Organic electroluminescent device

Abstract

To provide a blue light-emitting organic EL device having high emission efficiency and a long lifetime.SOLUTION: The organic EL device comprises one or more light emitting layers between an anode and a cathode opposite to each other. At least one of the light emitting layers contains a first host, a second host, and a light emitting dopant. The first host is a carbazole compound or a bicarbazole compound. The second host is an indolocarbazole compound. The light emitting dopant is a polycyclic aromatic compound represented by general formula (4) or a polycyclic aromatic compound having this structure as a partial structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an organic electroluminescent device (referred to as an organic EL device).

[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. Due to the statistical laws of electron spin, singlet and triplet excitons are generated in a ratio of 1:3. It is said that the internal quantum efficiency of fluorescent organic EL elements, which 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, which use emission from triplet excitons, can be increased to 100% if intersystem crossing from singlet excitons is efficiently achieved. However, extending the life of blue phosphorescent organic EL elements remains a technical challenge.

[0003] Recently, highly efficient organic EL devices utilizing delayed fluorescence have been developed. For example, Patent Document 1 discloses an organic EL device utilizing the TTF (Triplet-Triplet Fusion) mechanism, 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 devices, further improvements in efficiency are required.

[0004] Patent Document 2 discloses an organic EL device that utilizes the TADF (Thermally Activated Delayed Fluorescence) 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%. However, as with phosphorescent devices, further improvements in lifetime characteristics are required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2010 / 134350 publication [Patent Document 2] WO2011 / 070963 publication [Patent Document 3] WO2017 / 138526 publication [Patent Document 4] WO2018 / 198844 publication [Patent Document 5] WO2020 / 040298 publication

[0006] Patent Document 3 discloses an organic EL device that uses a TADF material, such as the polycyclic aromatic compound shown below, as a light-emitting dopant, but does not disclose practical life characteristics. [ka]

[0007] Patent Document 4 discloses a phosphorescent organic EL device in which an indolocarbazole compound and a carbazole compound, such as the compound shown below, are mixed in an emitting layer, but does not disclose an organic EL device having an emitting layer in which a polycyclic aromatic compound represented by general formula (4) is mixed and which exhibits practical life characteristics. [ka]

[0008] Patent Document 5 discloses an organic EL device in which a mixture of a boron-based compound (a5), a TADF compound (a6), and a carbazole compound (a7) is used in the light-emitting layer, but does not disclose an organic EL device that exhibits practical life characteristics and in which a mixture of a first host represented by general formula (1) or general formula (2) and a second host represented by general formula (3) is used in the light-emitting layer. [ka] Summary of the Invention

[0009] In order to apply organic EL elements to display elements such as flat panel displays and light sources, it is necessary to improve the luminous efficiency of the elements while ensuring sufficient stability during operation. An object of the present invention is to provide a practically useful organic EL element that is highly efficient and has a long lifespan.

[0010] The present invention provides an organic electroluminescent device comprising one or more emitting layers between an anode and a cathode facing each other, wherein at least one emitting layer comprises a host and a luminescent dopant, the host comprises a first host represented by general formula (1) or general formula (2) and a second host represented by general formula (3), and the luminescent dopant comprises a polycyclic aromatic compound represented by general formula (4) or a polycyclic aromatic compound having a structure represented by general formula (4) as a partial structure.

[0011] [ka] where Y 1 is O, S, or N-Ar 1 Represents. Ar 1 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these aromatic rings. R 1 independently represent deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. a's each independently represent an integer of 0 to 4; b's each independently represent an integer of 0 to 3;

[0012] [ka] Here, c's are independently integers of 0 to 5, d's are independently integers of 0 to 2, and at least one d is greater than or equal to 1. e's are independently integers of 0 to 2. R 2 are independently a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, L 2 is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Ar 2 is hydrogen, a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 or 3 of these.

[0013] [ka] where Z 3 is an indolocarbazole ring-containing group represented by formula (3a), and * is L 3 is the bonding position with Ring A is a heterocycle represented by formula (3b) and is fused to the adjacent ring at any position. L 3 and L 31 are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Ar 3 and Ar 31 are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these. R 3 are independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. f represents an integer of 1 to 3; g represents an integer of 0 to 3; h independently represents an integer of 0 to 4; i represents an integer of 0 to 2; and j represents an integer of 0 to 3.

[0014] [ka] Here, ring C, ring D, and ring E are independently an aromatic hydrocarbon ring having 6 to 24 carbon atoms or an aromatic heterocyclic ring having 3 to 17 carbon atoms. Y 4 is B, P, P=O, P=S, AL, Ga, As, Si-R 4 , or Ge-R 41 and X 4 are independently O, N-Ar 4 , S, or Se; R 4 , and R 41 each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, Ar 4 are independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these, and N-Ar 4 may be bonded to any of ring C, ring D, or ring E to form a heterocycle containing N, R 42 each independently represent a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, an arylheteroarylamino group having 12 to 44 carbon atoms, a diheteroarylamino group having 12 to 44 carbon atoms, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms; Each v independently represents an integer of 0 to 4; x represents an integer of 0 to 3; C ring, D ring, E ring, R 4 , R 41 , R 42 , and Ar 4At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom.

[0015] Examples of polycyclic aromatic compounds having the structure represented by general formula (4) as a partial structure include polycyclic aromatic compounds represented by the following formula (5) and boron-containing polycyclic aromatic compounds represented by the following formula (6). [ka] Here, ring F, ring G, ring H, ring I, and ring J are each independently an aromatic hydrocarbon ring having 6 to 24 carbon atoms or an aromatic heterocyclic ring having 3 to 17 carbon atoms, and at least one hydrogen atom in ring F, ring G, ring H, ring I, and ring J may be substituted with halogen or deuterium. X 4 , Y 4 , R 42 , x, and v have the same meaning as in formula (4), w represents an integer of 0 to 4, y represents an integer of 0 to 3, and z represents an integer of 0 to 2.

