Mixed material for organic electroluminescent element, and organic electroluminescent element using same

Abstract

Provided is a material for an organic electroluminescent element, with which it is possible to achieve a practically useful organic EL element that has long service life characteristics while being driven at a low voltage.　This mixed material for an organic electroluminescent element is characterized by containing a first compound which is composed of a compound represented by general formula (1) or the like and a second compound which is composed of a compound represented by general formula (2) or (3), or the like. R1 to R17 each represent hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or the like, at least one or more hydrogen atoms or all hydrogen atoms in the compound represented by general formula (1) may be substituted with deuterium, and at least one or more hydrogen atoms or all hydrogen atoms in the compound represented by general formula (2) or (3) may be substituted with deuterium.

Description

Mixed material for organic electroluminescent devices, and organic electroluminescent devices using the same.

[0001] The present invention relates to a mixed material for organic electroluminescent devices (referred to as organic EL devices) that can convert electrical energy into light, and to an organic EL device using the same.

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

[0003] In recent years, advancements have been made in technologies for extending the lifespan of phosphorescent organic EL elements, and these are being applied to displays in mobile phones and other devices. However, no practical phosphorescent organic EL elements have been developed for blue light, and there is a need for the development of highly efficient and long-lasting blue organic EL elements.

[0004] More recently, highly efficient delayed fluorescence type organic EL elements have been developed using delayed fluorescence. For example, Patent Document 1 discloses an organic EL element that utilizes the TTF (Triplet-Triplet Fusion) mechanism, one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon in which a singlet exciton is generated by the collision of two triplet excitons, and it is theoretically thought that the internal quantum efficiency can be increased to 40%. However, since its efficiency is lower compared to phosphorescent type organic EL elements, further improvements in efficiency are needed.

[0005] On the other hand, Patent Document 2 discloses an organic EL device utilizing the thermally activated delayed fluorescence (TADF) mechanism. The TADF mechanism utilizes the phenomenon in which reverse intersystem crossing occurs from triplet excitons to singlet excitons in materials where the energy difference between the singlet and triplet levels is small, and it is theoretically thought that the internal quantum efficiency can be increased to 100%.

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

[0007] Furthermore, while Patent Documents 3 to 5 disclose devices using a mixed material containing a compound in which multiple carbazoles are linked and a compound in which triazine and arylsilyl are linked, the lifetime characteristics are not sufficient.

[0008] Furthermore, Patent Document 6 discloses a device using a premixed material containing a compound in which carbazole and dibenzofuran are linked via benzene, and a compound in which triazine and carbazole are linked via benzene, but the lifetime characteristics are not sufficient.

[0009] Furthermore, Patent Document 7 discloses a device using a mixed material containing a compound in which multiple carbazoles are linked together and a compound in which triazine and carbazole are linked via benzene, but its lifetime characteristics are not sufficient.

[0010] Furthermore, Patent Document 8 discloses a device using a mixed material containing a compound in which carbazole is linked to an arylsilyl and a compound in which triazine and carbazole are linked via benzene, but the lifetime characteristics are not sufficient.

[0011] Furthermore, Patent Documents 9 to 13 disclose devices using mixed materials containing compounds in which carbazole is linked to specific substituents and compounds in which triazine and carbazole are linked via benzene, but none of these exhibit sufficient lifetime characteristics.

[0012] Publication No. WO2010 / 134350, Publication No. WO2011 / 070963, Publication No. WO2023 / 162701, Publication No. US2024 / 196742, Publication No. EP4273127, Publication No. US2024 / 260290, Publication No. US2024 / 276875, Publication No. US2024 / 074308, Publication No. US2020 / 168812, Publication No. US2024 / 188419, JP 2022-132157, Publication No. US2023 / 363273, Publication No. US2023 / 363272

[0013] Kim et al., Sci. Adv. 8, eabq1641 (2022)

[0014] In order to apply organic EL elements as display elements or light sources in flat panel displays and the like, it is necessary to improve the luminous efficiency of the elements while simultaneously ensuring sufficient stability during operation. However, conventional materials consisting of known combinations of compounds cannot achieve these goals.

[0015] This invention has been made in view of the current situation, and aims to provide an organic electroluminescent element material that can be used to obtain a practically useful organic EL element with long lifespan characteristics while being driven at low voltage. Furthermore, this invention aims to provide an organic EL element using such a material.

[0016] In other words, the present invention is a mixed material for an organic electroluminescent element, characterized in that it contains one or more compounds selected from the group consisting of compounds represented by the following general formulas (1), (10), and (11) as a first compound, and one or more compounds selected from the group consisting of compounds represented by the following general formulas (2) to (7) as a second compound.

[0017] Here, R １ R represents hydrogen, deuterium, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms. １ It is preferably hydrogen or deuterium, and more preferably deuterium. ２ ~R ７Each independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 of the aromatic hydrocarbon groups. R ２ ~R ７ is preferably hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, more preferably hydrogen, deuterium, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and even more preferably hydrogen or deuterium. Further, at least one hydrogen or all hydrogens in the first compound selected from the group consisting of the compounds represented by General Formulas (1), (10), and (11) are substituted with deuterium. Here, R ８ ~R １７ Each independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 of the aromatic hydrocarbon groups. R ８ ~R １７ is preferably hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, more preferably hydrogen, deuterium, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and even more preferably hydrogen or deuterium. Note that at least one hydrogen or all hydrogens in the second compound selected from the group consisting of the compounds represented by General Formulas (2) to (7) may be substituted with deuterium.

[0018] Furthermore, the mixed material for organic electroluminescent devices in the present invention may be a pre-mixed material for organic electroluminescent devices in which a first compound consisting of one or more compounds selected from the group consisting of compounds represented by general formulas (1), (10), and (11) is pre-mixed with a second compound consisting of one or more compounds selected from the group consisting of compounds represented by general formulas (2) to (7). In this case, the proportion of the first compound to the total pre-mixed material for organic electroluminescent devices is preferably 20% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, even more preferably 40% by mass or more and 70% by mass or less, and most preferably 50% by mass or more and 70% by mass or less.

[0019] Furthermore, in the mixed material for organic electroluminescent elements according to the present invention, the average deuterated rate of the first compound, which consists of one or more compounds selected from the group consisting of compounds represented by general formulas (1), (10), and (11), is preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more. Furthermore, with respect to the second compound, which consists of one or more compounds selected from the group consisting of compounds represented by general formulas (2) to (7), it is preferable that at least one hydrogen or all of the hydrogens in the compound are replaced with deuterium, and in this case, the average deuterated rate of the second compound, which consists of one or more compounds selected from the group consisting of compounds represented by general formulas (2) to (7), is preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more.

[0020] In the present invention, the first compound selected from the group consisting of the compounds represented by the general formulas (1), (10), and (11) is preferably any compound selected from the group consisting of the compounds represented by the following general formulas (1a) to (1g), (10a), (10b), and (11a) to (11c). Here, in the case of the first compound consisting of the compound represented by the general formula (1), it is more preferably any compound represented by the following general formulas (1b) to (1g). Further, in the case of the first compound consisting of the compound represented by the general formula (10), it is more preferably the compound represented by the following general formula (10b). Furthermore, in the case of the first compound consisting of the compound represented by the general formula (11), it is more preferably any compound represented by the following general formula (11b) or (11c).

[0021] Here, at least one hydrogen or all hydrogens in the first compound selected from the group consisting of the compounds represented by the general formulas (1a) to (1g), (10a), (10b), and (11a) to (11c) are substituted with deuterium.

[0022] Further, the second compound selected from the group consisting of the compounds represented by the general formulas (2) to (7) is preferably any compound selected from the group consisting of the compounds represented by the following general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a).

[0023] Here, at least one hydrogen or all hydrogens in the second compound selected from the group consisting of the compounds represented by the general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a) may be substituted with deuterium.

[0024] In the present invention, the combination of the first compound and the second compound is arbitrary. For example, a preferred combination is (i) a first compound comprising a compound represented by general formula (1) and a second compound comprising any compound selected from the group comprising compounds represented by general formulas (2), (3), (4), and (5). Similarly, (ii) a first compound comprising any compound selected from the group comprising compounds represented by general formulas (10) and (11) and a second compound comprising a compound represented by general formula (6). More preferably, (iii) a first compound comprising any compound selected from the group comprising compounds represented by general formulas (1a) to (1g) and a second compound comprising any compound selected from the group comprising compounds represented by general formulas (2a), (2b), (3a), (3b), (4a), and (5a). Similarly, [iv] the case in which a first compound consists of any compound selected from the group consisting of compounds represented by general formulas (10a), (10b), (11a) to (11c), and a second compound consists of a compound represented by general formula (6a).

