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  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
  • C07F9/6564—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having phosphorus atoms, with or without nitrogen, oxygen, sulfur, selenium or tellurium atoms, as ring hetero atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
  • C07F9/6564—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having phosphorus atoms, with or without nitrogen, oxygen, sulfur, selenium or tellurium atoms, as ring hetero atoms
  • C07F9/6568—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having phosphorus atoms, with or without nitrogen, oxygen, sulfur, selenium or tellurium atoms, as ring hetero atoms having phosphorus atoms as the only ring hetero atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
  • C07F9/6564—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having phosphorus atoms, with or without nitrogen, oxygen, sulfur, selenium or tellurium atoms, as ring hetero atoms
  • C07F9/6571—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having phosphorus atoms, with or without nitrogen, oxygen, sulfur, selenium or tellurium atoms, as ring hetero atoms having phosphorus and oxygen atoms as the only ring hetero atoms
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  • C09K11/00—Luminescent materials, e.g. electroluminescent or chemiluminescent
  • C09K11/06—Luminescent materials, e.g. electroluminescent or chemiluminescent containing organic luminescent materials
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
  • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
  • H10K50/14—Carrier transporting layers
  • H10K50/16—Electron transporting layers
  • H10K50/165—Electron transporting layers comprising dopants
• • H—ELECTRICITY
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  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
  • H10K50/17—Carrier injection layers
• • H—ELECTRICITY
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  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
  • H10K50/19—Tandem OLEDs
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/10—OLED displays
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/30—Coordination compounds
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/60—Organic compounds having low molecular weight

Definitions

• the present invention relates to a compound, an organic EL element, a display device, and a lighting device that use the compound.
• organic EL elements have been steadily put to practical use, including their use in television and smartphone displays.
• existing organic EL elements still have many technical challenges.
• One of the biggest challenges is achieving both highly efficient light emission and a long lifespan for organic EL elements.
• dibenzophosphole oxide derivatives having a dibenzophosphole oxide skeleton and substituted with specific heteroaryl groups see, for example, Patent Document 1
• dibenzophosphole oxide derivatives substituted with specific aryl groups having crosslinking sites see Patent Document 2
• dibenzophosphole oxide derivatives having an anthracene skeleton see Patent Document 3
• dibenzophosphole oxide derivatives substituted with phenylene groups and biphenyl groups see Patent Document 4
• dibenzophosphole oxide derivatives having specific arylene groups and triazine skeletons see Patent Documents 5 and 6).
• the present invention aims to provide an organic EL element with excellent luminous efficiency and durability.
• X 1 is C-R 1 or a nitrogen atom
• X 2 is C-R 8 or a nitrogen atom
• R 1 to R 8 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, an alkoxy group, a phosphoryl group, a halogen atom, a cyano group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group
• at least one of R 1 to R 8 is a group represented by the following general formula (2).
• R 9 is a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
• L 1 is a linking group selected from a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted pyridylene group, a substituted or unsubstituted pyridazylene group, a substituted or unsubstituted pyrazylene group, and a substituted or unsubstituted pyrimidylene group;
• L 2 is a linking group selected from a single bond, a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted pyridylene group, a substituted or unsubstituted pyridazylene group, a substituted or unsubstituted pyrazylene group, and a substituted or unsubstituted pyrimidylene group.
• A is an unsubstituted condensed polycyclic aromatic hydrocarbon group or a substituted or unsubstituted heteroaryl group having two or less nitrogen atoms.
• a in the general formula (2) is a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidyl group, a substituted or unsubstituted pyridazyl group, a substituted or unsubstituted pyrrole group, a substituted or unsubstituted pyrazolyl group, a substituted or unsubstituted imidazolyl group, a substituted or unsubstituted benzimidazolyl group, a substituted or unsubstituted quinolinyl group, a substituted or unsubstituted isoquinolinyl group, a substituted or unsubstituted quinoxalinyl group, a substituted
• An organic EL element which emits light by electrical energy comprising at least an electron transport layer and a light emitting layer between an anode and a cathode, wherein the electron transport layer contains the compound according to any one of [1] to [4].
• An organic EL element which emits light by electrical energy comprising at least a charge generating layer and a light emitting layer between an anode and a cathode, wherein the charge generating layer contains the compound according to any one of [1] to [4].
• 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;
• Z1 and Z2 are each independently an oxygen atom, NRa (a nitrogen atom having a substituent Ra) or a sulfur atom, and when Z1 is NRa, it may or may not be bonded to ring A or ring B 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;
• the present invention makes it possible to provide an organic EL element with excellent luminous efficiency and durability.
• X 1 is C-R 1 or a nitrogen atom
• X 2 is C-R 8 or a nitrogen atom
• R 1 to R 8 are each independently selected from the group consisting of a hydrogen atom, an alkyl group, an alkoxy group, a phosphoryl group, a halogen atom, a cyano group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group
• at least one of R 1 to R 8 is a group represented by the following general formula (2).
