Material for organic electroluminescent element and organic electroluminescent element

Abstract

To provide: a material for an organic electroluminescent element with which it is possible to obtain an organic EL element that emits light at a high efficiency while being driven at a low voltage, has long life characteristics, and is practically useful; and an organic electroluminescent element obtained by using the same.　This mixed material for an organic electroluminescent element contains a compound represented by general formula (1) and a cyclic azine compound represented by general formula (10). This organic electroluminescent element is formed by using the mixed material. m represents the number of repetitions and is 2 or 3. Ar1 is, inter alia, a substituted or unsubstituted aromatic hydrocarbon group having 6-20 carbon atoms, and R2-R7 are, inter alia, each independently hydrogen or a substituted or unsubstituted aromatic hydrocarbon group having 6-20 carbon atoms. Ar2 and Ar3 are, inter alia, each independently a substituted or unsubstituted aromatic hydrocarbon group having 6-20 carbon atoms, and L1 is a single bond or a substituted or unsubstituted phenyl group.

Description

Mixed material for organic electroluminescent device and organic electroluminescent device

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

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

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

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

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

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

[0007] Furthermore, Patent Document 3 discloses a device using a mixed host of a compound having a plurality of linked carbazoles and a compound having an indolocarbazole skeleton.

[0008] Furthermore, Patent Document 4 discloses a device using a mixed composition containing a compound having a carbazole skeleton and a cyclic azine compound.

[0009] Furthermore, Patent Documents 5 to 8 disclose elements using a mixed composition containing a compound having a carbazole skeleton and a compound having a triazine skeleton.

[0010] WO2010 / 134350 publication WO2011 / 070963 publication WO2016 / 158191 publication WO2022 / 45272 publication WO2021 / 200252 publication WO2020 / 218188 publication WO2021 / 065492 publication WO2012 / 077520 publication

[0011] Kim et al., Sci. Adv. 8, eabq1641 (2022)

[0012] In order to apply organic EL elements as display elements or light sources for flat panel displays and the like, it is necessary to improve the luminous efficiency of the elements and at the same time ensure sufficient stability during operation. However, these cannot be achieved with materials consisting of combinations of conventionally known compounds.

[0013] The present invention has been made in view of the above-mentioned circumstances, and aims to provide a material for organic electroluminescence devices that can provide practically useful organic EL devices that emit light with high efficiency and have long life characteristics while being driven at a low voltage. Another aim of the present invention is to provide an organic EL device using such a material.

[0014] That is, the present invention provides a mixed material for an organic electroluminescent device, characterized by containing a compound represented by the following general formula (1) and a cyclic azine compound represented by the following general formula (10): Note that, although the mixed material contains a compound represented by general formula (1) and a compound represented by general formula (10), the compounds represented by general formula (1) and general formula (10) are not the same compound at the same time. Here, m is the number of repetitions and represents 2 or 3. １ represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups. ２ ~R ７ each independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and aromatic heterocyclic groups. １ , and R ２ ~R ７ does not contain carbazole. In addition, some or all of the hydrogen atoms in the compound represented by general formula (1) may be substituted with deuterium atoms. Here, Ar ２ and Ar ３each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. １ represents a single bond or a substituted or unsubstituted phenyl group. Some or all of the hydrogen atoms in the compound represented by the general formula (10) may be substituted with deuterium atoms.

[0015] The compound represented by the general formula (1) preferably contains at least one bond structure represented by any of the following formulas (2) to (7), and more preferably contains at least two. Note that some or all of the hydrogen atoms in the bond structures represented by the formulas (2) to (7) may be substituted with deuterium. Furthermore, "*" in the formula indicates carbazole or Ar in the general formula (1). １ Furthermore, the carbazoles described in the following formulas (2) to (7) are each a bond position of R ２ ~R ７ It may have a substituent corresponding to:

[0016] L in the general formula (10) １ is preferably a single bond.