[0016] [ka] where X 6 are independently N-Ar 6 , O, or S, but at least one X 6 is N-Ar 6 Represents Ar 6 independently represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these aromatic rings, 6 is X 6 may be bonded to the aromatic ring to form a heterocyclic ring containing N. R 6 independently represent a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. k independently represents an integer of 0 to 4; l independently represents an integer of 0 to 3; and m independently represents an integer of 0 to 2.

[0017] The first host is preferably a first host represented by general formula (1), and Y 1 N-Ar 1 A preferred example of general formula (1) is the following formula (7). [ka] where Ar 1 has the same meaning as general formula (1).

[0018] Another aspect of the present invention is the organic electroluminescent device, wherein the light-emitting layer contains a first host represented by general formula (2) and a second host represented by general formula (3).

[0019] A preferred example of the general formula (2) is the following formula (8). [ka] where n is an integer from 1 to 5, and p is an integer from 0 to 1. L 8 represents a group derived from benzene, dibenzofuran, or dibenzothiophene. R 81 represents hydrogen or a radical derived from benzene, dibenzofuran, or dibenzothiophene.

[0020] The light-emitting dopant preferably has a difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of 0.20 eV or less, more preferably 0.10 eV or less.

[0021] The light-emitting layer preferably contains 0.10 to 10 wt % of a light-emitting dopant and 99.9 to 90 wt % of a host, and the host preferably contains 10 to 90 wt % of the first host and 90 to 10 wt % of the second host.

[0022] The present invention also provides an organic EL element comprising one or more emitting layers between an anode and a cathode facing each other, wherein at least one of the emitting layers contains, as a emitting dopant, an organic emitting material having a difference (ΔEST) between its excited singlet energy (S1) and its excited triplet energy (T1) of 0.20 eV or less, and the above-mentioned first host and second host.

[0023] It is believed that the organic EL element of the present invention has a low driving voltage, high luminous efficiency, and long life because it contains a specific luminescent dopant and a plurality of specific host materials in the light-emitting layer. The reason why the organic EL device of the present invention has a low driving voltage is thought to be that the carbazole compound as the first host material has a property to easily inject holes, and the indolocarbazole compound as the second host material has a property to easily inject electrons, and therefore holes and electrons are presumed to be injected at a lower voltage, thereby generating excitons. Furthermore, the reason why the organic EL device of the present invention has high luminous efficiency is believed to be that the carbazole compound has the property of easily injecting holes, and the indolocarbazole compound has the property of easily injecting electrons, thereby making it possible to maintain a balance between holes and electrons in the luminescent layer. The reason why the organic EL element of the present invention has a long life is thought to be that when a voltage is applied to the organic EL element, holes are preferentially injected into the first host made of a carbazole compound and electrons are preferentially injected into the second host made of an indolocarbazole compound, thereby reducing the electrochemical load on the luminescent dopant. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an organic EL element. DETAILED DESCRIPTION OF THE INVENTION

[0025] The organic EL device of the present invention has one or more emitting layers between an anode and a cathode facing each other, and at least one emitting layer contains a first host, a second host, and a luminescent dopant. The first host is selected from compounds represented by general formula (1) or general formula (2), and the second host is selected from compounds represented by general formula (3). The light-emitting dopant is selected from polycyclic aromatic compounds represented by general formula (4) or polycyclic aromatic compounds having a structure represented by general formula (4) as a partial structure. A polycyclic aromatic compound having a structure represented by general formula (4) as a partial structure is also called a partial structure type polycyclic aromatic compound.

[0026] The compound represented by the above general formula (1) or (2) used as the first host in the present invention will be explained below.

[0027] In general formula (1), Y 1 is O, S, or N-Ar 1 Preferably, O or N-Ar 1 More preferably, N-Ar 1 Represents.

[0028] A preferred embodiment of general formula (1) is general formula (7). In general formula (1) and formula (7), common symbols have the same meaning.

[0029] Ar 1 independently represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 8 of these aromatic rings. A substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 4 of these aromatic rings, is preferred. A phenyl group, a biphenyl group, or a terphenyl group is more preferred.

[0030] Ar 1Specific examples of when is an unsubstituted aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, Examples of the group include groups formed by removing one hydrogen atom from azole, phthalazine, tetrazole, indole, pyridine, pyrimidine, triazine, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or a compound formed by linking 2 to 8 of these. Preferred examples include groups formed by removing one hydrogen atom from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, or a compound formed by linking 2 to 4 of these. More preferred examples include groups formed from benzene, biphenyl, or terphenyl.

[0031] In this specification, the term "linked aromatic group" refers to a group in which aromatic rings of aromatic hydrocarbon groups or aromatic heterocyclic groups are linked by a single bond, and these may be linked in a linear or branched manner, and the aromatic rings may be the same or different. If the group corresponds to a linked aromatic group, it is different from a substituted aromatic hydrocarbon group or a substituted aromatic heterocyclic group.

[0032] R 1independently represent deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Preferably, it is an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms. More preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms. In addition, Ar 1 and R 1 is preferably not a group derived from a pyridine, pyrimidine or triazine.

[0033] a represents an integer of 0 to 4, and b represents an integer of 0 to 3. Preferably, a is an integer of 0 to 1, and b is an integer of 0 to 1.

[0034] R 1 When is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, specific examples include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl. Preferred examples include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl.

[0035] R 1 Specific examples of when Ar is an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or an unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms include the above-mentioned Ar 1 It was just as described.

[0036] In this specification, the substituted aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group may have a substituent, and the substituent is preferably deuterium, a cyano group, a triarylsilyl group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms. When the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear, branched, or cyclic. The number of substituents is 0 to 5, preferably 0 to 2. When the aromatic hydrocarbon group or aromatic heterocyclic group has a substituent, the number of carbon atoms in the substituent is not included in the calculation of the carbon number. However, it is preferable that the total number of carbon atoms, including the carbon atoms in the substituent, satisfies the above range.