• R 9 is a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
• L 1 is a linking group selected from a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted pyridylene group, a substituted or unsubstituted pyridazylene group, a substituted or unsubstituted pyrazylene group, and a substituted or unsubstituted pyrimidylene group;
• L 2 is selected from a single bond, a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted pyridylene group, a substituted or unsubstituted pyridazylene group, a substituted or unsubstituted pyrazylene group, and a substituted or unsubstituted pyrimidylene group.
• A is an unsubstit
• unsubstituted means that hydrogen atoms are bonded, and “substituted” means that at least some of the hydrogen atoms have been replaced.
• hydrogen atoms may be deuterium atoms.
• substituted or unsubstituted in the compounds or partial structures described below.
• 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, which may or may not have a substituent.
• the number of carbon atoms in the alkyl group is not particularly limited, but from the standpoint of ease of availability and cost, it is preferably in the range of 1 to 20, more preferably 1 to 8.
• the number of carbon atoms here includes the number of carbon atoms contained in the substituent bonded to the alkyl group, and the same applies to other substituents that specify the number of carbon atoms.
• An alkoxy group refers to a group in which an alkyl group is bonded to oxygen, such as a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, or a tert-butoxy group, which may or may not have a substituent.
• the number of carbon atoms in an alkoxy group is not particularly limited, but from the standpoint of ease of availability and cost, it is usually in the range of 1 to 20, more preferably 1 to 8.
• 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 benzoanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzoanthracenyl group, a perylenyl group, or a helicenyl group. This may or may not have a substituent. Of these, a phenyl group or a biphenyl group is preferred.
• Heteroaryl groups include, for example, pyridyl groups, pyrrole groups, furanyl groups, thiophenyl groups, quinolinyl groups, isoquinolinyl groups, pyrazinyl groups, pyrimidyl groups, pyridazinyl groups, triazinyl groups, naphthyridinyl groups, cinnolinyl groups, phthalazinyl groups, quinoxalinyl groups, quinazolinyl groups, benzofuranyl groups, benzothiophenyl groups, indolyl groups, dibenzofuranyl groups, dibenzothiophenyl groups, benzophosphole groups, benzophosphole oxide groups, dibenzophosphole groups, dibenzophosphole groups, dibenzophosphole groups, dibenzophosphole groups, It refers to a cyclic aromatic group having one or more atoms other than carbon in the ring, such as a peroxide group, a carbazolyl
• Patent Documents 1 to 5 disclose compounds U, V, W, X, Y, and Z represented by the following formulas.
• dibenzophosphole oxide derivatives with a triazine skeleton such as compounds U and V
• Dibenzophosphole oxide derivatives with substituted anthryl groups such as compounds W and X, have a large twisted structure due to the bulky nature of the anthryl group, making it difficult for the groups on either side of the anthryl group to conjugate. This results in reduced charge transport properties, higher driving voltages, and issues with luminous efficiency and durability.
• Dibenzophosphole derivatives with phenylene and biphenyl groups, such as compound Y have groups with short conjugation lengths, which reduces charge transport properties, increases driving voltage, and creates problems with luminous efficiency and durability.
• Dibenzophosphole derivatives with crosslinking sites and specific aryls, such as compound Z have small intermolecular interactions due to the bulkiness of the crosslinking sites, which reduces charge transport properties, resulting in high driving voltages and problems with luminous efficiency and durability.
• the compound represented by general formula (1) can improve its charge transport properties by including at least one group represented by general formula (2).
• L 1 is selected from a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted pyridylene group, a substituted or unsubstituted pyridazylene group, a substituted or unsubstituted pyrazylene group, and a substituted or unsubstituted pyrimidylene group; and L 2 is selected from a single bond, a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted pyridylene group, a substituted or unsubstituted pyridazylene group, a substituted or unsubstituted pyrazylene group, and a substituted or unsubstituted pyrimidylene group.
• L 1 is a phenylene group or a naphthylene group.
• L 2 is a single bond, it is more preferable because it can increase the interaction between the dibenzophosphole skeleton and the group represented by general formula (2), and can further improve the luminous efficiency and durable life.
• A is an unsubstituted condensed polycyclic aromatic hydrocarbon group or a substituted or unsubstituted heteroaryl group having two or less nitrogen atoms.
• the glass transition temperature of the compound is improved and the electron transport properties are also improved. Therefore, when the compound represented by general formula (1) is used in a light-emitting device, the driving voltage is further reduced and the light-emitting efficiency and durability can be further improved, which is preferable.
• A is an unsubstituted condensed polycyclic aromatic hydrocarbon group
• the number of ring-forming atoms in A is not particularly limited, but is preferably in the range of 15 to 40, more preferably 15 to 30. From the viewpoint of further improving the stability, luminous efficiency, and durability of the organic EL element, it is more preferable that A is a pyrenyl group, a fluoranthenyl group, a phenanthrenyl group, or a fluorenyl group.
• A is a substituted or unsubstituted heteroaryl group having two or less nitrogen atoms
• the glass transition temperature of the compound is improved, and excessive improvement in crystallinity is suppressed, providing good film quality stability. Therefore, when the compound represented by general formula (1) is used in a light-emitting device, the driving voltage can be reduced, and the light-emitting efficiency and durability can be improved.
