Compound, light-emitting element containing same, display device, and illumination device

Abstract

The purpose of the present invention is to provide an organic EL element having excellent luminous efficacy and durability life. The present invention provides a compound which is represented by following general formula (1). (In general formula (1), L represents a single bond, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group; A represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; B represents a substituent represented by general formula (2), and is bonded to a phenanthroline skeleton in general formula (1) at a position indicated by * in general formula (2); and L-A does not have the same structure as that of B.) (In general formula (2), R1 to R9 each independently represent a hydrogen atom, a halogen atom, an alkyl group, or an unsubstituted phenyl group, but R1 to R9 are never bonded to each other so as to form a ring.)

Description

Compound, light-emitting element, display device and lighting device containing the same

[0001] The present invention relates to a compound, and a light-emitting device, a display device, and a lighting device using the compound.

[0002] An organic EL element is a light-emitting element that has an anode, a cathode, and an organic layer interposed therebetween, and the organic layer emits light when exposed to electrical energy. In recent years, organic EL elements have been steadily put to practical use, including their adoption in television and smartphone displays. However, existing organic EL elements still have many technical challenges. Obtaining highly efficient light emission and extending the lifespan of organic EL elements are particularly challenging.

[0003] As compounds that solve these problems, phenanthroline derivatives having specific substituents have been developed (see, for example, Patent Documents 1 to 7).

[0004] Japanese Patent Publication No. 2003-338377 International Publication No. 2018 / 190522 Chinese Patent Application Publication No. 116375743 Chinese Patent Application Publication No. 116969935 Chinese Patent Application Publication No. 106565705 International Publication No. 2016 / 121597 International Publication No. 2024 / 043018

[0005] According to the techniques described in Patent Documents 1 to 7, it is possible to obtain organic EL elements that have high luminous efficiency, can be driven at a low voltage, and have excellent durability. However, in recent years, the luminous efficiency and durability required of organic EL elements have been increasing, and there is a demand for techniques that can achieve both higher luminous efficiency and a longer durable life.

[0006] In view of the above problems of the prior art, an object of the present invention is to provide an organic EL element having excellent luminous efficiency and durable life.

[0007] In order to solve the above problems, the present invention has the following features: [1] A compound represented by the following general formula (1):

[0008]

[0009] (In general formula (1), L is a single bond, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group. A is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. B is a substituent represented by general formula (2) and is bonded to the phenanthroline skeleton in general formula (1) at the position marked * in general formula (2). L-A does not have the same structure as B.)

[0010]

[0011] (In general formula (2), R １ ~R ９ are each independently a hydrogen atom, a halogen atom, an alkyl group, or an unsubstituted phenyl group, and R １ ~R ９ do not bond to each other to form a ring.) [2] In the general formula (1), R １ ~R ９ is a hydrogen atom. [3] The compound according to [1] or [2], wherein in the general formula (1), L is a single bond or a substituted or unsubstituted arylene group. [4] The compound according to any one of [1] to [3], wherein in the general formula (1), A is a substituted or unsubstituted aryl group having 10 or more ring atoms or a substituted or unsubstituted heteroaryl group having 10 or more ring atoms. [5] The compound according to any one of [1] to [3], wherein in the general formula (1), A is a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolinyl group, or a substituted or unsubstituted phenanthrolinyl group, and when these are substituted, the substituent is an aryl group or a pyridyl group. [6] The compound according to any one of [1] to [3], wherein in the general formula (1), L is a substituted or unsubstituted arylene group and A is selected from the following groups:

[0012]

[0013] (* indicates the bonding position with L, and these groups may be substituted with an aryl group.) [7] A light-emitting device which emits light in response to electric energy, having at least an electron transport layer and an emitting layer between an anode and a cathode, wherein the electron transport layer contains the compound according to any one of [1] to [6]. [8] The light-emitting device according to [7], wherein the electron transport layer further contains an alkali metal complex compound. [9] A light-emitting device which emits light in response to electric energy, having at least a charge generation layer and an emitting layer between an anode and a cathode, wherein the charge generation layer contains the compound according to any one of [1] to [6].

[10] The light-emitting device according to [9], wherein the charge generation layer further contains a phenanthroline derivative.

[11] The light-emitting device according to [9] or

[10] , wherein the charge generation layer further contains an alkali metal atom and a rare earth metal atom.

[12] The light-emitting device according to

[10] or

[11] , wherein the alkali metal atom is Li.

[13] The light-emitting device according to

[10] or

[11] , wherein the rare earth metal atom is Yb.

[14] A light-emitting element which emits light by electrical energy, having at least an electron-injecting layer and a light-emitting layer between an anode and a cathode, wherein the electron-injecting layer contains the compound according to any one of [1] to [6].

[15] A display device comprising a light-emitting element containing the compound according to any one of [1] to [6].

[16] A lighting device comprising a light-emitting element containing the compound according to any one of [1] to [6].

[0014] According to the present invention, an organic EL element having excellent luminous efficiency and durability can be provided.

[0015] Preferred embodiments of the compound, light-emitting element, display device, and lighting device according to the present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and can be practiced with various modifications depending on the purpose and application.

[0016] (Compound Represented by General Formula (1)) The compound according to the embodiment of the present invention is a compound represented by general formula (1).

[0017]

[0018] In general formula (1), L is a single bond, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group. A is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. B is a substituent represented by general formula (2) and is bonded to the phenanthroline skeleton in general formula (1) at the position marked * in general formula (2). L-A does not have the same structure as B.

[0019]

[0020] In general formula (2), R １ ~R ９ are each independently a hydrogen atom, a halogen atom, an alkyl group, or an unsubstituted phenyl group, and R １ ~R ９ do not bond to each other to form a ring.

[0021] In all of the above groups, a hydrogen atom may be a deuterium atom, as well as in the substituents, compounds, and partial structures thereof described below.

[0022] The term "unsubstituted" in the context of "substituted or unsubstituted" means that a hydrogen atom or a deuterium atom has been substituted. The same applies to the term "substituted or unsubstituted" in the compounds or partial structures thereof described below.

[0023] The halogen atom refers to fluorine, chlorine, bromine or iodine.

[0024] The aryl group refers to an aromatic hydrocarbon group such as a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzanthracenyl group, a perylenyl group, or a helicenyl group.

[0025] The heteroaryl group refers to a cyclic aromatic group having one or more atoms other than carbon in the ring, such as a pyridyl group, a furanyl group, a thiophenyl group, a quinolinyl group, an isoquinolinyl group, a pyrazinyl group, a pyrimidyl group, a pyridazinyl group, a triazinyl group, a naphthyridinyl group, a cinnolinyl group, a phthalazinyl group, a quinoxalinyl group, a quinazolinyl group, a benzofuranyl group, a benzothiophenyl group, an indolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, a benzocarbazolyl group, a carbolinyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a dihydroindenocarbazolyl group, a benzoquinolinyl group, an acridinyl group, a dibenzoacridinyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, or a phenanthrolinyl group. Here, the naphthyridinyl group refers to any one of a 1,5-naphthyridinyl group, a 1,6-naphthyridinyl group, a 1,7-naphthyridinyl group, a 1,8-naphthyridinyl group, a 2,6-naphthyridinyl group, and a 2,7-naphthyridinyl group. The number of ring atoms is not particularly limited, but is preferably in the range of 3 to 40, more preferably 3 to 30.

