Compound, hole-transporting material, and electroluminescent element

Abstract

Provided is a compound represented by formula (1). In formula (1), R1 and R2 each independently represent an (un)substituted C1-C20 alkyl group, an (un)substituted cycloalkyl group in which the number of ring-forming carbon atoms is 3-20, an (un)substituted C1-C20 heteroalkyl group, an (un)substituted C7-C30 aralkyl group, an (un)substituted C6-C30 aryl group, an (un)substituted C3-C30 heteroaryl group, or a combination of these, and X represents an oxygen atom or a sulfur atom.

Description

Compound, hole transport material, and electroluminescent device

[0001] The present invention relates to a compound, a hole transporting material, and an electroluminescent device.

[0002] Electroluminescent elements are self-luminous light-emitting elements that do not require a backlight, and are therefore attracting attention as a means for realizing a thin display device that can be driven with low power consumption.

[0003] In electroluminescent devices, holes injected from the anode and electrons injected from the cathode are recombined in the light-emitting layer to cause the light-emitting material contained in the light-emitting layer to emit light. Therefore, development of new charge-transporting materials that can be driven at low voltage and have a long life is underway.

[0004] For example, Patent Document 1 describes specific novel compounds, such as dehydrogenated benzobisoxazole, dehydrogenated benzobisthiazole, dehydrogenated benzobisselenazole, and compounds having structures similar thereto, as hole transport materials that can improve the voltage characteristics, life characteristics, and luminous efficiency of electroluminescence devices.

[0005] Patent No. 7054537

[0006] However, the inventors have found through their investigations that the compound described in Patent Document 1 does not have a sufficiently high electrical conductivity.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a novel compound that has high conductivity and can be used as a hole transport material, as well as a hole transport material and an electroluminescence device having high conductivity.

[0008] A compound according to one aspect of the present invention is represented by formula (1).

[0009]

[0010] In formula (1), R 1 and R 2each independently represents a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 20 ring carbon atoms, a substituted or unsubstituted heteroalkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted aralkyl group having from 7 to 30 carbon atoms, a substituted or unsubstituted aryl group having from 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having from 3 to 30 carbon atoms, or a combination thereof; and X represents an oxygen atom or a sulfur atom.

[0011] A hole transporting material according to another aspect of the present invention includes a compound represented by formula (1).

[0012] An electroluminescent device according to another aspect of the present invention includes a first electrode, a second electrode, and at least one organic layer provided between the first electrode and the second electrode, the organic layer containing a compound represented by formula (1).

[0013] The compound according to the present invention has hole transport properties and can be suitably used as a hole transport material. In addition, the compound and hole transport material according to the present invention have excellent thermal stability and high electrical conductivity, and when used in an organic layer of an electroluminescence device, the hole injection efficiency and hole transport efficiency can be improved, and the voltage, life span, and luminous efficiency of the electroluminescence device can be reduced.

[0014] 1 is a cross-sectional view showing an example of an electroluminescence element according to a third embodiment of the present invention; FIG. 2 is a cross-sectional view showing another example of an electroluminescence element according to the third embodiment of the present invention; FIG. 3 is a cross-sectional view showing yet another example of an electroluminescence element according to the third embodiment of the present invention;

[0015] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. The present invention can be modified in various ways within the scope of the object of the present invention, and embodiments obtained by appropriately combining the technical means described in different embodiments are also included in the technical scope of the present invention.

[0016] Hereinafter, the compound name may be followed by "system" to collectively refer to the compound and its derivatives. When the compound name is followed by "system" to describe the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, general formulas and chemical formulas will be collectively referred to as "formulas." Furthermore, "independently" in the description of a formula means that it may represent the same group or different groups. Furthermore, each component described below may be used alone or in combination of two or more types. Furthermore, "at least one of A and B" means "A and / or B." "A and / or B" means "A or B, or A and B."

[0017] [First embodiment: Compound] The first embodiment of the present invention relates to a compound represented by the following formula (1) (hereinafter, may be referred to as compound (1)).

[0018]

[0019] In formula (1), R 1 and R 2 each independently represents a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 20 ring carbon atoms, a substituted or unsubstituted heteroalkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted aralkyl group having from 7 to 30 carbon atoms, a substituted or unsubstituted aryl group having from 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having from 3 to 30 carbon atoms, or a combination thereof. In formula (1), X represents an oxygen atom or a sulfur atom.

[0020] In formula (1), "substituted or unsubstituted" may mean unsubstituted, and includes deuterium, a halogeno group, an unsubstituted alkyl group having from 1 to 20 carbon atoms, an unsubstituted cycloalkyl group having from 3 to 20 ring carbon atoms, an unsubstituted heteroalkyl group having from 1 to 20 carbon atoms, an unsubstituted aralkyl group having from 7 to 30 carbon atoms, an unsubstituted alkoxy group having from 1 to 20 carbon atoms, an unsubstituted aryloxy group having from 6 to 30 carbon atoms, an unsubstituted alkenyl group having from 2 to 20 carbon atoms, an unsubstituted alkyl group having from 2 to 20 carbon atoms, and the like.

[0039] This indicates that the aryl group may be substituted with at least one substituent selected from the group consisting of an unsubstituted aryl group having from 6 to 30 carbon atoms, an unsubstituted heteroaryl group having from 3 to 30 carbon atoms, an unsubstituted alkylsilyl group having from 3 to 20 carbon atoms, an unsubstituted arylsilyl group having from 6 to 20 carbon atoms, an amine group having from 0 to 20 carbon atoms, an acyl group, a carbonyl group, a carboxy group, an ester group, a cyano group, an isocyano group, a thio group, a sulfinyl group, a sulfonyl group, a phosphonoxy group, and combinations thereof.

[0021] Substitution includes both the replacement of hydrogen atoms with monovalent groups and the replacement of methylene groups with divalent groups, provided that the number of carbon atoms does not exceed the number specified in formula (1). Unless otherwise specified, each of the substituents may be optionally substituted.

[0022] In this specification, unless otherwise specified, alkyl groups include linear and branched alkyl groups. Unless otherwise specified, carbon atoms in the alkyl chain may be substituted with other heteroatoms. Similarly, unless otherwise specified, ring carbon atoms in a cycloalkyl group may be substituted with other heteroatoms. Unless otherwise specified, alkoxy groups include linear alkoxy groups, cyclic alkoxy groups, and branched alkoxy groups. Unless otherwise specified, alkenyl groups include linear olefinic groups and branched olefinic groups. Unless otherwise specified, alkynyl groups include linear alkynyl groups and branched alkynyl groups. Unless otherwise specified, aryl groups may be non-fused aryl groups or fused aryl groups. Unless otherwise specified, heteroaryl groups may be non-fused heteroaryl groups or fused heteroaryl groups.

[0023] Adjacent substituents may be bonded to form a ring. In the compound represented by formula (1), adjacent substituents may be bonded to form a ring, including cases where adjacent substituents are bonded to form a ring and cases where adjacent substituents are not bonded to form a ring. When adjacent substituents are bonded to form a ring, the ring formed may be any of a monocycle, a polycycle, an alicycle, a heteroalicycle, an aryl ring, and a heteroaryl ring. Adjacent substituents represent substituents that are closest in terms of steric structure, and may be substituents bonded to the same atom, substituents bonded to carbon atoms directly bonded to each other, or substituents bonded to distant carbon atoms. Preferably, adjacent substituents represent substituents bonded to the same carbon atom or substituents bonded to carbon atoms directly bonded to each other.

