Mixed material for organic electroluminescent element, and organic electroluminescent element

Abstract

Provided is a mixed material suitable for a practically useful organic EL element having high efficiency and a long life in spite of a low driving voltage.　The mixed material for an organic electroluminescent element contains a compound represented by general formula (1) and a compound represented by general formula (2). (Ring A is a nitrogen-containing five-membered heterocyclic ring expressed by formula (1a); Ar1 and Ar2 are each a C6-18 aromatic hydrocarbon group or the like; R1 is a C6-18 aromatic hydrocarbon group or the like; (a)-(c) are numbers of substitutions; and Ar3 is a connected phenyl group in which 2-6 phenyl groups are connected.) (X is an oxygen atom or a sulfur atom; Y1 to Y12 are each C-Ra; Z1 and Z2 are each a C6-18 aromatic hydrocarbon group or the like; and Ra is hydrogen, deuterium, or a substituted or unsubstituted C6-18 aromatic hydrocarbon group or the like.)

Description

Mixed material for organic electroluminescent devices and organic electroluminescent devices

[0001] This invention relates to a mixed material for organic electroluminescent devices and an organic electroluminescent device (referred to as an organic EL element) using the same. More specifically, it relates to a mixed material for organic electroluminescent devices comprising an indrocarbazole compound and a biscarbazole compound crosslinked with an oxygen atom or a sulfur atom, and an organic EL element using the same.

[0002] When a voltage is applied to an organic electroluminescent device (also known as an organic EL device), 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 devices that use emission from singlet excitons are said to have an internal quantum efficiency limited to 25%. On the other hand, phosphorescent organic EL devices 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. However, extending the lifespan 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 it is theoretically thought that the internal quantum efficiency can be increased to 40%. However, since the efficiency is lower compared to phosphorescent organic EL devices, further improvement in efficiency is required. 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 from triplet excitons to singlet excitons occurs in materials with a small energy difference between the singlet and triplet levels, and it is theoretically thought that the internal quantum efficiency can be increased to 100%. However, similar to phosphorescent devices, further improvement in lifetime characteristics is required.

[0004] Here, Patent Document 3 discloses the use of indolocarbazole compounds as host materials. Furthermore, Patent Documents 4 and 5 disclose the use of oxygen-crosslinked biscarbazole compounds as host materials.

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

[0006] Furthermore, Patent Document 9 discloses the use of a mixed material for organic electroluminescent devices, comprising multiple indolocarbazole compounds and oxygen-crosslinked biscarbazole compounds, as a host material.

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

[0008] WO2010 / 134350 WO2011 / 070963 WO2008 / 056746 WO 2011 / 019173 A2WO 2014 / 057684 A1US Patent Publication 2014 / 197386 US Patent Publication 2015 / 001488 KR102283849WO 2018 / 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 while simultaneously ensuring sufficient long-life characteristics. In view of the above situation, the present invention aims to provide a practically useful organic EL element and a suitable compound that have high efficiency and long lifespan despite having a low driving voltage.

[0010] As a result of diligent research, the inventors of the present invention have found that using a mixed material for organic electroluminescent devices, which consists of a specific indolocarbazole compound and a crosslinked biscarbazole compound crosslinked with an oxygen atom or a sulfur atom, exhibits excellent properties in organic electroluminescent devices, thus completing the present invention.

[0011] The present invention relates to 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).

[0012] Here, ring A is a nitrogen-containing five-membered heterocycle represented by formula (1a), which condenses with two adjacent rings at arbitrary positions. １ and Ar ２ Each of these substituents is 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 formed by the linking of 2 to 5 of these aromatic groups. In the case of linking, the aromatic hydrocarbon groups or aromatic heterocyclic groups may be the same or different from each other. Details of these substituents will be described later.

[0013] R １Each is 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. The aromatic hydrocarbon group or aromatic heterocyclic group in the case of linking may be the same as or different from each other.

[0014] a to c represent the number of substituents, a and c are each independently an integer of 0 to 4, b is an integer of 0 to 2, and preferably, a and c are each independently an integer of 0 to 2, and b is an integer of 0 to 1. Ar ３ is a substituted or unsubstituted linked phenyl group in which 2 to 6 phenyl groups are linked.

[0015]

[0016] Here, X is an oxygen atom or a sulfur atom, and Y １ to Y １２ are each independently represented by C—Ra. Z 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. The aromatic hydrocarbon group or aromatic heterocyclic group in the case of linking may be the same as or different from each other.

[0017] Ra is hydrogen, deuterium, a substituent, 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] Among the above general formula (1), the formula (1a) is represented by the following formula (3a), and Ar １ , and Ar ２It is preferable that each is 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. The benzene ring described in the following formula (3a) may have a substituent, and in that case, the substituent is the same as the substituent in the case of substituting an aromatic hydrocarbon group, an aromatic heterocyclic group, and a linked aromatic group. Details of these substituents will be described later.

[0019] Here, Ar ４ and Ar ５ are a substituted or unsubstituted phenyl group or a substituted or unsubstituted linked phenyl group in which 2 to 3 phenyl groups are linked. p is the substitution number and represents an integer of 0 to 2. q is the substitution number and is an integer of 0 to 3. However, the number of substituted or unsubstituted phenyl groups contained in the formula (3a) is 2 to 6.

[0020] In the formula (3a), it is preferable that the sum of p and q is 1 to 2.

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

[0022] In the mixed material for an organic electroluminescent device of the present invention, it is preferable that at least one of the compound represented by the general formula (1) and the compound represented by the general formula (2) has a part or all of hydrogen substituted with deuterium. More preferably, the average deuteration rate is 30% or more. Furthermore, it is more preferable that both the compound represented by the general formula (1) and the compound represented by the general formula (2) are deuterated, and the average deuteration rate of each is preferably 30% or more.

[0023] The mixed material for the organic electroluminescent element is a material for manufacturing at least one layer of an organic electroluminescent element having multiple organic layers between the anode and the cathode by a vapor deposition method, and can be a premixture that has been mixed in advance before vapor deposition. In this premixture, 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 30°C or less, and preferably this difference in 50% weight loss temperature is preferably 20°C or less.

