Anthracene derivative, organic electroluminescence element, display device, and lighting device

Abstract

To provide an anthracene derivative with high electron affinity and excellent light-emitting properties.SOLUTION: An anthracene derivative is represented by the general formula (1) in the figure. [In the formula: X represents hydrogen, a cyano group, or the like; and R represents hydrogen, a C1-10 alkyl group, or the like.]SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an anthracene derivative, an organic electroluminescence (hereinafter, electroluminescence (field emission) may be abbreviated as "EL") element, a display device, and a lighting device. [Background technology]

[0002] Fused ring compounds such as anthracene derivatives and tetracene derivatives have attracted attention as functional electronic device materials due to their electronic properties. These fused ring compounds have been widely used as light-emitting layer materials in organic electroluminescence devices because they exhibit high light emission quantum yields (see, for example, Non-Patent Documents 1 to 3).

[0003] In addition, by utilizing triplet-triplet annihilation, the above-mentioned fused ring compounds can also extract the triplet excited state generated by current excitation as light emission from the singlet excited state (see, for example, Non-Patent Documents 3 and 4).

[0004] Taking advantage of this feature, in recent years, vigorous efforts have been made to make organic electroluminescence elements emit light at low applied voltages. For example, it has been reported that by using rubrene, a tetracene derivative, as a donor and fullerene, which has a large electron affinity, as an acceptor, the energy of an exciplex formed at the interface between them can be extracted as light emission from the singlet excited state of rubrene through triplet-triplet annihilation in an organic electroluminescence element (see, for example, Non-Patent Documents 3 and 5).

[0005] In an organic electroluminescence element combining rubrene and an acceptor, the energy difference between the ionization potential, which is the energy of the highest occupied molecular orbital (HOMO) of rubrene, and the lowest unoccupied molecular orbital (LUMO) of the fullerene, which is the acceptor, is small, and an excited state that contributes to light emission can be generated with a low applied voltage because the small energy difference can form an excited state. In a typical organic electroluminescence element, charges are recombined in one molecule, so an applied voltage equivalent to the band gap energy is required to generate an excited state that contributes to light emission, but an organic electroluminescence element using an exciplex of rubrene and an acceptor can emit light at a lower voltage (for example, see Non-Patent Documents 1 to 3 and 5).

[0006] However, when tetracene derivatives such as rubrene are used as materials in which triplet-triplet annihilation occurs, the peak wavelength of the material is 550 nm or more, so only orange or red light can be emitted. To obtain blue or green light, fused ring compounds with shorter emission wavelengths, such as anthracene derivatives, are required. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Xiangyang Tang, Qing Bai, Tong Shan, Jinyu Li, Yu Gao, Futong Liu, Hui Liu, Qiming Peng, Bing Yang, Feng Li, and Ping Lu,Advanced Functional Materials,28:1705813,DOI:10.1002 / adfm.201705813 [Non-Patent Document 2] Futong Liu, 8 others, "Journal of Materials Chemistry C", Volume 7, 2019, p14881, DOI:10.1039 / c9tc05040j [Non-Patent Document 3] Sebastian Engmann and 5 others, "Nature Communications", Vol. 10, 2019, p. 227, doi.org / 10.1038 / s41467-018-08075-z [Non-Patent Document 4] Youn Jue Bae, 9 others, "Journal of the American chemical society", 2018, Volume 140, p15140, DOI:10.1021 / jacs.8b07498 [Non-Patent Document 5] Seiichiro Izawa, 3 others, DOI:10.26434 / chemrxiv.14685417.v1 Summary of the Invention [Problem to be solved by the invention]

[0008] In the above Non-Patent Documents 1 and 2, an anthracene derivative with a relatively large electron affinity can be realized by introducing an acceptor substituent such as a cyano group or a triphenyltriazine group into the anthracene derivative. By utilizing the exciplex formed between these anthracene derivatives and a donor material, it is possible to realize a blue or green organic electroluminescence element that operates at a low voltage. However, in order to further reduce the voltage, an anthracene derivative with a larger electron affinity is needed.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an anthracene derivative having a large electron affinity and excellent luminescence properties. Another object of the present invention is to provide an organic EL device, a display device and a lighting device which use such an anthracene derivative and have a low driving voltage. [Means for solving the problem]

[0010] The inventors conducted extensive research into anthracene derivatives having large electron affinity and excellent luminescent properties, and discovered that the above-mentioned problems could be resolved by connecting a phthalonitrile moiety (having two or more cyano groups) and a triphenyltriazine moiety to an anthracene ring, thereby completing the present invention. That is, the anthracene derivative, organic electroluminescence element, display device, and lighting device of the present invention that solve the above problems are generally configured as follows.

[0011] [1] The following general formula (1): [ka] [In general formula (1), X's each independently represent hydrogen or a monovalent substituent selected from the group consisting of a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may be joined together to form a ring, with the proviso that at least two of X's are cyano groups, R's are each independently hydrogen or a monovalent substituent selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may be joined together to form a ring. The anthracene derivative of the present invention described in the above [1] has a large electron affinity (for example, a calculated electron affinity value of 2 eV or more) and is excellent in luminescence properties.

[0012] [2] An organic electroluminescence element comprising an anode, a light-emitting layer, and a cathode in this order, An organic electroluminescence device, wherein the light-emitting layer contains the anthracene derivative according to [1]. The organic electroluminescence element described in the above item [2] has a low driving voltage.

[0013] [3] The organic electroluminescence element according to [2], wherein the light-emitting layer further contains a material having a smaller ionization energy than the anthracene derivative. The organic electroluminescence element described in [3] above has an even lower driving voltage.

[0014] [4] A hole transport layer is further provided between the anode and the light emitting layer, The organic electroluminescence device according to [2] or [3], wherein the hole transport layer contains a material having a smaller ionization energy than the anthracene derivative. The organic electroluminescence element described in [4] above has an even lower driving voltage.

[0015] [5] A display device comprising the organic electroluminescence element according to any one of [2] to [4]. The display device of the present invention described in [5] above emits light at a low applied voltage.

[0016] [6] A lighting device comprising the organic electroluminescence element according to any one of [2] to [4]. The lighting device of the present invention described in [6] above emits light at a low applied voltage. Effect of the Invention

[0017] According to the present invention, it is possible to provide an anthracene derivative having a large electron affinity and excellent luminescence properties. Furthermore, according to the present invention, it is possible to provide an organic EL device, a display device, and a lighting device which use such an anthracene derivative and have a low driving voltage. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing an example of the structure of an organic EL element of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the energy levels in an example of an organic EL element of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing light emission from a singlet excited state utilizing energy transfer from an exciplex and triplet-triplet annihilation, which is an example of the light emission mechanism of the anthracene derivative of the present invention. [Figure 4] FIG. 1 is a schematic diagram showing an example of the structure of a general organic EL element and the energy levels therein. [Diagram 5] FIG. 2 is a schematic diagram showing another example of the structure of the organic EL element of the present invention. [Figure 6] FIG. 2 is a schematic diagram showing light emission utilizing energy transfer from an exciplex, triplet-triplet annihilation, and energy transfer from a singlet excited state, which is another example of the light emission mechanism of the anthracene derivative of the present invention. [Figure 7] NMR spectrum of the anthracene derivative represented by formula (1-1). [Figure 8] 1 is a graph showing the results of measuring (a) current density-voltage characteristics, (b) luminance-voltage characteristics, and (c) EL spectra of various organic EL elements produced in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The anthracene derivative, the organic electroluminescence element, the display device, and the lighting device of the present invention will be illustrated in detail below based on their embodiments. In addition, a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

[0020] <Anthracene derivatives> The anthracene derivative of the present invention is represented by the following general formula (1): [ka] [In general formula (1), X's each independently represent hydrogen or a monovalent substituent selected from the group consisting of a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may be joined together to form a ring, with the proviso that at least two of X's are cyano groups, R are each independently hydrogen or a monovalent substituent selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may be joined together to form a ring.