[0024] In addition, when adjacent substituents are bonded to form a ring, two substituents bonded to the same carbon atom may be bonded to each other by a chemical bond to form a ring, two substituents bonded to carbon atoms that are directly bonded to each other may be bonded to each other by a chemical bond to form a ring, and when one of two substituents bonded to carbon atoms that are directly bonded to each other is a hydrogen atom, the other substituent may be bonded to the position where the one substituent is bonded to form a ring.

[0025] In formula (1), R 1 and R 2 are each independently a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted biphenyl group.

[0026] In formula (1), R 1 and R 2 At least one of R may be optionally substituted with at least one electron-withdrawing group, 1 and R 2 At least one of the groups preferably has at least one electron-withdrawing group.

[0027] R 1 and R 2 The Hammett substituent constant of the electron-withdrawing group contained in is preferably 0.05 or more, more preferably 0.3 or more, and even more preferably 0.5 or more.

[0028] The Hammett substituent constant is an index of electron-withdrawing property, and the larger the Hammett substituent constant, the higher the electron-withdrawing property. When compound (1) has an electron-withdrawing group with a large Hammett substituent constant, the LUMO (lowest unoccupied molecular orbital) level of compound (1) can be deepened.

[0029] R 1 and R 2The electron-withdrawing group contained in is preferably a group selected from the group consisting of a halogeno group, a nitroso group, a nitro group, a carbonyl group, a carboxy group, an SF5 group, a cyano group, an isocyano group, an SCN group, an OCN group, a boryl group, a phosphonooxy group, a nitrogen-containing heteroaromatic ring group, and a combination thereof. These electron-withdrawing groups have a Hammett substituent constant of 0.05 or more, and have high electron-withdrawing properties. The nitrogen-containing heteroaromatic ring group contains at least one nitrogen atom. The number of ring carbon atoms of the nitrogen-containing heteroaromatic ring group does not have to exceed the number of carbon atoms specified in formula (1), but is preferably 3 to 30. Among these electron-withdrawing groups, R 1 and R 2 The electron-withdrawing group contained in is more preferably an electron-withdrawing group selected from the group consisting of a fluoro group, a CF group, an OCF group, an SF group, a cyano group, an isocyano group, an SCN group, an OCN group, a pyrimidine group, a triazine group, and combinations thereof. When compound (1) contains at least one such electron-withdrawing group having high electron-withdrawing properties, the LUMO (lowest unoccupied molecular orbital) level of compound (1) can be deepened.

[0030] Therefore, in formula (1), R 1 and R 2 at least one of the groups is preferably an alkyl group having 1 to 20 carbon atoms and substituted with at least one of these electron-withdrawing groups, a cycloalkyl group having 3 to 20 ring carbon atoms and substituted with at least one of these electron-withdrawing groups, a heteroalkyl group having 1 to 20 carbon atoms and substituted with at least one of these electron-withdrawing groups, an aralkyl group having 7 to 30 carbon atoms and substituted with at least one of these electron-withdrawing groups, an aryl group having 6 to 30 carbon atoms and substituted with at least one of these electron-withdrawing groups, a heteroaryl group having 3 to 30 carbon atoms and substituted with at least one of these electron-withdrawing groups, or a combination thereof.

[0031] In addition, in formula (1), R 1 and R 2are each independently any one selected from the group consisting of a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms; an unsubstituted phenyl group; an unsubstituted biphenyl group; and a phenyl group or biphenyl group substituted with at least one selected from the group consisting of a halogeno group, a nitroso group, a nitro group, a carbonyl group, a carboxy group, an SF5 group, a cyano group, an isocyano group, an SCN group, an OCN group, a boryl group, and a phosphonooxy group.

[0032] In addition, in formula (1), R 1 and R 2 are each independently any one selected from the group consisting of a phenyl group, a methoxyphenyl group, a p-methylphenyl group, a 2,6-diisopropylphenyl group, a biphenyl group, a polyfluorophenyl group, a nitrophenyl group, a trifluoromethylphenyl group, a trifluoromethoxyphenyl group, a bis(trifluoromethyl)phenyl group, a bis(trifluoromethoxy)phenyl group, a 4-cyanotetrafluorophenyl group, and a phenyl group or a biphenyl group substituted with at least one selected from the group consisting of a fluoro group, a CF group, a cyano group, an isocyano group, and combinations thereof.

[0033] In addition, in formula (1), R 1 and R 2 is more preferably each independently a group represented by any one of formulas (A1) to (A20), wherein * represents a bond.

[0034]

[0035] Suitable examples of the compound (1) include compounds represented by the formula (1) in which X, R 1 , and R 2 Examples of the compounds include compounds (1-1) to (1-34) having the combinations shown in Table 1. In Table 1, O represents an oxygen atom, and S represents a sulfur atom. Also, A1 to A20 represent groups represented by formulas (A1) to (A20).

[0036]

[0037] Among the compounds (1), the compounds (1-1) to (1-34) shown in Table 1 have particularly excellent thermal stability and can achieve high electrical conductivity. Therefore, all of these compounds (1-1) to (1-34) can be particularly suitably used as hole transport materials. 1 and R 2 When at least one of the groups is a hydrogen atom, the thermal stability is low and the material is not suitable for use as a hole transporting material.

[0038] Among the compounds (1-1) to (1-34), R 1 and R 2 More preferably, at least one of R has a fluoro group and / or a cyano group. 1 and R 2 Among the compounds (1-1) to (1-34), compounds in which at least one of R has two or more fluoro groups and / or cyano groups are more preferred, compounds in which R has three or more fluoro groups and / or cyano groups are even more preferred, and compounds in which R has five fluoro groups and / or cyano groups are even more preferred. 1 and R 2 A compound in which at least one of the above has two or more cyano groups is particularly preferred.

[0039] [Method for producing compound (1)] Next, a method for producing compound (1) will be described. Compound (1) is produced, for example, according to the following reaction scheme or a method equivalent thereto. In the following, the compounds represented by formulas (a), (b), (c), (d), and (L) may be referred to as compounds (a), (b), (c), (d), and (L), respectively. In compounds (a), (b), (c), (d), and (L), R 1 , R 2 , and X are R in formula (1), 1 , R 2 , and X.

[0040]

[0041] The method for producing compound (1) includes, for example, reactions (r-1) to (r-4). In reaction (r-1), 1 molar equivalent of compound (a) is reacted with 2 molar equivalents of compound (L), which is a secondary amine, to obtain 1 molar equivalent of compound (b), which is an intermediate.

[0042] Reaction (r-2) is an iodination reaction in which 1 molar equivalent of compound (b) obtained in reaction (r-1) is reacted with 2 molar equivalents of iodine to obtain 1 molar equivalent of compound (c) as an intermediate.

[0043] In reaction (r-3), 1 molar equivalent of compound (c) obtained in reaction (r-2) is reacted with 2 molar equivalents of malononitrile to obtain 1 molar equivalent of compound (d) as an intermediate.

[0044] In the reaction (r-4), the compound (d) obtained in the reaction (r-3) is isomerized to obtain the compound (1).

[0045] The reactions (r-1) to (r-4) are preferably carried out in an inert gas atmosphere, such as nitrogen gas or argon gas.

[0046] Reactions (r-1) to (r-4) can be carried out in a solvent, such as cyclopentyl methyl ether, anhydrous THF (tetrahydrofuran), or anhydrous DMF (dimethylformamide).