[0024] The mixed material for the organic electroluminescent element preferably has a melting point of 300°C or less for at least one of the compound represented by general formula (1) and the compound represented by general formula (2). Furthermore, the mixed material for the organic electroluminescent element preferably has a melting point of at least one of the compound represented by general formula (1) and the compound represented by general formula (2) below the 50% weight loss temperature of the compound.

[0025] The mixed material for the organic electroluminescent element can be a molten mixture obtained by melting the compound represented by general formula (1) and the compound represented by general formula (2) by heating under reduced pressure or inert gas atmosphere. In this case, the difference between the maximum emission wavelength of the fluorescence emission spectrum of the molten mixture and the maximum emission wavelength of the fluorescence emission spectrum of either the compound represented by general formula (1) or the compound represented by general formula (2) is preferably within ±50 nm, and more preferably within ±50 nm. The difference between the maximum emission wavelength of the fluorescence emission spectrum of the molten mixture and the maximum emission wavelengths of the respective fluorescence emission spectra of the compound represented by general formula (1) and the compound represented by general formula (2) is preferably within ±50 nm. The difference in these spectra is preferably within ±30 nm, more preferably within ±20 nm, and even more preferably within ±10 nm.

[0026] Furthermore, the present invention relates to an organic electroluminescent element having a plurality of organic layers between an anode and a cathode, characterized in that at least one of the organic layers contains the above-mentioned mixed material for organic electroluminescent elements.

[0027] Preferably, the organic layer containing the mixed material for the organic electroluminescent element is at least one layer selected from the group consisting of an emissive 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 more preferably, it is an emissive layer. Furthermore, if the organic layer containing the mixed material for the organic electroluminescent element is an emissive layer, it is preferable that the emissive layer contains at least one luminescent dopant, and more preferably, it contains a compound represented by general formula (1) as a first host, a compound represented by general formula (2) as a second host, and the emissive layer contains at least one luminescent dopant.

[0028] Furthermore, the present invention relates to a method for manufacturing an organic electroluminescent element having a plurality of organic layers including a light-emitting layer between an anode and a cathode, characterized in that it includes the steps of preparing the above-mentioned mixed material for organic electroluminescent elements, and forming a light-emitting layer by evaporating and depositing this mixed material from a single evaporation source.

[0029] According to the present invention, it is possible to realize a practically useful organic EL element that has high efficiency and long lifespan despite having a low driving voltage.

[0030] This is a cross-sectional view showing an example of the structure of an organic EL element.

[0031] The mixed material for organic electroluminescent devices of the present invention comprises a compound represented by general formula (1) and a compound represented by general formula (2). In an organic electroluminescent device (organic EL device) having multiple organic layers between the anode and cathode, in order to improve the characteristics of the organic EL device, it is necessary that the material used in the organic layer has high resistance to charge, and in particular, it is important to suppress the leakage of excitons and charge to the surrounding layer in the light-emitting layer. To suppress this charge / exciton leakage, for example, improving the bias of the light-emitting region in the light-emitting layer is effective, and for this purpose 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 to a desirable range.

[0032] The dual charge injection transport properties of materials used in organic layers are largely determined by the energy levels of the molecular orbitals and the magnitude of intermolecular interactions. When the mixed material for organic electroluminescent devices of the present invention is used as a material for organic EL devices, it preferably contains an indolocarbazole compound having an ortho-linked biphenyldiyl group represented by formula (3a) as formula (1a) in general formula (1), as described later. Therefore, it has particularly high electron injection transport ability, and the steric hindrance effect of the biphenyldiyl group can suppress the proximity of indolocarbazole molecules to each other. Furthermore, by changing the substituent type and bond position of the biphenyldiyl group, the intermolecular interactions of molecular orbitals that contribute greatly to electron injection transport to the light-emitting layer can be controlled at a high level.

[0033] Furthermore, when the mixed material for organic electroluminescent devices of the present invention is used as a material for organic EL devices, it is believed that it will provide an excellent organic EL device with high efficiency and long lifespan, even at low voltages, because it contains an oxygen-bridged biscarbazole compound that has an energy level that is easily injected with holes and high hole transport properties, as represented by general formula (2), and has a highly durable framework.

[0034] First, let's explain the compounds related to general formula (1). In general formula (1), ring A is a nitrogen-containing five-membered heterocycle represented by formula (1a), and this heterocycle condenses with two adjacent rings at any position, but never condenses on an edge containing nitrogen. Therefore, the indolocarbazole ring has several isomer structures, but the number is limited.

[0035] Specifically, the compound represented by general formula (1) preferably has ring A represented by formula (3a), and there are embodiments represented by any of the following formulas (5) to (10), preferably formulas (6), (8) to (10), and more preferably the structure represented by formula (10). In formulas (5) to (10), symbols common to general formula (1) have the same meaning. Ar ４ Ar ５is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked phenyl group consisting of two to three linked phenyl groups. p represents the number of substitutions, an integer from 0 to 2. q represents the number of substitutions, an integer from 0 to 3. Note that the benzene ring included in the group corresponding to formula (3a) in formulas (5) to (10) below may have substituents, and in that case, the substituents are the same as those used when substituting for aromatic hydrocarbon groups, aromatic heterocyclic groups, and linked aromatic groups as described later.

[0036] In general formula (1), Ar １ and Ar ２ Each of these is 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 the aromatic hydrocarbon groups or aromatic heterocyclic groups in the case of linking may be the same or different from each other, preferably Ar １ , and Ar ２ Each of these is 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, preferably Ar １ and Ar ２ The sum of the number of benzene rings is 5 or less, more preferably 4 or less. The biphenyl group, terphenyl group, or quaterphenyl group has a structure in which 2, 3, or 4 benzene rings are linked together, but the bond position of each benzene ring may be o-, m-, or p-. It may also be linear or branched.

[0037] In this specification, a linked aromatic group refers to an aromatic group formed by the single-bonding of aromatic rings of two or more aromatic groups selected from the group consisting of aromatic hydrocarbon groups and aromatic heterocyclic groups. These linked aromatic groups may be linear or branched. The linking position when benzene rings are linked may be ortho, meta, or para, but para linking or meta linking is preferred. The aromatic groups may be aromatic hydrocarbon groups or aromatic heterocyclic groups, and the multiple aromatic groups may be the same or different. In other words, the aromatic hydrocarbon groups or aromatic heterocyclic groups used in linking may be the same or different from each other.

