such as tris(8-quinolinate)aluminum(III); and bistyrylbenzene derivatives. Examples of polymers include tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, and polymers such as polyphenylenevinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, and polythiophene derivatives. In particular, metal chelated oxynoide compounds, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, and triphenylene derivatives are preferably used as hosts when the luminescent layer performs triplet emission (phosphorescence).

[0063] Examples of dopant materials contained in luminescent materials include compounds having aryl rings such as naphthalene, anthracene, phenanthrene, pyrene, fluorantene, triphenylene, perylene, fluorene, and indene, and their derivatives (e.g., 2-(benzothiazole-2-yl)-9,10-diphenylanthracene and 5,6,11,12-tetraphenylnaphthalene), furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9'-spirobisilafluorene, benzothiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline, pyrazine, naphthyridine, quinoxaline, pyrrolopyridine, thioxanthene, and other compounds having heteroaryl rings, and their derivatives, distyrylbenzene derivatives, and 4,4'-bis(2-(4 Examples include aminostyryl derivatives such as -diphenylaminophenyl)ethenyl)biphenyl and 4,4'-bis(N-(stilben-4-yl)-N-phenylamino)stilbene, aromatic acetylene derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, coumarin derivatives such as 2,3,5,6-1H,4H-tetrahydro-9-(2'-benzothiazolyl)quinolidino[9,9a,1-gh]coumarin, azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, and triazole, their metal complexes, and aromatic amine derivatives such as N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine. Among these, dopants containing a diamine skeleton and dopants containing a fluorantene skeleton can further improve luminescence efficiency.

[0064] The light-emitting layer may also preferably contain a triplet light-emitting material. When the light-emitting layer 5 performs triplet light emission (phosphorescence), the dopant is preferably a metal complex compound containing at least one metal selected from the group consisting of iridium (Ir), ruthenium (Ru), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re). The ligand preferably has a nitrogen-containing aromatic heterocycle such as a phenylpyridine skeleton, a phenylquinoline skeleton, or a carbene skeleton. However, it is not limited to these, and an appropriate complex is selected based on the required emission color, device performance, and relationship with the host compound.

[0065] Furthermore, it is preferable that the light-emitting layer contains a thermally activated delayed fluorescence (TADF) material. Thermally activated delayed fluorescence (TADF) materials are generally also called TADF materials. The thermally activated delayed fluorescence (TADF) material may be a single material that exhibits thermally activated delayed fluorescence, or a material that exhibits thermally activated delayed fluorescence using multiple materials. If the material consists of multiple materials, it may be used as a mixture, or layers made of each material may be laminated together. Known materials can be used as the thermally activated delayed fluorescence (TADF) material. Examples include, but are not limited to, benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indrocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, and oxadiazole derivatives.

[0066] In light-emitting devices that contain TADF material in the light-emitting layer, it is preferable that the light-emitting layer also contains a fluorescent dopant. This is because the TADF material converts triplet excitons into singlet excitons, and the fluorescent dopant receives these singlet excitons, thereby achieving higher luminescence efficiency and longer durability.

[0067] (electron transport layer) In this invention, the electron transport layer is a layer that receives electrons from the cathode and transports them. The electron transport layer is desirable to have high electron injection efficiency and to efficiently transport the injected electrons. Therefore, the material constituting the electron transport layer is preferably a substance with high electron affinity, high electron mobility, excellent stability, and that does not easily generate trapping impurities during manufacturing and use. Especially when stacking thick layers, low molecular weight compounds tend to crystallize and degrade the film quality; therefore, compounds with a molecular weight of 400 or more are preferred to maintain a stable film quality. However, considering the balance between hole and electron transport, if the electron transport layer primarily plays a role in efficiently preventing holes from the anode from flowing to the cathode without recombining, then even if it is composed of a material with relatively low electron transport capability, the effect of improving luminescence efficiency will be equivalent to that of a material with high electron transport capability. Therefore, in this invention, the electron transport layer also includes a hole blocking layer that can efficiently block the movement of holes, and the hole blocking layer and electron transport layer may be composed of a single layer or multiple materials stacked together.

