Organic electroluminescent element mixed material and organic electroluminescent element

Abstract

Provided is an organic electroluminescent (EL) element mixed material with which it is possible to obtain an organic EL element of practical use and having high efficiency and long life while having a low driving voltage.　This organic EL element mixed material contains a compound represented by general formula (1) and a compound represented by general formula (2). The compound represented by general formula (1) is an indolocarbazole compound in which a substituted triazine ring is bonded to one N of an indolocarbazole ring, and there is a linked aromatic group at another N. The compound represented by general formula (2) is a biscarbazole compound in which an aromatic hydrocarbon group is substituted at an N of a carbazole ring and an oxygen atom is crosslinked.

Description

Mixed material for organic electroluminescent device and organic electroluminescent device

[0001] The present invention relates to a mixed material for organic electroluminescent devices and an organic electroluminescent device (referred to as an organic EL device) using the same. More specifically, the present invention relates to a mixed material for organic electroluminescent devices comprising an indolocarbazole compound and a biscarbazole compound bridged by oxygen atoms or sulfur atoms, and an organic EL device using the same.

[0002] When a voltage is applied to an organic electroluminescent device (referred to as an organic EL device), holes are injected from the anode and electrons are injected from the cathode into the light-emitting layer. The injected holes and electrons then recombine in the light-emitting layer, generating excitons. At this time, due to the statistical law of electron spin, singlet excitons and triplet excitons are generated in a ratio of 1:3. It is said that the internal quantum efficiency of fluorescent organic EL devices that use emission from singlet excitons is limited to 25%. On the other hand, it is known that the internal quantum efficiency of phosphorescent organic EL devices that use emission from triplet excitons can be increased to 100% if intersystem crossing from singlet excitons is efficiently achieved. However, extending the lifetime of phosphorescent organic EL devices remains a technical challenge.

[0003] More recently, highly efficient organic EL devices utilizing delayed fluorescence have been developed. For example, Patent Document 1 discloses an organic EL device utilizing the TTF (Triplet-Triplet Fusion) mechanism, one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon in which singlet excitons are generated by the collision of two triplet excitons, and is believed to theoretically achieve an internal quantum efficiency of up to 40%. However, its efficiency is lower than that of phosphorescent organic EL devices, and further efficiency improvements are needed. On the other hand, Patent Document 2 discloses an organic EL device utilizing the TADF (Thermally Activated Delayed Fluorescence) mechanism. The TADF mechanism utilizes the phenomenon in which reverse intersystem crossing occurs from triplet excitons to singlet excitons in materials with a small energy difference between the singlet and triplet levels, and is believed to theoretically achieve an internal quantum efficiency of up to 100%. However, as with phosphorescent devices, further improvements in lifetime characteristics are needed.

[0004] Here, Patent Document 3 discloses the use of an indolocarbazole compound as a host material, and Patent Documents 4 and 5 disclose the use of an oxygen-bridged biscarbazole compound as a host material.

[0005] Furthermore, Patent Documents 6 and 7 disclose the use of a mixed host of an indolocarbazole compound and a biscarbazole compound, and Patent Document 8 discloses the use of a deuterated carbazole compound as a host material.

[0006] Furthermore, Patent Document 9 discloses the use of a mixed material for organic electroluminescent devices, which is composed of a plurality of indolocarbazole compounds and an oxygen-bridged biscarbazole compound, as a host material.

[0007] However, conventionally known organic EL elements are not sufficient in terms of reducing the driving voltage of the element, improving the luminous efficiency, and extending the lifespan, and further improvements are desired.

[0008] WO2010 / 134350 WO2011 / 070963 WO2008 / 056746 WO2011 / 019173 A2WO2014 / 057684 A1US Patent Publication No. 2014 / 0197386 US Patent Publication No. 2015 / 0001488 KR102283849WO2018 / 043435

[0009] In order to apply organic EL elements to display elements such as flat panel displays, it is necessary to improve the luminous efficiency of the elements and at the same time ensure a sufficiently long life of the elements. In view of the above-mentioned current situation, an object of the present invention is to provide a practically useful organic EL element that has high efficiency and a long life while requiring a low driving voltage, and a compound suitable for the same.

[0010] As a result of intensive investigations, the present inventors have found that excellent properties can be exhibited by using a mixed material for an organic electroluminescent device, which is composed of a specific indolocarbazole compound and a bridged biscarbazole compound bridged with an oxygen atom or a sulfur atom, in an organic EL device, and have thus completed the present invention.

[0011] The present invention provides a mixed material for an organic electroluminescent device, which contains a compound represented by the following general formula (1) and a compound represented by the following general formula (2).

[0012] Here, ring A is a nitrogen-containing five-membered heterocycle represented by formula (1a) which is fused with two adjacent rings at any position. １ and Ar ２ are each independently hydrogen, deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different. Note that the benzene ring described in formula (1a) may have a substituent, and in that case, the substituent is the same as the substituent when substituted on the aromatic hydrocarbon group, aromatic heterocyclic group, and linked aromatic group.

[0013] R １are each independently deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different.

[0014] a to c represent the number of substitutions, and a and c are each independently an integer of 0 to 4, and b is an integer of 0 to 2, preferably a and c are each independently an integer of 0 to 2, and b is an integer of 0 to 1. ３ is deuterium, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked aromatic group in which 2 to 5 phenyl groups are linked together. n is the number of substitutions and is an integer of 0 to 4, preferably 0 or 1.

[0015]

[0016] where X is an oxygen atom or a sulfur atom, and Y １ ~Y １２ are each independently represented by C-Ra. １ and Z ２ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different.

[0017] Ra is hydrogen, deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms.

[0018] In the above general formula (1), the formula (1a) is represented by the following formula (3a), and Ar １ , and Ar ２are each independently hydrogen, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, or a substituted or unsubstituted quaterphenyl group. The benzene ring shown in the following formula (3a) may have a substituent, and in that case, the substituent is the same as the substituent when substituting an aromatic hydrocarbon group, an aromatic heterocyclic group, and a linking aromatic group.

[0019] Here, Ar ４ is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked aromatic group in which two phenyl groups are linked together. p is the number of substitutions and represents an integer of 0 to 2. q is the number of substitutions and represents an integer of 0 to 3, preferably 0 to 1.

[0020] Z in the general formula (2) １ and Z ２ are preferably the same as each other. １ and Z ２ When Y is a substituted or unsubstituted phenyl group, １ ~Y １２ In the formula (I), at least one Ra in C-Ra is preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms.