[0038] R １ Each of these is 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 the aromatic hydrocarbon groups or aromatic heterocyclic groups in the linked case may be the same or different from each other. Preferably, it is 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.

[0039] a to c represent the number of substitutions, where a and c are each independent integers from 0 to 4, and b is an integer from 0 to 2. Preferably, a and c are each independent integers from 0 to 2, and b is an integer from 0 to 1.

[0040] Ar ３ Ar is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked phenyl group consisting of 2 to 6 linked phenyl groups. ３ is a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted quaterphenyl group, a substituted or unsubstituted kinkphenyl group, or a substituted or unsubstituted sexiphenyl group, preferably Ar ３The sum of the number of benzene rings is 5 or less, more preferably 4 or less. The biphenyl group, terphenyl group, quaterphenyl group, kinkphenyl group, or sexiphenyl group has a structure in which 2, 3, 4, 5, or 6 benzene rings are linked together, but the bond position of each benzene ring may be o-, m-, or p-. It may also be linear or branched. Ar ４ or Ar ５ The same applies to the linked phenyl group as described above.

[0041] Ar １ Ar ２ , and R １ In this context, specific examples of unsubstituted aromatic hydrocarbon groups having 6 to 18 carbon atoms, unsubstituted aromatic heterocyclic groups having 3 to 12 carbon atoms, or unsubstituted linked aromatic groups formed by the linking of 2 to 5 of these aromatic groups include groups derived from 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 compounds composed of 2 to 5 of these linked together. １ Preferably, the group is derived from benzene, dibenzofuran, and compounds composed of 2 to 5 of these linked together.

[0042] In this specification, aromatic hydrocarbon groups, aromatic heterocyclic groups, or linked aromatic groups may each have substituents. When substituents are present, preferred substituents are halogens, cyano groups, triarylsilyl groups, aliphatic hydrocarbon groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 5 carbon atoms, alkoxy groups having 1 to 5 carbon atoms, or diarylamino groups having 12 to 44 carbon atoms. Here, when the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear, branched, or cyclic. When the above triarylsilyl group or diarylamino group is a substituent of the aromatic hydrocarbon group, aromatic heterocyclic group, or linked aromatic group, silicon and carbon, or nitrogen and carbon, respectively, are bonded by a single bond. The number of substituents in each of the aromatic hydrocarbon group, aromatic heterocyclic group, or linked aromatic group is preferably 0 to 5, and more preferably 0 to 2. Furthermore, when calculating the number of carbon atoms in aromatic hydrocarbon groups and aromatic heterocyclic groups that have substituents, the number of carbon atoms of the substituents is not included. However, it is preferable that the total number of carbon atoms, including the number of carbon atoms of the substituents, satisfies the above range.

[0043] Specific examples of the above substituents include 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, and dipyrenylamino. Preferably, cyano, triphenylsilyl, methyl, ethyl, t-butyl, propyl, butyl, pentyl, neopentyl, hexyl, heptyl, octyldiphenylamino, naphthylphenylamino, or dinaphthylamino are used.

[0044] 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 arbitrary positions. More preferably, formula (3a) is preferred over formula (1a), having a substituted or unsubstituted o-biphenyl group on the nitrogen-containing five-membered heterocycle. p represents the number of substitutions, an integer from 0 to 2, preferably 1 to 2. q represents the number of substitutions, an integer from 0 to 3, preferably 0 to 1.

[0045] Also, Ar in equation (3a) ４ Ar ５ is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked phenyl group in which two to three phenyl groups are linked together. p represents the number of substitutions and is an integer from 0 to 2, preferably 1 to 2. q represents the number of substitutions and is an integer from 0 to 3, preferably 0 to 1. In particular, it is preferable that the sum of p and q in formula (3a) is an integer from 1 to 2.

[0046] Specific examples of general formula (1) are shown below, but the compound is not limited to these examples. In the structural formulas below, the number of s substitutions of the substituted deuterium (D) represents the average number and changes depending on the average deuteration rate.

[0047] ​​​​​​​Among these specifically illustrated example compounds, compounds 112, 118, 119, 120, 123, 124, 132, 134, 135, 140, 141, 143, 145, 148, 155, 156, 157, 158, 159, 162, 165, 168, 171, 177, 178, 179, 612, 618, 619, 620, 623, 624, 632, 634, 635, 640, 641, 643, 645, 648, 655, 656, 657, 658, 659, 662, 665, 668, 671, 677, 678, and 679 are preferred, as they exhibit high performance in terms of luminous efficiency and device lifetime, while also having high thermal stability.

[0048] Next, we will describe the compounds relating to general formula (2). In general formula (2), X is an oxygen atom or a sulfur atom, preferably oxygen. １ ~Y １２ These are each independently represented by C-Ra. １ and Z ２ Each of these is 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 formed by the linking of 2 to 5 of these aromatic groups, wherein the aromatic hydrocarbon groups or aromatic heterocyclic groups in the linked case may be the same or different from each other. Preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by the linking of 2 of these aromatic hydrocarbon groups. More preferably, it is a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted phenanthryl group, and even more preferably, an unsubstituted phenyl group or an unsubstituted biphenyl group. The biphenyl group has a structure in which two benzene rings are linked, but the bond position of each benzene ring may be any of the o-, m-, or p- positions.

[0049] 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.

[0050] Z １ Z ２ ,Specific examples of unsubstituted aromatic hydrocarbon groups having 6 to 18 carbon atoms in Ra, unsubstituted aromatic heterocyclic groups having 3 to 12 carbon atoms, or unsubstituted linked aromatic groups in which 2 to 5 of these aromatic groups are linked together include the aforementioned Ar １ Ar ２ , and R １ This is the same as the case described earlier.

[0051] Specific examples of general formula (2) are shown below, but the compound is not limited to these examples. In the structural formulas below, the number of s substitutions of the substituted deuterium (D) represents the average number and changes depending on the average deuteration rate.