[0021] The anthracene derivative represented by the above general formula (1) has a structure in which a phthalonitrile moiety (having two or more cyano groups) and a triphenyltriazine moiety are connected to an anthracene ring, and has a large electron affinity (for example, a calculated electron affinity value of 2 eV or more) and excellent luminescence characteristics.

[0022] In the above general formula (1), X's are each independently hydrogen or a monovalent substituent selected from the group consisting of a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may combine together to form a ring, with the proviso that at least two of X's are cyano groups (-CN). By connecting a phthalonitrile moiety having two or more cyano groups, which are acceptor substituents, to an anthracene ring, the electron affinity is increased, and an anthracene derivative with excellent luminescence properties can be obtained.

[0023] The number of cyano groups among the five Xs is 2 or more, and is preferably 3 or less, and particularly preferably 2. When the number of cyano groups among the five Xs is 3 or less, the emission wavelength becomes shorter, and when the number is 2, the emission wavelength becomes even shorter. In addition, any one of X may be a cyano group, but it is preferable that at least one of X at the meta position relative to the bonding position to the anthracene ring is a cyano group, and it is more preferable that both of X at the meta positions are cyano groups.

[0024] In addition, R in the above general formula (1) are each independently hydrogen or a monovalent substituent selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may be joined together to form a ring. By linking the triphenyltriazine moiety to the anthracene ring, the electron affinity is further increased.

[0025] Regarding X and R in the above general formula (1), examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a nonyl group, examples of the alkoxy group having 1 to 10 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group, examples of the alkylthio group having 1 to 10 carbon atoms include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, a heptylthio group, an octylthio group, and a nonylthio group, examples of the alkylamino group having 1 to 10 carbon atoms include a methylamino group, an ethylamino group, a propylamino group, a butylamino group, a pentylamino group, a hexylamino group, and a heptylamino group. Examples of the acyl group having 2 to 10 carbon atoms include an acetyl group, a propionyl group, a butyryl group, etc. Examples of the aralkyl group having 7 to 20 carbon atoms include a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group, etc. Examples of the substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms include a phenyl group, a 2,6-xylyl group, a mesityl group, a duryl group, a biphenyl group, a terphenyl group, a naphthyl group, an anthryl group, a pyrenyl group, a toluyl group, an anisyl group, a fluorophenyl group, a diphenylaminophenyl group, a dimethylaminophenyl group, a diethylaminophenyl group, a pyridylphenyl group, a phenanthrenyl group, etc. Examples of the substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms include a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a triazinyl group, etc.

[0026] Specific examples of the anthracene derivative represented by the above general formula (1) include compounds represented by the following structural formulas (1-1) to (1-5). [ka]

[0027] The anthracene derivative represented by the above general formula (1) can be obtained by synthesis using a known method. The synthesis method of the anthracene derivative represented by the general formula (1) is not particularly limited, but an example is shown below.

[0028] First, a benzene derivative having a halogen group (also called a "halogeno group") and multiple carboxyl groups is prepared. Examples of the benzene derivative include 5-bromoisophthalic acid, 4-bromoisophthalic acid, 2-bromoisophthalic acid, and 2-bromoterephthalic acid. The carboxyl groups of the benzene derivative having a halogen group and multiple carboxyl groups are chlorinated to obtain a carboxylic acid chloride (acid chloride). Here, the chlorination of the carboxyl groups is carried out using oxalyl chloride [(COCl) 2 ], thionyl chloride (SOCl 2 ) etc. can be used. Next, the carboxylic acid chloride is amidated to obtain an amide compound. Here, an amine compound such as t-butylamine can be used for the amidation of the carboxylic acid chloride. Next, the amide compound is converted to a nitrile to obtain a benzene derivative having a halogen group and a plurality of cyano groups. Here, the nitrile conversion of the amide compound is performed using thionyl chloride (SOCl 2 ) etc. can be used. Next, a boryl group such as a pinacolatoboryl group is introduced into the benzene derivative having a halogen group and a plurality of cyano groups to obtain an organoboron compound having a plurality of cyano groups. Here, bis(pinacolato)diboron or the like can be used to introduce the boryl group.

[0029] On the other hand, a triazine compound having a halogenated phenyl group and two phenyl groups is prepared. An example of the triazine compound is 2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine. The triazine compound is coupled with a boron compound having an anthracene ring, such as 9-anthraceneboronic acid, via Suzuki coupling to obtain an anthracene derivative having a triphenyltriazine moiety. Next, the anthracene derivative having a triphenyltriazine moiety is brominated with N-bromosuccinimide (NBS) or the like to obtain an anthracene derivative having a triphenyltriazine moiety and a bromo group.

[0030] The anthracene derivative represented by the above general formula (1) can be produced by Suzuki coupling the organoboron compound having multiple cyano groups obtained as above with an anthracene derivative having a triphenyltriazine moiety and a bromo group. Here, the Suzuki coupling of the organoboron compound having multiple cyano groups with an anthracene derivative having a triphenyltriazine moiety and a bromo group can be carried out, for example, in the presence of a ligand such as S-Phos{dicyclohexyl(2',6'-dimethoxy-[1,1'-biphenyl]-2-yl)phosphine}, a palladium catalyst, and a base.

[0031] The Suzuki coupling can also be carried out using, for example, palladium acetate [Pd(OAc) 2 ], Pd 2 (dba) 3 , Pd(Ph 3 P) 4 , Pd(dppf)Cl 2 The reaction can be carried out in the presence of a palladium catalyst such as potassium phosphate, sodium carbonate, sodium bicarbonate or the like.

[0032] <Organic electroluminescence element> The organic electroluminescent element of the present invention is an organic electroluminescent element comprising an anode, an emitting layer, and a cathode in this order, and is characterized in that the emitting layer contains an anthracene derivative represented by the above general formula (1).

[0033] In the organic electroluminescent element of the present invention, since the anthracene derivative represented by the above general formula (1) has a large electron affinity, it is possible to obtain light emission at a low applied voltage by including the anthracene derivative represented by the general formula (1) in the light-emitting layer.

[0034] In the organic electroluminescence element of the present invention, since the anthracene derivative represented by the above general formula (1) has a large electron affinity, the anthracene derivative and a material having a smaller ionization energy than the anthracene derivative are adjacent to each other so as to form an exciplex (i.e., the light-emitting layer contains the anthracene derivative represented by general formula (1), and a layer adjacent to the light-emitting layer, such as a hole-transporting layer, contains a material having a smaller ionization energy than the anthracene derivative), or are mixed together (i.e., the light-emitting layer contains the anthracene derivative represented by general formula (1) and a material having a smaller ionization energy than the anthracene derivative), making it possible to obtain light emission at a lower applied voltage. Here, the ionization energies (also referred to as "ionization potentials (IP)") of the anthracene derivative represented by general formula (1) and of materials having smaller ionization energies than the anthracene derivative are calculated values, and are mainly calculated by density functional theory using the Gaussian 09 program under the following conditions [B3LYP / 6-31G (d,p)].