[0026] The alkyl group refers to a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group. The number of carbon atoms in the alkyl group is not particularly limited, but from the viewpoints of availability and cost, it is preferably in the range of 1 to 20, more preferably 1 to 8. The number of carbon atoms referred to here includes the number of carbon atoms contained in a substituent bonded to the alkyl group, and the same applies to other substituents that specify the number of carbon atoms.

[0027] The arylene group refers to a divalent aromatic hydrocarbon group such as a phenylene group, a biphenylene group, a terphenylene group, a naphthylene group, a fluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenanthrylene group, or an anthracenylene group, and a plurality of these groups may be linked together. The arylene group may or may not have a substituent. The number of carbon atoms in the arylene group is not particularly limited, but is preferably in the range of 6 to 40, more preferably 6 to 30.

[0028] The heteroarylene group refers to a divalent or higher group derived from an aromatic group having one or more atoms other than carbon in the ring, such as pyridine, quinoline, pyrimidine, pyrazine, triazine, quinoxaline, quinazoline, dibenzofuran, or dibenzothiophene. The heteroarylene group may or may not have a substituent. Preferred heteroarylene groups are divalent or trivalent heteroarylene groups. The number of carbon atoms in the heteroarylene group is not particularly limited, but is preferably in the range of 2 to 30. Specific examples of the heteroarylene group include a 2,6-pyridylene group, a 2,5-pyridylene group, a 2,4-pyridylene group, a 3,5-pyridylene group, a 3,6-pyridylene group, a 2,4,6-pyridylene group, a 2,4-pyrimidinylene group, a 2,5-pyrimidinylene group, a 4,6-pyrimidinylene group, a 2,4,6-pyrimidinylene group, a 2,4,6-triazinylene group, a 4,6-dibenzofuranylene group, a 2,6-dibenzofuranylene group, a 2,8-dibenzofuranylene group, and a 3,7-dibenzofuranylene group.

[0029] As conventional compounds containing nitrogen-containing aromatic heterocycles and polycyclic aromatic hydrocarbons, for example, Patent Documents 1 to 7 disclose compounds U, V, W, X, Y, and Z represented by the following formulas.

[0030]

[0031] However, even in devices using these compounds as materials for organic EL devices in the electron injection layer, electron transport layer or charge generation layer, sufficient performance has not yet been achieved in relation to the characteristics required in recent years.

[0032] For example, a compound such as Compound U in which two ortho-substituted biphenyl groups are substituted on phenanthroline has high structural symmetry and therefore high crystallinity. When an attempt is made to form a film by vapor deposition, there are problems in that the film stability and handling properties are reduced, the driving voltage is increased, and the luminous efficiency and durability life are reduced.

[0033] Compounds V and Y, which are diphenylfluorenyl groups substituted with aryl groups or compounds in which the aryl group has a dibenzothienyl group, have bulky substituents near the nitrogen atom on the highly coordinating phenanthrolinyl group, which tend to reduce the coordination ability of the phenanthrolinyl group to metal atoms. Therefore, when compounds V and Y are used together with metal atoms, the stability of the film decreases, the driving voltage increases, and the luminous efficiency and durability life decrease.

[0034] In compounds such as Compounds W, X, and Z in which a heteroaryl group is substituted on an ortho-substituted biphenyl group, the ortho-substituted biphenylene group is twisted relative to the plane of the phenanthrolinyl group, which breaks the intramolecular conjugation between the heteroaryl group and the phenanthrolinyl group, resulting in a decrease in electron transport properties, an increase in the driving voltage of the device, and a decrease in luminous efficiency and durability.

[0035] In investigating improvements, the present inventors focused on the effect of the substituents substituted on the phenanthroline skeleton.

[0036] The compound represented by general formula (1) has an ortho-biphenyl group introduced into the phenanthroline skeleton, which provides the compound with suitable crystallinity and thermal stability, while suppressing an increase in sublimation temperature and improving handleability. Furthermore, the electron mobility is appropriately reduced, which improves the carrier balance when used in a light-emitting device, thereby improving the luminous efficiency.

[0037] In general formula (1), L represents a single bond, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group, and is preferably a single bond or a substituted or unsubstituted arylene group.

[0038] A is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. In order to increase the glass transition temperature and thermal stability of the vapor-deposited film, A is preferably a substituted or unsubstituted aryl group having 10 or more ring atoms or a substituted or unsubstituted heteroaryl group having 10 or more ring atoms.

[0039] An aryl group having 10 or more ring atoms is a polycyclic aromatic hydrocarbon group in which 10 or more carbon atoms are condensed to form a single ring structure. Specific examples include a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzanthracenyl group, a perylenyl group, and a helicenyl group.

[0040] A heteroaryl group having 10 or more ring atoms is a cyclic aromatic group having one or more atoms other than carbon in the ring, the total number of atoms being 10 or more, and forming a single fused ring structure. Specific examples include a quinolinyl group, an isoquinolinyl group, a naphthyridinyl group, a cinnolinyl group, a phthalazinyl group, a quinoxalinyl group, a quinazolinyl group, a benzofuranyl group, a benzothiophenyl group, an indolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, a benzocarbazolyl group, a carbolinyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a dihydroindenocarbazolyl group, a benzoquinolinyl group, an acridinyl group, a dibenzoacridinyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, and a phenanthrolinyl group.

[0041] In general formula (2), R １ ~R ９ are each independently a hydrogen atom, a halogen atom, an alkyl group, or an unsubstituted phenyl group, and R １ ~R ９ do not bond to each other to form a ring. １ ~R ９is preferably a hydrogen atom, since the coordination ability of the nitrogen atom on the phenanthrolinyl group is further improved.

[0042] Furthermore, when the compound represented by general formula (1) is co-deposited with a metal, the coordination ability of the compound represented by general formula (1) to a metal atom can be further enhanced by substituting a coordinating substituent. Therefore, A is also preferably a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolinyl group, or a substituted or unsubstituted phenanthrolinyl group, and when these are substituted, the substituent is preferably an aryl group or a pyridyl group.

[0043] In general formula (1), it is also preferred that L is a substituted or unsubstituted arylene group and A is selected from the following groups:

[0044]

[0045] In the above groups, * indicates the bonding position to L, and these groups may be substituted with an aryl group.

[0046] L-A does not have the same structure as B. If L-A has the same structure as B, the symmetry of the compound structure will be high, resulting in high crystallinity, which will result in reduced film stability and handling properties when attempting to form a film by vapor deposition.

[0047] The molecular weight of the compound represented by general formula (1) is preferably 450 or more from the viewpoint of suppressing crystallization and improving the stability of film quality, while the molecular weight of the compound represented by general formula (1) is preferably 800 or less from the viewpoint of improving processability during sublimation purification and vapor deposition.

[0048] Examples of the compound represented by general formula (1) include the compounds shown below. Note that the following are merely examples, and compounds other than those explicitly listed here can also be preferably used as long as they are represented by general formula (1).

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] The compound represented by general formula (1) can be synthesized by a known synthesis method, such as, but not limited to, a coupling reaction between a boronic acid derivative and a halogenated arylene or halogenated heteroarylene derivative.