[0025] Here, the average deuteration rate of the first compound, which is made up of any compound selected from the group consisting of compounds represented by the general formulas (1a) to (1g), (10a), (10b), and (11a) to (11c), is preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more. Furthermore, it is preferable that at least one hydrogen or all of the hydrogens in the second compound, which is made up of any compound selected from the group consisting of compounds represented by the general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a), are substituted with deuterium. In this case, it is preferable that the average deuterated rate of the second compound, which is one of the compounds selected from the group consisting of compounds represented by the general formulas (2) to (7) including these, is 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more.

[0026] When the compound consists of a compound represented by the general formula (1), the first compound is preferably a compound represented by any of the following (1-1) to (1-16). Furthermore, when the compound consists of a compound represented by the general formula (10), the first compound is preferably (10-1). Moreover, when the compound consists of a compound represented by the general formula (11), the first compound is preferably a compound represented by the following (11-1) or (11-2). In the following, D represents deuterium, and n means the average number of substitutions by deuterium in each compound, and changes according to the average deuterated rate.

[0027]

[0028] Furthermore, when the compound consists of the compound represented by general formula (2), the second compound is preferably the compound represented by (2-1) to (2-4) below. Furthermore, when the compound consists of the compound represented by general formula (3), the second compound is preferably the compound represented by (3-1) to (3-6) and (3-14) below. Furthermore, when the compound consists of the compound represented by general formula (4), the second compound is preferably the compound represented by (4-1) below. Furthermore, when the compound consists of the compound represented by general formula (5), the second compound is preferably the compound represented by (5-1) below. Moreover, when the compound consists of the compound represented by general formula (6), the second compound is preferably the compound represented by (6-1) below. Moreover, when the compound consists of the compound represented by general formula (7), the second compound is preferably the compound represented by (7-1) below. In the following, D represents deuterium, and n means the average number of substitutions by deuterium in each compound, and changes according to the average deuterated rate.

[0029]

[0030] The mixed material for the organic electroluminescent element in the present invention preferably includes a first compound selected from the group consisting of compounds represented by the general formulas (1), (10), and (11) as a hole-transporting compound, and a second compound selected from the group consisting of compounds represented by the general formulas (2) to (7) as an electron-transporting compound. This makes it possible to appropriately adjust the amount of holes and electrons in the organic electroluminescent element, and in particular, to appropriately adjust the amount of holes and electrons flowing through the light-emitting layer.

[0031] For example, in devices described in the aforementioned Patent Documents 3 to 5, a compound having a triazine skeleton is included as the electron-transporting compound. However, since the triazine skeleton easily transports electrons, the device becomes electron-richer than hole-rich, and it is thought that the imbalance between holes and electrons causes an extra load on the material, leading to a shorter lifespan. On the other hand, in the present invention, the compounds represented by the general formulas (2) to (7) have a structure in which the triazine skeleton and the carbazole skeleton are linked at the ortho position of benzene. As a result, the triazine skeleton is covered with a sterically bulky structure, which can suppress the excessive electron transport properties of the triazine skeleton. Furthermore, the compounds represented by general formulas (1) and (11) have a structure in which three carbazole skeletons are linked in series, and the compound represented by general formula (10) has two structures in which two carbazole skeletons are linked to a phenyl group. Since none of them contain extra aromatic rings such as dibenzofuran skeletons, the hole transportability is relatively high, and it is thought that the balance between holes and electrons is better than in devices such as those implemented in Patent Documents 6 to 13, and the extra load on the material is suppressed, thereby extending the lifespan.

[0032] In other words, the mixed material for organic electroluminescent devices in the present invention includes a first compound selected from the group consisting of compounds represented by the general formulas (1), (10), and (11) as a hole-transporting compound, and a second compound selected from the group consisting of compounds represented by the general formulas (2) to (7) as an electron-transporting compound. This allows for a better balance of holes and electrons than conventional mixed materials, enabling the organic EL device to be driven at a low voltage while maintaining a long lifespan. Since the balance of holes and electrons in an organic EL device varies greatly depending on the compounds included, we have investigated and diligently devised a variety of combinations of hole-transporting compounds and electron-transporting compounds. In this invention, the first compound is used as the hole-transporting compound, and the second compound is used as the electron-transporting compound.

[0033] Furthermore, since the balance of holes and electrons in an organic EL device is also affected by the higher-order structure resulting from the composition of the organic layer and intermolecular interactions, it is ideal for the mixed material of the present invention to be uniformly mixed inside the device. For this reason, in the present invention, it is preferable that the mixture is a pre-mixed state in which a first compound consisting of any compound selected from the group consisting of compounds represented by general formulas (1), (10), and (11) is pre-mixed with a second compound consisting of any compound selected from the group consisting of compounds represented by general formulas (2) to (7). By using a mixed material consisting of such a pre-mixed state, it is possible to deposit the film uniformly from a single deposition source during film formation, and a more uniform deposited film can be formed.

[0034] In this case, the glass transition temperature of at least one of the compounds constituting the first compound and the compounds constituting the second compound is preferably 100°C or higher, and preferably both compounds have a glass transition temperature of 100°C or higher. Furthermore, the melting point of at least one of these first and second compounds is preferably 220°C or higher, and preferably both compounds have a melting point of 220°C or higher. In addition, when the mixed material for the organic electroluminescent element in the present invention consists of a premixture, the glass transition temperature of the premixture is preferably 100°C or higher, and similarly, the melting point of this premixture is preferably 220°C or higher. For reasons to be described later, by having compounds that satisfy these conditions, when forming an organic film using a mixed material consisting of a premixture, segregation of the material before deposition (segregation of the first compound and the second compound) can be suppressed, and the mixed state after deposition can be prevented from becoming non-uniform.

[0035] Furthermore, as described above, in the mixing ratio of the organic electroluminescent element mixed material in the present invention, a ratio of 20% by mass or more and 80% by mass or less of the first compound makes it easier to balance holes and electrons. Therefore, in order to maintain this mixing ratio even after deposition, it is preferable that the difference (absolute difference) between the 50% weight loss temperature of the first compound and the 50% weight loss temperature of the second compound in the premixture be 20°C or less, and more preferably 15°C or less.

[0036] In this case, the 50% weight loss temperature is preferably 270°C or lower for both the first and second compounds, more preferably 265°C or lower, and even more preferably 260°C or lower. This makes it possible to suppress the temperature required for deposition. That is, by lowering the temperature of the deposition source, it is possible to prevent segregation of the mixed material consisting of the premixture and to suppress the decomposition of the mixed material due to heat. The lower limit of the 50% weight loss temperature is preferably 230°C or higher for both the first and second compounds, more preferably 235°C or higher, and even more preferably 240°C or higher. The method for measuring the 50% weight loss temperature is described later.

[0037] Here, the glass transition temperature of at least one of the first and second compounds is preferably 100 to 250°C, more preferably 105 to 225°C, and even more preferably 115 to 200°C. Furthermore, the melting point of at least one of the first and second compounds is preferably 220 to 350°C, more preferably 230 to 330°C, and even more preferably 240 to 310°C.

[0038] As described above, it is preferable that the mixed material comprising the premix according to the present invention has a 50% weight loss temperature of 230°C or higher for both the first compound and the second compound constituting it. This is to prevent the material from sublimating at an unintended time due to radiant heat and heat transfer generated when heating the deposition source of other materials with higher deposition temperatures within the deposition machine. When deposition of a material with a 50% weight loss temperature of 230°C or higher, heating to at least 200°C is required. Due to this heating during deposition, the material molecules of compounds with low melting points flow inside the deposition source before sublimation, causing segregation due to interactions between similar materials. For the same reason, in order to suppress this segregation, it is preferable that at least one of the first and second compounds constituting the mixed material comprising the premix has a melting point of 220°C or higher, and preferably both compounds have a melting point of 220°C or higher. Similarly, the first compound and the second compound constituting the mixed material, which are both composed of a premixture, preferably have a glass transition temperature of 100°C or higher for at least one of them, and more preferably have a glass transition temperature of 100°C or higher for both compounds. Furthermore, it is even better if the premixture composed of the first compound and the second compound has a glass transition temperature of 100°C or higher and a melting point of 220°C or higher.

