WO2025105314A1 - Organic electroluminescent element mixed material and organic electroluminescent element - Google Patents

Abstract

The present invention provides: a practically useful organic electroluminescent element material having low voltage, high efficiency, and long life characteristics; and an organic electroluminescent element using the same.　The organic electroluminescent element material is represented by general formula (1). In the formula, a and b represent the number of substitutions with a representing 1-5 and b representing 1-4. Also, m represents the number of repetitions and represents 1 or 2. Ar⁰ and Ar¹ each independently represent hydrogen, a phenyl group, or the like. R² to R⁷ each independently represent hydrogen, an aromatic hydrocarbon group having 6-20 carbon atoms, an aromatic heterocyclic group having 2-20 carbon atoms, or the like. However, R² to R⁷ does not contain carbazole. Part or all of the hydrogen in the compound represented by general formula (1) may be substituted with deuterium.

Description

Mixed material for organic electroluminescent device and organic electroluminescent device

The present invention relates to organic electroluminescent devices (referred to as organic EL devices) that can convert electrical energy into light, and to materials for organic electroluminescent devices used therein.

By applying a voltage to an organic EL element, holes are injected from the anode and electrons are injected 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, 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.

In recent years, technology to extend the life of phosphorescent organic EL elements has advanced, and they are beginning to be applied to displays for mobile phones and other devices. However, when it comes 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 both highly efficient and have a long life.

More recently, highly efficient delayed fluorescence organic EL elements that utilize delayed fluorescence have been developed. For example, Patent Document 1 discloses an organic EL element that utilizes 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 it is believed that the internal quantum efficiency can theoretically be increased to 40%. However, since the efficiency is lower than that of phosphorescent organic EL elements, further improvements in efficiency are required.

On the other hand, Patent Document 2 discloses an organic EL element that utilizes the thermally activated delayed fluorescence (TADF) mechanism. The TADF mechanism utilizes the phenomenon in which reverse intersystem crossing occurs from triplet excitons to singlet excitons in materials with a small energy difference between the singlet and triplet levels, and is believed to be able to theoretically increase the internal quantum efficiency to 100%.

Here, Non-Patent Document 1 discloses an element that uses a specific mixed host (SiTrz2Cz and SiCzCz) in addition to a specific phosphorescent dopant, TADF dopant.

Patent Document 3 also discloses an element that uses a mixed host of a compound with multiple linked carbazoles and a compound with an indolocarbazole skeleton.

Furthermore, Patent Document 4 discloses an element that uses a mixed material that includes a compound containing a carbazole skeleton and a cyclic azine compound.

Furthermore, Patent Documents 5 to 8 disclose elements that use a mixed material containing a compound having a carbazole skeleton and a compound having a triazine skeleton.

WO2010/134350 publication WO2011/070963 publication WO2016/158191 publication WO2022/045272 publication WO2021/200252 publication WO2020/218188 publication WO2021/065492 publication WO2012/077520 publication

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

In order to use 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 while simultaneously ensuring sufficient stability during operation, but these cannot be achieved with materials consisting of combinations of previously known compounds.

The present invention was made in consideration of the current situation, and aims to provide a material for organic electroluminescence devices that can produce practically useful organic EL elements 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 element using such a material.

　ここで、a及びbは置換数を表し、aは１～５、ｂは１～４を表す。ｍは繰り返し数で１又は２を表す。Ａｒ^０及びＡｒ^１はそれぞれ独立に、水素、炭素数１～１０の脂肪族炭化水素基、置換若しくは未置換の炭素数１８～３６のトリアリールシリル基、置換若しくは未置換のフェニル基、又はフェニル基が２～３個連結して構成される置換若しくは未置換の連結芳香族基を表す。Ｒ^２～Ｒ^７はそれぞれ独立に、水素、炭素数１～１０の脂肪族炭化水素基、置換若しくは未置換の炭素数１８～３６のトリアリールシリル基、置換若しくは未置換の炭素数６～２０の芳香族炭化水素基、置換若しくは未置換の炭素数２～２０の芳香族複素環基、又は該芳香族炭化水素基及び該芳香族複素環基から選ばれる芳香族基が２～３個連結して構成される置換若しくは未置換の連結芳香族基を表す。ただし、Ｒ^２～Ｒ^７はカルバゾールを含むことはない。また、一般式（１）で表される化合物中の水素の一部又は全部は重水素で置換されてもよい。 That is, the present invention relates to a material for an organic electroluminescent device represented by the following general formula (1).

Here, a and b represent the number of substitutions, a represents 1 to 5, and b represents 1 to 4. m represents the number of repetitions and represents 1 or 2. ^{Ar 0} and Ar ¹ each independently represent 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 phenyl group, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 phenyl groups. R ² to R ⁷ each independently represent 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. However, R ² to R ⁷ do not include carbazole. In addition, some or all of the hydrogen atoms in the compound represented by the general formula (1) may be replaced with deuterium atoms.