[0073] The compound represented by general formula (1) is preferably used in any layer of a light-emitting device. As will be described later, the compound represented by general formula (1) is suitably used in a hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, charge generation layer, protective film (cap layer) for an electrode, etc., in a light-emitting device. By using the material represented by general formula (1) in any layer of a light-emitting device, a light-emitting device excellent in luminous efficiency and durable life can be provided.

[0074] (Light-emitting element) A light-emitting element according to an embodiment of the present invention has an anode, a cathode, and an organic layer interposed between the anode and the cathode, and the organic layer emits light when exposed to electrical energy. In the following description, such a light-emitting element may be referred to as an "organic EL element."

[0075] The layer configuration between the anode and the cathode in the organic EL element may be a configuration consisting of only an emitting layer, or may be a laminate configuration such as 1) emitting layer / electron transport layer, 2) hole transport layer / emitting layer, 3) hole transport layer / emitting layer / electron transport layer, 4) hole injection layer / hole transport layer / emitting layer / electron transport layer, 5) hole transport layer / emitting layer / electron transport layer / electron injection layer, 6) hole injection layer / hole transport layer / emitting layer / electron transport layer / electron injection layer, or 7) hole injection layer / hole transport layer / emitting layer / hole blocking layer / electron transport layer / electron injection layer.

[0076] Furthermore, a tandem type may be used in which a plurality of the above-described laminated structures are laminated via an intermediate layer. The intermediate layer is generally also called an intermediate electrode, intermediate conductive layer, charge generation layer, electron extraction layer, connection layer, or intermediate insulating layer, and a known material structure can be used. Specific examples of the tandem type include laminated structures including a charge generation layer as an intermediate layer between an anode and a cathode, such as 8) hole transport layer / light-emitting layer / electron transport layer / charge generation layer / hole transport layer / light-emitting layer / electron transport layer, and 9) 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.

[0077] 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 doped with a metal, which can improve the electron transport ability and the electron injection ability into adjacent layers. Furthermore, a protective layer (capping layer) may be further provided in addition to the above layers, which can further improve the luminous efficiency by optical interference. The compound represented by general formula (1) may be used in any of the above layers in an organic EL device, but is particularly suitable for use in the electron transport layer, charge generation layer, or electron injection layer. Preferred organic EL devices according to embodiments of the present invention include a configuration having at least an electron transport layer and an emitting layer between an anode and a cathode, with the electron transport layer containing a compound represented by general formula (1); a configuration having at least a charge generation layer and an emitting layer between an anode and a cathode, with the charge generation layer containing a compound represented by general formula (1); and a configuration having at least an electron injection layer and an emitting layer between an anode and a cathode, with the electron injection layer containing a compound represented by general formula (1).

[0078] In the organic EL element according to the embodiment of the present invention, the anode and cathode have the role of supplying a sufficient current for the element to emit light, and it is desirable that at least one of them is transparent or semi-transparent in order to extract light. Usually, the anode formed on the substrate is used as the transparent electrode.

[0079] (Substrate) In order to maintain the mechanical strength of the organic EL element, it is preferable to form the organic EL element on a substrate. Examples of the substrate include glass substrates such as soda glass and alkali-free glass, and plastic substrates. The thickness of the glass substrate is sufficient to maintain the mechanical strength, and 0.5 mm or more is sufficient. As for the glass material, it is preferable that the amount of ions eluted from the glass is small, and alkali-free glass is preferable. In addition, SiO ２ Soda lime glass coated with a barrier coating such as the above is also commercially available and can be used.

[0080] (Anode) The material used for the anode is preferably one that can efficiently inject holes into the organic layer. Furthermore, it is preferably transparent or semi-transparent in order to extract light. Examples of materials used 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 alone, or multiple materials may be stacked or mixed together.

[0081] (Cathode) The material used for the cathode is not particularly limited as long as it 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, as well as alloys and multilayer laminates 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 light-emitting efficiency, and magnesium and magnesium are more preferred because they facilitate electron injection into the electron transport layer and the electron injection layer.

[0082] (Protective Layer) For cathode protection, 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 thereof include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, alloys using these metals, inorganic substances such as silica, titania, and silicon nitride, and organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon polymer compounds. Compounds represented by general formula (1) can also be used as capping materials. However, when the organic EL element has a device structure in which light is extracted from the cathode side (top emission structure), it is preferable that the capping material be optically transparent in the visible light region.

[0083] (Hole injection layer) The hole injection layer is a layer inserted between the anode and the hole transport layer. The hole injection layer may be a single layer or a laminate of multiple layers. The presence of a hole injection layer between the hole transport layer and the anode is preferable because it not only enables lower voltage driving and improves durability and lifespan, but also improves the carrier balance of the element and the luminous efficiency.

[0084] Known materials can be used for the hole injection layer. Examples include heterocyclic compounds such as benzidine derivatives, starburst arylamine materials, triarylamine derivatives, biscarbazole derivatives, pyrazoline derivatives, stilbene compounds, fluorene compounds, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives, and polymer materials such as polycarbonates and styrene derivatives having the above-mentioned monomers in their side chains, polythiophenes, polyanilines, polyfluorenes, polyvinylcarbazoles, and polysilanes. From the viewpoint of smoothly injecting and transporting holes from the anode to the hole transport layer, benzidine derivatives, starburst arylamine materials, and fluorene compounds are more preferably used.

[0085] These materials may be used alone or in combination of two or more materials. Furthermore, a hole injection layer may be formed by laminating a plurality of materials. Furthermore, it is more preferable that the hole injection layer be composed solely of an acceptor compound or that the hole injection material be doped with an acceptor compound, since the above-described effects are more pronounced. The acceptor compound is a material that forms a charge-transfer complex with the adjacent hole transport layer when used as a single layer film, or with the material constituting the hole injection layer when used as a doped film. The use of such a material improves the conductivity of the hole injection layer, further contributing to a reduction in the driving voltage of the device and further improving the luminous efficiency and durability.

[0086] Known materials can be used as the acceptor compound. Examples include metal chlorides, metal oxides such as molybdenum oxide, charge-transfer complexes, organic compounds having a nitro group, a cyano group, a halogen, or a 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 vapor-deposit, and therefore the above-mentioned effects can be easily obtained. Whether the hole injection layer is composed of an acceptor compound alone or is doped with an acceptor compound, the hole injection layer may be a single layer or may be composed of multiple layers stacked together.

[0087] (Hole Transport Layer) The hole transport layer is a layer that transports holes injected from the anode to the light emitting layer. The hole transport layer may be a single layer or may be configured by laminating multiple layers.

[0088] Materials used for the hole transport layer include those exemplified as materials used for 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.

[0089] (Light-Emitting Layer) The light-emitting layer may be a single layer or multiple layers, each formed from light-emitting materials (host material, dopant material). This may be a mixture of a host material and a dopant material, a host material alone, or a mixture of two host materials and one dopant material. That is, in the organic EL device according to the embodiment of the present invention, only the host material or the dopant material may emit light in each light-emitting layer, 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 composed of a mixture of a host material and a 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 entirely or partially in the host material. The dopant material may be laminated or dispersed. The dopant material can control the emitted color. The amount of the dopant material is preferably 30% by weight or less, more preferably 20% by weight or less, based on the host material, from the viewpoint of suppressing concentration quenching. The doping method can be a co-evaporation method with the host material, or the dopant material may be mixed with the host material in advance and then evaporated simultaneously.