[0039] Furthermore, in the present invention, the mixed material for the organic electroluminescent element, consisting of a premixture, may also contain a luminescent dopant in addition to the first and second compounds. This allows for the suitable formation of a light-emitting layer, as described later, to obtain an organic electroluminescent element (organic EL element).

[0040] Furthermore, the present invention relates to an organic electroluminescent element (organic EL element) comprising one or more organic layers between opposing anodes and cathodes, wherein at least one organic layer contains a mixed material for organic electroluminescent elements comprising the first compound described above and the second compound described above. Preferably, the organic electroluminescent element contains a mixed material for organic electroluminescent elements consisting of a pre-mixed (pre-mixed) premixture of the first compound and the second compound. The first compound and the second compound may be supplied to the organic layer individually, or they may be supplied as a mixed material for organic electroluminescent elements consisting of a pre-mixed (pre-mixed) premixture, as described above.

[0041] In the organic electroluminescent device of the present invention, the organic layer containing the mixed material for the organic electroluminescent device is the light-emitting layer, and it is preferable that the light-emitting layer contains a thermally activated delayed fluorescence light-emitting material. In this case, it is more preferable that the thermally activated delayed fluorescence material contains boron atoms.

[0042] Furthermore, in the organic electroluminescent device of the present invention, the organic layer containing the mixed material for the organic electroluminescent device is a light-emitting layer, and it is preferable that the light-emitting layer contains a phosphorescent material. In this case, it is more preferable that the phosphorescent material contains platinum atoms or iridium atoms.

[0043] Furthermore, in the organic electroluminescent device of the present invention, the organic layer containing the mixed material for the organic electroluminescent device is a light-emitting layer, and it is preferable that the light-emitting layer further contains a thermally activated delayed fluorescence light-emitting material containing boron atoms and a phosphorescent light-emitting material containing platinum atoms or iridium atoms.

[0044] Furthermore, in the organic electroluminescent device of the present invention, it is preferable that the organic layer containing the mixed material for the organic electroluminescent device is an emissive layer, and that the emissive layer contains the mixed material for the organic electroluminescent device as a host material, and further contains a thermally activated delayed fluorescence emissive material containing boron atoms and a phosphorescent emissive material containing platinum atoms or iridium atoms.

[0045] Furthermore, the present invention relates to a method for manufacturing an organic electroluminescent element having one or more organic layers between opposing anodes and cathodes, wherein at least one organic layer is a light-emitting layer, and when forming the light-emitting layer, a mixed material for organic electroluminescent elements consisting of a premixture in which the first compound and the second compound described above are premixed is used, and this is deposited from a single deposition source.

[0046] According to the present invention, it is possible to obtain an organic EL element that is practically useful, possessing long lifespan characteristics despite being driven at low voltage.

[0047] Figure 1 is a schematic cross-sectional view showing an example of the structure of an organic EL element used in the present invention.

[0048] The first and second compounds constituting the mixed material for the organic electroluminescent element in the present invention will be described in detail below.

[0049] First, the first compound constituting the mixed material for the organic electroluminescent element in the present invention consists of one or more compounds selected from the group consisting of compounds represented by general formulas (1), (10), and (11). These compounds represented by general formulas are as follows.

[0050]

[0051] In general formulas (1), (10), and (11), R １ R represents hydrogen, deuterium, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms. １ It is preferably hydrogen or deuterium, and more preferably deuterium. ２ ~R ７ Each of these independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of 2 to 3 such aromatic hydrocarbon groups linked together. ２ ~R ７It is preferably hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, more preferably hydrogen, deuterium, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and even more preferably hydrogen or deuterium. Furthermore, in the first compound consisting of any compound selected from the group consisting of compounds represented by general formulas (1), (10), and (11), at least one or all of the hydrogens in the compound are substituted with deuterium. That is, R １ ~R ７ This refers to hydrogen as defined by, or in which at least one or all of the hydrogens in the aliphatic hydrocarbon group, aromatic hydrocarbon group, or linked aromatic group representing these are substituted with deuterium.

[0052] Furthermore, the second compound constituting the mixed material for the organic electroluminescent element in the present invention consists of one or more compounds selected from the group consisting of compounds represented by general formulas (2) to (7). These compounds represented by general formulas are as follows.

[0053] In general formulas (2) to (7), R ８ ~R １７ Each of these independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of 2 to 3 such aromatic hydrocarbon groups linked together. ８ ~R １７ The first compound is preferably hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, more preferably hydrogen, deuterium, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and even more preferably hydrogen or deuterium. The second compound selected from the group consisting of compounds represented by general formulas (2) to (7) may have at least one or all of its hydrogen atoms replaced with deuterium. That is, R ８ ~R １７The hydrogen may be defined as such, or at least one or all of the hydrogens in the aliphatic hydrocarbon group, aromatic hydrocarbon group, or linked aromatic group representing these may be substituted with deuterium.

[0054] Here, the first compound, which consists of one or more compounds represented by the general formulas (1), (10), and (11), preferably has an average deuterated rate of 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more. Furthermore, the second compound, which consists of one or more compounds represented by the general formulas (2) to (7), preferably has at least one hydrogen or all of its hydrogens replaced by deuterium, and in this case, the second compound preferably has an average deuterated rate of 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more. Theoretically, the upper limit of the average deuterated rate is 100%. Preferably, both the first compound and the second compound are deuterated, and in that case, the average deuterated rate of both the first compound and the second compound should be 10% or more.

[0055] Furthermore, in calculating the average deuterated rate in the present invention, for example, the first compound includes both cases where the compound represented by general formula (1) consists of a single compound and cases where it consists of a mixture of two or more compounds represented by general formula (1). An average deuterated rate of 50% means that, on average, half of the total hydrogen in the compound represented by general formula (1) is replaced with deuterium. In other words, this includes not only the case where it consists of a single compound, but also the case where it consists of a mixture with different deuterated rates.

[0056] The average deuterated rate can be determined by mass spectrometry or proton nuclear magnetic resonance spectroscopy. For example, when determining the rate by proton nuclear magnetic resonance spectroscopy, first, a sample is prepared by adding the compound and an internal standard substance to a deuterated solvent and dissolving them. The proton concentration [mol / g] of the compound contained in the sample is then calculated from the ratio of the integrated intensity derived from the internal standard substance and the compound. Next, the ratio of the proton concentration of the deuterated compound to the corresponding proton concentration of the non-deuterated compound is calculated, and the average deuterated rate of the deuterated compound can be calculated by subtracting this ratio from 1. The average deuterated rate of a substructure can also be calculated from the integrated intensity of the chemical shift derived from the substructure in question using the same procedure as described above.

[0057] The first compound, which consists of any of the compounds represented by the general formulas (1), (10), and (11), is preferably any of the compounds represented by the following general formulas (1a) to (1g), (10a), (10b), and (11a) to (11c), and more preferably any of the compounds represented by (1b) to (1g), (10b), and (11b) to (11c). The first compound selected from the group consisting of compounds represented by these general formulas (1a) to (1g), (10a), (10b), and (11a) to (11c) is one in which at least one or all of the hydrogens in the compound are substituted with deuterium.

[0058] Furthermore, the second compound, which consists of any of the compounds represented by the general formulas (2) to (7), is preferably any of the compounds represented by the following general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a). A second compound selected from the group consisting of compounds represented by these general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a) may have at least one or all of its hydrogen atoms replaced by deuterium.

[0059] The first compound and the second compound can be combined as appropriate. For example, a preferred combination is (i) a first compound consisting of a compound represented by general formula (1) and a second compound consisting of any compound selected from the group consisting of compounds represented by general formulas (2), (3), (4), and (5). Similarly, (ii) a first compound consisting of any compound selected from the group consisting of compounds represented by general formulas (10) and (11) and a second compound consisting of a compound represented by general formula (6). More preferably, (iii) a first compound consisting of any compound selected from the group consisting of compounds represented by general formulas (1a) to (1g) and a second compound consisting of any compound selected from the group consisting of compounds represented by general formulas (2a), (2b), (3a), (3b), (4a), and (5a). Similarly, [iv] the case in which a first compound consists of any compound selected from the group consisting of compounds represented by general formulas (10a), (10b), (11a) to (11c), and a second compound consists of a compound represented by general formula (6a).

[0060] Here, as described above, the average deuterated rate of the first compound is preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more. Furthermore, it is preferable that at least one or more hydrogens or all of the hydrogens in the second compound are replaced with deuterium, in which case the average deuterated rate of the second compound is preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, even more preferably 70% or more, and most preferably 80% or more.