The compound represented by the general formula (1) preferably contains at least one deuterated carbazolyl group represented by any one of the following formulae (1a) to (1e), in which D represents deuterium and "*" represents the bonding position to the adjacent group.

The material for organic electroluminescent devices represented by the general formula (1) preferably has an average deuteration rate of 20% or more for all hydrogen contained in the general formula (1).

ここで、式（２）～（７）の中のＲ^２～Ｒ^７は式（１）と同義である。式（２）～（７）で表される結合構造中の一部又は全ての水素は重水素で置換されてもよい。＊は隣接する基との結合位置を示す。 The compound represented by the general formula (1) preferably contains at least one bond structure represented by any of the following formulae (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 formulae (2) to (7) may be replaced with deuterium atoms. In addition, "*" in the formulae indicates the bonding position with the adjacent group.

Here, R ² to R ⁷ in formulas (2) to (7) have the same meaning as in formula (1). Some or all of the hydrogen atoms in the bond structures represented by formulas (2) to (7) may be replaced with deuterium atoms. * indicates the bond position to the adjacent group.

　ここで、Ａｒ^２及びＡｒ^３はそれぞれ独立に、水素、炭素数１～１０の脂肪族炭化水素基、置換若しくは未置換の炭素数１８～３６のトリアリールシリル基、置換若しくは未置換の炭素数６～２０の芳香族炭化水素基、置換若しくは未置換の炭素数２～１７の芳香族複素環基、又は該芳香族炭化水素基及び該芳香族複素環基から選ばれる芳香族基が２～３個連結して構成される置換若しくは未置換の連結芳香族基を表す。Ｌ^１は単結合若しくは置換若しくは未置換のフェニル基を表す。前記一般式（１０）で表される化合物中の水素の一部又は全部は重水素で置換されてもよい。前記一般式（１０）中のＬ^１は単結合であることが好ましい。 In addition, the material for organic electroluminescent elements of the present invention is preferably a mixed material for organic electroluminescent elements, characterized in that it contains a compound represented by the general formula (1) and a cyclic azine compound represented by the following general formula (10):

Here, Ar ² and Ar ³ each independently represent hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. L ¹ represents a single bond or a substituted or unsubstituted phenyl group. A part or all of the hydrogen in the compound represented by the general formula (10) may be substituted with deuterium. It is preferable that L ¹ in the general formula (10) is a single bond.

The present invention also relates to an organic electroluminescence device comprising one or more organic layers between opposing anodes and cathodes, characterized in that at least one of the organic layers contains a mixed material for organic electroluminescence devices represented by the general formula (1), and it is preferable that the organic layer contains a compound represented by the general formula (1) and a compound represented by the general formula (10). The compound represented by the general formula (1) and the compound represented by the general formula (10) may be supplied separately to the organic layer, or may be supplied as a premixed material for organic electroluminescence devices.

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

In addition, in the organic electroluminescent device of the present invention, the organic layer containing the mixed material for the organic electroluminescent device is the light-emitting layer, and it is preferable that the light-emitting layer contains a phosphorescent material, and it is more preferable that the phosphorescent material contains platinum atoms.

In the organic electroluminescent device of the present invention, the organic layer containing the mixed material for organic electroluminescent devices is the light-emitting layer, and it is preferable that the material for organic electroluminescent devices is contained as a host material, and it is more preferable that the light-emitting layer contains a thermally activated delayed fluorescent material containing boron atoms and a phosphorescent material containing platinum atoms.

Furthermore, the present invention relates to 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 to use an emitting layer formed by evaporating a premixed material for an organic electroluminescent device in which a compound represented by the general formula (1) of the present invention and a compound represented by the general formula (10) of the present invention are mixed in advance, from a single evaporation source.

According to the present invention, it is possible to obtain an organic EL element that is practically useful because it emits light with high efficiency while being driven at a low voltage and has long life characteristics. In particular, the compound represented by the general formula (1) has a structure in which a carbazole polymer and an aromatic hydrocarbon group are linked at the ortho position of the benzene, which suppresses some intramolecular rotation and makes the molecular structure less susceptible to changes in response to stimuli such as heat and current when the element is operated. This results in long life characteristics.

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

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

First, general formula (1) is as described above, and a and b represent the number of substitutions, a being 1 to 5 and b being 1 to 4. Preferably, a is 1 or 2 and b is 1 or 2. m is the number of repetitions and represents 1 or 2. Preferably, it is 1.

Ar ⁰ and Ar ¹ each independently represent 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 phenyl group, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 phenyl groups, preferably hydrogen, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 phenyl groups, and more preferably hydrogen, or a substituted or unsubstituted phenyl group.