[0037] Specific examples of the substituent include cyano, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, etc. Preferred are cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, diphenylamino, naphthylphenylamino, and dinaphthylamino.

[0038] In this specification, it is understood that hydrogen may be deuterium. That is, in general formulas (1) to (4), etc., a skeleton such as carbazole, R 1 and Ar 1 Some or all of the H's in such a substituent may be deuterium.

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

[0040] [ka] [ka] [ka]

[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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[0046] The compound represented by the general formula (2) will be explained below. In general formula (2), c is independently an integer of 0 to 5, d is independently an integer of 0 to 2, and at least one d is 1 or greater. e is independently an integer of 0 to 2. Preferably, c is an integer of 1 to 2, the sum of the two d's is an integer of 1 to 4, and e is an integer of 0 to 1.

[0047] R 2 are independently a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms. Preferably, they are an aliphatic hydrocarbon group having 1 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, and more preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms.

[0048] R 2 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, the following is a specific example: 1 is the same as in these cases.

[0049] R 2 Specific examples of the unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms include the above Ar 1 It was just as described.

[0050] L 2 is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms. More preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms.

[0051] L 2Specific examples of when is an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or an unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms include those in the general formula (1) where Ar 1 The same applies to these cases. Note that the valence may differ. 2 is understood to be a 2d+1 valent group.

[0052] Ar 2 independently represent hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 3 of these. Preferably, it is an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms, or a linked aromatic group formed by linking 2 to 3 of these. More preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a linked aromatic group formed by linking 2 to 3 of these. In addition, Ar 2 , L 2 , R 2 is preferably not a group derived from a pyridine, pyrimidine or triazine.

[0053] Ar 2 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, specific examples thereof include R 1 is the same as in these cases. Also, Ar 2 is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, specific examples of which include Ar 1 is the same as in these cases.

[0054] A preferred embodiment of general formula (2) is formula (8). In formula (8), n is an integer of 1 to 5, and p is an integer of 0 to 1, and preferably, n is an integer of 1 to 2, and p is 0. L 8represents a group derived from benzene, dibenzofuran, or dibenzothiophene. 81 represents hydrogen or a radical derived from benzene, dibenzofuran or dibenzothiophene.

[0055] Specific examples of the compound represented by general formula (2) are shown below, but the compound is not limited to these exemplary compounds.

[0056] [ka] [ka] [ka]

[0057] [ka] [ka] [ka]

[0058] [ka] [ka]

[0059] The compound represented by the general formula (3) will be explained below. In general formula (3), Z 3 is an indolocarbazole ring-containing group represented by formula (3a), and * is L 3 Ring A is a heterocycle represented by formula (3b), and this heterocycle is fused to the adjacent ring at any position. f represents an integer of 1 to 3, and preferably 1. g represents an integer of 0 to 3, and j represents an integer of 0 to 3. Preferably, g is an integer of 0 to 2, and j is an integer of 0 to 2.

[0060] Preferred examples of the general formula (3) include the following formula (9) or formula (10). [ka] In general formula (3), formula (9) and formula (10), common symbols have the same meaning.

[0061] L 3 and L 31 are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Preferably, they are an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 3 to 15 carbon atoms. More preferably, they are groups derived from benzene, naphthalene, pyridine, triazine, dibenzofuran, or carbazole.

[0062] Ar 3 and Ar 31 are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these. Preferably, they are a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 4 of these aromatic rings, and more preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a linked aromatic group formed by linking 2 to 3 of these. Ar 3 and Ar 31 is preferably a phenyl group, a biphenyl group, or a terphenyl group. The terphenyl group may be linearly linked or branched. Benzene, carbazole, and linked aromatic groups in which 2 to 3 of these aromatic rings are linked are preferred.

[0063] L 3 and L 31 or Ar 3 and Ar 31 Specific examples of when is an unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms or an aromatic heterocyclic group having 3 to 17 carbon atoms include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, tetracene, pentacene, hexacene, coronene, heptacene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiazoline, and thiazoline. Examples include groups derived from diazole, 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. However, L 3 and L 31 is a g+f or j+1 valent group. Ar 3 and Ar 31 can be a linking aromatic group, but the linking aromatic group is 1 is a linking aromatic group, except that the aromatic hydrocarbon group constituting the linking aromatic group has 6 to 30 carbon atoms. When these groups have a substituent, the substituent is as follows: 1 The same applies as in the case where the group has a substituent.

[0064] R 3each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Preferably, it is an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms. More preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms. h independently represents an integer of 0 to 4, and i represents an integer of 0 to 2. Preferably, h is an integer of 0 to 1, and i is an integer of 0 to 1.

[0065] R 3 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, R 1 Specific examples of the substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or the substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms are the same as those of the general formula (1), and examples of the substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or the substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms include Ar 1 is the same as in these cases.

[0066] Specific examples of the compound represented by general formula (3) are shown below, but the compound is not limited to these exemplary compounds.

[0067] [ka] [ka] [ka]

[0068] [ka] [ka] [ka]

[0069]

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[0070]

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[0071]

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[0072]

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[0073]

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[0074] [ka] [ka] [ka]

[0075] [ka] [ka]

[0076] The light-emitting dopant used in the organic EL device of the present invention is a polycyclic aromatic compound represented by the general formula (4) or a polycyclic aromatic compound having the structure represented by the general formula (4) as a partial structure. A polycyclic aromatic compound having the structure represented by general formula (4) as a partial structure is also called a partial structure type polycyclic aromatic compound. This partial structure type polycyclic aromatic compound is preferably a polycyclic aromatic compound represented by the above formula (5), and more preferably a boron-containing polycyclic aromatic compound represented by the above formula (6).