[0061] Furthermore, when the first compound consists of a compound represented by the general formula (1), it is preferable that it be one of the following (1-1) to (1-16). Similarly, when the first compound consists of a compound represented by the general formula (10), it is preferable that it is one of the following (10-1). Moreover, when the first compound consists of a compound represented by the general formula (11), it is preferable that it is one of the following (11-1) or (11-2). Note that D represents deuterium, and n means the average number of substitutions by deuterium in each of the above compounds, and changes according to the average deuteration rate.

[0062]

[0063] On the other hand, when the second compound consists of the compound represented by the general formula (2), it is preferable that it be one of the following (2-1) to (2-4). Furthermore, when the second compound consists of the compound represented by the general formula (3), it is preferable that it be one of the following (3-1) to (3-6) or (3-14). Furthermore, when the second compound consists of the compound represented by the general formula (4), it is preferable that it be one of the following (4-1). Furthermore, when the second compound consists of the compound represented by the general formula (5), it is preferable that it be one of the following (5-1). Moreover, when the second compound consists of the compound represented by the general formula (6), it is preferable that it be one of the following (6-1). Furthermore, when the second compound consists of the compound represented by the general formula (7), it is preferable that it be one of the following (7-1). Note that D represents deuterium, and n means the average number of substitutions by deuterium in each of the above compounds, and changes according to the average deuteration rate.

[0064]

[0065] Here, in the above general formulas (1), (10), and (11) representing the first compound, the R １Specific examples of groups where the group has 1 to 10 carbon atoms include methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, and decyl. Preferably, the group is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, or octyl. Preferably, the group is methyl, butyl, or octyl.

[0066] Also, in the same general formulas (1), (10), and (11) above, the R ２ ~R １７ A specific example of the case where is an unsubstituted aliphatic hydrocarbon group having 1 to 10 carbon atoms is the aforementioned R. １ This is similar to the specific example where is an unsubstituted aliphatic hydrocarbon group having 1 to 10 carbon atoms.

[0067] Similarly, in the above general formulas (1), (10), and (11), the R ２ ~R １７ Specific examples of groups where is an unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or an unsubstituted linked aromatic group formed by the linking of 2 to 3 such aromatic groups, include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, or groups formed by removing one hydrogen atom from groups formed by the linking of 2 to 3 of these groups. Preferably, it is benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, or groups formed by removing one hydrogen atom from groups formed by the linking of 2 to 3 of these groups.

[0068] In this specification, unsubstituted aromatic hydrocarbon groups or linked aromatic groups may each have substituents. When substituents are present, preferred substituents are deuterium, halogens, C1-C10 alkyl groups, C2-C5 alkenyl groups, C1-C5 alkoxy groups, or C12-C44 diarylamino groups. The number of substituents is preferably 0-5, more preferably 0-2. Note that when calculating the carbon number of an aromatic hydrocarbon group or linked aromatic group with substituents, the carbon numbers of the substituents are not included. However, it is preferable that the total carbon number including the carbon numbers of the substituents satisfies the above range.

[0069] Specific examples of the substituents include deuterium, bromo, fluorine, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenylenylamino, dipyrenylamino, etc. Preferably, deuterium, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, and pentoxy are used.

[0070] In this specification, a linked aromatic group refers to an aromatic group in which two or more aromatic rings are linked by a single bond. These linked aromatic groups may be linear or branched. The linking positions of the benzene rings may be ortho, meta, or para. The aromatic groups may be aromatic hydrocarbon groups, and the multiple aromatic groups may be the same or different.

[0071] The mixed material for organic electroluminescent devices in the present invention includes a first compound consisting of one or more compounds selected from the group consisting of compounds represented by the general formulas (1), (10), and (11), and a second compound consisting of one or more compounds selected from the group consisting of compounds represented by the general formulas (2) to (7). These compounds may each be in the form of a powder, a solid, or a thin film. For example, when forming the light-emitting layer of an organic EL element using this mixed material for organic electroluminescent devices, the first compound and the second compound may be supplied to the light-emitting layer individually, or they may be supplied as a mixed material for organic electroluminescent devices consisting of a premix of the first compound and the second compound. In particular, when forming the organic layer in an organic EL element, which will be described later, that is, an organic EL element that includes one or more organic layers between opposing anodes and cathodes, it is preferable to supply the mixed material for organic electroluminescent devices consisting of a premix of the first compound and the second compound, and to form the organic layer.

[0072] Furthermore, the mixed material for organic electroluminescent devices in the present invention may be prepared by mixing the first compound and the second compound in powder form, by melting and mixing them by heating under reduced pressure or inert gas atmosphere such as nitrogen, or by sublimating the compounds together. It may also be prepared as a thin film by vapor deposition or the like. On the other hand, if the first compound and the second compound constituting the mixed material for organic electroluminescent devices are not pre-mixed, they may be included in different organic layers of the device. For example, the first compound may be included in the electron blocking layer and the second compound in the light-emitting layer, so that they are included in different organic layers but share the same component as the device. As mentioned above, the mixed material for organic electroluminescent devices consisting of a pre-mixture means that the first compound and the second compound have been pre-mixed, and means of mixing include mixing them in powder form, heating and melting these powders, and sublimation for pre-mixing.

[0073] Here, in the mixed material for organic electroluminescent devices consisting of a premixture, it is preferable that the difference (absolute difference) between the 50% weight loss temperature of the first compound and the 50% weight loss temperature of the second compound is 20°C or less, and more preferably that the difference in 50% weight loss temperatures is 15°C or less. Furthermore, it is preferable that both the 50% weight loss temperature of the first compound and the 50% weight loss temperature of the second compound are 230 to 270°C, more preferably 235 to 265°C, and even more preferably 240 to 260°C or less. Moreover, it is preferable that at least one of the first compound and the second compound constituting the premixture, preferably both compounds, has a glass transition temperature of 100 to 250°C, more preferably 105 to 225°C, and even more preferably 115 to 200°C. Furthermore, at least one of the first and second compounds constituting the premixture, preferably both compounds, preferably have a melting point of 220 to 350°C, more preferably 230 to 330°C, and even more preferably 240 to 310°C. The melting point can be measured using widely known devices such as a melting point analyzer, a differential thermal / thermogravimetric analyzer (Tg-DTA), or a differential scanning calorimetry (DSC) analyzer. The glass transition temperature can also be measured using a DSC analyzer.

[0074] Furthermore, in the mixed material for organic electroluminescent devices in the present invention, the proportion of the first compound is preferably 20% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, even more preferably 40% by mass or more and 70% by mass or less, and most preferably 50% by mass or more and 70% by mass or less, relative to the total amount of the first compound and the second compound.

[0075] The following are specific examples of the general formulas (1), (10), and (11) that constitute the first compound, but the present invention is not limited to these exemplary compounds. Note that D represents deuterium, and the number of substitutions n represents the average number, which changes depending on the average deuteration rate.

[0076]

[0077] Furthermore, specific examples of compounds represented by general formulas (2) to (7) that constitute the second compound are shown below, but the present invention is not limited to these exemplary compounds. Note that D represents deuterium, and the number of substitutions n represents the average number, which changes depending on the average deuterated rate.

[0078]

[0079] Furthermore, the present invention relates to an organic electroluminescent element comprising one or more organic layers between opposing anodes and cathodes, wherein at least one organic layer contains a mixed material for organic electroluminescent elements comprising the first compound and the second compound. The first compound is preferably represented by the general formulas (1a) to (1g), (10a), (10b), or (11a) to (11c). The second compound is preferably represented by the general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), or (7a). In this case, it is preferable that the mixed material for organic electroluminescent elements contained in the organic layer is an organic electroluminescent element containing a premixture in which the first compound and the second compound are mixed beforehand.

[0080] The organic electroluminescent device of the present invention preferably has at least one organic layer as an emissive layer, and preferably contains a mixed material for organic electroluminescent devices consisting of a premixture according to the present invention in the emissive layer. More preferably, the organic electroluminescent device further contains a thermally activated delayed fluorescence material or a phosphorescent material in the emissive layer, and even more preferably, the organic electroluminescent device further contains a thermally activated delayed fluorescence material and a phosphorescent material in the emissive layer. Here, the thermally activated delayed fluorescence material preferably contains boron atoms, and the phosphorescent material preferably contains platinum atoms or iridium atoms.