• X 1 in the general formula (1) is C-R 1 or a nitrogen atom
• X 2 is C-R 8 or a nitrogen atom.
• X 1 in the general formula (1) is C-R 1 or a nitrogen atom
• X 2 is C-R 8 or a nitrogen atom.
• A when A is a heteroaryl group, A is preferably a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidyl group, a substituted or unsubstituted pyridazyl group, a substituted or unsubstituted pyrrole group, a substituted or unsubstituted pyrazolyl group, a substituted or unsubstituted imidazolyl group, a substituted or unsubstituted benzimidazolyl group, a substituted or unsubstituted quinolinyl group, a substituted or unsubstituted isoquinolinyl group, a substituted or unsubstituted quinoxalinyl group, a substituted or unsubstituted quinazolyl group, a substituted or unsubstituted acridinyl group, a substituted or unsubsti
• the electron transport properties of the entire compound are improved, and when the compound represented by the general formula (1) is used in a light-emitting device, the driving voltage can be further reduced, and the light-emitting efficiency and durability can be further improved.
• A is more preferably a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidyl group, a substituted or unsubstituted pyridazyl group, a substituted or unsubstituted benzimidazolyl group, a substituted or unsubstituted quinolinyl group, a substituted or unsubstituted isoquinolinyl group, a substituted or unsubstituted quinoxalinyl group, a substituted or unsubstituted quinazolyl group, a substituted or unsubstituted acridinyl group, a substituted or unsubstituted naphthazinyl group, a substituted or unsubstituted phenazinyl group, or a substituted or unsubstituted phen
• A is a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidyl group, a substituted or unsubstituted pyridazyl group, a substituted or unsubstituted benzimidazolyl group, or a substituted or unsubstituted phenanthrolyl group.
• the number of ring carbon atoms in A is not particularly limited, but is preferably in the range of 15 to 40, more preferably 15 to 30.
• A is a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted dibenzothiophenyl group, or a substituted or unsubstituted dibenzophosphoryloxide group.
• A is a substituted or unsubstituted dibenzophosphoryloxide group.
• R 1 to R 8 those which are not groups represented by general formula (2) are selected from the group consisting of a hydrogen atom, a methyl group, and a phenyl group. Also, from the viewpoint of improving the film quality stability and further improving the durability life of the light-emitting element, it is more preferable that among R 1 to R 8 , those which are not groups represented by general formula (2) are hydrogen atoms. Particularly preferably, among R 1 to R 8 , either R 2 or R 7 is a substituent represented by general formula (2), and the rest are all hydrogen atoms.
• R9 is a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, in which case the highly reactive phosphorus atom in the dibenzophosphole skeleton is substituted, improving the stability of the compound. From the viewpoint of improving the film stability and further improving the durability of the light-emitting element, R9 is more preferably a phenyl group.
• the molecular weight of the compound represented by general formula (1) is preferably 400 or more from the viewpoint of suppressing crystallization and improving the stability of the film quality. On the other hand, from the viewpoint of improving processability during sublimation purification and deposition, the molecular weight of the compound represented by general formula (1) is preferably 800 or less.
• Examples of compounds represented by general formula (1) include the compounds shown below. Note that the following are merely examples, and compounds other than those specified here can also be used preferably as long as they are represented by general formula (1).
• the compound represented by the general formula (1) can be synthesized by a known synthesis method.
• the synthesis method may be a coupling reaction between an aryl halide derivative and an arylboronic acid derivative using palladium, but is not limited to this.
• the compound represented by general formula (1) is preferably used in any of the layers of the light-emitting device.
• the compound represented by general formula (1) is preferably used as a material for the hole injection layer, hole transport layer, light-emitting layer, electron transport layer, protective film (cap layer) of the electrode, and the like in the light-emitting device.
• the material represented by general formula (1) in any of the layers of the light-emitting device, it is possible to provide a light-emitting device with excellent light-emitting efficiency and durability.
• 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 when exposed to electrical energy.
• a light-emitting element may be referred to as an "organic EL element.”
• the layer configuration of the organic layer between the anode and cathode can be, in addition to a configuration in which the organic layer is composed only of the light-emitting layer, stacked configurations such as 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.
• the organic EL element may be of a tandem type in which a plurality of organic layers having the above-mentioned laminated structure are laminated with an intermediate layer interposed therebetween.
• 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 may be made of a known material.
• 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.
• each of the above layers may be a single layer or multiple layers, and may be doped.
• the electron injection layer and the charge generation layer are preferably metal-doped layers doped with a metal, which can improve the electron transport ability and the electron injection ability to adjacent layers.
• a protective layer (cap layer) may be further provided, which can further improve the light-emitting efficiency by the optical interference effect.
• the compound represented by the general formula (1) may be used in any of the above layers in the organic EL element, but is particularly suitable for use in the electron transport layer, charge generation layer, or electron injection layer.
• the organic EL element As the organic EL element according to the embodiment of the present invention, a configuration in which at least an electron transport layer and a light-emitting layer are present between the anode and the cathode, and the electron transport layer contains a compound represented by the general formula (1), a configuration in which at least a charge generation layer and a light-emitting layer are present between the anode and the cathode, and the charge generation layer contains a compound represented by the general formula (1), and a configuration in which at least an electron injection layer and a light-emitting layer are present between the anode and the cathode, and the electron injection layer contains a compound represented by the general formula (1) are listed as preferred configurations.