[0090] Known light-emitting materials can be used, including, for example, fused ring derivatives of anthracene, pyrene, and the like, which are known as light-emitting bodies, metal-chelated oxinoid compounds such as tris(8-quinolinolato)aluminum, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, and polymers such as polyphenylenevinylene derivatives, polyparaphenylene derivatives, and polythiophene derivatives.

[0091] The host material contained in the light-emitting material does not need to be limited to only one compound, and a mixture of multiple compounds may be used. Furthermore, the compounds may be laminated. Known materials can be used as the host material. Examples of the host material include, but are not limited to, compounds having a condensed aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and indene, and derivatives thereof; aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine; metal chelated oxinoid compounds such as tris(8-quinolinato)aluminum(III); bisstyryl derivatives such as distyrylbenzene derivatives; Examples of the host 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. Among these, preferred examples of the host used when the light-emitting layer exhibits triplet emission (phosphorescence emission) include metal-chelated oxinoid compounds, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, and triphenylene derivatives.

[0092] Examples of dopant materials contained in the light-emitting material include compounds having an aryl ring and derivatives thereof, compounds having a heteroaryl ring and derivatives thereof, distyrylbenzene derivatives, aminostyryl derivatives, aromatic acetylene derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyrromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, coumarin derivatives, azole derivatives, metal complexes thereof, aromatic amine derivatives, and compounds represented by the following general formula (3). Among these, dopants containing a diamine skeleton and dopants containing a fluoranthene skeleton can further improve luminous efficiency, and compounds represented by the following general formula (3) can further improve luminous efficiency and durable life.

[0093]

[0094] In general formula (3), ring Za, ring Zb, and ring Zc are each independently a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms or a substituted or unsubstituted heteroaryl ring having 5 to 30 ring atoms. Ring Za, ring Zb, and ring Zc are each preferably independently a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms. Z １ and Z ２ are each independently an oxygen atom, NRa (a nitrogen atom having a substituent Ra), or a sulfur atom, and Z １ is NRa, it may or may not be bonded to ring Za or ring Zb to form a ring, ２ When NRa is NRa, it may or may not be bonded to the Zb ring or the Zc ring to form a ring. Each Ra is independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms. Z １ and Z ２are all NRa, and Ra is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms. Y is a boron atom, a phosphorus atom, SiRb (a silicon atom having a substituent Rb), P=O, or P=S. Rb is each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms. Y is preferably a boron atom.

[0095] In all of the above groups, the substituent when substituted is preferably an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, a halogen atom, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, or an oxo group. These substituents may further be substituted with the above-mentioned substituents.

[0096] Examples of the alkyl group, aryl group, heteroaryl group and halogen atom include those exemplified as the substituents in general formula (1).

[0097] The cycloalkyl group refers to a saturated alicyclic hydrocarbon group, such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, or an adamantyl group, which may or may not have a substituent. The number of ring carbon atoms is not particularly limited, but is preferably in the range of 3 to 20.

[0098] The heterocyclic group refers to an aliphatic ring having atoms other than carbon atoms in the ring, such as a pyran ring, a piperidine ring, or a cyclic amide, which may or may not have a substituent. The number of ring atoms is not particularly limited, but is preferably in the range of 3 to 20.

[0099] The alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, or a butadienyl group, which may or may not have a substituent. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0100] The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group, or a cyclohexenyl group, which may or may not have a substituent.

[0101] The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, which may or may not have a substituent. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0102] Furthermore, in a substituted phenyl group, when two adjacent carbon atoms in the phenyl group each have a substituent, the substituents may together form a ring structure. Depending on the structure, the resulting group may fall into one or more of the categories of a "substituted phenyl group," an "aryl group having a structure in which two or more rings are fused," and a "heteroaryl group having a structure in which two or more rings are fused."

[0103] An alkylthio group is an alkoxy group in which the oxygen atom of the ether bond is replaced with a sulfur atom. The alkylthio group may or may not have a substituent. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0104] The aryl ether group refers to a functional group in which an aromatic hydrocarbon group is bonded via an ether bond, such as a phenoxy group, and may or may not have a substituent. The number of carbon atoms in the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

[0105] The aryl thioether group refers to a functional group in which the oxygen atom of the ether bond of an aryl ether group is substituted with a sulfur atom, and may or may not have a substituent. The number of carbon atoms in the aryl thioether group is not particularly limited, but is preferably in the range of 6 to 40.

[0106] The acyl group refers to a functional group in which an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heteroaryl group is bonded via a carbonyl group, such as an acetyl group, a propionyl group, a benzoyl group, or an acrylyl group, and may or may not have a substituent. The number of carbon atoms in the acyl group is not particularly limited, but is preferably 2 to 40, more preferably 2 to 30.

[0107] The ester group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or the like is bonded via an ester bond, and may or may not have a substituent. The number of carbon atoms in the ester group is not particularly limited, but is preferably in the range of 1 to 20. More specific examples include methyl ester groups such as a methoxycarbonyl group, ethyl ester groups such as an ethoxycarbonyl group, propyl ester groups such as a propoxycarbonyl group, butyl ester groups such as a butoxycarbonyl group, isopropyl ester groups such as an isopropoxymethoxycarbonyl group, hexyl ester groups such as a hexyloxycarbonyl group, and phenyl ester groups such as a phenoxycarbonyl group.

[0108] The amide group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or the like is bonded via an amide bond, and may or may not have a substituent. The number of carbon atoms in the amide group is not particularly limited, but is preferably in the range of 1 to 20. More specific examples include a methylamide group, an ethylamide group, a propylamide group, a butylamide group, an isopropylamide group, a hexylamide group, and a phenylamide group.

[0109] The sulfonyl group is, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc., which is —S(═O) ２The sulfonyl group represents a functional group bonded via a - bond, and may or may not have a substituent. The number of carbon atoms in the sulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.

[0110] The sulfonate ester group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or the like is bonded via a sulfonate ester bond, and may or may not have a substituent. Here, the sulfonate ester bond refers to a group in which the carbonyl part of the ester bond, i.e., —C(═O)—, is bonded to the sulfonyl part, i.e., —S(═O) ２ The number of carbon atoms in the sulfonate ester group is not particularly limited, but is preferably in the range of 1 to 20.

[0111] The sulfonamide group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, or the like is bonded via a sulfonamide bond, and may or may not have a substituent. Here, the sulfonamide bond refers to a group in which the carbonyl part of the ester bond, i.e., —C(═O)—, is bonded to the sulfonyl part, i.e., —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.

[0112] The amino group may or may not have a substituent. The number of carbon atoms in the amino group is not particularly limited, but is preferably in the range of 2 to 50, more preferably 6 to 40, and particularly preferably 6 to 30.

[0113] The silyl group refers to a functional group to which a substituted or unsubstituted silicon atom is bonded, and examples thereof include alkylsilyl groups such as trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, propyldimethylsilyl, and vinyldimethylsilyl, and arylsilyl groups such as phenyldimethylsilyl, tert-butyldiphenylsilyl, triphenylsilyl, and trinaphthylsilyl. The silyl group may or may not have a substituent. The number of carbon atoms in the silyl group is not particularly limited, but is preferably in the range of 1 to 30.