[0052] Among these specifically illustrated example compounds, 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 are preferred, as they exhibit high performance in terms of luminous efficiency and device lifespan, while also having high thermal stability.

[0053] The hydrogen in the compound contained in the mixed material for organic electroluminescent devices of the present invention may be deuterium. That is, the hydrogen in the condensed ring (indolocarbazole ring) represented by general formula (1) and formula (1a), Ar １ Ar ２ Ar ３ Ar ４ Ar ５ , R １ Some or all of the hydrogen atoms in the aromatic rings and the substituents substituted on these aromatic rings may be deuterium. Also, Ra, Z in the compound represented by general formula (2) １ and Z ２ Some or all of the hydrogen atoms in the aromatic rings and the substituents that substitute for these aromatic rings may be deuterium. When deuterated, at least one of the compounds represented by general formula (1) and the compound represented by general formula (2) may have some or all of its hydrogen atoms substituted with deuterium, and both the compound represented by general formula (1) and the compound represented by general formula (2) may be deuterated.

[0054] Furthermore, if some or all of the hydrogen atoms in these compounds are deuterated, the compounds represented by general formula (1) or general formula (2) include both cases: consisting of a single compound and a mixture of two or more compounds. That is, the compounds represented by general formula (1) or general formula (2) may consist of two or more of the compounds included in these formulas, or they may be a mixture of compounds with different deuteration numbers or deuteration positions. Also, all of the compounds contained in the mixed material for organic electroluminescent devices may be deuterated, or only some of the compounds may be deuterated.

[0055] For compounds represented by general formula (1) or general formula (2), the average deuterated rate is preferably 30% or more, and more preferably 40% or more. To explain the average deuterated rate in more detail, an average deuterated rate of 50% means that, on average, half of the total hydrogen atoms are replaced with deuterium.

[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, the sample is first 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 integrated intensity ratio of 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 this ratio is subtracted from 1 to determine the average deuterated rate of the deuterated compound.

[0057] The mixed material for a mixed organic electroluminescent element of the present invention contains a compound represented by the general formula (1) and a compound represented by the general formula (2), wherein the mixing ratio (weight ratio) of the compound represented by the general formula (1) is preferably 20 to 70% by mass, and more preferably 20 to 60% by mass, relative to the total of the two.

[0058] The mixed material for the organic electroluminescent element may contain other compounds in addition to the compound represented by general formula (1) and the compound represented by general formula (2). 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) may constitute 50% by mass or more of the total, and more preferably 75% by mass or more.

[0059] The mixed material for organic electroluminescent devices of the present invention is suitable as a material or component of an organic EL device. When used as a component of an organic EL device, the mixed material for organic electroluminescent devices is included in the organic layer of the organic EL device, and this organic layer is preferably selected from the group consisting of an emissive 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, it is an emissive layer, and the emissive layer preferably contains at least one luminescent dopant.

[0060] When the light-emitting layer contains the mixed material for the organic electroluminescent element of the present invention, it is desirable that it be included as a host for the light-emitting layer. Advantageously, it is preferable to include the compound represented by general formula (1) as the first host and the compound represented by general formula (2) as the second host.

[0061] When the mixed material for organic electroluminescent elements of the present invention is used as a component of an organic EL element, it is possible to employ methods such as evaporating multiple compounds, such as the compound represented by general formula (1) and the compound represented by general formula (2), individually from different evaporation sources and then depositing them. However, it is preferable to pre-mix them to form a premixture before deposition, and then simultaneously evaporate and deposit the premixture from a single evaporation source to form an organic layer, preferably a light-emitting layer.

[0062] The aforementioned premixture is a form of the mixed material and may be prepared by mixing the compound represented by general formula (1) and the compound represented by general formula (2) in powder form, by melting and mixing them 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 general formula (1) and the compound represented by general formula (2) and may be in powder form or in thin film form. In the case of thin film form, the compound represented by general formula (1) and the compound represented by general formula (2) may be contained in the same organic layer, or they may be contained in different organic layers of the element.

[0063] Here, if the mixed material for the organic electroluminescent element in the present invention is a molten mixture of a compound represented by general formula (1) and a compound represented by general formula (2), preferably the difference between the maximum emission wavelength of the fluorescence emission spectrum of these molten mixtures and the maximum emission wavelength of the fluorescence emission spectrum of either the compound represented by general formula (1) or the compound represented by general formula (2) is within ±50 nm. More preferably, the difference between the maximum emission wavelength of the fluorescence emission spectrum of the molten mixtures and the maximum emission wavelengths of the respective fluorescence emission spectra of the compound represented by general formula (1) and the compound represented by general formula (2) is within ±50 nm. Regarding this spectral difference, including the case where it is compared with the maximum emission wavelength of the fluorescence emission spectrum of either or both of the compounds represented by general formula (1) and general formula (2), it is preferably within ±30 nm, more preferably within ±20 nm, and even more preferably within ±10 nm.

[0064] Furthermore, if the mixed material for the organic electroluminescent element in the present invention is the above-described premixture, it is preferable that the melting point of at least one of the compound represented by general formula (1) and the compound represented by general formula (2) is 300°C or lower. Moreover, it is preferable that the melting point of at least one of the compound represented by general formula (1) and the compound represented by general formula (2) is below the 50% weight loss temperature of the compound.

[0065] When forming a light-emitting layer using the above-mentioned premixture as the mixed material for the organic electroluminescent element of the present invention, the necessary luminescent dopant material or other hosts used as needed may be mixed in. However, if there is a large difference in the temperature at which the desired vapor pressure is achieved, it is preferable to deposit the luminescent dopant material or other hosts from a separate deposition source.

[0066] When the mixed material for the organic electroluminescent element of the present invention is the above-mentioned premixture, it is desirable that the compound represented by general formula (1) and the compound represented by general formula (2) have a 50% weight loss temperature of 30°C or less in order to perform stable deposition. More preferably, it is 20°C or less.

[0067] The organic EL element of the present invention has a plurality of organic layers between opposing electrodes, and at least one of the organic layers is a light-emitting layer. At least one light-emitting layer may contain the mixed material for organic electroluminescent devices as a host. When the light-emitting layer contains the mixed material for organic electroluminescent devices, it may contain at least one type of light-emitting dopant.

