Material for organic el element, organic el element, display device, and lighting device

Abstract

This invention provides a material for organic EL elements, an organic EL element, a display device, and a lighting device. The material for an organic EL element is represented by the following general formula (1). In general formula (1), X... 1 ~X 3 One of them is a nitrogen atom, and the others are methines. L 1 For substituted or unsubstituted phenylene, substituted or unsubstituted naphthylene, or substituted or unsubstituted anthracene, L 2 The group is a single bond, a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, or a substituted or unsubstituted anthracene group. When these groups are substituted, the substituents are alkyl or alkoxy groups. A is a phenyl or pyridinyl group, and n is 0 or 1. This provides an organic EL element with excellent luminous efficiency and longevity.

Description

Technical Field

[0001] This invention relates to a material for an organic electroluminescence (EL) element having a specific structure, an organic EL element using the compound, a display device, and a lighting device. Background Technology

[0002] In recent years, organic EL devices have been steadily being put into practical use in displays for televisions and smartphones. However, there are still many technical challenges in existing organic EL devices. Among them, achieving both high-efficiency light emission and long lifespan of organic EL devices has become a major challenge.

[0003] As compounds for solving these problems, phenanthroline derivatives having a terpyridine skeleton and specific aryl substitutions have been developed to date (e.g., see Patent Document 1), phenanthroline derivatives having a pyrene skeleton (e.g., see Patent Document 2), phenanthroline derivatives having a dibenzofuran skeleton (e.g., see Patent Documents 3-4), and phenanthroline derivatives having specific arylene and heteroaryl groups (e.g., see Patent Document 5), etc.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2016 / 121597

[0007] Patent Document 2: Korean Patent Application Publication No. 10-2020-0064423

[0008] Patent Document 3: Japanese Patent Publication No. 2020-506892

[0009] Patent Document 4: International Publication No. 2020 / 218648

[0010] Patent Document 5: European Patent Application Publication No. 2983227 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] According to Patent Documents 1 to 5, phenanthroline derivatives formed by linking terpyridine, pyrene, dibenzofuran, or specific aryl, arylene, or heteroaryl groups can be used to obtain organic EL devices with improved luminous efficiency, low-voltage drive capability, and excellent durability. However, in recent years, the required luminous efficiency and durability of organic EL devices have been increasing, thus demanding technologies that can achieve both high luminous efficiency and long lifespan.

[0013] In view of the problems of the prior art, the present invention aims to provide an organic EL element with excellent luminous efficiency and longevity.

[0014] Technical means to solve the problem

[0015] The present invention relates to a material for organic EL elements represented by the following general formula (1).

[0016] [Chemistry 1]

[0017]

[0018] In general formula (1), X 1 ~X 3 One of them is a nitrogen atom, and the others are methines. L 1 For substituted or unsubstituted phenylene, substituted or unsubstituted naphthylene, or substituted or unsubstituted anthracene, L 2 It is a single bond, a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, or a substituted or unsubstituted anthracene group. Wherein, the substituent when these groups are substituted is an alkyl or alkoxy group. A is a phenyl or pyridinyl group, and n is 0 or 1.

[0019] The effects of the invention

[0020] This invention provides an organic EL element with excellent luminous efficiency and long lifespan. Detailed Implementation

[0021] The preferred embodiments of the organic EL element material, the organic EL element, the display device, and the lighting device of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments and can be implemented with various modifications depending on the purpose or application.

[0022] (Materials for organic EL elements represented by general formula (1))

[0023] The organic EL element material represented by general formula (1), as an embodiment of the present invention, comprises the phenanthroline derivative shown below, indicating the material used in any layer constituting the organic EL element. That is, the so-called organic EL element material refers to the use of the phenanthroline derivative represented by the following general formula (1).

[0024] [Chemistry 2]

[0025]

[0026] In general formula (1), X 1 ~X 3 One of them is a nitrogen atom, and the others are methines. L 1For substituted or unsubstituted phenylene, substituted or unsubstituted naphthylene, or substituted or unsubstituted anthracene, L 2 It is a single bond, a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, or a substituted or unsubstituted anthracene group. Wherein, the substituent when these groups are substituted is an alkyl or alkoxy group. A is a phenyl or pyridinyl group, and n is 0 or 1.

[0027] In the case of "substituted or unsubstituted," "unsubstituted" means that a hydrogen atom is bonded, and "substituted" means that at least a portion of the hydrogen atoms are substituted. The hydrogen atom may also be a deuterium atom. The same applies to the "substituted or unsubstituted" cases in the compounds or partial structures described below.

[0028] The term alkyl refers to, for example, saturated aliphatic hydrocarbon groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl, which may or may not have substituents. There is no particular limitation on the number of carbon atoms in the alkyl group, but in terms of ease of acquisition or cost, it is generally in the range of 1 to 20, more preferably 1 to 8.

[0029] The term alkoxy refers to a group formed by the bonding of an alkyl group with an oxygen atom, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, or tert-butoxy. It may or may not have substituents. There is no particular limitation on the number of carbon atoms in the alkoxy group, but in terms of ease of acquisition or cost, it is generally in the range of 1 to 20, more preferably 1 to 8.

[0030] Existing compounds containing nitrogen-containing aromatic heterocycles and polycyclic aromatic hydrocarbons include, for example, compounds V, W, X, Y, and Z represented by the following formulas, as shown in Patent Documents 1 to 5.

[0031] [Chemistry 3]

[0032]

[0033] However, even when these compounds are used as materials for organic EL elements in electron injection layers, electron transport layers, or charge generation layers, they have not yet achieved sufficient performance to meet the characteristics required in recent years. There is a need to create compounds that can further improve performance in terms of luminous efficiency and durability.

[0034] For example, compounds like compound V, which are formed by substituting a pyrene group onto a phenanthroline group, have large substituents near the nitrogen atom on the highly coordinating phenanthroline group. This tends to reduce the coordination of the phenanthroline group with the metal atom. Therefore, using compound V simultaneously with a metal atom presents challenges such as reduced film stability, increased driving voltage, and decreased luminous efficiency and lifetime. Compounds like compounds W or Y, which have large aromatic substituents on the linking group of the terpyridinyl and phenanthroline groups, have a smaller effect on enhancing molecular interactions due to their large size, resulting in high driving voltage and challenges in luminous efficiency and lifetime. Compounds like compound X, formed by linking a terpyridinyl and phenanthroline group via a dibenzofuranyl group, have excessively high crystallinity due to the high planarity of the phenanthroline group and the linking group, resulting in high driving voltage and challenges in luminous efficiency and lifetime. Compounds like compound Z, which are formed by linking three arylene groups with terpyridyl and phenanthrolinyl groups, also exhibit excessive crystallinity due to their high planarity, resulting in higher driving voltage and issues with luminous efficiency and durability.

[0035] In their research on the improvement of materials for organic EL devices, the inventors focused on the effects of phenanthroline, terpyridinyl, and their linking groups. Both phenanthroline and terpyridinyl groups have high electron transport properties and are substituents with high coordination to metal atoms.

[0036] The organic EL element material represented by general formula (1) is selected by choosing phenylene, naphthylene, or anthraceneylene as the L 1 Choose a single bond, phenylene, naphthylene, or anthraceneylene as the L-type. 2 This allows for easy conjugation of phenanthrolinyl, terpyridyl, and their linker groups, further increasing the charge transport properties of the compound as a whole. Therefore, the driving voltage can be reduced when used in organic EL elements, improving luminous efficiency. Furthermore, it enhances coordination with metal atoms, thus forming a stable layer when the material for organic EL elements represented by the general formula (1) is used in the metal-doped layer of an organic EL element. Here, a metal-doped layer refers to a layer in which a metal is doped in any layer constituting an organic EL element. In particular, when the material for organic EL elements represented by the general formula (1) is used in electron transport layers, electron injection layers, or charge generation layers, these layers exhibit more stable and superior performance.

[0037] In general formula (1), L 1 For substituted or unsubstituted phenylene, substituted or unsubstituted naphthylene, or substituted or unsubstituted anthracene, L 2 It is a single bond, a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, or a substituted or unsubstituted anthracene group. L 1The substituents used in the substitution process are alkyl or alkoxy groups. These substituents can improve the stability of the compound without reducing its charge transport properties, and are therefore preferred. From the viewpoint of improving film stability, further improving luminous efficiency, and durability, L... 1 or L 2 Preferably, it is naphthylene. Additionally, in L... 2 In the case of a single bond, the interaction between the phenanthrolin group and the terpyridine group can be further increased, which can further improve the luminescence efficiency and durability.