[0077] In general formula (4) and general formula (5), ring C, ring D, ring E, ring F, ring G, ring H, ring I, and ring J each independently represent an aromatic hydrocarbon ring having 6 to 24 carbon atoms or an aromatic heterocyclic ring having 3 to 17 carbon atoms, preferably an aromatic hydrocarbon ring having 6 to 20 carbon atoms or an aromatic heterocyclic ring having 3 to 15 carbon atoms. Since rings C to J are aromatic hydrocarbon rings or aromatic heterocyclic rings as described above, they are also referred to as aromatic rings.

[0078] Specific examples of the aromatic ring include rings consisting of benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, 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. More preferred are a benzene ring, a naphthalene ring, an anthracene ring, a triphenylene ring, a phenanthrene ring, a pyrene ring, a pyridine ring, a dibenzofuran ring, a dibenzothiophene ring, and a carbazole ring.

[0079] In general formula (4), Y 4 is B, P, P=O, P=S, Al, Ga, As, Si-R 4 or Ge-R 41 and preferably B, P, P═O or P═S, more preferably B.

[0080] R 4 and R 41 represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Preferably, it is an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms. More preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms.

[0081] R 4and R 41 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, specific examples thereof include R 1 is these groups.

[0082] X 4 are independently O, N-Ar 4 , S or Se, preferably O, N-Ar 4 or S, more preferably O or N-Ar 4 is.

[0083] Ar 4 are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these. Preferably, they represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 6 of these aromatic rings. More preferably, they represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 10 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 4 of these aromatic rings. More preferred are phenyl, biphenyl, and terphenyl groups.

[0084] Ar 4 Specific examples of when is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these groups include Ar 1 is these groups.

[0085] N-Ar 4 may be bonded to an aromatic ring selected from ring C, ring D, or ring E to form a heterocyclic ring containing N.4 , R 41 , R 42 , and Ar 4 At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom.

[0086] R 42 represent substituents of ring C, ring D, and ring E, and each independently represent a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, an arylheteroarylamino group having 12 to 44 carbon atoms, a diheteroarylamino group having 12 to 44 carbon atoms, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Preferred are diarylamino groups having 12 to 36 carbon atoms, arylheteroarylamino groups having 12 to 36 carbon atoms, diheteroarylamino groups having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms. More preferred are diarylamino groups having 12 to 24 carbon atoms, arylheteroarylamino groups having 12 to 24 carbon atoms, diheteroarylamino groups having 12 to 24 carbon atoms, substituted or unsubstituted aromatic hydrocarbon groups having 6 to 10 carbon atoms, and substituted or unsubstituted aromatic heterocyclic groups having 3 to 12 carbon atoms.

[0087] R 42 Specific examples of when R represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms include 1 This is the same as in the case of

[0088] R 42 Specific examples of when represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms include Ar 1The same applies to the case of (1). Preferred examples include groups derived from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, 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. More preferred examples include groups derived from benzene or naphthalene.

[0089] R 42When represents a diarylamino group having 12 to 44 carbon atoms, an arylheteroarylamino group having 12 to 44 carbon atoms, a diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, specific examples thereof include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, di Examples of the alkyl group include benzofuranylnaphthylamino, dibenzofuranylanthranylamino, dibenzofuranylphenanthrenylamino, dibenzofuranylpyrenylamino, bisdibenzofuranylamino, carbazolylphenylamino, carbazolylnaphthylamino, carbazolylanthranylamino, carbazolylphenanthrenylamino, carbazolylpyrenylamino, dicarbazolylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl. Preferred examples include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, and dipyrenylamino. More preferred examples include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dibenzofuranylphenylamino, and carbazolylphenylamino.

[0090] Each v independently represents an integer of 0 to 4, preferably an integer of 0 to 2, more preferably an integer of 0 to 1. x represents an integer of 0 to 3, preferably an integer of 0 to 2, more preferably an integer of 0 to 1.

[0091] The following describes a polycyclic aromatic compound having a structure represented by general formula (4) as a partial structure. This polycyclic aromatic compound having a structure represented by general formula (4) as a partial structure can be considered a condensation product of the compound represented by general formula (4) or an analog thereof, and is therefore also called a partial structure type polycyclic aromatic compound. The partial structure type polycyclic aromatic compound includes the compounds represented by the above formula (5) or formula (6).

[0092] In general formula (4), formula (5) and formula (6), common symbols have the same meaning. In formula (5), w represents an integer of 0 to 4, y represents an integer of 0 to 3, and z represents an integer of 0 to 2. Preferably, w is 0 or 2, y is 0 or 1, and z is 0 or 1.

[0093] In formula (5), rings F to J are as described above. The rings F and G have the same meaning as the rings C and D in general formula (4), the rings H and J have the same meaning as the ring E, and the ring I is a tetravalent group (when z=0) because it is a shared structure.

[0094] In equation (6), X 6 are independently N-Ar 6 , O, or S, but at least one X 6 is N-Ar 6 Preferably, O or N-Ar 5 More preferably, N-Ar 5 Represents Ar 6 is Ar in general formula (4) 4 This is the same as N-Ar. 6 may be bonded to the aromatic ring to form a heterocyclic ring containing N. In this case, Ar 3 may be bonded directly to the aromatic ring or via a linking group.

[0095] R 6 independently represent a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. A specific example is R 42 is the same as in these cases.

[0096] k independently represents an integer of 0 to 4, l independently represents an integer of 0 to 3, and m independently represents an integer of 0 to 2. Preferably, k independently represents an integer of 0 to 2, l independently represents an integer of 0 to 2, and m independently represents an integer of 0 to 1.