[0068] 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.

[0069] Figure 1 is a cross-sectional view showing a typical organic EL element structure 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 may have an exciton blocking layer adjacent to the light-emitting layer, or an electron blocking layer between the light-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 light-emitting layer, and it is also possible to insert both simultaneously. The organic EL element of the present invention has an anode, a light-emitting layer, and a cathode as essential layers, but it is also common to have a hole injection transport layer and an electron injection transport layer in addition to the essential layers, and it is also common to have a hole blocking layer between the light-emitting layer and the electron injection transport layer. Note that the hole injection transport layer means either the hole injection layer or the hole transport layer, or both, and the electron injection transport layer means either the electron injection layer or the electron transport layer, or both.

[0070] 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 shown in Figure 1. In this case as well, layers can be added or omitted as needed.

[0071] -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.

[0072] - Anode - As the anode material for organic EL elements, 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 tincture oxide (ITO), and SnO ２ Examples include conductive transparent materials such as ZnO. Alternatively, amorphous materials such as IDIXO (In2O3-ZnO), which can be used to create transparent conductive films, may also 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.

[0073] - Cathode - As the cathode material, materials consisting of metals (electron-injection metals), alloys, electrically conductive compounds, or mixtures thereof with a small work function (4 eV or less) are used. 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 ３Examples include mixtures, indium, lithium / aluminum mixtures, and rare earth metals. Among these, from the viewpoint of electron injection properties and durability against oxidation, mixtures of electron-injection metals and metalloids, which have a larger work function and are more stable, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide mixtures, lithium / aluminum mixtures, and aluminum, are preferred. Cathodes can be made by forming thin films of these cathode materials by methods such as vapor deposition or sputtering. Furthermore, 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. In addition, in order to transmit the emitted light, 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.

[0074] 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 light-transmitting.

[0075] -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 contains an emissive dopant material and a host.

[0076] The mixed material for organic electroluminescent devices of the present invention can be suitably used as a material for organic electroluminescent devices, and preferably as a host. Preferably, the compound represented by general formula (1) is used as the first host, and the compound represented by general formula (2) is used as the second host. The first host or the second host may be one type, or two or more different compounds may be used, and if necessary, one or more other known host materials may be used in combination, but the amount used should be 50% by mass or less, preferably 25% by mass or less, of the total host material.

[0077] The present invention provides a method for manufacturing an organic electroluminescent element, comprising the steps of preparing the above-mentioned premixture, evaporating the premixture from a single evaporation source, and depositing it to form an emissive layer. A more preferable method is to vaporize the premixture from a single evaporation source and deposit it. Here, the premixture is preferably a uniform mixed material for organic electroluminescent elements.

[0078] When using a pre-mixed first and second host, it is desirable that the difference in the 50% weight loss temperature (T50) is small in order to reproducibly fabricate organic EL elements with good characteristics. 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 TG-DTA measurements under reduced pressure of nitrogen gas flow (1 Pa). Around this temperature, vaporization by evaporation or sublimation is thought to occur most actively.

[0079] It is preferable that the difference in the 50% weight loss temperature is within 30°C, as this allows for the acquisition of a uniform deposited film when the premixture is vaporized and deposited from a single evaporation source. In this case, the premixture may be mixed with a luminescent dopant material necessary for forming the luminescent layer, or other hosts used as needed.

[0080] When preparing a premix by pre-mixing, a method that allows for as uniform a mixture as possible is desirable. Examples 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. The premix may be in the form of a powder, stick, or granules.

[0081] When the compounds represented by general formula (1) or general formula (2) are deuterated compounds, methods for producing them using a starting material that is fully or partially deuterated, and methods for producing them by hydrogen / deuterium exchange reactions are known. Starting materials that are fully or partially deuterated can be purchased from commercial suppliers or produced by known hydrogen / deuterium exchange reactions. Known hydrogen / deuterium exchange reactions include methods in which a non-deuterated compound is treated with deuterium gas or an equivalent thereof in the presence of a transition metal catalyst, and methods in which a non-deuterated compound is treated with a deuterating solvent (such as deuterated benzene) in the presence of an acid catalyst.

[0082] When using a phosphorescent dopant as a 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. Specifically, iridium complexes described in J.Am.Chem.Soc.2001,123,4304, JP2013-530515A, US2016 / 0049599A, US2017 / 0069848A, US2018 / 0282356A, or US2019 / 0036043A, etc., or platinum complexes described in US2018 / 0013078A, or KR2018-094482A, etc., are preferably used, but are not limited to these.

[0083] The phosphorescent dopant material may be contained in the light-emitting layer by only one type or by two or more types. The content of the phosphorescent dopant material is preferably 0.1 to 30% by mass, and more preferably 1 to 20% by mass, relative to the host material.

[0084] Phosphorescent dopant materials are not particularly limited, but specific examples include the following compounds.

[0085] ​When using a fluorescent dopant as a luminescent dopant material, the fluorescent dopant is not particularly limited, but examples 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, metal complexes of 8-quinolinol derivatives and pyromethene derivatives, various metal complexes represented by rare earth complexes and transition metal complexes, polymer compounds such as polythiophene, polyphenylene, and polyphenylene vinylene, and organosilane derivatives. Preferably, these include condensed aromatic derivatives, styryl derivatives, diketopyrrolopyrrole derivatives, oxazine derivatives, pyromethene metal complexes, transition metal complexes, or lanthanide complexes. More preferably, these include naphthalene, pyrene, chrysene, triphenylene, benzo[c]phenanthrene, benzo[a]anthracene, pentacene, perylene, fluorantene, acenaphsofluorantene, dibenzo[a,j]anthracene, dibenzo[a,h]anthracene, benzo[a]naphthalene, hexacene, naphtho[2,1-f]isoquinoline, α-naphthaphenanthidine, phenanthroxazole, quinolino[6,5-f]quinoline, benzothiophanthrene, and the like. These may have alkyl groups, aryl groups, aromatic heterocyclic groups, or diarylamino groups as substituents.