R ² to R ⁷ each independently represent 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 group and the aromatic heterocyclic group. Preferably, they represent hydrogen, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. More preferably, they represent hydrogen, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group. However, R ² to R ⁷ do not contain carbazole.
In addition, a part or all of hydrogen in the compound represented by the general formula (1) may be replaced with deuterium. Preferably, the average deuteration rate of all hydrogen in the compound represented by the general formula (1) is 20% or more, more preferably 50% or more, and even more preferably 80% or more. In addition, it is preferable that the compound represented by the general formula (1) contains at least one deuterated carbazolyl group represented by any one of the formulas (1a) to (1e). In addition, in the case of the compound represented by the general formula (1), for example, the average deuteration rate in the present invention includes both a case where the compound is composed of a single compound and a case where the compound is composed of a mixture of two or more compounds represented by the general formula (1). That is, in a specific example of the average deuteration rate, when the average deuteration rate is 50%, it means that half of the total hydrogen is replaced with deuterium on average, and the compound may be composed of a single compound or a mixture of compounds with different deuteration rates.

The compound represented by the general formula (1) preferably contains at least one bond structure represented by any one of the formulas (2) to (7), more preferably at least two. Among these, the compound represented by the general formula (1) preferably contains at least one bond structure represented by the formula (2) or (3), at least one bond structure represented by the formula (4) or (5), or at least one bond structure represented by the formula (6) or (7).
The bond structure means that the bonding positions of adjacent carbazoles are specific.
In addition, a part or all of the hydrogen atoms in the bond structures represented by the formulas (2) to (7) may be replaced with deuterium atoms. Also, * in the formulas indicates the bond position with the adjacent carbazole.

Specific examples of Ar ⁰ and Ar ¹ that are unsubstituted aliphatic hydrocarbon groups having 1 to 10 carbon atoms include methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, and decyl. Preferred are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl.

Specific examples of the unsubstituted triarylsilyl group having 18 to 36 carbon atoms in Ar ⁰ and Ar ¹ include triphenylsilyl, biphenyldiphenylsilyl, bisbiphenylphenylsilyl, and trisbiphenylsilyl. Preferred are triphenylsilyl, biphenyldiphenylsilyl, and bisbiphenylphenylsilyl.

Specific examples when R ² to R ⁷ are unsubstituted aliphatic hydrocarbon groups having 1 to 10 carbon atoms are the same as the specific examples when Ar ⁰ and Ar ¹ are unsubstituted aliphatic hydrocarbon groups having 1 to 10 carbon atoms.

Specific examples when R ² to R ⁷ are unsubstituted triarylsilyl groups having 18 to 36 carbon atoms are the same as the specific examples when Ar ⁰ and Ar ¹ are unsubstituted triarylsilyl groups.

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

As described above, in the cyclic azine compound represented by the general formula (10), Ar ² and Ar ³ each independently represent hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. Preferably, 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, L1 represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linking aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups. Furthermore, ^L1 represents a single bond or a substituted or unsubstituted phenyl group, and is preferably a single bond.
In addition, a part or all of the hydrogen atoms in the compound represented by the general formula (10) may be replaced with deuterium atoms.

Specific examples of when Ar ² and Ar ³ are unsubstituted aliphatic hydrocarbon groups having 1 to 10 carbon atoms are the same as the specific examples of when Ar ⁰ and Ar ¹ are unsubstituted aliphatic hydrocarbon groups having 1 to 10 carbon atoms.

Specific examples when Ar ² and Ar ³ are unsubstituted triarylsilyl groups having 18 to 36 carbon atoms are the same as the specific examples when Ar ⁰ and Ar ¹ are unsubstituted triarylsilyl groups having 18 to 36 carbon atoms.

Further, specific examples of the case where Ar ² and Ar ³ are unsubstituted aromatic hydrocarbon groups having 6 to 20 carbon atoms, unsubstituted aromatic heterocyclic groups having 2 to 17 carbon atoms, or linked aromatic groups 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, imidazoline, and the like. Examples of groups derived from aryl, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. Preferred are groups derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole.

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

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

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

The mixed material for organic electroluminescent elements in the present invention may be in the form of a powder, solid, or thin film, so long as it contains the compound represented by the general formula (1) and the cyclic azine compound represented by the 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 the general formula (1) and the compound represented by the general formula (10) may be supplied separately to the light-emitting layer, or the compound represented by the general formula (1) and the compound represented by the general formula (10) may be supplied as a premixed material for organic electroluminescent elements in which they are mixed in advance. Among these, it is preferable to supply the compound represented by the general formula (1) and the compound represented by the general formula (10) as a premixed material for organic electroluminescent elements in which they are mixed in advance.

The mixed material for organic electroluminescence elements may be prepared by mixing the compound represented by the general formula (1) and the compound represented by the general formula (10) in a powder state, 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. It may also be prepared as a thin film by deposition or the like. On the other hand, if the compound represented by the general formula (1) and the compound represented by the general formula (10) constituting the mixed material are not premixed in advance, they may be contained in different organic layers of the element. For example, the compound represented by the general formula (1) may be contained in the electron blocking layer, and the compound represented by the general formula (10) may be contained in the light-emitting layer. The premixed material for organic electroluminescence elements refers to a mixture of the compound represented by the general formula (1) and the compound represented by the general formula (10) in a powder state, or a mixture of these powders premixed by heating and melting.