• the anode and cathode serve to supply 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.
• the anode formed on the substrate is a transparent electrode.
• the organic EL element In order to maintain the mechanical strength of the organic EL element, it is preferable to form the organic EL element on a substrate.
• the substrate include glass substrates such as soda glass and non-alkali 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.
• the glass material it is preferable that the amount of ions eluted from the glass is small, and non-alkali glass is preferable.
• soda lime glass with a barrier coat such as SiO2 is also commercially available, and this can also be used.
• the material used for 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 semi-transparent.
• 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 or NESA glass is preferable. These electrode materials may be used alone, or a plurality of materials may be laminated or mixed. In addition, the thickness of the anode can be selected arbitrarily according to the resistance value, and is usually used between 45 and 300 nm.
• the material used for the cathode is not particularly limited as long as it can efficiently inject electrons into the light-emitting layer.
• materials used for the cathode include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, or alloys of these metals with low work function metals such as lithium, sodium, potassium, calcium, and magnesium, and multi-layer laminates of these metals.
• metals selected from aluminum, silver, and magnesium are preferred as the main component in terms of electrical resistance value, ease of film formation, film stability, and light-emitting efficiency, and it is more preferred to be composed of magnesium and silver because electrons are easily injected into the electron transport layer and electron injection layer.
• the thickness of the cathode can be selected arbitrarily according to the resistance value, and is usually used in the range of 45 to 300 nm.
• the material (capping material) constituting the protective layer 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, organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride and hydrocarbon polymer compounds.
• a compound represented by the general formula (1) can also be used as a capping material.
• the organic EL element has an element structure (top emission structure) in which light is extracted from the cathode side, it is preferable that the capping material has optical transparency in the visible light region.
• the hole injection layer is a layer inserted between the anode and the hole transport layer.
• the hole injection layer may be either a single layer or a laminate of multiple layers. If the hole injection layer is present between the hole transport layer and the anode, not only can the device be driven at a lower voltage and have an improved durability, but also the carrier balance of the device can be improved, which is preferable because the light emitting efficiency can be improved.
• the hole injection layer may be made of any known material.
• the materials may be used alone or in combination of two or more materials.
• a plurality of materials may be laminated to form a hole injection layer.
• the hole injection layer is composed of an acceptor compound alone or that the hole injection material as described above is doped with an acceptor compound, since the above-mentioned effects are more pronounced.
• the acceptor compound is a material that forms a charge transfer complex with the hole transport layer in contact with it when used as a single layer film, or with the material that constitutes the hole injection layer when used as a doped film. The use of such a material improves the conductivity of the hole injection layer, contributing to a reduction in the driving voltage of the device and further improving the luminous efficiency and durability.
• any known material 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, fullerenes, etc.
• metal oxides and compounds containing a cyano group are preferred because they are easy to handle and vapor-deposit, and therefore the above-mentioned effects can be easily obtained.
• the hole injection layer may be a single layer or may be composed of multiple layers stacked together.
• 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 a laminate of multiple layers.
• Materials used in the hole transport layer include those exemplified as materials used in the hole injection layer. From the viewpoint of smoothly injecting and transporting holes to the light-emitting layer, triarylamine derivatives or benzidine derivatives are more preferable.
• the light-emitting layer may be a single layer or multiple layers, and is formed of a light-emitting material.
• the light-emitting material may be a mixture of a host material and a dopant material, a host material alone, or a mixture of two types of host materials and one type of dopant material. That is, in the organic EL device according to the embodiment of the present invention, in each light-emitting layer, only the host material or the dopant material may emit light, or both the host material and the dopant material may emit light.
• the light-emitting layer is made of a mixture of a host material and a dopant material.
• the host material and the dopant material may each be one type or a combination of multiple types.
• the dopant material When a mixture of a host material and a dopant material is used, the dopant material may be contained entirely or partially in the host material.
• the dopant material may be either laminated or dispersed.
• the dopant material can control the emitted color. From the viewpoint of suppressing the concentration quenching phenomenon, the amount of the dopant material is preferably 30% by weight or less relative to the host material, and more preferably 20% by weight or less.
• the doping method can be formed by co-evaporation with the host material, but it may also be mixed with the host material in advance and then evaporated at the same time.
• the luminescent material may be any known material. Examples include condensed ring derivatives such as anthracene and pyrene, which are known as luminescent bodies; metal chelated oxinoid compounds such as tris(8-quinolinolato)aluminum; bisstyryl derivatives such as bisstyryl anthracene derivatives and distyrylbenzene derivatives; tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, oxadiazole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, and polymers such as polyphenylenevinylene derivatives, polyparaphenylene derivatives, and polythiophene derivatives.
• condensed ring derivatives such as anthracene and
• the host material contained in the light-emitting material does not have to be limited to only one type of compound, and a mixture of multiple compounds may be used. Also, they may be laminated.