[0017] The present invention also relates to an organic electroluminescent device comprising one or more organic layers between opposing anode and cathode, wherein at least one of the organic layers contains the above-described mixed material for organic electroluminescent devices. The organic layer in this organic electroluminescent device may contain the compound represented by the general formula (1) and the compound represented by the general formula (10). These compounds may be supplied individually to the organic layer, or may be supplied as a premix in which the compound represented by the general formula (1) and the compound represented by the general formula (10) are mixed in advance, i.e., as a mixed composition for organic electroluminescent devices.

[0018] In the organic electroluminescent device of the present invention, the organic layer containing the mixed material for organic electroluminescent device is an emitting layer, and the emitting layer preferably contains a thermally activated delayed fluorescent material, and more preferably the thermally activated delayed fluorescent material contains a boron atom.

[0019] In the organic electroluminescent device of the present invention, the organic layer containing the mixed material for an organic electroluminescent device is an emitting layer, and the emitting layer preferably contains a phosphorescent material, and more preferably the phosphorescent material contains a platinum atom.

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

[0021] Furthermore, the present invention is a method for producing an organic electroluminescent device having a plurality of organic layers between an anode and a cathode, one of the organic layers being an emitting layer, and it is preferable that the emitting layer is produced by depositing the mixed material for organic electroluminescent devices of the present invention from a single deposition source.

[0022] According to the present invention, it is possible to obtain a practically useful organic EL element that emits light with high efficiency and has a long life, while being driven at a low voltage.

[0023] FIG. 1 is a cross-sectional view showing an example of the structure of an organic EL element used in the present invention.

[0024] The compound represented by formula (1) and the compound represented by formula (10) in the present invention will be described in detail below.

[0025] First, general formula (1) is as described above, and m is the number of repetitions and represents 2 or 3, preferably 2.

[0026] Ar １represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. Preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. More preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups. However, Ar １ does not contain carbazole.

[0027] Also, R ２ ~R ７ each independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. Preferably, they represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. More preferably, they represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups. However, R ２ ~R ７ does not contain carbazole. Note that part or all of the hydrogen atoms in the compound represented by general formula (1) may be substituted with deuterium atoms.

[0028] The compound represented by general formula (1) preferably contains at least one bond structure represented by any of the above formulas (2) to (7), more preferably at least two. Among these, the compound represented by general formula (1) preferably contains at least one bond structure represented by formula (2) or (3), at least one bond structure represented by formula (4) or (5), or at least one bond structure represented by formula (6) or (7). Note that some or all of the hydrogen atoms in the bond structures represented by formulas (2) to (7) may be substituted with deuterium. Furthermore, * in the formula represents carbazole or Ar in the general formula (1). １ The bond position is shown.

[0029] As for the other general formula (10), as described above, Ar ２ and Ar ３ each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. Preferably, each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. More preferably, each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups. １ represents a single bond or a substituted or unsubstituted phenyl group, preferably a single bond. Note that some or all of the hydrogen atoms in the compound represented by general formula (10) may be substituted with deuterium atoms.

[0030] The above-mentioned Ar １ and R ２ ~R ７Specific examples of the unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, the unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or the unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, Examples of such aromatic groups include groups derived from thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, or dibenzoselenophene, and linked aromatic groups in which 2 or 3 of these aromatic groups are linked together. Preferred examples include groups derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, or dibenzoselenophene, and linked aromatic groups in which 2 to 3 of these aromatic groups are linked together. More preferred are groups derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, or fluorene, or linked aromatic groups in which 2 or 3 of these aromatic groups are linked together.

[0031] The above-mentioned Ar ２ and Ar ３ Specific examples of the unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, the unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or the unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group include the above-mentioned Ar except that the aromatic heterocyclic group has 2 to 17 carbon atoms. １ and R ２ ~R ７ Preferred examples include groups derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole, and linked aromatic groups in which 2 or 3 of these aromatic groups are linked together. More preferred are groups derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, or carbazole, or linked aromatic groups in which 2 or 3 of these aromatic groups are linked together.