In the present invention, the mixed material for an organic electroluminescent device of the compound represented by the general formula (1) and the compound represented by the general formula (10) is preferably such that the mixing ratio (mass ratio) in the mixed material is 40 to 90 mass %, preferably 50 to 90 mass %, and 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).

Specific examples of compounds represented by general formula (1) are shown below, but the present invention is not limited to these exemplary compounds. Note that n in Dn described in 1-119 to 1-123 represents the average number of substitutions of deuterium (D) contained in the molecule, and changes depending on the average deuteration rate.

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

The present invention also relates to an organic electroluminescent device comprising one or more organic layers between opposing anodes and cathodes, characterized in that at least one of the organic layers contains a compound represented by the general formula (1) or a mixed material for organic electroluminescent devices comprising a compound represented by the general formula (1) and a compound represented by the general formula (10), and preferably the organic layer is an organic electroluminescent device comprising the mixed material for organic electroluminescent devices.

The organic electroluminescent 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. More preferably, the emitting layer further contains a thermally activated delayed fluorescent material or a phosphorescent material, and even more preferably, the emitting layer contains a thermally activated delayed fluorescent material. In addition, the thermally activated delayed fluorescent material preferably contains boron atoms, and the phosphorescent material preferably contains platinum atoms.

In other words, if necessary, the light-emitting layer can contain at least one host material together with the thermally activated delayed fluorescent material or phosphorescent material to produce an excellent organic EL device, and it is preferable that at least one host material is a material for organic electroluminescent devices that is a compound represented by the general formula (1). In addition, when the light-emitting layer contains at least two host materials, it is preferable to use a compound represented by the general formula (1) as the first host and a compound represented by the general formula (10) as the second host.

Furthermore, the present invention relates to an organic electroluminescence device having one or more organic layers between opposing anodes and cathodes, and a method for producing the same, in which a light-emitting layer is formed by vapor deposition from a single vapor deposition source using a premixed material for organic electroluminescence devices in which a compound represented by the general formula (1) and a cyclic azine compound represented by the general formula (10) are mixed in advance. In producing the organic layer of the organic electroluminescence device, the premixed material for organic electroluminescence devices is a premix of the compound represented by the general formula (1) and the compound represented by the general formula (10) in powder form, or a premix of these powders by heating and melting them, and the premix is used to produce the light-emitting layer of the organic EL device by vapor deposition from a single vapor deposition source.

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.

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

It is also possible to have the reverse structure to that shown in Figure 1, that is, to stack the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, hole injection layer 3, and anode 2 on the substrate 1 in that order, and in this case too, layers can be added or omitted as necessary. In the organic EL element described above, the layers that make up the stacked structure on the substrate other than the electrodes such as the anode and cathode are sometimes collectively referred to as organic layers.

-substrate-
The organic EL element of the present invention is preferably supported by a substrate. There are no particular limitations on the substrate, and any substrate that has been conventionally used in organic EL elements, such as glass, transparent plastic, quartz, etc., can be used.

-anode-
As the material of the anode in the organic EL element, a material consisting of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, CuI, indium tin oxide (ITO), SnO ₂ , ZnO, and other conductive transparent materials. In addition, amorphous materials such as IDIXO (In ₂ O ₃ -ZnO) that can be used to prepare a transparent conductive film may be used. The anode may be formed by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering, and forming a pattern of a desired shape by a photolithography method, or when pattern accuracy is not required very much (about 100 μm or more), a pattern may be formed through a mask of a desired shape during vapor deposition or sputtering of the electrode material. Alternatively, when a coatable material such as an organic conductive compound is used, a wet film formation method such as a printing method or a coating method may be used. When light is to be emitted from this anode, it is desirable to make the 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 from the range of 10 to 1000 nm, preferably 10 to 200 nm.

-cathode-
On the other hand, as the material of the cathode, a material consisting of a metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, or a mixture thereof having a small work function (4 eV or less) is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, a magnesium/copper mixture, a magnesium/silver mixture, a magnesium/aluminum mixture, a magnesium/indium mixture, an aluminum/aluminum oxide (Al ₂ O ₃ ) mixture, indium, a lithium/aluminum mixture, and a rare earth metal. Among these, from the viewpoint of electron injectability and durability against oxidation, etc., a mixture of an electron injecting metal and a second metal which is a metal having a larger and more stable work function than the electron injecting metal, such as a magnesium/silver mixture, a magnesium/aluminum mixture, a magnesium/indium mixture, an aluminum/aluminum oxide (Al ₂ O ₃ ) mixture, a lithium/aluminum mixture, and aluminum, is preferable. The cathode can be produced by forming a thin film of these cathode materials by a method such as vapor deposition or sputtering. The sheet resistance of the cathode is preferably several hundred Ω/□ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, it is advantageous for either the anode or the cathode of the organic EL element to be transparent or semi-transparent, as this improves the luminance of the emitted light.

