Organic electroluminescent device

Abstract

Provided is a blue-light-emitting organic electroluminescent (EL) element which has a high luminescent efficiency and a long life. This organic EL element comprises an anode and a cathode which face each other and one or more luminescent layers interposed therebetween, wherein at least one of the luminescent layers comprises one or more hosts selected from among indolocarbazole compounds represented by general formula (1) and a light-emitting dopant that is either a polycyclic aromatic compound having a structure represented by general formula (2) or a polycyclic aromatic compound including said structure as a partial structure. In the formulae, Z is a group including an indolocarbazole ring, X1 is O, N-Ar3, S, or Se, and Y1 is B, P, P=O, P=S, Al, Ga, As, Si-R2, or Ge-R3.

Description

[Technical Field]

[0001] The present invention relates to an organic electroluminescent device (hereinafter 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] More recently, highly efficient organic EL devices utilizing delayed fluorescence have been developed. For example, Patent Document 1 discloses an organic EL device utilizing the TTF (Triplet-Triplet Fusion) mechanism, which is one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon in which singlet excitons are generated by the collision of two triplet excitons, and is thought to theoretically increase the internal quantum efficiency to 40%. However, since the efficiency is lower than that of phosphorescent organic EL devices, further improvements in efficiency are required. On the other hand, 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 materials 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 lifespan characteristics are required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2010 / 134350 publication [Patent Document 2] WO2011 / 070963 publication [Patent Document 3] WO2015 / 102118 publication [Patent Document 4] WO2018 / 212169 publication [Patent Document 5] WO2014 / 166585 publication [Patent Document 6] WO2016 / 042997 publication

[0005] Patent Documents 3 and 4 disclose highly efficient organic EL devices that emit blue light by using a TADF material made of a polycyclic aromatic compound, such as the compound shown below, as a light-emitting dopant and a material made of a carbazole ring-containing compound as a host, but do not specifically disclose life characteristics. [ka]

[0006] Patent Document 5 discloses an organic EL device that uses a TADF material as a light-emitting dopant and a material made of an indolocarbazole ring-containing compound as a host, but does not demonstrate the usefulness of the present invention.

[0007] Patent Document 6 discloses an organic EL device that uses a premixed material of two or more indolocarbazole ring-containing compounds as a host, but does not disclose a device that uses a TADF material composed of the above-mentioned polycyclic aromatic compound as a light-emitting dopant. Summary of the Invention

[0008] 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 and at the same time ensure a device life sufficient for practical use. An object of the present invention is to provide a practically useful organic EL element that has high efficiency and long life despite a low driving voltage.

[0009] The present invention provides an organic electroluminescent device comprising one or more light-emitting layers between an anode and a cathode facing each other, wherein at least one of the light-emitting layers contains one or more hosts selected from compounds represented by the following general formula (1), and contains, as a light-emitting dopant, a polycyclic aromatic compound represented by the following general formula (2) or a polycyclic aromatic compound having a structure represented by the general formula (2) as a partial structure:

[0010] [ka] wherein Z is an indolocarbazole ring-containing group represented by formula (1a), * is L 1 is the bonding position with Ring A is a heterocycle represented by formula (1b), and ring A is fused to the adjacent ring at any position. L 1 and L 2 each independently represents 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 1 and Ar 2 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 1 are each 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. a represents an integer of 1 to 3; b represents an integer of 0 to 3; c and d each independently represent an integer of 0 to 4; e represents an integer of 0 to 2; and f represents an integer of 0 to 3.