[0047] The reactions (r-1) and (r-3) may be carried out in the presence of a palladium catalyst, such as palladium acetate, tetrakis(triphenylphosphine), or palladium.

[0048] The palladium catalyst may be used in combination with an organic phosphorus ligand. Examples of organic phosphorus ligands include Xphos (2-dicyclohexylphosphino-2',4',6'-triisopropyl-1,1'-biphenyl). Furthermore, a palladium catalyst coordinated with an organic phosphorus ligand may be used as the palladium catalyst.

[0049] Reactions (r-1) to (r-4) may be carried out in the presence of a base, such as potassium carbonate, n-butyllithium, sodium hydride, or bis(trifluoroacetoxy)iodobenzene.

[0050] The reaction temperature of the reaction (r-1) is preferably the reflux temperature, and the reaction time of the reaction (r-1) is preferably 1 hour or more and 20 hours or less.

[0051] Reaction (r-2) can be carried out at room temperature. The reaction temperature of reaction (r-2) is preferably 15° C. or higher and 40° C. or lower. The reaction time of reaction (r-1) is preferably 1 hour or higher and 15 hours or lower.

[0052] The reaction temperature of the reaction (r-3) is preferably 70° C. or more and 110° C. or less. The reaction time of the reaction (r-1) is preferably 1 hour or more and 36 hours or less.

[0053] When a base is used as the isomerization catalyst, for example, reaction (r-4) can be carried out at room temperature. In this case, the reaction temperature of reaction (r-4) is preferably 15°C or higher and 40°C or lower. Isomerization may also be carried out by heating. The reaction time of reaction (r-4) varies depending on the reaction conditions, but is preferably 1 hour or higher and 96 hours or lower.

[0054] The reaction products obtained in each reaction can be purified to isolate the intermediate compounds (b) to (d) and the target compound (1). Examples of purification methods include purification by column chromatography, adsorption purification using silica gel or activated clay, or recrystallization or crystallization using a solvent. Nuclear magnetic resonance analysis (NMR) or the like can be used to identify the resulting compounds.

[0055] [Second embodiment: hole transport material] The second embodiment of the present invention relates to a hole transport material. Compound (1) according to the first embodiment of the present invention can be used as a hole transport material. The hole transport material according to this embodiment contains compound (1).

[0056] As described in the first embodiment, compound (1) has high conductivity and can be suitably used as a hole transport material. The hole transport material may contain only compound (1), or may further contain a hole transport material other than compound (1).

[0057] The hole transport material according to this embodiment may further contain additives as needed. As the additives, conventionally known additives such as an interface treatment agent can be used.

[0058] A hole transport material containing compound (1) has excellent thermal stability and high conductivity. Therefore, when compound (1) or a hole transport material containing compound (1) is used in an organic layer of an electroluminescence device (hereinafter sometimes referred to as an EL device), the hole injection efficiency, hole transport efficiency, and light-emitting efficiency of the EL device can be improved. Compound (1) or a hole transport material containing compound (1) may be used alone, as a host, or as a dopant. For example, by using compound (1) or a hole transport material containing compound (1) as a dopant, the HOMO level and LUMO level of the doped layer can be changed, thereby improving the hole injection efficiency or hole transport efficiency of the doped layer.

[0059] [Third Embodiment: EL Element] The third embodiment of the present invention relates to an EL element. The EL element according to the third embodiment of the present invention includes a first electrode, a second electrode, and at least one organic layer containing the compound (1) according to the first embodiment, disposed between the first and second electrodes. The compound (1) has hole transport properties and is suitable for use as a material for, for example, a hole injection layer, a hole transport layer, an electron blocking layer, or an emitting layer. The organic layer containing the compound (1) may be a hole injection layer or a hole transport layer. The organic layer containing the compound (1) may be an electron blocking layer or an emitting layer. The organic layer containing the compound (1) is preferably one or more layers selected from a hole injection layer, a hole transport layer, an electron blocking layer, and an emitting layer, and more preferably a layer adjacent to an anode (e.g., a hole injection layer). Therefore, the at least one organic layer containing the compound (1) preferably includes any one of a hole injection layer, a hole transport layer, and an electron blocking layer, and more preferably includes a hole injection layer.

[0060] The structure of the EL element according to this embodiment will be described below with reference to Fig. 1. Fig. 1 is a cross-sectional view showing an example of the EL element according to this embodiment. In the following, the EL element according to this embodiment will be described as an organic EL element (also called an organic light-emitting diode).

[0061] 1, the EL element 10 according to this embodiment includes a first electrode 2, a second electrode 4, and an EL layer 3 provided between the first electrode 2 and the second electrode 4. In this embodiment, the functional layers provided between the first electrode 2 and the second electrode 4 are collectively referred to as an EL layer (electroluminescence layer).

[0062] 1 shows an example in which the first electrode 2 is an anode and the second electrode 4 is a cathode. The EL layer 3 shown in Fig. 1 has a configuration in which a hole injection layer 11, a hole transport layer 12, an electron blocking layer 13, an emitting layer 14, a hole blocking layer 15, an electron transport layer 16, and an electron injection layer 17 are provided in this order from the first electrode 2 side.

[0063] 1, the EL element 10 according to this embodiment may include a substrate 1. The substrate 1 is used as a support for supporting a laminate including the first electrode 2, the EL layer 3, and the second electrode 4.

[0064] (Substrate) The substrate 1 may be a flexible substrate having flexibility, or may be a rigid substrate having rigidity. The substrate 1 may also be transparent, translucent, or opaque. Examples of materials for the substrate 1 include glass, quartz, ceramics, plastic, and stainless steel. The substrate 1 may also be a circuit board or an array substrate provided with a plurality of driving elements such as thin film transistors (TFTs). When the EL element 10 is part of a device such as a display device or a lighting device, the substrate 1 is a support of the device.

[0065] (First Electrode and Second Electrode) As described above, one of the first electrode 2 and the second electrode 4 is an anode, and the other is a cathode. The first electrode 2 and the second electrode 4 are made of a conductive material. At least one of the first electrode 2 and the second electrode 4 may be substantially transparent so that light from the light-emitting layer 14 can pass through and be extracted to the outside of the EL element 10. The first electrode 2 may be formed in a sheet shape over the entire surface of the substrate 1, or may be formed in a pattern on the substrate 1.

[0066] The anode is preferably made of a material with a relatively large work function, such as gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), titanium (Ti), or alloys thereof; metal oxides such as zinc oxide, tin oxide, or indium oxide; and metal nitrides such as titanium nitride.

[0067] On the other hand, the cathode is preferably made of a material with a relatively small work function, such as an alkali metal such as lithium (Li) or cesium (Cs), an alkaline earth metal such as magnesium (Mg), calcium (Ca), or strontium (Sr), or an alloy thereof (e.g., MgAg), or a rare earth metal such as europium (Eu) or ytterbium (Yb), or an alloy thereof.

[0068] The first electrode 2 and the second electrode 4 may have a single-layer structure, or a laminated structure in which multiple layers are laminated. For example, in order to reduce the wiring resistance of the first electrode 2 or the second electrode 4, a low-resistivity metal such as Al (aluminum), Ag, Cu, or Au may be laminated, such as ITO / Ag / ITO (a three-layer structure in which ITO (indium tin oxide), Ag (silver), and ITO are laminated in this order).