[0032] In this specification, except for the compound represented by general formula (1), the unsubstituted 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, alkyl group having 1 to 10 carbon atoms, triarylsilyl group having 9 to 30 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. Furthermore, the unsubstituted triarylsilyl group may have a substituent, and in this case, the substituent is deuterium or alkyl group having 1 to 10 carbon atoms, and is substituted at the aryl moiety of the triarylsilyl group.

[0033] The number of substituents is 0 to 5, preferably 0 to 2. When an aromatic hydrocarbon group, an aromatic heterocyclic group, or a linking aromatic group has a substituent, the number of carbon atoms in the substituent is not included in the calculation of the number of carbon atoms. However, it is preferable that the total number of carbon atoms, including the number of carbon atoms in the substituent, falls within the above range.

[0034] Specific examples of the substituent include deuterium, cyano, bromo, fluorine, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, triphenylsilyl, biphenyldiphenylsilyl, bisbiphenylphenylsilyl, trisbiphenylsilyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, etc. Preferred are deuterium, cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, and triphenylsilyl.

[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 are linked by a single bond. These linking aromatic groups may be linear or branched. The linking position when the benzene rings are linked may be ortho, meta, or para, but para- or meta-linking is 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.

[0036] The mixed material for organic electroluminescent elements in the present invention may be in the form of a powder, solid, or thin film, so long as it contains a compound represented by general formula (1) and a compound represented by general formula (10). For example, when this material is used to form a light-emitting layer of an organic EL element, the compound represented by general formula (1) and the compound represented by general formula (10) may be supplied to the light-emitting layer individually, or the compound represented by general formula (1) and the compound represented by general formula (10) may be supplied as a premix in which they are mixed in advance, i.e., as a mixed composition for organic electroluminescent elements. Among these, it is preferable to use a premix in which the compound represented by general formula (1) and the compound represented by general formula (10) are mixed in advance (i.e., a mixed composition for organic electroluminescent elements).

[0037] The premix (mixed composition) is one 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 (10) in powder form, by melt-mixing by heating under reduced pressure or in an inert gas atmosphere such as nitrogen, or by sublimating the mixed compounds together. On the other hand, the mixed material contains the compound represented by the general formula (1) and the compound represented by the general formula (10), and may be in powder form or in thin film form. In the thin film form, the compound represented by the general formula (1) and the compound represented by the general formula (10) may be contained in the same organic layer or in different organic layers of a device. For example, the compound represented by the general formula (1) may be contained in an electron-blocking layer, and the compound represented by the general formula (10) may be contained in an emitting layer.

[0038] Regarding the mixed material for organic electroluminescent elements in the present invention, the mixing ratio (mass ratio) of the compound represented by the general formula (1) to the compound represented by the general formula (10) in the material is preferably 40 to 90 mass %, more preferably 50 to 90 mass %, and even more preferably 60 to 90 mass %, of the compound represented by the general formula (1) relative to the total of the compound represented by the general formula (1) and the compound represented by the general formula (10).

[0039] Specific examples of the compound represented by formula (1) are shown below, but the present invention is not limited to these exemplary compounds.

[0040] Specific examples of the compound represented by formula (10) are shown below, but the present invention is not limited to these exemplary compounds.

[0041] By forming an organic layer using a mixed material for an organic electroluminescent device containing the compound represented by the general formula (1) and the compound represented by the general formula (10), it is possible to obtain an organic EL device that emits light with high efficiency and has long life characteristics and is excellent for practical use.

[0042] The organic EL device preferably has at least one organic layer that is an emitting layer, and the emitting layer contains the mixed material for organic electroluminescent devices according to the present invention. The emitting layer preferably further contains a thermally activated delayed fluorescent material or a phosphorescent material, and more preferably contains a thermally activated delayed fluorescent material in the emitting layer.

[0043] That is, an excellent organic EL device can be obtained by incorporating at least one host material in the light-emitting layer together with the thermally activated delayed fluorescent material or the phosphorescent material as necessary, and it is preferable that at least one host material is the mixed material for organic electroluminescent devices according to the present invention.