[0021] In the mixed material for organic electroluminescent elements of the present invention, it is preferable that the ratio of the compound represented by general formula (1) is 20% by mass or more and 70% by mass or less with respect to the total of the compound represented by general formula (1) and the compound represented by general formula (2).

[0022] In the mixed material for organic electroluminescent elements of the present invention, it is preferable that at least one of the compounds represented by the general formula (1) and the compounds represented by the general formula (2) has some or all of its hydrogen atoms substituted with deuterium atoms.

[0023] The mixed material for organic electroluminescent devices is a material for manufacturing at least one layer of an organic electroluminescent device having a plurality of organic layers between an anode and a cathode by a vapor deposition method, and can be a premix prepared before vapor deposition. In this premix, the difference in 50% weight loss temperature between the compound represented by general formula (1) and the compound represented by general formula (2) is preferably within 20°C.

[0024] The present invention also provides an organic electroluminescent device having a plurality of organic layers between an anode and a cathode, wherein at least one of the organic layers contains the above-mentioned mixed material for organic electroluminescent devices.

[0025] Preferably, the organic layer containing the mixed material for organic electroluminescent devices is at least one layer selected from the group consisting of a light-emitting layer, a hole-injection layer, a hole-transport layer, an electron-transport layer, an electron-injection layer, a hole-blocking layer, and an electron-blocking layer, and is more preferably a light-emitting layer. Furthermore, when the organic layer containing the mixed material for organic electroluminescent devices is a light-emitting layer, the light-emitting layer preferably contains at least one light-emitting dopant, and more preferably contains a compound represented by general formula (1) as a first host and a compound represented by general formula (2) as a second host, and the light-emitting layer contains at least one light-emitting dopant.

[0026] The present invention also provides a method for producing an organic electroluminescent device having a plurality of organic layers including an emitting layer between an anode and a cathode, the method comprising the steps of: preparing the above-mentioned mixed material for organic electroluminescent devices; and evaporating and depositing the mixed material for organic electroluminescent devices from a single evaporation source to form an emitting layer.

[0027] According to the present invention, it is possible to realize a practically useful organic EL element that has high efficiency and a long life despite a low driving voltage.

[0028] FIG. 1 is a cross-sectional view showing an example of the structure of an organic EL element.

[0029] The mixed material for organic electroluminescent devices of the present invention contains a compound represented by the general formula (1) and a compound represented by the general formula (2). To improve the characteristics of organic EL devices, the materials used in the organic layers must be highly durable against electric charges, and it is particularly important to suppress leakage of excitons and charges into surrounding layers in the light-emitting layer. To suppress this charge / exciton leakage, it is effective to improve the bias of the light-emitting region in the light-emitting layer. To achieve this, it is necessary to control the amount of both charges (electrons / holes) injected into the light-emitting layer or the transportability of both charges in the light-emitting layer within a preferred range.

[0030] The charge injection and transport properties of materials used in the organic layer are largely determined by the energy levels of the molecular orbitals of the materials and the strength of intermolecular interactions. When the mixed material for organic electroluminescent elements of the present invention is used as a material for organic EL devices, it is preferable that, among general formula (1), the formula (1a) contains an indolocarbazole compound having an ortho-linked biphenyldiyl group represented by formula (3a). This provides particularly high electron injection and transport properties, but the steric hindrance effect of the biphenyldiyl group can prevent indolocarbazole molecules from approaching each other. Furthermore, by changing the type of substituent and bonding position of the biphenyldiyl group, the intermolecular interactions of the molecular orbitals that contribute significantly to electron injection and transport to the light-emitting layer can be controlled at a high level.

[0031] Furthermore, when the mixed material for organic electroluminescent elements of the present invention is used as a material for organic EL elements, it is believed that an excellent organic EL element having high efficiency and long life despite low voltage can be obtained because it contains an oxygen-bridged biscarbazole compound having an energy level that facilitates hole injection, high hole transport property, and a highly durable skeleton, as represented by general formula (2). In particular, the heat resistance of materials is important in the organic EL panel production process, and the compound represented by general formula (2) has a high glass transition temperature, allowing for stable production of organic EL panels.

[0032] First, the compound represented by general formula (1) will be described. In general formula (1), ring A is a nitrogen-containing five-membered heterocycle represented by formula (1a), and the heterocycle is fused to two adjacent rings at any position, but is not fused at a side containing N. Therefore, the indolocarbazole ring has several isomeric structures, but the number is limited.

[0033] Specifically, in the compound represented by general formula (1), ring A is preferably represented by formula (3a), and there is an embodiment represented by any of the following formulas (5) to (10), preferably formulas (6), (8) to (10), and more preferably a structure represented by formula (10). In formulas (5) to (10), symbols common to general formula (1) have the same meanings. Ar ４ is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linking aromatic group in which two phenyl groups are linked together. p is the number of substitutions and represents an integer of 0 to 2. q is the number of substitutions and represents an integer of 0 to 3. Note that the benzene ring contained in the group corresponding to formula (3a) in the following formulas (5) to (10) may have a substituent, and in that case, the substituent is the same as the substituent when substituting an aromatic hydrocarbon group, an aromatic heterocyclic group, and a linking aromatic group.

[0034] In the general formula (1), Ar １ and Ar ２ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different from each other, and preferably １ , and Ar ２ are each independently a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, or a substituted or unsubstituted quaterphenyl group, and preferably Ar １ and Ar ２The sum of the numbers of benzene rings is 5 or less, more preferably 4 or less. A biphenyl group, a terphenyl group, or a quaterphenyl group has a structure in which 2, 3, or 4 benzene rings are linked together, respectively, and the bonding position of each benzene ring may be any of o-, m-, or p-position. In addition, the structure may be linear or branched.

[0035] In this specification, the term "linked aromatic group" refers to an aromatic group in which the aromatic rings of two or more aromatic groups selected from the group consisting of aromatic hydrocarbon groups and aromatic heterocyclic groups are linked by a single bond. These linking aromatic groups may be linear or branched. The linking position when benzene rings are linked may be ortho, meta, or para, with para- or meta-linking being preferred. The aromatic group may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and the multiple aromatic groups may be the same or different. In other words, the aromatic hydrocarbon groups or aromatic heterocyclic groups when linked may be the same or different.

[0036] R １ are each independently deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different. Preferred are deuterium, a substituted or unsubstituted phenyl group having 6 carbon atoms, a dibenzofuran group having 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which two of these aromatic groups are linked together.

[0037] Ar ３ is deuterium, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked aromatic group in which 2 to 5 phenyl groups are linked together. ３ is deuterium, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted quaterphenyl group, or a substituted or unsubstituted quinquiphenyl group, preferably Ar ３The sum of the numbers of benzene rings is 5 or less, more preferably 4 or less. A biphenyl group, a terphenyl group, or a quaterphenyl group has a structure in which 2, 3, or 4 benzene rings are linked together, and the bonding position of each benzene ring may be any of o-, m-, or p-position. In addition, the structure may be linear or branched.

