Mixed material for organic electroluminescent element and organic electroluminescent element

Abstract

The present invention makes it possible to achieve a practical organic EL element that can be driven at a low voltage but has high light-emission efficiency and a long life.　According to the present invention, a material for an organic electroluminescent element is a compound represented by any of general formulas (1a)–(1f), the material being characterized in that the average deuteration rate of the hydrogen in the compound is at least 20%. X represents O or S, and A and E each represent general formulas (2a)–(2e) and are different from each other. * indicates the site of bonding to general formulas (1a)–(1f), and R1–R7 each independently represent hydrogen, deuterium, or the like. However, R2–R7 do not include carbazole.

Description

Mixed material for organic electroluminescent device and organic electroluminescent device

[0001] The present invention relates to an organic electroluminescent device (referred to as an organic EL device) capable of converting electrical energy into light, and a material for the organic electroluminescent device used therein.

[0002] When a voltage is applied to an organic EL element, holes are injected from the anode and electrons are injected from the cathode into the light-emitting layer. The injected holes and electrons then recombine in the light-emitting layer, generating excitons. At this time, due to the statistical laws of electron spin, singlet excitons and triplet excitons are generated in a ratio of 1:3. It is said that the internal quantum efficiency of fluorescent organic EL elements that use emission from singlet excitons is limited to 25%. On the other hand, it is known that the internal quantum efficiency of phosphorescent organic EL elements that use emission from triplet excitons can be increased to 100% if intersystem crossing from singlet excitons is efficiently performed.

[0003] In recent years, technology for extending the lifetime of phosphorescent organic EL elements has progressed, and they are beginning to be applied to displays of mobile phones, etc. However, with regard to blue organic EL elements, no practical phosphorescent organic EL elements have been developed, and there is a demand for the development of blue organic EL elements that are highly efficient and have a long lifetime.

[0004] More recently, highly efficient delayed fluorescence organic EL elements utilizing delayed fluorescence have been developed. For example, Patent Document 1 discloses an organic EL element utilizing the TTF (Triplet-Triplet Fusion) mechanism, which is one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon in which singlet excitons are generated by the collision of two triplet excitons, and is thought to theoretically increase the internal quantum efficiency to 40%. However, since the efficiency is lower than that of phosphorescent organic EL elements, further improvement in efficiency is required.

[0005] On the other hand, Patent Document 2 discloses an organic EL device that utilizes the thermally activated delayed fluorescence (TADF) mechanism. The TADF mechanism utilizes the phenomenon of reverse intersystem crossing from triplet excitons to singlet excitons in a material with a small energy difference between the singlet and triplet levels, and is thought to theoretically increase the internal quantum efficiency to 100%.

[0006] Here, Non-Patent Document 1 discloses a device using a predetermined mixed host (SiTrz2Cz and SiCzCz) in addition to a predetermined phosphorescent dopant, TADF dopant.

[0007] Furthermore, Patent Documents 3 to 5 disclose elements using compounds in which multiple non-deuterated carbazoles are linked together.

[0008] WO2010 / 134350 publication WO2011 / 070963 publication WO2012 / 077520 publication WO2022 / 45272 publication WO2021 / 200252 publication

[0009] Kim et al., Sci. Adv. 8, eabq1641 (2022)

[0010] In order to apply organic EL elements as display elements or light sources for flat panel displays and the like, it is necessary to improve the luminous efficiency of the elements and at the same time ensure sufficient stability during operation. However, these cannot be achieved with materials consisting of combinations of conventionally known compounds.

[0011] The present invention has been made in view of the above-mentioned circumstances, and aims to provide a material for organic electroluminescence devices that can provide practically useful organic EL devices that emit light with high efficiency and have long life characteristics while being driven at a low voltage. Another aim of the present invention is to provide an organic EL device using such a material.

[0012] That is, the present invention provides a material for an organic electroluminescent element, which is a compound represented by the following general formulas (1a) to (1f), characterized in that the average deuteration rate of hydrogen in the compound is 20% or more. Here, the following general formula is preferably (1a), (1b), (1c), or (1d), with (1a) being more preferred. In (1e), E is bonded to the meta position of the biphenyl group. This has the effect of increasing the triplet excitation energy of E as a partial skeleton and localizing the triplet excitation energy in the entire general formula (1e). The average deuteration rate is preferably 50% or more, more preferably 70% or more, and even more preferably 80% or more. Here, X represents O or S, preferably O. A and E are each independently represented by the following general formulas (2a) to (2e), and A and E are different from each other. However, A or E is represented by (2e) only in the case of the general formula (1c) or (1d). Here, A and E are preferably (2a), (2b) or (2c), and more preferably A or E is (2c). * indicates the bonding position with the general formulae (1a) to (1f). １ ~R ７ each independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups, provided that R ２ ~R ７ does not contain carbazole.

[0013] The average deuteration rate of A or E is preferably 80% or more, and the average deuteration rate of each of A and E is more preferably 80% or more.

[0014] Furthermore, in a preferred embodiment of the general formulas (1a) to (1f), A and E are (2b) or (2c), and the average deuteration rate of each of A and E is 70% or more.

[0015] Furthermore, when the triplet excitation energy of A as a partial skeleton of the material for organic electroluminescent elements represented by the general formulas (1a) to (1f) is represented as T1(A) and the triplet excitation energy of E as a partial skeleton is represented as T1(E), |T1(A)-T1(E)| is preferably 0.02 eV or more, more preferably 0.05 eV or more, and even more preferably 0.1 eV or more.

[0016] The calculation method for T1(A) and T1(E) will be described. For example, when the compound represented by the general formula (1a) is (1a-1) below, if A is (2a-1) and E is (2b-1), since the hydrogen atom has little electronic interaction with surrounding atoms, T1(A) can be expressed as the triplet excitation energy of a compound in which (2a-1) is bonded to hydrogen with an *, such as (2a-2). Similarly, T1(E) can be expressed as the triplet excitation energy of (2b-2). When evaluating the energy levels of the partial skeletons of A and E, T1(A) of (2a-1) and T1(E) of (2b-1) can be calculated by evaluating the energy levels of (2a-2) and (2b-2), respectively. T1(A) calculated by this method is 3.1367 eV, and T1(E) is 3.1644 eV. In this case, |T1(A)-T1(E)| is 0.0277, which is greater than 0.02 eV. In order for a blue organic EL device to emit light with high efficiency, the compound used as the host in the light-emitting layer and the compound used in the layer adjacent to the light-emitting layer must have a high triplet excited state energy (T1(h)). On the other hand, compounds with a high T1(h) are relatively prone to degradation, such as decomposition and alteration, which shortens the device's lifespan. To solve this problem, the present invention provides a compound containing a partial skeleton with a high T1 and a partial skeleton with a low T1, and by making |T1(A) - T1(E)| 0.02 eV or greater, it is possible to realize an organic EL device that emits blue light with high efficiency and a long lifespan.