[0044] In this case, as described above, the compound represented by the general formula (1) and the compound represented by the general formula (10) are each made into powders and premixed in advance, or these powders are premixed in advance by heating and melting them to form a mixed composition for organic electroluminescent elements (premixture), and this mixed composition is used to perform vapor deposition from a single vapor deposition source, thereby making it possible to produce a light-emitting layer for an organic EL element.

[0045] 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.

[0046] 1 is a cross-sectional view showing an example of the structure of a general organic EL element used in the present invention, in which 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents a light-emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. The organic EL element of the present invention has an anode, a light-emitting layer, and a cathode as essential layers, but may also have a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the essential layers, and may further have an electron blocking layer between the hole transport layer and the light-emitting layer, and a hole blocking layer between the light-emitting layer and the electron transport layer.

[0047] 1 , it is also possible to laminate the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, hole injection layer 3, and anode 2 in this order on the substrate 1, and in this case too, layers can be added or omitted as necessary. In the organic EL element described above, layers constituting the laminated structure on the substrate other than electrodes such as the anode and cathode may be collectively referred to as organic layers.

[0048] 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.

[0049] Anode: Anode materials for organic EL devices are preferably metals, alloys, electrically conductive compounds, or mixtures thereof, each having a large work function (4 eV or more). Specific examples of such electrode materials include metals such as Au, CuI, indium tin oxide (ITO), and SnO. ２ Examples of suitable conductive transparent materials include ZnO and ZnO. Amorphous materials, such as IDIXO (In2O3-ZnO), that can be used to fabricate transparent conductive films, may also be used. The anode may be formed by depositing a thin film of these electrode materials using methods such as vapor deposition or sputtering, followed by forming a desired pattern using photolithography. Alternatively, if pattern precision is not required (approximately 100 μm or greater), a pattern may be formed using a mask of the desired shape during vapor deposition or sputtering of the electrode material. Alternatively, when using a coatable material such as an organic conductive compound, wet film formation methods such as printing or coating can be used. When extracting light from this anode, a transmittance of greater than 10% is desirable, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness, depending on the material, is typically selected in the range of 10 to 1,000 nm, preferably 10 to 200 nm.

[0050] - Cathode - On the other hand, the cathode material is made of a metal (called an electron injecting metal), alloy, electrically conductive compound, or a mixture thereof, each of which has a small work function (4 eV or less). Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, and aluminum / aluminum oxide (Al ２ O ３ Among these, in view of electron injection property and durability against oxidation, etc., mixtures of an electron injection metal and a second metal which is a metal having a larger and more stable work function than the electron injection metal, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ２ O３ ) mixture, lithium / aluminum mixture, aluminum, etc. are suitable. The cathode can be produced by forming a thin film of these cathode materials by methods such as vapor deposition or sputtering. The cathode preferably has a sheet resistance of several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit emitted light, it is advantageous if either the anode or cathode of the organic EL element is transparent or semitransparent, as this improves the luminance of the emitted light.

[0051] Furthermore, a transparent or semitransparent cathode can be fabricated by forming the above-mentioned metal as a cathode with a film thickness of 1 to 20 nm and then forming the conductive transparent material described in the description of the anode thereon. This can be applied to fabricate an element in which both the anode and cathode are transparent.

[0052] -Light-emitting layer- The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and cathode, respectively. The light-emitting layer may be a single layer or multiple layers, and each layer contains an organic light-emitting dopant material and a host material.

[0053] The light-emitting layer may contain only one type of organic light-emitting dopant, or may contain two or more types of organic light-emitting dopant. The content of the organic light-emitting dopant is preferably 0.1 to 50% by mass, more preferably 0.1 to 40% by mass, based on the host material.

[0054] When a phosphorescent dopant is used as the organic light-emitting dopant material, the phosphorescent dopant preferably contains an organometallic complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Specifically, the iridium complexes described in J. Am. Chem. Soc. 2001, 123, 4304 and JP-A-2013-530515 and the platinum complexes described in Adv. Mater. 2014, 26, 7116 and JP-A-2018-2722 are preferably used, but are not limited thereto.