[0038] Ar １ , Ar ２ , and R １ In the formula (I), specific examples of the unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, the unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or the unsubstituted linked aromatic group formed by linking 2 to 5 of these aromatic groups include benzene, naphthalene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or a group derived from a compound formed by linking 2 to 5 of these. Preferred are benzene, dibenzofuran, and a group derived from a compound formed by linking 2 to 5 of these.

[0039] In this specification, the aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group may each have a substituent. When the substituent has a substituent, the substituent is preferably deuterium, halogen, cyano group, triarylsilyl group, aliphatic hydrocarbon group having 1 to 10 carbon atoms, alkenyl group having 2 to 5 carbon atoms, alkoxy group having 1 to 5 carbon atoms, or diarylamino group having 12 to 44 carbon atoms. When the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear, branched, or cyclic. When the triarylsilyl group or diarylamino group serves as a substituent for the aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group, silicon and carbon, or nitrogen and carbon, are bonded by a single bond, respectively. The number of the substituents in each of the aromatic hydrocarbon group, aromatic heterocyclic group, and linking aromatic group is preferably 0 to 5, and more preferably 0 to 2. Furthermore, when the aromatic hydrocarbon group and aromatic heterocyclic group have a substituent, the number of carbon atoms of the substituent is not included in the calculation of the carbon number. However, it is preferable that the total number of carbon atoms, including the number of carbon atoms of the substituent, falls within the above range.

[0040] Specific examples of the substituent include deuterium, cyano, triphenylsilyl, trinaphthylsilyl, trianthranylsilyl, triphenanthrenylsilyl, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, neopentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, etc. Preferred are deuterium, cyano, triphenylsilyl, methyl, ethyl, t-butyl, propyl, butyl, pentyl, neopentyl, hexyl, heptyl, or octyldiphenylamino, naphthylphenylamino, or dinaphthylamino.

[0041] Ring A in general formula (1) is a nitrogen-containing five-membered heterocycle represented by formula (1a) that is fused with two adjacent rings at any position. Formula (3a) in which the nitrogen-containing five-membered heterocycle has a substituted or unsubstituted o-biphenyl group is more preferred compared to formula (1a). p represents the number of substitutions and is an integer of 0 to 2, preferably 1 or 2. q represents the number of substitutions and is an integer of 0 to 3, preferably 0 or 1.

[0042] Also, Ar in formula (3a) ４ is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked aromatic group in which two phenyl groups are linked together. p is the number of substitutions and represents an integer of 0 to 2, preferably 0 to 1. q is the number of substitutions and represents an integer of 0 to 3, preferably 1 or 2.

[0043] Specific examples of general formula (1) are shown below, but the present invention is not limited to these exemplary compounds. In the following structural formula, the number of substituted deuterium (D) s means the average number, and varies depending on the average deuteration rate.

[0044] Among these specific exemplified compounds, compounds 101, 107, 110, 117, 124, 127, 133, 136, 137, 138, 139, 142, 145, 146, 147, 148, 151, 154, 159, 163, 170, 186, 198, 221, 222, 228, 234, 235, 237, 244, 251, 254, 260, 263, 264, 265, 266, 269, 272, 273, 274, 277, 278, 281, and 282 are preferred because they exhibit high characteristics in terms of luminous efficiency and device life, while also exhibiting high thermal stability. 286, 290, 297, 313, 325, 348, and 349.

[0045] Next, the compound according to the general formula (2) will be explained. In the general formula (2), X is an oxygen atom or a sulfur atom, and preferably oxygen. １ ~Y １２ are each independently represented by C-Ra. １ and Z ２ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different. Preferably, they are substituted or unsubstituted aromatic hydrocarbon groups having 6 to 10 carbon atoms, or substituted or unsubstituted linked aromatic groups in which two of these aromatic hydrocarbon groups are linked together. More preferably, they are substituted or unsubstituted phenyl groups, substituted or unsubstituted biphenyl groups, substituted or unsubstituted naphthyl groups, or substituted or unsubstituted phenanthryl groups, and more preferably unsubstituted phenyl groups. A biphenyl group has a structure in which two benzene rings are linked together, and the bonding position of each benzene ring may be any of the o-, m-, or p-positions.

[0046] Ra is hydrogen, deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms. Preferably, it is hydrogen, deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, and more preferably hydrogen, deuterium, or a substituted or unsubstituted phenyl group. However, Z １ and Z ２ When Y is a substituted or unsubstituted phenyl group, １ ~Y １２ In the formula (I), at least one Ra in C-Ra is preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms. It is preferably a substituted or unsubstituted phenyl group or biphenyl group, and more preferably, Y １ ~Y １２ In any two of the groups C-Ra, Ra is a substituted or unsubstituted phenyl group, and more preferably Y ２ , Y ５ , Y ８ and Y １１ In the formula C-Ra, Ra is a substituted or unsubstituted phenyl group.

[0047] Z １ , Z ２ Specific examples of the unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, the unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or the unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together in Ra include the above-mentioned Ar １ , Ar ２ , and R １ Preferred are substituted or unsubstituted linking aromatic groups such as a substituted or unsubstituted phenyl group having 6 carbon atoms, a dibenzofuran group having 12 carbon atoms, or a biphenyl group or terphenyl group in which 2 or 3 of these aromatic groups are linked together.

[0048] Specific examples of general formula (2) are shown below, but the present invention is not limited to these exemplary compounds. In the following structural formula, the number of substituted deuterium (D) s means the average number, and varies depending on the average deuteration rate.

[0049] Among these specific exemplified compounds, preferred are compounds 401, 403, 404, 406, 407, 409, 411, 412, 413, 422, 423, 424, 425, 428, 429, 431, 432, 465, 467, 468, 470, 471, 473, 475, 476, 477, 486, 487, 488, 489, 492, and 493, which exhibit high properties in terms of luminous efficiency and device life and also have high thermal stability.

[0050] The hydrogen atoms in the compound contained in the mixed material for organic electroluminescent devices of the present invention may be deuterium atoms. That is, the hydrogen atoms in the fused rings (indolocarbazole rings) represented by the general formula (1) and the formula (1a), Ar １ , Ar ２ , Ar ３ , R １ The hydrogen atoms in the aromatic rings and the hydrogen atoms in the substituents substituted on these aromatic rings may be partially or entirely deuterium atoms. １ and Z ２ A part or all of the hydrogen atoms in the aromatic rings and the substituents substituted on these aromatic rings may be deuterium atoms.