In addition, after forming the above metals in a thickness of 1 to 20 nm on the cathode, a transparent or translucent cathode can be made by forming the conductive transparent material mentioned in the explanation of the anode on top of it. This can be used to create an element in which both the anode and cathode are transparent.

-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 either a single layer or multiple layers, and each layer contains an organic light-emitting dopant material and a host material.

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

When a phosphorescent dopant is used as the organic light-emitting dopant material, the phosphorescent dopant is preferably one that contains an organometallic complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. More preferably, it is an organometallic complex containing platinum, and specifically, the iridium complexes described in J.Am.Chem.Soc.2001,123,4304 and JP2013-530515A and the platinum complexes described in Adv.Mater.2014,26,7116 and JP2018-2722A are preferably used, but are not limited to these.

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

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

The fluorescent dopant material is not particularly limited, but specific examples include the following:

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

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 it is not a compound represented by the general formula (10).

As the host material in the light-emitting layer, it is preferable to use 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 be used in combination with a known host material used in phosphorescent or fluorescent light-emitting devices. Note that a combination of multiple known host materials may be used, or each may be used alone. The known host material that can be used is preferably a compound that has hole transporting ability and electron transporting ability and has a high glass transition temperature, and has a triplet excitation energy (T1) greater than the triplet excitation energy (T1) of the light-emitting dopant material. In addition, a TADF-active compound may be used as the host material, and in this case, a compound in which the difference between the singlet excitation energy (S1) and the triplet excitation energy (T1) (ΔEST = S1 - T1) is 0.20 eV or less is preferable. The compound represented by the general formula (1) may be used alone as a host material in the light-emitting layer, and other known host materials may be used in combination. However, in order to improve the characteristics of the organic EL device, it is preferable to use the compound represented by the general formula (10) in combination as a host material. Note that a plurality of types of the other known host materials may be used in combination.

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

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

The other known host materials can be selected from those known in numerous patent documents, etc. Specific examples of host materials 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 represented by metal complexes of benzoxazole and benzothiazole compounds, poly(N-vinylcarbazole) compounds, aniline copolymer compounds, thiophene oligomers, polythiophene compounds, polyphenylene compounds, polyphenylenevinylene compounds, polyfluorene compounds, and other polymeric compounds. Preferred examples include carbazole compounds, indolocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, anthracene compounds, triphenylene compounds, carborane compounds, and porphyrin compounds.

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

When using multiple types of hosts, each host can be evaporated from a different evaporation source, or they can be premixed before evaporation to form a premixed material, allowing multiple hosts to be evaporated simultaneously from a single evaporation source.

When multiple types of hosts are used, the host is preferably a mixed material for organic electroluminescent devices obtained by mixing a compound represented by the general formula (1) and a compound represented by the general formula (10).

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

The difference in 50% weight loss temperature between the two types of hosts in the premixed material is preferably within 20°C. By vaporizing and depositing this premix from a single evaporation source, it is possible to obtain a uniform deposited film. In this case, the premix may be mixed with a luminescent dopant material required to form a light-emitting layer or other hosts to be used as necessary, but if there is a large difference in the temperature at which the desired vapor pressure is achieved, it is better to deposit from separate evaporation sources.

In addition, 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 first host relative to the total of the first host and the second host. When the compound represented by the general formula (1) and the compound represented by the general formula (10) are used as hosts, the first host is the compound represented by the general formula (1), and the compound represented by the general formula (10) is the second host.

As mentioned above, the method for premixing the host is preferably one that allows for as uniform mixing as possible, and examples of such methods 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.

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

-Injection layer-
The injection layer is a layer provided between an electrode and an organic layer to reduce the driving voltage and improve the luminance of light emitted, and includes a hole injection layer and an electron injection layer, and 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. The injection layer can be provided as necessary.

-Hole blocking layer-
In a broad sense, the hole blocking layer has the function of an electron transport layer, and is made of a hole blocking material that has the function of transporting electrons but has a significantly small ability to transport holes, and can improve the probability of recombination of electrons and holes in the light emitting layer by blocking holes while transporting electrons. The hole blocking layer can be made of a known hole blocking material. A plurality of hole blocking materials may also be used in combination.

-Electron blocking layer-
In a broad sense, the electron blocking layer has the function of a hole transport layer, and by blocking electrons while transporting holes, the probability of electrons and holes recombining in the light emitting layer can be improved. As the material of the electron blocking layer, it is preferable to use the compound represented by the general formula (1) or the mixed material, but a known electron blocking layer material 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 compound represented by the general formula (1), the known host material described above, and a host material obtained by combining a plurality of these may be used as the host material.