[0017] As shown in the calculation method of |T1(A) - T1(E)| for the (1a-1) compound represented by general formula (1a) of the present invention, T1(A) has a lower T1 than T1(E), and therefore, when a triplet excited state of the (1a-1) compound occurs in a device, the triplet excited state is localized on the partial skeleton [(2a-1)] of A. In a compound in which T1 is localized, the spatial proportion of the triplet excited state in the light-emitting layer and layers adjacent to the light-emitting layer is reduced during device operation, compared to a compound in which T1 is delocalized. Because the triplet excited state is the starting point for degradation and alteration reactions between two molecules, a reduction in the spatial proportion of the triplet excited state suppresses the degradation and alteration of the compound, thereby extending the device's lifespan. That is, the compound (1a-1) in which the triplet excited state is localized extends the life of the organic EL device compared to the compounds (A1) and (A2) below in which the triplet excited state is not localized, i.e., T1 is not localized. Furthermore, a compound in which the triplet excited state is delocalized can provide an effect of extending the life of the device more than a compound in which the triplet excited state is localized by replacing hydrogen in the compound, particularly hydrogen in the partial skeleton where T1 is localized, with deuterium. That is, taking the above compound (1a-1) represented by general formula (1a) of the present invention as an example, it is preferable that the average deuteration ratio of (2a-1) or (2b-1) is 80% or more, it is more preferable that the average deuteration ratio of (2a-1) and (2b-1) is 80% or more, and it is even more preferable that the average deuteration ratio of (2a-1) with a low T1 is 85% or more.

[0018] The material for organic electroluminescent elements of the present invention is preferably a mixed material for organic electroluminescent elements, characterized by containing a compound represented by any one of the general formulas (1a) to (1f) and a cyclic azine compound represented by the following general formula (10). More preferably, it is a premixed material for organic electroluminescent elements comprising a compound represented by any one of the general formulas (1a) to (1f) and a cyclic azine compound represented by the following general formula (10). Here, Ar ２ and Ar ３each independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups. １ represents a single bond or a substituted or unsubstituted phenyl group, preferably a single bond. Some or all of the hydrogen atoms in the compound represented by the general formula (10) may be substituted with deuterium atoms.

[0019] The present invention also relates to an organic electroluminescent device comprising one or more organic layers between opposing anode and cathode electrodes, wherein at least one of the organic layers contains a material for organic electroluminescent devices represented by any one of the general formulas (1a) to (1f). Preferably, the organic layer contains a mixed material for organic electroluminescent devices comprising a compound represented by any one of the general formulas (1a) to (1f) and a cyclic azine compound represented by the general formula (10). More preferably, the organic layer contains a premixed material for organic electroluminescent devices comprising a compound represented by any one of the general formulas (1a) to (1f) and a cyclic azine compound represented by the general formula (10). Note that the compound represented by any one of the general formulas (1a) to (1f) and the cyclic azine compound represented by the general formula (10) may be supplied to the organic layer individually, or may be supplied as a premixed material for organic electroluminescent devices.

[0020] In the organic electroluminescent device of the present invention, it is preferable that the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and that the emitting layer contains a thermally activated delayed fluorescent material, and it is more preferable that the thermally activated delayed fluorescent material contains a boron atom.

[0021] In the organic electroluminescent device of the present invention, it is preferable that the organic layer containing the mixed material for an organic electroluminescent device is an emitting layer, and that the emitting layer contains a phosphorescent material, and it is more preferable that the phosphorescent material contains platinum atoms.

[0022] Furthermore, in the organic electroluminescent device of the present invention, it is preferable that the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and that the emitting layer further contains a thermally activated delayed fluorescent material containing a boron atom and a phosphorescent material containing a platinum atom.

[0023] In addition, in the organic electroluminescent device of the present invention, it is preferable that the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and the emitting layer contains the mixed material for organic electroluminescent devices as a host material, and further contains a thermally activated delayed fluorescent material containing a boron atom and a phosphorescent material containing a platinum atom.

[0024] Furthermore, the present invention provides a method for producing an organic electroluminescent element having one or more organic layers between an anode and a cathode facing each other, wherein at least one of the organic layers is an emitting layer, and the emitting layer is formed by depositing, from a single deposition source, a premixed material for an organic electroluminescent element, in which a compound represented by any one of general formulas (1a) to (1f) of the present invention and a compound represented by general formula (10) are mixed in advance.

[0025] According to the present invention, it is possible to obtain a practically useful organic EL element that emits light with high efficiency and has a long life, while being driven at a low voltage.

[0026] FIG. 1 is a cross-sectional view showing an example of the structure of an organic EL element used in the present invention.

[0027] The compounds represented by the general formulae (1a) to (1f) and the compound represented by the general formula (10) of the present invention will be described in detail below.

[0028] First, the general formulas (1a) to (1f) are as described above, and R １ ~R ７each independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. Preferably, they represent hydrogen, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. More preferably, they represent hydrogen, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups. However, R １ ~R ７ does not contain carbazole. The average deuteration ratio of all hydrogen atoms in the compounds represented by the general formulas (1a) to (1f) is 20% or more, preferably 50% or more, more preferably 70% or more, and even more preferably 80% or more. Furthermore, it is preferable that the compounds represented by the general formulas (1a) to (1f) contain at least one deuterated carbazolyl group represented by any of the general formulas (2a) to (2e). Regarding the average deuteration ratio in the present invention, for example, in the case of a compound represented by the general formula (1a), it includes both a single compound and a mixture of two or more compounds represented by the general formula (1a). Specifically, an average deuteration ratio of 50% means that on average, half of all hydrogen atoms are substituted with deuterium, and the compound may be composed of either a single compound or a mixture of compounds with different deuteration ratios.