[0051] Furthermore, when these compounds are deuterated compounds in which some or all of the hydrogen atoms are deuterated, the compound represented by general formula (1) or general formula (2) includes both a single compound and a mixture of two or more compounds. That is, the compound represented by general formula (1) or general formula (2) may be two or more types of compounds included in these formulas, or may be a mixture of compounds with different deuteration numbers or deuteration positions. Furthermore, all of the compounds included in the mixed material for an organic electroluminescent device may be deuterated, or only some of the compounds may be deuterated.

[0052] The compound represented by general formula (1) or (2) preferably has an average deuteration ratio of 30% or more, more preferably 40% or more. Specifically, an average deuteration ratio of 50% means that half of all hydrogen atoms are replaced with deuterium atoms.

[0053] The average deuteration ratio can be determined by mass spectrometry or proton nuclear magnetic resonance spectroscopy. For example, when determining by proton nuclear magnetic resonance spectroscopy, a measurement sample is first prepared by adding and dissolving the compound and an internal standard in a deuterated solvent, and the proton concentration [mol / g] of the compound contained in the measurement sample is calculated from the integrated intensity ratio derived from the internal standard and the compound. Next, the ratio of the proton concentration of the deuterated compound to the proton concentration of the corresponding non-deuterated compound is calculated, and the ratio is subtracted from 1 to calculate the average deuteration ratio of the deuterated compound.

[0054] The mixed material for a mixed organic electroluminescent device of the present invention contains a compound represented by the general formula (1) and a compound represented by the general formula (2), and the mixing ratio (weight ratio) thereof is preferably such that the compound represented by the general formula (1) accounts for 20 to 70 mass %, and more preferably 20 to 60 mass %, of the total of the two.

[0055] The mixed material for organic electroluminescent devices may contain other compounds in addition to the compound represented by general formula (1) and the compound represented by general formula (2). Examples of other compounds include known host materials and luminescent dopants. However, the compound represented by general formula (1) and the compound represented by general formula (2) preferably account for 50% by mass or more of the total, and more preferably 75% by mass or more.

[0056] The mixed material for organic electroluminescent elements of the present invention is suitable as a material or component of an organic EL element. When used as a component of an organic EL element, the mixed material for organic electroluminescent elements is included in an organic layer of the organic EL element, and this organic layer is preferably selected from the group consisting of an emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a hole blocking layer, and an electron blocking layer. Preferably, the organic layer is an emitting layer, and the emitting layer preferably contains at least one luminescent dopant.

[0057] When the light-emitting layer contains the mixed material for organic electroluminescent devices of the present invention, it is desirable that the mixed material for organic electroluminescent devices of the present invention is contained as a host in the light-emitting layer. Advantageously, the compound represented by the general formula (1) is used as a first host, and the compound represented by the general formula (2) is used as a second host.

[0058] When the mixed material for organic electroluminescent elements of the present invention is used as a component of an organic EL element, a method of vapor-depositing a plurality of compounds such as the compound represented by general formula (1) and the compound represented by general formula (2) individually from different vapor deposition sources can be employed, but it is preferable to premix them before vapor deposition to form a premixture, and then simultaneously evaporate and vapor-deposit the premixture from a single vapor deposition source to form an organic layer, preferably a light-emitting layer.

[0059] The premix is ​​a form of a mixed material, and may be prepared by mixing the compound represented by the general formula (1) and the compound represented by the general formula (2) in powder form, by melt-mixing by heating under reduced pressure or in an inert gas atmosphere such as nitrogen, or by sublimating the compounds to be mixed together. On the other hand, the mixed material contains the compound represented by the general formula (1) and the compound represented by the general formula (2), and may be in powder form or in thin film form. In the case of a thin film form, the compound represented by the general formula (1) and the compound represented by the general formula (2) may be contained in the same organic layer or in different organic layers of a device.

[0060] When the above premix is ​​used as the mixed material for the organic electroluminescent device of the present invention to form a light-emitting layer, a necessary light-emitting dopant material or other hosts to be used as needed may be mixed therein. However, if there is a large difference in the temperature at which the desired vapor pressure is achieved, it is preferable to vapor-deposit the light-emitting dopant material and other hosts from different vapor deposition sources.

[0061] When the mixed material for an organic electroluminescent element of the present invention is the above-mentioned premixture, in order to stably carry out vapor deposition, it is desirable that the compound represented by the general formula (1) and the compound represented by the general formula (2) have a 50% weight loss temperature of 20°C or less, more preferably 15°C or less.

[0062] The organic EL device of the present invention has a plurality of organic layers between opposing electrodes, at least one of which is an emitting layer. At least one emitting layer preferably contains the above-mentioned mixture material for organic electroluminescent devices as a host. When the mixture material for organic electroluminescent devices is contained in the emitting layer, it preferably contains at least one emitting dopant.

[0063] Next, the structure of the organic EL element of the present invention will be described with reference to the drawings, but the structure of the organic EL element of the present invention is not limited to this.

[0064] FIG. 1 is a cross-sectional view showing an example of the structure of a typical organic EL device used in the present invention, in which 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents an emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. The organic EL device of the present invention may have an exciton blocking layer adjacent to the emitting layer, or an electron blocking layer between the emitting layer and the hole injection layer. The exciton blocking layer can be inserted on either the anode side or the cathode side of the emitting layer, or both sides can be inserted simultaneously. The organic EL device of the present invention has an anode, an emitting layer, and a cathode as essential layers, but may also have a hole injection transport layer and an electron injection transport layer in addition to the essential layers, and may further have a hole blocking layer between the emitting layer and the electron injection transport layer. Note that the hole injection transport layer refers to either the hole injection layer or the hole transport layer, or both, and the electron injection transport layer refers to either the electron injection layer or the electron transport layer, or both.

[0065] It is also possible to have a structure opposite to that shown in FIG. 1 , that is, 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 this order, and in this case too, layers can be added or omitted as necessary.

[0066] The organic EL device of the present invention is preferably supported on a substrate. There are no particular limitations on the substrate, and any substrate conventionally used in organic EL devices, such as glass, transparent plastic, or quartz, can be used.

