Compound, light-emitting element, display device, and lighting device

Abstract

The purpose of the present invention is to provide a light-emitting element having excellent luminous efficiency and durability life. The present invention is a compound represented by general formula (1). (In general formula (1), R1, R2, and R5 to R8 are each independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. And R3 and R4 each represents a carbon atom having a substituent. R3 and R4 may be bonded to each other. And L is an unsubstituted arylene group with the carbon atom number of 6-20. > # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a compound having a specific structure, and a light-emitting element, a display device, and a lighting device using the same. Background Art

[0002] Organic EL elements, which are light-emitting elements, have been used in displays of televisions and smartphones in recent years, and their practical application is steadily advancing. However, there are still many technical issues in existing organic EL elements. Among them, achieving both high-efficiency light emission and extending the life of organic EL elements has become a major issue.

[0003] As compounds for solving these problems, bipyridine derivatives having a bipyridine skeleton and substituted with specific aromatic and heteroaromatic groups (for example, refer to Patent Documents 1 to 3), bipyridine derivatives substituted with aromatic groups having a fluoranthene skeleton (refer to Patent Document 4), bipyridine derivatives having a phenanthroline skeleton (for example, refer to Patent Document 5), etc. have been developed so far.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Chinese Patent Application Publication No. 112724073

[0007] Patent Document 2: Chinese Patent Application Publication No. 112500330

[0008] Patent Document 3: International Publication No. 2013 / 141097

[0009] Patent Document 4: International Publication No. 2015 / 182547

[0010] Patent Document 5: Korean Patent No. 102052332 Summary of the invention

[0011] Problems to be solved by the invention

[0012] According to Patent Documents 1 to 5, bipyridine derivatives formed by connecting a fluoranthene skeleton, a specific aryl group, an arylene group or a heteroaryl group can improve the luminous efficiency and obtain an organic EL element that can be driven at a low voltage and has excellent durability. However, in recent years, the luminous efficiency and durability required of organic EL elements have become increasingly higher, requiring a technology that combines higher luminous efficiency and durable life.

[0013] In view of the above problems in the prior art, an object of the present invention is to provide a light-emitting element having excellent luminous efficiency and durable life.

[0014] Means for solving problems

[0015] In order to solve the above-mentioned problems, the present invention adopts the following configuration.

[0016] [1] A compound represented by the following general formula (1).

[0017] [Chemical formula 1]

[0018]

[0019] A compound represented by the following general formula (1).

[0020] In the general formula (1), R 1 , R 2 and R 5 ~R 8 are each independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. 3 and R 4 is a carbon atom having a substituent. 3 and R 4 They may be bonded to each other. L is an unsubstituted arylene group having 6 to 20 carbon atoms.

[0021] [2] The compound as described in [1], wherein in the general formula (1), R 1 , R 2 , R 5 and R 6 are hydrogen atoms respectively.

[0022] [3] The compound as described in [1] or [2], wherein in the general formula (1), R 7 is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

[0023] [4] The compound according to any one of [1] to [3], wherein in the general formula (1), R 3 With R 4 Connect with each other.

[0024] [5] A light-emitting element comprising at least an electron transport layer and a light-emitting layer between an anode and a cathode, and emitting light using electrical energy, wherein the electron transport layer contains the compound described in any one of [1] to [4].

[0025] [6] The light-emitting element as described in [5], wherein the electron transport layer further contains a complex of an alkali metal and an organic substance.

[0026] [7] A light-emitting element comprising at least a charge generation layer and a light-emitting layer between an anode and a cathode, and emitting light using electrical energy, wherein the charge generation layer contains the compound described in any one of [1] to [4].

[0027] [8] The light-emitting element according to [7], wherein the charge generating layer further contains a phenanthroline dimer.

[0028] [9] The light-emitting element described in [7] or [8], wherein the charge generation layer further contains alkali metal atoms or rare earth metal atoms.

[0029]

[10] The light-emitting element according to any one of [7] to [9], wherein the charge generation layer further contains an alkali metal atom, and the alkali metal atom is Li.

[0030]

[11] The light-emitting element according to any one of [7] to [9], wherein the charge generation layer further contains rare earth metal atoms, and the rare earth metal atoms are Yb.

[0031]

[12] A light-emitting element comprising at least an electron injection layer and a light-emitting layer between an anode and a cathode, and emitting light using electrical energy, wherein the electron injection layer contains the compound described in any one of [1] to [4].

[0032]

[13] The light-emitting element according to claim 12, wherein the electron injection layer further contains alkali metal atoms or rare earth metal atoms.

[0033]

[14] A display device comprising a light-emitting element containing the compound according to any one of [1] to [4].

[0034]

[15] A lighting device comprising a light-emitting element containing the compound described in any one of [1] to [4].

[0035] Effects of the Invention

[0036] According to the present invention, a light-emitting element having excellent luminous efficiency and durable life can be provided. DETAILED DESCRIPTION

[0037] Hereinafter, preferred embodiments of the compound, light-emitting element, display device, and lighting device of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with various modifications according to the purpose and application.

[0038] (Compound represented by general formula (1))

[0039] The compound according to the embodiment of the present invention is a compound represented by the general formula (1).

[0040] [Chemical formula 2]

[0041]

[0042] In the general formula (1), R 1 , R2 and R 5 ~R 8 are each independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. 3 and R 4 is a carbon atom having a substituent. 3 and R 4 They may be bonded to each other. L is an unsubstituted arylene group having 6 to 20 carbon atoms.

[0043] Here, the problems to be solved by the present invention will be described again in detail.

[0044] As conventional compounds containing nitrogen-containing aromatic heterocycles and polycyclic aromatic hydrocarbons, for example, Patent Documents 1 to 5 disclose compounds V, W, X, Y, and Z represented by the following formulae.

[0045] [Chemical formula 3]

[0046]

[0047] However, even when these compounds are used as materials for organic EL elements in electron injection layers, electron transport layers or charge generation layers, sufficient performance has not yet been obtained for the properties required in recent years. Therefore, compounds that can further improve performance in terms of luminous efficiency and durable life are required.

[0048] For example, heteroaryl derivatives composed of five consecutive pyridines and pyrimidines such as Compounds V and W, or compounds having three bipyridyl groups such as Compound X, have a problem of high crystallinity and reduced handling properties and film stability due to an excessively strong intermolecular hydrogen bonding network.

[0049] Compounds having bipyridyl and fluoranthene groups such as compound Y have high planarity and excessively high crystallinity due to the fluoranthene skeleton, resulting in low film stability, high driving voltage, and problems in luminous efficiency and long life.

[0050] In the 3,3'-bipyridine derivative such as compound Z, since the nitrogen atom of pyridine is not at the 2,2' position, there is a problem that the coordination of bipyridine to the metal atom is reduced, resulting in an increase in driving voltage.

[0051] The inventors of the present application have focused on the effects of bipyridyl groups and their linking groups in their improved research. Bipyridyl groups have large electron transport properties and are substituents with high coordination properties to metal atoms. L of the compound represented by the general formula (1) is an unsubstituted arylene group having 6 to 20 carbon atoms, so that the groups on both sides of L are easily conjugated. Therefore, the charge transport property of the compound becomes greater. In addition, since the number of carbon atoms in L is not too large, excessive crystallinity is suppressed, providing good film stability. Therefore, the driving voltage when the compound represented by the general formula (1) is used in a light-emitting element can be reduced, and the luminous efficiency and durable life can be improved.

[0052] In addition, the bipyridyl group has a high coordination property to the metal atom, so when the compound represented by the general formula (1) is used in a metal-doped layer in a light-emitting element, a stable layer can be formed. In particular, when the compound represented by the general formula (1) is used in an electron transport layer, an electron injection layer, or a charge generation layer, these layers show more stable and excellent performance.

[0053] Hereinafter, the compound represented by the general formula (1) will be described in detail.

[0054] In the general formula (1), R 1 , R 2 and R 5 ~R 8 Each is independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group and a substituted or unsubstituted heteroaryl group.

[0055] The hydrogen atom may be a deuterium atom. The same applies to hydrogen atoms contained in other groups.

[0056] The alkyl group represents, for example, a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, etc., which may or may not have a substituent. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 1 to 20, and more preferably in the range of 1 to 8, from the perspective of ease of acquisition and cost. The number of carbon atoms mentioned here also includes the number of carbon atoms contained in the substituent group bonded to the alkyl group, and the same applies to other substituent groups for which the number of carbon atoms is specified.