• Known materials can be used as the host material. Examples include, but are not limited to, compounds having condensed aryl rings 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
• metal chelated oxinoid compounds dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, and triphenylene derivatives are preferably used as hosts when the light-emitting layer emits triplet light (phosphorescence).
• the dopant material contained in the light-emitting material includes, for example, compounds having an aryl ring or derivatives thereof, compounds having a heteroaryl ring or 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).
• dopants containing a diamine skeleton and dopants containing a fluoranthene skeleton can further improve the light-emitting efficiency.
• the compound represented by the following general formula (3) can further improve the light-emitting efficiency and durability, so it is particularly preferable that the light-emitting layer contains the compound represented by the following general formula (3).
• the Za ring, the Zb ring and the 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.
• the Za ring, the Zb ring and the Zc ring are each independently preferably 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.
• 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 2 are both NRa, and Ra is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
• 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.
• 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, 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 sulfonic acid ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, or an oxo group.Furthermore, these substituent
• alkyl group, alkoxy group, aryl group, and heteroaryl group include those exemplified as the substituents in general formula (1).
• Cycloalkyl groups refer to saturated alicyclic hydrocarbon groups such as cyclopropyl, cyclohexyl, norbornyl, and adamantyl groups, which may or may not have a substituent. There are no particular limitations on the number of ring carbon atoms, but it is preferably in the range of 3 to 20.
• the heterocyclic group refers to an aliphatic ring having atoms other than carbon within 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-forming atoms is not particularly limited, but is preferably in the range of 3 to 20.
• 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.
• Cycloalkenyl groups refer to unsaturated alicyclic hydrocarbon groups containing a double bond, such as cyclopentenyl groups, cyclopentadienyl groups, and cyclohexenyl groups, which may or may not have a substituent.
• 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.
• a substituted phenyl group when the phenyl group has a substituent on each of two adjacent carbon atoms, the substituents may form a ring structure together.
• the resulting group may fall into one or more of the following categories: 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.”
• 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.
• An aryl ether group is 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.
• An aryl thioether group refers to a functional group in which the oxygen atom of the ether bond of an aryl ether group is replaced 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.
• Halogen refers to fluorine, chlorine, bromine or iodine.
• An 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.
• the ester group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group 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.
• 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.
• An amide group refers to a functional group in which, for example, an alkyl group, a cycloalkyl group, an aryl group, or a heteroaryl group 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 methylamide groups, ethylamide groups, propylamide groups, butylamide groups, isopropylamide groups, hexylamide groups, and phenylamide groups.
• the number of carbon atoms in the sulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.
• 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.
• the number of carbon atoms in the sulfonate ester group is not particularly limited, but is preferably in the range of 1 to 20.
• 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.
• the number of carbon atoms in the sulfonamide group is not particularly limited, but is preferably in the range of 1 to 20.
• 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.
• silyl group refers to a functional group to which a substituted or unsubstituted silicon atom is bonded, and includes, for example, 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. There are no particular limitations on the number of carbon atoms in the silyl group, but it is preferably in the range of 1 to 30.
• the siloxanyl group refers to a silicon compound group via an ether bond, such as a trimethylsiloxanyl group.
• the siloxanyl group may or may not have a substituent.
• the boryl group may or may not have a substituent.
• Examples of compounds represented by general formula (3) include the following:
• the light-emitting layer contains a triplet light-emitting material.
• 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, it is not limited to these, and an appropriate complex is selected based on the required light emission color, device performance, and relationship with the host compound.
• tris(2-phenylpyridyl)iridium complex tris ⁇ 2-(2-thiophenyl)pyridyl ⁇ iridium complex, tris ⁇ 2-(2-benzothiophenyl)pyridyl ⁇ iridium complex, tris(2-phenylbenzothiazole)iridium complex, tris(2-phenylbenzoxazole)iridium complex, trisbenzoquinolineiridium complex, bis(2-phenylpyridyl)(acetylacetonate)iridium complex, bis ⁇ 2-(2-thiophenyl)pyridyl ⁇ iridium complex, bis ⁇ 2-(2-benzothiophenyl)pyridyl ⁇ (acetylacetonate)iridium complex, bis(2-phenylbenzothiazole)(acetylacetonate)iridium complex, bis(2-phenylbenzothiazole)(acetylacetonate)iridium complex, -phenylbenz
• the triplet light-emitting materials used as dopant materials may each be contained in the light-emitting layer alone or in a mixture of two or more kinds.
• the total weight of the dopant materials is preferably 30% by weight or less, more preferably 20% by weight or less, relative to the host material.
• Preferred hosts and dopants in triplet light-emitting systems are not particularly limited, but specific examples include the following:
• the light-emitting layer contains a thermally activated delayed fluorescent material.
• TADF thermally activated delayed fluorescence
• Thermal activated delayed fluorescent materials are generally also called TADF materials.
• the thermally activated delayed fluorescent material may be a material that exhibits thermally activated delayed fluorescence from a single material, or may be a material that exhibits thermally activated delayed fluorescence from multiple materials. When multiple materials are used, they may be used as a mixture, or layers made of each material may be laminated.