[0069] The EL layer 3 includes at least one organic layer containing the compound (1). The compound (1) may be contained in at least one of the hole injection layer 11, the hole transport layer 12, the electron blocking layer 13, and the light-emitting layer 14. When the EL layer 3 includes an organic layer containing the compound (1), an EL element 1 can be obtained that has excellent thermal stability, high conductivity, and excellent voltage characteristics, life characteristics, luminous efficiency, etc.

[0070] (Light-emitting layer 14) The light-emitting layer 14 contains a light-emitting material. Holes injected into the light-emitting layer 14 from the anode and electrons injected into the light-emitting layer 14 from the cathode are recombined in the light-emitting layer 14 to form excitons. The formed excitons emit light when they deactivate from the excited state to the ground state. This results in the emission of light of a color corresponding to the light-emitting material. As the light-emitting material, low-molecular-weight fluorescent dyes, metal complexes, etc., or known organic light-emitting materials that emit fluorescence or phosphorescence can be used.

[0071] The light-emitting layer 14 may contain only the light-emitting material, or may contain the light-emitting material together with a hole-transporting material and / or an electron-transporting material. When the light-emitting layer 14 contains a hole-transporting material, the hole-transporting material is used as a hole-transporting host responsible for charge transport of holes within the light-emitting layer 14. The light-emitting material is used as a dopant. Compound (1) can be used as the hole-transporting host.

[0072] When the light-emitting layer 14 contains the compound (1), the molar ratio of the compound (1) to the light-emitting material in the light-emitting layer 14 is preferably 10,000:1 or more and 1:10,000 or less, and more preferably 10:1 or more and 1:100 or less.

[0073] (Hole Injection Layer, Hole Transport Layer, Electron Blocking Layer) The hole transport layer 12 is disposed between the anode and the light-emitting layer 14, and promotes the transport of holes from the anode to the light-emitting layer 14. The hole injection layer 11 is disposed between the anode and the hole transport layer 12, and promotes the injection of holes from the anode to the hole transport layer 12. The electron blocking layer 13 is disposed between the hole transport layer 12 and the light-emitting layer 14, and transports holes from the hole transport layer 12 to the light-emitting layer 14, while trapping electrons injected from the cathode side in the light-emitting layer 14.

[0074] The hole injection layer 11 and the hole transport layer 12 are made of a hole transport material. The electron blocking layer 13 is made of an electron blocking material that blocks the transport of electrons. The electron blocking material may be an organic insulating material or a hole transport material.

[0075] Therefore, each of these functional layers (hole injection layer 11, hole transport layer 12, and electron blocking layer 13) may contain only a known hole transport material (hereinafter, sometimes referred to as a first hole transport material) as the hole transport material, or may contain only compound (1). Furthermore, each of these functional layers may contain, as the hole transport material, compound (1) and the first hole transport material.

[0076] When these functional layers are organic layers containing compound (1) and a first hole transport material, the molar ratio of compound (1) to the first hole transport material in these functional layers is preferably 10,000:1 or more and 1:10,000 or less, and more preferably 10:1 or more and 1:100 or less.

[0077] Similar hole transport materials can be used for the hole transport hosts of the hole injection layer 11, the hole transport layer 12, and the electron blocking layer 13, and the light emitting layer 14. When the hole injection layer 11, the hole transport layer 12, the electron blocking layer 13, and the light emitting layer 14 contain a first hole transport material, examples of the first hole transport material include a compound having a triarylamine unit, a spirobifluorene compound, a pentacene compound, an oligothiophene compound, an oligophenyl compound, an oligophenylene vinyl compound, an oligofluorene compound, a porphyrin complex, and a metal phthalocyanine complex.

[0078] Among these first hole transport materials, spirobifluorene compounds are preferred, and 2,2',7,7'-tetrakis[N,N-di-p-methoxyphenylamino]-9,9'-spirobifluorene represented by the following formula (HT1) (hereinafter, sometimes referred to as compound (HT1)) is more preferred.

[0079]

[0080] In order to efficiently transport holes to the light-emitting layer 14 and improve light-emitting efficiency, it is preferable that the HOMO (highest occupied molecular orbital) level of the hole-transport material in the hole injection layer 11 be deeper (larger in absolute value) than the HOMO level of the hole-transport material in the hole transport layer 12. In this case, holes can easily enter the hole transport layer 12, and holes can be efficiently injected from the hole injection layer 11 to the hole transport layer 12, allowing the light-emitting layer 14 to emit light efficiently. It is also preferable that the LUMO level of the hole-transport material in the hole injection layer 11 be deeper (larger in absolute value) than the LUMO level of the hole-transport material in the hole transport layer 12. In this case, electrons are less likely to leak from the hole transport layer 12 to the hole injection layer 11, allowing the light-emitting layer 14 to emit light efficiently. Therefore, it is preferable that the hole-transport material in the hole injection layer 11 and the hole-transport material in the hole injection layer 11 be selected so as to satisfy the above relationship.

[0081] Furthermore, in order to efficiently confine electrons in the light-emitting layer 14, it is preferable that the LUMO level of the hole-transporting material in the electron-blocking layer 13, which serves as an electron-blocking material, is deeper than the LUMO level of the hole-transporting material in the light-emitting layer 14. In this case, electrons are less likely to leak from the light-emitting layer 14 to the hole-transporting layer 12, and electrons can be efficiently confined in the light-emitting layer 14, allowing the light-emitting layer 14 to emit light efficiently. Both the HOMO level and the LUMO level can be determined by a commonly used method.

[0082] (Hole Blocking Layer, Electron Transport Layer, Electron Injection Layer) The electron transport layer 16 is disposed between the cathode and the light-emitting layer 14, and promotes the transport of electrons from the cathode to the light-emitting layer 14. The electron injection layer 17 is disposed between the anode and the electron transport layer 16, and promotes the injection of electrons from the anode to the electron transport layer 16. The hole blocking layer 15 is disposed between the electron transport layer 16 and the light-emitting layer 14, and transports electrons from the electron transport layer 16 to the light-emitting layer 14, while confining holes injected from the anode side in the light-emitting layer 14.

[0083] The electron injection layer 17 and the electron transport layer 16 are made of an electron transporting material. The hole blocking layer 15 is made of a hole blocking material that blocks the transport of holes. The hole blocking material may be an organic insulating material or an electron transporting material.

[0084] The electron injection layer 17, the electron transport layer 16, and the hole blocking layer 15 may be made of a known electron transport material.

[0085] Examples of materials that can be used for the electron injection layer 17 include alkali metals, alkaline earth metals, alkali metal compounds, alkaline earth metal compounds, alkali metal complexes, alkaline earth metal complexes, mixtures of at least one of these with organic compounds, and any combinations of these.

[0086] Examples of materials that can be used for the electron transport layer 16 include metal complexes such as aluminum complexes, beryllium complexes, and zinc complexes; aromatic heterocyclic compounds such as imidazole derivatives, benzimidazole derivatives, azine derivatives, carbazole derivatives, and phenanthroline derivatives; and other polymer compounds.

[0087] The hole blocking layer 15 may be made of, for example, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP).

[0088] The thickness of each layer in the EL element 10 may be selected so as to obtain appropriate values ​​for the driving voltage and luminous efficiency, but the thickness must be such that pinholes are not generated. Note that the thicker the layer, the higher the driving voltage of the EL element 10. The order, number, and thickness of the stacked layers may be adjusted taking into consideration the luminous efficiency and element life, and can be set in the same manner as in the past.