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

-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 multiple layers.

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 may be selected from conventionally known compounds. Examples of such hole transport materials include porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

-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 provided as a single layer or as a multi-layer.

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

When producing the organic EL element of the present invention, there are no particular limitations on the method for forming each layer, and they may be produced by either a dry process or a wet process.

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

As a representative example, the synthesis of compound 1-119 is shown below. Other compounds were synthesized in a similar manner. Note that Dn in the formula indicates that some or all of the hydrogen atoms in the compound are deuterated, independently for each compound.

化合物（a）１５.３gに、化合物（b）を１８．９ g、炭酸カリウムを ２０．３ g、ヨウ化銅を４．５ g、 １８－ｃｒｏｗｎ－６を１．３ｇ、１，３－ジメチル－２－イミダゾリジノン２００mLを加え、窒素雰囲気下で１８０℃にて２４時間撹拌した。室温まで冷却後、水を５００ ml加え固体析出させたのち、固体を濾別した。シリカゲルカラムクロマトグラフィーで精製を行い、白色固体として化合物（ｃ）を１２．４ gを得た。
Synthesis Example 1

To 15.3 g of compound (a), 18.9 g of compound (b), 20.3 g of potassium carbonate, 4.5 g of copper iodide, 1.3 g of 18-crown-6, and 200 mL of 1,3-dimethyl-2-imidazolidinone were added, and the mixture was stirred at 180°C for 24 hours under a nitrogen atmosphere. After cooling to room temperature, 500 mL of water was added to precipitate a solid, which was then filtered off. The mixture was purified by silica gel column chromatography to obtain 12.4 g of compound (c) as a white solid.

化合物　（c）　１０．０ｇに、重ベンゼン（Ｃ６Ｄ６）を１２０ｍｌ、重トリフルオロメタンスルホン酸（ＴｆＯＤ）を５．２ｇ加え、窒素雰囲気下、５０℃で３時間加熱撹拌した。反応液を炭酸カリウム（５．３ｇ）の重水溶液（２４ｍｌ）に加えて急冷し、分離、精製して重水素化物である化合物（１－１１９）を６．２ｇ得た。 Synthesis Example 2

To 10.0 g of compound (c), 120 ml of deuterated benzene (C6D6) and 5.2 g of deuterated trifluoromethanesulfonic acid (TfOD) were added, and the mixture was heated and stirred at 50° C. for 3 hours under a nitrogen atmosphere. The reaction liquid was added to a deuterium oxide solution (24 ml) of potassium carbonate (5.3 g) and quenched, and then separated and purified to obtain 6.2 g of the deuterated compound (1-119).

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

Example 1
On a glass substrate on which an anode made of ITO having a film thickness of 70 nm was formed, each of the thin films shown below was laminated at a vacuum degree of 4.0×10 ⁻⁵ Pa by vacuum deposition. First, HAT-CN shown above was formed on ITO as a hole injection layer to a thickness of 10 nm, and then HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1-12) 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 emission layer having a thickness of 40 nm. At this time, the co-deposition was performed under deposition conditions in which the concentration of BD-2 was 13% by mass, the concentration of BD-1 was 0.4% by mass, and 1-12 was 86.6% by mass. Next, ET-2 was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer to a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer to a thickness of 1 nm on the electron transport layer. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby producing the organic EL element according to Example 1.

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

Examples 2 to 9
Organic EL devices were prepared in the same manner as in Example 1, except that the electron blocking layer material and the first host were the compounds shown in Table 1.

Example 10
On a glass substrate on which an anode made of ITO having a thickness of 70 nm was formed, each of the thin films shown below was laminated by vacuum deposition at a vacuum degree of 4.0×10 ⁻⁵ Pa. First, HAT-CN shown above was formed on ITO as a hole injection layer to a thickness of 10 nm, and then HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1-6) was co-deposited as a first host, compound (2-49) was co-deposited as a second host, BD-2 was co-deposited as a phosphorescent dopant, and BD-1 was co-deposited as a thermally activated delayed fluorescent dopant from different deposition sources to form an emitting layer having a thickness of 40 nm. At this time, the co-deposition was performed under deposition conditions where the concentration of BD-2 was 13% by mass, the concentration of BD-1 was 0.4% by mass, and the mass ratio of the first host to the second host was 50:50. Next, ET-2 was formed to a thickness of 5 nm as a hole blocking layer. Next, ET-2 was formed to a thickness of 31 nm as an electron transport layer. Furthermore, lithium fluoride (LiF) was formed 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 an organic EL device according to Example 2.