[0068] Examples of electron transport materials used in the electron transport layer include condensed polycyclic aromatic derivatives such as naphthalene and anthracene, styryl aromatic ring derivatives such as 4,4'-bis(diphenylethenyl)biphenyl, quinone derivatives such as anthraquinone and diphenoquinone, phosphorus oxide derivatives, quinolinol complexes such as tris(8-quinolinolate)aluminum(III), benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes, and various metal complexes such as flavonol metal complexes. It is preferable to use compounds composed of elements selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus, and having a heteroaryl ring structure containing electron-accepting nitrogen, in order to further reduce the driving voltage and obtain more efficient light emission.

[0069] The above electron transport materials may be used alone, or two or more of the above electron transport materials may be used in combination, or one or more other electron transport materials may be mixed with the above electron transport materials. Furthermore, a donor compound may be included. Here, a donor compound is a compound that improves the electron injection barrier, thereby facilitating electron injection from cathode 3 or the electron injection layer to the electron transport layer, and further improving the electrical conductivity of the electron transport layer.

[0070] Preferred donor compounds include alkali metals, inorganic salts containing alkali metals, complexes of alkali metals and organic substances, alkaline earth metals, inorganic salts containing alkaline earth metals or complexes of alkaline earth metals and organic substances, and rare earth metals. Preferred examples of alkali metals, alkaline earth metals, and rare earth metals include alkali metals such as lithium, sodium, potassium, rubidium, and cesium, which have low work functions and are highly effective in improving electron transport capacity, as well as alkaline earth metals such as magnesium, calcium, cerium, and barium, and rare earth metals such as samarium, europium, and ytterbium. Multiple of these metals may be used, and alloys made of these metals may also be used.

[0071] Furthermore, it is preferable for the metal to be in the form of an inorganic salt or a complex with an organic substance rather than as a pure metal, as this facilitates deposition in a vacuum and makes it easier to handle. Moreover, it is even more preferable for the metal to be in the form of a complex with an organic substance, as this facilitates handling in the atmosphere and makes it easier to adjust the additive concentration. Examples of inorganic salts include oxides and nitrides such as LiO and Li2O, fluorides such as LiF, NaF, and KF, and carbonates such as Li2CO3, Na2CO3, K2CO3, Rb2CO3, and Cs2CO3. As for preferred examples of alkali metals or alkaline earth metals, lithium and cesium are good examples from the viewpoint of further reducing the driving voltage. As for preferred organic substances in the complex, quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole are good examples. Among these, complexes of alkali metals and organic substances are preferred from the viewpoint of further reducing the driving voltage of the light-emitting element. Furthermore, from the viewpoint of ease of synthesis and thermal stability, complexes of lithium and organic substances are more preferable, and lithium quinolinol (Liq), which is relatively inexpensive and readily available, is particularly preferred.

[0072] It is preferable to use the aforementioned organic thin film layer as an electron transport layer. In this case, it is preferable to include alkali metals and / or rare earth metals together with the aforementioned phenanthroline derivative.

[0073] The ionization potential of the electron transport layer is not particularly limited, but is preferably 5.6 eV to 8.0 eV, and more preferably 5.6 eV to 7.0 eV.

[0074] The method for forming each of the above-mentioned layers constituting the light-emitting element is not particularly limited and can include resistance heating deposition, electron beam deposition, sputtering, molecular stacking, and coating methods, but resistance heating deposition or electron beam deposition is generally preferred from the viewpoint of element characteristics.

[0075] (electron injection layer) In the present invention, an electron injection layer may be provided between the cathode and the electron transport layer. Generally, the electron injection layer is inserted to assist in the injection of electrons from the cathode to the electron transport layer. When inserting the layer, a compound having a heteroaryl ring structure containing electron-accepting nitrogen may be used, or a layer containing the above-mentioned donor material may be used.

[0076] Furthermore, inorganic materials such as insulators and semiconductors can be used in the electron injection layer. By using these materials, short circuits in the light-emitting element can be suppressed and electron injection performance can be improved.

[0077] As such an insulator, at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides is preferred.

[0078] Specifically, preferred alkali metal chalcogenides include, for example, Li2O, Na2S, and Na2Se. Preferred alkaline earth metal chalcogenides include, for example, CaO, BaO, SrO, BeO, BaS, and CaSe. Preferred alkali metal halides include, for example, LiF, NaF, KF, LiCl, KCl, and NaCl. Preferred alkaline earth metal halides include, for example, fluorides such as CaF2, BaF2, SrF2, MgF2, and BeF2, as well as halides other than fluorides.

[0079] Furthermore, complexes of organic compounds and metals are also suitably used. When an organic compound and metal complex is used in the electron injection layer, the thickness can be easily adjusted. Preferred examples of organic compounds in organometallic complexes include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole.