[0081] In other words, an excellent organic EL element can be obtained by including a host material together with a thermally activated delayed fluorescence emitting material or a phosphorescent emitting material in the light-emitting layer as needed. However, it is preferable to use the mixed material for organic electroluminescent elements according to the present invention as the host material, and more preferably, to use the mixed material for organic electroluminescent elements consisting of a premixture. In that case, it is preferable that the first compound becomes a hole-transporting host material, and the second compound becomes an electron-transporting host material.

[0082] Furthermore, in the present invention, in an organic electroluminescent element containing one or more organic layers between opposing anodes and cathodes, at least one organic layer is a light-emitting layer, and in manufacturing the organic electroluminescent element containing the light-emitting layer, it is preferable to manufacture the organic electroluminescent element by using a mixed material for organic electroluminescent elements consisting of a premixture obtained by premixing the first compound and the second compound, and depositing this mixture from a single deposition source to form the light-emitting layer.

[0083] A preferred method is to use the first compound and the second compound, both powdered and pre-mixed, or to use a pre-mixed mixture of these powders obtained by heating and melting, to create a mixed material for organic electroluminescent devices, and then deposit it from a single deposition source to produce the light-emitting layer of the organic EL device.

[0084] Furthermore, in the present invention, the mixed material for the organic electroluminescent element, consisting of a premixture, may also contain a luminescent dopant in addition to the first and second compounds mentioned above. This allows for the suitable formation of a light-emitting layer and the acquisition of an organic electroluminescent element (organic EL element). The luminescent dopant referred to here may be one of those described later (luminescent dopant materials) as appropriate.

[0085] 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 thereto.

[0086] Figure 1 is a cross-sectional view showing an example of the structure of a typical organic EL element used in the present invention, where 1 is the substrate, 2 is the anode, 3 is the hole injection layer, 4 is the hole transport layer, 5 is the light-emitting layer, 6 is the electron transport layer, and 7 is the cathode. The organic EL element of the present invention has an anode, a light-emitting layer, and a cathode as essential layers, but it is common to 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 furthermore, an electron blocking layer may be included between the hole transport layer and the light-emitting layer, and a hole blocking layer may be included between the light-emitting layer and the electron transport layer.

[0087] It is also possible to stack the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, hole injection layer 3, and anode 2 on the substrate 1 in the reverse order of Figure 1, and in this case as well, layers can be added or omitted as needed. In organic EL elements as described above, layers that constitute the stacked structure on the substrate other than electrodes such as anodes and cathodes are sometimes collectively called organic layers. Examples of organic layers include hole injection layers, hole transport layers, light-emitting layers, electron transport layers, electron injection layers, electron blocking layers, and hole blocking layers.

[0088] -Substrate- The organic EL element of the present invention is preferably supported on a substrate. There are no particular restrictions on the substrate; any substrate that has been conventionally used in organic EL elements is acceptable, such as those made of glass, transparent plastic, quartz, etc.

[0089] - Anode - As the anode material for an organic EL device, materials consisting of metals, alloys, electrically conductive compounds, or mixtures thereof with a large work function (4 eV or more) are preferably used. Specific examples of such electrode materials include metals such as Au, CuI, indium tin oxide (ITO), and SnO ２ Examples include conductive transparent materials such as ZnO. Alternatively, amorphous materials capable of producing transparent conductive films, such as IDIXO (In2O3-ZnO), may be used. The anode may be formed by creating a thin film from these electrode materials using methods such as vapor deposition or sputtering, and then forming a pattern of the desired shape using photolithography. Alternatively, if high pattern accuracy is not required (approximately 100 μm or more), the pattern may be formed via a mask of the desired shape during vapor deposition or sputtering of the electrode material. In the case of coating-applicable materials such as organic conductive compounds, wet film formation methods such as printing or coating can also be used. When extracting light from this anode, it is desirable to have a transmittance greater than 10%, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

[0090] - Cathode - On the other hand, materials consisting of metals (called electron-injection metals), alloys, electrically conductive compounds, or mixtures thereof with a small work function (4 eV or less) are used as cathode materials. 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, aluminum / aluminum oxide (Al ２ O ３ Examples include mixtures, indium, lithium / aluminum mixtures, and rare earth metals. Among these, from the standpoint of electron injection properties and durability against oxidation, mixtures of electron-injectable metals and metallic compounds that have a larger work function and are more stable, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, and aluminum / aluminum oxide (Al ２ O ３Suitable materials include mixtures, lithium / aluminum mixtures, and aluminum. The cathode can be fabricated by forming a thin film of these cathode materials by methods such as vapor deposition or sputtering. The sheet resistance of the cathode is preferably 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. It is advantageous that the luminescence brightness is improved if either the anode or cathode of the organic EL element is transparent or semi-transparent in order to transmit the emitted light.

[0091] Furthermore, by forming the above-mentioned metal on the cathode with a film thickness of 1 to 20 nm, and then forming the conductive transparent material mentioned in the description of the anode on top of it, a transparent or translucent cathode can be fabricated. By applying this, it is possible to fabricate an element in which both the anode and cathode are transparent.

[0092] -Emitting Layer- The emissive layer is a layer that emits light after excitons are generated by the recombination of holes and electrons injected from the anode and cathode, respectively. The emissive layer may be a single layer or multiple layers, each containing an organic luminescent dopant material and a host material.

[0093] The organic luminescent dopant may be contained in the luminescent layer by one type or by two or more types. The content of the organic luminescent dopant is preferably 0.1 to 50% by mass, and more preferably 0.1 to 40% by mass, relative to the host material.

[0094] When using a phosphorescent dopant as an organic luminescent dopant material, the phosphorescent dopant should contain an organometallic complex comprising at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. More preferably, an organometallic complex containing platinum is used. Specifically, iridium complexes described in J.Am.Chem.Soc.2001,123,4304 and JP 2013-530515, and platinum complexes described in Adv. Mater.2014,26,7116 and JP 2018-2722 are suitably used, but are not limited to these.

[0095] Phosphorescent dopant materials are not particularly limited, but specific examples include the following:

[0096]

[0097] When using a fluorescent dopant as a luminescent dopant material, the fluorescent dopant is not particularly limited, but examples include condensed polycyclic aromatic derivatives, styrylamine derivatives, condensed ring amine derivatives, boron-containing compounds, pyrrole derivatives, indole derivatives, and carbazole derivatives. Among these, condensed ring amine derivatives, boron-containing compound derivatives, and carbazole derivatives are preferred. Examples of condensed ring amine derivatives include diaminepyrene derivatives, diaminochrysene derivatives, diaminoanthracene derivatives, diaminofluorenone derivatives, and diaminofluorene derivatives having one or more benzoflo skeletons fused together. Examples of boron-containing compounds include pyromethene derivatives and polycyclic aromatic compounds described in publication WO2015 / 102118, etc.

[0098] Fluorescent dopant materials are not particularly limited, but specific examples include the following:

[0099] When using a thermally activated delayed fluorescence dopant as a luminescent dopant material, the thermally activated delayed fluorescence dopant is not particularly limited, but examples 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 publication WO2015 / 102118, etc. Preferably, it is a thermally activated delayed fluorescence dopant containing a boron atom.

[0100] The thermally activated delayed fluorescence dopant material is not particularly limited, but specific examples include the following. A cyclic azine compound may be used as the thermally activated delayed fluorescence dopant material, but it is preferable that it is not a compound represented by the general formulas (2) to (7) above.

[0101] As the host material in the light-emitting layer, it is preferable to use a mixed material for organic electroluminescent devices that includes a first compound consisting of one or more compounds selected from the group consisting of compounds represented by the general formulas (1), (10), and (11), in particular a first compound consisting of one or more compounds selected from the group consisting of compounds represented by the general formulas (1a) to (1g), (10a), (10b), and (11a) to (11c), and a second compound consisting of one or more compounds selected from the group consisting of compounds represented by the general formulas (2) to (7), in particular a second compound consisting of one or more compounds selected from the group consisting of compounds represented by the general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a). When such a mixed material for organic electroluminescent devices containing the first compound and the second compound is used in any organic layer other than the light-emitting layer, the first compound and the second compound may or may not be included in the light-emitting layer. In this case, known host materials used in phosphorescent and fluorescent light-emitting devices can also be used in combination with the light-emitting layer. Multiple known host materials may be used in combination, or each may be used individually. Suitable known host materials are compounds that possess hole transport ability, electron transport ability, and a high glass transition temperature, and preferably have a triplet excitation energy (T1(h)) greater than the triplet excitation energy (T1(exp)) of the luminescent dopant material. Furthermore, delayed fluorescence (TADF) active compounds may be used as the host material; in this case, compounds with a difference between the singlet excitation energy (S1(h)) and the triplet excitation energy (T1(h)) (ΔEST = S1(h) - T1(h)) of 0.20 eV or less are preferred. Multiple known host materials may be used in combination.