[0086] When using a thermally activated delayed fluorescence dopant as a luminescent dopant material, examples of thermally activated delayed fluorescence dopants are not particularly limited, but include 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.

[0087] Thermally activated delayed fluorescence dopant materials are not particularly limited, but specific examples include the following compounds.

[0088] The thermally activated delayed fluorescence dopant material may be contained in the light-emitting layer by one type or by two or more types. Furthermore, the thermally activated delayed fluorescence dopant may be used in mixture with phosphorescent dopants or fluorescent dopants. The content of the thermally activated delayed fluorescence dopant material is preferably 0.1 to 50% by mass, and more preferably 1 to 30% by mass, relative to the host material.

[0089] -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.

[0090] -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.

[0091] -Electron Stopping Layer- In a broad sense, the electron stopping layer functions as a hole transport layer, and by transporting holes while blocking electrons, it can improve the probability of electrons and holes recombining in the light-emitting layer.

[0092] As the material for the electron blocking layer, known electron blocking layer materials can be used, and the material for the hole transport layer described later can be used as needed. The thickness of the electron blocking layer is preferably 3 to 100 nm, and more preferably 5 to 30 nm.

[0093] -Exciton Blocking Layer- An exciton blocking layer is a layer designed to prevent excitons, generated by the recombination of holes and electrons within the light-emitting layer, from diffusing into the charge transport layer. By inserting this layer, it becomes possible to efficiently confine excitons within the light-emitting layer, thereby improving the light-emitting efficiency of the device. In devices where two or more light-emitting layers are adjacent to each other, the exciton blocking layer can be inserted between two adjacent light-emitting layers.

[0094] As the material for the exciton blocking layer, known exciton blocking layer materials can be used. Examples include 1,3-dicarbazolylbenzene (mCP) and bis(8-hydroxy-2-methylquinoline)-(4-phenylphenoxy)aluminum(III) (BAlq).

[0095] - 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.

[0096] The hole transport material has either hole injection or transport properties, or electron barrier properties, and may be either organic or inorganic. Any compound from conventionally known compounds 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, aminosubstituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. However, it is preferable to use porphyrin derivatives, arylamine derivatives and styrylamine derivatives, and more preferably arylamine derivatives.

[0097] -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.

[0098] 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-hydroxyquinoline)aluminum(III) derivatives; phosphine oxide derivatives; nitro-substituted fluorene derivatives; diphenylquinone derivatives; thiopyrandioxide derivatives; carbodiimide, phreolenylidenemethane derivatives; anthraquinodimethane and anthrone derivatives; bipyridine derivatives; quinoline derivatives; oxadiazole derivatives; benzimidazole derivatives; benzothiazole derivatives; indolocarbazole derivatives; and polymer materials that incorporate these materials into a polymer chain or use these materials as the main chain of the polymer.

[0099] The present invention will be described 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 it does not exceed the gist of the invention.

[0100] Synthesis Example 1: Compound 118 was synthesized according to the following reaction. 5 g of compound (a) was mixed with 5.6 g of compound (b), 8.6 g of tripotassium phosphate, and 100 ml of 1,3-dimethyl-2-imidazolidinone, and the mixture was 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 6.9 g of intermediate (1-1) as a white solid (72% yield).

[0101] Under a nitrogen atmosphere, 1.3 g of 60% by mass sodium hydride was added to 30 ml of N,N'-dimethylacetamide to prepare a suspension. 6 g of intermediate (1-1), dissolved in 120 ml of N,N'-dimethylacetamide, was added to this suspension and stirred for 30 minutes. 5.5 g of compound (c) was then added, and the mixture was stirred for 6 hours. The reaction solution was added to a mixture of methanol (300 ml) and distilled water (100 ml) with stirring, and the precipitated solid was filtered off. The obtained solid was purified by silica gel column chromatography and crystallization to obtain 6.2 g of compound 118 (yield 63%) as a yellow solid (APCI-TOFMS, m / z 792[M+H]+).

[0102] 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 of compound 406 as a white solid (yield 53%).

[0103] Synthesis Example 3 Compound 1-1-D was synthesized according to the following reaction. 8.4 g of compound (1-1) was mixed with 220 ml of deuterated benzene (C6D6) and 10.7 g of deuterated trifluoromethanesulfonic acid (TfOD), and the mixture was heated and stirred at 50°C for 4 hours under a nitrogen atmosphere. The reaction mixture was added to 150 ml of a heavy aqueous solution of sodium carbonate (10.2 g), rapidly cooled, separated, and purified to obtain 6.6 g of the deuterated compound (1-1-D). Note that the number of s substitutions in the substituted deuterium (D) represents the average number.

[0104] Compound 618 was synthesized according to the following reaction. Synthesis Example 4 Under a nitrogen atmosphere, 2.0 g of 60 wt% sodium hydride was added to 40 ml of N,N'-dimethylacetamide to prepare a suspension. 7.0 g of intermediate (1-1-D), dissolved in 240 ml of N,N'-dimethylacetamide, was added to this suspension and stirred for 30 minutes. 6.0 g of compound (cD) was then added, and the mixture was stirred for 6 hours. The reaction solution was added to a mixture of methanol (400 ml) and distilled water (150 ml) with stirring, and the precipitated solid was filtered off. The obtained solid was purified by silica gel column chromatography and crystallization to obtain 8.1 g of compound 618 as a yellow solid (72% yield). Note that the number of substitutions of the substituted deuterium (D) atoms represents the average number.

[0105] The average deuterated rate of compound 618 was determined by proton nuclear magnetic resonance spectroscopy. A sample was prepared by dissolving compound 618 (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 618 contained in the sample was calculated from the integrated intensity ratio derived from the internal standard and compound 618. Similarly, the average proton concentration [mol / g] of the non-deuterated compound 618 (compound 118) was also calculated. Next, the ratio of the proton concentration of compound 618 to the proton concentration of compound 118 was calculated and subtracted from 1 to obtain an average deuterated rate of 72.1% for compound 618.