[0080] It is preferable to use the aforementioned organic thin film layer as an electron transport layer. In this case, alkali metals and / or rare earth metals may be included along with the aforementioned phenanthroline derivative, which can further reduce the driving voltage and improve durability.

[0081] (Charge generation layer) The charge generation layer in the present invention generally consists of a double layer and can be used as a pn junction type charge generation layer comprising an n-type charge generation layer and a p-type charge generation layer. The pn junction type charge generation layer generates charge or separates charge into holes and electrons when a voltage is applied in the light-emitting element, and injects these holes and electrons into the light-emitting layer via a hole transport layer and an electron transport layer. Specifically, it functions as an intermediate layer charge generation layer in a light-emitting element in which multiple light-emitting layers are stacked. The n-type charge generation layer supplies electrons to the light-emitting layer located on the anode side, and the p-type charge generation layer supplies holes to the light-emitting layer located on the cathode side. Therefore, the luminous efficiency of a light-emitting element with multiple stacked light-emitting layers can be further improved, the driving voltage can be further reduced, and the durability of the element can be further improved.

[0082] The above-mentioned n-type charge generation layer consists of an n-type dopant and a host, and conventional materials can be used for these. For example, alkali metals, alkaline earth metals, or rare earth metals can be used as the n-type dopant. Furthermore, compounds having nitrogen-containing aromatic heterocyclic compounds, such as phenanthroline derivatives and oligopyridine derivatives, can be used as the host. In particular, it is preferable to use the aforementioned organic thin film layer as the n-type charge generation layer, and the phenanthroline derivative represented by general formula (1) exhibits excellent properties as a host for the n-type charge generation layer. In this case, it is preferable to include alkali metals and / or rare earth metals together with the aforementioned phenanthroline derivative.

[0083] The above-mentioned p-type charge generation layer consists of a p-type dopant and a host, and conventional materials can be used for these. For example, as the p-type dopant, tetrafluore-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl3, FeF3, SbCl5, etc. are used. A radialene derivative is preferred as the p-type dopant. An arylamine derivative is preferred as the host.

[0084] The thickness of the organic thin film layer cannot be limited as it depends on the resistance of the light-emitting material, but it is preferably 1 to 1000 nm. The thickness of the light-emitting layer is preferably 1 nm to 200 nm, and more preferably 5 nm to 100 nm.

[0085] The light-emitting element according to an embodiment of the present invention has the function of converting electrical energy into light. While DC current is primarily used as the electrical energy, pulsed current and AC current can also be used. There are no particular restrictions on the current and voltage values, but considering the power consumption and lifespan of the element, they should be selected to obtain maximum brightness with the lowest possible energy.

[0086] The light-emitting element according to an embodiment of the present invention is suitably used as a display device, such as a display that displays in a matrix and / or segment format.

[0087] The light-emitting element according to the embodiment of the present invention is also preferably used as a backlight for various devices. Backlights are mainly used to improve the visibility of display devices such as non-self-illuminating displays, and are used in liquid crystal displays, clocks, audio equipment, automobile panels, display boards, and signs. In particular, the light-emitting element of the present invention is preferably used as a backlight for liquid crystal displays, especially for PC applications where thinning is being considered, and can provide a backlight that is thinner and lighter than conventional ones.

[0088] The light-emitting element according to the embodiment of the present invention is also preferably used as various lighting devices. The light-emitting element according to the embodiment of the present invention can achieve both high luminous efficiency and high color purity, and furthermore, it can be made thinner and lighter, so a lighting device that combines low power consumption, vivid light color, and high design quality can be realized. [Examples]

[0089] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0090] Synthesis Example 1: Synthesis of 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline by batch method 9.64 g of 1,10-phenanthroline and 250 ml of toluene were placed in a 100 ml four-necked flask purged with nitrogen gas. The solution was stirred while maintaining the flask temperature at 0-5°C, and 100 ml of phenyllithium (1.6 M dibutyl ether solution) was added. The mixture was stirred for a further 1.5 hours to allow the reaction to proceed. Next, the reaction solution was stirred while maintaining the flask temperature at 0-5°C, and 150 ml of H2O was added to quench the reaction. Then, 200 ml of dichloromethane was added to the quench solution to extract the reaction product. To this extract, 200 ml of dichloromethane solution containing 93 g of manganese dioxide dispersed was added while maintaining the flask temperature below 30°C, and the mixture was stirred at room temperature for 1 hour to allow oxidation. Next, the obtained oxide solution was filtered using a Kiriyama funnel (filter paper mesh: 4 μm), and the filtrate was concentrated to dryness using an evaporator at a bath temperature of 40°C to obtain 9.44 g of 2-phenyl-1,10-phenanthroline.