[0114] The siloxanyl group refers to a silicon compound group bonded via an ether bond, such as a trimethylsiloxanyl group, etc. The siloxanyl group may or may not have a substituent.

[0115] The boryl group may or may not have a substituent.

[0116] Examples of the compound represented by general formula (3) include the following.

[0117]

[0118] In the organic EL device according to the embodiment of the present invention, the light-emitting layer preferably contains a triplet light-emitting material.

[0119] The dopant used when the light-emitting layer emits triplet light (phosphorescence) 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, the dopant 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. Specifically, tris(2-phenylpyridyl)iridium complexes, tris{2-(2-thiophenyl)pyridyl}iridium complexes, tris{2-(2-benzothiophenyl)pyridyl}iridium complexes, tris(2-phenylbenzothiazole)iridium complexes, tris(2-phenylbenzoxazole)iridium complexes, trisbenzoquinolineiridium complexes, bis(2-phenylpyridyl)(acetylacetonate)iridium complexes, bis{2-(2-thiophenyl)pyridyl}iridium complexes, bis{2-(2-benzothiophenyl)pyridyl}(acetylacetonate)iridium complexes, bis(2-phenylbenzothiazole)(acetylacetonate)iridium complexes, bis(2-phenylbenzothiazole)(acetylacetonate)iridium complexes, Examples of suitable dopants include a bis(2-(2,4-difluorophenyl)pyridyl)(acetylacetonate)iridium complex, a bisbenzoquinoline(acetylacetonate)iridium complex, a bis{2-(2,4-difluorophenyl)pyridyl}(acetylacetonate)iridium complex, a tetraethylporphyrin platinum complex, a {tris(cenoyltrifluoroacetone)mono(1,10-phenanthroline)}europium complex, a {tris(cenoyltrifluoroacetone)mono(4,7-diphenyl-1,10-phenanthroline)}europium complex, a {tris(1,3-diphenyl-1,3-propanedione)mono(1,10-phenanthroline)}europium complex, and a trisacetylacetone terbium complex. Phosphorescent dopants such as those described in JP-A-2009-130141 are also suitable. Iridium complexes or platinum complexes are preferred, as they can further improve luminous efficiency.

[0120] The triplet light-emitting materials used as dopant materials may each be contained alone in the light-emitting layer, or two or more of them may be mixed together. When two or more triplet light-emitting materials are used, the total weight of the dopant materials is preferably 30% by weight or less, more preferably 20% by weight or less, based on the host material.

[0121] Preferred hosts and dopants in triplet light-emitting systems are not particularly limited, but specific examples include the following.

[0122]

[0123]

[0124] It is also preferable that the light-emitting layer contains a thermally activated delayed fluorescent material. Thermally activated delayed fluorescence is discussed on pages 87 to 103 of "State-of-the-art Organic EL" (edited by Adachi Chinaya and Fujimoto Hiroshi, published by CMC Publishing). This document explains that by bringing the energy levels of the excited singlet state and the excited triplet state of a fluorescent material close to each other, reverse energy transfer from the excited triplet state, which normally has a low transition probability, to the excited singlet state occurs with high efficiency, resulting in the expression of thermally activated delayed fluorescence (TADF). Furthermore, Figure 5 in this document explains the mechanism by which delayed fluorescence occurs. The emission of delayed fluorescence can be confirmed by transient PL (Photo Luminescence) measurement.

[0125] Thermally activated delayed fluorescence materials are also commonly referred to as TADF materials. Thermally activated delayed fluorescence materials may be materials that exhibit thermally activated delayed fluorescence using a single material, or may be materials that exhibit thermally activated delayed fluorescence using multiple materials. When multiple materials are used, they may be used as a mixture, or layers made of each material may be stacked. Known materials can be used as thermally activated delayed fluorescence materials. Examples include, but are not limited to, benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indolocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, and oxadiazole derivatives.

[0126] It is preferable that a device containing a TADF material in its light-emitting layer further contains a fluorescent dopant in the light-emitting layer, because the TADF material converts triplet excitons into singlet excitons, and the fluorescent dopant accepts the singlet excitons, thereby achieving higher luminous efficiency and longer durability.

[0127] (Electron Transport Layer) In the present invention, the electron transport layer is a layer into which electrons are injected from the cathode and which further transports the electrons. It is desirable for the electron transport layer to have high electron injection efficiency and efficiently transport the injected electrons. Therefore, it is preferable that the material constituting the electron transport layer has high electron affinity, high electron mobility, excellent stability, and is unlikely to generate impurities that become traps during production and use. In particular, when a thick film is laminated, low-molecular-weight compounds are prone to deterioration of film quality due to crystallization, etc., so in order to maintain stable film quality, compounds with a molecular weight of 400 or more are preferred. However, considering the balance between hole and electron transport, if the electron transport layer mainly plays a role in efficiently preventing holes from the anode from flowing to the cathode without recombining, even if the electron transport layer is composed of a material with a relatively low electron transport capacity, the effect of improving luminous efficiency will be equivalent to that of a material with a high electron transport capacity. Therefore, the electron transport layer in the present invention also includes a hole blocking layer that can efficiently block the movement of holes, and the hole blocking layer and the electron transport layer may be formed by a single material or by laminating a plurality of materials.

[0128] Known materials can be used as the electron transport material for the electron transport layer. Examples include condensed polycyclic aromatic derivatives, styryl aromatic ring derivatives, quinone derivatives, phosphorus oxide derivatives, quinolinol complexes, benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes, and various metal complexes such as flavonol metal complexes. Compounds containing an electron-accepting nitrogen atom and an element selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus are preferably used because they can reduce the driving voltage and achieve more efficient light emission.

[0129] The electron-accepting nitrogen referred to here refers to a nitrogen atom that forms a multiple bond with an adjacent atom. Because the nitrogen atom has high electronegativity, the multiple bond has electron-accepting properties. Therefore, aromatic heterocycles containing electron-accepting nitrogen have high electron affinity. Electron-transporting materials containing electron-accepting nitrogen readily accept electrons from a cathode with high electron affinity, enabling operation at lower voltages. Furthermore, the supply of electrons to the light-emitting layer increases, increasing the recombination probability, further improving luminous efficiency.

[0130] Examples of heteroaryl rings containing an electron-accepting nitrogen include a triazine ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a quinoline ring, a quinoxaline ring, a quinazoline ring, a naphthyridine ring, a pyrimidopyrimidine ring, a benzoquinoline ring, a phenanthroline ring, an imidazole ring, an oxazole ring, an oxadiazole ring, a triazole ring, a thiazole ring, a thiadiazole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, and a phenanthroimidazole ring.

[0131] Examples of compounds having these heteroaryl ring structures include pyridine derivatives, triazine derivatives, quinazoline derivatives, pyrimidine derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives, and naphthyridine derivatives. Among these, imidazole derivatives, triazole derivatives, triazine derivatives, pyrimidine derivatives, phenanthroline derivatives, benzoquinoline derivatives, bipyridine derivatives, terpyridine derivatives, and naphthyridine derivatives are preferably used from the viewpoint of electron transport ability.