[0067] Anode materials for organic EL devices are preferably metals, alloys, electrically conductive compounds, or mixtures thereof, each having a large work function (4 eV or more). Specific examples of such electrode materials include metals such as Au, CuI, indium tin oxide (ITO), and SnO. ２Examples of suitable conductive transparent materials include ZnO and ZnO. Amorphous materials capable of forming transparent conductive films, such as IDIXO (In2O3-ZnO), may also be used. The anode may be formed by depositing a thin film of these electrode materials using methods such as vapor deposition or sputtering, followed by photolithography to form a desired pattern. Alternatively, if pattern precision is not required (approximately 100 μm or greater), a pattern may be formed using a mask of the desired shape during vapor deposition or sputtering of the electrode material. Alternatively, when using a coatable material such as an organic conductive compound, wet film formation methods such as printing or coating can be used. When extracting light from this anode, a transmittance of greater than 10% is desirable, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness, depending on the material, is typically selected within the range of 10 to 1,000 nm, preferably 10 to 200 nm.

[0068] Cathode: A material consisting of a metal (electron injecting metal), alloy, electrically conductive compound, or mixture thereof, having a small work function (4 eV or less) is used as the cathode material. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, and aluminum / aluminum oxide (Al ２ O ３) mixtures, indium, lithium / aluminum mixtures, rare earth metals, etc. Among these, from the viewpoints of electron injection ability and durability against oxidation, etc., mixtures of an electron injection metal and a second metal having a larger and more stable work function than the electron injection metal, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide mixtures, lithium / aluminum mixtures, and aluminum, are preferred. The cathode can be fabricated by forming a thin film of these cathode materials by methods such as vapor deposition or sputtering. Furthermore, the cathode preferably has a sheet resistance of several hundred Ω / □ or less, and the film thickness is typically selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. It is advantageous to make either the anode or cathode of the organic EL element transparent or semitransparent to allow the emitted light to pass through, thereby improving the luminance of the emitted light.

[0069] Furthermore, a transparent or semitransparent cathode can be fabricated by forming the above-mentioned metal as a cathode with a film thickness of 1 to 20 nm and then forming the conductive transparent material described in the description of the anode thereon. This can be applied to fabricate an element in which both the anode and cathode are optically transparent.

[0070] -Light-emitting layer- The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and cathode, respectively, and contains a light-emitting dopant material and a host.

[0071] The mixed material for organic electroluminescent elements of the present invention can be suitably used as a material for organic electroluminescent elements, and preferably can be used as a host. It is preferable to use a compound represented by general formula (1) as a first host and a compound represented by general formula (2) as a second host. The first host or second host may be used alone or in combination with two or more different compounds. If necessary, one or more other known host materials may be used in combination. The amount of the host materials used is preferably 50% by mass or less, and preferably 25% by mass or less, based on the total amount of the host materials.

[0072] The method for manufacturing an organic electroluminescent device of the present invention includes the steps of preparing the above-mentioned premix and evaporating and depositing the premix from a single evaporation source to form a light-emitting layer. The method of vaporizing and depositing the premix from a single evaporation source is more preferred. Here, the premix is ​​preferably a homogeneous mixed material for an organic electroluminescent device.

[0073] When the first host and second host are premixed and used, it is desirable that the difference in 50% weight loss temperature (T50) be small in order to reproducibly fabricate organic EL devices with good characteristics. The 50% weight loss temperature is the temperature at which the weight is reduced by 50% when the temperature is raised from room temperature to 550°C at a rate of 10°C per minute in TG-DTA measurement under reduced pressure (1 Pa) of nitrogen gas flow. It is believed that vaporization by evaporation or sublimation occurs most actively around this temperature.

[0074] The difference in the 50% weight loss temperature is preferably within 20° C., because a uniform deposited film can be obtained when the premix is ​​vaporized from a single evaporation source and deposited. In this case, a luminescent dopant material required for forming the luminescent layer or other hosts to be used as needed may be mixed into the premix.

[0075] When preparing a premix by premixing, a method that can mix the components as uniformly as possible is desirable, and examples of the method include pulverization and mixing, heating and melting under reduced pressure or in an inert gas atmosphere such as nitrogen, sublimation, etc. However, the premix may be in the form of a powder, stick, or granules.

[0076] When the compound represented by general formula (1) or the compound represented by general formula (2) is a deuterated product, known methods include a method of preparing the compound using a fully or partially deuterated starting material, and a method of preparing the compound by a hydrogen / deuterium exchange reaction. The fully or partially deuterated starting material can be purchased from a commercial supplier or can be prepared by a known hydrogen / deuterium exchange reaction. Known hydrogen / deuterium exchange reactions include a method in which a non-deuterated compound is subjected to the action of deuterium gas or its equivalent in the presence of a transition metal catalyst, and a method in which a non-deuterated compound is treated with a deuterated solvent (e.g., deuterated benzene) in the presence of an acid catalyst.

[0077] When a phosphorescent dopant is used as the luminescent dopant material, the phosphorescent dopant preferably contains an organometallic complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Specifically, iridium complexes described in J.Am.Chem.Soc.2001,123,4304, JP2013-530515A, US2016 / 0049599A, US2017 / 0069848A, US2018 / 0282356A, or US2019 / 0036043A, or platinum complexes described in US2018 / 0013078A or KR2018-094482A are preferably used, but are not limited to these.

[0078] The phosphorescent dopant material may be contained in the light-emitting layer alone or in combination of two or more kinds. The content of the phosphorescent dopant material is preferably 0.1 to 30% by mass, more preferably 1 to 20% by mass, based on the host material.

[0079] The phosphorescent dopant material is not particularly limited, but specific examples include the following compounds.

[0080] When a fluorescent dopant is used as the light-emitting dopant material, the fluorescent dopant is not particularly limited, and examples thereof include benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, condensed aromatic compounds, perinone derivatives, oxadiazole derivatives, oxazine derivatives, aldazine derivatives, pyrrolidine derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, styrylamine derivatives, diketopyrrolopyrrole derivatives, aromatic dimethylidine compounds, various metal complexes typified by metal complexes of 8-quinolinol derivatives, metal complexes of pyrromethene derivatives, rare earth complexes, and transition metal complexes, polymer compounds such as polythiophene, polyphenylene, and polyphenylenevinylene, and organic silane derivatives. Preferred examples include condensed aromatic derivatives, styryl derivatives, diketopyrrolopyrrole derivatives, oxazine derivatives, pyrromethene metal complexes, transition metal complexes, and lanthanoid complexes, and more preferred examples include naphthalene, pyrene, chrysene, triphenylene, benzo[c]phenanthrene, benzo[a]anthracene, pentacene, perylene, fluoranthene, acenaphthofluoranthene, dibenzo[a,j]anthracene, dibenzo[a,h]anthracene, benzo[a]naphthalene, hexacene, naphtho[2,1-f]isoquinoline, α-naphthaphenanthridine, phenanthroxazole, quinolino[6,5-f]quinoline, and benzothiophanthrene. These may have an alkyl group, an aryl group, an aromatic heterocyclic group, or a diarylamino group as a substituent.