[0057] Alkoxy groups are groups formed by bonding an alkyl group such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy and oxygen, and they may or may not have a substituent. The number of carbon atoms in the alkoxy group is not particularly limited, but is generally 1 to 20, more preferably 1 to 8, from the perspective of ease of acquisition and cost.

[0058] The aryl group represents, for example, phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, anthracenyl, triphenylenyl, benzanthryl, The aromatic hydrocarbon groups include phenyl, pyrenyl, fluoranthenyl, triphenylene, benzofluoranthenyl, dibenzoanthryl, perylene, helicenyl and the like. They may or may not have a substituent. Among them, phenyl and biphenyl are preferred.

[0059] The heteroaryl group represents, for example, a cyclic aromatic group having one or more atoms other than carbon in the ring, such as pyridyl, furanyl, thienyl, quinolyl, isoquinolyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, naphthyridinyl, cinnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzothienyl, indolyl, dibenzofuranyl, dibenzothienyl, carbazolyl, benzocarbazolyl, carbolyl, indolecarbazolyl, benzofuranocarbazolyl, benzothiophenocarbazolyl, dihydroindenocarbazolyl, benzoquinolyl, acridinyl, dibenzoacridinyl, benzimidazolyl, imidazopyridinyl, benzoxazolyl, benzothiazolyl, and phenanthrolinyl. Among them, naphthyridinyl represents any one of 1,5-naphthyridinyl, 1,6-naphthyridinyl, 1,7-naphthyridinyl, 1,8-naphthyridinyl, 2,6-naphthyridinyl, and 2,7-naphthyridinyl. The heteroaryl group may or may not have a substituent. The number of ring atoms is not particularly limited, but is preferably 3 to 40, and more preferably 3 to 30.

[0060] Based on the ease of obtaining the compound, R 1 , R 2 , R 5 and R 6 In addition, from the viewpoint of improving the film stability and further improving the durability life of the light-emitting element, R 1 , R 2 , R 5 and R 6 are hydrogen atoms respectively.

[0061] R 7 Preferably, it is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. In this case, since the highly reactive 2-position in the bipyridine skeleton is substituted, the stability of the compound is improved. 7 More preferably, it is phenyl, tolyl, tert-butylphenyl, cyanophenyl, fluorophenyl or pyridyl. In this case, due to the effective metal orientation of the substituent, when the compound represented by general formula (1) is used in the metal doping layer, a more stable layer can be formed. Therefore, the driving voltage can be further reduced and the durability life can be improved. From the viewpoint of further improving the stability and durability life of the element, R 7More preferably, it is phenyl or tert-butylphenyl. 8 Preferably, R is a hydrogen atom or a phenyl group. 8 A hydrogen atom is more preferred.

[0062] In the general formula (1), R 3 and R 4 is a carbon atom having a substituent. 3 and R 4 Can be bonded to each other. 3 and R 4 Preferably, they are bonded to each other. In this case, by fixing the ring structure, the coordination to the metal atom can be further improved. Therefore, the driving voltage can be further reduced and the luminous efficiency can be further improved. From the perspective of further improving the stability and durability of the light-emitting element, R 3 and R 4 It is more preferred that the left-side skeleton of L in the general formula (1) is a phenanthroline skeleton and that the two groups are bonded to each other via a vinylene group.

[0063] In the general formula (1), L is an unsubstituted arylene group having 6 to 20 carbon atoms. As described above, since L is an unsubstituted arylene group having 6 to 20 carbon atoms, the groups on both sides of L are easily conjugated. Therefore, the charge transport property of the compound becomes greater. In addition, since the number of carbon atoms of L is not too much, the excessive improvement of crystallinity is suppressed, providing good film stability. Therefore, it is possible to reduce the driving voltage when the compound represented by the general formula (1) is used in a light-emitting element, and improve the luminous efficiency and durable life. From the viewpoint of further improving the luminous efficiency and durable life, L is preferably a phenylene, a naphthylene or a phenylene naphthylene.

[0064] From the viewpoint of inhibiting crystallization and improving the stability of the film quality, the molecular weight of the compound represented by the general formula (1) is preferably not less than 400. On the other hand, from the viewpoint of improving the processability during sublimation purification and vapor deposition, the molecular weight of the compound represented by the general formula (1) is preferably not more than 700, and more preferably not more than 640.

[0065] Examples of the compound represented by the general formula (1) include the following compounds. The following are illustrative only, and any compound other than the compounds explicitly described herein, as long as it is represented by the general formula (1), can also be preferably used.

[0066] [Chemical formula 4]

[0067]

[0068] [Chemical formula 5]

[0069]

[0070] [Chemical formula 6]

[0071]

[0072] [Chemical formula 7]

[0073]

[0074] [Chemical formula 8]

[0075]

[0076] [Chemical formula 9]

[0077]

[0078] [Chemical formula 10]

[0079]

[0080] [Chemical formula 11]

[0081]

[0082] [Chemical formula 12]

[0083]

[0084] [Chemical formula 13]

[0085]

[0086] [Chemical formula 14]

[0087]

[0088] [Chemical formula 15]

[0089]

[0090] [Chemical formula 16]

[0091]

[0092] [Chemical formula 17]

[0093]

[0094] [Chemical formula 18]

[0095]

[0096] [Chemical formula 19]

[0097]

[0098] [Chemical formula 20]

[0099]

[0100] [Chemical formula 21]

[0101]

[0102] [Chemical formula 22]

[0103]

[0104] [Chemical formula 23]

[0105]

[0106] [Chemical formula 24]

[0107]

[0108] [Chemical formula 25]

[0109]

[0110] [Chemical formula 26]

[0111]

[0112] [Chemical formula 27]

[0113]

[0114] [Chemical formula 28]

[0115]

[0116] [Chemical formula 29]

[0117]

[0118] [Chemical formula 30]

[0119]

[0120] [Chemical formula 31]

[0121]

[0122] [Chemical formula 32]

[0123]

[0124] [Chemical formula 33]

[0125]

[0126] The compound represented by the general formula (1) can be synthesized by a known synthesis method. Examples of the synthesis method include a coupling reaction of a halogenated aryl derivative and an arylboronic acid derivative using palladium, but the present invention is not limited thereto.

[0127] The compound represented by the general formula (1) is preferably used in any layer of the light-emitting element. As described later, the compound represented by the general formula (1) is suitable for use in the hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electrode protective film (covering layer), etc. in the light-emitting element. By using the material represented by the general formula (1) in any layer of the light-emitting element, a light-emitting element with excellent luminous efficiency and durable life can be provided.

[0128] (Light-emitting element)

[0129] The light emitting element has an anode, a cathode, and an organic layer interposed between the anode and the cathode, and the organic layer emits light by electric energy. In the following description, such a light emitting element may be referred to as an "organic EL element".

[0130] In addition to the structure containing only the light-emitting layer, the layer structure between the anode and the cathode in the organic EL element can also include a stacked structure of 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, and 7) hole injection layer / hole transport layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer.

[0131] In addition, it can also be a series type in which the above-mentioned stacked structure is stacked via a plurality of intermediate layers. The intermediate layer is also commonly referred to as an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connecting layer, and an intermediate insulating layer, and can be composed of known materials. Specific examples of the series type include 8) hole transport layer / luminescent layer / electron transport layer / charge generation layer / hole transport layer / luminescent layer / electron transport layer, 9) hole injection layer / hole transport layer / luminescent layer / electron transport layer / electron injection layer / charge generation layer / hole injection layer / hole transport layer / luminescent layer / electron transport layer / electron injection layer such a stacked structure including a charge generation layer as an intermediate layer between the anode and the cathode.

[0132] In addition, each of the above layers can be any of a single layer or a multilayer, and can also be doped. In particular, the above electron injection layer and the charge generation layer are preferably set as a metal doping layer doped with a metal, which can improve the electron transport ability and the electron injection ability to other adjacent layers. In addition, in addition to the above layers, a protective layer (covering layer) can be further provided, which can further improve the luminous efficiency through the optical interference effect.

[0133] The compound represented by the general formula (1) can be used in any of the above layers in the organic EL element, and is particularly suitable for use in an electron transport layer, a charge generation layer, or an electron injection layer. As an organic EL element of an embodiment of the present invention, the following structures can be cited as preferred structures: a structure having at least an electron transport layer and a light-emitting layer between the anode and the cathode, and the electron transport layer contains a compound represented by the general formula (1); a structure having at least a charge generation layer and a light-emitting layer between the anode and the cathode, and the charge generation layer contains a compound represented by the general formula (1); and a structure having at least an electron injection layer and a light-emitting layer between the anode and the cathode, and the electron injection layer contains a compound represented by the general formula (1).