[0097] The partial structure type polycyclic aromatic compound will be explained below with reference to formula (5) and formula (6). Formula (5) consists of the structure represented by general formula (4) and a partial structure thereof. From another perspective, there are two structures represented by general formula (4), but they share the I ring. In other words, the structure represented by general formula (4) is a partial structure. Similarly, formula (6) has a structure in which the central benzene ring is shared, but it can be understood to be composed of the structure represented by general formula (4) and a part of its structure. The partial structure type polycyclic aromatic compound referred to in the present invention has a structure represented by general formula (4) as a partial structure. A compound having a structure in which any one of rings C to E in general formula (4) is missing as another partial structure is suitable. A compound having one structure represented by general formula (4) as a partial structure and 1 to 3 of the other partial structures is preferred. The bond between the structure represented by general formula (4) and the other partial structure may be a bond formed by condensation of one or more rings, or a bond formed by one or more bonds.

[0098] Preferred embodiments of the general formula (4), general formula (5) or formula (6), or partial structure type polycyclic aromatic compounds include the following formulae (4-a) to (4-h). [ka]

[0099] The partial structure type polycyclic aromatic compound represented by the above formula (4-a) corresponds to a compound represented by the formula (4-64) described below, for example. That is, the formula (4-a) has a structure in which two structures of the general formula (4) are shared by the central benzene ring, but it is understood that the compound contains the structural unit of the general formula (4) and one partial structure thereof.

[0100] The partial structure type polycyclic aromatic compound represented by formula (4-b) corresponds to a compound represented by formula (4-65) described later, for example. That is, formula (4-b) has a structure in which two structures of general formula (4) are shared by the central benzene ring, but it is understood that it is a compound containing a structural unit of general formula (4) and one partial structure thereof. In terms of general formula (4), X 4 One of them is NAr 4 This is then bonded to another aromatic ring to form a ring (fused ring structure).

[0101] The partial structure type polycyclic aromatic compound represented by formula (4-c) corresponds to, for example, a compound represented by formula (4-66) described later. That is, in terms of general formula (4), it has a structure having three unit structures represented by general formula (4) so ​​as to share the benzene ring E. That is, it is understood that it is a compound having the unit structure represented by general formula (4) as a partial structure, and also containing two partial structures which are structures obtained by removing one benzene ring from general formula (4). In addition, X 4 N-Ar 4 This is bonded to the other adjacent ring to form a ring.

[0102] [ka]

[0103] Furthermore, the partial structure type polycyclic aromatic compounds represented by formula (4-d), formula (4-e), formula (4-f), and formula (4-g) correspond to compounds represented by formula (4-67), formula (4-68), formula (4-69), and formula (4-70) described later, for example. That is, it is a compound having two or three unit structures represented by general formula (4) in one compound, sharing a benzene ring, which is ring C (or ring D). That is, it is understood to be a compound having a unit structure represented by general formula (4) as a partial structure, and including one partial structure that is a structure obtained by removing one benzene ring from general formula (4).

[0104] The partial structure polycyclic aromatic compound represented by formula (4-h) corresponds to compounds represented by formulas (4-71), (4-72), (4-73), (4-74), and (4-75) described below. That is, in terms of general formula (4), the C ring is a naphthalene ring, and the partial structure polycyclic aromatic compound has two unit structures represented by general formula (4) in one compound, sharing the ring. That is, it is understood to be a compound having the unit structure represented by general formula (4) as a partial structure, and containing one or two partial structures that are the structure of general formula (4) minus one C ring (naphthalene ring).

[0105] In formulas (4-a) to (4-h), X 4 and Y 4 is the same as general formula (4), and R 6 , k, l, and m have the same meanings as in formula (6). s is 0 to 1, and is preferably 0.

[0106] The partial structure type polycyclic aromatic compound of the present invention has a structure in which a plurality of compounds of general formula (4) are linked together by sharing one or two of the rings (ring C to ring E) in the structural unit of general formula (4), and can be said to contain at least one structural unit of general formula (4). The number of compounds of general formula (4) forming the above structure is 2 to 5, preferably 2 to 3. The number of shared rings (rings C to E) may be one, two, or three.

[0107] Specific examples of polycyclic aromatic compounds represented by general formula (4), general formula (5), or formula (6) and other partial structure type polycyclic aromatic compounds are shown below, but are not limited to these exemplary compounds.

[0108] [ka] [ka] [ka]

[0109]

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[0110]

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[0111]

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[0112]

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[0113]

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[0114] The organic light-emitting material used as a light-emitting dopant in the organic EL device of the present invention preferably has a ΔEST of 0.20 eV, more preferably 0.15 eV or less, and even more preferably 0.10 eV.

[0115] ΔEST represents the difference between the excited singlet energy (S1) and the excited triplet energy (T1), where the measurement conditions for S1 and T1 are the same as those described in the Examples.

[0116] An excellent organic EL device can be provided by using a material selected from the polycyclic aromatic compounds or partial structure polycyclic aromatic compounds represented by the general formula (3) (hereinafter also referred to as a polycyclic aromatic compound material) as a light-emitting dopant, a material selected from the compounds represented by the general formula (1) or (2) as a first host, and a material selected from the compounds represented by the general formula (3) as a second host.

[0117] In another embodiment of the present invention, a compound having a ΔEST of 0.20 eV or less is used as the luminescent dopant together with the first host and second host. In this case, the compound used as the luminescent dopant does not need to be the polycyclic aromatic compound material described above, but may be any compound having a ΔEST of 0.20 eV or less, preferably 0.15 eV or less, and more preferably 0.10 eV or less. Such compounds are known as delayed fluorescent materials (TADF) in many documents, such as Patent Document 2, and can be selected from these.

[0118] 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.