[0091] 0.24 ml of 1,3-dibromobenzene and 6.9 ml of n-hexane were placed in a 200 ml four-necked flask purged with nitrogen gas and stirred at room temperature. While stirring this solution, 3.3 ml of n-butyllithium (1.52 M hexane solution) was added and stirred further. This mixture was heated to an ambient temperature of 70°C using an oil bath, stirred under reflux for 1 hour, and then cooled to 0-5°C in an ice bath. Separately, 1.02 g of 2-phenyl-1,10-phenanthroline and 20 ml of THF were placed in a 100 ml four-necked flask purged with nitrogen gas and stirred, and the resulting solution was cooled to 0-5°C in an ice bath. This solution was added dropwise to the 1,3-dilithiobenzene solution while maintaining the flask temperature at 0-5°C, stirred for 2 hours, and then 20 ml of water was added while maintaining the flask temperature at 0-5°C to quench the reaction. Next, 50 ml of dichloromethane was added to the quenched solution to extract the reaction products. To the extract solution, 50 ml of dichloromethane solution containing 7.0 g of manganese dioxide was added while maintaining the flask temperature below 30°C, and the mixture was stirred for 15 minutes to oxidize it. The resulting oxide solution was then filtered using a Kiriyama funnel (filter paper mesh: 4 μm), and the filtrate was concentrated to dryness using an evaporator at a bath temperature of 40°C to obtain 0.65 g of crude product of 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline, a phenanthroline derivative represented by the general formula (1).

[0092] The obtained crude product was heated and washed with toluene slurry, then recrystallized with anisole / toluene solution, and heated and washed with tetrahydrofuran / methanol solution slurry. The resulting crystals were extracted using an oil diffusion pump, yielding 1.0 × 10⁻⁶ crystals. -3 Under a pressure of Pa or less, the substance was purified by sublimation at 320°C to obtain 3.8 g of 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline, which is a phenanthroline derivative represented by the general formula (1).

[0093] Synthesis Example 2: Synthesis of iodine-containing 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline by batch method 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline, obtained in the same manner as in Synthesis Example 1, was appropriately mixed with a 0.2 M iodine solution dissolved in ethanol to prepare solutions with iodine content of 1 ppm, 60 ppm, 10,000 ppm, and 100,000 ppm.

[0094] Synthesis Example 3: Synthesis of iodine-containing 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline by flow method 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline was synthesized by the following flow reaction (steps 1A) to (steps 5A). Syringe pump: YMC Corporation, Model YSP-301, High-performance high-pressure type Temperature: 10~30℃ Flow channel diameter (inner diameter) between mixers: 1 mm Material of the flow path between mixers: "Teflon" (registered trademark) Mixer shape: T-shape Mixer material: "Teflon" (registered trademark) Mixer channel diameter: 1mm.

[0095] (Process 1A) A 0.2 M 1,3-dibromobenzene / tetrahydrofuran solution was flowed from server A at a flow rate of 5.0 ml / min, and a 0.2 M n-butyllithium / n-hexane solution was flowed from server B at a flow rate of 4.6 ml / min, and the reaction was carried out in the first T-shaped mixer section. The reaction flow rate was 9.6 ml / min.

[0096] (Process 2A) Two seconds after the first T-mixer section, a 0.2 M 2-phenyl-1,10-phenanthroline / tetrahydrofuran solution was introduced from server C into the flow path at a flow rate of 4.2 ml / min and reacted in the second T-mixer section. The reaction flow rate was 13.8 ml / min.

[0097] (Process 3A) Four seconds after the second T-shaped mixer section, a 0.2 M n-butyllithium / n-hexane solution was flowed from server D into the channel at a flow rate of 4.6 ml / min and reacted in the third T-shaped mixer section. The reaction flow rate was 18.4 ml / min.

[0098] (Process 4A) Two seconds after entering the third T-shaped mixer section, a 0.2 M 2-phenyl-1,10-phenanthroline / tetrahydrofuran solution was introduced from server E into the flow path at a flow rate of 4.2 ml / min and reacted in the fourth T-shaped mixer section. The reaction flow rate was 22.6 ml / min.