[0089] 1, the EL element 10 may have a cover layer 5 on the surface opposite to the substrate 1. In FIG. 1, the EL element 10 is illustrated as an example in which a first electrode 22, an EL layer, a second electrode 24, and a cover layer 5 are laminated in this order on the substrate 1.

[0090] The cover layer 5 is a layer that prevents the penetration of foreign substances such as moisture and oxygen into the EL layer. The cover layer 5 may be an inorganic insulating layer and / or an organic insulating layer, or a laminate thereof, or may be a hard substrate such as glass.

[0091] An example of an EL element according to this embodiment has been described above. However, the EL element according to this embodiment is not limited to the EL element 10 shown in FIG. 1 . The EL layer only needs to include at least a light-emitting layer, and some functional layers in the EL layer may be omitted. Furthermore, one layer may have multiple functions. For example, the hole transport layer may also function as a hole injection / transport layer that also functions as a hole injection layer. Furthermore, the EL layer may further include other functional layers.

[0092] 1 illustrates an example in which the first electrode 2 is an anode, the second electrode 4 is a cathode, and the anode, EL layer, and cathode are provided on the substrate 1 in this order from the substrate 1 side. However, this embodiment is not limited to this, and the cathode, EL layer, and anode may be provided on the substrate 1 in this order from the substrate 1 side. That is, in FIG. 1, the first electrode 2 may be a cathode, and the second electrode 4 may be an anode. However, when the first electrode 2 is a cathode and the second electrode 4 is an anode, the arrangement order of the hole injection layer 11, the hole transport layer 12, the electron blocking layer 13, the light-emitting layer 14, the hole blocking layer 15, the electron transport layer 16, and the electron injection layer 17 is reversed from the example illustrated in FIG. 1. When the first electrode 2 is a cathode and the second electrode 4 is an anode, the electron injection layer 17, the electron transport layer 16, the hole blocking layer 15, the light-emitting layer 14, the electron blocking layer 13, the hole transport layer 12, and the hole injection layer 11 are provided in this order from the substrate 1 side, which is the cathode side.

[0093] The EL device according to this embodiment may have a multi-stack structure in which a plurality of light-emitting units, each including a light-emitting layer, are stacked with a charge generation layer interposed therebetween, and the charge generation layer includes a p-type charge generation layer and an n-type charge generation layer. For example, the EL device according to this embodiment may have a first light-emitting unit including at least a first light-emitting layer, a second light-emitting unit including at least a second light-emitting layer, and a charge generation layer provided between the first light-emitting unit and the second light-emitting unit, and the charge generation layer includes an n-type charge generation layer and a p-type charge generation layer. When the EL device according to this embodiment has such a multi-stack structure, the p-type charge generation layer may be an organic layer containing the compound (1) according to the first embodiment.

[0094] The structure of an EL element having a multi-stack structure according to this embodiment will be described below with reference to Fig. 2 and Fig. 3. Fig. 2 and Fig. 3 are cross-sectional views showing other examples of an EL element according to this embodiment. In Fig. 2 and Fig. 3, the p-type charge generation layer is an organic layer containing the compound (1) according to the first embodiment.

[0095] The EL element 20 shown in FIG. 2 includes a first electrode 22, a second electrode 24, and an EL layer provided between the first electrode 22 and the second electrode 24.

[0096] 2 shows an example in which the first electrode 22 is an anode and the second electrode 24 is a cathode. The EL layer shown in Fig. 2 includes a first light-emitting unit 31, a second light-emitting unit 33, and a charge generation layer 32 provided between the first light-emitting unit 31 and the second light-emitting unit 33. In Fig. 2, the first light-emitting unit 31, the charge generation layer 32, and the second light-emitting unit 33 are collectively referred to as the EL layer.

[0097] The first light-emitting unit 31 includes a first hole injection layer 41, a first hole transport layer 42, a first electron blocking layer 43, a first light-emitting layer 44, a first hole blocking layer 45, and a first electron transport layer 46. The first hole injection layer 41, the first hole transport layer 42, the first electron blocking layer 43, the first light-emitting layer 44, the first hole blocking layer 45, and the first electron transport layer 46 are provided in this order from the first electrode 22 side.

[0098] The second light-emitting unit 33 includes a second hole injection layer 61, a second hole transport layer 62, a second electron blocking layer 63, a second light-emitting layer 64, a second hole blocking layer 65, a second electron transport layer 66, and an electron injection layer 67. The second hole injection layer 61, the second hole transport layer 62, the second electron blocking layer 63, the second light-emitting layer 64, the second hole blocking layer 65, the second electron transport layer 66, and the electron injection layer 67 are provided in this order from the charge generation layer 32 side.

[0099] The charge generation layer 32 includes an n-type charge generation layer 51 and a p-type charge generation layer 52. The n-type charge generation layer 51 and the p-type charge generation layer 52 are provided in this order from the first light-emitting unit 31 side.

[0100] Therefore, the EL layer shown in FIG. 2 has a configuration in which a first hole injection layer 41, a first hole transport layer 42, a first electron blocking layer 43, a first light-emitting layer 44, a first hole blocking layer 45, a first electron transport layer 46, an n-type charge generation layer 51, a p-type charge generation layer 52, a second hole injection layer 61, a second hole transport layer 62, a second electron blocking layer 63, a second light-emitting layer 64, a second hole blocking layer 65, a second electron transport layer 66, and an electron injection layer 67 are provided in this order from the first electrode 22 side.

[0101] 2, the EL element 20 may also include a substrate 11. The substrate 11 is used as a support for supporting a laminate including the first electrode 22, the EL layer, and the second electrode 24. The EL element 20 may also include a cover layer 25 on the surface opposite to the substrate 11, as shown in FIG.

[0102] The substrate 11 can be the same as the substrate 1. The cover layer 25 can be designed in the same way as the cover layer 5. The first hole blocking layer 45 and the second hole blocking layer 65 can be designed in the same way as the hole blocking layer 15. Therefore, the materials for the first hole blocking layer 45 and the second hole blocking layer 65 can be the same as the materials for the hole blocking layer 15. The first electron transport layer 46 and the second electron transport layer 66 can be designed in the same way as the electron transport layer 16. Therefore, the materials for the first electron transport layer 46 and the second electron transport layer 66 can be the same as the materials for the electron transport layer 16. The first electrode 22 can be designed in the same way as the first electrode 2. Therefore, the materials for the first electrode 22 can be the same as the materials for the first electrode 2. The second electrode 24 can be designed in the same way as the second electrode 4. Therefore, the materials for the second electrode 24 can be the same as the materials for the second electrode 4.

[0103] The p-type charge generation layer 52 supplies holes to the second light-emitting unit 33. When the p-type charge generation layer 52 contains compound (1) as described above, the p-type charge generation layer 52 may contain only compound (1), or may contain compound (1) and a first hole transport material. When the p-type charge generation layer 52 contains the first hole transport material, the first hole transport material described above can be used as the first hole transport material.

[0104] When the p-type charge generation layer 52 is an organic layer containing the compound (1) and the first hole transport material, the molar ratio of the compound (1) to the first hole transport material in these functional layers is preferably 10,000:1 or more and 1:10,000 or less, and more preferably 10:1 or more and 1:100 or less.

[0105] The n-type charge generation layer 51 supplies electrons to the first light-emitting unit 3. The n-type charge generation layer 51 is made of an electron transporting material. As the electron transporting material, the various electron transporting materials exemplified above can be used.