[0119] FIG. 1 is a cross-sectional view showing an example of the structure of a typical organic EL device used in the present invention, where 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents an emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. The organic EL device of the present invention may have an exciton blocking layer adjacent to the emitting layer, or an electron blocking layer between the emitting layer and the hole injection layer. The exciton blocking layer can be inserted on either the anode side or the cathode side of the emitting layer, or both layers can be inserted simultaneously. The organic EL device of the present invention has an anode, an emitting layer, and a cathode as essential layers, but may also have a hole injection transport layer and an electron injection transport layer in addition to the essential layers, and may further have a hole blocking layer between the emitting layer and the electron injection transport layer. Note that the hole injection transport layer refers to either the hole injection layer or the hole transport layer, or both, and the electron injection transport layer refers to either the electron injection layer or the electron transport layer, or both.

[0120] It is also possible to have the reverse structure to that shown in Figure 1, i.e., to stack the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, and anode 2 on the substrate 1 in this order, and in this case too, layers can be added or omitted as necessary.

[0121] -substrate- The organic EL device of the present invention is preferably supported by 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.

[0122] -anode- Anode materials for organic EL devices are preferably metals, alloys, electrically conductive compounds, or mixtures thereof with a high work function (4 eV or higher). Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO. Amorphous materials capable of forming transparent conductive films, such as IDIXO (In2O3-ZnO), may also be used. The anode may be formed by forming a thin film of these electrode materials by methods such as vapor deposition or sputtering, followed by photolithography to form a desired pattern. Alternatively, if pattern precision is not required (approximately 100 μm or higher), a pattern may be formed using a mask of the desired shape during vapor deposition or sputtering of the electrode material. Alternatively, when a coatable material such as an organic conductive compound is used, wet film formation methods such as printing or coating can be used. When light is emitted from this anode, a transmittance of more than 10% is desirable, and the sheet resistance of the anode is preferably less than several hundred Ω / □. The film thickness varies depending on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

[0123] -cathode- On the other hand, cathode materials are typically made of metals (referred to as electron-injecting metals), alloys, electrically conductive compounds, or mixtures thereof with a low work function (4 eV or less). Specific examples of such electrode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, indium, lithium / aluminum mixtures, and rare earth metals. Among these, mixtures of electron-injecting metals and stable second metals with higher work functions, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, lithium / aluminum mixtures, and aluminum, are preferred in terms of electron injection properties and durability against oxidation. Cathode materials can be fabricated by forming thin films of these cathode materials using methods such as vapor deposition or sputtering. Furthermore, the cathode preferably has a sheet resistance of several hundred Ω / □ or less, and the film thickness is typically selected from the range of 10 nm to 5 μm, preferably 50 to 200 nm. It is advantageous if either the anode or cathode of the organic EL element is transparent or semi-transparent to allow the emitted light to pass through, as this improves the luminance of the emitted light.

[0124] Furthermore, a transparent or semitransparent cathode can be fabricated by forming the above-mentioned metal in a thickness of 1 to 20 nm on the cathode 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.

[0125] -Emitting layer- The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and cathode, respectively, and contains a light-emitting dopant and a host. The light-emitting dopant and the host can be used so that the light-emitting dopant accounts for 0.10 to 10% and the host accounts for 99.9 to 90%, for example, preferably 1.0 to 5.0% of the light-emitting dopant and 99 to 95% of the host, and more preferably 1.0 to 3.0% of the light-emitting dopant and 99 to 97% of the host. In this specification, % means % by mass unless otherwise specified.

[0126] The hosts used in the light-emitting layer are a first host represented by general formula (1) or (2) and a second host represented by general formula (3). The first host and second host can be used in a ratio of, for example, 10 to 90% first host and 90 to 10% second host. Preferably, the ratio is 30 to 70% first host and 70 to 30% second host, and more preferably 40 to 60% first host and 60 to 40% second host. Furthermore, as other hosts than those mentioned above, one or more known hosts may be used in combination, but the amount used should be 50% or less, preferably 25% or less, of the total amount of the host materials.

[0127] The host is preferably a compound having hole transport capability, electron transport capability, and a high glass transition temperature, and has a T1 greater than that of the luminescent dopant. Specifically, the T1 of the host is preferably at least 0.010 eV higher than that of the luminescent dopant, more preferably at least 0.030 eV higher, and even more preferably at least 0.10 eV higher. A TADF-active compound may also be used as the host material, and this compound preferably has a difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of 0.20 eV or less.

[0128] Known hosts as the other host can be selected from many known in patent documents, etc. Specific examples of the host include, but are not limited to, indole derivatives, carbazole derivatives, indolocarbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, phenylenediamine derivatives, arylamine derivatives, styrylanthracene derivatives, fluorenone derivatives, stilbene derivatives, triphenylene derivatives, carborane derivatives, porphyrin derivatives, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metal phthalocyanines, various metal complexes typified by metal complexes of benzoxazole and benzothiazole derivatives, poly(N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylenevinylene derivatives, and polyfluorene derivatives.

[0129] When multiple types of hosts are used, each host can be vapor-deposited from a different vapor deposition source, or multiple hosts can be simultaneously vapor-deposited from one vapor deposition source by premixing them before vapor deposition to form a premixture.

[0130] The premixing method is preferably a method that allows mixing as uniformly as possible, and examples thereof 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.

[0131] The light-emitting dopant in the light-emitting layer may be any of the above polycyclic aromatic compound materials or organic light-emitting materials having a ΔEST of 0.20 eV or less, preferably any of the above polycyclic aromatic compound materials having a ΔEST of 0.20 eV or less.

[0132] The light-emitting dopant in the light-emitting layer may be the above-mentioned polycyclic aromatic compound material. Preferably, it is a partial structure polycyclic aromatic compound represented by the above formula (5), and more preferably, it is a boron-containing partial structure polycyclic aromatic compound represented by the above formula (6). The ΔEST of the above-mentioned polycyclic aromatic compound material is preferably 0.20 eV or less.