[0011] [ka] wherein ring C, ring D, and ring E are each independently an aromatic hydrocarbon ring having 6 to 24 carbon atoms or an aromatic heterocyclic ring having 3 to 17 carbon atoms; Y 1 is B, P, P=O, P=S, Al, Ga, As, Si-R 2 or Ge-R 3 and R 2 and R 3 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, X 1 are independently O, N-Ar 3 , S or Se; Ar 3 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, and N-Ar 3 may be bonded to any of ring C, ring D, or ring E to form a heterocycle containing N, C ring, D ring, E ring, R 2 , R 3 , R 6 and Ar 3 At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom. R 6 represent substituents of ring C, ring D, and ring E, each independently representing 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;

[0012] Examples of polycyclic aromatic compounds having the structure represented by the general formula (2) as a partial structure include polycyclic aromatic compounds represented by the following formula (3) and boron-containing polycyclic aromatic compounds represented by the following formula (4). [ka] wherein ring F, ring G, ring H, ring I and ring J are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 24 carbon atoms or a substituted or unsubstituted aromatic heterocycle having 3 to 17 carbon atoms; Y 2 is Y in the above general formula (2) 1 I agree with this. X 2 is X in the above general formula (2) 1 I agree with this. At least one hydrogen atom in rings F, G, H, I, and J may be substituted with halogen or deuterium. R 6 , x, and v are defined as in the general formula (2), 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.

[0013] [ka] where X 3 are each independently N-Ar 5 , O, or S, but at least one X 3 is N-Ar 5 Represents. Ar 5 N-Ar 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. 5 is X 3may be bonded to any of the aromatic rings to which it is bonded to form a heterocyclic ring containing N. R 61 each independently represents 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. g and h each independently represent an integer of 0 to 4; i and j each independently represent an integer of 0 to 3; k represents an integer of 0 to 2;

[0014] The light-emitting layer may contain two or more types of hosts selected from the compounds represented by the general formula (1). At least one of the hosts selected from the compounds represented by the general formula (1) is L 1 and L 2 It is preferable that only one of them is a nitrogen-containing aromatic heterocyclic group having 3 to 17 carbon atoms.

[0015] The light-emitting layer may contain, as hosts selected from the compounds represented by general formula (1), a first host represented by formula (5a) or (5b) below and a second host represented by formula (6) below. [ka] where Z, Ar 1 , a and b have the same meanings as in general formula (1). X 4 represents O or S. b1 represents an integer of 0 to 2, and is one less than the above b. X 5 are each independently N, CH, C-, or CR 7 and at least one X 5 represents N. X 5 When is C-, Ar 1 and combine. R 7 each independently represents a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms.

[0016] At least one host selected from the compounds represented by the general formula (1) may be a compound represented by the following formula (7) or formula (8), and is preferably a compound represented by formula (7). [ka] where L 1 , L 2 , Ar 1 , Ar 2 , b and f have the same meanings as in the general formula (1) above.

[0017] The difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of the luminescent dopant is preferably 0.20 eV or less, and more preferably 0.10 eV or less.

[0018] The light-emitting layer preferably contains 0.10 to 10 mass % of the light-emitting dopant and 99.9 to 90 mass % of the host, and more preferably contains 10 to 90 mass % of the first host and 90 to 10 mass % of the second host in the host.

[0019] The organic EL device of the present invention contains a specific luminescent dopant and host material in the luminescent layer, thereby achieving high luminescent efficiency and a long lifetime despite a low driving voltage. The low driving voltage of the organic EL device is believed to be due to the fact that the indolocarbazole compound host material has the property of easily injecting holes. Furthermore, the use of two or more host materials, each made of an indolocarbazole compound, with different electron or hole injection and transport properties in the luminescent layer allows for a more precise balance between holes and electrons, resulting in an organic EL device with higher luminescent efficiency. The long lifetime of the organic EL device of the present invention is believed to be due to the preferential injection of holes or electrons into the host made of the indolocarbazole compound when a voltage is applied to the organic EL device, thereby reducing the electrochemical load on the luminescent dopant. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an organic EL element. DETAILED DESCRIPTION OF THE INVENTION

[0021] The organic EL device of the present invention comprises one or more emitting layers between an anode and a cathode facing each other, and at least one emitting layer contains a host and a luminescent dopant. The host contains one or more hosts selected from the compounds represented by the general formula (1). The light-emitting dopant contains a polycyclic aromatic compound represented by the general formula (2) or a polycyclic aromatic compound having the structure represented by the general formula (2) as a partial structure.