[0038] In general formula (1), X 1 ~X 3 One of them is a nitrogen atom, and the others are methine atoms. From the viewpoint of improving the coordination of the metal atom and forming a more stable layer, X 3 Nitrogen atoms are preferred. By forming a more stable layer, it can be driven at low voltage, further improving durability and lifespan.

[0039] In general formula (1), when n is 1, A is phenyl or pyridyl. When n is 1, the highly reactive positions 2 and 9 of the phenanthroline are substituted, thus improving the stability of the compound. Furthermore, by selecting phenyl or pyridyl as A, the high coordination of the nitrogen atom on the phenanthroline group allows for the formation of a layer with higher metal coordination and greater stability when used in a metal-doped layer. Therefore, the driving voltage can be further reduced, and the lifespan can be improved. From the viewpoint of further improving the stability or lifespan of the device, phenyl is preferred as A.

[0040] In general formula (1), when n is 0, the 9-position of phenanthroline is hydrogen. When n is 0, phenanthroline is sterically empty, so when used in metal-doped layers, it can form layers with higher metal coordination and greater stability.

[0041] From the viewpoint of suppressing crystallization and improving the stability of the film, the molecular weight of the organic EL element material represented by general formula (1) is preferably 400 or more. On the other hand, from the viewpoint of improving processability during sublimation purification or vapor deposition, the molecular weight of the organic EL element material represented by general formula (1) is preferably 640 or less.

[0042] As materials for organic EL elements represented by the general formula (1), examples include compounds containing the compounds shown below. Furthermore, as an example, even compounds other than those explicitly described herein, as long as they are compounds represented by the general formula (1), can be used with equal preference.

[0043] [Chemistry 4]

[0044]

[0045] [Chemistry 5]

[0046]

[0047] [Chemistry 6]

[0048]

[0049] [Chemistry 7]

[0050]

[0051] [Chemistry 8]

[0052]

[0053] [Chemistry 9]

[0054]

[0055] [Chemistry 10]

[0056]

[0057] [Chemistry 11]

[0058]

[0059] [Chemistry 12]

[0060]

[0061] [Chemistry 13]

[0062]

[0063] [Chemistry 14]

[0064]

[0065] [Chemistry 15]

[0066]

[0067] [Chemistry 16]

[0068]

[0069] [Chemistry 17]

[0070]

[0071] [Chemistry 18]

[0072]

[0073] [Chemistry 19]

[0074]

[0075] [Chemistry 20]

[0076]

[0077] The organic EL element material represented by general formula (1) can be synthesized by known synthetic methods. Examples of synthetic methods include, for instance, the coupling reaction of palladium halide aryl derivatives with arylboronic acid derivatives, but are not limited to this.

[0078] The term "material for organic EL devices" refers to a material used in any layer of an organic EL device. Examples of layers for which the material of general formula (1) can be used include, as described later, hole injection layers, hole transport layers, light-emitting layers, electron transport layers, and protective films (capping layers) for electrodes. By using the material of general formula (1) in any layer of an organic EL device, an organic EL device with excellent luminous efficiency and longevity can be provided.

[0079] (Organic EL element)

[0080] Secondly, the implementation of the organic EL element is described in detail. The organic EL element has an anode and a cathode, and an organic layer between the anode and the cathode, the organic layer emitting light through electrical energy.

[0081] In addition to structures containing only a light-emitting layer, the layered structures between the anode and cathode in this type of organic EL element can include: 1) light-emitting layer / electron transport layer, 2) hole transport layer / light-emitting layer, 3) hole transport layer / light-emitting layer / electron transport layer, 4) hole injection layer / hole transport layer / light-emitting layer / electron transport layer, 5) hole transport layer / light-emitting layer / electron transport layer / electron injection layer, 6) hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer, 7) hole injection layer / hole transport layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer, etc.

[0082] Furthermore, it can also be a tandem type where multiple of the aforementioned stacked structures are stacked via an intermediate layer. The intermediate layer is generally also referred to as an intermediate electrode, intermediate conductive layer, charge generation layer, electron absorption layer, connecting layer, or intermediate insulating layer, and can use known material structures. Specific examples of the tandem type include: 8) hole transport layer / light emission layer / electron transport layer / charge generation layer / hole transport layer / light emission layer / electron transport layer, 9) hole injection layer / hole transport layer / light emission layer / electron transport layer / electron injection layer / charge generation layer / hole injection layer / hole transport layer / light emission layer / electron transport layer / electron injection layer, etc., in which a charge generation layer is included as an intermediate layer between the anode and the cathode.

[0083] Furthermore, each of the layers can be a single layer or multiple layers, and can also be doped. In particular, if the electron injection layer and charge generation layer are metal-doped layers, the electron transport capability or the electron injection capability to adjacent layers can be improved, which is therefore preferred. In addition, if a protective layer (capping layer) is provided in addition to the layers, the luminous efficiency can be further improved through optical interference effects, which is also preferred.

[0084] The organic EL element material represented by general formula (1) can be used in any of the layers of the organic EL element, and is particularly preferably used in the electron transport layer, charge generation layer, or electron injection layer. The preferred structures for the organic EL element of the present invention are: a structure having at least an electron transport layer and a light-emitting layer between the anode and cathode, and containing the organic EL element material represented by general formula (1) in the electron transport layer; a structure having at least a charge generation layer and a light-emitting layer between the anode and cathode, and containing the organic EL element material represented by general formula (1) in the charge generation layer; or a structure having at least an electron injection layer and a light-emitting layer between the anode and cathode, and containing the organic EL element material represented by general formula (1) in the electron injection layer. These layers may also contain the organic EL element material represented by general formula (1) in two or more layers.

[0085] In the organic EL element of the embodiment of the present invention, the anode and cathode serve to supply current sufficient to make the element emit light, and ideally, at least one of them is transparent or translucent in order to output light. Typically, the anode formed on the substrate is set as a transparent electrode.

[0086] (Substrate)

[0087] To maintain the mechanical strength of the organic EL element, it is preferable to form the organic EL element on a substrate. Examples of substrates include glass substrates such as soda-lime glass or alkali-free glass, or plastic substrates. When using a glass substrate, the thickness only needs to be sufficient to maintain mechanical strength; 0.5 mm or more is sufficient. Regarding the glass material, it is preferable to have low ion leaching, and alkali-free glass is preferred. Additionally, commercially available soda-lime glass with a barrier coating such as SiO2 can also be used.

[0088] (anode)

[0089] An anode is formed on a substrate. The material used in the anode is preferably one that can efficiently inject holes into the organic layer. Furthermore, for light output, it is preferably transparent or translucent. Examples of materials used in 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 materials such as copper iodide and copper sulfide; and conductive polymers such as polythiophene, polypyrrole, and polyaniline. Among these, ITO glass or NESA glass is preferred. These electrode materials can be used individually or in combination. The resistance of the substrate on which the anode is formed is only required to supply a current sufficient to make the element emit light; from the viewpoint of the element's power consumption, low resistance is preferred. For example, if the ITO substrate has a resistance of 300Ω / Y or less, it functions as a component electrode. However, substrates with a resistance of around 10Ω / Y are also available now, so it is preferable to use a low-resistance substrate with a resistance of 20Ω / Y or less. The thickness of the anode can be arbitrarily selected according to the resistance value, but it is usually used in the range of 45nm to 300nm.

[0090] (hole injection layer)

[0091] 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. If a hole injection layer exists between the hole transport layer and the anode, it can be driven at a lower voltage, resulting in improved lifespan. Furthermore, it improves the carrier balance of the device and the luminous efficiency, making it a preferred option.

[0092] There are no particular limitations on the materials used for hole injection layers. Examples include: 4,4'-bis(N-(3-methylphenyl)-N-phenylamino)biphenyl (N,N,N',N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, TPD), 4,4'-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, NPD), and 4,4'-bis(N,N-bis(4-biphenyl)amino)biphenyl (tetrabiphenylyl) diaminobiphenyl (TBDB), bis(N,N'-diphenyl-4-aminophenyl)-N,N-diphenyl-4,4'-diamino-1,1'-biphenyl (TPD232) and other benzidine derivatives; 4,4',4"-tris(3-methylphenyl(phenyl)amino)triphenylamine (m-MTDATA), 4,4',4"-tris(1-naphthyl(phenyl)amino)triphenylamine (m-MTDATA) Materials belonging to the group known as starburst arylamines, such as phenyl(amino)triphenylamine (1-TNATA); triarylamine derivatives; bis(N-arylcarbazole), bis(N-alkylcarbazole), and other biscarbazole derivatives; pyrazoline derivatives; stilbene compounds; hydrazone compounds; heterocyclic compounds such as benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; polycarbonate or styrene derivatives having the aforementioned monomers in the side chain; and polymeric materials such as polythiophene, polyaniline, polyfluorene, polyvinylcarbazole, and polysilane. From the viewpoint of smoothly injecting transport holes from the anode to the hole transport layer, benzidine derivatives or starburst arylamine materials are more preferably used.