Examples 11 to 32, Examples A-1 to A-6, Comparative Examples 2 to 10, Comparative Examples A-1 to A-4
Organic EL devices were prepared in the same manner as in Example 10, except that the electron blocking layer material, the first host, and the second host were the compounds shown in Table 1 or Table 2. The compounds (1-118), (1-119), (1-120), (1-121), (1-122), (1-123), (1-124), (1-125), (1-126), (1-127), (1-128), and (1-129) had average deuteration ratios of 26%, 85%, 88%, 90%, 83%, 89%, 86%, 90%, 87%, 83%, 82%, and 84%, respectively. The compounds HT-8, HT-9, HT-10, and HT-11 had average deuteration ratios of 86%, 86%, 88%, and 87%, respectively. The average deuteration ratio indicates the ratio of hydrogen contained in the compound that is deuterium-substituted, and was determined by mass spectrometry or proton nuclear magnetic resonance spectroscopy.

For example, when determining the average deuteration ratio by proton nuclear magnetic resonance spectroscopy, a measurement sample is prepared by adding and dissolving the compound and an internal standard in a deuterated solvent, and the proton concentration [mol/g] of the compound contained in the measurement sample is calculated from the integrated intensity ratio of the internal standard and the compound. Next, the ratio of the proton concentration of the deuterated compound to the proton concentration of the corresponding non-deuterated compound is calculated, and the average deuteration ratio of the deuterated compound can be calculated by subtracting it from 1. The average deuteration ratio of a partial structure can be calculated from the integrated intensity of the chemical shift derived from the target partial structure in the same manner as above. The method for determining the average deuteration ratio of compound 1-118 by proton nuclear magnetic resonance spectroscopy is shown below. First, a measurement sample was prepared by dissolving compound 1-118 (5.0 mg) and dimethyl sulfone (2.0 mg) as an internal standard in deuterated tetrahydrofuran (1.0 ml). The average proton concentration [mol/g] of compound 1-118 contained in the measurement sample was calculated from the integrated intensity ratio of the internal standard and compound 1-118. The average proton concentration [mol/g] was also calculated in the same manner for the non-deuterated form of compound 1-118 (corresponding to example compound 1-15). Next, the ratio of the proton concentration of compound 1-118 to the proton concentration of the non-deuterated form of compound 1-118 was calculated, and this was subtracted from 1 to calculate the average deuteration rate of compound 1-118.

The evaluation results of the produced organic EL elements are shown in Tables 3 and 4. 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 the organic EL elements, indicating that light emission was obtained from BD-1.
The voltage and power efficiency in the table are values at a driving current of 2.5 mA/cm2, which are initial characteristics. The lifetime is the time it takes for the brightness to decay to 97% when the initial brightness at a driving current of 4.0 mA/cm2 is taken as 100%, and represents the lifetime characteristics. The emission color was confirmed by the emission spectrum of the organic EL element. From the results of the examples and comparative examples shown in Tables 3 and 4, it can be seen that the organic EL element using the mixed material for organic electroluminescent element of the present invention as a host in the emission layer emits blue light and has low voltage, high efficiency, and long lifetime characteristics.

Example 33
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 laminated by vacuum deposition at a vacuum degree of 4.0×10 ⁻⁵ Pa. First, HAT-CN shown above was formed on ITO as a hole injection layer with a thickness of 10 nm, and then HT-1 was formed as a hole transport layer with a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer with a thickness of 5 nm. Next, compound (1-12) was co-deposited as a first host and BD-2 was co-deposited as a phosphorescent dopant from different deposition sources to form a light-emitting layer having a thickness of 40 nm. At this time, the co-deposition was performed under deposition conditions in which the concentration of BD-2 was 13% by mass. Next, ET-2 was formed as a hole blocking layer with a thickness of 5 nm. Next, ET-2 was formed as an electron transport layer with a thickness of 31 nm. Furthermore, lithium fluoride (LiF) was formed as an electron injection layer on the electron transport layer with a thickness of 1 nm. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer, thereby completing the organic EL element according to Comparative Example 9.

Examples 34 to 41, Comparative Example 11
As shown in Table 5, an organic EL device was prepared in the same manner as in Example 33, except that the first host was a compound shown in Table 5.

Example 42
On a glass substrate on which an anode made of ITO having a thickness of 70 nm was formed, each of the thin films shown below was laminated by vacuum deposition at a vacuum degree of 4.0×10 ⁻⁵ Pa. First, HAT-CN shown above was formed on ITO as a hole injection layer to a thickness of 10 nm, and then HT-1 was formed as a hole transport layer to a thickness of 60 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1-12) was co-deposited as a first host, compound (2-49) was co-deposited as a second host, and BD-2 was co-deposited as a phosphorescent dopant from different deposition sources to form a light-emitting layer having a thickness of 40 nm. At this time, the co-deposition was performed under deposition conditions in which 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, and finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer to prepare an organic EL device according to Example 42.

Examples 43 to 64, Comparative Examples 12 to 18
An organic EL device was prepared in the same manner as in Example 42, except that the electron blocking layer material, the first host, and the second host were each formed as the compounds shown in Table 5.