[0099] (Step 5A) Two seconds after the fourth T-shaped mixer section, a 0.2 M iodine / tetrahydrofuran solution was introduced from server F into the flow path at a flow rate of 4.2 ml / min and reacted in the fifth T-shaped mixer section. The reaction flow rate was 26.8 ml / min. Ten seconds after the fifth T-shaped mixer section, the reaction product was collected in a flask. However, the sample was collected one minute after the pump started operating.

[0100] Next, the suspension solution of the reaction product was filtered using a Kiriyama funnel (filter paper mesh: 4 μm), and the filtrate was dried at 80°C to obtain 5.1 g of the crude product of 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline.

[0101] Next, (Step 6A) was carried out using the following method (batch method).

[0102] (Process 6A) The crude product of 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline obtained in (Step 5A) was heated and slurry-washed with toluene, then recrystallized with anisole / toluene solution, and heated and slurry-washed with tetrahydrofuran / methanol solution. The crystals were purified by sublimation at 320°C under a pressure of 1.0 × 10⁻³ Pa or less using an oil diffusion pump to obtain 3.9 g of 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline. The iodine content was measured to be 850 ppm by the method described later.

[0103] The structure of 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline obtained by synthesis examples 1 to 3 is shown below.

[0104] [ka]

[0105] Next, the evaluation methods for each embodiment will be described.

[0106] (Iodine content) The phenanthroline derivative obtained in Synthesis Example 3 was compressed and molded using a press, and the surface was covered with a polypropylene film to suppress volatilization from the surface, and used as a measurement sample. The obtained measurement sample was irradiated with primary X-rays using an X-ray fluorescence analyzer, and the intensity of iodine fluorescence X-rays that appeared when returning from the excited state to the ground state was measured. The iodine content was calculated from a calibration curve prepared in advance using samples with known iodine content.

[0107] The following evaluations were conducted through accelerated testing, applying DC drive currents and voltages significantly more severe than actual operating conditions, in order to obtain results quickly.

[0108] (Drive voltage) The elements obtained in Examples 1-13 and Comparative Examples 1-2 were each given a flow rate of 10 mA / cm². 2 The device was driven by DC power, and the initial drive voltage was measured.

[0109] Furthermore, the light-emitting elements obtained in Examples 14-26 and Comparative Examples 3-4 were each given a brightness of 1000 cd / m². 2 The lights were turned on, and the initial drive voltage was measured.

[0110] Furthermore, the light-emitting elements obtained in Examples 27-39 and Comparative Examples 5-6 were each set to 10 mA / cm². 2 The system was driven at the specified current density, and the initial drive voltage was measured.

[0111] (durability) (1) The elements obtained in Examples 1 to 13 and Comparative Examples 1 to 2 were subjected to a current density of 10 mA / cm² in an environment with a temperature of 70°C. 2 The voltage was measured after 100 hours of DC operation, and the voltage rise from the initial operating voltage was calculated. A smaller voltage rise indicates better durability.

[0112] Furthermore, the light-emitting elements obtained in Examples 14-26 and Comparative Examples 3-4 were subjected to a current density of 10 mA / cm² in an environment of 70°C. 2 The voltage was measured after 100 hours of constant current operation, and the voltage rise from the initial operating voltage was calculated. A smaller voltage rise indicates better durability.

[0113] (2) The light-emitting elements obtained in Examples 14-39 and Comparative Examples 4-6 were subjected to a 10 mA / cm² 2 The device was lit and the initial brightness was measured. Furthermore, 10mA / cm² was measured. 2 The device was continuously driven with a constant current, and the time it took for the brightness to decrease by 20% from the initial brightness (hereinafter sometimes abbreviated as "brightness decrease time") was measured.