[0029] The average deuteration ratio can be determined by mass spectrometry or proton nuclear magnetic resonance spectroscopy. For example, when determining by proton nuclear magnetic resonance spectroscopy, a measurement sample is first prepared by adding and dissolving the compound and an internal standard in a deuterated solvent, and the proton concentration [mol / g] of the compound contained in the measurement sample is calculated from the ratio of the integrated intensities derived from the internal standard and the compound. Next, the ratio of the proton concentration of the deuterated compound to the proton concentration of the corresponding non-deuterated compound is calculated, and the ratio is subtracted from 1 to calculate the average deuteration ratio of the deuterated compound. The average deuteration ratio of a substructure can also be calculated from the integrated intensities of the chemical shifts derived from the target substructure using the same procedure as described above.

[0030] A and E are each independently represented by the general formulae (2a) to (2e), and A and E are different from each other. However, A or E is represented by (2e) only when it is represented by the general formula (1c) or (1d). Note that * indicates the bonding position with the general formulae (1a) to (1f). Here, A and E are preferably (2a), (2b), or (2c), and more preferably A or E is (2c). Furthermore, the average deuteration rate of A or E is preferably 80% or more, and more preferably the average deuteration rate of each of A and E is 80% or more.

[0031] The R １ ~R ７ Specific examples of when is an unsubstituted aliphatic hydrocarbon group having 1 to 10 carbon atoms include methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, and decyl. Preferred are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl. Preferred are methyl, butyl, and octyl.

[0032] In addition, the R １ ~R ７Specific examples of when is an unsubstituted triarylsilyl group having 18 to 36 carbon atoms include triphenylsilyl, biphenyldiphenylsilyl, bisbiphenylphenylsilyl, and trisbiphenylsilyl. Preferred are triphenylsilyl, biphenyldiphenylsilyl, and bisbiphenylphenylsilyl. More preferred are triphenylsilyl and biphenyldiphenylsilyl.

[0033] The R １ ~R ７Specific examples of the linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, Examples of groups derived from triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. Preferably, it is a group derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. ２ ~R ７ does not contain carbazole.

[0034] The cyclic azine compound represented by the general formula (10) is as described above, but Ar ２ and Ar ３each independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. Preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. More preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups. Furthermore, L １ represents a single bond or a substituted or unsubstituted phenyl group, preferably a single bond. Note that some or all of the hydrogen atoms in the compound represented by general formula (10) may be substituted with deuterium atoms.

[0035] The Ar ２ and Ar ３ is an unsubstituted aliphatic hydrocarbon group having 1 to 10 carbon atoms, the R １ ~R ７ is the same as the specific example when is an unsubstituted aliphatic hydrocarbon group having 1 to 10 carbon atoms.

[0036] In addition, the Ar ２ and Ar ３ Specific examples of when R is an unsubstituted triarylsilyl group having 18 to 36 carbon atoms include the above-mentioned R １ ~R ７ is the same as the specific example when is an unsubstituted triarylsilyl group having 18 to 36 carbon atoms.

[0037] Furthermore, the Ar ２ and Ar ３is an unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, an unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups, specific examples thereof include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazoline, Examples of groups derived from benzoyl, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. Preferred are groups derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole.

[0038] In this specification, unsubstituted aromatic hydrocarbon groups, aromatic heterocyclic groups, and linking aromatic groups may each have a substituent. When substituted, the substituent is preferably deuterium, halogen, a cyano group, an alkyl group having 1 to 10 carbon atoms, a triarylsilyl group having 9 to 30 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms. The number of substituents is preferably 0 to 5, and more preferably 0 to 2. When an aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group has a substituent, the number of carbon atoms in the substituent is not included in the calculation of the carbon number. However, it is preferable that the total number of carbon atoms, including the number of carbon atoms in the substituent, satisfies the above range.

[0039] Specific examples of the substituent include deuterium, cyano, bromo, fluorine, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, triphenylsilyl, biphenyldiphenylsilyl, bisbiphenylphenylsilyl, trisbiphenylsilyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, etc. Preferred are deuterium, cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, and pentoxy.

[0040] In this specification, a linking aromatic group refers to an aromatic group in which the aromatic rings of two or more aromatic groups are linked by a single bond. These linking aromatic groups may be linear or branched. The linking position when benzene rings are linked may be ortho, meta, or para. The aromatic group may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and the multiple aromatic groups may be the same or different.

[0041] The mixed material for organic electroluminescent elements in the present invention may be in the form of a powder, solid, or thin film, so long as it contains the compound represented by any one of the general formulas (1a) to (1f) and the cyclic azine compound represented by the general formula (10). For example, when this material is used to form an emissive layer of an organic EL element, the compound represented by any one of the general formulas (1a) to (1f) and the compound represented by the general formula (10) may be supplied to the emissive layer individually, or the compound represented by any one of the general formulas (1a) to (1f) and the compound represented by the general formula (10) may be supplied as a premixed material for organic electroluminescent elements in which the compound represented by any one of the general formulas (1a) to (1f) and the compound represented by the general formula (10) are premixed. Among these, it is preferable to supply the compound represented by any one of the general formulas (1a) to (1f) and the compound represented by the general formula (10) as a premixed material for organic electroluminescent elements in which the compound represented by any one of the general formulas (1a) to (1f) and the compound represented by the general formula (10) are premixed.

[0042] The mixed material for organic electroluminescent devices may be prepared by mixing the compounds represented by the general formulas (1a) to (1f) and the compound represented by the general formula (10) in powder form, by melt-mixing by heating under reduced pressure or in an inert gas atmosphere such as nitrogen, or by sublimating the mixed compounds together. It may also be prepared as a thin film by vapor deposition or the like. On the other hand, if the compounds represented by the general formulas (1a) to (1f) and the compound represented by the general formula (10) that constitute the mixed material are not premixed in advance, they may be contained in different organic layers of the device. For example, the electron-blocking layer may contain the compounds represented by the general formulas (1a) to (1f), and the light-emitting layer may contain the compound represented by the general formula (10). The premixed material for organic electroluminescent devices refers to a mixed material for organic electroluminescent devices in which the compounds represented by the general formulas (1a) to (1f) and the compound represented by the general formula (10) are premixed in powder form, or premixed in advance by heating and melting these powders.

[0043] In the mixed material for organic electroluminescent elements and the premixed material for organic electroluminescent elements, the mixing ratio (mass ratio) of the compounds represented by the general formulas (1a) to (1f) to the compound represented by the general formula (10) is preferably 40 to 90 mass%, more preferably 50 to 90 mass%, and even more preferably 60 to 90 mass%, of the compound represented by the general formula (1) relative to the total of the compounds represented by the general formulas (1a) to (1f) and the compound represented by the general formula (10).