[0106] The EL layer only needs to include at least one organic layer containing compound (1). Therefore, when the p-type charge generation layer 52 is an organic layer containing compound (1) and a first hole transport material, the first hole injection layer 41, the first hole transport layer 42, the first electron blocking layer 43, the first light-emitting layer 44, the second hole injection layer 61, the second hole transport layer 62, the second electron blocking layer 63, and the second light-emitting layer 64 may or may not contain compound (1).

[0107] Therefore, the first hole injection layer 41, the first hole transport layer 42, the first electron blocking layer 43, the second hole injection layer 61, the second hole transport layer 62, and the second electron blocking layer 63 may each contain only the first hole transport material or only compound (1) as the hole transport material. Furthermore, each of these functional layers may contain compound (1) and the first hole transport material as the hole transport material.

[0108] The first hole injection layer 41 and the second hole injection layer 61 can be designed in the same manner as the hole injection layer 11. Therefore, the materials for the first hole injection layer 41 and the second hole injection layer 61 can be the same as the materials for the hole injection layer 11. The first hole transport layer 42 and the second hole transport layer 62 can be designed in the same manner as the hole transport layer 12. Therefore, the materials for the first hole transport layer 42 and the second hole transport layer 62 can be the same as the materials for the hole transport layer 12. The first electron blocking layer 43 and the second electron blocking layer 63 can be designed in the same manner as the electron blocking layer 13. Therefore, the materials for the first electron blocking layer 43 and the second electron blocking layer 63 can be the same as the materials for the electron blocking layer 13.

[0109] EL element 70 shown in FIG. 3 is the same as EL element 20 shown in FIG. 2 except that EL layer 32 includes buffer layer 53 provided between n-type charge generating layer 51 and p-type charge generating layer 52.

[0110] By providing the thin buffer layer 53 between the n-type charge generating layer 51 and the p-type charge generating layer 52 in this manner, for example, it is possible to improve the adhesion at the interface and prevent mixing.

[0111] When a thin buffer layer 53 is provided between the n-type charge generating layer 51 and the p-type charge generating layer 52 in this manner, the buffer layer 53 may contain compound (1). When the buffer layer 53 contains compound (1), it may contain only compound (1), or it may contain compound (1) and a first hole transport material. When the buffer layer 53 contains the first hole transport material, the first hole transport material described above can be used as the first hole transport material. When the buffer layer 53 contains compound (1) in this manner, the conductivity of the buffer layer 53 can be improved, and an EL element with higher conductivity can be obtained.

[0112] 2 and 3 illustrate an example in which the first light-emitting unit 31 does not have an electron injection layer. However, as described above, the EL element according to this embodiment may further include other functional layers, and one layer may have multiple functions. Therefore, the EL element 20 and the EL element 70 may have a configuration in which the first light-emitting unit 31 is provided with a first electron injection layer as the electron injection layer, and the second light-emitting unit 33 is provided with an electron injection layer 67 as the second electron injection layer. Furthermore, some functional layers in the EL layer may be omitted.

[0113] In addition, in this embodiment, the EL element according to this embodiment is an organic EL element. However, the EL element according to this embodiment is not limited to an organic EL element, and may be, for example, a QLED (quantum dot light-emitting diode) using nano-sized quantum dots (semiconductor nanoparticles) as a light-emitting material. In addition, when the EL element is a QLED, the HOMO level and the LUMO level are replaced by the conduction band level and the valence band level, respectively.

[0114] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples.

[0115] <Synthesis of Compounds> As Examples 1 to 10, the compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32) described in the first embodiment were synthesized by the following methods.

[0116] <Synthesis of Compound (1-6)> Compound (1-6) was synthesized according to the following reaction scheme. Hereinafter, the compounds represented by formulas (a-1), (b-1), (c-1), (d-1), and (L-1) may be referred to as compounds (a-1), (b-1), (c-1), (d-1), and (L-1), respectively. As shown in the following reaction scheme, compound (a-1) is compound (a) in which X is an oxygen atom. Compound (L-1) is a compound represented by formula (a) in which R 1 and R 2 Compounds (b-1), (c-1), and (d-1) are compounds (L) in which X is an oxygen atom and R 1 and R 2 are compounds (b), (c), and (d) each of which is a group represented by formula (A6). The yield of each compound was calculated in terms of molar ratio.

[0117]

[0118] In reaction (r-1), compound (a-1) was reacted with compound (L-1) to obtain compound (b-1). In the synthesis of compound (b-1), first, 100 mL of cyclopentyl methyl ether was placed in a reaction flask under a nitrogen atmosphere, stirred, and nitrogen gas was bubbled through for 15 minutes. Next, 1.89 mmol (0.420 g) of palladium acetate and 3.93 mmol (1.870 g) of Xphos were added to the reaction flask and stirred for 10 minutes. Next, 15.7 mmol (5.000 g) of compound (a-1), 65.3 mmol (11.000 g) of the secondary amine compound (L-1), and 94.3 mmol (13.000 g) of potassium carbonate were added and reacted for 14 hours under heating and reflux. Thereafter, the contents of the reaction vessel were cooled to room temperature, the solid was filtered off, and the filtrate was concentrated under reduced pressure. The solid formed by this vacuum concentration was collected by filtration, washed with water, and then washed with methanol. The washed solid was recrystallized with hot chloroform, and the collected solid was washed with chloroform to obtain compound (b-1). The yield of compound (b-1) was 3.890 g, and the yield of compound (b-1) from compound (a-1) was 50%.

[0119] In reaction (r-2), compound (b-1) was reacted with iodine to obtain compound (c-1). In the synthesis of compound (c-1), first, 11.47 mmol (5.670 g) of compound (b-1) was placed in a reaction flask and purged with nitrogen. Next, 200 mL of anhydrous THF was added to the reaction flask. After the contents of the reaction flask were cooled to -94°C, 26.4 mmol (16.4 ml) of a 1.6 M hexane solution of n-butyllithium was slowly added dropwise to the contents of the reaction flask. After the dropwise addition of the 1.6 M hexane solution of n-butyllithium, the contents of the reaction flask were stirred for 1 hour and then stirred at -78°C for an additional 5 hours. Next, 34.4 mmol (8.730 g) of iodine dissolved in 10 mL of THF (iodine / THF solution) was added to the contents of the reaction flask, and the contents of the reaction flask were stirred for 5 hours while the temperature was returned to room temperature. Next, 50 mL of saturated aqueous ammonium chloride solution was added to the contents of the reaction flask and stirred. The product was extracted with chloroform, and the organic layer containing chloroform was distilled off under reduced pressure. Thereafter, the residue was purified by silica gel column chromatography using chloroform and hexane as an additional solvent to obtain compound (c-1). The yield of compound (c-1) was 3.420 g, and the yield of compound (c-1) from compound (b-1) was 40%.

[0120] In reaction (r-3), compound (c-1) was reacted with malononitrile to obtain compound (d-1). In the synthesis of compound (d-1), first, 9.3 mmol (0.473 g) of 60% sodium hydride was placed in a reaction flask and purged with nitrogen, after which 20 mL of anhydrous DMF was added to the reaction flask. The reaction flask was then cooled to 0°C in an ice bath, and 9.3 mmol (0.615 g) of malononitrile dissolved in 5 mL of DMF was added dropwise to the contents of the reaction flask. The contents of the reaction flask were stirred for 10 minutes, after which the ice bath was removed and the contents of the reaction flask were stirred for 20 minutes while allowing the temperature to return to room temperature. Subsequently, 1.56 mmol (1.160 g) of compound (c-1) was added to the contents of the reaction flask, followed by 0.155 mmol (0.180 g) of tetrakis(triphenylphosphine)palladium(0). The contents of the reaction flask were then heated to 90°C and stirred for 18 hours. The contents of the reaction flask were then poured into 100 mL of ice water, adjusted to pH 1 with concentrated hydrochloric acid, and the resulting solid was collected by filtration and washed with chloroform to obtain compound (d-1). The yield of compound (d-1) was 0.870 g, and the yield of compound (d-1) from compound (c-1) was 90%.