[0055] The phosphorescent dopant material is not particularly limited, but specific examples include the following.

[0056]

[0057] When a fluorescent dopant is used as the light-emitting dopant material, the fluorescent dopant is not particularly limited, but examples thereof include fused polycyclic aromatic derivatives, styrylamine derivatives, fused-ring amine derivatives, boron-containing compounds, pyrrole derivatives, indole derivatives, and carbazole derivatives. Among these, fused-ring amine derivatives, boron-containing compounds, and carbazole derivatives are preferred. Examples of fused-ring amine derivatives include diaminepyrene derivatives, diaminochrysene derivatives, diaminoanthracene derivatives, diaminofluorenone derivatives, and diaminofluorene derivatives having one or more fused benzofuro skeletons. Examples of boron-containing compounds include pyrromethene derivatives and polycyclic aromatic compounds described in WO2015 / 102118 and the like.

[0058] The fluorescent dopant material is not particularly limited, but specific examples include the following.

[0059]

[0060] When a thermally activated delayed fluorescent dopant is used as the luminescent dopant material, the thermally activated delayed fluorescent dopant is not particularly limited, but examples thereof include those containing a boron atom, metal complexes such as tin complexes and copper complexes, cyanobenzene derivatives and carbazole derivatives described in Nature 2012,492,234, phenazine derivatives, oxadiazole derivatives, triazole derivatives, sulfone derivatives, phenoxazine derivatives, and acridine derivatives described in Nature Photonics 2014,8,326, and polycyclic aromatic compounds described in WO2015 / 102118, etc.

[0061] The thermally activated delayed fluorescent dopant material is not particularly limited, but specific examples include the following: A cyclic azine compound may be used as the thermally activated delayed fluorescent dopant material, but it is preferable that the compound is not a compound represented by the general formula (10).

[0062]

[0063] The host material in the light-emitting layer is preferably a compound represented by the general formula (1) and / or the general formula (10). When the compound represented by the general formula (1) or the general formula (10) is used in any organic layer other than the light-emitting layer, the compound represented by the general formula (1) or the general formula (10) may or may not be contained in the light-emitting layer. In this case, the light-emitting layer may also contain a known host material used in phosphorescent or fluorescent light-emitting devices. A plurality of known host materials may be used in combination, or each may be used alone. Usable known host materials are compounds having hole-transporting and electron-transporting capabilities and a high glass transition temperature, and preferably have a triplet excitation energy (T1) greater than that of the light-emitting dopant material. A TADF-active compound may also be used as the host material. In this case, a compound having a difference between the singlet excitation energy (S1) and the triplet excitation energy (T1) (ΔEST = S1 - T1) of 0.20 eV or less is preferred. The compound represented by the general formula (1) may be contained alone as a host material in the light-emitting layer, and other known host materials may be used in combination, but in order to improve the properties of the organic EL device, it is necessary to use the compound represented by the general formula (10) in combination as a host material. Furthermore, in addition to the compound represented by the general formula (10), two or more known host materials may be used in combination.

[0064] Here, S1 and T1 are measured as follows: A film is deposited on a quartz substrate by vacuum deposition at a vacuum level of 10 －４A sample compound (thermally activated delayed fluorescent material) is vapor-deposited under conditions of 0.1 Pa or less to form a vapor-deposited film with a thickness of 100 nm. S1 is calculated by measuring the emission spectrum of this vapor-deposited film, drawing a tangent to the rising edge on the short wavelength side of the emission spectrum, and substituting the wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis into the following formula (i): S1 [eV] = 1239.85 / λedge (i)

[0065] On the other hand, T1 is calculated by measuring the phosphorescence spectrum of the vapor-deposited film, drawing a tangent to the rising edge on the short wavelength side of this phosphorescence spectrum, and substituting the wavelength value λedge [nm] at the intersection of this tangent line and the horizontal axis into the following formula (ii): T1 [eV] = 1239.85 / λedge (ii)