[0132] Furthermore, when these derivatives have a condensed polycyclic aromatic skeleton, the glass transition temperature is improved, the electron mobility is increased, and the driving voltage of the organic EL device can be further reduced, which is preferable. Furthermore, in consideration of further improving the durability life of the device, ease of synthesis, and ease of availability of raw materials, it is more preferable that the condensed polycyclic aromatic skeleton is a fluoranthene skeleton, an anthracene skeleton, a pyrene skeleton, or a phenanthroline skeleton.

[0133] Preferred electron transport materials are not particularly limited, but specific examples include the following.

[0134]

[0135]

[0136] The compound represented by the general formula (1) is also preferred because it has high electron transporting properties and exhibits excellent properties as an electron transport layer.

[0137] The above electron transporting materials may be used alone, or two or more of the above electron transporting materials may be mixed and used, or one or more other electron transporting materials may be mixed with the above electron transporting materials and used.

[0138] The electron transport layer may contain a donor material. Here, the donor material is a compound that improves the electron injection barrier, thereby facilitating electron injection from the cathode or the electron injection layer into the electron transport layer, and further improving the electrical conductivity of the electron transport layer.

[0139] The donor material preferably contains an alkali metal atom, an alkaline earth metal atom, or a rare earth metal atom from the viewpoint of a low work function and improved electron transport properties, and more preferably contains an alkali metal atom, a rare earth metal atom, or a copper group atom from the viewpoint of further reducing the driving voltage of the organic EL device.

[0140] In addition, the donor material is preferably in the form of an inorganic salt or a complex of a metal and an organic substance rather than a simple metal, because it can be easily vapor-deposited in a vacuum and is easy to handle. Furthermore, a complex of a metal and an organic substance is more preferable, because it facilitates handling in the atmosphere and makes it easier to adjust the addition concentration. Examples of inorganic salts include oxides, nitrides, fluorides, and carbonates. Preferred examples of the organic substance in the complex with the organic substance include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole. Among these, a complex of an alkali metal and an organic substance is preferred from the viewpoint of further reducing the driving voltage of the organic EL device. Furthermore, a complex of lithium and an organic substance is more preferred from the viewpoints of ease of synthesis and thermal stability, and lithium quinolinol (Liq), which is relatively inexpensive and available, is particularly preferred.

[0141] The ionization potential of the electron transport layer is not particularly limited, but is preferably from 5.6 eV to 8.0 eV, more preferably from 5.6 eV to 7.0 eV.

[0142] The method for forming each of the layers constituting the organic EL element is not particularly limited, and may be resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, coating, or the like. However, resistance heating evaporation or electron beam evaporation is usually preferred in terms of element characteristics.

[0143] (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 for the purpose of assisting the injection of electrons from the cathode to the electron transport layer. In this case, 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.

[0144] In addition, inorganic insulating or semiconducting materials can be used for the electron injection layer, and known materials can be used. By using these materials, it is possible to suppress short circuits in the organic EL element and improve the electron injection properties.

[0145] Such an insulator 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.

[0146] Furthermore, a complex of an organic substance and a metal can also be suitably used. When a complex of an organic substance and a metal is used in the electron injection layer, the film thickness can be easily adjusted. Preferred examples of the organic substance in the organometallic complex include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole.

[0147] A layer containing a compound represented by general formula (1) also has high electron injection properties and is therefore preferred because it exhibits excellent properties as an electron injection layer. Furthermore, the electron injection layer preferably contains a compound represented by general formula (1) and an alkali metal atom, a rare earth metal atom, or a copper group atom. In this case, the driving voltage can be further reduced and the durability life can be further improved.

[0148] (Charge Generation Layer) The charge generation layer in the present invention generally comprises a double layer, and specifically, can be used as a pn junction charge generation layer comprising an n-type charge generation layer and a p-type charge generation layer. When a voltage is applied to the organic EL element, the pn junction charge generation layer generates charges or separates the charges into holes and electrons, and injects these holes and electrons into the light-emitting layer via the hole transport layer and electron transport layer. Specifically, it functions as an intermediate charge generation layer in an organic EL element in which light-emitting layers are stacked. 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 an organic EL element in which multiple light-emitting layers are stacked can be further improved, the driving voltage can be reduced, and the durability of the element can be further improved.

[0149] The n-type charge generating layer comprises an n-type dopant and a host, and conventional materials can be used for these. For example, an alkali metal, an alkaline earth metal, or a rare earth metal can be used as the n-type dopant. Furthermore, a compound having a nitrogen-containing aromatic heterocycle, such as a phenanthroline derivative or an oligopyridine derivative, can be used as the host. In particular, the compound represented by general formula (1) and a phenanthroline derivative are preferred because they exhibit excellent properties as hosts for the n-type charge generating layer.

[0150] In one embodiment of the charge generating layer, it is preferable to further contain a phenanthroline derivative in addition to the compound represented by formula (1). Examples of the phenanthroline derivative include the following compounds.

[0151]

[0152] In one embodiment of the charge generating layer, in addition to the compound represented by general formula (1), it is preferable that the charge generating layer further contains an alkali metal atom, a copper group atom, or a rare earth metal atom. As the alkali metal atom, Li is particularly preferred. As the copper group atom, Ag is particularly preferred. As the rare earth metal atom, Yb is particularly preferred.

[0153] As one embodiment of the charge generating layer, a structure containing a phenanthroline derivative and an alkali metal atom, a copper group atom or a rare earth metal atom in addition to the compound represented by general formula (1) is also preferred.

[0154] The p-type charge generation layer is composed of a p-type dopant and a host, and conventional materials can be used for these. For example, p-type dopants include tetrafluorene-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), tetracyanoquinodimethane derivatives, radialene derivatives, iodine, and FeCl. ３ , FeF ３ , SbCl ５ The p-type dopant is preferably a radialene derivative, and the host is preferably an arylamine derivative.

[0155] Specific examples of preferable p-type dopants include the following compounds.

[0156]

[0157] The thickness of the organic layer is not limited because it depends on the resistance value of the light-emitting substance, but is preferably 1 to 1,000 nm. The thickness of each of the light-emitting layer, electron transport layer, and hole transport layer is preferably 1 nm to 200 nm, more preferably 5 nm to 100 nm.

[0158] The organic EL element according to the embodiment of the present invention has a function of converting electrical energy into light. While direct current is primarily used as the electrical energy, pulsed current or alternating current can also be used. While there are no particular limitations on the current and voltage values, they should be selected so as to obtain maximum brightness with as little energy as possible, taking into consideration the power consumption and lifespan of the element.

[0159] The organic EL element according to the embodiment of the present invention is suitably used as a display device such as a matrix and / or segment display, and also as a display device having an optical sensor, which is being considered for thinning and weight reduction.

[0160] The organic EL element according to the embodiment of the present invention is also preferably used as a backlight for various devices. Backlights are primarily used for the purpose of improving the visibility of display devices such as non-self-luminous displays, and are used in liquid crystal displays, clocks, audio equipment, automobile panels, display boards, signs, etc. In particular, the organic EL element of the present invention is preferably used as a backlight for liquid crystal displays, particularly for personal computers, which are being considered for thinning, and can provide a backlight that is thinner and lighter than conventional ones.

[0161] The organic EL element according to the embodiment of the present invention is also preferably used in various lighting devices. The organic EL element according to the embodiment of the present invention can achieve both high luminous efficiency and high color purity, and can also be made thin and lightweight, thereby realizing a lighting device that combines low power consumption, vivid luminous color, and high designability.