[0121] In reaction (r-4), compound (d-1) was isomerized to obtain compound (1-6). In the synthesis of compound (1-6), first, 1.4 mmol (0.871 g) of compound (d-1) was placed in a reaction flask and the atmosphere was replaced with nitrogen. Next, the reaction flask was cooled to 0°C in an ice bath, and 200 mL of chloroform was added to compound (d-1) in the reaction flask. Next, 4.2 mmol (1.820 g) of bis(trifluoroacetoxy)iodobenzene was added to the contents of the reaction flask and stirred for 30 minutes. Next, the ice bath was removed, and the contents of the reaction flask were stirred at room temperature for 72 hours. Next, the contents of the reaction flask were concentrated under reduced pressure, and then hexane was added to the contents of the reaction flask. The precipitated solid was collected by filtration to obtain compound (1-6). The yield of compound (1-6) was 0.690 g, and the yield of compound (1-6) from compound (d-1) was 80%.

[0122] <Synthesis of Compounds (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32)> Hereinafter, compound (a) in which X is a sulfur atom may be referred to as compound (a-2). 1 and R 2 are each a group represented by formula (A15), is referred to as compound (L-2), X is an oxygen atom, and R 1 and R 2 The compounds (b), (c), and (d) each having a group represented by formula (A15) may be referred to as compounds (b-2), (c-2), and (d-2), respectively.

[0123] Also, R 1 and R 2 are each a group represented by formula (A16), is referred to as compound (L-3), X is an oxygen atom, and R 1 and R 2 are groups represented by formula (A15), may be referred to as compounds (b-3), (c-3) and (d-3), respectively.

[0124] Also, R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A6), is referred to as compound (L-4), X is an oxygen atom, and R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A6), may be referred to as compounds (b-4), (c-4) and (d-4), respectively.

[0125] Also, R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A15), is referred to as compound (L-5), X is an oxygen atom, and R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A15), may be referred to as compounds (b-5), (c-5), and (d-5), respectively.

[0126] Also, R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A16), is referred to as compound (L-6), X is an oxygen atom, and R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A16), may be referred to as compounds (b-6), (c-6) and (d-6), respectively.

[0127] Also, R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A18), is referred to as compound (L-7), X is an oxygen atom, and R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A18), may be referred to as compounds (b-7), (c-7) and (d-7), respectively.

[0128] Also, R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A19), is referred to as compound (L-8), X is an oxygen atom, and R 1 is a group represented by formula (A1), and R 2 is a group represented by formula (A19), may be referred to as compounds (b-8), (c-8) and (d-8), respectively.

[0129] Also, R 1 is a group represented by formula (A15), and R 2 is a group represented by formula (A16), is referred to as compound (L-9), X is an oxygen atom, and R 1 is a group represented by formula (A15), and R 2 is a group represented by formula (A16), may be referred to as compounds (b-9), (c-9) and (d-9), respectively.

[0130] Also, R 1 and R 2are each a group represented by formula (A11), is referred to as compound (L-10), X is a sulfur atom, and R 1 and R 2 The compounds (b), (c), and (d) each having a group represented by formula (A11) may be referred to as compounds (b-10), (c-10), and (d-10), respectively.

[0131] Compounds (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), and (1-26) were each synthesized by the same method as in the synthesis of compound (1-6), except that compound (L-1) was changed to any of compounds (L-2) to (L-10) shown in the compound (L) column of Table 2. Furthermore, compounds (1-29) and (1-32) were each synthesized by the same method as in the synthesis of compound (1-6), except that 5.7 mmol of compound (a-1) was changed to 5.7 mmol of compound (a-2) shown in the compound (a) column of Table 2, and 65.3 mmol of compound (L-1) was changed to compound (L-2) or (L-7) shown in the compound (L) column of Table 2. The molar amounts of the compounds added used in the synthesis of compounds (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32) were all the same as the molar amounts of the corresponding components added used in the synthesis of compound (1-6).

[0132] Table 2 shows the types of compounds (a) and (b) used in the synthesis of each of the compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32); the type and molecular weight (Mw) of compound (L) (secondary amine) used in the synthesis of each of the compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32); the yield of compound (b) obtained in each reaction (r-1) and the yield from compound (a); the type of compound (1) and the values ​​of X, R 1 , R 2Table 3 also shows the yield of compound (c) obtained in each reaction (r-2) and the yield from compound (b), the yield of compound (d) obtained in each reaction (r-3) and the yield from compound (c), and the yield of compound (1) obtained in each reaction (r-4) and the yield from compound (d).

[0133]

[0134]

[0135] 1 H-NMR (proton nuclear magnetic resonance spectrometer) or 19 Using F-NMR (fluorine-19 nuclear magnetic resonance spectrometer), the synthesized compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32) were analyzed. 1 H-NMR spectrum or 19 The F-NMR spectrum was measured. 1 For the measurement of H-NMR spectrum, DMSO (dimethyl sulfoxide) was used as a deuterated solvent, and the magnetic field strength was set to 600 MHz. 19 For F-NMR spectrum measurement, DMSO (dimethyl sulfoxide) was used as a deuterated solvent. The magnetic field strength was set to 564 MHz. C6F6 (base peak: 164.9 ppm) was used as an internal standard.

[0136] Among the synthesized compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32), the compounds (1-6) and (1-32) are representative examples. 1 The chemical shift values ​​of the H-NMR spectrum are shown below. 1 From the chemical shift values ​​of the H-NMR spectrum, it was confirmed that compounds (1-6) and (1-32) were obtained. Compound (1-6): 1 H-NMR (600MHz, DMSO-d6, ppm) δ=7.20-7.38 (m, 8H), 7.05-7.10 (m, 8H), 6.77-6.84 (m, 4H) Compound (1-32): 1 ​H-NMR (600MHz, DMSO-d6) δ (ppm) = 7.21-7.38 (m, 8H), 7.04-7.11 (m, 8H)

[0137] In addition, compounds (1-15), (1-16), (1-23), (1-24), (1-25), and (1-26) 19 The chemical shift values ​​of the F-NMR spectrum are shown below. 19 From the chemical shift values ​​of the F-NMR spectrum, it was confirmed that compounds (1-15), (1-16), (1-23), (1-24), (1-25), and (1-26) were obtained. Compound (1-15): 19 F-NMR (564MHz, DMSO-d6, C6F6 = 164.9ppm) δ (ppm) = -135.9 (8F), -152.7 (4F), -163.7 (8F) Compound (1-16): 19 F-NMR (564MHz, DMSO-d6, C6F6 = 164.9ppm) δ (ppm) = -135.8 (8F), -140.4 (8F) Compound (1-23): 19 F-NMR (564MHz, DMSO-d6, C6F6 = 164.9ppm) δ (ppm) = -135.9 (4F), 152.8 (2F), -163.8 (4F) Compound (1-24): 19 F-NMR (564MHz, DMSO-d6, C6F6 = 164.9ppm) δ (ppm) = -135.8 (4F), -140.5 (4F) Compound (1-25): 19 F-NMR (564MHz, DMSO-d6, C6F6 = 164.9ppm) δ (ppm) = -135.8 (6F) Compound (1-26): 19 F-NMR (564MHz, DMSO-d6, C6F6 = 164.9ppm) δ (ppm) = -135.7 (4F), -140.4 (2F)

[0138] Compound (1-29): 19 F-NMR (564MHz, DMSO-d6, C6F6 = 164.9ppm) δ (ppm) = -135.9 (8F), -140.4 (4F), -152.8 (2F), -163.8 (4F)

[0139] <Measurement of Electrical Conductivity> The electrical conductivity was evaluated for each of the compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32) obtained in Examples 1 to 10. The evaluation was carried out at a temperature of 20°C and a humidity of 40% RH, unless otherwise specified.