[0044] Specific examples of the compounds represented by general formulas (1a) to (1f) are shown below, but the present invention is not limited to these exemplary compounds. Note that Dn represents the number of deuterium (D) contained in the molecule.

[0045]

[0046] Among the exemplary compounds represented by the general formulas (1a) to (1f), any of the formulas (1) to (18), (21), (25), (28), (32), (42), (47), (59), (72), and (73) is preferred. This is because the triplet excitation energy (T1(A) or T1(E)) is localized in A or E as a partial structure, thereby localizing the distribution of triplet excitation energy throughout the molecule and spatially reducing the active sites in the excited state, which is preferable in that deterioration of the material is suppressed.

[0047] Specific examples of the compound represented by formula (10) are shown below, but the present invention is not limited to these exemplary compounds.

[0048]

[0049] The present invention also relates to an organic electroluminescent element comprising one or more organic layers between an anode and a cathode facing each other, wherein at least one of the organic layers contains a compound represented by any one of the general formulae (1a) to (1f) or a mixed material for an organic electroluminescent element comprising a compound represented by any one of the general formulae (1a) to (1f) and a compound represented by the general formula (10), and preferably the organic layer contains the premixed material for an organic electroluminescent element.

[0050] In the organic electroluminescent device of the present invention, at least one organic layer is preferably an emitting layer, and the emitting layer preferably contains the mixed material for organic electroluminescent devices. More preferably, the emitting layer further contains a thermally activated delayed fluorescent material or a phosphorescent material, and even more preferably, the emitting layer further contains a thermally activated delayed fluorescent material and a phosphorescent material. Furthermore, the thermally activated delayed fluorescent material preferably contains a boron atom, and the phosphorescent material preferably contains a platinum atom.

[0051] That is, an excellent organic EL device can be obtained by optionally incorporating at least one host material in the light-emitting layer together with a thermally activated delayed fluorescent material or a phosphorescent material, and it is preferable that at least one host material is a material for an organic electroluminescent device that is a compound represented by any one of the general formulae (1a) to (1f). Furthermore, when the light-emitting layer contains at least two host materials, it is preferable to use a compound represented by any one of the general formulae (1a) to (1f) as the first host and a compound represented by the general formula (10) as the second host.

[0052] Furthermore, the present invention relates to a method for producing an organic electroluminescent device comprising one or more organic layers between opposing anode and cathode, at least one of which is an emissive layer, the emissive layer being formed by vapor deposition from a single vapor deposition source using a premixed material for organic electroluminescent devices, which is a mixture of a compound represented by any one of the general formulas (1a) to (1f) and a cyclic azine compound represented by the general formula (10). Specifically, in producing the organic layer of the organic electroluminescent device, the compound represented by any one of the general formulas (1a) to (1f) and the compound represented by the general formula (10) are premixed in advance as powders, or these powders are premixed in advance by heating and melting to form a premixed material for organic electroluminescent devices, which is then vapor-deposited from a single vapor deposition source to form the emissive layer of the organic EL device.

[0053] Next, the structure of the organic EL element of the present invention will be described with reference to the drawings, but the structure of the organic EL element of the present invention is not limited to this.

[0054] 1 is a cross-sectional view showing an example of the structure of a general organic EL element used in the present invention, in which 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents a light-emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. The organic EL element of the present invention has an anode, a light-emitting layer, and a cathode as essential layers, but may also have a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the essential layers, and may further have an electron blocking layer between the hole transport layer and the light-emitting layer, and a hole blocking layer between the light-emitting layer and the electron transport layer.

[0055] 1 , it is also possible to laminate the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, hole injection layer 3, and anode 2 in this order on the substrate 1, and in this case too, layers can be added or omitted as necessary. In the organic EL element described above, layers constituting the laminated structure on the substrate other than electrodes such as the anode and cathode may be collectively referred to as organic layers.

[0056] The organic EL device of the present invention is preferably supported on a substrate. There are no particular limitations on the substrate, and any substrate conventionally used in organic EL devices, such as glass, transparent plastic, or quartz, can be used.

[0057] Anode: Anode materials for organic EL devices are preferably metals, alloys, electrically conductive compounds, or mixtures thereof, each having a large work function (4 eV or more). Specific examples of such electrode materials include metals such as Au, CuI, indium tin oxide (ITO), and SnO. ２ Examples of suitable conductive transparent materials include ZnO and ZnO. Amorphous materials, such as IDIXO (In2O3-ZnO), that can be used to fabricate transparent conductive films, may also be used. The anode may be formed by depositing a thin film of these electrode materials using methods such as vapor deposition or sputtering, followed by forming a desired pattern using photolithography. Alternatively, if pattern precision is not required (approximately 100 μm or greater), a pattern may be formed using a mask of the desired shape during vapor deposition or sputtering of the electrode material. Alternatively, when using a coatable material such as an organic conductive compound, wet film formation methods such as printing or coating can be used. When extracting light from this anode, a transmittance of greater than 10% is desirable, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness, depending on the material, is typically selected in the range of 10 to 1,000 nm, preferably 10 to 200 nm.

[0058] - Cathode - On the other hand, the cathode material is made of a metal (called an electron injecting metal), alloy, electrically conductive compound, or a mixture thereof, each of which has a small work function (4 eV or less). Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, and aluminum / aluminum oxide (Al ２ O ３Among these, in view of electron injection property and durability against oxidation, etc., mixtures of an electron injection metal and a second metal which is a metal having a larger and more stable work function than the electron injection metal, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ２ O ３ ) mixture, lithium / aluminum mixture, aluminum, etc. are suitable. The cathode can be produced by forming a thin film of these cathode materials by methods such as vapor deposition or sputtering. The cathode preferably has a sheet resistance of several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit emitted light, it is advantageous if either the anode or cathode of the organic EL element is transparent or semitransparent, as this improves the luminance of the emitted light.

[0059] Furthermore, a transparent or semitransparent cathode can be fabricated by forming the above-mentioned metal as a cathode with a film thickness of 1 to 20 nm and then forming the conductive transparent material described in the description of the anode thereon. This can be applied to fabricate an element in which both the anode and cathode are transparent.

[0060] -Light-emitting layer- The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and cathode, respectively. The light-emitting layer may be a single layer or multiple layers, and each layer contains an organic light-emitting dopant material and a host material.