[0133] The light-emitting layer may contain two or more light-emitting dopants. For example, the light-emitting layer may contain the polycyclic aromatic compound material and a light-emitting dopant composed of another compound. In this case, the light-emitting dopant composed of the other compound preferably has a ΔEST of 0.20 eV or less, but is not limited thereto.

[0134] When two or more types of luminescent dopants are contained in the luminescent layer, the first dopant is the polycyclic aromatic compound material described above, and the second dopant may be a known compound used in combination as another luminescent dopant. The content of the first dopant is preferably 0.05 to 50% of the host material, and the content of the second dopant is preferably 0.050 to 50% of the host material, and the total content of the first dopant and the second dopant does not exceed 50% of the host material.

[0135] Such other luminescent dopants can be selected from among those known in numerous patent documents, etc. Specific examples of the dopant include, but are not limited to, fused ring derivatives such as phenanthrene, anthracene, pyrene, tetracene, pentacene, perylene, naphthopyrene, dibenzopyrene, rubrene, and chrysene, benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, benzotriazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, imidazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazoline derivatives, stilbene derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives, bisstyrylarylene derivatives, diazaindacene derivatives, furan derivatives, benzofuran derivatives, and the like. Examples of the benzofluorene derivatives include benzophenone derivatives, isobenzofuran derivatives, dibenzofuran derivatives, coumarin derivatives, dicyanomethylenepyran derivatives, dicyanomethylenethiopyran derivatives, polymethine derivatives, cyanine derivatives, oxobenzoanthracene derivatives, xanthene derivatives, rhodamine derivatives, fluorescein derivatives, pyrylium derivatives, carbostyril derivatives, acridine derivatives, oxazine derivatives, phenylene oxide derivatives, quinacridone derivatives, quinazoline derivatives, pyrrolopyridine derivatives, furopyridine derivatives, 1,2,5-thiadiazolopyrene derivatives, pyrromethene derivatives, perinone derivatives, pyrrolopyrrole derivatives, squarylium derivatives, violanthrone derivatives, phenazine derivatives, acridone derivatives, deazaflavin derivatives, fluorene derivatives, and benzofluorene derivatives.

[0136] The organic luminescent dopant and the first host or the second host can be deposited from different deposition sources, or they can be premixed before deposition to form a premixture, allowing the luminescent dopant and the first host or the second host to be simultaneously deposited from a single deposition source.

[0137] -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 needed.

[0138] -Hole blocking layer- In a broad sense, a hole-blocking layer functions as an electron-transporting layer and is made of a hole-blocking material that has the ability to transport electrons but has a significantly lower ability to transport holes. By transporting electrons while blocking holes, the hole-blocking layer can improve the probability of electron-hole recombination in the light-emitting layer. Known hole-blocking materials can be used for the hole-blocking layer. To maximize the properties of the light-emitting dopant, the material used as the second host can also be used as the material for the hole-blocking layer. Multiple hole-blocking materials can also be used in combination.

[0139] -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 can improve the probability of electron and hole recombination in the light-emitting layer. Known electron blocking layer materials can be used as the material for the electron blocking layer. To bring out the properties of the light-emitting dopant, the material used as the first host can also be used as the material for the electron blocking layer. The thickness of the electron blocking layer is preferably 3 to 100 nm, more preferably 5 to 30 nm.

[0140] -Exciton blocking layer- The exciton-blocking layer is a layer that prevents excitons generated by the recombination of holes and electrons in the light-emitting layer from diffusing into the charge-transporting layer. Inserting this layer makes it possible to efficiently confine excitons within the light-emitting layer, thereby improving the luminous efficiency of the device. In devices with two or more adjacent light-emitting layers, the exciton-blocking layer can be inserted between two adjacent light-emitting layers. As the material for the exciton blocking layer, known exciton blocking layer materials can be used.

[0141] Layers adjacent to the light-emitting layer include a hole-blocking layer, an electron-blocking layer, an exciton-blocking layer, etc., but if these layers are not provided, the adjacent layers are a hole-transporting layer, an electron-transporting layer, etc.

[0142] -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.

[0143] The hole transport material has either hole injection or transport properties or electron barrier properties, and may be either organic or inorganic. Any conventionally known compound can be selected and used for the hole transport layer. Examples of such hole transport materials include porphyrin derivatives, 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. Porphyrin derivatives, arylamine derivatives, and styrylamine derivatives are preferred, and arylamine compounds are more preferred.

[0144] -Electron transport layer- The electron transport layer is made of a material having the function of transporting electrons, and the electron transport layer may be a single layer or a plurality of layers.

[0145] 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 a variety 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, 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 incorporated into a polymer chain or in which these materials form the polymer backbone may also be used.

[0146] When the organic EL device 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. [Example]

[0147] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0148] The compounds used in the examples and comparative examples are as follows: Examples 1 to 8 and 10 to 16 are reference examples. [ka]

[0149] The S1 and T1 of the compounds (4-2) and (4-110) were measured. S1 and T1 were measured as follows. Vacuum deposition method on a quartz substrate at a vacuum level of 10 -4Compound (2-30) as a host and compound (4-2) or (4-110) as an emitting dopant were co-deposited from different evaporation sources to form a 100 nm thick evaporated film under conditions of ≤ Pa. The co-deposition was carried out under evaporation conditions such that the concentration of compound (4-2) or (4-110) was 3%. 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 this emission spectrum, and substituting the wavelength value λedge [nm] at the intersection of this tangent and the horizontal axis into the following formula (i). S1[eV] = 1239.85 / λedge (i) T1 is calculated by measuring the phosphorescence spectrum of the above-mentioned 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 and the horizontal axis into formula (ii). T1[eV] = 1239.85 / λedge (ii)

[0150] The measurement results are shown in Table 1. [Table 1]

[0151] Example 1 Each thin film was deposited by vacuum deposition on a glass substrate with an anode made of ITO with a film thickness of 70 nm at a vacuum of 4.0 × 10 -5The layers were laminated at 1000 Pa. First, HAT-CN 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 25 nm. Next, compound (1-77) was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1-77) was formed as a first host, compound (3-3) as a second host, and compound (4-110) as an emissive dopant, each co-deposited from a different evaporation source, to form an emitting layer to a thickness of 30 nm. The co-deposition conditions were a concentration of compound (4-110) of 2% and a weight ratio of the first host to the second host of 50:50. Next, compound (HB1) was formed as a hole blocking layer to a thickness of 5 nm. Next, ET-1 was formed as an electron transport layer to a thickness of 40 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 to fabricate an organic EL device.