[0081] When a thermally activated delayed fluorescent dopant is used as the luminescent dopant material, examples of the thermally activated delayed fluorescent dopant include, but are not limited to, metal complexes such as tin complexes and copper complexes, indolocarbazole derivatives described in WO2011 / 070963A, cyanobenzene derivatives and carbazole derivatives described in Nature 2012,492,234, phenazine derivatives, oxadiazole derivatives, triazole derivatives, sulfone derivatives, phenoxazine derivatives and acridine derivatives described in Nature Photonics 2014,8,326, and the like.

[0082] The thermally activated delayed fluorescent dopant material is not particularly limited, but specific examples thereof include the following compounds.

[0083] The light-emitting layer may contain only one type of thermally activated delayed fluorescent dopant material, or two or more types. The thermally activated delayed fluorescent dopant may be used in combination with a phosphorescent or fluorescent dopant. The content of the thermally activated delayed fluorescent dopant material is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, relative to the host material.

[0084] Injection layer: An injection layer is a layer provided between an electrode and an organic layer to reduce driving voltage and improve luminance, and includes a hole injection layer and an electron injection layer. An injection layer may be provided between the anode and the light-emitting layer or the hole transport layer, and between the cathode and the light-emitting layer or the electron transport layer. An injection layer can be provided as needed.

[0085] -Hole-blocking layer- In a broad sense, the hole-blocking layer functions as an electron-transporting layer, and is made of a hole-blocking material that has the function of transporting electrons but an extremely small ability to transport holes. By transporting electrons while blocking holes, the hole-blocking layer can improve the probability of recombination of electrons and holes in the light-emitting layer.

[0086] - Electron Blocking Layer - In a broad sense, the electron blocking layer functions as a hole transporting layer, and can increase the probability of recombination of electrons and holes in the light-emitting layer by blocking electrons while transporting holes.

[0087] As the material for the electron blocking layer, known electron blocking layer materials can be used, and the materials for the hole transport layer described below can also be used as needed. The thickness of the electron blocking layer is preferably 3 to 100 nm, more preferably 5 to 30 nm.

[0088] -Exciton blocking layer- An exciton blocking layer is a layer that prevents excitons generated by the recombination of holes and electrons in the light-emitting layer from diffusing into the charge transport layer. Insertion of this layer makes it possible to efficiently confine excitons within the light-emitting layer, thereby improving the luminous efficiency of the device. In a device having two or more adjacent light-emitting layers, an exciton blocking layer can be inserted between two adjacent light-emitting layers.

[0089] The exciton blocking layer may be made of any known exciton blocking layer material, such as 1,3-dicarbazolylbenzene (mCP) or bis(8-hydroxy-2-methylquinoline)-(4-phenylphenoxy)aluminum(III) (BAlq).

[0090] -Hole Transport Layer- The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer may be provided as a single layer or as a plurality of layers.

[0091] The hole transport material has either hole injection or transport properties or electron barrier properties, and may be either organic or inorganic. Any conventionally known compound can be selected and used for the hole transport layer. Examples of such hole transport materials include porphyrin derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers. Porphyrin derivatives, arylamine derivatives, and styrylamine derivatives are preferred, and arylamine derivatives are more preferred.

[0092] - Electron Transport Layer - The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer may be a single layer or multiple layers.

[0093] The electron transport material (which may also serve as a hole blocking material) may have the function of transporting electrons injected from the cathode to the light-emitting layer. The electron transport layer may be formed from any of conventionally known compounds, including, for example, polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline, tris(8-hydroxyquinoline)aluminum(III) derivatives, phosphine oxide derivatives, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, bipyridine derivatives, quinoline derivatives, oxadiazole derivatives, benzimidazole derivatives, benzothiazole derivatives, and indolocarbazole derivatives. Furthermore, polymeric materials in which any of these materials are incorporated into a polymer chain or in which any of these materials form the polymer backbone may also be used.

[0094] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples and can be implemented in various forms as long as they do not depart from the gist of the invention.

[0095] Synthesis Example 1 To 5 g of compound (a), 5.6 g of compound (b), 8.6 g of tripotassium phosphate, and 60 ml of 1,3-dimethyl-2-imidazolidinone were added and stirred at 200 °C for 48 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was purified by silica gel column chromatography and crystallization to obtain 6.6 g of intermediate (1-1) as a white solid (70% yield). Under a nitrogen atmosphere, 1.3 g of 60% by weight sodium hydride was added to 30 ml of N,N'-dimethylacetamide to prepare a suspension. 6 g of intermediate (1-1) dissolved in 170 ml of N,N'-dimethylacetamide was added and stirred for 30 minutes. 5.1 g of compound (c) was added and stirred for 6 hours. The reaction solution was added to a mixed solution of methanol (300 ml) and distilled water (100 ml) with stirring, and the resulting precipitate was collected by filtration. The obtained solid was purified by silica gel column chromatography and crystallization to obtain 6.5 g (yield 66%) of Compound 117 as a yellow solid (APCI-TOFMS, m / z 792 [M+H]+).

[0096] Synthesis Example 2 Compound 406 was synthesized according to the following reaction. To 1.6 g of compound (d), 5.4 g of compound (e), 0.18 g of copper iodide, 0.27 g of 8-quinolinol, 148 g of potassium carbonate, and 20 g of toluene were added, and the mixture was stirred at 190°C for 38 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was purified by silica gel column chromatography and crystallization to obtain 1.6 g (yield 53%) of compound 406 as a white solid.

[0097] Synthesis Example 3 To 8.4 g of compound (1-1), 200 ml of deuterated benzene (CD) and 12.7 g of deuterated trifluoromethanesulfonic acid (TfOD) were added, and the mixture was heated and stirred at 50°C for 4 hours under a nitrogen atmosphere. The reaction mixture was added to a heavy water solution (130 ml) of sodium carbonate (10.2 g) and quenched. After separation and purification, 6.8 g of the deuterated product, compound (1-1-D), was obtained. Note that the substitution number of s for the substituted deuterium (D) refers to the average number.

[0098] Compound 244 was synthesized according to the following reaction: Synthesis Example 4 Under a nitrogen atmosphere, 1.8 g of 60 wt% sodium hydride was added to 45 mL of N,N'-dimethylacetamide to prepare a suspension. 6.9 g of intermediate (1-1-D) dissolved in 240 mL of N,N'-dimethylacetamide was added and stirred for 30 minutes. 6.0 g of compound (c) was added to the suspension and stirred for 6 hours. The reaction solution was poured into a mixture of methanol (400 mL) and distilled water (150 mL) with stirring, and the resulting precipitate was collected by filtration. The resulting solid was purified by silica gel column chromatography and crystallized to obtain 7.8 g (69% yield) of compound 244 as a yellow solid. Note that the "s" in the deuterium (D) substitution indicates the average number.