[0102] Here, S1(h), T1(h), and ΔEST = S1(h) - T1(h) can be measured as follows: Vacuum deposition on a quartz substrate at a vacuum level of 10 －４ A sample compound (a compound exhibiting delayed fluorescence (TADF) activity) is deposited under conditions below Pa, forming a deposited film with a thickness of 100 nm. S1(h) is calculated by measuring the emission spectrum of this deposited film, drawing a tangent to the rising edge of the short-wavelength side of the emission spectrum, and substituting the wavelength value λedge [nm] at the intersection of this tangent and the horizontal axis into the following equation (i): S1(h) [eV] = 1239.85 / λedge (i)

[0103] On the other hand, T1(h) is calculated by measuring the phosphorescence spectrum of the deposited film, drawing a tangent to the rising edge on the short-wavelength side of the phosphorescence spectrum, and substituting the wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis into the following equation (ii): T1(h) [eV] = 1239.85 / λedge (ii) From the above, S1(h) and ΔEST can be determined.

[0104] The known host materials can be selected from those known through numerous patent documents, etc. Specific examples of host materials are not 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 and metal phthalocyanines, various metal complexes represented by metal complexes of benzoxazole and benzothiazole compounds, poly(N-vinylcarbazole) compounds, aniline copolymers, thiophene oligomers, polythiophene compounds, polyphenylene compounds, polyphenylene vinylene compounds, polyfluorene compounds, and other polymer compounds. Preferably, examples include carbazole compounds, indrocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, anthracene compounds, triphenylene compounds, carborane compounds, and porphyrin compounds.

[0105] The known hosts mentioned above are not limited to the following compounds.

[0106] When using multiple types of hosts, each host can be deposited from a different deposition source, or multiple types of hosts can be pre-mixed and deposited simultaneously from a single deposition source.

[0107] When multiple types of hosts are used, the host is preferably a mixed material for an organic electroluminescent device containing the first compound and the second compound. More preferably, the mixed material for an organic electroluminescent device is made of a pre-mixed premixture of these compounds. In this case, as mentioned above, the first compound is preferably a hole-transporting host material, and the second compound is preferably an electron-transporting host material.

[0108] In order to reproducibly fabricate organic EL elements with good characteristics, the mixed material for organic electroluminescent elements and the mixed material for organic electroluminescent elements consisting of the premixture are configured such that the 50% weight loss temperature (T) of the first host and the second host is specified. 50 It is desirable that the difference (absolute difference) between the first and second hosts be small, preferably the difference in the 50% weight loss temperature is within 20°C, and more preferably within 15°C. The 50% weight loss temperature is the temperature at which the weight decreases by 50% when the temperature is raised from room temperature to 550°C at a rate of 10°C per minute in a TG-DTA measurement under reduced pressure of nitrogen flow (1 Pa). Around this temperature, vaporization by evaporation or sublimation is considered to occur most actively. If the difference in the 50% weight loss temperature between the first host and the second host is within 20°C, it is possible to obtain a uniform deposited film by vaporizing and depositing from a single evaporation source. In this case, the mixed material for the organic electroluminescent element may contain, in addition to the first and second compounds, a luminescent dopant material necessary for forming the light-emitting layer, or the known host used as needed. However, if there is a large difference in the temperature at which the desired vapor pressure is reached, it is preferable to deposit from a different deposition source.

[0109] Furthermore, when two types of host materials are used, including a first compound and a second compound, the mixing ratio (mass ratio) of these materials is preferably such that the proportion of the first compound is 20% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, even more preferably 40% by mass or more and 70% by mass or less, and most preferably 50% by mass or more and 70% by mass or less, relative to the total of the first compound and the second compound.

[0110] When using multiple types of host materials, a method that allows for as uniform a mixture as possible is desirable for pre-mixing the host materials. Examples of such methods include grinding and mixing, heating and melting under reduced pressure or inert gas atmosphere such as nitrogen, and sublimation, but the method is not limited to these.

[0111] Furthermore, the host material, including the case of a mixed material consisting of the mixed material according to the present invention or a pre-mixed premixture, may be in the form of a powder, a stick, or granules.

[0112] -Injection Layer- An injection layer is a layer provided between the electrode and the organic layer to reduce the driving voltage and improve the luminescence brightness. There are hole injection layers and electron injection layers, and they may be present between the anode and the light-emitting layer or hole transport layer, and between the cathode and the light-emitting layer or electron transport layer. The injection layer can be provided as needed.

[0113] -Hole Blocking Layer- In a broad sense, the hole blocking layer functions as an electron transport layer. It consists of a hole-blocking material that has the ability to transport electrons while having a significantly low ability to transport holes. By blocking holes while transporting electrons, it is possible to improve the probability of electron-hole recombination in the light-emitting layer. Known hole-blocking materials can be used for the hole blocking layer. In addition, multiple types of hole-blocking materials may be used in combination.

[0114] -Electron Blocking Layer- In a broad sense, the electron blocking layer functions as a hole transport layer, and by blocking electrons while transporting holes, it can improve the probability of electrons and holes recombining in the light-emitting layer. Preferably, the mixed material for organic electroluminescent devices according to the present invention can be used as the material for the electron blocking layer, but known electron blocking layer materials can also be used. When the mixed material for organic electroluminescent devices according to the present invention is used for the electron blocking layer, the mixed material for organic electroluminescent devices according to the present invention may also be used as the host material in the light-emitting layer.

[0115] Layers adjacent to the light-emitting layer include hole blocking layers and electron blocking layers. However, if these layers cannot be provided, hole transport layers and electron transport layers become the adjacent layers.

[0116] - Hole Transport Layer - The hole transport layer consists of a hole transport material that has the function of transporting holes, and the hole transport layer can be a single layer or multiple layers.

[0117] The hole transport material has either hole injection or transport, or electron barrier properties, and may be either organic or inorganic. Any compound from conventionally known compounds can be selected and used as the hole transport material. Examples of such hole transport materials include porphyrin derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, aminosubstituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

[0118] - Electron Transport Layer - The electron transport layer consists of a material that has the function of transporting electrons, and the electron transport layer can be a single layer or multiple layers.

[0119] The electron transport material (which may also serve as a hole-blocking material) only needs to have the function of transferring electrons injected from the cathode to the light-emitting layer. Any compound from conventionally known compounds can be selected and used for the electron transport layer. Examples include polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline; tris(8-quinolinolate)aluminum(III) derivatives; phosphine oxide derivatives; nitro-substituted fluorene derivatives; diphenylquinone derivatives; thiopyrandioxide derivatives; carbodiimide; fluorenylidene methane derivatives; anthraquinodimethane and anthrone derivatives; bipyridine derivatives; quinoline derivatives; oxadiazole derivatives; benzimidazole derivatives; benzothiazole derivatives; and indolocarbazole derivatives. Furthermore, polymer materials can be used in which these materials are incorporated into polymer chains, or in which these materials are used as the main chain of the polymer.

[0120] The method for fabricating each layer of the organic EL element of the present invention is not particularly limited, and may be fabricated using either a dry process or a wet process.

[0121] The present invention will be described in more detail below based on examples using a mixed material containing the first compound and the second compound, but the present invention is not limited to these examples.

[0122] Calculation Example: Calculation of HOMO and LUMO Values ​​For compounds 1-8, 1-10, 1-14, 1-15, 10-1, 11-1, 11-2, 2-1, 3-1, 3-14, 4-1, 5-1, and 6-1, HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) were calculated. Similarly, calculations were performed for HH-5 and EH-1. The calculations were performed using density functional theory (DFT), with Gaussian as the calculation program, and the density functional calculation B3LYP / 6-31G(d) was used for structural optimization. The results are shown in Table 1 below. The first compound according to the present invention exhibits a low HOMO rank of -5.0 eV or less, while the second compound exhibits a LUMO rank of -2.1 eV or higher and a HOMO rank of -5.6 eV or higher. Thus, it can be said that these compounds have desirable HOMO and LUMO values ​​that allow for appropriate control of the amount of charge within a predetermined organic layer, such as a light-emitting layer.