• Known materials can be used as thermally activated delayed fluorescent 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.
• the light-emitting layer also contains a fluorescent dopant. This is because the TADF material converts triplet excitons into singlet excitons, and the fluorescent dopant receives the singlet excitons, thereby achieving higher luminous efficiency and longer durability.
• the electron transport layer is a layer into which electrons are injected from the cathode and which transports the electrons. It is desired that the electron transport layer has a high electron injection efficiency and efficiently transports the injected electrons. Therefore, it is preferable that the material constituting the electron transport layer is a substance that has a large electron affinity, a large electron mobility, is excellent in stability, and is unlikely to generate impurities that become traps during production and use. In particular, when the film thickness is thickly laminated, low molecular weight compounds tend to deteriorate the film quality due to crystallization, etc., so in order to maintain stable film quality, compounds with a molecular weight of 400 or more are preferable.
• 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 composed of a single material or a plurality of materials laminated together.
• the electron transport material used in the electron transport layer can be any known material. 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. It is preferable to use a compound that is composed of an element selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus and has a heteroaryl ring structure containing electron-accepting nitrogen, because this further reduces the driving voltage and provides more efficient light emission.
• the electron-accepting nitrogen referred to here refers to a nitrogen atom that forms a multiple bond with an adjacent atom. Since the nitrogen atom has high electronegativity, the multiple bond has electron-accepting properties. Therefore, an aromatic heterocycle containing electron-accepting nitrogen has high electron affinity.
• An electron transport material containing electron-accepting nitrogen can easily accept electrons from a cathode with high electron affinity, making it possible to operate at a lower voltage. In addition, the supply of electrons to the light-emitting layer increases, increasing the probability of recombination, thereby further improving the luminous efficiency.
• heteroaryl rings containing an electron-accepting nitrogen examples 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.
• Examples of compounds having these heteroaryl ring structures include pyridine derivatives, triazine derivatives, quinazoline derivatives, pyrimidine derivatives, benzimidazole derivatives, benzoxazole derivatives, benzothiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives, quinoxaline derivatives, and naphthyridine derivatives.
• compounds selected from 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.
• the glass transition temperature is improved and the electron mobility is increased, which makes it possible to further reduce the driving voltage of the organic EL element, which is preferable.
• the condensed polycyclic aromatic skeleton is a fluoranthene skeleton, anthracene skeleton, pyrene skeleton, or phenanthroline skeleton.
• Preferred electron transport materials are not particularly limited, but specific examples include the following:
• the compound represented by the above general formula (1) is also preferred because it has high electron transport properties and exhibits excellent properties as an electron transport layer.
• the above electron transport material may be used alone, or two or more of the above electron transport materials may be mixed, or one or more other electron transport materials may be mixed with the above electron transport material.
• the electron transport layer may contain a donor material in addition to the above electron transport material, preferably the compound represented by general formula (1).
• the donor material is a compound that improves the electron injection barrier, thereby facilitating the injection of electrons from the cathode or the electron injection layer into the electron transport layer, and further improves the electrical conductivity of the electron transport layer.
• Preferred examples of donor materials include alkali metals, inorganic salts containing alkali metals, complexes of alkali metals and organic substances, alkaline earth metals, inorganic salts containing alkaline earth metals or complexes of alkaline earth metals and organic substances, rare earth metals, and simple substances of Group 11 elements.
• Preferred examples of alkali metals and rare earth metals include lithium and ytterbium, which have a low work function and are highly effective in improving electron transport ability. A plurality of these metals may be used, and an alloy made of these metals may also be used.
• the metal is in the form of an inorganic salt or a complex with an organic substance rather than a simple metal. Furthermore, it is more preferable that the metal is in the form of a complex with an organic substance, since it is easier to handle in the atmosphere and the concentration added can be easily adjusted.
• inorganic salts include oxides, nitrides, fluorides, and carbonates.
• alkali metals or alkaline earth metals include lithium and cesium.
• preferred examples of organic substances in complexes with organic substances include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole.
• complexes of an alkali metal, a rare earth metal or an alkali metal and an organic substance are preferred, and complexes of an alkali metal and an organic substance are more preferred.
• complexes of lithium and an organic substance are more preferred, and lithium quinolinol (Liq), which is relatively inexpensive and available, is particularly preferred.
• the ionization potential of the electron transport layer is not particularly limited, but is preferably 5.6 eV or more and 8.0 eV or less, and more preferably 5.6 eV or more and 7.0 eV or less.
• an electron injection layer may be provided between the cathode and the electron transport layer.
• the electron injection layer is inserted for the purpose of helping the injection of electrons from the cathode to the electron transport layer.
• a compound having a heteroaryl ring structure containing an electron-accepting nitrogen may be used, or a layer containing the above-mentioned donor material may be used.
• inorganic insulators or semiconductors 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.
• 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.
• complexes of organic substances and metals are also suitable for use.
• a complex of organic substances and metals is used in the electron injection layer, the film thickness can be easily adjusted.
• Preferred examples of organic substances in organometallic complexes include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole.
• a layer containing a compound represented by the above general formula (1) also has high electron injection properties and is preferable because it exhibits excellent properties as an electron injection layer.