[0099] The average deuteration ratio of compound 244 was determined by proton nuclear magnetic resonance spectroscopy. A measurement sample was prepared by dissolving compound 244 (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 244 contained in the measurement sample was calculated from the integrated intensity ratio of the internal standard and compound 244. The average proton concentration [mol / g] of the non-deuterated form of compound 244 (compound 117) was also calculated in the same manner. Next, the ratio of the proton concentration of compound 244 to that of compound 117 was calculated and subtracted from 1 to calculate the average deuteration ratio of compound 244 as 76.4%.

[0100] Compound 470 was synthesized according to the following reaction: Synthesis Example 5 To 1.4 g of compound 406, 40 ml of deuterated benzene (CD) and 3 g of deuterated trifluoromethanesulfonic acid (TfOD) were added, and the mixture was heated and stirred at 50°C for 4 hours under a nitrogen atmosphere. The reaction mixture was added to a heavy water solution (25 ml) of sodium carbonate (2.0 g) and quenched. After separation and purification, 1.2 g of the deuterated product, compound 470, was obtained. Note that the substitution number of s in the deuterium (D) substituted represents the average number.

[0101] The average deuteration ratio of compound 470 was determined by proton nuclear magnetic resonance spectroscopy. A measurement sample was prepared by dissolving compound 470 (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 470 contained in the measurement sample was calculated from the integrated intensity ratio derived from the internal standard and compound 470. The average proton concentration [mol / g] of the non-deuterated form of compound 470 (compound 406) was also calculated in the same manner. Next, the ratio of the proton concentration of compound 470 to the proton concentration of compound 406 was calculated and subtracted from 1 to calculate the average deuteration ratio of compound 470 as 72.5%.

[0102] Synthesis Example 6 Reactions were carried out in the same manner as in Synthesis Examples 4 and 5 to synthesize deuterated compounds 228, 235, 264, 265, 281, 476, and 468. The average deuteration ratios for these compounds were calculated in the same manner as for 244 and 470, and the results are shown in Table 1.

[0103] The compounds used in the examples and comparative examples are shown below.

[0104] Example 1 Each thin film was deposited by vacuum deposition on a glass substrate on which an anode made of ITO with a film thickness of 110 nm was formed at a vacuum degree of 4.0 × 10 -5The layers were laminated at 100 Pa. First, compound A and compound B were co-deposited from separate evaporation sources on the ITO substrate to form a hole-injection layer with a thickness of 10 nm. The co-deposition was carried out under evaporation conditions such that the concentration of compound B was 3% by mass. Next, compound A was formed as a first hole-transport layer with a thickness of 110 nm. Next, compound C was formed as a second hole-transport layer with a thickness of 10 nm. Next, compound D was formed as an electron-blocking layer with a thickness of 5 nm. Next, compound 101 (first host) and compound 404 (second host) were mixed while grinding them in a mortar to obtain a premix, which was co-evaporated from a single evaporation source. Compound E-1 was then co-deposited as an emitting dopant from a separate evaporation source to form a 40-nm-thick emitting layer. The co-deposition was carried out under evaporation conditions such that the concentration of compound E-1 was 15% by mass and the weight ratio of the first host to the second host was 40:60. Next, compound F was formed as a hole-blocking layer with a thickness of 5 nm. Next, Compound G was formed as an electron transport layer to a thickness of 30 nm. Furthermore, LiF was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer. Finally, Al was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby completing the organic EL device.

[0105] Examples 2 to 40 and Comparative Examples 1 and 2 Organic EL devices were prepared in the same manner as in Example 1, except that the compounds shown in Table 2 were used as the first host and the second host in the mass ratio shown in Table 2.

[0106] The evaluation results of the fabricated organic EL devices are shown in Table 2. In the table, the luminance, voltage, and current efficiency are measured at a driving current of 10 mA / cm. 2 The LT70 is the time required for the luminance to decay to 70% when driven at an initial luminance of 9000 nits, and represents the lifetime characteristics. The numbers for the first host and the second host are the numbers assigned to the above example compounds, and the weight ratio is first host:second host. Note that all characteristics are expressed as relative values, with the characteristics of Comparative Example 1 taken as 100%.

[0107]

[0108] Examples 41 to 82 and Comparative Examples 3 and 4 Organic EL devices were prepared in the same manner as in Example 1, except that the compounds shown in Table 3 were used as the first host and the second host, and were co-deposited from different evaporation sources in the weight ratios shown in Table 3.

[0109] The obtained organic EL device was evaluated in the same manner as in Example 1. The results are shown in Table 3. Note that all characteristics are expressed as relative values, with the characteristics of Comparative Example 3 taken as 100%.

[0110]

[0111] These results demonstrate that Examples 1 to 82 exhibit low voltage, high efficiency, and long life characteristics compared to the Comparative Examples. Generally, efficiency and life may have a trade-off relationship, making it difficult to improve both current efficiency and life characteristics. In particular, improving current efficiency leads to lower power consumption and improved luminance, so if current efficiency can be improved while maintaining a certain level of life characteristics, more practical devices can be achieved. From this perspective, Examples 1 to 82, which used the mixed material of the present invention, achieved voltage characteristics of 99% or less and current efficiencies of 105% or more on average, while demonstrating life characteristics of 100% or more, compared to Comparative Examples 1 to 4, which used a conventional compound as part of the mixed host material, thereby providing practically advantageous organic EL devices.

[0112] Example 83: Each thin film was deposited by vacuum deposition on a glass substrate on which an anode made of ITO with a film thickness of 110 nm was formed, at a vacuum degree of 4.0 × 10 -5The layers were laminated at 100 Pa. First, compound A and compound B were co-deposited from separate evaporation sources on the ITO substrate to form a hole-injection layer with a thickness of 10 nm. The co-deposition was carried out under evaporation conditions such that the concentration of compound B was 3% by mass. Next, compound A was formed as a first hole-transport layer with a thickness of 110 nm. Next, compound C was formed as a second hole-transport layer with a thickness of 10 nm. Next, compound D was formed as an electron-blocking layer with a thickness of 5 nm. Next, compound 101 (first host) and compound 404 (second host) were mixed while grinding them in a mortar, and a premix was obtained. This was then co-evaporated from a single evaporation source. Compound E-2 was then co-deposited as an emitting dopant from a separate evaporation source to form a 40-nm-thick emitting layer. The co-deposition was carried out under evaporation conditions such that the concentration of compound E-2 was 5% by mass and the weight ratio of the first host to the second host was 30:70. Next, compound F was formed as a hole-blocking layer with a thickness of 5 nm. Next, Compound G was formed as an electron transport layer to a thickness of 30 nm. Furthermore, LiF was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer. Finally, Al was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby completing the organic EL device.