[0061] The light-emitting layer may contain only one type of organic light-emitting dopant, or may contain two or more types of organic light-emitting dopant. The content of the organic light-emitting dopant is preferably 0.1 to 50% by mass, more preferably 0.1 to 40% by mass, based on the host material.

[0062] When a phosphorescent dopant is used as the organic light-emitting dopant material, the phosphorescent dopant preferably contains an organometallic complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. More preferably, the phosphorescent dopant is an organometallic complex containing platinum. Specific examples of suitable dopants include, but are not limited to, the iridium complexes described in J. Am. Chem. Soc. 2001, 123, 4304 and JP-A-2013-530515 and the platinum complexes described in Adv. Mater. 2014, 26, 7116 and JP-A-2018-2722.

[0063] The phosphorescent dopant material is not particularly limited, but specific examples include the following.

[0064]

[0065] When a fluorescent dopant is used as the light-emitting dopant material, the fluorescent dopant is not particularly limited, but examples thereof include fused polycyclic aromatic derivatives, styrylamine derivatives, fused-ring amine derivatives, boron-containing compounds, pyrrole derivatives, indole derivatives, and carbazole derivatives. Among these, fused-ring amine derivatives, boron-containing compounds, and carbazole derivatives are preferred. Examples of fused-ring amine derivatives include diaminepyrene derivatives, diaminochrysene derivatives, diaminoanthracene derivatives, diaminofluorenone derivatives, and diaminofluorene derivatives having one or more fused benzofuro skeletons. Examples of boron-containing compounds include pyrromethene derivatives and polycyclic aromatic compounds described in WO2015 / 102118 and the like.

[0066] The fluorescent dopant material is not particularly limited, but specific examples include the following.

[0067]

[0068] When a thermally activated delayed fluorescent dopant is used as the luminescent dopant material, the thermally activated delayed fluorescent dopant is not particularly limited, and examples thereof include those containing boron atoms, metal complexes such as tin complexes and copper complexes, cyanobenzene derivatives and carbazole derivatives described in Nature 2012,492,234, phenazine derivatives, oxadiazole derivatives, triazole derivatives, sulfone derivatives, phenoxazine derivatives, acridine derivatives described in Nature Photonics 2014,8,326, and polycyclic aromatic compounds described in WO2015 / 102118, etc. Preferably, the thermally activated delayed fluorescent dopant contains a boron atom.

[0069] The thermally activated delayed fluorescent dopant material is not particularly limited, but specific examples include the following: A cyclic azine compound may be used as the thermally activated delayed fluorescent dopant material, but it is preferable that the compound is not a compound represented by the general formula (10).

[0070]

[0071] The host material in the light-emitting layer is preferably a compound represented by any of the general formulae (1a) to (1f) and / or (10). When the compound represented by any of the general formulae (1a) to (1f) or (10) is used in any organic layer other than the light-emitting layer, the compound represented by any of the general formulae (1a) to (1f) or (10) may or may not be contained in the light-emitting layer. In this case, the light-emitting layer may also contain a known host material used in phosphorescent or fluorescent light-emitting devices. Multiple known host materials may be used in combination, or each may be used alone. Usable known host materials are preferably compounds that have hole-transporting and electron-transporting capabilities and a high glass transition temperature, and have a triplet excitation energy (T1(h)) greater than the triplet excitation energy (T1(exp)) of the light-emitting dopant material. A compound active in delayed fluorescence (TADF) may also be used as the host material. In this case, a compound having a difference (ΔEST = S1(h) - T1(h)) between the singlet excitation energy (S1(h)) and the triplet excitation energy (T1(h)) of 0.20 eV or less is preferred. The compound represented by the general formula (1) may be used alone as a host material in the light-emitting layer, and another known host material may be used in combination. However, in order to improve the characteristics of the organic EL device, it is preferable to use a compound represented by the general formula (10) in combination as a host material. A plurality of other known host materials may also be used in combination. Here, S1(h), T1(h), and ΔEST = S1(h) - T1(h) are measured as follows. A quartz substrate is coated with a thin film of 10% fluorescein by vacuum deposition. －４A sample compound (a compound active in delayed fluorescence (TADF)) is vapor-deposited under conditions of 0.1 Pa or less to form a vapor-deposited film with a thickness of 100 nm. S1(h) is calculated by measuring the emission spectrum of the vapor-deposited film, drawing a tangent to the rising edge of the emission spectrum on the short wavelength side, and substituting the wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis into the following formula (i): S1(h) [eV] = 1239.85 / λedge (i) Meanwhile, T1(h) is calculated by measuring the phosphorescence spectrum of the vapor-deposited film, drawing a tangent to the rising edge of the phosphorescence spectrum on the short wavelength side, and substituting the wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis into the following formula (ii): T1(h) [eV] = 1239.85 / λedge (ii) ΔEST can be calculated from S1(h) and T1(h) determined above.

[0072] The other known host materials can be selected from those known in numerous patent documents, etc. Specific examples of the host material include, but are not particularly limited to, indole compounds, carbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, triazole compounds, oxazole compounds, oxadiazole compounds, imidazole compounds, phenylenediamine compounds, arylamine compounds, anthracene compounds, fluorenone compounds, stilbene compounds, triphenylene compounds, carborane compounds, porphyrin compounds, phthalocyanine compounds, metal complexes of 8-quinolinol compounds, metal phthalocyanines, various metal complexes typified by metal complexes of benzoxazole and benzothiazole compounds, polymer compounds such as poly(N-vinylcarbazole) compounds, aniline copolymer compounds, thiophene oligomers, polythiophene compounds, polyphenylene compounds, polyphenylenevinylene compounds, and polyfluorene compounds. Preferred examples include carbazole compounds, indolocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, anthracene compounds, triphenylene compounds, carborane compounds, and porphyrin compounds.

[0073] The other known hosts are not particularly limited, but specific examples include the following compounds.

[0074] When a plurality of hosts are used, each host can be vapor-deposited from a different vapor deposition source, or a plurality of hosts can be mixed before vapor deposition and then vapor-deposited simultaneously from a single vapor deposition source.