[0134] In the organic EL element of the embodiment of the present invention, the anode and cathode have the function of supplying sufficient current for the light emission of the element, and in order to extract light, it is ideal that at least one of them is transparent or translucent. Usually, the anode formed on the substrate is set as a transparent electrode.

[0135] (Substrate)

[0136] In order to maintain the mechanical strength of the organic EL element, it is preferred to form the organic EL element on a substrate. As the substrate, glass substrates such as soda glass and alkali-free glass, plastic substrates, etc. can be cited. The thickness of the glass substrate can be sufficient as long as it is thick enough to maintain the mechanical strength, and it is sufficient if it is 0.5 mm or more. Regarding the material of the glass, it is preferred that there are few ions dissolved from the glass, and alkali-free glass is preferred. In addition, soda-lime glass with a barrier layer such as SiO2 applied is also commercially available, and this glass can also be used.

[0137] (anode)

[0138] The material used in the anode is preferably capable of efficiently injecting holes into the organic layer. In addition, in order to extract light, it is preferably transparent or translucent. As the material used in the anode, for example, conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), metals such as gold, silver, chromium, inorganic conductive materials such as copper iodide, copper sulfide, polythiophene, polypyrrole, polyaniline and other conductive polymers can be cited. Among them, ITO glass and Nesser glass (NESAglass) are preferred. These electrode materials can be used alone, or a variety of materials can be stacked or mixed.

[0139] (cathode)

[0140] The material used in the cathode is not particularly limited as long as it is a substance that can efficiently inject electrons into the light-emitting layer. As the material used in the cathode, for example, metals such as platinum, gold, silver, copper, iron, tin, aluminum, indium, or alloys of these metals with low work function metals such as lithium, sodium, potassium, calcium, and magnesium, multilayer stacking, etc. can be cited. Among them, from the aspects of resistance value, ease of film formation, stability of the film, luminous efficiency, etc., aluminum, silver, and magnesium are preferably used as the main components, and from the aspect of easy electron injection into the electron transport layer and the electron injection layer, it is more preferably composed of magnesium and silver.

[0141] (Protective layer)

[0142] In order to protect the cathode, a protective layer (covering layer) is preferably stacked on the cathode. As the material (capping material) constituting the protective layer, there is no particular limitation, for example, metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium, alloys using these metals, inorganic substances such as silicon dioxide, titanium dioxide and silicon nitride, organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, hydrocarbon-based polymer compounds, etc. can be cited. In addition, the compound shown in general formula (1) can also be used as a capping material. Among them, in the case where the organic EL element is an element structure (top emission structure) that extracts light from the cathode side, the capping material preferably has light transmittance in the visible light region.

[0143] (Hole Injection Layer)

[0144] The hole injection layer is a layer inserted between the anode and the hole transport layer. The hole injection layer can be one layer or multiple layers can be stacked. If there is a hole injection layer between the hole transport layer and the anode, not only lower voltage driving is performed, but also the durable life is improved, and the carrier balance of the element is further improved, and the luminous efficiency is also improved, so it is preferred.

[0145] The material used in the hole injection layer can use a known material. For example, benzidine derivatives, a material group called starburst arylamine, triarylamine derivatives, biscarbazole derivatives, pyrazoline derivatives, stilbene compounds, fluorene compounds, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, porphyrin derivatives and other heterocyclic compounds, polycarbonate having the above monomers in the side chain, styrene derivatives, polythiophene, polyaniline, polyfluorene, polyvinylcarbazole, polysilane and other polymer materials, etc. From the viewpoint of smoothly injecting and transporting holes from the anode to the hole transport layer, benzidine derivatives, starburst arylamine material groups, and fluorene compounds are more preferably used.

[0146] These materials can be used alone, or two or more materials can be mixed and used. In addition, multiple materials can also be stacked to form a hole injection layer. In addition, if the hole injection layer is composed of an acceptor compound alone or is doped with an acceptor compound in the hole injection material as described above, the above effect can be obtained more significantly, so it is more preferred. About the acceptor compound, when used in the form of a monolayer film, it refers to the material that forms a charge transfer complex with the hole transport layer in contact, and when used by doping, it refers to the material that forms a charge transfer complex with the material constituting the hole injection layer. If such a material is used, the conductivity of the hole injection layer is improved, which further contributes to the reduction of the driving voltage of the element, and can further improve the luminous efficiency and the durable life.

[0147] As the acceptor compound, known materials can be used. For example, metal oxides such as metal chlorides, molybdenum oxide, charge transfer complexes, organic compounds having nitro, cyano, halogen or trifluoromethyl in the molecule, quinone compounds, acid anhydride compounds, fullerenes, etc. can be cited. Among them, metal oxides and cyano-containing compounds are easy to handle and easy to evaporate, so it is easy to obtain the above-mentioned effect, so it is preferred. In any case where the hole injection layer is composed of an acceptor compound alone, or in any case where an acceptor compound is doped in the hole injection layer, the hole injection layer can be 1 layer, or it can be composed of multiple layers stacked.

[0148] (Hole Transport Layer)

[0149] 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 composed of a plurality of stacked layers.

[0150] The material used in the hole transport layer includes the materials exemplified as the material used in the hole injection layer. From the viewpoint of smoothly injecting and transporting holes to the light-emitting layer, triarylamine derivatives and benzidine derivatives are more preferred.

[0151] (Luminous layer)

[0152] The light-emitting layer can be any of a single layer and a multilayer, and is formed by a light-emitting material (a main material and a dopant material), which can be a mixture of a main material and a dopant material, a single main material, or a mixture of two main materials and one dopant material. That is, in each light-emitting layer, the organic EL element in the embodiment of the present invention can emit light from only the main material or the dopant material, or both the main material and the dopant material. From the viewpoint of efficiently utilizing electric energy and obtaining light with high color purity, the light-emitting layer is preferably obtained from a mixture of a main material and a dopant material. In addition, the main material and the dopant material can be one material or a combination of multiple materials. The dopant material can be contained in the whole of the main material or partially contained in the main material. The dopant material can be stacked or dispersed. The dopant material can control the luminescent color. From the viewpoint of suppressing the concentration quenching phenomenon, the amount of the dopant material is preferably less than 30% by weight, and more preferably less than 20% by weight, relative to the main material. The doping method can be formed by co-evaporation with the main material, or it can be pre-mixed with the main material and then evaporated simultaneously.

[0153] As the luminescent material, known materials can be used. For example, condensed ring derivatives such as anthracene and pyrene, metal chelated oxime compounds such as tris(8-hydroxyquinoline)aluminum, bisphenylene anthracene derivatives, bisphenylene benzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, oxadiazole derivatives, thiadiazole pyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolecarbazole derivatives, polyphenylene vinyl derivatives, polyparaphenylene derivatives, polymers such as polythiophene derivatives, etc. can be cited.

[0154] The host material contained in the luminescent material does not need to be limited to only one compound, and multiple compounds may be mixed and used. In addition, they may be stacked. As the host material, a known material may be used. There is no particular limitation, and examples thereof include naphthalene, anthracene, phenanthrene, pyrene, Compounds having fused aromatic rings such as tetracene, triphenylene, perylene, fluoranthene, fluorene, and indene, derivatives thereof, aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine, metal chelated oxime compounds such as tri(8-quinolinol)aluminum(III), distyryl derivatives such as distyrylbenzene derivatives, 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, polyphenyleneethylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives, and the like. Among them, as a host used when the light-emitting layer emits triplet light (phosphorescence), metal chelate oxime compounds, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, triphenylene derivatives, and the like are preferably used.

[0155] As the dopant material contained in the light-emitting material, for example, there can be mentioned compounds having an aryl ring, derivatives thereof, compounds having a heteroaryl ring, 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, compounds represented by the following general formula (2), etc. Among them, a dopant containing a diamine skeleton and a dopant containing a fluoranthene skeleton can further improve the light-emitting efficiency, and a compound represented by the following general formula (2) can further improve the light-emitting efficiency and the durable life.

[0156] [Chemical formula 34]

[0157]

[0158] In the general formula (2), Za ring, Zb ring and Zc ring 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. Preferably, Za ring, Zb ring and Zc ring are each independently a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms. 1 and Z 2 Each independently represents an oxygen atom, NRa (a nitrogen atom having a substituent Ra) or a sulfur atom, and in Z 1 When NRa is NRa, it may be bonded to the Za ring or Zb ring to form a ring, or it may not form a ring. 2In the case of NRa, it may be bonded to the Zb ring or the Zc ring to form a ring, or it may not form a ring. 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 2 All of them are 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 (silicon atom having a substituent Rb), P=O or P=S. Rb 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. Y is preferably a boron atom. Among all the above groups, as a substituent when substituted, 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, a cyano group, an aldehyde group, an acyl group, a carboxyl group, an ester group, an amide group, an acyl group, a sulfonyl group, a sulfonate group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxane group, a borane group, and an oxo group are preferred. In addition, these substituents may be further substituted by the above-mentioned substituents.