[0140] A glass substrate was prepared with two ITO strips spaced 1 mm apart as electrodes for the thin film. A thin film, a mixed layer of a host material and a dopant material, was formed on this glass substrate by mixed thermal evaporation using a high-vacuum chamber. Compound (HT1) (synthesized in-house) was used as the host material. Compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32) obtained in Examples 1 to 10 were used as dopant materials. In Comparative Example 1, a compound represented by the following formula (HI) (synthesized in-house) (hereinafter sometimes referred to as compound (HI)) was used as the dopant material. The doping concentration was 5 mol% in all cases, and the thin film thickness was 50 nm. The electrical conductivity of the thin film was measured from the current-voltage characteristics of the thin film, and the results are shown in Table 4.

[0141]

[0142]

[0143] Compounds (1-6), (1-15), (1-16), (1-21), (1-23), (1-24), (1-25), (1-26), (1-29), and (1-32) are all compound (1) represented by formula (1), and were able to achieve conductivity one order of magnitude higher than that of compound (HI). 1 and R 2 It can be seen that the conductivity is improved when at least one of R has an electron-withdrawing group. 1 and R 2It can be seen that the conductivity is further improved when at least one of R has a cyano group. 1 and R 2 It can be seen that the greater the number of cyano groups, the higher the electrical conductivity.

[0144] The compound according to the present invention can be used, for example, as a hole transport material. Furthermore, the compound and hole transport material according to the present invention can be suitably used, for example, as a hole transport material for an electroluminescence device. Furthermore, the electroluminescence device according to the present invention can be used, for example, in a display device, a lighting device, etc.

Claims

1. A compound represented by formula (1). (In the formula (1), R 1 and R 2 each independently represents a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to 20 ring carbon atoms, a substituted or unsubstituted heteroalkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted aralkyl group having from 7 to 30 carbon atoms, a substituted or unsubstituted aryl group having from 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having from 3 to 30 carbon atoms, or a combination thereof; and X represents an oxygen atom or a sulfur atom.

2. In the formula (1), R 1 and R 2 and each independently represent a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted biphenyl group.

3. In the formula (1), R 1 and R 2 at least one of the following has at least one electron-withdrawing group, and the electron-withdrawing group is selected from the group consisting of a halogeno group, a nitroso group, a nitro group, a carbonyl group, a carboxy group, an SF5 group, a cyano group, an isocyano group, an SCN group, an OCN group, a boryl group, a phosphonooxy group, a nitrogen-containing heteroaromatic group, and combinations thereof.

4. The compound of claim 3, wherein the electron-withdrawing group is selected from the group consisting of a fluoro group, a CF3 group, an OCF3 group, an SF5 group, a cyano group, an isocyano group, an SCN group, an OCN group, a pyrimidine group, a triazine group, and combinations thereof.

5. In the formula (1), R 1 and R 2 each independently represents any one selected from the group consisting of a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms; an unsubstituted phenyl group; an unsubstituted biphenyl group; and a phenyl group or biphenyl group substituted with at least one selected from the group consisting of a halogeno group, a nitroso group, a nitro group, a carbonyl group, a carboxy group, an SF5 group, a cyano group, an isocyano group, an SCN group, an OCN group, a boryl group, and a phosphonooxy group.

6. In the formula (1), R 1 and R 2 each independently represent any one selected from the group consisting of a phenyl group, a methoxyphenyl group, a p-methylphenyl group, a 2,6-diisopropylphenyl group, a biphenyl group, a polyfluorophenyl group, a nitrophenyl group, a trifluoromethylphenyl group, a trifluoromethoxyphenyl group, a bis(trifluoromethyl)phenyl group, a bis(trifluoromethoxy)phenyl group, a 4-cyanotetrafluorophenyl group, and a phenyl group or a biphenyl group substituted with at least one selected from the group consisting of a fluoro group, a CF group, a cyano group, an isocyano group, and combinations thereof.

7. In the formula (1), R 1 and R 2 and each independently represent a group represented by any one of formulas (A1) to (A20). (In the formulas (A1) to (A20), * represents a bond.) 8. In the formula (1), R 1 and R 2 The compound according to claim 7, wherein at least one of the above has two or more cyano groups.

9. A hole transporting material comprising the compound of claim 1.

10. An electroluminescent device comprising a first electrode, a second electrode, and at least one organic layer provided between the first electrode and the second electrode, the organic layer containing the compound represented by formula (1) according to claim 1.

11. The electroluminescent device according to claim 10, wherein the organic layer is at least one layer selected from the group consisting of a hole injection layer, a hole transport layer, a light-emitting layer, and an electron blocking layer.

12. The electroluminescent device according to claim 11, wherein the organic layer is any one of a hole injection layer, a hole transport layer, and an electron blocking layer, and the organic layer contains only the compound represented by formula (1).

13. The electroluminescent device according to claim 11, wherein the organic layer is any one of a hole injection layer, a hole transport layer, and an electron blocking layer, and the organic layer contains the compound represented by formula (1) and at least one hole transport material selected from the group consisting of compounds having a triarylamine unit, spirobifluorene compounds, pentacene compounds, oligothiophene compounds, oligophenyl compounds, oligophenylene vinyl compounds, oligofluorene compounds, porphyrin complexes, and metal phthalocyanine complexes, and the content ratio of the compound represented by formula (1) to the hole transport material is 10,000:1 or more and 1:10,000 or less in molar ratio.

14. The electroluminescent device according to claim 13, comprising: a first light-emitting unit including at least a first light-emitting layer; a second light-emitting unit including at least a second light-emitting layer; and a charge generation layer provided between the first light-emitting unit and the second light-emitting unit, wherein the charge generation layer includes an n-type charge generation layer and a p-type charge generation layer; and the p-type charge generation layer is an organic layer containing the compound represented by formula (1).

15. The electroluminescent device according to claim 14, wherein the p-type charge generation layer contains the compound represented by formula (1) and at least one hole transporting material selected from the group consisting of compounds having a triarylamine unit, spirobifluorene compounds, pentacene compounds, oligothiophene compounds, oligophenyl compounds, oligophenylene vinyl compounds, oligofluorene compounds, porphyrin complexes, and metal phthalocyanine complexes, and the molar ratio of the compound represented by formula (1) to the hole transporting material is 10,000:1 or more and 1:10,000 or less.

16. The electroluminescent device according to claim 14, wherein the charge generation layer further includes a buffer layer provided between the n-type charge generation layer and the p-type charge generation layer, and the buffer layer contains the compound represented by formula (1).

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