[0075] When multiple types of hosts are used, the hosts are preferably the mixed material for organic electroluminescent devices containing the compounds represented by the general formulas (1a) to (1f) and the compound represented by the general formula (10). When two types of hosts are used, the premixed material for organic electroluminescent devices is preferably composed of the compounds represented by the general formulas (1a) to (1f) and the compound represented by the general formula (10). Furthermore, when the compounds represented by the general formulas (1a) to (1f) and the compound represented by the general formula (10) are used as hosts, the first host is the compound represented by the general formula (1), and the compound represented by the general formula (10) is the second host.

[0076] In order to reproducibly produce an organic EL device having good characteristics, the 50% weight loss temperature (T 50 ) is small, and preferably the difference in 50% weight loss temperature is within 20°C. The 50% weight loss temperature refers to the temperature at which a 50% weight loss occurs when the temperature is raised from room temperature to 550°C at a rate of 10°C per minute in TG-DTA measurement under reduced pressure (1 Pa) of nitrogen flow. It is believed that vaporization by evaporation or sublimation occurs most actively around this temperature. When the difference in 50% weight loss temperature between the first host and the second host is within 20°C, a uniform vapor-deposited film can be obtained by vaporizing and depositing them from a single evaporation source. In this case, the mixed material for an organic electroluminescent device may contain, in addition to the first host and second host, a light-emitting dopant material required for forming an emitting layer or other hosts used as needed. However, if there is a large difference in the temperatures at which the desired vapor pressure is achieved, it is preferable to deposit them from separate evaporation sources.

[0077] When two types of hosts are used, the mixing ratio (mass ratio) of the first host to the second host is such that the proportion of the first host relative to the total of the first host and the second host is 40 to 90%, preferably 50 to 90%, and more preferably 60 to 90%.

[0078] When a plurality of types of hosts are used, the method for previously mixing the hosts is preferably a method that can mix them as uniformly as possible, and examples thereof include pulverization and mixing, a method of heating and melting under reduced pressure or in an inert gas atmosphere such as nitrogen, and sublimation, but are not limited to these methods.

[0079] The host and its premixed material may be in the form of powder, stick, or granules.

[0080] Injection layer: An injection layer is a layer provided between an electrode and an organic layer to reduce driving voltage and improve luminance, and includes a hole injection layer and an electron injection layer. An injection layer may be provided between the anode and the light-emitting layer or the hole transport layer, and between the cathode and the light-emitting layer or the electron transport layer. An injection layer can be provided as needed.

[0081] -Hole Blocking Layer- In a broad sense, the hole blocking layer functions as an electron transport layer and is made of a hole blocking material that has the function of transporting electrons but has a significantly low ability to transport holes. By transporting electrons while blocking holes, the probability of electron and hole recombination in the light-emitting layer can be improved. Known hole blocking materials can be used for the hole blocking layer. Multiple hole blocking materials may also be used in combination.

[0082] -Electron Blocking Layer- In a broad sense, the electron blocking layer functions as a hole transport layer, and by transporting holes while blocking electrons, it is possible to improve the probability of electrons and holes recombining in the light-emitting layer. As the material for the electron blocking layer, it is preferable to use the compound represented by the general formula (1) or the mixed material, but known electron blocking layer materials can also be used. When the compound represented by the general formula (1) or the mixed material is used in the electron blocking layer, the host material may be the compound represented by the general formula (1), the known host materials described above, or a host material obtained by combining two or more of these.

[0083] Layers adjacent to the light-emitting layer include a hole-blocking layer and an electron-blocking layer, but if these layers are not provided, a hole-transporting layer, an electron-transporting layer, etc. will be the adjacent layers.

[0084] -Hole Transport Layer- The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer may be provided as a single layer or as a plurality of layers.

[0085] The hole transport material has either hole injection or transport properties or electron barrier properties, and may be either organic or inorganic. Any hole transport material can be selected from conventionally known compounds. Examples of such hole transport materials include porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

[0086] - Electron Transport Layer - The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer may be a single layer or multiple layers.

[0087] The electron transport material (which may also serve as a hole blocking material) may have the function of transporting electrons injected from the cathode to the light-emitting layer. The electron transport layer may be formed from any of conventionally known compounds, including polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline; tris(8-quinolinolato)aluminum(III) derivatives; phosphine oxide derivatives; nitro-substituted fluorene derivatives; diphenylquinone derivatives; thiopyran dioxide derivatives; carbodiimides; fluorenylidenemethane derivatives; anthraquinodimethane and anthrone derivatives; bipyridine derivatives; quinoline derivatives; oxadiazole derivatives; benzimidazole derivatives; benzothiazole derivatives; and indolocarbazole derivatives. Furthermore, polymeric materials in which any of these materials are incorporated into a polymer chain or in which any of these materials form the polymer backbone may also be used.

[0088] When the organic EL element of the present invention is produced, the method for forming each layer is not particularly limited, and the layers may be produced by either a dry process or a wet process.

[0089] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0090] Calculation Example To investigate T1(A) and T1(E) when A or E is (2a-1) to (2e-1), as explained above, the T1 of the following compounds (2a-2) to (2e-2) bonded to hydrogen at the bonding position * with the general formulae (1a) to (1f) was calculated by the following method. Specifically, using the molecular orbital method program Gaussian 16, geometry optimization calculations were performed at the B3LYP / 6-31G* level using density half-function theory (DFT), and each T1 was calculated at the TD-B3LYP / 6-31G* level. The results are shown in Table 1.

[0091]

[0092] The T1 calculated as above was regarded as T1(A) and T1(E), and |T1(A) - T1(E)| was calculated for the following compounds (1), (2), and (4) represented by general formulas (1a) to (1f). The results are shown in Table 2. The skeletons of A and E in the following compounds (1), (2), and (4) are as shown in Table 2.

[0093]

[0094] It can be seen from Table 2 that compounds (1), (2), and (4) have a preferred |T1(A)-T1(E)|.

[0095] Synthesis Example 1: In the formula, Dn independently indicates that some or all of the hydrogen atoms in the compound are deuterated. To 5.0 g of compound (1)-H, 100 ml of deuterated benzene (CD6) and 8.0 g of deuterated trifluoromethanesulfonic acid (TfOD) were added, and the mixture was heated and stirred at 50° C. for 4 hours under a nitrogen atmosphere. The reaction mixture was added to a deuterated water solution (100 ml) of sodium carbonate (5.0 g), and the mixture was quenched. After separation and purification, 1.0 g of the deuterated compound (1) was obtained.