[0159] Examples of the alkyl group and the alkoxy group include the groups exemplified as the substituents in the general formula (1).

[0160] The cycloalkyl group includes, for example, saturated alicyclic hydrocarbon groups such as cyclopropyl, cyclohexyl, norbornyl, and adamantyl, 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 or more and 20 or less.

[0161] The heterocyclic group refers to an aliphatic ring having atoms other than carbon in the ring, such as a pyran ring, a piperidine ring, and 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 or more and 20 or less.

[0162] The alkenyl group represents an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, and a butadienyl group, and these 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 or more and 20 or less.

[0163] The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group, and a cyclohexenyl group, and these may or may not have a substituent.

[0164] The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, and 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 or more and 20 or less.

[0165] The aryl group represents, for example, phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, anthracenyl, triphenylenyl, benzanthryl, The aromatic hydrocarbon groups include phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, anthracenyl, pyrenyl, fluoranthenyl, triphenylene, benzofluoranthenyl, dibenzoanthryl, perylene, spiroenyl, etc. Among them, phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, anthracenyl, pyrenyl, fluoranthenyl, triphenylene. The aryl group may or may not have a substituent. The number of carbon atoms in the aryl group is not particularly limited, but is preferably 6 to 40, and more preferably 6 to 30.

[0166] In addition, in the case where the substituted phenyl group has substituents on two adjacent carbon atoms in the phenyl group, these substituents may form a ring structure with each other. The group formed as a result may correspond to any one or more of "substituted phenyl group", "aryl group having a structure formed by condensing two or more rings", and "heteroaryl group having a structure formed by condensing two or more rings" according to its structure.

[0167] The heteroaryl group represents, for example, a cyclic aromatic group having one or more atoms other than carbon in the ring, such as pyridyl, furanyl, thienyl, quinolyl, isoquinolyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, naphthyridinyl, cinnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzothienyl, indolyl, dibenzofuranyl, dibenzothienyl, carbazolyl, benzocarbazolyl, carbolyl, indolecarbazolyl, benzofuranocarbazolyl, benzothiophenocarbazolyl, dihydroindenocarbazolyl, benzoquinolyl, acridinyl, dibenzoacridinyl, benzimidazolyl, imidazopyridinyl, benzoxazolyl, benzothiazolyl, and phenanthrolinyl. Among them, naphthyridinyl represents any one of 1,5-naphthyridinyl, 1,6-naphthyridinyl, 1,7-naphthyridinyl, 1,8-naphthyridinyl, 2,6-naphthyridinyl, and 2,7-naphthyridinyl. The heteroaryl group may or may not have a substituent. The number of ring atoms of the heteroaryl group is not particularly limited, and is preferably 3 to 40, and more preferably 3 to 30.

[0168] An alkylthio group is a group in which the oxygen atom of the ether bond of an alkoxy group is replaced by a sulfur atom. An alkylthio group may or may not have a substituent. The number of carbon atoms in an alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0169] 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 or more and 40 or less.

[0170] The aryl thioether group is a functional group in which the oxygen atom of the ether bond of the aryl ether group is replaced by 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 or more and 40 or less.

[0171] Halogen represents fluorine, chlorine, bromine or iodine.

[0172] Acyl groups, for example, represent functional groups such as acetyl, propionyl, benzoyl, acryloyl, etc., which are bonded to alkyl, cycloalkyl, alkenyl, alkynyl, aryl, and heteroaryl groups via a carbonyl 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 or more and 40 or less, and more preferably 2 or more and 30 or less.

[0173] The ester group, for example, represents a functional group formed by an ester bond such as an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc., and may or may not have a substituent. The number of carbon atoms in the ester group is not particularly limited, and is preferably in the range of 1 to 20. More specifically, 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, phenyl ester groups such as phenoxycarbonyl, etc. can be cited.

[0174] The amide group represents, for example, a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. 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 specifically, methylamide group, ethylamide group, propylamide group, butylamide group, isopropylamide group, hexylamide group, phenylamide group, etc. may be cited.

[0175] The sulfonyl group represents a functional group formed by bonding, for example, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. via a -S(=O)2- 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.

[0176] The sulfonate group, for example, represents a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. via a sulfonate bond, and may or may not have a substituent. Here, the sulfonate bond refers to a bond formed by replacing the carbonyl part (i.e., -C(=O)-) of the ester bond with the sulfonyl part (i.e., -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.

[0177] The sulfonamide group, for example, represents a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. via a sulfonamide bond, and may or may not have a substituent. Here, the sulfonamide bond refers to a bond formed by replacing the carbonyl part (i.e., -C(=O)-) of the ester bond with 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.

[0178] 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.

[0179] The silyl group represents a functional group bonded with a substituted or unsubstituted silicon atom, for example, an alkylsilyl group such as trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, propyldimethylsilyl, vinyldimethylsilyl, and an arylsilyl group 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.

[0180] The siloxane group refers to a silicon compound group connected via an ether bond, such as a trimethylsiloxane group, for example. The siloxane group may or may not have a substituent.

[0181] The borane group may or may not have a substituent.

[0182] Examples of the compound represented by the general formula (2) include the following.

[0183] [Chemical formula 35]

[0184]

[0185] In the organic EL device according to the embodiment of the present invention, it is also preferred that the light-emitting layer contains a triplet light-emitting material.

[0186] As the dopant used when the light-emitting layer performs triplet luminescence (phosphorescent luminescence), it is preferred to include a metal complex compound of 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 or a phenylquinoline skeleton or a carbene skeleton. However, it is not limited to these, and appropriate complexes can be selected according to the desired luminescent color, device performance, and the relationship with the host compound. Specifically, there can be mentioned tris(2-phenylpyridyl)iridium complex, tris{2-(2-thienyl)pyridyl}iridium complex, tris{2-(2-benzothienyl)pyridyl}iridium complex, tris(2-phenylbenzothiazole)iridium complex, tris(2-phenylbenzooxazole)iridium complex, tribenzoquinolineiridium complex, bis(2-phenylpyridyl)(acetylacetonate)iridium complex, bis{2-(2-thienyl)pyridyl}iridium complex, bis{2-(2-benzothienyl)pyridyl}(acetylacetonate)iridium complex, bis(2-phenylbenzothiazole)(acetylacetonate)iridium complex Iridium complex, bis(2-phenylbenzoxazole)(acetylacetone)iridium complex, bisbenzoquinoline(acetylacetone)iridium complex, bis{2-(2,4-difluorophenyl)pyridyl}(acetylacetone)iridium complex, tetraethylporphyrin platinum complex, {tri(enoyltrifluoroacetone)mono(1,10-phenanthroline)}europium complex, {tri(enoyltrifluoroacetone)mono(4,7-diphenyl-1,10-phenanthroline)}europium complex, {tri(1,3-diphenyl-1,3-propanedione)mono(1,10-phenanthroline)}europium complex, triacetylacetonate terbium complex, etc. In addition, the phosphorescent dopant described in Japanese Patent Application Laid-Open No. 2009-130141 is also suitable. Iridium complex or platinum complex is preferred, which can further improve the luminous efficiency.

[0187] The triplet light-emitting materials used as dopant materials may be contained in the light-emitting layer alone or in a mixture of two or more. When two or more triplet light-emitting materials are used, the total weight of the dopant materials is preferably less than 30% by weight, more preferably less than 20% by weight, relative to the host material.

[0188] Preferred hosts and dopants in the triplet light-emitting system are not particularly limited, but specific examples include the following.

[0189] [Chemical formula 36]

[0190]

[0191] [Chemical formula 37]

[0192]

[0193] In addition, it is also preferred that the light-emitting layer contains a thermally activated delayed fluorescence material. Thermally activated delayed fluorescence is explained in "The Most Advanced Organic EL" (edited by Chiba Andachi and Hiroshi Fujimoto, published by CMC) pages 87 to 103. In this document, it is explained that by making the energy levels of the excited singlet state and the excited triplet state of the fluorescent material close, the reverse energy transfer from the excited triplet state to the excited singlet state, which usually has a low transition probability, occurs with high efficiency, showing thermally activated delayed fluorescence (Thermally Activated delayed Fluorescence, TADF). In addition, in Figure 5 of this document, the generation mechanism of delayed fluorescence is explained. The luminescence of delayed fluorescence can be confirmed by transition PL (transient photo luminescence) measurement.