[0022] The compound represented by the general formula (1) used as the host will be explained below. In general formula (1), Z is an indolocarbazole ring-containing group represented by formula (1a), ring A is a heterocycle represented by formula (1b), and the heterocycle of ring A is fused to the adjacent ring at any position.

[0023] L 1 and L 2 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 an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 3 to 15 carbon atoms. L 1 and L 2 It is preferable that one of the groups is a nitrogen-containing aromatic heterocyclic group having 3 to 17 carbon atoms.

[0024] When two or more compounds represented by general formula (1) are used, L of at least one of the compounds 1 and L 2 It is preferable that one of the groups is a substituted or unsubstituted nitrogen-containing aromatic heterocyclic group having 3 to 17 carbon atoms.

[0025] L1 and L 2 Specific examples of when is an unsubstituted aromatic hydrocarbon group or an aromatic heterocyclic group 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, thiadiazole, pyrazinone, and the like. Examples of suitable groups include groups derived from benzene, 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. Here, the term "derived group" refers to a group derived by removing a specified number of hydrogen atoms from these compounds. 1 and L 2 are a + b valent group and a + d valent group, respectively.

[0026] More preferred are groups derived from benzene, naphthalene, pyridine, triazine, dibenzofuran, or carbazole.

[0027] Ar 1 and Ar 2 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 15 carbon atoms, or a linked aromatic group formed by linking 2 to 4 of these, 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.

[0028] Ar 1 and Ar 2 Specific 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, tetracene, pentacene, hexacene, coronene, heptacene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, and isoxa Examples of the group include a group obtained by removing one hydrogen atom from benzole, 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, carbazole, or a compound formed by linking 2 to 8 of these. Preferred examples include a group obtained by removing one hydrogen atom from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, pyridine, pyrimidine, triazine, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or a compound formed by linking 2 to 4 of these. More preferred are groups formed by removing one hydrogen from benzene, pyridine, pyrimidine, triazine, dibenzofuran, dibenzothiophene, carbazole, or a compound formed by linking two or three of these.

[0029] Ar 1 and Ar 2 is preferably a phenyl group, a biphenyl group, or a terphenyl group. The terphenyl group may be linearly linked or branched.

[0030] R 1each 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.

[0031] 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.

[0032] R 1Specific 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 benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, and isopropyl. Examples include groups formed by removing one hydrogen from 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, and carbazole. Preferred examples include groups formed by removing one hydrogen atom 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. Preferred examples include groups derived from benzene, naphthalene, 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, and carbazole.

[0033] In this specification, the unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group as described above may each have a substituent. When the group has a substituent, 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, the substituent 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 number of carbon atoms. However, it is preferable that the total number of carbon atoms, including the number of carbon atoms in the substituent, falls within the above range.

[0034] Specific examples of the substituent include 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.

[0035] In this specification, a linking aromatic group refers to an aromatic group in which carbon atoms in the aromatic rings of the aromatic group are linked together by a single bond. It is an aromatic group in which two or more aromatic groups are linked together, and these may be linear or branched. 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. An aromatic group that corresponds to a linking aromatic group is different from a substituted aromatic group.

[0036] 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.

[0037] In general formula (1), a represents an integer of 1 to 3, b represents an integer of 0 to 3, and f represents an integer of 0 to 3. Preferably, a is 1 to 2, b is 0 to 2, and f is 0 to 2. c and d each independently represent an integer of 0 to 4, and e represents an integer of 0 to 2. Preferably, c and d each independently represent 0 or 1.

[0038] The light-emitting layer contains one or more compounds represented by general formula (1), preferably two or more. More preferably, the first host is represented by formula (5a) or formula (5b), and the second host is a compound represented by formula (6). In the general formula (1) and the formula (5a), (5b), or (6), the common symbols have the same meaning.