[0123]

[0124] The following are representative examples of the synthesis of compounds 1-10, 1-14, and 2-1. Other compounds were synthesized using similar methods. The average deuterated rate was determined by proton nuclear magnetic resonance spectroscopy. In the formulas, Dn indicates that, independently for each compound, some or all of the hydrogen atoms in the compound are deuterated.

[0125] Synthesis Example 1 (Synthesis of Compounds 1-10) In a 200 mL three-necked flask purged with degassed nitrogen, 30.0 g of compound (a), 37.1 g of compound (b), 38.6 g of potassium carbonate, 8.9 g of copper iodide, 2.5 g of 18-crown-6-ether, and 300 mL of 1,3-dimethyl-2-imidazolidinone were added and stirred at 190 °C for 10 hours under a nitrogen atmosphere. After cooling to room temperature, 500 mL of water and 50 mL of 2 M hydrochloric acid were added to precipitate the solid, which was then filtered off. The obtained solid was purified by crystallization to obtain 33.9 g of compound (c) as a white solid. The yield was 63%.

[0126] 28.5 g of compound (c) obtained above, 300 mL of deuterated benzene (C6D6), and 14.9 g of trifluoromethanesulfonic acid (TfOH) were added to a 500 mL three-necked flask that had been degassed and purged with nitrogen. The mixture was heated and stirred at 60°C for 3 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction mixture was added to 59 mL of a heavy aqueous solution of potassium carbonate (15.1 g) in an ice bath. The reaction mixture was transferred to a separatory funnel and fractionated into an organic layer and an aqueous layer. The aqueous layer was extracted twice with 200 mL of dichloromethane, and the resulting organic layer was concentrated under reduced pressure. The resulting residue was purified by crystallization to obtain 22.8 g of compound (1-10) (white solid) (average deuterated rate 89%). The yield was 80%.

[0127] Synthesis Example 2 (Synthesis of Compounds 1-14) 21.0 g of compound (d), 8.7 g of compound (e), 17.9 g of potassium carbonate, 4.1 g of copper iodide, 1.1 g of 18-crown-6-ether, and 230 mL of 1,3-dimethyl-2-imidazolidinone were added to a 200 mL three-necked flask that had been degassed and purged with nitrogen. The mixture was stirred at 180 °C for 22 hours under a nitrogen atmosphere. After cooling to room temperature, 200 mL of water was added, and the mixture was extracted with dichloromethane and washed three times with water. The organic layer was concentrated under reduced pressure, and the resulting solid was purified by silica gel column chromatography to obtain 19.4 g of compound (f) as a white solid. The yield was 79%.

[0128] Add 18.1 g of the compound (f) obtained above to a 500 mL three-necked flask that has been degassed and purged with nitrogen, and deuterated benzene (C ６ D ６190 mL of ) and 23.7 g of trifluoromethanesulfonic acid (TfOH) were added, and the mixture was heated and stirred at 60°C for 3 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction mixture was added to 160 mL of heavy aqueous solution of sodium carbonate (18.4 g) in an ice bath. The reaction mixture was transferred to a separatory funnel and fractionated into an organic layer and an aqueous layer. The aqueous layer was extracted twice with 50 mL of dichloromethane, and the resulting organic layer was concentrated under reduced pressure. The resulting residue was purified by column chromatography to obtain 15.1 g of compound (1-14) (white solid) (average deuteration rate 86%). The yield was 83%.

[0129] Synthesis Example 3 (Synthesis of Compound 2-1) 5.0 g of compound (g), 8.6 g of compound (h), 1.0 g of tetrakis(triphenylphosphine)palladium(0), and 4.7 g of potassium carbonate were placed in a 300 mL three-necked flask that had been purged with deaerated nitrogen. 240 mL of toluene, 20 mL of ethanol, and 20 mL of water were added, and the mixture was stirred at 100°C for 24 hours. After cooling to room temperature, 100 mL of water was added, and the mixture was transferred to a separatory funnel to separate the organic layer from the aqueous layer. The resulting oil layer was filtered through activated clay and then dried under reduced pressure. Crystallization was performed on the resulting residue to obtain 10.6 g of compound (2-1) (white solid) (average deuterated rate 95%). The yield was 90%.

[0130] The average deuterated rates of the compounds used in the examples and comparative examples are shown in Table 2 below. The average deuterated rate indicates the proportion of hydrogen contained in the compound that has been deuterated, and was determined by mass spectrometry or proton nuclear magnetic resonance spectroscopy. As a representative example, the method for determining the average deuterated rate of compounds (1-8) by proton nuclear magnetic resonance spectroscopy is shown below.

[0131] First, a sample was prepared by dissolving compound (1-8) (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 (1-8) contained in the sample was calculated from the integrated intensity ratio derived from the internal standard and compound (1-8). Similarly, the average proton concentration [mol / g] of the non-deuterated form of compound (1-8) (EH6) was also calculated. Next, the ratio of the proton concentration of compound (1-8) to the proton concentration of the non-deuterated form of compound (1-8) was calculated and subtracted from 1 to determine the average deuterated rate of compound (1-8). The average deuterated rate was determined in the same manner for other compounds used in the examples and comparative examples. The results are shown in Table 2.

[0132]

[0133] The compounds used in the examples and comparative examples are shown below.

[0134] Example 1 A glass substrate on which an anode made of ITO with a thickness of 70 nm was formed was deposited with the following thin films by vacuum deposition at a vacuum of 4.0 × 10⁻⁶ －５The layers were laminated with Pa. First, the previously shown HAT-CN was formed on ITO to a thickness of 10 nm as a hole injection layer, and then HT-1 was formed to a thickness of 50 nm as a hole transport layer. Next, HT-2 was formed to a thickness of 5 nm as an electron blocking layer. Next, a compound corresponding to the first compound (1-8) was co-deposited from different deposition sources as the first host, a compound corresponding to the second compound (2-1) as the second host, BD-2 as a phosphorescent dopant, and BD-1 as a thermally activated delayed fluorescence dopant, to form an emissive layer with a thickness of 40 nm. At this time, the concentration of BD-2 was 13 mass%, the concentration of BD-1 was 0.4 mass%, and the co-deposit was carried out under deposition conditions in which the mass ratio of the first host to the second host in the mixed material containing the first and second hosts was 70:30. Next, ET-2 was formed to a thickness of 5 nm as a hole blocking layer. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed on the electron transport layer to a thickness of 1 nm as an electron injection layer. Finally, aluminum (Al) was formed on the electron injection layer to a thickness of 70 nm as a cathode, and the organic electroluminescent device according to Example 1 was fabricated.

[0135] Examples 2-9, 40-54, Comparative Examples 1-8, 10-12: Organic electroluminescent devices were fabricated in the same manner as in Example 1, except that the first and second hosts were the compounds shown in Tables 3 and 4, and the mixing ratio of the first and second hosts was the mixing ratio shown in these tables.

[0136] Examples 10-18, 55-69, and Comparative Examples 13-15: Organic EL elements were fabricated in the same manner as in Example 1, except that the compounds shown in Tables 3 and 4 were used as the first and second hosts, and a mixed material consisting of a preliminary mixture obtained by grinding and mixing these compounds in a mortar was deposited from a single evaporation source.

[0137]

[0138]

[0139] Tables 5 and 6 show the evaluation results of the fabricated organic electroluminescent devices. When an external power supply was connected and a DC voltage was applied to the organic electroluminescent devices obtained in Examples 1-18, 40-69 and Comparative Examples 1-8, 10-15, an emission spectrum with a maximum emission wavelength of 450 nm to 480 nm was observed in all organic electroluminescent devices, indicating that emission was obtained from BD-1 and BD-2. Here, the voltage in the table represents the drive current of 4.0 mA / cm. ２ This is the value in hours. The lifespan is based on a drive current of 4.0 mA / cm². ２ This represents the time it takes for the brightness to decrease from 100% to 97%, and indicates the device lifetime characteristics. The emitted color was confirmed by the emission spectrum of the organic electroluminescent element.

[0140] From the results of the examples and comparative examples shown in Tables 5 and 6, it can be seen that the organic electroluminescent device using the mixed material for organic electroluminescent devices of the present invention as a host in the light-emitting layer emits blue light, has good power efficiency, and is particularly long-lived.