[0162] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0163] Synthesis Example: Synthesis of Compound 1 A mixed solution of 2.7 g of 1-pyreneboronic acid, 3.6 g of raw material A, 14.0 ml of 1.0 M aqueous sodium carbonate solution, 75 mg of bis(triphenylphosphine)dichloropalladium, and 100 ml of THF was heated and stirred at 80°C for 5 hours under a nitrogen stream. After cooling to room temperature, water was added, and the mixture was filtered, washed with methanol, and dried under vacuum. The resulting solid was recrystallized from toluene and then dried under vacuum to obtain 3.0 g of Compound 1.

[0164] The obtained compound 1 was subjected to 1×10 －３ Sublimation purification was carried out at about 330° C. under a pressure of 100 Pa. The HPLC purity (area % at a measurement wavelength of 254 nm) of Compound 1 before and after sublimation purification was 99.9%.

[0165] After sublimation purification, mass spectrometry (MS) analysis and １ The structure of Compound 1 was identified by H-NMR analysis. The analytical results are shown below. MS (m / z): 533 [M+H] ＋ １ H-NMR (400MHz, CDCl３ -d ６ ) δ: 8.98 (d, J = 9.2Hz, 1H), 8.49 (d, J = 7.6Hz, 1H), 8.42 (d, J = 8.0Hz , 1H), 8.34 (d, J = 8.4Hz, 1H), 8.30 (d, J = 7.6Hz, 1H), 8.23 ​​(d, J = 7.6H z, 2H), 8.18-8.13 (m, 4H), 8.04 (t, J=7.6Hz, 1H), 7.90 (dd, J=8.8Hz , 2H), 7.78 (d, J=8.8Hz, 1H), 7.54-7.40 (m, 3H), 7.29-7.16 (m, 6H).

[0166]

[0167] Next, the evaluation methods used in each example will be described.

[0168] (Driving voltage) The elements obtained in Examples 1 to 30, 101 to 108 and Comparative Examples 1 to 12 were each driven at a current of 10 mA / cm ２ The device was then driven with a direct current at a current density of 10 mA / cm under a temperature of 70°C, and the initial drive voltage was measured. ２ The voltage was measured after driving the device with a direct current for 100 hours at 1000 V, and the amount of voltage increase from the initial driving voltage was calculated.

[0169] The organic EL devices obtained in Examples 31 to 91, 109 to 124 and Comparative Examples 13 to 36 were each tested to obtain a luminance of 1000 cd / m ２ The device was then turned on at a current density of 10 mA / cm at room temperature, and the initial driving voltage was measured. ２ The voltage was measured after driving the device at a constant current of 100 hours at 100 volts, and the amount of voltage increase from the initial driving voltage was calculated.

[0170] The smaller the initial driving voltage, the lower the driving voltage, and therefore the better the light emitting efficiency (brightness / power). Also, the smaller the voltage rise, the better the durability.

[0171] (External Quantum Efficiency) The organic EL devices obtained in Examples 31 to 91, 109 to 124 and Comparative Examples 13 to 36 were each subjected to a current density of 10 mA / cm ２ The external quantum efficiency was measured and the luminous efficiency was evaluated. The higher the external quantum efficiency, the better the luminous efficiency can be evaluated.

[0172] (Durability) The organic EL devices obtained in Examples 31 to 91, 109 to 124 and Comparative Examples 13 to 36 were subjected to a current of 10 mA / cm ２ The time required for the brightness to decrease by 20% from the initial brightness was measured and used as the durability.

[0173] Example 1 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 125 nm ITO transparent conductive film had been deposited as an anode was cut into a size of 38 mm x 46 mm and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" (registered trademark) 56 (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and then washed with ultrapure water. This substrate was subjected to UV-ozone treatment for 1 hour immediately before fabricating the element, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was adjusted to 5 x 10. －４ The chamber was evacuated to a pressure of 100 Pa or less. Compound 1 and the dopant metal element Yb were evaporated to a thickness of 100 nm by resistance heating, with the evaporation rate ratio of Compound 1:Yb = 9:1, to form a layer with a weight ratio of 9:1. Aluminum was then evaporated to a thickness of 60 nm to form a cathode, and a single charge element measuring 5 mm x 5 mm was fabricated. The film thickness referred to here is the value displayed on a quartz crystal oscillation film thickness monitor, and is the same in other examples and comparative examples.

[0174] When this single charge device was evaluated by the above-mentioned method, the initial driving voltage was 0.083 V, and the voltage increase after driving at 70° C. for 100 hours was 0.021 V.

[0175] Examples 2 to 30, 101 to 108, Comparative Examples 1 to 12 Single-charge elements were prepared in the same manner as in Example 1, except that the compounds, metal elements, and vapor deposition rate ratios of the compounds and metal elements used were changed as shown in Table 1. The results of each Example, Comparative Example, and Reference Example are shown in Tables 1-1 and 1-2. Compounds 1 to 12, compounds 14 to 19, compounds U to Z, and compounds Q to T are the compounds shown below.

[0176]

[0177]

[0178]

[0179]

[0180]

[0181]

[0182] Example 31 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited as an anode was cut into a size of 38 mm x 46 mm and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" 56 (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and then washed with ultrapure water. This substrate was subjected to UV-ozone treatment for 1 hour immediately before fabricating the element, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was adjusted to 5 x 10 －４ The chamber was evacuated to a pressure of 100 Pa or less. Using a resistance heating method, p-D1 was first vapor-deposited to a thickness of 5 nm as a hole injection layer, followed by vapor-depositing HT-1 at a thickness of 50 nm as a hole transport layer. Next, a mixed layer of host material H-1 and dopant material D-1 was vapor-deposited to a thickness of 20 nm as an emitting layer, with a doping concentration of 5 wt %. Next, ET-1 and 2E-1 were vapor-deposited to a thickness of 35 nm as an electron transport layer, with a vapor deposition rate ratio of ET-1 to 2E-1 = 1:1. Next, compound 1 and the metal element Yb as a dopant were vapor-deposited to a thickness of 10 nm as an electron injection layer, with a vapor deposition rate ratio of compound 1:Yb = 9:1. Subsequently, aluminum was vapor-deposited to a thickness of 60 nm to form a cathode, and a 5 mm x 5 mm square organic EL device was fabricated.

[0183] When this organic EL device was evaluated by the above-mentioned method, the initial driving voltage was 4.46 V, the external quantum efficiency (luminous efficiency) was 4.95%, the durability life was 830 hours, and the voltage increase after driving for 100 hours at room temperature was 0.034 V. Note that p-D1, HT-1, H-1, D-1, ET-1, and 2E-1 are the compounds shown below.

[0184]

[0185] Examples 32 to 60, 109 to 116, Comparative Examples 13 to 24 Organic EL devices were prepared in the same manner as in Example 31, except that the compounds, metal elements, and vapor deposition rate ratios of the compounds and metal elements used were changed as shown in Table 2. The results of each of the Examples and Comparative Examples are shown in Tables 2-1 and 2-2.