[0039] In formula (5a), X 4 represents O or S. In formula (5b), b1 is an integer of 0 to 2, and is a number that is 1 less than b. In equation (6), X 5 are each independently N, CH, C-, or CR 7 and at least one X 5 represents N. X 5 When is C-, Ar1 Combine with R 7 R independently represents a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms. 7 Specific examples of the group can be understood from the above description of the substituents.

[0040] A preferred embodiment of general formula (1) is the above formula (7) or formula (8), with formula (7) being more preferred. In general formula (1), formula (7), and formula (8), common symbols have the same meaning.

[0041] Specific examples of the compound represented by general formula (1) are shown below, but the compound is not limited to these exemplary compounds.

[0042] [ka] [ka] [ka]

[0043] [ka] [ka] [ka]

[0044] [ka] [ka] [ka]

[0045]

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[0046]

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[0047]

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[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055] [ka] [ka]

[0056] The light-emitting dopant used in the organic EL device of the present invention is a polycyclic aromatic compound represented by the general formula (2) above or a polycyclic aromatic compound having the structure represented by the general formula (2) above as a partial structure. The polycyclic aromatic compound having the structure represented by general formula (2) as a partial structure is preferably a polycyclic aromatic compound represented by the general formula (3), and more preferably a boron-containing polycyclic aromatic compound represented by the formula (4).

[0057] In general formula (2) and general formula (3), 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, and 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.

[0058] 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.

[0059] R 6 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.

[0060] R 6 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

[0061] R 6 Specific examples of when represents an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or an unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, and isopropyl. Examples include groups formed by removing one hydrogen from 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, and carbazole. 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.

[0062] R 6 Specific examples of when 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 include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, dibenzofuranylnaphthylamino, dibenzofuranylanthranylamino, dibenzofuranylphenanthrenylamino, dibenzofuranylpyrenylamino, bisdibenzofuranylamino, carbazolylphenylamino, carbazolylnaphthylamino, carbazolylanthranylamino, carbazolylphenanthrenylamino, carbazolylpyrenylamino, dicarbazolylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl. Preferred are diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, and dipyrenylamino. More preferred are diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dibenzofuranylphenylamino, and carbazolylphenylamino.

[0063] Each v independently represents an integer of 0 to 4, preferably an integer of 0 to 2, and more preferably 0 to 1. x represents an integer of 0 to 3, preferably an integer of 0 to 2, and more preferably 0 to 1.

[0064] Y 1 is B, P, P=O, P=S, Al, Ga, As, Si-R 2 or Ge-R 3 and preferably B, P, P=O or P=S, and more preferably B.

[0065] R 2and R 3 independently represent 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, they are 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, they are 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.

[0066] R 2 and R 3 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or an unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, specific examples of which include R 1 is the same as in these cases.

[0067] X 1 are independently O, N-Ar 3 , S or Se, preferably O, N-Ar 3 or S, more preferably O or N-Ar 3 is.

[0068] Ar 3 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 are 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 are 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.

[0069] Specific examples of unsubstituted aromatic hydrocarbon groups, aromatic heterocyclic groups, or linking 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, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, and isoquinoline. , quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or a group formed by removing one hydrogen atom from 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 by linking benzene or a compound formed by linking 2 to 3 of these.

[0070] These unsubstituted aromatic hydrocarbon groups, aromatic heterocyclic groups, and linking aromatic groups may each have a substituent, which, when substituted, is a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms, as described above.

[0071] N-Ar 3 may be bonded to any of ring C, ring D, or ring E to form a heterocycle containing N. In addition, ring C, ring D, ring E, and R 2 , R 3 , R 6 and Ar 3 At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom.

[0072] A polycyclic aromatic compound having a structure represented by general formula (2) as a partial structure (hereinafter also referred to as a partial structure type polycyclic aromatic compound) will be described. The partial structure type polycyclic aromatic compound includes the compounds represented by the above general formula (3) or (4).