[0035] Next, one embodiment of the organic electroluminescence element of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic diagram showing an example of the structure of the organic EL element of the present invention. The organic EL element 1 shown in Fig. 1 has a laminated structure in which an anode 3, a hole injection layer 4, a hole transport layer 5, a light emitting layer 6, an electron injection layer 7, and a cathode 8 are formed in this order on a substrate 2.

[0036] The energy levels in the organic electroluminescence element 1 shown in Fig. 1 are shown in Fig. 2. In the organic EL element 1, electrons injected into the anthracene derivative (light-emitting layer 6) and holes injected into the hole transport layer 5, which has a smaller ionization potential than the anthracene derivative, form an exciplex, causing a current to flow and emitting light. At this time, the voltage required for emitting light is determined by the energy difference between the electron affinity (EA) of the anthracene derivative and the ionization potential (IP) of the material of the hole transport layer 5, but since the anthracene derivative, which is the light-emitting layer 6, has a large electron affinity, this energy difference is small and the externally applied voltage required for emitting light is reduced.

[0037] Next, the process of energy transfer from the formation of an exciplex to light emission is shown in Figure 3. The small external voltage required to form an exciplex means that the energy of the light from the resulting exciplex is not large. However, if the triplet energy of the anthracene derivative involved in the formation of the exciplex is smaller than the energy of the excited state of this exciplex, the energy of the exciplex is transferred to the triplet excited state of the anthracene derivative. It is well known that anthracene derivatives generate a singlet excited state by utilizing triplet-triplet annihilation, so by utilizing this characteristic, a singlet excited state can be generated and light can be obtained from it. Here, the light emitted from the singlet excited state has a larger energy than the light from the exciplex.

[0038] Next, the structure and energy levels of a general organic electroluminescence element that does not utilize the formation of an exciplex are shown in FIG. 4. The organic electroluminescence element shown in FIG. 4 has a laminated structure in which an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode are formed in this order on a substrate. In a general organic electroluminescence element, an external voltage close to the band gap of the light emitting layer material needs to be applied because the light emitting layer material directly recombines electrons and holes to form an excited state. This external voltage is higher than the voltage required for light emission in the organic EL element shown in FIG. 1 to FIG. 3. In addition, if a large number of materials with different energy levels are used in the organic EL element, an energy difference occurs in the device, leading to an increase in voltage. Therefore, in order to reduce the voltage, it is effective to use an exciplex of an anthracene derivative and another material as shown in FIG. 1 to FIG. 3. However, since the anthracene derivative of the present invention is expected to exhibit high light emitting efficiency, it can also be used in the light emitting layer or the like in the form shown in FIG. 4.

[0039] In the organic EL elements shown in FIGS. 1 to 3, it is also possible to insert another electron transport layer material between the light emitting layer 6 and the electron injection layer 7 so as not to create an energy barrier.

[0040] Furthermore, the organic EL element 1 of this embodiment may be an organic EL element having an inverted structure in which a cathode 8 is provided on a substrate 2, as shown in Fig. 5. The organic EL element 1 shown in Fig. 5 has a laminated structure in which a cathode 8, an electron injection layer 7, an emitting layer 6, a hole transport layer 5, a hole injection layer 4, and an anode 3 are formed in this order on the substrate 2.

[0041] The organic EL element 1 of this embodiment may be an organic-inorganic hybrid organic electroluminescent element (HOILED element) in which some of the layers constituting the organic EL element are formed using inorganic compounds.

[0042] "substrate" The material of the substrate 2 may be a resin material, a glass material, or the like. Examples of the resin material used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, polyarylate, etc. When a resin material is used as the material for the substrate 2, it is preferable because an organic EL element 1 having excellent flexibility can be obtained. Examples of the glass material used for the substrate 2 include quartz glass and soda glass.

[0043] When the organic EL element 1 is of a bottom emission type, the material of the substrate 2 is a transparent substrate. When the organic EL element 1 is of a top emission type, not only a transparent substrate but also an opaque substrate may be used as the material of the substrate 2. Examples of opaque substrates include a substrate made of a ceramic material such as alumina, a substrate in which an oxide film (insulating film) is formed on the surface of a metal plate such as stainless steel, and a substrate made of a resin material.

[0044] The average thickness of the substrate 2 can be determined depending on the material of the substrate 2, and is preferably 0.1 to 30 mm, and more preferably 0.1 to 10 mm. The average thickness of the substrate 2 can be measured with a digital multimeter and a vernier caliper.

[0045] "anode" The anode 3 shown in FIG. 1 is formed on and in direct contact with the substrate 2, but in the case of an organic EL element having an inverted structure as shown in FIG. The material of the anode 3 is ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), In 3 O 3 , SnO 2 , Sb-containing SnO 2 Examples of the conductive material for the anode 3 include oxide conductive materials such as Al-containing ZnO, etc. Among these, it is preferable to use ITO, IZO, or FTO as the material for the anode 3. The average thickness of the anode 3 is not particularly limited, but is preferably from 10 to 500 nm, and more preferably from 100 to 200 nm. The average thickness of the anode 3 can be measured by a stylus step gauge or spectroscopic ellipsometry.

[0046] "Hole injection layer" The hole injection layer 4 may be made of an inorganic material or an organic material. Inorganic materials are more stable than organic materials, and therefore, it is easier to obtain high resistance to oxygen and water compared to the case where an organic material is used. The inorganic material is not particularly limited, but for example, vanadium oxide (V 2 O 5 ), molybdenum oxide (MoO 3 ), ruthenium oxide (RuO 2 ) can be used alone or in combination. Examples of organic materials that can be used include dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ). Polymer materials such as poly(3,4-ethylenedioxythiophene) (PEDOT) can also be used. The average thickness of the hole injection layer 4 is not particularly limited, but is preferably from 1 to 1000 nm, and more preferably from 5 to 50 nm. The average thickness of the hole injection layer 4 can be measured during deposition using a quartz crystal thickness gauge.

[0047] "Hole transport layer" As described above, the hole transport layer 5 preferably contains an organic compound that forms an exciplex with an anthracene derivative, and more preferably contains a material having a smaller ionization energy than the anthracene derivative represented by the general formula (1). As described later, since the light emitting layer 6 contains the anthracene derivative represented by the general formula (1), when the hole transport layer 5 contains a material having a smaller ionization energy than the anthracene derivative, an exciplex is formed at the interface between the light emitting layer 6 and the hole transport layer 5, and the driving voltage of the organic EL device 1 can be further reduced.

[0048] As the hole transporting organic material used in the hole transport layer 5, it is preferable to use a material having a small IP and EA (a material having a high donor property) among materials forming an exciplex. Specifically, a material having a molecular structure having a high donor property, such as triarylamine, carbazole, phenoxazine, phenazine, acridine, azadibenzopyrene, or julolidine skeleton, is preferable. More specifically, the following m-MTDATA, TPT-1, TAPC, TPDI, HN-D1, HN-D2, N-TPA, EH44, PHZ-2Naph, TBDI, HT-01, N-DPA, spiro-MeO-TAD, Tris-PCz, α-NPD, TcTa, 2-SF-DMAC, 2-SF-PHX, SF-BCz, FATPA, and the like are preferable. [ka] [ka] [ka]

[0049] The calculated IP / EA values ​​of the above highly donor materials are shown in Table 1.