[0096] Synthesis Example 2 To 5.0 g of compound (2)-H, 100 ml of deuterated benzene (CD6) and 8.0 g of deuterated trifluoromethanesulfonic acid (TfOD) were added, and the mixture was heated and stirred at 50° C. for 4 hours under a nitrogen atmosphere. The reaction mixture was added to a deuterated solution (100 ml) of sodium carbonate (5.0 g) in heavy water, and the mixture was quenched. After separation and purification, 1.2 g of the deuterated compound (2) was obtained.

[0097] Synthesis Example 3 To 5.0 g of compound (4)-H, 100 ml of deuterated benzene (CD6) and 8.0 g of deuterated trifluoromethanesulfonic acid (TfOD) were added, and the mixture was heated and stirred at 50°C for 4 hours under a nitrogen atmosphere. The reaction mixture was added to a deuterated solution (100 ml) of sodium carbonate (5.0 g) and quenched, followed by separation and purification to obtain 1.2 g of the deuterated product, compound (1).

[0098] Synthesis Example 4 To 5.0 g of compound (4)-T1, 6.1 g of (4)-T2, 100 mL of m-xylene, 0.2 g of bis(tri-tert-butylphosphine)palladium, and 4.9 g of potassium carbonate were added, and the mixture was stirred under reflux for 5 hours under a nitrogen atmosphere. After cooling, the reaction mixture was separated and purified to obtain 1.1 g of compound (4)-P, a deuterated product, as a white solid.

[0099] The average deuteration ratios of the compounds used in the examples and comparative examples are listed in Table 3 below. The average deuteration ratio indicates the proportion of hydrogen contained in the compound that is deuterated, and was determined by mass spectrometry or proton nuclear magnetic resonance spectroscopy. As a representative example, the method for determining the average deuteration ratio of compound (1) by proton nuclear magnetic resonance spectroscopy is described below. First, a measurement sample was prepared by dissolving compound (1) (5.0 mg) and dimethyl sulfone (2.0 mg) as an internal standard in deuterated tetrahydrofuran (1.0 ml). The average proton concentration [mol / g] of compound (1) contained in the measurement sample was calculated from the integrated intensity ratio derived from the internal standard and compound (1). The average proton concentration [mol / g] of the non-deuterated form of compound (1) ((1)-H) was also calculated in the same manner. Next, the average deuteration ratio of compound (1) was calculated by calculating the ratio of the proton concentration of compound (1) to the proton concentration of the non-deuterated form of compound (1) ((1)-H), and subtracting this ratio from 1. The average deuteration ratios of other compounds used in the examples and comparative examples were also calculated in the same manner.

[0100]

[0101] Compound (4)-P was synthesized using compound (4)-T1, which was previously deuterated and had an average deuteration rate of 89%, in the biscarbazole partial skeleton corresponding to partial skeleton E. Therefore, the average deuteration rate of the biscarbazole corresponding to partial skeleton E of compound (4)-P is 89%, and the average deuteration rate of the entire compound (4)-P is 38%.

[0102] The compounds used in the examples and comparative examples are shown below.

[0103] Example 1 On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the thin films shown below was deposited by vacuum deposition at a vacuum degree of 4.0 × 10 －５ The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1) was co-deposited as a host, BD-2 as a phosphorescent dopant, and BD-1 as a thermally activated delayed fluorescent dopant from different deposition sources to form an emitting layer having a thickness of 40 nm. At this time, the co-deposition was performed under deposition conditions such that the concentration of BD-2 was 13% by mass, the concentration of BD-1 was 0.4% by mass, and the concentration of compound (1) was 86.6% by mass. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer. Finally, aluminum (Al) was formed as a cathode on the electron injection layer to a thickness of 70 nm, thereby completing the organic electroluminescent device according to Example 1.

[0104] Comparative Example 1 As shown in Table 5, an organic electroluminescent device was produced in the same manner as in Example 1, except that the host was changed to HT-2.

[0105] Examples 2 to 9 Organic electroluminescent devices were fabricated in the same manner as in Example 1, except that the electron blocking layer material and the first host were changed to the compounds shown in Table 4.

[0106] Example 10: On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the thin films shown below was deposited by vacuum deposition at a vacuum degree of 4.0×10 －５The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1) was used as a first host, compound (2-49) was used as a second host, BD-2 was used as a phosphorescent dopant, and BD-1 was used as a thermally activated delayed fluorescent dopant, all of which were co-deposited from different evaporation sources to form an emitting layer having a thickness of 40 nm. The co-deposition was carried out under evaporation conditions such that the concentration of BD-2 was 13% by mass, the concentration of BD-1 was 0.4% by mass, and the mass ratio of the first host to the second host was 50:50. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer, and finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby producing an organic electroluminescent device according to Example 10.

[0107] Examples 11 to 28, Examples B-1 to B-6, Comparative Examples 2 to 23 Organic electroluminescent devices were fabricated in the same manner as in Example 10, except that the electron-blocking layer material, the first host, and the second host were the compounds shown in Tables 4 and 5, and the mixing ratio of the first host to the second host was the mixing ratio shown in Tables 4 and 5.

[0108]

[0109]

[0110] The evaluation results of the fabricated organic electroluminescent devices are shown in Tables 6 and 7. When an external power supply was connected to the organic electroluminescent devices obtained in the Examples and Comparative Examples and a DC voltage was applied, an emission spectrum with a maximum emission wavelength of 450 nm to 480 nm was observed in all organic electroluminescent devices, indicating that light was emitted from BD-1. The voltage and power efficiency in the tables are values ​​at a driving current of 2.5 mA / cm2 and represent initial characteristics. Furthermore, the lifetime is the time it takes for the brightness to decay to 97%, assuming the initial brightness at a driving current of 4.0 mA / cm2 is 100%, and represents the lifetime characteristics. The emitted color was confirmed by the emission spectrum of the organic electroluminescent device. The results of the Examples and Comparative Examples shown in Tables 6 and 7 demonstrate that organic electroluminescent devices using the mixed material for organic electroluminescent devices of the present invention as a host in the light-emitting layer emit blue light and have low voltage, high efficiency, and long lifetime characteristics.

[0111]

[0112]

[0113] Example 29 On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the thin films shown below was deposited by vacuum deposition at a vacuum degree of 4.0 × 10 －５ The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1) was co-deposited as a first host and BD-2 as a phosphorescent dopant from different deposition sources to form an emitting layer having a thickness of 40 nm. This co-deposition was performed under deposition conditions such that the concentration of BD-2 was 13% by mass. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby producing an organic EL device according to Example 29.