[0073] In general formula (2), general formula (3) and formula (4), common symbols have the same meaning. In general formula (3), X 2 is X in general formula (2) 1 has the same meaning as Y 2 is Y in general formula (2) 1 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.

[0074] Ring F, ring G, ring H, ring I and ring J are aromatic rings as described above, and each independently represents a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 24 carbon atoms or a substituted or unsubstituted 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. Specifically, the same applies as for rings C to E in general formula (2). The rings F and G have the same meaning as the rings C and D in general formula (2), 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.

[0075] In equation (4), X 3 are each independently N-Ar 5 , O, or S, but at least one X 3 is N-Ar 5 Preferably, O or N-Ar 5 More preferably, N-Ar 5 Represents. N-Ar 5 or Ar 5 is N-Ar of general formula (2) 3 or Ar 3 I agree with this. R 61each independently represents 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. Preferably, it is a diarylamino group 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 preferably, it is a diarylamino group having 12 to 24 carbon atoms, 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. g and h each independently represent an integer of 0 to 4, i and j each independently represent an integer of 0 to 3, and k represents an integer of 0 to 2. Preferably, g and h each independently represent an integer of 0 to 2, i and j each independently represent 0 or 1, and k is 0.

[0076] Ar 5 and R 61 Specific examples of the Ar 3 and R 6 This can be understood from the explanation. In addition, N-Ar 5 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.

[0077] The partial structure type polycyclic aromatic compound will be explained below with reference to formula (3) and formula (4). Formula (3) consists of the structure represented by general formula (2) and a partial structure thereof. From another perspective, there are two structures represented by general formula (2), but they share the I ring. In other words, the structure represented by general formula (2) is a partial structure. Similarly, formula (4) 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 (2) 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 (2) as a partial structure. A compound having a structure in which any one of rings C to E in general formula (2) is missing as another partial structure is suitable. A compound having one structure represented by general formula (2) as a partial structure and 1 to 3 of the other partial structures is preferred.

[0078] Examples of such partial structure polycyclic aromatic compounds include compounds represented by the following formulae (2-a) to (2-h). The compound represented by the following formula (2-a) corresponds to, for example, a compound represented by the formula (2-64) described below. Formula (2-a) has a structure in which a central benzene ring is shared by two compounds of general formula (2), and it is understood that this is a compound that contains a structural unit of general formula (2) and one partial structure thereof. Formula (2-b) has a structure in which the central benzene ring is shared by two compounds of general formula (2), but it is understood that it is a compound that contains the structural unit of general formula (2) and one partial structure thereof. 1 One of them is N-Ar 3 This is then bonded to another aromatic ring to form a ring (fused ring structure).

[0079] [ka]

[0080] Furthermore, the partial structure type polycyclic aromatic compound represented by the above formula (2-c) corresponds to, for example, a compound represented by formula (2-66) described later. That is, in terms of general formula (2), it has a structure having three unit structures represented by general formula (2) so as to share the benzene ring, which is the E ring. That is, it is understood that it is a compound having the unit structure represented by general formula (2) as a partial structure, and also containing two partial structures which are structures obtained by removing one benzene ring from general formula (2). Also, X 1 N-Ar 3 This is bonded to the other aromatic ring to form a ring.

[0081] Furthermore, the partial structure type polycyclic aromatic compounds represented by the above formula (2-d) and the following formulas (2-e), (2-f), and (2-g) correspond to compounds such as those represented by the formulas (2-67), (2-68), (2-69), and (2-70) described below. In terms of general formula (2), it is a compound having two or three unit structures represented by general formula (2) 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 (2) as a partial structure, and including one partial structure that is a structure obtained by removing one benzene ring from general formula (2).