[0050] [Table 1]

[0051] The above IP / EA calculation values ​​were mainly calculated by the density functional method using the Gaussian 09 program under the following conditions [B3LYP / 6-31G (d,p)]. We also show the measured IP values ​​for several materials, as determined by ultraviolet photoelectron spectroscopy (UPS). As shown, there is a strong correlation between the measured and calculated IP values.

[0052] The organic compound contained in the hole transport layer 5 preferably has a calculated ionization potential (IP) of 3.74 to 5.08 eV calculated using density functional theory, or an actually measured ionization potential (IP) of 4.4 to 5.8 eV. The average thickness of the hole transport layer 5 is not particularly limited, but is preferably from 10 to 150 nm, and more preferably from 20 to 100 nm. The average thickness of the hole transport layer 5 can be measured by, for example, a stylus step gauge or spectroscopic ellipsometry.

[0053] "Light-emitting layer" As described above, the light-emitting layer 6 contains the anthracene derivative of the present invention. The light-emitting layer 6 may further contain a material having a smaller ionization energy than the anthracene derivative. When the light-emitting layer 6 contains the anthracene derivative represented by the general formula (1) and a material having a smaller ionization energy than the anthracene derivative, an exciplex is formed.

[0054] As materials having smaller ionization energy than the anthracene derivative, materials having small IP and EA (materials with high donor properties) as listed in the section "Hole transport layer 5" are preferable, and m-MTDATA, TPT-1, TAPC, TPDI, HN-D1, HN-D2, N-TPA, EH44, PHZ-2Naph, TBDI, HT-01, N-DPA, spiro-MeO-TAD, Tris-PCz, α-NPD, TcTa, 2-SF-DMAC, 2-SF-PHX, SF-BCz, FATPA, and the like are more preferable. Here, the content of the material having a smaller ionization energy than the anthracene derivative in the light-emitting layer 6 is preferably in the range of 10 to 50% by mass with respect to the anthracene derivative.

[0055] In the light-emitting layer 6, it is possible to extract light emitted from an anthracene derivative as shown in Fig. 3, while it is also possible to extract light emitted from another light-emitting dopant by using an anthracene derivative (or an exciplex) as a host for the light-emitting layer 6 as shown in Fig. 6. In this case, a phosphorescent material such as an iridium complex or platinum complex, a fluorescent material, a thermally activated delayed fluorescent material, or the like may be mixed into the light-emitting layer 6 as a dopant for the host. The mixing ratio of the dopant is preferably 20% by mass or less, more preferably 10% by mass or less, relative to the anthracene derivative (or an exciplex).

[0056] The fluorescent material is 8-hydroxyquinoline aluminum (Alq 3 ), tris(4-methyl-8-quinolinolato)aluminum(III) (Almq 3 ), 8-hydroxyquinoline zinc (Znq 2), and various metal complexes; benzene-based compounds such as distyrylbenzene (DSB) and diaminodistyrylbenzene (DADSB); naphthalene-based compounds such as naphthalene and Nile Red; phenanthrene-based compounds such as phenanthrene; chrysene-based compounds such as chrysene and 6-nitrochrysene; perylene-based compounds such as perylene and N,N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-di-carboximide (BPPC); coronene-based compounds such as coronene; anthracene-based compounds such as anthracene and bisstyrylanthracene; pyrene-based compounds such as pyrene and BD-1; pyran-based compounds such as 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM); acridine-based compounds such as acridine; stilbene-based compounds such as stilbene; thiophene-based compounds such as 2,5-dibenzoxazolethiophene; benzyl benzoxazole-based compounds such as benzoxazole; benzimidazole-based compounds such as benzimidazole; benzothiazole-based compounds such as 2,2'-(para-phenylenedivinylene)-bisbenzothiazole; butadiene-based compounds such as bistyryl(1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene; naphthalimide-based compounds such as naphthalimide; coumarin-based compounds such as coumarin; perinone-based compounds such as perinone; oxadiazole-based compounds such as oxadiazole; aldazine-based compounds; cyclopentadiene-based compounds such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP); quinacridone-based compounds such as quinacridone and quinacridone red; pyridine-based compounds such as pyrrolopyridine and thiadiazolopyridine; and spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene.

[0057] Examples of the thermally activated delayed fluorescent material include 2,4,5,6-tetra(9-carbazole)-isophthalonitrile (4CzIPN), 4,5-di(9-carbazole)-phthalonitrile (2CzPN), 3,4,5,6-tetra(9-carbazole)-phthalonitrile (4CzPN), 2,3,5,6-tetra(9-carbazole)-terephthalonitrile (4CzTPN), 2,3,5,6-tetra(3,6-dimethyl-9-carbazole)-terephthalonitrile (4CzTPN-Me), 2,3,5,6-tetra(3,6-diphenyl-9-carbazole)-terephthalonitrile (4CzTPN-Ph), and further include compounds described in JP2012-193352A and WO2011 / 070963A.

[0058] The average thickness of the light-emitting layer 6 is not particularly limited, but is preferably from 10 to 150 nm, and more preferably from 20 to 100 nm. The average thickness of the light-emitting layer 6 may be measured by a stylus-type step gauge, or may be measured by a quartz crystal thickness gauge during the deposition of the light-emitting layer 6.

[0059] "Electron injection layer" The electron injection layer 7 can be made of any of a variety of materials having a low work function, such as alkali metals and alkaline earth metals; compounds containing a metal having a low work function, such as lithium quinoline, lithium fluoride, cesium carbonate, and calcium carbonate; a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (2); or a compound having a structure represented by the following general formula (3).

[0060] [ka] (In general formula (2), R 1 represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent linear or cyclic hydrocarbon group, which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. 1 is an integer from 1 to 4.

[0061] [ka] (In general formula (3), X 1 , X 2 are the same or different and each represents a nitrogen atom, an oxygen atom, a sulfur atom, or a divalent linking group which may have a substituent. L represents a direct bond or a p-valent linking group. 2 represents a number of 0 or 1, and p represents a number of 1 to 4. q represents a number of 0 or 1, and when p is 1, q is 0. R 2 ~R 4 m may be the same or different and represents a monovalent substituent. 1 ~m 3 R may be the same or different and represents a number from 0 to 3. 2 ~R 4 X 1 , X 2 may be bonded to form a ring structure, R 2 If there are multiple R 2 may be bonded to form a ring structure. 3 If there are multiple R 3 may be bonded to form a ring structure. 4 If there are multiple R 4 may be bonded to form a ring structure.