[0066] Known host materials can be selected from numerous patent documents, etc. Specific examples of the host material include, but are not limited to, indole compounds, carbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, triazole compounds, oxazole compounds, oxadiazole compounds, imidazole compounds, phenylenediamine compounds, arylamine compounds, anthracene compounds, fluorenone compounds, stilbene compounds, triphenylene compounds, carborane compounds, porphyrin compounds, phthalocyanine compounds, metal complexes of 8-quinolinol compounds, metal phthalocyanines, various metal complexes typified by metal complexes of benzoxazole and benzothiazole compounds, polymer compounds such as poly(N-vinylcarbazole) compounds, aniline copolymer compounds, thiophene oligomers, polythiophene compounds, polyphenylene compounds, polyphenylenevinylene compounds, and polyfluorene compounds. Preferred examples include carbazole compounds, indolocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, anthracene compounds, triphenylene compounds, carborane compounds, and porphyrin compounds.

[0067] The known host is not particularly limited, but specific examples include the following:

[0068] When multiple types of hosts are used, each host can be vapor-deposited from a different vapor deposition source, or multiple types of hosts can be simultaneously vapor-deposited from one vapor deposition source by premixing them before vapor deposition to form a premixture.

[0069] In the case where a plurality of types of hosts are used, the host is preferably the mixed composition for organic electroluminescent devices (preliminary mixture) obtained by mixing the compound represented by the general formula (1) and the compound represented by the general formula (10).

[0070] When two types of hosts are premixed, the 50% weight loss temperature (T 50 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. It is believed that vaporization by evaporation or sublimation occurs most actively around this temperature.

[0071] The difference between the 50% weight loss temperatures of the two types of hosts in the premix is ​​preferably within 20°C. By vaporizing and depositing this premix from a single evaporation source, a uniform deposited film can be obtained. In this case, a luminescent dopant material required for forming the emitting layer or other hosts to be used as needed may be mixed into the premix. However, if there is a large difference in the temperatures at which the desired vapor pressure is achieved, it is preferable to deposit them from different evaporation sources.

[0072] When two types of hosts are used, the mixing ratio (mass ratio) of the first host to the second host is preferably 40 to 90%, more preferably 50 to 90%, and even more preferably 60 to 90% of the total of the first host and the second host. When the compound represented by the general formula (1) is used as the host, the first host is the compound represented by the general formula (1), and the compound represented by the general formula (10) is the second host.

[0073] As described above, the premixing method is preferably a method that allows mixing as uniformly as possible, and examples of the premixing method include pulverization and mixing, heating and melting under reduced pressure or in an inert gas atmosphere such as nitrogen, and sublimation, but are not limited to these methods.

[0074] The host and its premixture may be in the form of a powder, stick, or granules.

[0075] 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.

[0076] -Hole Blocking Layer- In a broad sense, the hole blocking layer functions as an electron transport layer and is made of a hole blocking material that has the function of transporting electrons but has a significantly low ability to transport holes. By transporting electrons while blocking holes, the probability of electron and hole recombination in the light-emitting layer can be improved. Known hole blocking materials can be used for the hole blocking layer. Multiple hole blocking materials may also be used in combination.

[0077] -Electron Blocking Layer- In a broad sense, the electron blocking layer functions as a hole transport layer, and by transporting holes while blocking electrons, it is possible to improve the probability of electrons and holes recombining in the light-emitting layer. As the material for the electron blocking layer, it is preferable to use the compound represented by the general formula (1) or the mixed material, but known electron blocking layer materials can also be used. When the compound represented by the general formula (1) or the mixed material is used in the electron blocking layer, the host material may be the compound represented by the general formula (1), the known host materials described above, or a host material obtained by combining two or more of these.

[0078] Layers adjacent to the light-emitting layer include a hole-blocking layer and an electron-blocking layer, but if these layers are not provided, a hole-transporting layer, an electron-transporting layer, etc. will be the adjacent layers.

[0079] -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.

[0080] The hole transport material has either hole injection or transport properties or electron barrier properties, and may be either organic or inorganic. Any hole transport material can be selected from conventionally known compounds. Examples of such hole transport materials include porphyrin derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

[0081] - 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.