[0082] [ka]

[0083] The partial structure type polycyclic aromatic compound represented by the above formula (2-h) corresponds to compounds represented by the formulas (2-71), (2-72), (2-73), (2-74), and (2-75) described below. To explain it in terms of general formula (2), for example, it is a compound in which the C ring is a naphthalene ring and two unit structures represented by general formula (2) are contained in one compound so as to share the ring. In other words, it is understood to be a compound that has the unit structure represented by general formula (2) as a partial structure and also contains one or two partial structures that are structures in which one C ring (naphthalene ring) is removed from general formula (2).

[0084] The partial structure type polycyclic aromatic compound of the present invention has a structure in which a plurality of compounds of general formula (2) are linked together by sharing one or two aromatic rings (ring C to ring E) in the structural unit of general formula (2), and can be said to contain at least one structural unit of general formula (2). The number of compounds of general formula (2) 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.

[0085] In the above formula, X 1 and Y 1 is the same as general formula (2). 7 is R in Eq. (4). 61 However, a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms is preferred. Each 1 is independently an integer of 0 to 4, each m is independently an integer of 0 to 1, each n is independently an integer of 0 to 3, and each o is independently an integer of 0 to 2. Preferably, 1 and n are 0 to 2. o is preferably 0 to 1.

[0086] Specific examples of polycyclic aromatic compounds represented by general formula (2), general formula (3), or formula (4) and other partial structure polycyclic aromatic compounds are shown below, but are not limited to these exemplary compounds.

[0087] [ka] [ka] [ka]

[0088] [ka] [ka] [ka]

[0089] [ka] [ka] [ka]

[0090] [ka] [ka] [ka]

[0091] [ka] [ka] [ka]

[0092] [ka] [ka] [ka]

[0093] 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 or less, more preferably 0.15 eV or less, and particularly preferably 0.10 eV or less.

[0094] ΔEST represents the difference between the excited singlet energy (S1) and the excited triplet energy (T1), where S1 and T1 are measured by the method described in the Examples.

[0095] An excellent organic EL device can be provided by using a material selected from the compounds represented by the general formula (2), (3) or (4) or polycyclic aromatic compounds having the structure represented by the general formula (2) as a partial structure as a light-emitting dopant, and a material selected from the compounds represented by the general formula (1), (5), (6), (7) or (8) as a host.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] -substrate- The organic EL device of the present invention is preferably supported on a substrate. There are no particular limitations on the substrate, and any substrate conventionally used in organic EL devices, such as glass, transparent plastic, or quartz, can be used.

[0100] -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.

[0101] -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 by methods such as vapor deposition or sputtering. Furthermore, the cathode preferably has a sheet resistance of several hundred Ω / □ or less, and the film thickness is typically selected 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.

[0102] 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.

[0103] -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 in a ratio of, for example, 0.10 to 10% (mass %) of the light-emitting dopant to 99.9 to 90% of the host, 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.

[0104] As the host in the light-emitting layer, two or more types of hosts represented by general formula (1) can be used. The first host and second host can be used, for example, in a ratio of 10 to 90% of the first host and 90 to 10% of the second host. Preferably, the ratio is 30 to 70% of the first host and 70 to 30% of the second host, and more preferably, 40 to 60% of the first host and 60 to 40% of the 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 by weight, based on the total amount of the host materials.

[0105] 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 0.010 eV or more higher than that of the luminescent dopant, more preferably 0.030 eV or more higher, and even more preferably 0.10 eV or more higher. A TADF-active compound may also be used as the host material, and a compound having the above ΔEST of 0.20 eV or less is preferred.

[0106] The other hosts can be selected from among those known in numerous patent documents, etc. Specific examples of the host include, but are not limited to, indole derivatives, carbazole 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, polyfluorene derivatives, and other polymer compounds.

[0107] 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.

[0108] 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.