[0062] R in the above general formula (2) 1 represents an aromatic hydrocarbon group which may have a substituent, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent chain or cyclic hydrocarbon group, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. The aromatic hydrocarbon group and aromatic heterocyclic group preferably have 3 to 30 carbon atoms, more preferably have 4 to 24 carbon atoms, and further preferably have 5 to 20 carbon atoms. Examples of aromatic hydrocarbon groups include compounds consisting of only one aromatic ring, such as benzene; compounds in which multiple aromatic rings, such as biphenyl and diphenylbenzene, are directly bonded to each other via one carbon atom; and groups formed by removing one to four hydrogen atoms from any of the aromatic rings of condensed ring aromatic hydrocarbon compounds, such as naphthalene, anthracene, phenanthrene, and pyrene. Examples of the aromatic heterocyclic group include compounds consisting of only one aromatic heterocycle, such as thiophene, furan, pyrrole, oxazole, oxadiazole, thiazole, thiadiazole, imidazole, pyridine, pyrimidine, pyrazine, and triazine; compounds in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded to each other via one carbon atom (such as bipyridine); and groups obtained by removing 1 to 4 hydrogen atoms from any of the aromatic heterocycles of condensed ring heteroaromatic hydrocarbon compounds, such as quinoline, quinoxaline, benzothiophene, benzothiazole, benzimidazole, benzoxazole, indole, carbazole, dibenzofuran, dibenzothiophene, acridine, and phenanthroline. The arylalkylene group includes a group formed by combining the above aromatic hydrocarbon group with an alkylene group having 1 to 3 carbon atoms. The divalent to tetravalent chain or cyclic hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably has 1 to 6 carbon atoms, and further preferably has 1 to 4 carbon atoms. The chain hydrocarbon group may be either linear or branched. Also, R 1 may be a group formed by combining two or more of the above-mentioned aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups. Furthermore, R 1 may be a group formed by combining one or more of the above aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups with a nitrogen atom. Examples of such groups include groups formed by removing 1 to 4 hydrogen atoms from trialkylamines such as trimethylamine or triphenylamine.

[0063] The aromatic hydrocarbon group, aromatic heterocyclic group, or arylalkylene group may have one or more monovalent substituents. Examples of the monovalent substituent include a fluorine atom; a haloalkyl group such as a fluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, or a cycloheptyl group; a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, or a methyloxy group. linear or branched alkoxy groups having 1 to 20 carbon atoms, such as a silyl group or an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms, such as a methylamino group, an ethylamino group, a dimethylamino group or a diethylamino group; a cyclic amino group, such as a pyrrolidino group, a piperidino group or a morpholino group; a diarylamino group, such as a diphenylamino group or a carbazolyl group; an acyl group, such as an acetyl group, a propionyl group or a butyryl group; an alkenyl group having 2 to 30 carbon atoms, such as a styryl group; a halogen atom, such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a cyclic amino group having 1 to 10 carbon atoms, such as ... an aryl group having 5 to 20 carbon atoms which may be substituted with a silyl group, an amino group, or the like (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group described above); a heterocyclic group containing one or more of a nitrogen atom, a sulfur atom, and an oxygen atom which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (the heterocyclic group may be one consisting of only one ring, or may be a compound in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded to each other at one carbon atom, or may be a condensed heterocyclic group. Specific examples of the heterocyclic group include Specific examples of aromatic heterocyclic groups include a thiophene ring, a furan ring, a pyrrole ring, a benzothiophene ring, a benzofuran ring, an indole ring, a dibenzothiophene ring, a dibenzofuran ring, a carbazole ring, a thiazole ring, a benzothiazole ring, an oxazole ring, a benzoxazole ring, an imidazole ring, a benzimidazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a benzothiadiazole ring, a phenanthridine ring, etc.); an ester group, a thioether group, etc.These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, or the like.

[0064] In the above general formula (2), n 1 is an integer of 1 to 4, preferably 2 or 3.

[0065] The compound represented by the above general formula (2) can be synthesized by using a halogen compound having iodine, bromine, chlorine, or fluorine and hexahydropyrimidopyrimidine as raw materials, through Ullmann coupling reaction, Buchwald-Hartwig amination reaction, nucleophilic substitution reaction, or the like.

[0066] X in the above general formula (3) 1 , X 2 are the same or different and represent a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have a substituent. Examples of the divalent linking group include divalent hydrocarbon groups and groups in which some of the carbon atoms of a hydrocarbon group have been substituted with a heteroatom such as a nitrogen atom, an oxygen atom or a sulfur atom. The hydrocarbon group preferably has 1 to 6 carbon atoms, and more preferably has 1, 2 or 6 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination thereof. The divalent hydrocarbon group may be an alkylene group, which is a saturated hydrocarbon group, or an unsaturated hydrocarbon group such as an alkenylene group or an alkynylene group.

[0067] In the above general formula (3), L represents a direct bond or a p-valent linking group. Note that L becomes a direct bond only when p is 2. Examples of the p-valent linking group include a nitrogen atom, an oxygen atom, a sulfur atom, a carbon atom, and also a group obtained by removing p hydrogen atoms from a hydrocarbon group or a group in which some of the carbon atoms of a hydrocarbon group have been substituted with a hetero atom such as a nitrogen atom, an oxygen atom, or a sulfur atom. When the p-valent linking group has a carbon atom, it preferably has 1 to 30 carbon atoms, and more preferably has 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination thereof. The hydrocarbon group may be any of a saturated hydrocarbon group, an unsaturated hydrocarbon group, and an aromatic hydrocarbon group. Examples of aromatic hydrocarbon groups include groups formed by removing a hydrogen atom from an aromatic compound such as a benzene ring, a naphthalene ring, an anthracene ring, a tetracene ring, a pentacene ring, a triphenylene ring, a pyrene ring, a fluorene ring, or an indene ring.

[0068] R in the above general formula (3) 2 ~R 4 are the same or different and each represents a monovalent substituent. 1 ~m 3 are the same or different and represent a number from 0 to 3. Examples of the monovalent substituent include a fluorine atom; a haloalkyl group such as a fluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, or a cycloheptyl group; a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, or a methyloxy group. linear or branched alkoxy groups having 1 to 20 carbon atoms, such as a silyl group or an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms, such as a methylamino group, an ethylamino group, a dimethylamino group or a diethylamino group; a cyclic amino group, such as a pyrrolidino group, a piperidino group or a morpholino group; a diarylamino group, such as a diphenylamino group or a carbazolyl group; an acyl group, such as an acetyl group, a propionyl group or a butyryl group; an alkenyl group having 2 to 30 carbon atoms, such as a styryl group; a halogen atom, such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a cyclic amino group having 1 to 10 carbon atoms, such as ... an aryl group having 5 to 20 carbon atoms which may be substituted with a silyl group, an amino group, or the like (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group described above); a heterocyclic group containing one or more of a nitrogen atom, a sulfur atom, and an oxygen atom which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (the heterocyclic group may be one consisting of only one ring, or may be a compound in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded to each other at one carbon atom, or may be a condensed heterocyclic group. Specific examples of the heterocyclic group include Specific examples of aromatic heterocyclic groups include a thiophene ring, a furan ring, a pyrrole ring, a benzothiophene ring, a benzofuran ring, an indole ring, a dibenzothiophene ring, a dibenzofuran ring, a carbazole ring, a thiazole ring, a benzothiazole ring, an oxazole ring, a benzoxazole ring, an imidazole ring, a benzimidazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a benzothiadiazole ring, a phenanthridine ring, etc.); an ester group, a thioether group, etc.These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, or the like.

[0069] In the above general formula (3), p represents a number of 1 to 4, and is preferably a number of 1 to 3. In addition, n in the above general formula (3) 2 represents the number 0 or 1, with 0 being preferred.