The evaluation results of the organic EL elements produced are shown in Table 6. The voltage and power efficiency in the table are values at a drive current of 2.5 mA/cm2, which are initial characteristics. The lifetime is the time it takes for the brightness to decay to 97% when the initial brightness at a drive current of 4.0 mA/cm2 is taken as 100%, and represents the lifetime characteristics. The emitted color was confirmed by the emission spectrum of the organic EL element.

1  Substrate, 2  Anode, 3  Hole injection layer, 4  Hole transport layer, 5  Emitting layer, 6  Electron transport layer, 7  Cathode

According to the present invention, it is possible to obtain a practically useful organic EL element which is driven at a low voltage, emits light with high efficiency, and has a long life characteristic.

Claims (20)

A material for an organic electroluminescent device represented by the following general formula (1):

(Here, a and b represent the number of substitutions, a represents 1 to 5 and b represents 1 to 4. m is the number of repetitions and represents 1 or 2. Ar ⁰ and Ar ¹ each independently represent 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 phenyl group, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 phenyl groups. R ² to R ⁷ each independently represent 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. However, R ² to 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 replaced with deuterium atoms. The material for organic electroluminescent devices according to claim 1, characterized in that the compound represented by the general formula (1) contains at least one deuterated carbazolyl group represented by any one of the following formulas (1a) to (1e):

(D represents deuterium, and * indicates the bonding position with the adjacent group.) The material for organic electroluminescence devices according to claim 1, characterized in that the average deuteration rate of all hydrogen atoms contained in the general formula (1) is 20% or more. 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):

(Here, R ² to R ⁷ in formulas (2) to (7) have the same meaning as in formula (1). A part or all of the hydrogen atoms in the bond structures represented by formulas (2) to (7) may be replaced with deuterium atoms. * indicates the bond position to the adjacent group.) The material for organic electroluminescent devices according to claim 4, characterized in that the compound represented by the general formula (1) contains at least one bond structure represented by the formula (2) or (3). The material for organic electroluminescent devices according to claim 4, characterized in that the compound represented by the general formula (1) contains at least one bond structure represented by the formula (4) or (5). The material for organic electroluminescent devices according to claim 4, characterized in that the compound represented by the general formula (1) contains at least one bond structure represented by the formula (6) or (7). The material for organic electroluminescent devices according to claim 4, characterized in that the compound represented by the general formula (1) contains at least two bond structures represented by the formulas (2) to (7). A mixed material for an organic electroluminescent device, comprising the compound represented by the general formula (1) according to claim 1 and a cyclic azine compound represented by the following general formula (10):

(Here, Ar ² and Ar ³ each independently represent hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. L ¹ represents a single bond or a substituted or unsubstituted phenyl group. A part or all of the hydrogen in the compound represented by the general formula (10) may be substituted with deuterium.) An organic electroluminescent device comprising one or more organic layers between opposing anode and cathode, wherein at least one of the organic layers contains the material for organic electroluminescent devices described in claim 1. An organic electroluminescent device comprising one or more organic layers between opposing anodes and cathodes, wherein at least one of the organic layers contains the mixed material for organic electroluminescent devices described in claim 9. The organic electroluminescent device according to claim 11, characterized in that the organic layer containing the mixed material for the organic electroluminescent device is an emitting layer, and the emitting layer contains a thermally activated delayed fluorescent material. The organic electroluminescent device according to claim 12, characterized in that the organic layer containing the mixed material for the organic electroluminescent device is an emitting layer, and the emitting layer contains a thermally activated delayed fluorescent material containing boron atoms. The organic electroluminescent device according to claim 11, characterized in that the organic layer containing the mixed material for the organic electroluminescent device is an emitting layer, and the emitting layer contains a phosphorescent material. The organic electroluminescent device according to claim 14, characterized in that the organic layer containing the mixed material for the organic electroluminescent device is an emitting layer, and the emitting layer contains a phosphorescent material containing platinum atoms. The organic electroluminescent device according to claim 11, characterized in that the organic layer containing the mixed material for the organic electroluminescent device 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. The organic electroluminescent device according to claim 11, characterized in that the light-emitting layer contains the mixed material for organic electroluminescent devices according to claim 9 as a mixed host material. A premixed material for an organic electroluminescent device, comprising the compound represented by the general formula (1) according to claim 1 and a cyclic azine compound represented by the following general formula (10):

(Here, Ar ² and Ar ³ each independently represent hydrogen, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted triarylsilyl group having 18 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups. L ¹ represents a single bond or a substituted or unsubstituted phenyl group. A part or all of the hydrogen in the compound represented by the general formula (10) may be substituted with deuterium.) An organic electroluminescent device comprising one or more organic layers between opposing anodes and cathodes, wherein at least one of the organic layers contains the premixed material described in claim 18. 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, the method comprising the steps of: forming the light-emitting layer by depositing the premixed material according to claim 18 from a single deposition source.

Images