[0109] The light-emitting dopant in the light-emitting layer is a polycyclic aromatic compound represented by the above general formula (2), or a polycyclic aromatic compound having the structure represented by general formula (2) as a partial structure (partial structure polycyclic aromatic compound). The polycyclic aromatic compound having the structure represented by general formula (2) as a partial structure is preferably a partial structure polycyclic aromatic compound represented by the above general formula (3), and more preferably a boron-containing partial structure polycyclic aromatic compound represented by the above formula (4). The light-emitting dopant is preferably a compound having a difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of 0.20 eV or less.

[0110] The light-emitting layer may contain one or more types of light-emitting dopant. The content of the light-emitting dopant is preferably 0.050 to 50%, more preferably 0.10 to 40%, based on the host material.

[0111] When the light-emitting layer contains two or more light-emitting dopants, the first dopant is a compound represented by general formula (2), (3), or (4), or the above-mentioned partial structure polycyclic aromatic compound, and the second dopant may be a known compound used in combination as a light-emitting dopant. The content of the first dopant is preferably 0.050 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.

[0112] 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.

[0113] The 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, so that the luminescent dopant and the first host or the second host can be simultaneously deposited from a single deposition source.

[0114] -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.

[0115] -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 low ability to transport holes. By transporting electrons while blocking holes, the hole-blocking layer can improve the probability of electron and hole recombination in the light-emitting layer. Known hole-blocking materials can be used for the hole-blocking layer. To bring out the properties of the light-emitting dopant, the material used as the host can also be used as the material for the hole-blocking layer. Multiple hole-blocking materials may also be used in combination.

[0116] -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 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.

[0117] -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.

[0118] 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.

[0119] -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.

[0120] 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.

[0121] -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.

[0122] The electron transport material (which may also serve as a hole blocking material) may be any material capable 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 incorporating these materials into polymer chains or containing these materials as the polymer backbone may also be used.

[0123] 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]

[0124] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. The following Examples 10 and 24 are for reference only.

[0125] The compounds used in the examples and comparative examples are listed below. [ka]

[0126] The S1 and T1 of the compounds (2-2) and (4-2) were measured. S1 and T1 were measured as follows. Vacuum deposition method on a quartz substrate at a vacuum level of 10 -4A 100-nm-thick deposited film was formed by co-evaporation from different evaporation sources using BH1 as the host and compound (2-2) or (4-2) as the luminescent dopant under conditions of 0.01 Pa or less, with the concentration of compound (2-2) or (4-2) being 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)

[0127] 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)

[0128] The measurement results are shown in Table 1. [Table 1]

[0129] 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 on ITO as a hole transport layer to a thickness of 25 nm. Next, compound (1-148) was formed on ITO as an electron blocking layer to a thickness of 5 nm. Next, compound (1-148) was formed on ITO as a first host, compound (1-331) was formed on ITO as a second host, and compound (4-2) was formed on ITO as a light-emitting dopant to a thickness of 30 nm by co-evaporation from different evaporation sources. The co-evaporation conditions were a concentration of compound (4-2) of 2% and a weight ratio of the first host to the second host of 50:50. Next, compound (1-331) was formed on ITO as a hole blocking layer to a thickness of 5 nm. Next, ET-1 was formed on ITO as an electron transport layer to a thickness of 40 nm. Furthermore, lithium fluoride (LiF) was formed on the electron transport layer to a thickness of 1 nm as an electron injection 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.

[0130] Examples 2 to 19 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 as shown in Table 2.

[0131] Examples 20 to 25 Organic EL devices were prepared in the same manner as in Example 1, except that the light-emitting dopant and the first host or second host were compounds shown in Table 2.

[0132] 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 mCBP was formed as an electron-blocking layer to a thickness of 5 nm. Next, compound mCBP was co-deposited as a first host and compound (4-2) as an emissive dopant from separate evaporation sources to form an emissive layer to a thickness of 30 nm. The co-deposition was performed under evaporation conditions that resulted in a 2% concentration of compound (4-2). Next, compound (1-331) 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.

[0133] Comparative Example 2 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.

[0134] [Table 2]

[0135] 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.