[0114] Examples 30 to 37 and Comparative Example 24 As shown in Table 8, organic EL devices were prepared in the same manner as in Example 29, except that the compounds shown in Table 8 were used as the first host.

[0115] Example 38: On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the following thin films was deposited by vacuum deposition at a vacuum degree of 4.0×10 －５ The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1) was co-deposited as a first host, compound (2-49) as a second host, and BD-2 as a phosphorescent dopant from different evaporation sources to form an emitting layer having a thickness of 40 nm. This co-deposition was carried out under evaporation conditions such that the concentration of BD-2 was 13% by mass. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer on the electron transport layer to a thickness of 1 nm. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby completing the organic EL device according to Example 38.

[0116] Examples 39 to 55 and Comparative Examples 25 to 42 Organic EL devices were prepared in the same manner as in Example 38, except that the electron-blocking layer material, the first host, and the second host were compounds shown in Table 8, and the mixing ratio of the first host to the second host was the mixing ratio shown in Table 8.

[0117]

[0118] The evaluation results of the fabricated organic EL devices are shown in Table 9. The voltage and power efficiency in the table are values ​​at a driving current of 2.5 mA / cm2, which represent initial characteristics. The lifetime is the time it takes for the brightness to decay to 97%, assuming the initial brightness at a driving current of 4.0 mA / cm2 is 100%, and represents the lifetime characteristics. The emitted color was confirmed by the emission spectrum of the organic EL device.

[0119]

[0120] 1 Substrate, 2 Anode, 3 Hole injection layer, 4 Hole transport layer, 5 Light-emitting layer, 6 Electron transport layer, 7 Cathode

[0121] According to the present invention, it is possible to obtain a practically useful organic EL element that emits light with high efficiency and has a long life, while being driven at a low voltage.

Claims

1. A material for organic electroluminescent devices, which is a compound represented by any one of the following general formulas (1a) to (1f), characterized in that the average deuteration rate of hydrogen in the compound is 20% or more. Here, X is represented by O or S. A and E are each independently represented by the following general formulas (2a) to (2e), and A and E are different from each other. However, A or E is represented by (2e) only in the case of the general formula (1c) or (1d). * indicates the bonding position with the general formulae (1a) to (1f). １ ~R ７ each independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups, provided that R ２ ~R ７ does not contain carbazole.

2. The material for organic electroluminescent devices according to claim 1, wherein the average deuteration rate of A or E is 80% or more.

3. The material for organic electroluminescent devices according to claim 1, wherein the average deuteration rate of each of A and E is 80% or more.

4. The material for organic electroluminescent elements according to claim 1, characterized in that when the triplet excitation energy of A as a partial skeleton of the material for organic electroluminescent elements represented by any of the general formulae (1a) to (1f) is represented as T1(A) and the triplet excitation energy of E as a partial skeleton is represented as T1(E), |T1(A) - T1(E)| is 0.02 eV or higher.

5. The material for organic electroluminescent devices according to claim 4, characterized in that the partial skeleton of T1(A) or T1(E), whichever has the lower energy, has an average deuteration rate of 85% or more.

6. The material for organic electroluminescent devices according to claim 1, characterized in that it is represented by the general formula (1a).

7. The material for organic electroluminescent devices according to claim 6, wherein A and E are (2a), (2b) or (2c).

8. The material for organic electroluminescent devices according to claim 6, wherein A and E are (2b) or (2c), and each has an average deuteration rate of 70% or more.

9. A mixed material for organic electroluminescent devices, comprising a compound represented by any one of general formulas (1a) to (1f) according to claim 1 and a cyclic azine compound represented by the following general formula (10): (where Ar ２ and Ar ３ each independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups. １ represents a single bond or a substituted or unsubstituted phenyl group. Some or all of the hydrogen atoms in the compound represented by the general formula (10) may be substituted with deuterium atoms.

10. An organic electroluminescent device comprising one or more organic layers between opposing anode and cathode, wherein at least one of the organic layers contains the material for organic electroluminescent devices according to claim 1.

11. An organic electroluminescent device comprising one or more organic layers between opposing anode and cathode, wherein at least one of the organic layers contains the mixed material for organic electroluminescent devices according to claim 9.

12. The organic electroluminescent device according to claim 11, wherein the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and the emitting layer further contains a thermally activated delayed fluorescent material.

13. The organic electroluminescent device according to claim 12, wherein the thermally activated delayed fluorescent material is a thermally activated delayed fluorescent material containing a boron atom.

14. The organic electroluminescent device according to claim 11, wherein the organic layer containing the mixed material for organic electroluminescent devices is a light-emitting layer, and the light-emitting layer further contains a phosphorescent material.

15. The organic electroluminescent device according to claim 14, wherein the phosphorescent material is a phosphorescent material containing platinum atoms.

16. The organic electroluminescent device according to claim 11, wherein the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and the emitting layer contains a thermally activated delayed fluorescent material containing boron atoms and a phosphorescent material containing platinum atoms.

17. An organic electroluminescent device comprising one or more organic layers between opposing anode and cathode, at least one of which is an emitting layer, the emitting layer containing the mixed material for organic electroluminescent devices according to claim 9 as a mixed host material, and further containing a thermally activated delayed fluorescent material containing boron atoms and a phosphorescent material containing platinum atoms.

18. A premixed material for organic electroluminescent devices comprising a compound represented by any one of general formulas (1a) to (1f) according to claim 1 and a cyclic azine compound represented by the following general formula (10): (where Ar ２ and Ar ３ each independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups. １ represents a single bond or a substituted or unsubstituted phenyl group. Some or all of the hydrogen atoms in the compound represented by the general formula (10) may be substituted with deuterium atoms.

19. An organic electroluminescent device comprising one or more organic layers between opposing anode and cathode, wherein at least one of the organic layers contains the premixed material for organic electroluminescent devices according to claim 18.

20. A method for producing an organic electroluminescent device having one or more organic layers between opposing anode and cathode, at least one of which is an emitting layer, the method comprising depositing the premixed material for organic electroluminescent devices according to claim 18 from a single deposition source.

21. A material for organic electroluminescent devices, wherein the compound represented by general formulas (1a) to (1f) according to claim 1 is any one of the following formulas (1) to (18), (21), (25), (28), (32), (42), (47), (59), (72), and (73), where Dn is the number of deuterium (D) contained in the molecule.

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