[0114] Example 1 A glass substrate (manufactured by Geomatec Co., Ltd., 10Ω / □, sputtered) with a 100nm transparent ITO conductive film deposited as the anode was cut to 75mm x 75mm and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" (registered trademark) 56 (product name, manufactured by Furuuchi Chemical Co., Ltd.), and then washed with ultrapure water. Immediately before fabricating the device, this substrate was UV-ozone treated for 1 hour, placed in a vacuum deposition apparatus, and evacuated until the vacuum level inside the apparatus was 5 × 10⁻⁴ Pa or less. First, using the resistance heating method, a mixed layer of host material TR-host A, represented by the following structural formula, and dopant material TR-dopant B, represented by the following structural formula, was deposited to a thickness of 20nm with a dope concentration of 3% by weight as the light-emitting layer. Next, 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline (hereinafter sometimes abbreviated as "compound 1") obtained in Synthesis Example 3 and the dopant metal element Li were deposited to a thickness of 100 nm such that the deposition rate ratio of compound 1:Li = 99:1, forming a layer with a weight ratio of 99:1. Then, aluminum was deposited to a thickness of 100 nm as the cathode to fabricate a 25 mm × 25 mm square light-emitting element. The thickness referred to here is the value displayed on a quartz oscillator thickness monitor and is common to other examples and comparative examples as well.

[0115] [ka]

[0116] When this light-emitting element was evaluated using the method described above, the initial drive voltage was 0.029V, and the voltage rise after 100 hours of operation at 70°C was 0.001V.

[0117] Examples 2-7, Comparative Example 1 As Compound 1, a compound 1 with an iodine content described in Table 1 was used, and a light-emitting device was fabricated in the same manner as in Example 1, except that the deposition rate ratio of Compound 1 to the metal element Li was as shown in Table 1. Here, as Compound 1, in Examples 2 to 7, the compound 1 obtained by Synthesis Example 2 was used, and in Comparative Example 1, the compound 1 obtained by Synthesis Example 1 was used.

[0118] Examples 8 to 13, Comparative Example 2 Instead of Compound 1, a compound 2 represented by the following structural formula with an iodine content described in Table 1 was used, and a light-emitting device was fabricated in the same manner as in Example 1, except that the deposition rate ratio of Compound 2 to the metal element Li was as shown in Table 1.

[0119] [Chemical formula]

[0120] [Table 1]

[0121] Example 14 A glass substrate (manufactured by Geomatec Co., Ltd., 10 Ω / □, sputtered product) on which a 100 nm ITO transparent conductive film was deposited as an anode was cut into 75 mm × 75 mm and etched. The obtained substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" (registered trademark) 56 (product name, manufactured by Furuchi Chemical Co., Ltd.), and then washed with ultrapure water. This substrate was subjected to UV-ozone treatment for 1 hour immediately before fabricating the device, placed in a vacuum evaporation apparatus, and the degree of vacuum in the apparatus was 5 × 10 -4The atmosphere was evacuated until the pressure dropped below Pa. Using the resistance heating method, first, TR-HIL was deposited at a thickness of 5 nm as a hole injection layer, followed by the deposition of TR-HTL-A at 105 nm and TR-HTL-B at 10 nm as hole transport layers. Next, a mixed layer of host material TR-host A and dopant material TR-dopant B was deposited to a thickness of 20 nm as an emissive layer, with a dope concentration of 3 wt%. Next, TR-ETL-A was deposited to a thickness of 20 nm. Next, as an electron injection layer, compound 1 obtained in synthesis example 3 and the dopant metal element Li were deposited at a thickness of 10 nm, with a deposition rate ratio of compound 1:Li = 99:1. After that, aluminum was deposited at a thickness of 100 nm to form the cathode, and a 25 mm × 25 mm square light-emitting device was fabricated. The structures of TR-HIL, TR-HTL-A, TR-HTL-B, and TR-ETL-A are shown below.

[0122] [ka]

[0123] When this light-emitting element was evaluated using the method described above, the initial drive voltage was 4.01V, the brightness reduction time was 1040 hours, and the voltage increase was 0.003V.

[0124] Examples 15-20, Comparative Example 3 A light-emitting element was fabricated in the same manner as in Example 14, except that Compound 1 with the iodine content listed in Table 2 was used as Compound 1, and the deposition rate ratio of Compound 1 to the metal element Li was as shown in Table 2. Here, as Compound 1, Examples 15 to 20 used Compound 1 obtained in Synthesis Example 2, and Comparative Example 3 used Compound 1 obtained in Synthesis Example 1.

[0125] Examples 21-26, Comparative Example 4 A light-emitting element was fabricated in the same manner as in Example 14, except that compound 2, with the iodine content listed in Table 2, was used instead of compound 1, and the deposition rate ratio of compound 2 to the metal element Li was as shown in Table 2.

[0126] The results for each example and comparative example are shown in Table 2.