[0113] Examples 84 to 122 and Comparative Examples 5 to 6 Organic EL devices were prepared in the same manner as in Example 83, except that the compounds shown in Table 4 were used as the first host and the second host in the mass ratio shown in Table 4.

[0114] The evaluation results of the fabricated organic EL devices are shown in Table 4. In the table, the luminance, voltage, and current efficiency are 2 The LT70 is the time required for the luminance to decay to 70% when driven at an initial luminance of 9000 nits, and represents the lifetime characteristics. The numbers for the first host and the second host are the numbers assigned to the above example compounds, and the weight ratio is first host:second host. Note that all characteristics are expressed as relative values, with the characteristics of Comparative Example 5 taken as 100%.

[0115]

[0116] Examples 123 to 164 and Comparative Examples 7 to 8 Organic EL devices were prepared in the same manner as in Example 83, except that the compounds shown in Table 3 were used as the first host and the second host, and were co-deposited from different evaporation sources in the weight ratios shown in Table 5.

[0117] The obtained organic EL device was evaluated in the same manner as in Example 1. The results are shown in Table 5. Note that all characteristics are expressed as relative values, with the characteristics of Comparative Example 7 taken as 100%.

[0118]

[0119] These results demonstrate that Examples 83 to 164 exhibit higher efficiency and longer lifetime characteristics than the comparative examples. Generally, efficiency and lifetime are sometimes in a trade-off relationship, making it difficult to improve both current efficiency and lifetime characteristics. In particular, improving current efficiency leads to lower power consumption and improved luminance, so if current efficiency can be improved while maintaining a certain level of lifetime characteristics, more practical devices can be achieved. From this perspective, when comparing Examples 83 to 164, which used the mixed material of the present invention, with Comparative Examples 5 to 8, which used a conventional compound as part of the mixed host material, and the comparative examples with similar blend ratios, they achieved current efficiencies of 100% or more while exhibiting long lifetime characteristics, thereby enabling the production of practically advantageous organic EL devices.

[0120] Table 6 shows the 50% weight loss temperatures (T50) of compounds 101, 110, 117, 137, 138, 139, 145, 154, 228, 235, 244, 264, 265, 272, 281, 404, 406, 412, 468, 470, 476, 401, H, J, K, and L.

[0121]

[0122] Table 7 also shows the glass transition temperatures (Tg) of compounds 404, 406, 412, 401, and H.

[0123] In general, heat resistance of materials is important in the organic EL panel production process, and materials exhibiting high Tg are preferred. From this perspective, Examples 1 to 164, which use the mixed materials according to the present invention, can produce organic EL panels more stably than Comparative Examples 1 to 8 due to the high thermal stability of the second host used therein.

[0124] 1: Substrate, 2: Anode, 3: Hole injection layer, 4: Hole transport layer, 5: Light-emitting layer, 6: Electron transport layer, 7: Cathode

Claims

1. A mixed material for an organic electroluminescent device, comprising a compound represented by the following general formula (1) and a compound represented by the following general formula (2): (Here, ring A is a nitrogen-containing five-membered heterocycle represented by formula (1a) which is fused to two adjacent rings at any position. Ar １ and Ar ２ are each independently hydrogen, deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different. １ are each independently deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different from each other. a to c are the number of substitutions, a and c are each independently an integer of 0 to 4, and b is an integer of 0 to 2. Ar ３ is deuterium, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked aromatic group in which 2 to 5 phenyl groups are linked. n is the number of substitutions and is an integer of 0 to 4. (wherein X is an oxygen atom or a sulfur atom, and Y １ ~Y １２ are each independently represented by C-Ra. １ and Z ２ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic groups are linked together, and when linked, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different from each other. Ra is hydrogen, deuterium, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms.

2. In the general formula (1), the formula (1a) is represented by the following formula (3a), and Ar １ , and Ar ２ is each independently a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, or a substituted or unsubstituted quaterphenyl group. (wherein, Ar ４ is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked aromatic group in which two phenyl groups are linked together. p is the number of substitutions and represents an integer of 0 to 2. q is the number of substitutions and represents an integer of 0 to 3.

3. Z in the general formula (2) １ and Z ２ The mixed material for an organic electroluminescent device according to claim 1, characterized in that Z １ and Z ２ When R a is a substituted or unsubstituted phenyl group, at least one R a is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms.

4. The mixed material for organic electroluminescent devices according to claim 1, characterized in that the ratio of the compound represented by general formula (1) to the total of the compound represented by general formula (1) and the compound represented by general formula (2) is 20 mass% or more and 70 mass% or less.

5. The mixed material for organic electroluminescent devices according to claim 1, wherein at least one of the compounds represented by the general formula (1) and the compounds represented by the general formula (2) has some or all of its hydrogen atoms substituted with deuterium.

6. The mixed material for organic electroluminescent devices according to claim 1, characterized in that the mixed material for organic electroluminescent devices is a material for manufacturing at least one layer of an organic electroluminescent device having a plurality of organic layers between an anode and a cathode by a vapor deposition method, and is a premixture that is mixed in advance before vapor deposition.

7. The mixed material for organic electroluminescent devices according to claim 6, characterized in that the difference in 50% weight loss temperature between the compound represented by the general formula (1) and the compound represented by the general formula (2) is within 20°C.

8. An organic electroluminescent device having a plurality of organic layers between an anode and a cathode, characterized in that at least one of the organic layers contains the mixed material for organic electroluminescent devices according to any one of claims 1 to 7.

9. The organic electroluminescent device according to claim 8, wherein the organic layer containing the mixed material for organic electroluminescent devices is at least one layer selected from the group consisting of a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a hole blocking layer and an electron blocking layer.

10. The organic electroluminescent device according to claim 8, wherein the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, contains a compound represented by general formula (1) as a first host and a compound represented by general formula (2) as a second host, and the emitting layer contains at least one luminescent dopant.

11. A method for producing an organic electroluminescent device having a plurality of organic layers including an emitting layer between an anode and a cathode, comprising the steps of: preparing a mixed material for organic electroluminescent devices according to any one of claims 1 to 7; and evaporating and depositing the mixed material for organic electroluminescent devices from a single evaporation source to form an emitting layer.

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