[0186]

[0187]

[0188] Example 61 A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω / □, sputtered product) on which a 165 nm ITO transparent conductive film had been deposited as an anode was cut into 38 mm × 46 mm pieces and etched. The resulting substrate was ultrasonically cleaned for 15 minutes using "Semicoclean" 56 (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and then washed with ultrapure water. This substrate was subjected to UV-ozone treatment for 1 hour immediately before fabricating the element, and then placed in a vacuum deposition apparatus, and the degree of vacuum in the apparatus was adjusted to 5 × 10. －４ The chamber was evacuated to a pressure of 100 Pa or less. First, p-D1 was vapor-deposited to a thickness of 5 nm as a hole injection layer by resistance heating. Next, an emitting unit (first emitting unit) consisting of a hole transport layer, an emitting layer, and an electron transport layer was formed on the hole injection layer.

[0189] Specifically, HT-1 was deposited to a thickness of 50 nm as a hole transport layer, and then a mixed layer of host material H-1 and dopant material D-1 was deposited to a thickness of 20 nm as an emitting layer so that the doping concentration was 5 wt %. Next, ET-1 and 2E-1 were deposited to a thickness of 35 nm as an electron transport layer so that the deposition rate ratio of ET-1 to 2E-1 was 1:1.

[0190] On the first light-emitting unit, Compound 1 and a metal element Yb serving as a dopant were deposited to a thickness of 10 nm as an N-type charge generation layer so that the deposition rate ratio of Compound 1:Yb was 9:1, and then p-D1 was deposited to a thickness of 10 nm as a P-type charge generation layer.

[0191] Following the charge generation layer, a second light-emitting unit was formed in the same manner as the first light-emitting unit. Then, as an electron injection layer, Compound 1 and a metal element Yb serving as a dopant were vapor-deposited to a thickness of 10 nm at a vapor deposition rate ratio of Compound 1:Yb=9:1, and subsequently, aluminum was vapor-deposited to a thickness of 60 nm to form a cathode, thereby producing an organic EL device having a size of 5 mm × 5 mm.

[0192] When this organic EL element was evaluated by the above-mentioned method, the initial driving voltage was 8.85 V, the external quantum efficiency (luminous efficiency) was 10.00%, the durability life was 1850 hours, and the voltage increase after driving for 100 hours at room temperature was 0.038 V.

[0193] Examples 62 to 91, 117 to 124, Comparative Examples 25 to 36 Organic EL devices were fabricated in the same manner as in Example 61, except that the compounds used and the deposition rate ratios of the compounds and metal elements were changed as shown in Table 3. The results of each Example and Comparative Example are shown in Tables 3-1 and 3-2. In Example 91, Compound 1 and Compound 13 were co-deposited as compounds used in the N-type charge generation layer at a deposition rate ratio of 1:1. Compound 13 is the compound shown below.

[0194]

[0195]

[0196]

[0197] Examples 1 to 30 show the results of single-charge devices using a compound represented by general formula (1) together with the alkali metal element Li and the rare earth metal element Yb. On the other hand, Comparative Examples 1 to 12 show the results of light-emitting devices using compounds U to Z, which are not compounds represented by general formula (1), together with the alkali metal element Li and the rare earth metal element Yb. Each Example had a lower initial driving voltage and a smaller increase in driving voltage compared to each Comparative Example. This is understood to be because compounds 1 to 12 represented by general formula (1) have higher film quality stability compared to compounds U to Z, and therefore have stronger coordination stability with alkali metal elements and rare earth metal elements, resulting in higher charge generation efficiency and electron transportability, thereby suppressing the increase in voltage during driving.

[0198] Furthermore, Examples 31 to 60 show the results of applying the organic layers used in Examples 1 to 30 to light-emitting devices. On the other hand, Comparative Examples 13 to 24 show the results of applying the organic layers used in Comparative Examples 1 to 12 to light-emitting devices. Compared to the respective Comparative Examples, each Example had a lower driving voltage, higher external quantum efficiency, improved durability, and a smaller increase in driving voltage. This shows that, similar to the results for the single-charge element, the compound represented by general formula (1) forms an efficient, more stable light-emitting device with a smaller increase in driving voltage.

[0199] Furthermore, Examples 61 to 91 show the results of applying the light-emitting elements used in Examples 31 to 60 to tandem light-emitting elements. On the other hand, Comparative Examples 25 to 36 show the results of applying the light-emitting elements used in Comparative Examples 13 to 24 to tandem light-emitting elements. Compared to the respective Comparative Examples, each Example had a lower driving voltage, higher external quantum efficiency, improved durability, and less increase in driving voltage. This shows that, similar to the results of the light-emitting elements used in Examples 31 to 60 and Comparative Examples 13 to 24, the compound represented by general formula (1) forms an efficient, more stable tandem light-emitting element with less increase in driving voltage.

Claims

1. A compound represented by the following general formula (1): (In general formula (1), L is a single bond, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group. A is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. B is a substituent represented by general formula (2) and is bonded to the phenanthroline skeleton in general formula (1) at the position marked * in general formula (2). L-A does not have the same structure as B.) (In general formula (2), R １ ~R ９ are each independently a hydrogen atom, a halogen atom, an alkyl group, or an unsubstituted phenyl group, and R １ ~R ９ do not bond to each other to form a ring.) 2. In the general formula (2), R １ ~R ９ The compound according to claim 1 , wherein is a hydrogen atom.

3. The compound according to claim 1, wherein in the general formula (1), L is a single bond or a substituted or unsubstituted arylene group.

4. The compound according to claim 1, wherein in the general formula (1), A is a substituted or unsubstituted aryl group having 10 or more ring atoms or a substituted or unsubstituted heteroaryl group having 10 or more ring atoms.

5. The compound according to claim 1, wherein in said general formula (1), A is a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolinyl group, or a substituted or unsubstituted phenanthrolinyl group, and when these are substituted, the substituent is an aryl group or a pyridyl group.

6. The compound according to claim 1, wherein in the general formula (1), L is a substituted or unsubstituted arylene group, and A is selected from the following groups: (* indicates the bonding position with L, and these groups may be substituted with an aryl group.) 7. A light-emitting device which emits light by electrical energy and which has at least an electron transport layer and a light-emitting layer between an anode and a cathode, and in which the electron transport layer contains the compound according to any one of claims 1 to 6.

8. The light-emitting device according to claim 7, wherein the electron transport layer further contains an alkali metal complex compound.

9. A light-emitting device which emits light by electrical energy and which has at least a charge-generating layer and a light-emitting layer between an anode and a cathode, and in which the charge-generating layer contains the compound according to any one of claims 1 to 6.

10. The light-emitting device according to claim 9, wherein the charge generating layer further contains a phenanthroline derivative.

11. The light-emitting device according to claim 9, wherein said charge generating layer further contains alkali metal atoms or rare earth metal atoms.

12. The light-emitting device according to claim 11, wherein the alkali metal atom is Li.

13. The light-emitting device according to claim 11, wherein the rare earth metal atom is Yb.

14. A light-emitting device which emits light by electrical energy and which has at least an electron-injecting layer and a light-emitting layer between an anode and a cathode, and in which the electron-injecting layer contains the compound according to any one of claims 1 to 6.

15. A display device comprising a light-emitting element containing the compound according to any one of claims 1 to 6.

16. A lighting device comprising a light-emitting element containing the compound according to any one of claims 1 to 6.

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