[0136] [Table 3]

[0137] It can be seen from Table 3 that the organic EL device according to the embodiment of the present invention has the characteristics of low voltage, high efficiency, and long life, and emits blue light from the maximum emission wavelength. [Explanation of symbols]

[0138] 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 light-emitting layers between an anode and a cathode facing each other, wherein at least one of the light-emitting layers contains one or more hosts selected from compounds represented by the following general formula (1), and contains, as a light-emitting dopant, a boron-containing polycyclic aromatic compound of the following formula (4) having a structure represented by the following general formula (2) as a partial structure: 【Chemical 1】 wherein Z is an indolocarbazole ring-containing group represented by formula (1a): * is L １ is the bonding position with Ring A is a heterocycle represented by formula (1b), and ring A is fused to the adjacent ring at any position. L １ and L ２ each independently represents 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 １ and Ar ２ 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 １ are each 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. a represents an integer of 1 to 3; b represents an integer of 0 to 3; c and d each independently represent an integer of 0 to 4; e represents an integer of 0 to 2; and f represents an integer of 0 to 3. 【Chemistry 2】 wherein ring C, ring D, and ring E are each independently an aromatic hydrocarbon ring having 6 to 24 carbon atoms or an aromatic heterocycle having 3 to 17 carbon atoms; Y １ is B, P, P=O, P=S, Al, Ga, As, Si-R ２ or Ge-R ３ and R ２ and R ３ 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, X １ are each independently O, N-Ar ３ , S or Se, Ar ３ 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, and N-Ar ３ may be bonded to any of ring C, ring D, or ring E to form a heterocycle containing N, C ring, D ring, E ring, R ２ , R ３ , R ６ and Ar ３ At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom. R ６ 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; 【Chemistry 3】 Here, X 3 represents N—Ar 5 . Each Ar 5 independently represents a substituted or unsubstituted phenyl group. Each R 61 independently represents 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. g and h each independently represent an integer of 0 to 4; i and j each independently represent an integer of 0 to 3; k represents an integer of 0 to 2;

2. 2. The organic electroluminescent device according to claim 1, wherein the light-emitting layer contains two or more hosts selected from the compounds represented by formula (1).

3. At least one of the hosts selected from the compounds represented by the general formula (1) is L １ and L ２ 3. The organic electroluminescent device according to claim 2, wherein only one of the above is a substituted or unsubstituted nitrogen-containing aromatic heterocyclic group having 3 to 17 carbon atoms.

4. 4. The organic electroluminescent device according to claim 3, wherein the host selected from the compounds represented by the general formula (1) includes a first host represented by the following formula (5a) or (5b) and a second host represented by the following formula (6): 【Chemistry 4】 Here, Z, Ar １ , a and b have the same meanings as in general formula (1). X ４ represents O or S. b1 represents an integer of 0 to 2. X ５ are each independently N, C—H, C—, or C—R ７ and at least one X ５ represents N. R ７ each independently represents a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms.

5. 4. The organic electroluminescent device according to claim 3, wherein at least one host selected from the compounds represented by the general formula (1) is a compound represented by the following formula (7) or (8): 【Chemistry 5】 Here, L １ , L ２ , Ar １ , Ar ２ , b and f have the same meanings as in the general formula (1).

6. 6. The organic electroluminescent device according to claim 5, wherein at least two of the hosts selected from the compounds represented by the general formula (1) are represented by the formula (7).

7. 7. The organic electroluminescent device according to claim 1, wherein the difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of the luminescent dopant is 0.20 eV or less.

8. 8. The organic electroluminescent device according to claim 7, wherein the ΔEST is 0.10 eV or less.

9. 9. The organic electroluminescent device according to claim 4, 7, or 8, wherein the host is contained in an amount of 99.9 to 90 mass % relative to 0.10 to 10 mass % of the luminescent dopant, and the host contains 10 to 90 mass % of a first host represented by formula (5) and 90 to 10 mass % of a second host represented by formula (6).

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