[0152] Examples 2 to 16 An organic EL device was fabricated in the same manner as in Example 1, except that the light-emitting dopant, the first host, the second host, and the weight ratio of the first host to the second host were the compounds shown in Table 2.

[0153] Comparative Example 1 Each thin film was deposited by vacuum deposition on a glass substrate with an anode made of ITO with a film thickness of 70 nm at a vacuum of 4.0 × 10 -5The layers were laminated at 1000 W / m². First, HAT-CN was formed as a hole-injection layer on ITO to a thickness of 10 nm, followed by HT-1 as a hole-transport layer to a thickness of 25 nm. Next, compound (2-30) was formed as an electron-blocking layer to a thickness of 5 nm. Next, compound (1-77) as a first host and compound (4-110) as an emissive dopant were co-deposited from different evaporation sources to form an emissive layer to a thickness of 30 nm. The co-deposition was carried out under evaporation conditions that resulted in a 2% concentration of compound (4-110). Next, compound (HB1) was formed as a hole-blocking layer to a thickness of 5 nm. Next, ET-1 was formed as an electron-transport layer to a thickness of 40 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 to fabricate an organic EL device.

[0154] Comparative Examples 2, 3, 4, 7, 8, and 9 An organic EL device was prepared in the same manner as in Comparative Example 1, except that the light-emitting dopant and the first host (no second host) were the compounds shown in Table 2.

[0155] Comparative Examples 5, 6, and 10 Organic EL devices were fabricated in the same manner as in Example 1, except that the light-emitting dopant, first host, and second host were compounds shown in Table 2.

[0156] [Table 2]

[0157] The voltage, maximum emission wavelength of the emission spectrum, external quantum efficiency, and lifespan of the organic EL devices fabricated in the examples and comparative examples are shown in Table 3. The voltage, maximum emission wavelength, and external quantum efficiency were 2 The value is the initial value, and is the initial characteristic. 2 The time it took for the brightness to decay to 50% of the initial brightness was measured.

[0158] [Table 3]

[0159] From Table 3, it can be seen that the organic EL devices of the examples of the present invention have high efficiency and long life characteristics, and that they emit blue light based on the maximum emission wavelength. [Explanation of symbols]

[0160] 1 substrate, 2 anode, 3 hole injection layer, 4 hole transport layer, 5 light-emitting layer, 6 electron transport layer, 7 cathode

Claims

1. An organic electroluminescent device comprising one or more emitting layers between an anode and a cathode facing each other, wherein at least one emitting layer comprises a host and a luminescent dopant, the host comprises a first host represented by general formula (1) and a second host represented by general formula (3), and the luminescent dopant comprises a polycyclic aromatic compound represented by general formula (4). 【Chemical 1】 Here, Y １ is O, S, or N-Ar １ Represents. Ar １ each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these aromatic rings. R １ each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. a independently represents an integer of 0 to 4; b independently represents an integer of 0 to 3; 【Chemistry 2】 Here, Z ３ is an indolocarbazole ring-containing group represented by formula (3a), * is L ３ is the bonding position with Ring A is a heterocycle represented by formula (3b) and is fused to the adjacent ring at any position. L ３ and L ３１ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Ar ３ and Ar ３１ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these. R ３ are independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. f represents an integer of 1 to 3; g represents an integer of 0 to 3; h independently represents an integer of 0 to 4; i represents an integer of 0 to 2; and j represents an integer of 0 to 3. 【Chemistry 3】 wherein ring C, ring D, and ring E are independently an aromatic hydrocarbon ring having 6 to 24 carbon atoms or an aromatic heterocyclic ring having 3 to 17 carbon atoms; Y ４ is B, P, P=O, P=S, AL, Ga, As, Si-R ４ , or Ge-R ４１ and X ４ are independently O, N-Ar ４ , S, or Se; R ４ , and R ４１ each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, Ar ４ are independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these, and N-Ar ４ may be bonded to any of ring C, ring D, or ring E to form a heterocycle containing N, R ４２ each independently represent a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, an arylheteroarylamino group having 12 to 44 carbon atoms, a diheteroarylamino group having 12 to 44 carbon atoms, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, Each v independently represents an integer of 0 to 4; x represents an integer of 0 to 3; C ring, D ring, E ring, R ４ , R ４１ , R ４２ , and Ar ４ At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom.

2. Y in general formula (1) １ is N-Ar １ 2. The organic electroluminescent device according to claim 1, wherein

3. 3. The organic electroluminescent device according to claim 1, wherein the general formula (1) is the following formula (7): 【Chemistry 4】 Here, Ar １ has the same meaning as general formula (1).

4. 4. The organic electroluminescent device according to claim 1, wherein f in general formula (3) is 1.

5. 5. The organic electroluminescent device according to claim 1, wherein the light-emitting dopant has a difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of 0.20 eV or less.

6. 6. The organic electroluminescent device according to claim 5, wherein the ΔEST is 0.10 eV or less.

7. 7. The organic electroluminescent device according to claim 1, wherein the host is contained in an amount of 99.9 to 90 wt % relative to 0.10 to 10 wt % of the luminescent dopant, and the host contains the first host in an amount of 10 to 90 wt % and the second host in an amount of 90 to 10 wt %.

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