[0070] The average thickness of the electron injection layer 7 is preferably 0.5 to 100 nm, and more preferably 1 to 10 nm. The electron injection layer 7 can be formed by applying a coating composition or by co-deposition using a vacuum deposition method. The average thickness of the electron injection layer 7 can be measured by, for example, a stylus step gauge or spectroscopic ellipsometry.

[0071] "cathode" Examples of materials used for the cathode 8 include ITO, IZO, Au, Pt, Ag, Cu, Al, and alloys containing these. Among these, it is preferable to use ITO, IZO, Au, Ag, or Al as the material for the cathode 8. The average thickness of the cathode 8 is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 30 to 150 nm. Even when an opaque material is used as the material for the cathode 8, by setting the average thickness to, for example, about 10 to 30 nm, it can be used as a transparent cathode in a top-emission organic EL element. The average thickness of the cathode 8 can be measured by a quartz crystal film thickness meter during the deposition of the cathode 8.

[0072] In particular, in the organic EL element having an inverted structure shown in FIG. 5, the layer made of an inorganic oxide formed on the cathode 8 is also treated as a part of the cathode. The oxide used in this case is a semiconductor or insulator laminated thin film layer. Specifically, it may be any of a layer made of a single metal oxide, a layer made of a mixture of two or more metal oxides and a layer made of a single metal oxide, or a layer made of a mixture of two or more metal oxides.

[0073] Metal elements constituting metal oxides that form inorganic oxides include magnesium, calcium, strontium, barium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, indium, gallium, iron, cobalt, nickel, copper, zinc, cadmium, aluminum, and silicon.

[0074] When the layer made of an inorganic oxide includes a layer containing a mixture of two or more kinds of metal oxides, it is preferable that at least one of the metal elements constituting the metal oxide is a layer made of magnesium, aluminum, calcium, zirconium, hafnium, silicon, titanium, or zinc. When the layer made of an inorganic oxide is a layer made of a simple metal oxide, it is preferable that the layer is made of a metal oxide selected from the group consisting of magnesium oxide, aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide, titanium oxide, and zinc oxide.

[0075] When the layer made of an inorganic oxide is a layer obtained by laminating either or both of a layer made of a mixture of two or more kinds of metal oxides and a layer made of a single metal oxide, or a layer obtained by mixing two or more kinds of metal oxides, examples of the layer made of an inorganic oxide include a layer made of a mixture of two kinds of metal oxides selected from titanium oxide / zinc oxide, titanium oxide / magnesium oxide, titanium oxide / zirconium oxide, titanium oxide / aluminum oxide, titanium oxide / hafnium oxide, titanium oxide / silicon oxide, zinc oxide / magnesium oxide, zinc oxide / zirconium oxide, zinc oxide / hafnium oxide, zinc oxide / silicon oxide, and calcium oxide / aluminum oxide, a layer made of a mixture of three kinds of metal oxides selected from titanium oxide / zinc oxide / magnesium oxide, titanium oxide / zinc oxide / zirconium oxide, titanium oxide / zinc oxide / aluminum oxide, titanium oxide / zinc oxide / hafnium oxide, titanium oxide / zinc oxide / silicon oxide, and indium oxide / gallium oxide / zinc oxide.

[0076] The inorganic oxides are IGZO (indium gallium zinc oxide), an oxide semiconductor that exhibits good properties as a special composition, and / or 12CaO 7Al 2 O 3 It may include. When an inorganic oxide film is formed, the average thickness is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 2 to 100 nm. The average thickness of the layer made of an inorganic oxide can be measured by a stylus step gauge or spectroscopic ellipsometry.

[0077] "Sealing" The organic EL element 1 may be sealed, if necessary. For example, the organic EL element 1 may be sealed by a sealing container (not shown) having a concave space for accommodating the organic EL element 1, and an adhesive for bonding the edge of the sealing container to the substrate 2. Alternatively, the organic EL element 1 may be accommodated in a sealing container and sealed by filling it with a sealant made of an ultraviolet (UV) curable resin or the like.

[0078] When the organic EL element 1 is sealed using a sealing container or a sealing member, a desiccant that absorbs moisture may be placed inside the sealing container or the sealing member. A material that absorbs moisture may be used as the sealing container or the sealing member. A space may be formed inside the sealed sealing container or the sealing member.

[0079] Resin materials, glass materials, etc. can be used as the material of the sealing container or sealing member used to seal the organic EL element 1. Examples of the resin materials and glass materials used for the sealing container or sealing member include the same materials as those used for the substrate 2.

[0080] "Manufacturing method for organic EL elements" Next, a method for producing the organic EL element 1 will be described as an example of a method for producing the organic EL element of the present invention.

[0081] To manufacture the organic EL element 1, first, the anode 3 is formed on the substrate 2. The anode 3 can be formed by a sputtering method, a vacuum deposition method, a sol-gel method, a spray pyrolysis (SPD) method, an atomic layer deposition (ALD) method, a vapor phase deposition method, a liquid phase deposition method, etc. The anode 3 may be formed by bonding a metal foil.

[0082] Next, on the anode 3, a hole injection layer 4, a hole transport layer 5, a light emitting layer 6, and an electron injection layer 7 are formed in this order. The methods for forming the hole injection layer 4, the hole transport layer 5, the light emitting layer 6, and the electron injection layer 7 are not particularly limited, and various conventionally known formation methods can be used appropriately in accordance with the properties of the materials used for the hole injection layer 4, the hole transport layer 5, the light emitting layer 6, and the electron injection layer 7, respectively. Specifically, methods for forming the hole injection layer 4, the hole transport layer 5, the light emitting layer 6, and the electron injection layer 7 include a coating method in which an organic compound solution containing an organic compound that will become the hole injection layer 4, the hole transport layer 5, the light emitting layer 6, and the electron injection layer 7 is applied, a vacuum deposition method, an ESDUS (Evaporative Spray Deposition from Ultra-dilute Solution) method, and the like.

[0083] Next, the cathode 8 is formed on the electron injection layer 7. The cathode 8 can be formed in the same manner as the anode 3, for example.

[0084] The order is reversed when fabricating an organic EL element having an inverted structure as shown in Fig. 5. When forming a layer made of an inorganic oxide on the cathode 8 in the organic EL element having an inverted structure as shown in Fig. 5, the oxide is formed by using a method such as a spray pyrolysis method, a sol-gel method, a sputtering method, or a vacuum deposition method. Through the above steps, the organic EL element 1 is obtained.

[0085] "Sealing method" When sealing the organic EL element 1, it can be sealed by using a method commonly used for sealing an organic EL element.

[0086] <Display device, lighting device> The organic EL device 1 of the present embodiment emits light using the anthracene derivative represented by the above general formula (1) which has high luminous efficiency, and preferably emits light using an exciplex formed between the anthracene derivative having high electron affinity and another organic material having low ionization potential, so that recombination of charges can be achieved with small energy, resulting in an organic EL device 1 with low driving voltage.

[0087] The organic EL element of the present invention can change the emission color by appropriately selecting the materials for the light-emitting layer, etc., and can also obtain a desired emission color by using a color filter, etc. Therefore, the organic EL element of the present invention can be suitably used as a light-emitting portion of a display device or a lighting device.