[0093] These materials can be used alone or in combination of two or more materials. Alternatively, multiple materials can be stacked to form a hole injection layer. Furthermore, if the hole injection layer is composed solely of an acceptor compound, or if an acceptor compound is doped into the hole injection material described above, the aforementioned effect can be obtained more significantly, and is therefore preferred. The acceptor compound, when used as a monolayer, refers to the material that forms the contacted hole transport layer and charge migration complex; when used as a dopant, it refers to the material constituting the hole injection layer and the material forming the charge migration complex. Using such a material improves the conductivity of the hole injection layer, further reducing the device's driving voltage and improving luminous efficiency or lifetime.

[0094] Examples of acceptor compounds include: metal chlorides such as ferric(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 ammonium tris(4-bromophenyl)hexachloroantimonate (TBPAH); organic compounds containing nitro, cyano, halogen, or trifluoromethyl groups; quinone compounds; acid anhydride compounds; and fullerenes. Among these, metal oxides or cyano-containing compounds are preferred because they are easy to handle and readily vapor-deposit, thus readily achieving the aforementioned effects. In either the case where the hole injection layer is composed solely of an acceptor compound, or where an acceptor compound is doped into the hole injection layer, the hole injection layer may be a single layer or composed of multiple layers stacked together.

[0095] (Hole transport layer)

[0096] 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 together.

[0097] Materials used in the hole transport layer can be exemplified as materials used in the hole injection layer. From the viewpoint of smoothly injecting transported holes into the light-emitting layer, triarylamine derivatives or benzidine derivatives are more preferred.

[0098] (Emitting layer)

[0099] The light-emitting layer can be a single layer or multiple layers. The light-emitting layer is formed of a light-emitting material, which can be a mixture of a host material and a dopant material, a single host material, or a mixture of two host materials and one dopant material; any of these are acceptable. That is, regarding the organic EL element in the embodiments of the present invention, in each light-emitting layer, only the host material or the dopant material may emit light, 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, the light-emitting layer is preferably a mixture containing both the host material and the dopant material. Furthermore, the host material and the dopant material can be one type or a combination of multiple types; any of these are acceptable. When the light-emitting layer contains a mixture of the host material and the dopant material, the dopant material can be contained in the entire host material or in a portion of the host material; any of these are acceptable. The dopant material can be layered or dispersed; any of these are acceptable. The dopant material can control the emission color. From the perspective of suppressing concentration quenching, the total amount of the host material and the dopant material is set to 100% by weight, and the amount of the dopant material is preferably 30% by weight or less, and more preferably 20% by weight or less. Regarding the doping method, it can be formed by co-evaporation with the host material, but it can also be pre-mixed with the host material and then simultaneously evaporated.

[0100] Examples of luminescent materials include condensed ring derivatives of anthracene or pyrene, metal chelated oxinoid compounds such as tris(8-hydroxyquinoline)aluminum, bis(styrene) derivatives such as bis(styrene)-anthracene or styrene-benzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, violet ketone derivatives, cyclopentadiene derivatives, oxadiazole derivatives, thiadiazopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indole-carbazole derivatives, or polymers such as polyphenylacetylene derivatives, poly(p-phenylene) derivatives, and polythiophene derivatives.

[0101] The host material in a luminescent material does not need to be limited to a single compound; multiple compounds can be mixed or layered. There are no particular limitations on the host material; examples include: naphthalene, anthracene, phenanthrene, pyrene, etc. Compounds or their derivatives containing condensed aryl rings, such as tetraphenylene, triphenylene, perylene, fluoranthene, fluorene, and indene; aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine; metal chelated octyl compounds such as tris(8-hydroxyquinoline)aluminum(III); bis(styrene) derivatives such as styreneylbenzene derivatives; tetraphenylbutadiene derivatives; indene derivatives; coumarin derivatives; oxadiazole derivatives; pyrrolopyridine derivatives; violetone derivatives; cyclopentadiene derivatives; pyrrolopyrrole derivatives; thiadiazopyridine derivatives; dibenzofuran derivatives; carbazole derivatives; indolocarbazole derivatives; triazine derivatives; or polymers such as polyphenylacetylene derivatives, poly(p-phenylene) derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, and polythiophene derivatives. Among them, the main material used as the light-emitting layer for triplet emission (phosphorescence) can preferably be metal chelated octanoic compounds, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, indole-carbazole derivatives, triazine derivatives, triphenylene derivatives, etc.

[0102] Examples of dopants used in luminescent materials include: naphthalene, anthracene, phenanthrene, pyrene, fluoranthene, triphenylene, perylene, fluorene, indene, and other compounds with aryl rings or their derivatives (e.g., 2-(benzothiazol-2-yl)-9,10-diphenylanthracene or 5,6,11,12-tetraphenyltetraphenyl, etc.); furan, pyrrole, thiophene, thiophene, 9-silicon fluorene, 9,9'-spirodisilyl fluorene, benzothiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthrene, pyrazine, naphthidine, quinoxaline, pyrrolopyridine, thioxanthium, and other compounds with heteroaryl rings or their derivatives; stilbene derivatives; 4,4'-bis(2-(4-diphenylaminophenyl)vinyl)biphenyl, 4,4'-bis(N-( Aminostyryl derivatives such as stilbene-4-yl)-N-phenylamino)stilbene; aromatic acetylene derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldehyde azide derivatives, pyrrole methylene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives; coumarin derivatives such as 2,3,5,6-1H,4H-tetrahydro-9-(2'-benzothiazolyl)quinazino[9,9a,1-gh]coumarin; azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, triazole, and their metal complexes; aromatic amine derivatives such as N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine; and compounds represented by the following general formula (2). Among these, dopants containing a diamine skeleton or dopants containing a fluoranthene skeleton can further improve luminescence efficiency, and compounds represented by the following general formula (2) can further improve luminescence efficiency or durability.

[0103] [Chemistry 21]

[0104]

[0105] In general formula (2), the Za ring, Zb ring, and Zc ring are each independently formed as an aryl ring with 6 to 30 carbon atoms, either substituted or unsubstituted, or as a heteroaryl ring with 5 to 30 atoms. Preferably, the Za ring, Zb ring, and Zc ring are each independently formed as an aryl ring with 6 to 30 carbon atoms, either substituted or unsubstituted. 1 and Z 2 Each can be independently an oxygen atom, NRa (a nitrogen atom with a substituent Ra), or a sulfur atom, in Z. 1 In the case of NRa, Ra can form a ring by bonding with a Za ring or a Zb ring, or it can not form a ring. 2 In the case of NRa, Ra can bond with Zb or Zc rings to form a ring, or it may not form a ring. Ra can independently form an aryl group with 6 to 30 carbon atoms in a substituted or unsubstituted ring, a heteroaryl group with 5 to 30 atoms in a substituted or unsubstituted ring, or an alkyl group with 1 to 30 carbon atoms in a substituted or unsubstituted ring. 1 and Z 2 All are NRa, and Ra is preferably an aryl group with 6 to 30 carbon atoms, either substituted or unsubstituted. Y is a boron atom, a phosphorus atom, SiRb (a silicon atom with substituent Rb), P=O, or P=S. Rb is independently an aryl group with 6 to 30 carbon atoms, either substituted or unsubstituted, a heteroaryl group with 5 to 30 carbon atoms, either substituted or unsubstituted, or an alkyl group with 1 to 30 carbon atoms, either substituted or unsubstituted. Y is preferably a boron atom. Among all the groups, the substituents used when substituted are preferably alkyl, cycloalkyl, heterocyclic, alkenyl, cycloalkenyl, alkynyl, aryl, heteroaryl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, aryl thioether, halogen, cyano, aldehyde, acyl, carboxyl, ester, amide, sulfonyl, sulfonate, sulfonamide, amino, nitro, silyl, siloxane, oxoboryl, or oxy group. In addition, these substituents may be further substituted by the aforementioned substituents.

[0106] As alkyl and alkoxy groups, examples of alkyl and alkoxy groups exemplified as substituents in general formula (1) can be listed.

[0107] The term cycloalkyl refers to saturated alicyclic hydrocarbon groups such as cyclopropyl, cyclohexyl, norbornyl, and adamantyl, which may or may not have substituents. The number of carbon atoms in the ring formation is not particularly limited, but is preferably in the range of 3 to 20.

[0108] The term "heterocyclic group" refers to an aliphatic ring, such as a pyran ring, piperidine ring, or cyclic amide, which has atoms other than carbon atoms within the ring. It may or may not have substituents. The number of ring-forming atoms is not particularly limited, but is preferably in the range of 3 or more and 20 or less.