[0082] The electron transport material (which may also serve as a hole blocking material) may have the function of transporting electrons injected from the cathode to the light-emitting layer. The electron transport layer may be formed from any of conventionally known compounds, including polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline; tris(8-quinolinolato)aluminum(III) derivatives; phosphine oxide derivatives; nitro-substituted fluorene derivatives; diphenylquinone derivatives; thiopyran dioxide derivatives; carbodiimide derivatives; 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.

[0083] When the organic EL element of the present invention is produced, the method for forming each layer is not particularly limited, and the layers may be produced by either a dry process or a wet process.

[0084] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0085] The compounds used in the examples and comparative examples are listed below.

[0086] Comparative Example 1 On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the thin films shown below was deposited by vacuum deposition at a vacuum degree of 4.0 × 10 －５ The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Then, the aforementioned compound (1-42) was co-deposited as a host, BD-2 as a phosphorescent dopant, and BD-1 as a thermally activated delayed fluorescent dopant from different deposition sources to form an emitting layer having a thickness of 40 nm. The co-deposition was carried out under deposition conditions such that the BD-2 concentration was 13% by mass and the BD-1 concentration was 0.4% by mass. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby completing the organic EL element according to Comparative Example 1.

[0087] Comparative Example 2 As shown in Table 1, an organic EL device was prepared in the same manner as in Comparative Example 1, except that the host was changed to HT-2.

[0088] Example 1 On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the thin films shown below was deposited by vacuum deposition at a vacuum degree of 4.0 × 10 －５The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Then, the aforementioned compound (1-30) as a first host, the aforementioned compound (2-49) as a second host, BD-2 as a phosphorescent dopant, and BD-1 as a thermally activated delayed fluorescent dopant were co-deposited from different deposition sources to form an emitting layer having a thickness of 40 nm. The co-deposition was carried out under deposition conditions of a BD-2 concentration of 13 mass %, a BD-1 concentration of 0.4 mass %, and a mass ratio of the first host to the second host of 50:50. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed to a thickness of 1 nm as an electron injection layer on the electron transport layer. Finally, aluminum (Al) was formed to a thickness of 70 nm as a cathode on the electron injection layer, thereby producing the organic EL device according to Example 1. The evaluation results are shown in Table 2.

[0089] Examples 2 to 23 and Comparative Examples 3 to 9 Organic EL devices were prepared in the same manner as in Example 1, except that the electron-blocking layer material, first host, and second host were compounds shown in Table 1. The evaluation results are shown in Table 2.

[0090]

[0091]

[0092] When an external power source was connected to the organic EL elements obtained in the Examples and Comparative Examples and a DC voltage was applied, an emission spectrum with a maximum emission wavelength of 450 nm to 480 nm was observed in all of the organic EL elements, demonstrating that light emission was obtained from BD-1. From the results of the Examples and Comparative Examples shown in Table 2, it can be seen that organic EL elements using the mixed material for organic electroluminescent elements of the present invention as a host in the light-emitting layer emit blue light and have the characteristics of low voltage, high efficiency, and long life. The voltage and power efficiency in the table are measured at a driving current of 2.5 mA / cm. ２ The values ​​are those at the time of driving current 4.0 mA / cm and are the initial characteristics. ２The time required for the luminance to decay to 97% of the initial luminance at 100% is used to indicate the lifespan characteristics. The luminescent color was confirmed by the emission spectrum of the organic electroluminescence element.

[0093] Comparative Example 10: On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the thin films shown below was deposited by vacuum deposition at a vacuum degree of 4.0×10 －５ The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Then, compound (1-42) as a first host and BD-2 as a phosphorescent dopant were co-deposited from different deposition sources to form an emitting layer having a thickness of 40 nm. The co-deposition was performed under deposition conditions such that the concentration of BD-2 was 13% by mass. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby producing an organic EL device according to Comparative Example 10. The evaluation results are shown in Table 4.