[0088] The display device of the present invention is excellent in productivity due to its simple element structure, and includes the organic EL element of the present invention, which has a low driving voltage, and is therefore preferable as a display device. Furthermore, the lighting device of the present invention has excellent productivity due to its simple element structure and is equipped with the organic EL element of the present invention, which has a low driving voltage, and is therefore preferable as a lighting device. EXAMPLES

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0090] <Synthesis of anthracene derivatives> According to the following reaction scheme, an anthracene derivative represented by formula (1-1) was synthesized. [ka]

[0091] "Synthesis process of the compound represented by formula (4-3)" In an argon atmosphere, 5-bromoisophthalic acid (10.4 g, 42.4 mmol, 1.0 eq.) represented by formula (4-1) and anhydrous dichloromethane (100 mL) were added to a 300 mL reactor, and oxalyl chloride (10.9 mL, 12.7 mmol, 3.0 eq.) and DMF (3 drops) were added to the suspension. The suspension was stirred at room temperature for 18 hours until the foaming subsided, and then concentrated. Toluene (100 mL x 2) was added to the residue and concentrated again to obtain the compound represented by formula (4-2) (12.4 g, excess), which is a pale yellow viscous liquid. THF (100 mL), iPr 2 NEt (17.8mL, 127mmol, 3.0eq.) was added and cooled on ice. At an internal temperature of 5°C, t-butylamine (11.2mL, 106mmol, 2.5eq.) was added dropwise over 15 minutes, and the mixture was allowed to warm to room temperature over 3 hours while the cooling bath was still attached. The suspension was quenched with 0.5N aqueous hydrochloric acid (100mL), extracted with ethyl acetate (100mL x 2), and the organic layers were combined and washed with saturated aqueous sodium bicarbonate and saturated saline, dried over anhydrous sodium sulfate, and concentrated to obtain the compound represented by formula (4-3) (14.5g, 40.8mmol, 96%) as a colorless solid.

[0092] "Synthesis process of the compound represented by formula (4-4)" In an argon atmosphere, a compound represented by formula (4-3) (14.5 g, 6.41 mmol, 1.0 eq.) and thionyl chloride (64 mL, 883 mmol, 21 eq.) were added to a 300 mL reactor, the bath temperature was raised to 85 ° C., and the mixture was heated under reflux at the same temperature for 3 days. This was concentrated, and toluene (100 mL × 2) was added to the residue to cause azeotropy. Heptane (60 mL) was added to this light brown solid, heated to 70 ° C., dispersed and washed, cooled, and filtered. THF (20 mL) was added to the filtered product, and after complete dissolution at 70 ° C., IPE (20 mL) was slowly added to precipitate the solid, which was then cooled, filtered, and dried at 40 ° C. under high vacuum to obtain a colorless solid compound represented by formula (4-4) (7.0 g, 33.8 mmol, 82%).

[0093] "Synthesis process 1 of the compound represented by formula (4-5)" In an argon atmosphere, a 100 mL reactor was charged with the compound represented by formula (4-4) (1.0 g, 4.83 mmol, 1.0 eq.), bis-pinacoldiborane (1.84 g, 7.24 mmol, 1.5 eq.), and Pd(dppf)Cl. 2 (40 mg, 0.0483 mmol, 0.01 eq.), potassium acetate (1.04 g, 10.6 mmol, 2.2 eq.), and degassed isopropyl acetate (25 mL) were added, and the mixture was heated and stirred at a bath temperature of 90°C for 6 hours. After cooling, the black-brown suspension was filtered through Celite, the filter bed was washed with ethyl acetate, and the filtrate was concentrated to obtain a black-brown solid (2.69 g). This was purified by column purification (SiO 2 = 65 g, hexane / ethyl acetate = 2 / 1 → 1 / 1) to obtain a viscous solid (1.11 g). This was washed by heating and dispersion with IPE (ca. 8 mL), cooled, and the precipitated solid was filtered, the filter bed was washed with heptane, and dried at 50 ° C under high vacuum to obtain the compound represented by formula (4-5) (0.79 g, 3.11 mmol, 64%) as a colorless solid.

[0094] "Synthesis process 2 of the compound represented by formula (4-5)" In an argon atmosphere, a 300 mL reactor was charged with the compound represented by formula (4-4) (3.6 g, 17.4 mmol, 1.0 eq.), bis-pinacoldiborane (6.62 g, 26.1 mmol, 1.5 eq.), and Pd(dppf)Cl.2 (142 mg, 0.174 mmol, 0.01 eq.), potassium acetate (3.75 g, 38.2 mmol, 2.2 eq.), and degassed isopropyl acetate (90 mL) were added, and the mixture was heated and stirred at a bath temperature of 90°C for 8 hours. After cooling, the black-brown suspension was filtered through Celite, the filter bed was washed with ethyl acetate, and the filtrate was concentrated to obtain a black-brown solid (9.61 g). This was purified by column purification (SiO 2 = 150 g, hexane / ethyl acetate = 2 / 1 → 1 / 1) to obtain a viscous solid (4.86 g). This was washed by heating and dispersion with IPE (ca. 30 mL), cooled, and the precipitated solid was filtered, the filter bed was washed with heptane, and dried at 50 ° C under high vacuum to obtain the compound represented by formula (4-5) (3.22 g, 12.6 mmol, 72%) as a colorless solid. The compounds obtained in the above "Synthesis process 1 of the compound represented by formula (4-5)" and "Synthesis process 2 of the compound represented by formula (4-5)" were mixed and used in the following "Synthesis process of the anthracene derivative represented by formula (1-1)".

[0095] "Synthesis process of the compound represented by formula (5-2)" In an argon atmosphere, 2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine (2.3 g, 5.92 mmol, 1.0 eq.) represented by formula (5-1), 9-anthraceneboronic acid (1.58 g, 7.11 mmol, 1.2 eq.), Pd(Ph 3 P) 4 (0.205g, 0.178mmol, 0.03eq.), sodium carbonate (1.88g, 17.8mmol, 3.0eq.), degassed toluene (40mL), degassed distilled water (20mL), and degassed ethanol (10mL) were added. The bath temperature of this suspension was raised to 95°C, and it was heated and stirred for 10 hours. After cooling, heptane (40mL) was added to this brown suspension and stirred, and the insoluble matter was filtered, and the filter bed was washed with city water and methanol, and dried at 60°C under high vacuum to obtain a gray powder (3.24g). This was dispersed and washed with heated ethanol, filtered, washed with methanol, and dried at 60°C under high vacuum to obtain a compound represented by formula (5-2) (2.98g, 6.14mmol, 86%, poor purity) which is a yellow-green solid.

[0096] "Synthesis process of the compound represented by formula (5-3)" A 300 mL reactor was charged with the compound represented by formula (5-2) (2.95 g, 6.08 mmol, 1.0 eq.), NBS (1.3 g, 7.30 mmol, 1.2 eq.), and chloroform (300 mL). The suspension was heated and stirred at a bath temperature of 65° C. for 8 hours. The suspension was concentrated, and methanol / distilled water = 2 / 1 (60 mL) was added to the residue, ultrasonically cleaned, filtered, and the filtered solid was dispersed and washed again with methanol, filtered, and dried at 80° C. under high vacuum to obtain a yellowish brown solid, the compound represented by formula (5-3) (3.46 g, 6.12 mmol, excess).