[0109] The term "alkenyl" refers to unsaturated aliphatic hydrocarbon groups containing double bonds, such as vinyl, allyl, and butadienyl. These groups may or may not have substituents. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0110] The term "cycloalkenyl" refers to unsaturated alicyclic hydrocarbon groups containing double bonds, such as cyclopentenyl, cyclopentadienyl, and cyclohexenyl. These groups may or may not have substituents.

[0111] The term alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as ethynyl group. It may or may not have substituents. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 or more and 20 or less.

[0112] The term "aryl" can refer to, for example, phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzo[a]fluorenyl, dibenzo[a]fluorenyl, phenanthryl, anthracene, benzo[a]phenanthryl, benzo[a]anthryl, etc. The aromatic hydrocarbon groups include phenyl, pyrene, fluoranthenyl, triphenylenyl group, benzo[di]fluorenyl, dibenzo[anthracene], peryl, and helicenyl group. Preferably, they are phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, anthracene, pyrene, fluoranthenyl, and triphenylenyl. The aryl group may or may not have substituents. The number of carbon atoms in the aryl group is not particularly limited, but is preferably 6 or more and 40 or less, more preferably 6 or more and 30 or less.

[0113] Furthermore, in a substituted phenyl group, if each of the two adjacent carbon atoms in the phenyl group has a substituent, these substituents can also form a ring structure with each other. The resulting group, depending on its structure, can be equivalent to any one or more of the following: "substituted phenyl group", "aryl group with a structure formed by two or more cyclic ring condensations", or "heteroaryl group with a structure formed by two or more cyclic ring condensations".

[0114] The term "heteroaryl" refers to cyclic aromatic groups, such as pyridyl, furanyl, phenylthio, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, naphridinyl, cinolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzophenylthio, indolyl, dibenzofuranyl, dibenzophenylthio, carbazoyl, benzocarbazoyl, carbolinyl group, indolocarbazoyl, benzofuranocarbazoyl, benzothiophenocarbazoyl, dihydroindocarbazoyl, benzoquinolinyl, acridineyl, dibenzoacridyl, benzoimidazoyl, imidazopyridyl, benzooxazolyl, benzothiazoyl, phenanthrolinel, etc., having atoms other than carbon atoms in one or more rings. The term "naphthidyl" refers to any one of 1,5-naphthidyl, 1,6-naphthidyl, 1,7-naphthidyl, 1,8-naphthidyl, 2,6-naphthidyl, or 2,7-naphthidyl. The heteroaryl group may or may not have substituents. The number of ring-forming atoms in the heteroaryl group is not particularly limited, but is preferably 3 or more and 40 or less, more preferably 3 or more and 30 or less.

[0115] An alkylthio group refers to an alkylthio group in which the oxygen atom in the ether bond of an alkoxy group is replaced by a sulfur atom. Alkylthio groups may or may not have substituents. The number of carbon atoms in an alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0116] The term "aryl ether group" refers to a functional group, such as a phenoxy group, that is bonded to an aromatic hydrocarbon group via an ether bond. It may or may not have substituents. The number of carbon atoms in the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

[0117] The term "aryl thioether group" refers to a functional group in which the oxygen atom of the ether bond in an aryl ether group is replaced by a sulfur atom. It may or may not have substituents. The number of carbon atoms in the aryl thioether group is not particularly limited, but is preferably in the range of 6 to 40.

[0118] The term halogen refers to fluorine, chlorine, bromine, or iodine.

[0119] The term "acyl group" refers to a functional group such as acetyl, propionyl, benzoyl, acryloyl, etc., that is separated from a carbonyl group and bonded with an alkyl, cycloalkyl, alkenyl, alkynyl, aryl, or heteroaryl group. It may or may not have substituents. The number of carbon atoms in the acyl group is not particularly limited, but is preferably 2 or more and 40 or less, more preferably 2 or more and 30 or less.

[0120] The term "ester group" refers to a functional group formed by alkyl, cycloalkyl, aryl, or heteroaryl groups bonded by ester bonds. It may or may not have substituents. The number of carbon atoms in the ester group is not particularly limited, but is preferably in the range of 1 to 20. More specifically, examples include: methyl ester groups such as methoxycarbonyl, ethyl ester groups such as ethoxycarbonyl, propyl ester groups such as propoxycarbonyl, butyl ester groups such as butoxycarbonyl, isopropyl ester groups such as isopropoxymethoxycarbonyl, hexyl ester groups such as hexyloxycarbonyl, and phenyl ester groups such as phenoxycarbonyl.

[0121] The term "amide group" refers to a functional group formed by a mesoamide bond, such as alkyl, cycloalkyl, aryl, or heteroaryl groups. It may or may not have substituents. The number of carbon atoms in the amide group is not particularly limited, but is preferably in the range of 1 to 20. More specifically, examples include: methylamide, ethylamide, propylamide, butylamide, isopropylamide, hexylamide, and phenylamide.

[0122] The term sulfonyl group refers to a functional group formed by a mesial -S(=O)2- bond, such as alkyl, cycloalkyl, aryl, or heteroaryl groups. It may or may not have substituents. The number of carbon atoms in the sulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.

[0123] The term "sulfonate group" refers to a functional group formed by the intercalation of alkyl, cycloalkyl, aryl, and heteroaryl groups through a sulfonate bond. It may or may not have substituents. Here, the term "sulfonate bond" refers to a sulfonate bond formed by the substitution of the carbonyl group (-C(=O)-) of an ester bond with a sulfonyl group (-S(=O)2-). The number of carbon atoms in the sulfonate group is not particularly limited, but is preferably in the range of 1 to 20.

[0124] The term "sulfonamide group" refers to a functional group formed by a sulfonamide bond, such as an alkyl, cycloalkyl, aryl, or heteroaryl group, and may or may not have substituents. Here, the term "sulfonamide bond" refers to a sulfonamide bond formed by replacing the carbonyl group (-C(=O)-) of the amide bond with a sulfonyl group (-S(=O)2-). The number of carbon atoms in the sulfonamide group is not particularly limited, but is preferably in the range of 1 to 20.

[0125] The amino group may or may not have substituents. The number of carbon atoms in the amino group is not particularly limited, but is preferably 2 or more and 50 or less, more preferably 6 or more and 40 or less, and particularly preferably in the range of 6 or more and 30 or less.

[0126] The term silane refers to a functional group formed by the bonding of substituted or unsubstituted silicon atoms. Examples include alkylsilanes such as trimethylsilane, triethylsilane, tert-butyldimethylsilane, propyldimethylsilane, and vinyldimethylsilane, or arylsilanes such as phenyldimethylsilane, tert-butyldiphenylsilane, triphenylsilane, and trinaphthylsilane. Silanes may or may not have substituents. The number of carbon atoms in a silane is not particularly limited, but is preferably in the range of 1 to 30.

[0127] The term siloxane refers to a silicon compound group, such as trimethylsiloxane, that is separated by an ether bond. Siloxanes may or may not have substituents.

[0128] The oxoboronic group may or may not have substituents.

[0129] Examples of compounds represented by general formula (2) are listed below.

[0130] [Chemistry 22]

[0131]

[0132] The organic EL element in the embodiment of the present invention is preferably an emitting layer containing a triplet emitting material.

[0133] Furthermore, the dopant used as the emitting layer for triplet emission (phosphorescence) is preferably an organometallic 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 constituting the metal complex compound is preferably a nitrogen-containing aromatic heterocycle having a phenylpyridine backbone, a phenylquinoline backbone, or a carbene backbone. However, it is not limited to these, and an appropriate complex can be selected based on the desired emission color, device performance, and relationship with the host compound. Specifically, examples include: tris(2-phenylpyridyl)iridium complex, tris{2-(2-phenylthio)pyridyl}iridium complex, tris{2-(2-benzophenylthio)pyridyl}iridium complex, tris(2-phenylbenzothiazole)iridium complex, tris(2-phenylbenzoxazole)iridium complex, tribenzoquinone iridium complex, bis(2-phenylpyridyl)(acetylacetone)iridium complex, bis{2-(2-phenylthio)pyridyl}iridium complex, bis{2-(2-benzophenylthio)pyridyl}(acetylacetone)iridium complex, and bis(2-phenylbenzothiazole)(acetylacetone). Iridium complexes, bis(2-phenylbenzoxazole)(acetylacetone)iridium complexes, bisbenzoquinone(acetylacetone)iridium complexes, bis{2-(2,4-difluorophenyl)pyridyl}(acetylacetone)iridium complexes, tetraethylporphyrin platinum complexes, {tris(thiophenecarboxyltrifluoroacetone)mono(1,10-phenanthroline)} europium complexes, {tris(thiophenecarboxyltrifluoroacetone)mono(4,7-diphenyl-1,10-phenanthroline)} europium complexes, {tris(1,3-diphenyl-1,3-propanedione)mono(1,10-phenanthroline)} europium complexes, triacetylacetone terbium complexes, etc. Additionally, phosphorescent dopants described in Japanese Patent Application Publication No. 2009-130141 may also be used preferably. Iridium complexes or platinum complexes are preferred, as they can further improve luminescence efficiency.