[0194] Thermally activated delayed fluorescence materials are also commonly referred to as TADF materials. Thermally activated delayed fluorescence materials can be materials that display thermally activated delayed fluorescence with a single material, or materials that display thermally activated delayed fluorescence with multiple materials. When the material contains multiple materials, it can be used in the form of a mixture, or the layers containing each material can be stacked for use. As thermally activated delayed fluorescence materials, known materials can be used. For example, benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indole and carbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, oxadiazole derivatives, etc. can be cited, but are not limited to these.

[0195] In an element containing a TADF material in a light-emitting layer, it is preferred that a fluorescent dopant is also contained in the light-emitting layer, because the TADF material converts triplet excitons into singlet excitons, and the fluorescent dopant receives the singlet excitons, thereby achieving higher light-emitting efficiency and longer durable life.

[0196] (Electron Transport Layer)

[0197] In the present invention, the electron transport layer refers to a layer that injects electrons from the cathode and then transports electrons. For the electron transport layer, it is desired that the electron injection efficiency is high and the injected electrons are efficiently transported. Therefore, the material constituting the electron transport layer is preferably a substance with large electron affinity, large electron mobility, excellent stability, and impurities that are not easy to produce as traps during manufacture and use. In particular, when the film thickness is stacked thickly, low molecular weight compounds crystallize, etc., which causes the film quality to deteriorate easily. Therefore, in order to maintain a stable film quality, a compound with a molecular weight of more than 400 is preferred. However, considering the transmission balance of holes and electrons, if the electron transport layer mainly plays a role in efficiently preventing holes from the anode from recombining and flowing to the cathode side, even if it is composed of a material with not so high electron transport ability, the effect of improving the luminous efficiency is the same as that of a material with high electron transport ability. Therefore, in the electron transport layer in the present invention, a hole blocking layer that can efficiently prevent the movement of holes is also included as a synonymous layer, and the hole blocking layer and the electron transport layer can be constituted separately or by stacking a variety of materials.

[0198] As the electron transport material used in the electron transport layer, known materials can be used. For example, various metal complexes such as fused polycyclic aromatic derivatives, styryl aromatic ring derivatives, quinone derivatives, phosphorus oxide derivatives, hydroxyquinoline complexes, benzohydroxyquinoline complexes, hydroxylazole complexes, azomethine complexes, tropolone metal complexes, and flavonol metal complexes can be cited. From the perspective of further reducing the driving voltage and obtaining more efficient luminescence, it is preferred to use a compound composed of an element selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus, and having a heteroaryl ring structure containing electron accepting nitrogen.

[0199] The electron accepting nitrogen mentioned here means a nitrogen atom that forms a multiple bond with adjacent atoms. Since the nitrogen atom has a high electron negativity, the multiple bond has the property of electron accepting. Therefore, the aromatic heterocycle containing electron accepting nitrogen has a high electron affinity. The electron transport material with electron accepting nitrogen easily accepts electrons from the cathode with high electron affinity, and can achieve driving at a lower voltage. In addition, the supply of electrons to the light-emitting layer becomes more, and the probability of recombination becomes higher, so the luminous efficiency is further improved.

[0200] Examples of the heteroaryl ring containing 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.

[0201] As compounds having heteroaryl ring structures, for example, pyridine derivatives, triazine derivatives, quinazoline derivatives, pyrimidine derivatives, benzimidazole derivatives, benzoxazole derivatives, benzothiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives, quinoxaline derivatives and naphthyridine derivatives can be mentioned. Among them, imidazole derivatives, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, benzoquinoline derivatives, bipyridine derivatives, terpyridine derivatives and naphthyridine derivatives are preferably used from the viewpoint of electron transport ability.

[0202] In addition, if these derivatives have a fused polycyclic aromatic skeleton, the glass transition temperature is improved, and the electron mobility is also increased, and the driving voltage of the organic EL element can be further reduced, so it is preferred. In addition, considering that the durable life of the element is further improved, the ease of synthesis, and the raw material acquisition is easy, the fused polycyclic aromatic skeleton is more preferably a fluoranthene skeleton, anthracene skeleton, pyrene skeleton or phenanthroline skeleton.

[0203] Preferred electron transport materials are not particularly limited, but specific examples include the following.

[0204] [Chemical formula 38]

[0205]

[0206] [Chemical formula 39]

[0207]

[0208] In addition, the compound represented by the general formula (1) also has a high electron transport property and exhibits excellent properties as an electron transport layer, and therefore is preferred.

[0209] The electron transport material may be used alone, or two or more of the electron transport materials may be mixed and used, or one or more of the other electron transport materials may be mixed with the electron transport material for use. In addition, a donor compound may also be contained. Here, the donor compound refers to a compound that facilitates electron injection from the cathode or electron injection layer to the electron transport layer by improving the electron injection barrier, thereby improving the conductivity of the electron transport layer.

[0210] As the donor compound, from the viewpoint of low work function and improved electron transport properties, it is preferred to contain alkali metal atoms, alkaline earth metal atoms or rare earth metal atoms. Among them, from the viewpoint of being able to further reduce the driving voltage of the organic EL, it is more preferred to contain alkali metal atoms or rare earth metal atoms as donor compounds in the electron transport layer.

[0211] In addition, from the perspective of easy evaporation in vacuum and excellent processing, compared to metal monomers, donor compounds are preferably inorganic salts or metal-organic complexes. In addition, from the perspective of making it easy to process in the atmosphere and being able to easily adjust the added concentration, it is more preferably in the state of a metal-organic complex. As examples of inorganic salts, oxides, nitrides, fluorides, carbonates, etc. can be cited. As preferred examples of organics in complexes with organics, hydroxyquinoline, benzohydroxyquinoline, pyridylphenol, flavonols, hydroxyimidazopyridine, hydroxybenzoxazole, hydroxytriazole, etc. can be cited. Among them, from the perspective of being able to further reduce the driving voltage of the organic EL element, it is preferred that an alkali metal and an organic complex are contained in the electron transport layer as a donor compound. In addition, from the perspective of ease of synthesis and thermal stability, as a donor compound, a complex of lithium and an organic substance is more preferably used, and hydroxyquinoline lithium (Liq) that can be obtained in a relatively cheap manner is particularly preferred.

[0212] The ionization potential of the electron transport layer is not particularly limited, but is preferably 5.6 eV to 8.0 eV, and more preferably 5.6 eV to 7.0 eV.

[0213] The formation methods of the above-mentioned layers constituting the organic EL element are not particularly limited and include resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, coating, etc. Generally, resistance heating evaporation or electron beam evaporation is preferred from the perspective of element characteristics.

[0214] (Electron Injection Layer)

[0215] 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, and in the case of insertion, 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.

[0216] In addition, the electron injection layer may be made of an inorganic substance such as an insulator or a semiconductor, and a known material may be used. By using these materials, short circuits of the organic EL element can be suppressed and electron injection properties can be improved.

[0217] As such an insulator, at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides is preferred.

[0218] In addition, it is also suitable to use a complex of organic matter and metal. In the case of using a complex of organic matter and metal in the electron injection layer, the film thickness can be easily adjusted. As the preferred example of the organic matter in the organometallic complex, hydroxyquinoline, benzohydroxyquinoline, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzoxazole, hydroxytriazole etc. can be enumerated.

[0219] In addition, the layer comprising the compound shown in the general formula (1) also has high electron injection properties, and as an electron injection layer, it shows excellent properties, so it is preferred. In addition, the compound shown in the general formula (1) is preferably doped with the above-mentioned alkali metal or rare earth metal, which can further reduce the driving voltage and further improve the durable life. That is, the electron injection layer preferably further contains alkali metal atoms or rare earth metal atoms.

[0220] (Charge Generation Layer)

[0221] The charge generation layer in the present invention is usually composed of a double layer, specifically, it can be used as a pn junction charge generation layer including an n-type charge generation layer and a p-type charge generation layer. With regard to the above-mentioned pn junction charge generation layer, a charge is generated by applying a voltage in an organic EL element, or the charge is separated into holes and electrons, and these holes and electrons are injected into the light-emitting layer via a hole transport layer and an electron transport layer. Specifically, the charge generation layer functions as an intermediate layer in an organic EL element stacked with light-emitting layers. The n-type charge generation layer supplies electrons to the first light-emitting layer present on the anode side, and the p-type charge generation layer supplies holes to the second light-emitting layer present on the cathode side. Therefore, the luminous efficiency in an organic EL element stacked with multiple light-emitting layers can be further improved, the driving voltage can be reduced, and the durability of the element can be further improved.