[0106] Compound 470 was synthesized according to the following reaction. Synthesis Example 5 1.8 g of compound (406) was mixed with 50 ml of deuterated benzene (C6D6) and 3 g of deuterated trifluoromethanesulfonic acid (TfOD), and the mixture was heated and stirred at 50°C for 4 hours under a nitrogen atmosphere. The reaction mixture was added to 30 ml of a heavy aqueous solution of sodium carbonate (2.0 g), rapidly cooled, separated, and purified to obtain 1.2 g of compound 470, a deuteride. Note that the number of s substitutions in the substituted deuterium (D) represents the average number.

[0107] The average deuterated rate of compound 470 was determined by proton nuclear magnetic resonance spectroscopy. A 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 sample was calculated from the integrated intensity ratio derived from the internal standard and compound 470. Similarly, the average proton concentration [mol / g] of the non-deuterated compound 470 (compound 406) was also calculated. Next, the ratio of the proton concentration of compound 470 to the proton concentration of compound 406 was calculated and subtracted from 1 to determine the average deuterated rate of compound 470 as 72.5%.

[0108] Compound 465-1 was synthesized according to the following reaction. Synthesis Example 6 2.3 g of compound (401) was mixed with 50 ml of deuterated benzene (C6D6) and 3 g of deuterated trifluoromethanesulfonic acid (TfOD), and the mixture was heated and stirred at 50°C for 4 hours under a nitrogen atmosphere. The reaction mixture was added to 30 ml of a heavy aqueous solution of sodium carbonate (2.0 g), rapidly cooled, separated, and purified to obtain 1.6 g of compound 465-1, a deuteride. Note that the number of s substitutions in the substituted deuterium (D) represents the average number.

[0109] Synthesis Example 7 Compound 465-2 was synthesized according to the following reaction. To 1.6 g of compound (f), 3.7 g of deuterated bromobenzene, 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 24 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was purified by silica gel column chromatography and crystallization to obtain 1.3 g of compound (g) as a white solid. To 1.3 g of compound (g), 30 ml of deuterated benzene (C6D6) and 2 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 30 ml of a heavy aqueous solution of sodium carbonate (2.0 g), rapidly cooled, separated, and purified to obtain 0.8 g of compound 465-2, which is a deuteride. Note that the number of s substitutions of the substituted deuterium (D) represents the average number.

[0110] Synthesis Example 8 The deuterated compounds 619, 620, 641, 468-1, 468-2, 612, 623, 624, 632, 634, 635, 640, 643, 645, 648, 655, 656, 657, 662, 665, 668, 465-1, 465-2, 467, 471, and 473 were synthesized by carrying out the reaction in the same manner as in Synthesis Examples 3 to 7. The average deuterated rates of these compounds were calculated in the same manner as for 618 and 470, and the results are shown in Table 1. Note that compounds 468-1 and 468-2 have similar structures but different average deuterated rates. Similarly, compounds 465-1 and 465-2 have similar structures but different average deuterated rates.

[0111] The compounds used in the examples and comparative examples are shown below.

[0112] Example 1 A glass substrate on which an anode made of ITO with a thickness of 110 nm was formed was used to deposit each thin film by vacuum deposition at a vacuum of 4.0 × 10⁻⁶. -5 The layers were laminated using Pa. First, compound A and compound B were co-deposited onto ITO from different deposition sources to form a hole injection layer to a thickness of 10 nm. At this time, the co-deposit was performed under deposition conditions where the concentration of compound B was 3 mass%. Next, compound A was formed to a thickness of 110 nm as the first hole transport layer. Next, compound C was formed to a thickness of 10 nm as the second hole transport layer. Next, compound D was formed to a thickness of 5 nm as the electron blocking layer. Next, compound 618 was co-deposited as the first host, compound 401 as the second host, and compound E-2 as the luminescent dopant from different deposition sources to form a luminescent layer to a thickness of 40 nm. At this time, the co-deposit was performed under deposition conditions where the concentration of compound E-2 was 5 mass% and the weight ratio of the first host to the second host was 30:70. Next, compound F was formed to a thickness of 5 nm as the hole blocking layer. Next, compound G was formed to a thickness of 30 nm as the electron transport layer. Furthermore, a 1 nm thick layer of LiF was formed on the electron transport layer as an electron injection layer. Finally, an Al layer was formed on the electron injection layer as a cathode to a thickness of 70 nm to fabricate an organic EL device.

[0113] Examples 2-66, Comparative Examples 1-4 Organic EL elements were fabricated in the same manner as in Example 1, except that the compounds shown in Table 1 were used as the first and second hosts, and their mass ratios were as shown in Table 1.

[0114] Table 2 shows the evaluation results of the fabricated organic EL elements. In the table, brightness, voltage, and current efficiency are calculated using a driving current of 10 mA / cm². 2 These are values ​​over time and represent initial characteristics. LT70 is the time it takes for the brightness to decrease from an initial brightness of 9000 nits to 70%, and represents the lifetime characteristic. The numbers for the first host and second host are the numbers assigned to the example compounds above, 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 set to 100%.

[0115]

[0116]

[0117]

[0118] Examples 67-88, Comparative Examples 5-6 Organic EL elements were fabricated in the same manner as in Example 1, except that the compounds shown in Table 5 were used as the first and second hosts, and the preliminary mixture obtained by grinding and mixing them in a mortar was deposited from a single evaporation source.

[0119] The obtained organic EL elements were evaluated in the same manner as in the previous example. The results are shown in Table 5. Note that all characteristics are expressed as relative values ​​with the characteristics of Comparative Example 5 set to 100%.

[0120]

[0121] Examples 89-104, Comparative Examples 7-8: The compounds shown in Table 6 were used as the first and second hosts, and a preliminary mixture was obtained by grinding and mixing them in a mortar. The preliminary mixture was placed in a vacuum chamber, heated to 300°C under a reduced pressure of 100 Pa or less, cooled to room temperature, and then pulverized and mixed to obtain a molten mixture. An organic EL element was fabricated in the same manner as in Example 51, except that this molten mixture was deposited from a single evaporation source.

[0122] The obtained organic EL elements were evaluated in the same manner as in the previous example. The results are shown in Table 6. Note that all characteristics are expressed as relative values ​​with the characteristics of Comparative Example 7 set to 100%.