[0134] The triplet luminescent material used as a dopant material may contain only one type of each material in the luminescent layer, or two or more materials may be used in combination. When using two or more triplet luminescent materials, the total weight of the host material and the dopant material is set to 100% by weight, and the total weight of the dopant material is preferably 30% by weight or less, and more preferably 20% by weight or less.

[0135] There are no particular limitations on the preferred host and dopant materials in triplet emission systems; specific examples can be listed below.

[0136] [Chemistry 23]

[0137]

[0138] [Chemistry 24]

[0139]

[0140] Furthermore, the luminescent layer is preferably composed of a thermally activated delayed fluorescence (TADF) material. TADF is explained on pages 87-103 of *Advanced Organic Electroluminescence (EL)* (edited by Chihaya Adachi and Hiroshi Fujimoto, published by CMC). This literature explains that by bringing the energy levels of the excited singlet state and the excited triplet state of the fluorescent luminescent material close, reverse energy migration from the excited triplet state (with low migration probability) to the excited singlet state is typically generated with high efficiency, exhibiting thermally activated delayed fluorescence (TADF). Furthermore, Figure 5 in the aforementioned literature illustrates the mechanism of delayed fluorescence. The emission of delayed fluorescence can be confirmed by photoluminescence (PL) measurement.

[0141] Thermally activated delayed fluorescence (TADF) materials are also commonly referred to as TADF materials. TADF materials can be a single material exhibiting TADF or a combination of multiple materials. When multiple materials are included, they can be used as a mixture or as layers containing the various materials. Well-known materials can be used as TADF materials. Examples include benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indole-carbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, and oxadiazole derivatives, but are not limited to these.

[0142] Components containing TADF material in the light-emitting layer preferably further contain a fluorescent dopant in the light-emitting layer. This is because, by utilizing TADF material, triplet excitons are converted into singlet excitons, which are then accepted by the fluorescent dopant, thereby achieving higher luminous efficiency or longer lifetime.

[0143] (Electron transport layer)

[0144] In this invention, the electron transport layer refers to the layer through which electrons are injected from the cathode and then transported. For the electron transport layer, it is desirable to have high electron injection efficiency and efficient transport of 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 is unlikely to generate impurities that could become traps during manufacturing and use. Especially when stacked in thick films, low molecular weight compounds are prone to crystallization and other defects that degrade the film quality; therefore, to maintain a stable film quality, compounds with a molecular weight of 400 or higher are preferred. However, considering the balance between hole and electron transport, as long as the electron transport layer primarily functions to efficiently block holes from the anode from recombinizing and flowing towards the cathode, the effect of improving luminous efficiency is equivalent to that of using materials with low electron transport capability, even if the material contains materials with relatively low electron transport capability. Therefore, the electron transport layer of this invention also includes a hole blocking layer that efficiently blocks hole migration, serving as an electron transport layer with the same meaning. The hole blocking layer and the electron transport layer can be constructed separately or by stacking multiple materials.

[0145] Examples of electron transport materials used in the electron transport layer include condensed polycyclic aromatic derivatives of naphthalene and anthracene; styryl aromatic ring derivatives such as 4,4'-bis(diphenylvinyl)biphenyl; quinone derivatives such as anthraquinone or biphenylquinone; phosphorus oxide derivatives; various metal complexes such as tris(8-hydroxyquinoline)aluminum(III) hydroxyquinoline complexes, benzo(hydroxyquinoline) complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes, and flavonol metal complexes. For further reducing the driving voltage and obtaining higher efficiency luminescence, compounds containing elements selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus, and having a heteroaryl ring structure containing electron-accepting nitrogen, are preferred.

[0146] The electron-accepting nitrogen mentioned here refers to a nitrogen atom that forms multiple bonds with neighboring atoms. Because nitrogen atoms have high electronegativity, these multiple bonds possess electron-accepting properties. Therefore, aromatic heterocycles containing electron-accepting nitrogen exhibit high electron affinity. Electron transport materials containing electron-accepting nitrogen readily accept electrons from cathodes with high electron affinity, allowing for lower voltage operation. Furthermore, the increased supply of electrons to the luminescent layer leads to a higher recombination probability, thus further improving luminous efficiency.

[0147] Examples of heteroaryl rings containing electron-accepting nitrogen include: triazine rings, pyridine rings, pyrazine rings, pyrimidine rings, quinoline rings, quinoxaline rings, quinazoline rings, naphthidine rings, pyrimidine rings, benzoquinoline rings, phenanthrene rings, imidazole rings, oxazole rings, oxadiazole rings, triazole rings, thiazole rings, thiadiazole rings, benzoxazole rings, benzothiazole rings, benzimidazole rings, phenanthrenemidazole rings, etc.

[0148] Examples of compounds having these heteroaryl ring structures include pyridine derivatives, triazine derivatives, quinazoline derivatives, pyrimidine derivatives, benzimidazole derivatives, benzoxazole derivatives, benzothiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives such as bipyridine or terpyridine, quinoxaline derivatives, and naphthidine derivatives. From the viewpoint of electron transport capability, imidazole derivatives such as tris(N-phenylbenzimidazole-2-yl)benzene, oxadiazole derivatives such as 1,3-bis[(4-tert-butylphenyl)1,3,4-oxadiazolyl]benzene, triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproin), or 1,3-bis(1,10-phenanthroline-9-yl)benzene are preferred. ) phenanthroline derivatives such as benzene, benzoquinoline derivatives such as 2,2'-bis(benzo[h]quinoline-2-yl)-9,9'-spirodifluorene, bipyridine derivatives such as 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilanol, terpyridine derivatives such as 1,3-bis(4'-(2,2':6'2"-terpyridyl))benzene, naphthidine derivatives such as bis(1-naphthyl)-4-(1,8-naphthidyl-2-yl)phenylphosphine oxide.

[0149] Furthermore, if these derivatives have a condensed polycyclic aromatic skeleton, the glass transition temperature is increased and the electron mobility is also increased, which can further reduce the driving voltage of the organic EL device, and is therefore preferred. Moreover, considering the further improvement of device durability, ease of synthesis, and ease of obtaining raw materials, the condensed polycyclic aromatic skeleton is more preferably a fluoranthene skeleton, anthracene skeleton, pyrene skeleton, or phenanthroline skeleton.

[0150] There are no particular limitations on the preferred electron transport material; however, the following examples can be cited.

[0151] [Chemistry 25]

[0152]

[0153] In addition, the organic EL element material represented by the general formula (1) also has high electron transport properties and exhibits excellent properties as an electron transport layer, and is therefore preferred.

[0154] The electron transport material can be used alone, or two or more electron transport materials can be used in combination, or one or more other electron transport materials can be mixed into the electron transport material. Additionally, it may contain a donor compound. Here, a donor compound refers to a compound that, when used in an electron transport layer, facilitates electron injection from the cathode or electron injection layer to the electron transport layer by improving the electron injection barrier, thereby increasing the conductivity of the electron transport layer.

[0155] Preferred examples of donor compounds include: alkali metals, inorganic salts containing alkali metals, complexes of alkali metals and organic compounds, alkaline earth metals, inorganic salts containing alkaline earth metals or complexes of alkaline earth metals and organic compounds, 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 significantly improve electron transport capabilities; or alkaline earth metals such as magnesium, calcium, cerium, and barium; or rare earth metals such as samarium, europium, and ytterbium. Lithium or cesium are preferred examples of alkali metals or alkaline earth metals, provided that the driving voltage can be further reduced. Furthermore, multiple metals can be used, or alloys containing these metals can be used.

[0156] Furthermore, regarding these metals, in terms of ease of vacuum deposition and excellent operation, inorganic salts or complexes with organic compounds are preferred over metal monomers. Moreover, in terms of facilitating atmospheric operation and easily adjusting the added concentration, a complex with organic compounds is more preferred. Examples of inorganic salts include oxides such as LiO and Li₂O; nitrides; fluorides such as LiF, NaF, and KF; and carbonates such as Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃, and Cs₂CO₃. Preferred examples of organic compounds in complexes with organic compounds include hydroxyquinoline, benzo[a]hydroxyquinoline, pyridylphenol, flavonols, hydroxyimidazo[a]pyridine, hydroxybenzo[a]azole, and hydroxytriazole. From the viewpoint of further reducing the driving voltage of organic EL elements, alkali metal complexes with organic compounds, i.e., alkali metal complex compounds, are preferred. Furthermore, from the viewpoint of ease of synthesis and thermal stability, a lithium-organic complex is preferred, and lithium hydroxyquinoline (Liq), which is relatively inexpensive, is particularly preferred.