[0094] Comparative Example 11 An organic EL device was prepared in the same manner as in Comparative Example 10, except that the host was changed to HT-2 as shown in Table 3. The evaluation results are shown in Table 4.

[0095] Examples 24 to 46 and Comparative Examples 12 to 18 Organic EL devices were prepared in the same manner as in Comparative Example 10, except that the electron-blocking layer material, first host, and second host were compounds shown in Table 3. The evaluation results are shown in Table 4.

[0096]

[0097]

[0098] From the results of the Examples and Comparative Examples shown in Table 4, it can be seen that the organic EL device using the mixed material for organic electroluminescent devices of the present invention as a host in the light-emitting layer emits blue light and has the characteristics of low voltage, high efficiency, and long life. Note that various evaluations were performed in the same manner as described above, and an emission spectrum with a maximum emission wavelength of 450 nm to 480 nm was observed, indicating that light emission from BD-2 was obtained.

[0099] According to the present invention, it is possible to obtain a practically useful organic EL element that emits light with high efficiency and has a long life, while being driven at a low voltage.

[0100] 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 cyclic azine compound represented by the following general formula (10): (where m is the number of repetitions and represents 2 or 3. １ represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. ２ ~R ７ each independently represents hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups, provided that Ar １ , and R ２ ~R ７ does not contain carbazole. In addition, a part or all of the hydrogen atoms in the compound represented by the general formula (1) may be replaced with deuterium atoms. (wherein, Ar ２ and Ar ３ each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. １ represents a single bond or a substituted or unsubstituted phenyl group. A part or all of the hydrogen atoms in the compound represented by the general formula (10) may be substituted with deuterium atoms.

2. The mixed material for organic electroluminescent devices according to claim 1, characterized in that the compound represented by the general formula (1) contains at least one bond structure represented by any one of the following formulas (2) to (7): (Part or all of the hydrogen atoms in the bond structures represented by formulas (2) to (7) may be replaced with deuterium atoms. * represents carbazole or Ar in the general formula (1). １ The bond position with is shown.) 3. The mixed material for organic electroluminescent devices according to claim 1, characterized in that the compound represented by the general formula (1) contains at least one bond structure represented by the formula (2) or (3).

4. The mixed material for organic electroluminescent devices according to claim 1, characterized in that the compound represented by the general formula (1) contains at least one bond structure represented by the formula (4) or (5).

5. The mixed material for organic electroluminescent devices according to claim 1, characterized in that the compound represented by the general formula (1) contains at least one bond structure represented by the formula (6) or (7).

6. The mixed material for organic electroluminescent devices according to claim 1, characterized in that the compound represented by the general formula (1) contains at least two of the bonding structures represented by the formulas (2) to (7).

7. L in the general formula (10) １ The mixed material for an organic electroluminescent device according to claim 1, characterized in that is a single bond.

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

9. The organic electroluminescent device according to claim 8, wherein the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and the emitting layer contains a thermally activated delayed fluorescent material.

10. The organic electroluminescent device according to claim 9, wherein the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and the emitting layer contains a thermally activated delayed fluorescent material containing boron atoms.

11. The organic electroluminescent device according to claim 8, wherein the organic layer containing the mixed material for organic electroluminescent devices is a light-emitting layer, and the light-emitting layer contains a phosphorescent material.

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

13. The organic electroluminescent device according to claim 8, wherein the organic layer containing the mixed material for organic electroluminescent devices is an emitting layer, and the emitting layer contains a thermally activated delayed fluorescent material containing boron atoms and a phosphorescent material containing platinum atoms.

14. The organic electroluminescent device according to any one of claims 8 to 13, wherein the light-emitting layer contains the mixed material for organic electroluminescent devices according to claim 1 as a mixed host material.

15. A method for producing an organic electroluminescent device having a plurality of organic layers between an anode and a cathode, one of the organic layers being a light-emitting layer, comprising the steps of: preparing a preliminary mixture using the mixed material for organic electroluminescent devices according to claim 1; and depositing this preliminary mixture from a single deposition source to produce a light-emitting layer.

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