• the compound represented by the general formula (1) is preferably doped with the above alkali metal or rare earth metal, which can further reduce the driving voltage and further improve the durability life.
• the electron injection layer preferably contains an alkali metal or a rare earth metal in addition to the compound represented by formula (1).
• alkali metals and rare earth metals include alkali metals such as lithium, sodium, potassium, rubidium, and cesium, which have a low work function and are highly effective in improving electron transport ability, and rare earth metals such as samarium, europium, and ytterbium. More preferred examples of alkali metals and rare earth metals include lithium and ytterbium, which can further reduce the driving voltage.
• the charge generating layer in the present invention generally consists of a double layer, and specifically, can be used as a pn junction charge generating layer formed by laminating an n-type charge generating layer and a p-type charge generating layer.
• the pn junction charge generating layer generates charges or separates charges into holes and electrons by applying a voltage in the organic EL element, and injects these holes and electrons into the light emitting layer via the hole transport layer and the electron transport layer.
• an organic EL element having a plurality of light emitting layers it functions as a charge generating layer of an intermediate layer.
• the n-type charge generating layer supplies electrons to the first light emitting layer present on the anode side, and the p-type charge generating layer supplies holes to the second light emitting layer present on the cathode side. Therefore, the light emitting efficiency of an organic EL element having a plurality of light emitting layers laminated can be further improved, the driving voltage can be reduced, and the durability life of the element can be further improved.
• the n-type charge generating layer is composed of an n-type dopant and a host, and conventional materials can be used for these.
• an alkali metal, an alkaline earth metal, a rare earth metal, or a simple substance of a Group 11 element can be used as the n-type dopant.
• a compound having a nitrogen-containing aromatic heterocycle such as a phenanthroline derivative or an oligopyridine derivative, can be used as the host.
• the compound represented by the above general formula (1) and the phenanthroline derivative are preferred because they exhibit excellent properties as a host for the n-type charge generating layer.
• the layer further contains a phenanthroline derivative in addition to the compound represented by general formula (1).
• a phenanthroline derivative include the following compounds.
• the charge generating layer further contains an alkali metal or a rare earth metal in addition to the compound represented by general formula (1).
• the alkali metal Li is particularly preferable.
• the rare earth metal Yb is particularly preferable.
• a configuration that further contains a phenanthroline derivative and an alkali metal or a rare earth metal in addition to the compound represented by general formula (1) is also preferred.
• the p-type charge generating layer is composed of a p-type dopant and a host, and conventional materials can be used for these.
• a p-type dopant for example, tetrafluorene-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl 3 , FeF 3 , SbCl 5 , etc. can be used as the p-type dopant.
• a preferred p-type dopant is a radialene derivative.
• a preferred host is an arylamine derivative.
• the thickness of the organic layer interposed between the anode and cathode cannot be limited because it depends on the resistance value of the light-emitting material, but it is preferable that the total thickness is 1 to 1000 nm.
• the thickness of each layer constituting the organic layer is preferably 1 nm or more and 200 nm or less, and more preferably 5 nm or more and 100 nm or less.
• each of the layers constituting the organic EL element is not particularly limited and may include resistance heating deposition, electron beam deposition, sputtering, molecular lamination, coating, etc., but resistance heating deposition or electron beam deposition is usually preferred in terms of element characteristics.
• the organic EL element according to the embodiment of the present invention has the function of converting electrical energy into light.
• DC current is mainly used as the electrical energy, but pulse current or AC current can also be used.
• the organic EL element 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 format.
• 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, automotive panels, display boards, signs, and the like.
• the organic EL element of the present invention is preferably used as a backlight for liquid crystal displays, particularly for personal computers, where thinner displays are being considered, and can provide a backlight that is thinner and lighter than conventional ones.
• the organic EL element according to the embodiment of the present invention is also preferably used as various lighting devices.
• the organic EL element according to the embodiment of the present invention is capable of achieving both high luminous efficiency and high color purity, and can also be made thin and lightweight, making it possible to realize a lighting device that combines low power consumption, vivid luminous color, and high designability.
• Synthesis Example 1 Synthesis of Compound 5 A mixed solution of 1.2 g of 3-chloro-5-phenyldibenzophosphole oxide, 2.0 g of boronic acid ester A, 33 mg of dichlorobis(triphenylphosphinepalladium) dichloride, 6 ml of 2.0 M potassium phosphate aqueous solution, and 39 ml of dimethoxyethane was heated and stirred under reflux for 2 hours under a nitrogen stream. After cooling to room temperature, water was added and filtration was performed, and the obtained solid was washed with methanol and dried in vacuum. The obtained solid was dissolved in toluene, and the catalyst was removed using activated carbon. The solid obtained by removing the solvent by evaporation was recrystallized with toluene and then dried in vacuum to obtain 1.0 g of Compound 5.
• the obtained compound 5 was subjected to sublimation purification using an oil diffusion pump at about 320° C. under a pressure of 1 ⁇ 10 ⁇ 3 Pa.
• the HPLC purity (area % at a measurement wavelength of 254 nm) of compound 5 before and after the sublimation purification was both 99.9%.