[0157] The ionization potential of the electron transport layer is not particularly limited, but is preferably 5.6 eV or higher and 8.0 eV or lower, and more preferably 5.6 eV or higher and 7.0 eV or lower.

[0158] (Electron injection layer)

[0159] In this invention, an electron injection layer may also be provided between the cathode and the electron transport layer. The electron injection layer is generally inserted to facilitate the injection of electrons from the cathode to the electron transport layer. During insertion, a compound having a heteroaryl ring structure containing electron-accepting nitrogen may be used, or a layer containing the donor material may be used.

[0160] Alternatively, inorganic materials such as insulators or semiconductors can be used in the electron injection layer. By using these materials, short circuits in organic EL devices can be suppressed and electron injection performance can be improved.

[0161] As such an insulator, it is preferably 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.

[0162] 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 or halides other than fluorides such as CaF₂, BaF₂, SrF₂, MgF₂, and BeF₂.

[0163] Furthermore, a complex of an organic compound and a metal can also be preferably used. When an organic compound and a metal complex are used in the electron injection layer, the film thickness can be easily adjusted. Preferred examples of organic compounds in such organometallic complexes include: hydroxyquinoline, benzo[a]hydroxyquinoline, pyridylphenol, flavonols, hydroxyimidazopyridine, hydroxybenzo[a]azole, hydroxytriazole, etc.

[0164] Furthermore, the layer containing the organic EL element material represented by the general formula (1) also has high electron injection capability and exhibits excellent properties as an electron injection layer, and is therefore preferred. Moreover, when using the organic EL element material represented by the general formula (1) as an electron injection layer, it is preferable to dope it with the alkali metal or rare earth metal, which can further reduce the driving voltage and further improve the durability.

[0165] (cathode)

[0166] The material used in the cathode is not particularly limited as long as it can efficiently inject electrons into the light-emitting layer. Examples of materials used in the cathode include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, or alloys or multilayers of these metals with low work function metals such as lithium, sodium, potassium, calcium, and magnesium. Among these, in terms of resistance, ease of film formation, film stability, and luminous efficiency, metals selected from aluminum, silver, and magnesium are preferred as the main components, and in terms of ease of electron injection into the electron transport layer and electron injection layer, the inclusion of magnesium and silver is more preferred.

[0167] (protective layer)

[0168] To protect the cathode, a protective layer (covering layer) is preferably laminated on the cathode. The material constituting the protective layer (covering 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 silicon dioxide, titanium dioxide, and silicon nitride; and organic polymers such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon polymers. Additionally, the material used for organic EL elements represented by general formula (1) can also be used as the covering material. In the case where the organic EL element is a structure that outputs light from the cathode side (top-emitting structure), the covering material is preferably transparent in the visible light region.

[0169] (charge generation layer)

[0170] The charge generation layer in this invention generally comprises two layers. Specifically, a pn-junction charge generation layer comprising an n-type charge generation layer and a p-type charge generation layer is preferred. The pn-junction charge generation layer generates charge by applying a voltage to the organic EL element, or by separating the charge into holes and electrons, which are then injected into the light-emitting layer via a hole transport layer and an electron transport layer. Specifically, in an organic EL element with multiple stacked light-emitting layers, the charge generation layer functions as the intermediate layer among these layers. The n-type charge generation layer supplies electrons to the first light-emitting layer located on the anode side, and the p-type charge generation layer supplies holes to the second light-emitting layer located on the cathode side. Therefore, the luminous efficiency of the organic EL element with multiple stacked light-emitting layers can be further improved, the driving voltage can be reduced, and the lifespan of the element can also be further improved.

[0171] The n-type charge generation layer comprises an n-type dopant material and a host material, which can be existing materials. For example, alkali metals, alkaline earth metals, or rare earth metals can be used as n-type dopant materials. Lithium or ytterbium is preferred as an n-type dopant material. Multiple combinations of these metals can also be used. In addition, alloys of alkali metals, alkaline earth metals, or rare earth metals with other metals can also be used. Specifically, zinc, cadmium, or bismuth can be listed as metals that can be used as materials for the alloys, but are not limited to these. As the host material, compounds with nitrogen-containing aromatic heterocycles, such as phenanthroline derivatives and oligopyridine derivatives, can be used. In addition, compounds with phosphine oxide groups can also be used. In particular, organic EL element materials represented by the general formula (1) or phenanthroline dimers exhibit excellent properties as the host of the n-type charge generation layer, and are therefore preferred. Multiple combinations of these can also be used.

[0172] The p-type charge-generating layer comprises a p-type dopant material and a host material, which can be existing materials. For example, as a p-type dopant material, tetrafluoro-7,7,8,8-tetracyanoquinone dimethane (F4-TCNQ), tetracyanoquinone dimethane derivatives, radialene derivatives, iodine, FeCl3, FeF3, SbCl5, etc., can be used. Radialene derivatives are preferred as the p-type dopant material. Arylamine derivatives are preferred as the host material.

[0173] The methods for forming the layers constituting an organic EL element are not particularly limited to resistance heating evaporation, electron beam evaporation, sputtering, molecular stacking, coating, etc. Generally, in terms of element characteristics, resistance heating evaporation or electron beam evaporation is preferred.

[0174] The total thickness of the organic layer between the anode and cathode also depends on the resistance value of the luminescent material, and therefore cannot be limited, but is preferably 1 nm to 1000 nm. The film thicknesses of the luminescent layer, electron transport layer and hole transport layer are preferably 1 nm or more and 200 nm or less, and more preferably 5 nm or more and 100 nm or less.

[0175] The organic EL element of this embodiment of the invention has the function of converting electrical energy into light. Here, direct current is mainly used as electrical energy, but pulsed current or alternating current can also be used. There are no particular limitations on the current and voltage values; however, considering the power consumption or lifespan of the element, it should be selected in a way that obtains maximum brightness with the lowest possible energy.

[0176] The organic EL element of the embodiments of the present invention can be preferably used as a display device such as a display that displays in a matrix and / or segment manner.

[0177] Furthermore, the organic EL element of the embodiments of the present invention can also be preferably used as backlighting for various devices, etc. Backlighting is mainly used to improve the visibility of display devices such as displays that do not emit light themselves, and can be used in liquid crystal displays, clocks, audio devices, automotive panels, display panels, and signs, etc. In particular, the organic EL element of the present invention can be preferably used in backlighting for personal computers in liquid crystal displays where thinner designs are being researched, providing a thinner and lighter backlight than before.

[0178] Furthermore, the organic EL element of the embodiments of the present invention can also be preferably used as various lighting devices. The organic EL element of the embodiments of the present invention can achieve both high luminous efficiency and high color purity, and thus can be made thin or lightweight, thereby realizing lighting devices that combine low power consumption, bright luminous color, and high design flexibility.

[0179] Example

[0180] The present invention will be described below with examples, but the present invention is not limited to these examples.

[0181] Synthesis Example 1: Synthesis of Compound 5

[0182] [Chemistry 26]

[0183]

[0184] Under a nitrogen stream and at 0°C, 13 ml of n-butyllithium (1.6 M hexane solution) was added dropwise to a mixed solution of 4.0 g of 1-bromo-3-chlorobenzene and 30 ml of tetrahydrofuran. After stirring at 0°C for 1 hour, the solution was added dropwise to a mixed solution of 4.5 g of 2-phenyl-1,10-phenanthroline and 30 ml of tetrahydrofuran at 0°C. After warming to room temperature, the reaction solution was extracted with dichloromethane, leaving 100 ml of solvent, which was then evaporated. 10.0 g of manganese dioxide was added to the resulting solution, and after stirring at room temperature for 4 hours, magnesium sulfate was added and the mixture was filtered. The solvent was removed by evaporation. The resulting solid was purified by silica gel column chromatography, with the solvent removed by evaporation, and the solid was dried under vacuum to obtain 6.0 g of intermediate A.

[0185] Next, a mixed solution of intermediate A (3.0 g), borate ester A (3.7 g), dichlorobis(triphenylphosphine palladium) dichloride (160 mg), 1.5 M tripotassium phosphate aqueous solution (7 ml), and 1,4-dioxane (80 ml) was heated and stirred under reflux for 7 hours under a nitrogen atmosphere. After cooling to room temperature, water was added, the precipitated solid was filtered, washed with methanol, and then dried under vacuum. The resulting solid was dissolved in a mixed solvent of toluene and pyridine, and the solvent was removed using activated carbon. After washing the solid obtained by evaporation of the solvent with toluene and methanol, the solid was dried under vacuum to obtain 3.0 g of compound 5.