[0097] "Synthesis process of anthracene derivative represented by formula (1-1)" In a 200 mL reactor, the compound represented by formula (5-3) (1.7 g, 3.01 mmol, 1.0 eq.), the compound represented by formula (4-5) (0.79 g, 3.11 mmol, 1.04 eq.), potassium phosphate tripotassium (1.92 g, 9.03 mmol, 3.0 eq.), and degassed toluene (28 mL) were added. The suspension was degassed under reduced pressure, and then Pd 2 (dba) 3(34mg, 0.151mmol, 0.05eq.), S-Phos (0.148g, 0.361mmol, 0.12eq.) were added and degassed again under reduced pressure. This suspension was heated and stirred at a bath temperature of 110°C for 18 hours. This suspension was added to toluene (2L), stirred at 110°C for 1 hour, cooled to about 60°C, and insoluble matter was filtered. The filter bed was added to chloroform (1.5L), heated to 60°C, Galleon Earth VR-2 (15g) was added to this suspension, stirred, filtered through Celite, and the filtrate was concentrated to obtain a beige solid (0.55g). The filtered toluene solution was heated again, Galleon Earth VR-2 (15g) was added, stirred, and filtered through Celite. The filtrate was concentrated to obtain a beige powder (0.92g). The obtained solids were combined and dispersed and washed in heated THF and ethyl acetate in that order. This was dried under high vacuum at 80° C. to obtain a beige solid anthracene derivative represented by formula (1-1) (1.25 g, 2.04 mmol, 67%). 1 The H-NMR spectrum is shown in Figure 7.

[0098] "Example 1" (Fabrication of organic EL elements) Organic EL device 1 was produced and evaluated by the following method.

[0099] [Process 1] As the substrate 2, a commercially available transparent glass substrate having an average thickness of 0.7 mm and having an electrode (anode 3) patterned with ITO to a width of 3 mm was prepared. The substrate 2 having the anode 3 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. Thereafter, the substrate 2 having the anode 3 was taken out of the isopropanol, dried by nitrogen blowing, and subjected to UV ozone cleaning for 20 minutes.

[0100] [Process 2] The substrate 2 on which the anode 3 that was cleaned in [Step 1] was formed was set on a spin coater, and a hole injection material "Clevios HIL1.3N" manufactured by Heraeus was spin-coated as a hole injection layer 4, followed by a heat treatment in the atmosphere to form a hole injection layer 4 of 10 nm.

[0101] [Process 3] Next, the substrate 2 on which each layer up to the hole injection layer 4 had been formed was fixed to a substrate holder of a vacuum deposition apparatus. -5 The pressure was reduced to 100 Pa. First, a hole transport layer 5 having the following structural formula: [ka] 2-SF-PHX (calculated ionization energy = 4.55 eV) represented by the formula (1-1) and NDP-9, a p-type dopant from Novaled, were evaporated to a thickness of 30 nm in a mass ratio of 9:1, and then 2-SF-PHX was evaporated to a thickness of 10 nm. Furthermore, a film was formed as the light-emitting layer 6 by evaporating an anthracene derivative (calculated electron affinity = 2.14 eV, calculated ionization energy = 5.67 eV) represented by the formula (1-1) to a thickness of 30 nm.

[0102] After the light-emitting layer 6 was formed, a compound represented by the following structural formula (2-1) was deposited to a thickness of 3 nm as the electron-injection layer . [ka] The compound represented by the above structural formula (2-1) was synthesized according to the method described in T. Sasaki, M. Hasegawa, K. Inagaki, H. Ito, K. Suzuki, T. Oono, K. Morii, T. Shimizu and H. Fukagawa, Nature Communications, 12, pp. 2706.1, DOI: 10.1038 / s41467-021-23067-2.

[0103] Next, a cathode 8 made of aluminum and having a thickness of 100 nm was formed by vacuum deposition on the substrate 2 on which the electron injection layer 7 had been formed. The cathode 8 was formed using a stainless steel deposition mask so that the deposition surface would be in the shape of a strip with a width of 3 mm, and the light-emitting area of ​​the fabricated organic EL element was 9 mm 2 It was decided.

[0104] [Step 4] Next, the substrate 2 on which each layer up to the cathode 8 was formed was placed in a glass cap (sealing container) having a concave space, and sealed by filling it with a sealant made of an ultraviolet (UV) curable resin, thereby obtaining the organic EL element of Example 1.

[0105] "Comparative Example 1" An organic EL device of Comparative Example 1 was prepared in the same manner as in Example 1, except that the material used for the light-emitting layer 6 was a compound represented by the following structural formula (6-1) (described in Non-Patent Document 1), which contains benzonitrile and thus has a larger electron affinity than simple aromatic anthracene derivatives such as 9-(1-naphthyl)-10-(2-naphthyl)anthracene. [ka]

[0106] (Evaluation of organic EL element characteristics) Voltage was applied to the thus obtained elements of the examples and comparative examples using a Keithley 2400 source meter, and the luminance was measured using a Konica Minolta LS-100 to examine the relationship between the applied voltage and the luminance. The relationship between the applied voltage and the current density, and the emission spectrum were also examined. These results are shown in FIG. 8.

[0107] FIG. 8(a) shows the applied voltage-current density characteristics of Example 1 and Comparative Example 1. A current rise was observed at a lower applied voltage in Example 1 than in Comparative Example 1. This is because the electron affinity of the material used in the light-emitting layer 6 is greater in the anthracene derivative represented by structural formula (1-1) than in the compound represented by structural formula (6-1).

[0108] 8(b) and (c) show the applied voltage-luminance characteristics and EL spectra of Example 1 and Comparative Example 1. 8(b) and (c), in Example 1, blue light emission is obtained at a lower applied voltage than in Comparative Example 1. In particular, in Example 1, blue light emission is obtained even though the current starts to rise at an applied voltage of 2 V or less. As shown in FIGS. 2 and 3, it is considered that an exciplex is formed at a low applied voltage due to the large electron affinity of the anthracene derivative represented by structural formula (1-1), and the energy of the exciplex can be extracted as blue light emission via triplet-triplet annihilation. [Industrial Applicability]

[0109] The anthracene derivative of the present invention can be used to form a light-emitting device such as an organic EL device. [Explanation of symbols]

[0110] 1: organic EL element, 2: substrate, 3: anode, 4: hole injection layer, 5: hole transport layer, 6: light emitting layer, 7: electron injection layer, 8: cathode

Claims

1. The following general formula (1): 【Chemistry 1】 [In general formula (1), X's are each independently hydrogen or a monovalent substituent selected from the group consisting of a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may be joined together to form a ring, with the proviso that at least two of X's are cyano groups, R are each independently hydrogen or a monovalent substituent selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may be joined together to form a ring.

2. An organic electroluminescence element comprising an anode, a light-emitting layer, and a cathode in this order, An organic electroluminescence device, wherein the light-emitting layer comprises the anthracene derivative according to claim 1 .

3. The organic electroluminescence device according to claim 2 , wherein the light-emitting layer further contains a material having a smaller ionization energy than the anthracene derivative.

4. A hole transport layer is further provided between the anode and the light emitting layer, The organic electroluminescence device according to claim 2 , wherein the hole transport layer contains a material having a smaller ionization energy than the anthracene derivative.

5. A display device comprising the organic electroluminescence element according to claim 2.

6. A lighting device comprising the organic electroluminescence element according to claim 2.

Images