[0222] The n-type charge generation layer comprises an n-type dopant and a host, which can use conventional materials. For example, as the n-type dopant, an alkali metal, an alkaline earth metal or a rare earth metal can be used. In addition, as the host, compounds having nitrogen-containing aromatic heterocycles such as phenanthroline derivatives and oligopyridine derivatives can be used. In particular, the compound represented by the general formula (1) and the phenanthroline dimer are preferred as the host of the above-mentioned n-type charge generation layer and show excellent properties.

[0223] As one embodiment of the charge generating layer, it is preferred that the charge generating layer further contains a phenanthroline dimer in addition to the compound represented by the general formula (1). Examples of the phenanthroline dimer include the following compounds.

[0224] [Chemical formula 40]

[0225]

[0226] As one embodiment of the charge generating layer, it is preferred that the charge generating layer further contains an alkali metal atom or a rare earth metal atom in addition to the compound represented by the general formula (1). As the alkali metal atom, Li is particularly preferred. As the rare earth metal atom, Yb is particularly preferred.

[0227] As one embodiment of the charge generating layer, a structure containing a phenanthroline dimer and an alkali metal or rare earth metal atom in addition to the compound represented by the general formula (1) is also preferred.

[0228] The p-type charge generation layer includes a p-type dopant and a host, which can use conventional materials. For example, as a p-type dopant, tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), tetracyanoquinodimethane derivatives, radium derivatives, iodine, FeCl3, FeF3, SbCl5, etc. can be used. As a p-type dopant, a radium derivative is preferred. As a host, an arylamine derivative is preferred.

[0229] The thickness of the organic layer depends on the resistance of the light-emitting material and is therefore not limited, but is preferably 1 to 1000 nm. The thickness 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.

[0230] The organic EL element of the embodiment of the present invention has the function of converting electrical energy into light. Here, as electrical energy, direct current is mainly used, but pulse current and alternating current can also be used. There is no particular restriction on the current value and voltage value. If the power consumption and life of the element are taken into consideration, the current value and voltage value should be selected in a way that the maximum brightness can be obtained with the lowest possible energy.

[0231] The light-emitting device according to the embodiment of the present invention is suitable for use as a display device such as a display that displays in a matrix and / or segment system. That is, the light-emitting device containing the compound according to the embodiment of the present invention is suitable for use as a display device.

[0232] The light-emitting element of the embodiment of the present invention is also preferably used as a backlight source for various devices. The backlight source is mainly used to improve the visibility of display devices such as displays that do not emit light by themselves, and is used for liquid crystal displays, clocks, audio devices, automobile panels, display boards, and logos. In particular, the light-emitting element of the present invention is preferably used for liquid crystal displays, especially backlight sources for personal computers for which thinning has been studied, and can provide a backlight source that is thinner and lighter than previous backlight sources.

[0233] The light-emitting element of the embodiment of the present invention is also preferably used as various lighting devices. That is, the light-emitting element containing the compound of the embodiment of the present invention is suitable for use as a lighting device. The light-emitting element of the embodiment of the present invention can take into account both high luminous efficiency and high color purity, and can be thinned and lightweight, so it is possible to achieve a lighting device with low power consumption, bright luminous color, and high design.

[0234] Example

[0235] Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

[0236] Synthesis Example 1: Synthesis of Compound 2

[0237] [Chemical formula 41]

[0238]

[0239] A mixed solution of 10g raw material A, 4.9g of 6-bromo-2,2'-bromobipyridine, 150mg of dichlorobis(triphenylphosphine palladium) dichloride, 40ml of 0.75M potassium carbonate aqueous solution, and 210ml of dimethoxyethane was heated and stirred for 5 hours under a nitrogen stream and reflux. After cooling to room temperature, water was added for filtration, washed with methanol and vacuum dried. For the obtained solid, activated carbon was used to remove the catalyst, the solvent was removed by evaporation, and the obtained solid was recrystallized with toluene and vacuum dried to obtain 7.2g of compound 2.

[0240] For the obtained compound 7, an oil diffusion pump was used at 1 × 10 -3 Sublimation purification was performed at about 290° C. under a pressure of 1.3 Pa. The HPLC purity (area % at a measurement wavelength of 254 nm) of Compound 2 before and after sublimation purification was 99.9%.

[0241] After sublimation purification, the 1 H-NMR analysis identified the structure of Compound 2. The analysis results are shown below.

[0242] MS (m / z): 487 [M+H] +

[0243] 1H-NMR (400MHz, CDCl3) δ: 9.37 (m, 1H), 8.72-8.74 (m, 2H), 8.51-8.54 (m, 3H), 8.45-8.47 (m, 1H), 8.29-8.41 (m, 3H), 8.17-8.20 (m, 1 H), 8.09-8.12(m, 1H), 7.98-8.02(m, 1H), 7.82-7.86(m, 3H), 7.74-7.76(m, 1H), 7.46-7.55(m, 3H), 7.35-7.30(m, 1H), 7.26(m, 1H).

[0244] Synthesis Example 2: Synthesis of Compound 6

[0245] [Chemical formula 42]

[0246]

[0247] In a mixed solution of 34.3 g of 1,4-dibromonaphthalene and 130 ml of tetrahydrofuran, 75 ml of n-butyl lithium (1.6 M hexane solution) was added dropwise at 0°C under a nitrogen stream. After stirring at 0°C for 30 minutes, it was added dropwise to a mixed solution of 25.5 g of 2-phenyl-1,10-phenanthroline and 150 ml of THF at 0°C. After warming to room temperature, 150 ml of saturated aqueous ammonium chloride solution was added to the reaction solution. The organic layer was extracted with ethyl acetate and evaporated. 340 ml of dichloromethane and 15.6 g of manganese dioxide were added to the obtained solid, and stirred at room temperature for 1 hour. The reaction solution was filtered, and the filtrate was concentrated by evaporation. The residual solid was washed with methanol and vacuum dried to obtain 30.0 g of intermediate A.

[0248] Next, a mixed solution of 15.5 g of intermediate A, 17.0 g of borate ester A, 10.0 g of potassium acetate, 550 mg of bis(diphenylphosphino)ferrocenepalladium dichloride, and 335 ml of dimethylformamide was heated and stirred at 100° C. for 1.5 hours under a nitrogen stream. After cooling to room temperature, water was added and filtered, washed with methanol and vacuum dried to obtain 15.0 g of intermediate B.

[0249] Next, a mixed solution of 15.0 g of intermediate B, 7.9 g of raw material B, 420 mg of dichlorobis(triphenylphosphine palladium) dichloride, 50 ml of 0.9 M potassium carbonate aqueous solution, and 300 ml of 1,4-dioxane was heated and stirred under reflux for 8 hours under a nitrogen stream. After cooling to room temperature, water was added for filtration, washed with methanol and vacuum dried. For the obtained solid, the catalyst was removed using activated carbon, the solvent was removed by evaporation, and the obtained solid was recrystallized with toluene and methanol, and then vacuum dried to obtain 7.5 g of compound 6.

[0250] For the obtained compound 6, an oil diffusion pump was used at 1×10 -3 Sublimation purification was performed at about 340° C. under a pressure of 1.3 Pa. The HPLC purity (area % at a measurement wavelength of 254 nm) of Compound 6 before and after sublimation purification was 99.9%.

[0251] After sublimation purification, the 1 H-NMR analysis identified the structure of Compound 6. The analysis results are shown below.

[0252] MS (m / z): 613 [M+H] +

[0253] 1 H-NMR (400MHz, DMSO-d6) δ: 8.94-9.00 (m, 1H), 8.70-8.74 (m, 2H), 8.65-8 .67(m,1H),8.55-8.57(m,1H),8.43-8.47(m,4H),8.38-8.42(m,2H),8.18 -8.24(m, 2H), 8.05-8.14(m, 5H), 7.95-7.99(m, 1H), 7.77-7.81(m, 2H), 7. 70-7.73 (m, 1H), 7.66-7.69 (m, 2H), 7.53-7.58 (m, 2H), 7.47-7.53 (m, 2H).