[0123]

[0124] These results show that Examples 1 to 104 exhibit longer lifespan characteristics compared to the comparative examples. Generally, efficiency and lifespan can be in a trade-off relationship, and it is difficult to improve both current efficiency and lifespan characteristics. In particular, improving lifespan leads to improvements in brightness, so if lifespan can be improved while maintaining a certain level of efficiency, a more practical device can be created. From this viewpoint, Examples 1 to 104, which use the mixed material according to the present invention, exhibit long lifespan characteristics while achieving current efficiency of 100% or more when comparing comparative examples with similar mixing ratios, compared to Comparative Examples 1 to 8, which use conventional compounds as part of the mixed host material, thus enabling the creation of organic EL devices that are advantageous in practical use.

[0125] Table 7 shows the 50% weight loss temperature (T50) and melting point (Tm) of the compounds used in the examples and comparative examples.

[0126]

[0127] The photoluminescence (PL: fluorescence emission) spectra of the powders of the molten mixture prepared in Example 96 and its constituent compounds 641 and 468-1 were measured. A spectrofluorometer (FP-6500, JASCO) was used to measure the PL spectra. The powder samples were sandwiched between two quartz substrates, and irradiated with 340 nm excitation light in the powder state. The PL spectra observed in the measurement range of 350 nm to 700 nm were measured.

[0128] In the measurements described above, the wavelength at the maximum peak was defined as the PL maximum emission wavelength, and this is summarized in Table 8.

[0129]

[0130] 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 condenses with two adjacent rings at arbitrary positions. Ar １ and Ar ２ Each of these is 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 the aromatic hydrocarbon groups or aromatic heterocyclic groups in the linked case may be the same or different from each other. １ Each of these is 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 formed by the linking of 2 to 5 of these aromatic groups, wherein the aromatic hydrocarbon groups or aromatic heterocyclic groups in the linked group may be the same or different. a to c are the number of substitutions, where a and c are independently integers from 0 to 4, and b is an integer from 0 to 2. Ar ３ This is a linked phenyl group consisting of 2 to 6 substituted or unsubstituted phenyl groups. (Here, X is an oxygen atom or a sulfur atom, and Y １ ~Y １２ These are each independently represented by C-Ra. １ and Z ２ Each of these is 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 formed by the linking of 2 to 5 of these aromatic groups. In the case of linking, 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. Among the general formula (1), the formula (1a) is represented by the following formula (3a), and Ar 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 quarterphenyl group. The hybrid material for an organic electroluminescent device according to claim 1, characterized in that. (Here, Ar ４ , Ar ５ is a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked phenyl group in which 2 to 3 phenyl groups are linked. p is the number of substitutions and represents an integer of 0 to 2. q is the number of substitutions and is an integer of 0 to 3.) 3. The mixed material for organic electroluminescent element according to claim 2, characterized in that the sum of p and q in formula (3a) is an integer between 1 and 2.

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

5. The mixed material for an organic electroluminescent element according to claim 1, wherein at least one of the compounds represented by general formula (1) and the compound represented by general formula (2) is partially or completely substituted with deuterium.

6. The mixed material for an organic electroluminescent element according to claim 5, wherein at least one of the compounds represented by general formula (1) and the compound represented by general formula (2) has some or all of its hydrogen replaced by deuterium, and its average deuteration rate is 30% or more.

7. The mixed material for an organic electroluminescent element according to claim 6, wherein both the compound represented by general formula (1) and the compound represented by general formula (2) have some or all of their hydrogen replaced by deuterium, and the average deuteration rate of both is 30% or more.

8. The mixed material for organic electroluminescent elements according to claim 1, which is used to form at least one layer of an organic electroluminescent element having a plurality of organic layers between an anode and a cathode, and is a premixed mixture prepared in advance to form the organic layer.

9. The mixed material for an organic electroluminescent element according to claim 8, characterized in that the difference in the 50% weight loss temperature between the compound represented by general formula (1) and the compound represented by general formula (2) is 30°C or less.

10. The mixed material for an organic electroluminescent element according to claim 1, characterized in that it is a molten mixture obtained by melting the compound represented by general formula (1) and the compound represented by general formula (2) by heating under reduced pressure or in an inert gas atmosphere.

11. The mixed material for an organic electroluminescent element according to claim 10, characterized in that the difference between the maximum emission wavelength of the fluorescence emission spectrum of the molten mixture and the maximum emission wavelength of the fluorescence emission spectrum of either the compound represented by general formula (1) or the compound represented by general formula (2) is within ±20 nm.

12. The mixed material for an organic electroluminescent element according to claim 1, characterized in that at least one of the compound represented by general formula (1) and the compound represented by general formula (2) has a melting point of 300°C or less.

13. The mixed material for an organic electroluminescent element according to claim 1, characterized in that the melting point of at least one of the compound represented by general formula (1) and the compound represented by general formula (2) is less than or equal to the 50% weight loss temperature of the compound.

14. An organic electroluminescent element 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 elements described in any one of claims 1 to 13.

15. The organic electroluminescent element according to claim 14, wherein the organic layer containing the mixed material for the organic electroluminescent element is at least one layer selected from the group consisting of an emissive 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.

16. The organic electroluminescent element according to claim 15, wherein the organic layer containing the mixed material for the organic electroluminescent element is an emissive layer, and comprises a compound represented by general formula (1) as a first host, a compound represented by general formula (2) as a second host, and the emissive layer contains at least one emissive dopant.

17. The organic electroluminescent device according to claim 16, characterized in that at least one compound among the first host, the second host, and the luminescent dopant has some or all of its hydrogen atoms replaced with deuterium.

18. The organic electroluminescent device according to claim 17, characterized in that at least two compounds among the first host, the second host, and the luminescent dopant have some or all of their hydrogen atoms replaced with deuterium.

19. The organic electroluminescent element according to claim 18, characterized in that the first host, the second host, and the luminescent dopant are partially or entirely replaced with deuterium.

20. A method for manufacturing an organic electroluminescent element having a plurality of organic layers including a light-emitting layer between an anode and a cathode, characterized by comprising the steps of preparing a mixed material for organic electroluminescent elements according to any one of claims 8 to 13, and depositing the mixed material for organic electroluminescent elements from a single evaporation source to form a light-emitting layer.

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