[0141]

[0142]

[0143] Example 19 A glass substrate on which an anode made of ITO with a thickness of 70 nm was formed was deposited with the following thin films by vacuum deposition at a vacuum of 4.0 × 10⁻⁶ －５The layers were laminated with Pa. First, the previously shown HAT-CN was formed on ITO to a thickness of 10 nm as a hole injection layer, and then HT-1 was formed to a thickness of 50 nm as a hole transport layer. Next, HT-2 was formed to a thickness of 5 nm as an electron blocking layer. Next, a compound corresponding to the first compound (1-8) was co-deposited from different deposition sources as the first host, a compound corresponding to the second compound (2-1) as the second host, and BD-2 as a phosphorescent dopant, to form an emissive layer with a thickness of 40 nm. At this time, the concentration of BD-2 was 13 mass%, and the co-deposit conditions were such that the mass ratio of the first host to the second host in the mixed material containing the first and second hosts was 70:30. Next, ET-2 was formed to a thickness of 5 nm as a hole blocking layer. Next, ET-2 was formed to a thickness of 31 nm as an electron transport layer. Furthermore, lithium fluoride (LiF) was formed on the electron transport layer to a thickness of 1 nm as an electron injection layer. Finally, aluminum (Al) was formed on the electron injection layer to a thickness of 70 nm as a cathode, and the organic EL device according to Example 19 was fabricated.

[0144] Examples 20-27, 70-84, Comparative Examples 16-23, 25, and 26: Organic EL elements were fabricated in the same manner as in Example 19, except that the first and second hosts were compounds shown in Tables 7 and 8, and the mixing ratio of the first and second hosts was as shown in these tables.

[0145] In Examples 28-39, 85-99, and Comparative Examples 27 and 28, organic EL elements were fabricated in the same manner as in Example 19, except that the compounds shown in Tables 7 and 8 were used as the first and second hosts, and a mixed material consisting of a preliminary mixture obtained by grinding and mixing these compounds in a mortar was deposited from a single evaporation source.

[0146]

[0147]

[0148] The evaluation results of the fabricated organic EL elements are shown in Tables 9 and 10. The voltages in the tables represent the drive current of 4.0 mA / cm². ２ This is the value at time and represents the initial characteristics. Furthermore, the lifespan is based on a drive current of 4.0 mA / cm². ２This represents the time it takes for the brightness to decrease from 100% to 97%, and indicates the device's lifetime characteristics. The emitted color was confirmed by the emission spectrum of the organic EL element.

[0149]

[0150]

[0151] When an external power supply was connected to the organic electroluminescent devices obtained in Examples 19-39, 70-99 and Comparative Examples 16-23, 25-28 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 emission from BD-2 was obtained. Furthermore, from the results of these examples and comparative examples shown in Table 6, it can be seen 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 high efficiency and long lifespan characteristics.

[0152] The 50% weight loss temperature (T50) and glass transition temperature (Tg) of the compounds used in the examples and comparative examples described above are shown in Tables 11 and 12, respectively. The melting points (Tm) of some of these compounds are also shown in Table 13. Furthermore, the melting points (Tm) and glass transition temperatures (Tg) of the preliminary mixtures obtained by using the compounds shown in Table 14 as the first and second compounds and grinding them in a mortar are also shown.

[0153]

[0154]

[0155]

[0156]

[0157] 1: Substrate, 2: Anode, 3: Hole injection layer, 4: Hole transport layer, 5: Light-emitting layer, 6: Electron transport layer, 7: Cathode

Claims

A mixed material for an organic electroluminescent element, characterized in that it contains one or more compounds selected from the group consisting of compounds represented by the following general formulas (1), (10), and (11) as a first compound, and one or more compounds selected from the group consisting of compounds represented by the following general formulas (2) to (7) as a second compound. (Here, R １ R represents hydrogen, deuterium, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms. ２ ~R ７ Each of these independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of 2 to 3 such aromatic hydrocarbon groups linked together. Furthermore, the first compound selected from the group consisting of compounds represented by general formulas (1), (10), and (11) has at least one hydrogen atom or all of the hydrogen atoms in the compound substituted with deuterium. (Here, R ８ ~R １７ Each of these independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of 2 to 3 such aromatic hydrocarbon groups linked together. Note that in the second compound selected from the group consisting of compounds represented by general formulas (2) to (7), at least one or all of the hydrogen atoms in the compound may be substituted with deuterium. 　 The mixed material for an organic electroluminescent element according to claim 1, characterized in that the second compound selected from the group consisting of compounds represented by the general formulas (2) to (7) is such that at least one hydrogen or all of the hydrogens in the compound are replaced with deuterium. 　 The mixed material for an organic electroluminescent element according to claim 2, wherein the average deuterated rate of the first compound and the second compound is 10% or more. 　 The mixed material for an organic electroluminescent element according to claim 1, characterized in that it contains one or more compounds selected from the group consisting of compounds represented by the following general formulas (1a), (10a), and (11a) as a first compound, and one or more compounds selected from the group consisting of compounds represented by the following general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a) as a second compound. (The first compound selected from the group consisting of compounds represented by general formulas (1a), (10a), and (11a) is one in which at least one or all of the hydrogen atoms in the compound are replaced with deuterium.) (The second compound selected from the group consisting of compounds represented by general formulas (2a), (2b), (3a), (3b), (4a), (5a), (6a), and (7a) may have at least one hydrogen or all of the hydrogens in the compound substituted with deuterium.) 　 The mixed material for an organic electroluminescent element according to claim 1, characterized in that it contains one or more compounds selected from the group consisting of compounds represented by the following general formulas (1b) to (1g), (10b), (11b), and (11c) as a first compound, and one or more compounds selected from the group consisting of compounds represented by the general formulas (2) to (7) as a second compound. (The first compound selected from the group consisting of compounds represented by general formulas (1b) to (1g), (10b), (11b), and (11c) is one in which at least one or all of the hydrogen atoms in the compound are replaced with deuterium.) 　 The mixed material for an organic electroluminescent element according to claim 1, wherein the first compound consists of one or more compounds selected from the group consisting of compounds represented by (1-1) to (1-16), (10-1), (11-1), and (11-2) below, and the second compound consists of one or more compounds selected from the group consisting of compounds represented by (2-1) to (2-4), (3-1) to (3-6), (3-14), (4-1), (5-1), (6-1), and (7-1) below. (Here, D represents deuterium. Also, n represents the average number of deuterium substitutions in each compound, and changes depending on the average deuterated rate.) 　 The mixed material for an organic electroluminescent element according to claim 1, comprising a premixture in which the first compound and the second compound are premixed, and characterized in that the difference between the 50% weight loss temperature of the first compound and the 50% weight loss temperature of the second compound is 20°C or less. 　 The mixed material for an organic electroluminescent element according to claim 7, wherein the glass transition temperature of at least one of the first compound and the second compound constituting the premixture is 100°C or higher. 　 The mixed material for an organic electroluminescent element according to claim 7, wherein the 50% weight loss temperature of the first compound constituting the premixture and the 50% weight loss temperature of the second compound constituting the premixture are both 270°C or less. 　 The mixed material for an organic electroluminescent element according to claim 7, characterized in that at least one of the first compound constituting the premixture and the second compound constituting the premixture has a melting point of 220°C or higher. 　 The mixed material for an organic electroluminescent element according to claim 7, characterized in that the proportion of the first compound to the sum of the first compound constituting the premixture and the second compound constituting the premixture is 20% by mass or more and 80% by mass or less. 　 The mixed material for an organic electroluminescent element according to claim 7, characterized in that the premix further comprises a luminescent dopant in addition to the first compound and the second compound. 　 An organic electroluminescent element comprising one or more organic layers between opposing anodes and cathodes, characterized in that at least one organic layer contains the mixed material for organic electroluminescent elements described in claim 1. 　 The organic electroluminescent element according to claim 13, wherein the organic layer containing the mixed material for the organic electroluminescent element is an emissive layer, and the emissive layer further contains a thermally activated delayed fluorescence emissive material. 　 The organic electroluminescent element according to claim 14, characterized in that the thermally activated delayed fluorescence material is a thermally activated delayed fluorescence material containing boron atoms. 　 The organic electroluminescent element according to claim 13, wherein the organic layer containing the mixed material for organic electroluminescent elements is an emissive layer, and the emissive layer further contains a phosphorescent material. 　 The organic electroluminescent element according to claim 16, characterized in that the phosphorescent material is a phosphorescent material containing platinum atoms or iridium atoms. 　 A method for manufacturing an organic electroluminescent element having one or more organic layers between opposing anodes and cathodes, wherein at least one organic layer is a light-emitting layer, and when manufacturing the light-emitting layer, a mixed material for an organic electroluminescent element consisting of a pre-mixed premix as described in claim 7 is used, and the layer is deposited from a single deposition source.

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