[0254] Synthesis Example 3: Synthesis of Compound 10

[0255] [Chemical formula 43]

[0256]

[0257] Under nitrogen flow, 150 ml of n-butyl lithium (1.6 M hexane solution) was added dropwise to a mixed solution of 41.0 g of 3-bromotoluene and 150 ml of tetrahydrofuran at 0°C. After stirring at 0°C for 30 minutes, it was added dropwise to a mixed solution of 36.0 g of 1,10-phenanthroline and 150 ml of THF at 0°C. After warming to room temperature, 250 ml of saturated aqueous ammonium chloride solution was added to the reaction solution. The organic layer was extracted with ethyl acetate and evaporated. 340 ml of dichloromethane and 34.7 g of manganese dioxide were added to the obtained solid, and stirred at room temperature for 1 hour. The reaction solution was filtered, and the filtrate was concentrated by evaporation. The residual solid was washed with methanol and vacuum dried to obtain 34.5 g of intermediate C.

[0258] Next, under a nitrogen stream, 96 ml of n-butyl lithium (1.6 M hexane solution) was added dropwise to a mixed solution of 36.1 g of 1,3-dibromobenzene and 96 ml of tetrahydrofuran at 0°C. After stirring at 0°C for 30 minutes, it was added dropwise to a mixed solution of 34.5 g of intermediate C and 96 ml of THF at 0°C. After warming to room temperature, 150 ml of saturated aqueous ammonium chloride solution was added to the reaction solution. The organic layer was extracted with ethyl acetate and evaporated. 200 ml of dichloromethane and 22.1 g of manganese dioxide were added to the obtained solid, and stirred at room temperature for 1 hour. The reaction solution was filtered, and after the filtrate was concentrated by evaporation, the residual solid was washed with methanol and vacuum dried to obtain 33.2 g of intermediate D.

[0259] Next, a mixed solution of 33.0 g of intermediate D, 27.6 g of borate ester A, 22.8 g of potassium acetate, 570 mg of bis(diphenylphosphino)ferrocenepalladium dichloride, and 780 ml of dimethylformamide was heated and stirred at 100° C. for 3 hours under a nitrogen stream. After cooling to room temperature, water was added and filtered, washed with methanol and vacuum dried to obtain 35.2 g of intermediate E.

[0260] Next, 30.0g of intermediate E, 16.9g of raw material B, 890mg of dichlorobis(triphenylphosphine palladium) dichloride, 140ml of 0.9M potassium carbonate aqueous solution, and a mixed solution of 630ml of 1,4-dioxane were heated and stirred under reflux for 12 hours under a nitrogen stream. After cooling to room temperature, water was added for filtration, washed with methanol and vacuum dried. For the obtained solid, activated carbon was used for catalyst removal, the solvent was removed by evaporation, and the obtained solid was recrystallized with toluene and methanol, and then vacuum dried to obtain 25.5g of compound 10.

[0261] For the obtained compound 10, an oil diffusion pump was used at 1 × 10 -3 Sublimation purification was performed at about 340° C. under a pressure of 1.3 Pa. The HPLC purity (area % at a measurement wavelength of 254 nm) of Compound 10 before and after sublimation purification was 99.9%.

[0262] After sublimation purification, the 1 H-NMR analysis identified the structure of Compound 10. The analysis results are shown below.

[0263] MS (m / z): 577 [M+H] +

[0264] 1H-NMR (400MHz, DMSO-d6) δ: 9.20-9.22 (m, 1H), 8.58-8.70 (m, 4H), 8.49-8.56 (m, 4H), 8.36-8.48 (m, 4H), 8.05-8.14 ( m, 2H), 7.94-8.03 (m, 2H), 7.78-7.82 (m, 1H), 7.55-7.60 (m, 2H), 7.38-7.48 (m, 3H), 6.97-7.09 (m, 2H), 2.14 (s, 3H).

[0265] Next, the evaluation method in each example is described.

[0266] (Drive voltage)

[0267] The devices obtained in Examples 1 to 27 and Comparative Examples 1 to 16 were each charged at 10 mA / cm 2 The initial driving voltage was measured by direct current driving. In addition, the current density was 10 mA / cm2 at a temperature of 70°C. 2 The voltage at the time of direct current driving for 100 hours was used to calculate the voltage rise from the initial driving voltage.

[0268] In addition, the organic EL devices obtained in Examples 28 to 81 and Comparative Examples 17 to 48 were each subjected to a luminance of 1000 cd / m 2 Light up and measure the initial driving voltage. In addition, measure the current density of 10 mA / cm at room temperature. 2 The voltage at the time of constant current driving for 100 hours was used to calculate the voltage rise from the initial driving voltage.

[0269] The smaller the initial driving voltage is, the lower the voltage can be used for driving, so it can be evaluated that the luminous efficiency (brightness / power) is better. In addition, the smaller the voltage rise is, the better the durable life can be evaluated.

[0270] (External quantum efficiency)

[0271] The organic EL devices obtained in Examples 28 to 81 and Comparative Examples 17 to 48 were each subjected to a current density of 10 mA / cm 2 The light was turned on, and the external quantum efficiency was measured to evaluate the luminous efficiency. The higher the external quantum efficiency, the better the luminous efficiency can be evaluated.

[0272] (Durability)

[0273] The organic EL devices obtained in Examples 28 to 81 and Comparative Examples 17 to 48 were subjected to a current of 10 mA / cm 2 The constant current was continued to drive the device, and the time required for the luminance to decrease by 20% from the initial luminance was measured as the durability.

[0274] Example 1

[0275] A glass substrate (GEOMATEC CO., LTD., 11Ω / □, sputtered product) with a 125nm ITO transparent conductive film deposited as an anode was cut into 38mm×46mm and etched. The obtained substrate was ultrasonically cleaned for 15 minutes using "Semico Clean" (registered trademark) 56 (trade name, manufactured by Furuuchi Chemical Corporation) and then cleaned with ultrapure water. Immediately before the element was made, the substrate was subjected to UV-ozone treatment for 1 hour, placed in a vacuum evaporation device, and evacuated until the vacuum degree in the device reached 5×10 -4 Pa or less. Compound 1 and metal element Yb as a dopant were evaporated by resistance heating at a deposition rate ratio of Compound 1:Yb=9:1 to form a layer with a weight ratio of 9:1. Then, 60nm of aluminum was evaporated to form a cathode, and a 5mm×5mm square element was made. The film thickness mentioned here is the value displayed by the quartz oscillation film thickness monitor, which is also common in other embodiments and comparative examples.

[0276] This element was evaluated by the above method. As a result, the initial driving voltage was 0.067 V, and the amount of voltage increase when driven at 70° C. for 100 hours was 0.035 V.

[0277] [Chemical formula 44]

[0278]

[0279] Examples 2 to 27, Comparative Examples 1 to 16

[0280] A device was produced in the same manner as in Example 1 except that the compound, metal element, and the vapor deposition rate ratio between the compound and the metal element were changed as shown in Table 1. The results of each example and comparative example are shown in Table 1. Compounds 2 to 19 are the following compounds.

[0281] [Chemical formula 45]

[0282]

[0283] [Chemical formula 46]

[0284]

[0285] [Table 1]

[0286]

Table 1

[0287]

[0288] Embodiment 28

[0289] A glass substrate (GEOMATEC CO., LTD., 11Ω / □, sputtered product) with a 165nm ITO transparent conductive film deposited as an anode was cut into 38mm×46mm and etched. The obtained substrate was ultrasonically cleaned for 15 minutes using "Semico Clean" 56 (trade name, manufactured by Furuuchi Chemical Corporation) and then cleaned with ultrapure water. Immediately before the production of the element, the substrate was subjected to UV-ozone treatment for 1 hour, placed in a vacuum evaporation device, and evacuated until the vacuum degree in the device reached 5×10 -4 Pa or less. By the resistance heating method, first, 5 nm of p-D1 is evaporated as a hole injection layer, and then 50 nm of HT-1 is evaporated as a hole transport layer. Next, as a light-emitting layer, a mixed layer of the main material H-1 and the dopant material D-1 is evaporated to a thickness of 20 nm in a manner that the doping concentration becomes 5 weight %. Next, as an electron transport layer, ET-1 and 2E-1 are evaporated to a thickness of 35 nm in a manner that the evaporation rate ratio becomes ET-1 and 2E-1=1:1. Next, as an electron injection layer, compound 1 and the metal element Yb as a dopant are evaporated to 10 nm in a manner that the evaporation rate ratio becomes compound 1:Yb=9:1. Then, 60 nm of aluminum is evaporated as a cathode to make a 5 mm×5 mm square organic EL element.