[0186] Regarding the obtained compound 5, an oil diffusion pump was used at 1×10⁻⁶. -3 The compound 5 was purified by sublimation at a pressure of Pa and a temperature of approximately 360°C. The high-performance liquid chromatography (HPLC) purity (area %) of compound 5 before and after sublimation purification was 99.9%.

[0187] After sublimation and purification, the samples were analyzed by mass spectrometry (MS). 1 The structure of compound 5 was identified by 1H-nuclear magnetic resonance (NMR) analysis. The analytical results are shown below.

[0188] MS (m / z): 640 [M+H] +

[0189] 1 H-NMR (400MHz, CDCl3) δ: 8.94 (s, 1H), 8.81-8.87 (m, 2H), 8.65-8.74 (m, 4H), 8.40-8.5 2(m,3H),8.23-8.40(m,4H),7.78-7.99(m,6H),7.64-7.78(m,2H),7.31-7.50(m,4H).

[0190] Synthesis Example 2: Synthesis of Compound 10

[0191] [Chemistry 27]

[0192]

[0193] A mixture of 10.0 g of 8-aminoquinoline-7-carboxaldehyde, 13.1 g of 1-(4-bromonaphthyl-1-yl)ethane-1-one, 50 ml of 2.0 M potassium hydroxide aqueous solution, and 250 ml of ethanol was heated and stirred at 70 °C for 5 hours under a nitrogen atmosphere. After cooling to room temperature, water was added, the precipitated solid was filtered, and the resulting solid was washed with methanol and dried under vacuum to obtain 12.1 g of intermediate B.

[0194] Next, a mixed solution of 3.0 g of intermediate B, 3.6 g of borate ester B, 160 mg of dichlorobis(triphenylphosphine palladium) dichloride, 7 ml of 1.5 M tripotassium phosphate aqueous solution, and 70 ml of 1,4-dioxane was heated and stirred under reflux for 7 hours under a nitrogen atmosphere. After cooling to room temperature, water was added, the precipitated solid was filtered, washed with methanol, and then dried under vacuum. The resulting solid was dissolved in a mixed solvent of toluene and pyridine, and the catalyst was removed using activated carbon. After washing the solid obtained by evaporating the solvent with toluene and methanol, it was dried under vacuum to obtain 2.7 g of compound 10.

[0195] Regarding the obtained compound 10, an oil diffusion pump was used at 1×10⁻⁶. -3 The compound 1 was purified by sublimation at a pressure of Pa and a temperature of approximately 360°C. The HPLC purity (area %) of compound 1 before and after sublimation purification was 99.9%.

[0196] After sublimation and purification, the samples were analyzed by mass spectrometry (MS). 1 The structure of compound 10 was identified by 1H-NMR analysis. The analytical results are shown below.

[0197] MS (m / z): 614 [M+H] +

[0198] 1 H-NMR (400MHz, CDCl3) δ: 9.23 (s, 1H), 8.84-8.88 (m, 2H), 8.65-8.79 (m, 3H), 8.34-8.43 (m, 1H), 8.24-8.34(m,1H),7.82-8.20(m,9H),7.58-7.74(m,4H),7.42-7.52(m,2H),7.31-7.42(m,2H).

[0199] Secondly, the evaluation methods in each embodiment will be explained.

[0200] (Driving voltage)

[0201] The components obtained in Examples 1 to 12 and Comparative Examples 1 to 14 were respectively subjected to an A / cm2 DC drive was performed, and the initial drive voltage was measured. Furthermore, the voltage was measured at a current density of 10 mA / cm² at a temperature of 70°C. 2 Calculate the voltage rise from the initial drive voltage after 100 hours of DC drive.

[0202] In addition, the organic EL elements obtained in Examples 13 to 24 and Comparative Examples 15 to 28 were respectively tested at a brightness of 1000 cd / m². 2 Light the lamp and measure the initial driving voltage. Additionally, measure the voltage at room temperature with a current density of 10 mA / cm². 2 The voltage after 100 hours of constant current driving. Calculate the voltage rise from the start of the measurement to 100 hours later.

[0203] In addition, the organic EL elements obtained in Examples 25 to 63 and Comparative Examples 29 to 70 were subjected to an A / cm² voltage of 10 mA / cm². 2 Driven by current density, the initial driving voltage is measured.

[0204] A lower initial driving voltage allows for driving at lower voltages, thus indicating better luminous efficiency (brightness / power). Furthermore, a smaller voltage rise indicates better durability.

[0205] (External quantum efficiency)

[0206] The organic EL devices obtained in Examples 13-24 and Comparative Examples 15-28 were subjected to a current density of 10 mA / cm². 2 Light the lamp, measure the external quantum efficiency, and evaluate the luminous efficiency. The higher the external quantum efficiency, the better the luminous efficiency.

[0207] (brightness)

[0208] The organic EL elements obtained in Examples 25 to 63 and Comparative Examples 29 to 70 were subjected to an A / cm² voltage of 10 mA. 2 Light the lamp, measure its brightness, and evaluate its luminous efficiency. Higher brightness indicates better luminous efficiency.

[0209] (Durability lifespan)

[0210] The organic EL elements obtained in Examples 13 to 63 and Comparative Examples 15 to 70 were subjected to an A / cm² voltage of 10 mA. 2 The constant current continues to drive. The time it takes for the brightness to decrease by 20% from the starting point of measurement is taken as the durability life.

[0211] Example 1

[0212] A glass substrate (manufactured by Geomatec, Inc., 11Ω / Y, sputtered) with a 125nm ITO transparent conductive film deposited as the anode was cut into 38mm × 46mm pieces and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using Semico Clean (registered trademark) 56 (trade name, manufactured by Gunai Chemical, Inc.), followed by rinsing with ultrapure water. Prior to component fabrication, the substrate underwent a 1-hour UV-ozone treatment in a vacuum evaporation apparatus, where exhaust was performed until the vacuum level reached 5 × 10⁻⁶. -4 Up to Pa. Using a resistance heating method, compound 1 and the dopant metal element Li were deposited at a deposition rate ratio of compound 1:Li = 99:1 for 100 nm, forming a layer with a weight ratio of 99:1. Then, aluminum was deposited for 60 nm as a cathode to fabricate a 5 mm × 5 mm square element. The film thickness described here is the value displayed by a quartz oscillating film thickness monitor, which is also common in other embodiments and comparative examples.

[0213] The device was evaluated using the method described above, and the initial driving voltage was 0.029V, with a voltage rise of 0.001V after driving at 70°C for 100 hours.

[0214] [Chemistry 28]

[0215]

[0216] Examples 2 to 12, Comparative Examples 1 to 14

[0217] Except for the changes in the compounds used and the vapor deposition rate ratio of the compounds to the metal elements as described in Table 1, the components were fabricated in the same manner as in Example 1. The results of each example and comparative example are shown in Table 1. Furthermore, compounds 2 to 26 are the compounds shown below.

[0218] [Chemistry 29]

[0219]

[0220] [Chemistry 30]

[0221]

[0222] [Chemistry 31]

[0223]

[0224] [Chemistry 32]

[0225]

[0226] [Table 1]

[0227] [Table 1]

[0228]

[0229] Example 13

[0230] A glass substrate (manufactured by Geomatec, Inc., 11Ω / Y, sputtered) with a 165nm ITO transparent conductive film deposited as the anode was cut into 38mm × 46mm pieces and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using Semico Clean 56 (trade name, manufactured by Gunai Chemical Co., Ltd.), followed by rinsing with ultrapure water. Prior to component fabrication, the substrate underwent a 1-hour UV-ozone treatment in a vacuum evaporation apparatus, where exhaust was performed until the vacuum level reached 5 × 10⁻⁶. -4 Up to Pa, the process is as follows: First, a 5 nm thick HAT-CN6 layer is deposited as a hole injection layer using resistance heating, followed by a 50 nm thick HT-1 layer as a hole transport layer. Next, a 20 nm thick layer of a mixture of the host material H-1 and the dopant material D-1 is deposited at a doping concentration of 5% by weight to serve as the light-emitting layer. Then, a 35 nm thick layer of ET-1 and 2E-1 is deposited at a deposition rate ratio of ET-1:2E-1 = 1:1 to serve as the electron transport layer. Next, a 10 nm thick layer of compound 1 and the dopant metal element Li is deposited at a deposition rate ratio of compound 1:Li = 99:1 to serve as the electron injection layer. Finally, 60 nm of aluminum is deposited as the cathode to fabricate a 5 mm × 5 mm square organic EL device.