• Synthesis Example 2 Synthesis of Compound 14 A mixed solution of 0.75 g of 1,3-benzenediboronic acid, 1.5 g of 3-chloro-5-phenyldibenzophosphole oxide, 38 mg of dichlorobis(triphenylphosphinepalladium) dichloride, 4 ml of 2.0 M potassium phosphate aqueous solution, and 23 ml of dimethoxyethane was heated and stirred under reflux for 2 hours under a nitrogen stream. After cooling to room temperature, water was added and the mixture was filtered. The obtained solid was washed with hexane and dried in vacuum. The obtained solid was dissolved in toluene, and the catalyst was removed using activated carbon.
• the solid obtained by removing the solvent by evaporation was recrystallized in toluene and then dried in vacuum to obtain 1.4 g of Compound 14.
• the obtained compound 14 was subjected to sublimation purification using an oil diffusion pump at about 320° C. under a pressure of 1 ⁇ 10 ⁇ 3 Pa.
• the HPLC purity (area % at a measurement wavelength of 254 nm) of compound 7 before and after the sublimation purification was both 99.9%.
• the organic EL elements obtained in Examples 34 to 136 and Comparative Examples 13 to 48 were each driven at a current density of 10 mA/cm 2 to measure the initial driving voltage.
• Example 1 A glass substrate (manufactured by Geomatec Co., Ltd., 11 ⁇ / ⁇ , sputtered product) on which an ITO transparent conductive film was deposited to 165 nm as an anode was cut into 38 mm ⁇ 46 mm and etched. The obtained 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 UV-ozone treated for 1 hour immediately before fabricating the element, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus was 5 ⁇ 10 ⁇ 4 Pa or less.
• “Semicoclean” 56 trade name, manufactured by Furuuchi Chemical Co., Ltd.
• P-D1 was evaporated to 5 nm as a hole injection layer by resistance heating, and then HT-1 was evaporated to 50 nm as a hole transport layer.
• a mixed layer of a host material H-1 and a dopant material D-1 was evaporated to a thickness of 20 nm as a light-emitting layer so that the doping concentration was 5% by weight.
• ET-1 and 2E-1 were evaporated to a thickness of 35 nm such that the evaporation rate ratio of ET-1 and 2E-1 was 1:1.
• compound 1 and the metal element Li as a dopant were evaporated to a thickness of 10 nm such that the evaporation rate ratio of compound 1:Li was 99:1.
• aluminum was evaporated to a thickness of 60 nm to form a cathode, and an organic EL element measuring 5 mm ⁇ 5 mm square was produced.
• Examples 2 to 33, Comparative Examples 1 to 12 Elements were prepared in the same manner as in Example 1, except that the compounds used were changed as shown in Table 1. The results of each of the Examples and Comparative Examples are shown in Table 1. Compounds 2 to 33 are the compounds shown below.
• Example 34 A glass substrate (manufactured by Geomatec Co., Ltd., 11 ⁇ / ⁇ , sputtered product) on which an ITO transparent conductive film was deposited to 165 nm as an anode was cut into 38 mm ⁇ 46 mm and etched. The obtained 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 UV-ozone treated for 1 hour immediately before fabricating the element, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus was 5 ⁇ 10 ⁇ 4 Pa or less.
• P-D1 was vapor-deposited to a thickness of 5 nm as a hole injection layer by a resistance heating method.
• a light-emitting unit (first light-emitting unit) consisting of a hole transport layer, a light-emitting layer, and an electron transport layer was formed on the hole injection layer.
• HT-1 was evaporated to a thickness of 50 nm as a hole transport layer
• a mixed layer of host material H-1 and dopant material D-1 was evaporated to a thickness of 20 nm as an emitting layer with a doping concentration of 5% by weight
• a charge generation layer consisting of a laminated structure of an n-type charge generation layer and a p-type charge generation layer was formed on the first light-emitting unit.
• the initial driving voltage was 9.10 V
• the luminance was 1350 cd/m 2
• the durability life was 2010 hours.
• Examples 35 to 103, Comparative Examples 13 to 36 Organic EL devices were prepared in the same manner as in Example 34, except that the compounds, dopant materials, metal elements, and the deposition rate ratio of the compounds and metal elements used were changed as shown in Tables 2 and 3.
• Examples 56 and 91 a mixed layer of host material H-1 and dopant material D-2 was deposited as an emitting layer to a thickness of 20 nm such that the doping concentration was 5% by weight.
• D-2 and ET-2 are the compounds shown below.
• Example 104 An organic EL element was produced in the same manner as in Example 22, except that in forming the electron transport layer, compound 1 was used instead of ET-1, and in forming the n-type charge generation layer, compound ET-2 was used instead of ET-1.
• the initial driving voltage was 10.90 V
• the luminance was 1470 cd/m 2
• the durability life was 2160 hours.
• Examples 105 to 136, Comparative Examples 37 to 48 Organic EL devices were prepared in the same manner as in Example 104, except that the compounds used were changed as shown in Table 4. The results of each of the Examples and Comparative Examples are shown in Table 4.

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