[0290] The organic EL element was evaluated by the above method, and the initial driving voltage was 4.52 V, the external quantum efficiency (luminous efficiency) was 5.50%, the durable life was 960 hours, and the voltage rise amount when driven for 100 hours at room temperature was 0.021 V. It should be noted that p-D1, HT-1, H-1, D-1, ET-1 and 2E-1 are the compounds shown below.

[0291] [Chemical formula 47]

[0292]

[0293] Examples 29 to 54, Comparative Examples 17 to 32

[0294] An organic EL device was produced in the same manner as in Example 28 except that the compound, metal element, and the vapor deposition rate ratio between the compound and the metal element were changed as shown in Table 2. Table 2 shows the results of each of the Examples and Comparative Examples.

[0295] [Table 2] [Table 2]

[0296]

[0297] Embodiment 55

[0298] A glass substrate (GEOMATEC CO., LTD., 11Ω / □, sputtered product) with a 165nm ITO transparent conductive film deposited as an anode was cut into 38mm×46mm and etched. The obtained substrate was ultrasonically cleaned for 15 minutes using "Semico Clean" 56 (trade name, manufactured by Furuuchi Chemical Corporation) and then cleaned with ultrapure water. Immediately before the production of the element, the substrate was subjected to UV-ozone treatment for 1 hour, placed in a vacuum evaporation device, and evacuated until the vacuum degree in the device reached 5×10 -4 Pa or less. First, 5 nm of p-D1 was evaporated as a hole injection layer by resistance heating. Next, a light-emitting unit (first light-emitting unit) including a hole transport layer, a light-emitting layer, and an electron transport layer was formed on the hole injection layer.

[0299] Specifically, 50 nm of HT-1 is vapor deposited as a hole transport layer. Next, as a light-emitting layer, a mixed layer of the main material H-1 and the dopant material D-1 is vapor deposited to a thickness of 20 nm in a manner that the doping concentration becomes 5 wt%. Next, as an electron transport layer, ET-1 and 2E-1 are vapor deposited to a thickness of 35 nm in a manner that the vapor deposition rate ratio becomes ET-1 to 2E-1 = 1:1.

[0300] On the first light-emitting unit, as an N-type charge generation layer, compound 1 and metal element Yb as a dopant were evaporated at a deposition rate ratio of compound 1:Yb=9:1 for 10nm, and then as a P-type charge generation layer, 10nm of p-D1 was evaporated.

[0301] The second light-emitting unit was formed in the same manner as the first light-emitting unit after the charge generation layer. Then, as an electron injection layer, compound 1 and metal element Yb as a dopant were vapor-deposited at a vapor deposition rate ratio of compound 1:Yb=9:1 to 10 nm, followed by vapor deposition of 60 nm of aluminum to form a cathode, and a 5 mm×5 mm square organic EL element was produced.

[0302] The organic EL element was evaluated by the above method. As a result, the initial driving voltage was 9.14 V, the external quantum efficiency (luminous efficiency) was 11.03%, and the durable life was 1950 hours.

[0303] Examples 56 to 81, Comparative Examples 33 to 48

[0304] An organic EL device was produced in the same manner as in Example 55 except that the vapor deposition rate ratio of the compound used and the compound metal element was changed as shown in Table 3. Table 3 shows the results of each of the Examples and Comparative Examples.

[0305] [Table 3]

[0306]

Table 3

[0307]

[0308] In Examples 1 to 27, the results of single-charge elements using the compound represented by the general formula (1) together with Li as an alkali metal element and Yb as a rare earth metal element are shown. On the other hand, in Comparative Examples 1 to 16, the results of light-emitting elements using compounds 13 to 19 that are not compounds represented by the general formula (1) together with Li as an alkali metal element and Yb as a rare earth metal element are shown. Compared with each comparative example, the initial driving voltage of each embodiment is low and the increase in driving voltage is small. This can be understood as follows: Compared with compounds 13 to 19, compounds 1 to 12 represented by the general formula (1) have strong interactions such as coordination with alkali metal elements and rare earth metal elements, and the charge generation efficiency and electron transport properties are increased, so the carrier balance is stable and the voltage increase during driving can be suppressed.

[0309] In addition, the results of single-charged elements containing the compound represented by the general formula (1) and Yb as a rare earth metal element are shown in Examples 1 to 15, and the results of single-charged elements containing Li as an alkali metal element instead of Yb are shown in Examples 16 to 27. From these results, it can be understood that the compound represented by the general formula (1) forms a stable layer with less increase in driving voltage by using it together with a rare earth metal element.

[0310] In addition, Examples 28 to 54 show the results of applying the organic layer used in Examples 1 to 27 to a light-emitting element. On the other hand, Comparative Examples 17 to 32 show the results of applying the organic layer used in Comparative Examples 1 to 16 to a light-emitting element. Compared with the comparative examples, the driving voltage of each embodiment is low, the external quantum efficiency is high, the durability is improved, and the driving voltage rise is small. It can be seen that, similar to the results of the single-charge element, the compound represented by the general formula (1) forms an efficient and more stable light-emitting element with less driving voltage rise.

[0311] In addition, the results of light-emitting elements containing the compound represented by the general formula (1) and Yb as a rare earth metal element are shown in Examples 28 to 42, and the results of light-emitting elements containing Li as an alkali metal element instead of Yb are shown in Examples 43 to 54. From these results, it can be understood that the compound represented by the general formula (1) forms a stable layer with less increase in driving voltage by using it together with a rare earth metal element.

[0312] In addition, Examples 55 to 81 show the results of applying the light-emitting elements used in Examples 28 to 54 to tandem light-emitting elements. On the other hand, Comparative Examples 33 to 48 show the results of applying the light-emitting elements used in Comparative Examples 17 to 32 to tandem light-emitting elements. Compared with the comparative examples, the driving voltage of each embodiment is low, the external quantum efficiency is high, the durability is improved, and the driving voltage rise is small. It can be seen that, similar to the results of the light-emitting elements used in Examples 28 to 54 and Comparative Examples 17 to 32, the compound represented by general formula (1) forms an efficient and more stable tandem light-emitting element with less driving voltage rise.

[0313] In addition, the results of tandem light-emitting devices containing the compound represented by the general formula (1) and Yb as a rare earth metal element are shown in Examples 55 to 69, and the results of tandem light-emitting devices containing Li as an alkali metal element instead of Yb are shown in Examples 70 to 81. From these results, it can be understood that the compound represented by the general formula (1) forms a stable layer with less increase in driving voltage by using it together with a rare earth metal element.

Claims

1. A compound represented by the following general formula (1), [Chemical formula 1] In the general formula (1), R 1 , R 2 and R 5 ~R 8 are each independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group, R 3 and R 4 is a carbon atom with a substituent, R 3 and R 4 They may be bonded to each other, and L is an unsubstituted arylene group having 6 to 20 carbon atoms.

2. The compound according to claim 1, wherein In the general formula (1), R 1 , R 2 , R 5 and R 6 are hydrogen atoms respectively.

3. The compound according to claim 1, wherein In the general formula (1), R 7 is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

4. The compound according to claim 1, wherein In the general formula (1), R 3 With R 4 bonded to each other.

5. A light-emitting element, comprising at least an electron transport layer and a light-emitting layer between an anode and a cathode, and emitting light using electrical energy, wherein the electron transport layer contains the compound according to any one of claims 1 to 4.

6. The light emitting element according to claim 5, wherein The electron transport layer further contains a complex of an alkali metal and an organic substance.

7. A light-emitting element comprising at least a charge generation layer and a light-emitting layer between an anode and a cathode, and emitting light using electrical energy, wherein the charge generation layer contains the compound according to any one of claims 1 to 4.

8. The light emitting element according to claim 7, wherein The charge generating layer further contains a phenanthroline dimer.

9. The light emitting element according to claim 7, wherein: The charge generating layer further contains alkali metal atoms or rare earth metal atoms.

10. The light emitting element according to claim 7, wherein The charge generation layer further contains an alkali metal atom, and the alkali metal atom is Li.

11. The light emitting element according to claim 7, wherein The charge generation layer further contains rare earth metal atoms, and the rare earth metal atoms are Yb.

12. A light-emitting element comprising at least an electron injection layer and a light-emitting layer between an anode and a cathode, and emitting light using electrical energy, wherein the electron injection layer contains the compound according to any one of claims 1 to 4.

13. The light emitting element according to claim 12, wherein: The electron injection layer further contains alkali metal atoms or rare earth metal atoms.

14. A display device comprising a light-emitting element containing the compound according to any one of claims 1 to 4.

15. A lighting device comprising a light-emitting element comprising the compound according to any one of claims 1 to 4.

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