[0231] The organic EL device was evaluated using the method described above, and the results showed an initial driving voltage of 4.00 V, an external quantum efficiency (luminous efficiency) of 5.79%, a lifetime of 1080 hours, and a voltage rise of 0.001 V after 100 hours of driving at room temperature. Furthermore, HAT-CN6, HT-1, H-1, D-1, ET-1, and 2E-1 are the compounds shown below.

[0232] [Chemistry 33]

[0233]

[0234] Examples 14-24, Comparative Examples 15-28

[0235] Organic EL elements were fabricated in the same manner as in Example 13, except that the compounds used and the vapor deposition rate ratio of the compounds to the metal elements were changed as described in Table 2. The results of each example and comparative example are shown in Table 2.

[0236] [Table 2]

[0237] [Table 2]

[0238]

[0239] Example 25

[0240] A glass substrate (manufactured by Geomatec, Inc., 11Ω / Y, sputtered) with a 165nm ITO transparent conductive film deposited as the anode was cut into 38mm × 46mm pieces and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using Semico Clean 56 (trade name, manufactured by Gunai Chemical Co., Ltd.), followed by rinsing with ultrapure water. Prior to component fabrication, the substrate underwent a 1-hour UV-ozone treatment in a vacuum evaporation apparatus, where exhaust was performed until the vacuum level reached 5 × 10⁻⁶. -4 Up to Pa. First, a 5nm HAT-CN6 layer is deposited as a hole injection layer using a resistance heating method. Then, a light-emitting unit (first light-emitting unit) comprising a hole transport layer, a light-emitting layer, and an electron transport layer is formed on the hole injection layer.

[0241] Specifically, HT-1 with a thickness of 50 nm is deposited as a hole transport layer. Next, a mixed layer of host material H-1 and dopant material D-1 with a doping concentration of 5% by weight is deposited with a thickness of 20 nm as a light-emitting layer. Then, ET-1 and 2E-1 are deposited with a deposition rate ratio of ET-1:2E-1 = 1:1 with a thickness of 35 nm as an electron transport layer.

[0242] On the first light-emitting unit, compound 1 and metal element Li as a dopant are deposited at a deposition rate ratio of compound 1:Li = 99:1 for 10 nm to serve as an n-type charge generation layer, and then HAT-CN6 is deposited at a deposition rate ratio of 1:Li = 99:1 for 10 nm to serve as a p-type charge generation layer.

[0243] In the charge generation layer, a second light-emitting unit is formed in the same manner as the first light-emitting unit. Then, compound 1 and the metal element Li as a dopant are deposited at a deposition rate ratio of compound 1:Li = 99:1 for 10 nm as an electron injection layer. Then, aluminum is deposited for 60 nm as a cathode to fabricate an organic EL device with dimensions of 5 mm × 5 mm.

[0244] The organic EL element was evaluated using the method described above, and the results showed an initial driving voltage of 8.21V and a luminance of 1760 cd / m². 2 Its durability is 2620 hours.

[0245] Examples 26–38, Comparative Examples 29–42

[0246] Except for the changes in the compounds used and the deposition rate ratio of the compounds to the metal element as described in Table 3, the organic EL element was fabricated in the same manner as in Example 25. In Example 37, compound 1, ET-2, and the metal element Li were deposited at a deposition rate ratio of compound 1:ET-2:Li = 49.5:49.5:1 for 10 nm to serve as an n-type charge generation layer. In Example 38, a mixed layer of host material H-1 and dopant material D-2 was deposited at a doping concentration of 5% by weight to a thickness of 20 nm to serve as a light-emitting layer. The results of each example and comparative example are shown in Table 3. Furthermore, D-2 and ET-2 are the compounds shown below.

[0247] [Chemistry 34]

[0248]

[0249] [Table 3]

[0250] [Table 3]

[0251]

[0252] Example 39

[0253] The organic EL element was fabricated in the same manner as in Example 25, except that compound 1 was used instead of ET-1 in the formation of the electron transport layer and ET-2 was used instead of compound 1 in the formation of the n-type charge generation layer.

[0254] The organic EL element was evaluated using the method described above, and the results showed an initial driving voltage of 8.20V and a luminance of 1790 cd / m². 2 Its durability is 2600 hours.

[0255] Examples 40-50, Comparative Examples 43-56

[0256] Organic EL elements were fabricated in the same manner as in Example 39, except that the compounds used and the vapor deposition rate ratio of the compounds to the metal elements were changed as described in Table 4. The results of each example and comparative example are shown in Table 4.

[0257] [Table 4]

[0258] [Table 4]

[0259]

[0260] Examples 51 to 63, Comparative Examples 57 to 70

[0261] Except for changing the types of compounds, metal elements and evaporation rate ratios used as described in Table 5, organic EL elements were fabricated in the same manner as in Example 25.

[0262] [Table 5]

[0263] [Table 5]

[0264]

Claims

1. A material for an organic electroluminescent element, represented by the following general formula (1): In general formula (1), X 3 X is a nitrogen atom. 1 and X 2 It is methine; L 1 For substituted or unsubstituted phenylene, substituted or unsubstituted naphthylene, or substituted or unsubstituted anthracene, L 2 It is a single bond, a substituted or unsubstituted phenylene, a substituted or unsubstituted naphthylene, or a substituted or unsubstituted anthraceneylene; wherein, When these groups are substituted, the substituents are alkyl or alkoxy; A is phenyl or pyridyl, and n is 1.

2. The material for organic electroluminescent devices according to claim 1, wherein in the general formula (1), A is phenyl.

3. The material for organic electroluminescent devices according to claim 1 or 2, wherein in the general formula (1), L 1 or L 2 It is a naphthyl group.

4. The material for organic electroluminescent devices according to claim 1 or 2, wherein in the general formula (1), L 2 It is a single key.

5. An organic electroluminescent element, which has at least an electron transport layer and a light-emitting layer between an anode and a cathode and emits light through electrical energy, wherein the electron transport layer contains the material for an organic electroluminescent element as described in any one of claims 1 to 4.

6. The organic electroluminescent element according to claim 5, wherein the electron transport layer further comprises an alkali metal complex compound.

7. An organic electroluminescent element having at least a charge-generating layer and a light-emitting layer between an anode and a cathode and emitting light by means of electrical energy, wherein the charge-generating layer contains a material for an organic electroluminescent element as described in any one of claims 1 to 4.

8. The organic electroluminescent element according to claim 7, wherein the charge generating layer further comprises phenanthroline dimer.

9. The organic electroluminescent element according to claim 7, wherein the charge generating layer further comprises an alkali metal or a rare earth metal.

10. The organic electroluminescent element according to claim 9, wherein the alkali metal is Li.

11. The organic electroluminescent element according to claim 9, wherein the rare earth metal is Yb.

12. The organic electroluminescent element according to claim 7, wherein the light-emitting layer contains a compound represented by the following general formula (2): In general formula (2), the Za ring, Zb ring, and Zc ring are independently substituted or unsubstituted rings forming aryl rings with 6 to 30 carbon atoms, or substituted or unsubstituted rings forming heteroaryl rings with 5 to 30 atoms; Z 1 and Z 2 Each can be independently an oxygen atom, NRa, or a sulfur atom, where NRa is a nitrogen atom with a substituent Ra, in Z 1 In the case of NRa, it can form a loop by bonding with either A-ring or B-ring, or it can not form a loop, in Z 2 In the case of NRa, it may form a ring by bonding with the B ring or the C ring, or it may not form a ring; Ra is independently formed by a substituted or unsubstituted ring forming an aryl group with 6 to 30 carbon atoms, a substituted or unsubstituted ring forming a heteroaryl group with 5 to 30 atoms, or a substituted or unsubstituted alkyl group with 1 to 30 carbon atoms; Y is a boron atom, a phosphorus atom, SiRb, P=O, or P=S, wherein SiRb is a silicon atom having a substituent Rb; Rb is independently selected from substituted or unsubstituted aryl groups with 6 to 30 carbon atoms, a substituted or unsubstituted ring forming a heteroaryl group with 5 to 30 atoms, or a substituted or unsubstituted alkyl group with 1 to 30 carbon atoms.

13. An organic electroluminescent element having at least an electron injection layer and a light-emitting layer between an anode and a cathode and emitting light by means of electrical energy, wherein the electron injection layer contains a material for an organic electroluminescent element as described in any one of claims 1 to 4.

14. A display device comprising an organic electroluminescent element as claimed in any one of claims 5 to 13.

15. A lighting device comprising an organic electroluminescent element as claimed in any one of claims 5 to 13.

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