[0127] [Table 2]

[0128] Example 27 A glass substrate (manufactured by Geomatec Co., Ltd., 11Ω / □, sputtered) with a 165nm ITO transparent conductive film deposited as the anode was cut to 75mm x 75mm and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" (registered trademark) 56 (product name, manufactured by Furuuchi Chemical Co., Ltd.), and then washed with ultrapure water. Immediately before fabricating the device, this substrate was UV-ozone treated for 1 hour and placed in a vacuum deposition apparatus, where the vacuum level inside the apparatus was 5 x 10⁻⁶. -4 The system was evacuated until the pressure dropped below Pa. First, a 10 nm layer of TR-HIL was deposited as a hole injection layer using the resistance heating method. Next, a light-emitting unit (first light-emitting unit) consisting of a hole transport layer, a light-emitting layer, and an electron transport layer was formed on the hole injection layer.

[0129] Specifically, TR-HTL-A was deposited at a thickness of 105 nm and TR-HTL-B at a thickness of 10 nm as a hole transport layer. Next, a mixed layer of the host material TR-host A and the aforementioned dopant material TR-dopant B was deposited to a thickness of 20 nm with a doping concentration of 3 wt% as an emissive layer. Next, TR-ETL-A was deposited to a thickness of 20 nm as an electron transport layer.

[0130] On the first light-emitting unit, compound 1 obtained in synthesis example 3 and the dopant metal element Li were deposited at a rate ratio of compound 1:Li = 99:1 at a rate of 12 nm, and then TR-HIL was deposited at a rate of 10 nm as a P-type charge generation layer.

[0131] Following the charge generation layer, a second light-emitting unit was formed in the same manner as the first light-emitting unit. Subsequently, as an electron injection layer, compound 1 obtained in synthesis example 3 and the dopant metal element Li were deposited at a deposition rate ratio of compound 1:Li = 99:1 at a deposition rate of 10 nm, followed by the deposition of aluminum at a deposition rate of 100 nm to form the cathode, thereby fabricating a light-emitting device measuring 25 mm × 25 mm square.

[0132] When this light-emitting element was evaluated using the method described above, the initial drive voltage was 8.12V and the brightness degradation time was 2670 hours.

[0133] Examples 28-33, Comparative Example 5 A light-emitting element was fabricated in the same manner as in Example 27, except that Compound 1 with the iodine content listed in Table 3 was used as Compound 1, and the deposition rate ratio of Compound 1 to the metal element Li was as shown in Table 3. Here, as Compound 1, Examples 28 to 33 used Compound 1 obtained in Synthesis Example 2, and Comparative Example 5 used Compound 1 obtained in Synthesis Example 1.

[0134] Examples 34-39, Comparative Example 6 A light-emitting element was fabricated in the same manner as in Example 27, except that compound 2, with the iodine content listed in Table 3, was used instead of compound 1, and the deposition rate ratio of compound 2 to the metal element Li was as shown in Table 3.

[0135] The results for each example and comparative example are shown in Table 3.

[0136] [Table 3] [Explanation of Symbols]

[0137] 1 Light-emitting element 2 Anode 3 cathode 5. Emitting layer 6 Organic thin film layer

Claims

1. A light-emitting element that emits light by electrical energy, wherein at least an organic thin film layer and a light-emitting layer are present between an anode and a cathode, and the organic thin film layer comprises an n-type charge generation layer, an electron transport layer and / or an electron injection layer, and the n-type charge generation layer, electron transport layer and / or electron injection layer contains a phenanthroline derivative represented by the following general formula (1) containing iodine, and the iodine content in the phenanthroline derivative represented by the general formula (1) is 60 ppm or more and 100,000 ppm or less. 【Chemistry 1】 (In the above general formula (1), R2 to R7 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryloxy group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkylthio group, an arylthio group, or a cyano group. R1 and R8 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group. However, at least one of R1 and R8 is a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group.)

2. The light-emitting element according to claim 1, comprising 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline and / or 2-[4-(9-phenantrenyl)-1-naphthalenyl]-1,10-phenanthroline as the phenanthroline derivative represented by the general formula (1).

3. The light-emitting element according to claim 1 or claim 2, wherein the iodine content in the phenanthroline derivative represented by the general formula (1) is 60 ppm or more and 10,000 ppm or less.

4. The light-emitting element according to any one of claims 1 to 3, wherein the organic thin film layer contains alkali metal atoms and / or rare earth metal atoms.

5. A display device including a light-emitting element according to any one of claims 1 to 4.

6. A lighting device including a light-emitting element according to any one of claims 1 to 4.

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