Organic electroluminescent device

Abstract

Provided is a blue light-emitting organic EL device with high emission efficiency and a long life. This organic EL device is provided with one or more luminescent layers between a positive electrode and a negative electrode which face each other, and is characterized in that at least one luminescent layer contains a first host which is selected from indolocarbazole compounds, a second host which is selected from compounds represented by general formula (2), and, as a luminescent dopant, a polycyclic aromatic compound which is represented by general formula (3) or a polycyclic aromatic compound which has, as a partial structure, a structure represented by general formula (3). Here, Y4 is B, P, P=O, P=S, Al, Ga, As, Si-R4 or Ge-R5, and X4 is O, N-Ar4, S or Se.

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] 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.

[0004] Meanwhile, 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 be able to increase the internal quantum efficiency to 100%. However, as with phosphorescent devices, further improvements in lifetime characteristics are required.

[0005] Patent Documents 3 and 4 disclose organic EL devices that use, as a light-emitting dopant, a TADF material made of a polycyclic aromatic compound, such as the compound shown below, but do not specifically disclose the life characteristics. [ka] [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2010 / 134350 publication [Patent Document 2] WO2011 / 070963 publication [Patent Document 3] WO2015 / 102118 publication [Patent Document 4] WO2018 / 212169 publication Summary of the Invention

[0007] 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 has high efficiency and long life characteristics while requiring a low driving voltage.

[0008] 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, as a light-emitting dopant, a first host selected from compounds represented by the following general formula (1), a second host selected from compounds represented by the following general formula (2), and a polycyclic aromatic compound represented by the following general formula (3) or a polycyclic aromatic compound having a structure represented by the general formula (3) as a partial structure:

[0009] [ka] Here, Z is an indolocarbazole ring-containing group represented by general formula (1a), * is L 1 This is the bonding position with Ring A is a heterocycle represented by formula (1b), and this heterocycle is fused to the adjacent ring at any position. 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. 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.

[0010] [ka] where X 1 Each independently represents N or CH, provided that at least one X 1 represents N. Preferably, three X 1 is N. Ar 3 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.

[0011] [ka] Here, ring C, ring D, and ring E are each independently 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. Y 4 is B, P, P=O, P=S, Al, Ga, As, Si―R 4 or Ge-R 5 and R 4 and R 5 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. X 4 are independently O, N-Ar 4 , S or Se, and 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, and N-Ar 4 may be bonded to any of ring C, ring D, or ring E to form a heterocycle containing N. R 3 each independently represents 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. C ring, D ring, E ring, R 3 , R 4 , R 5 , and Ar 4 At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom. 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 (3) as a partial structure include polycyclic aromatic compounds represented by the following general formula (4) and boron-containing polycyclic aromatic compounds represented by the following formula (5).

[0013] [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 heterocyclic ring having 3 to 17 carbon atoms; 4 , Y 4 , R 3 , x, and v have the same meaning as in formula (3), 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. At least one hydrogen atom in rings F, G, H, I, and J may be substituted with halogen or deuterium.

[0014] [ka] where X 9 are each independently N-Ar 6 , O, or S, but at least one X 9 is N-Ar 6 Represents Ar 6 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. 6 may be bonded to the aromatic ring to form a heterocyclic ring containing N. R 9 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. m and n each independently represent an integer of 0 to 4; o and p each independently represent an integer of 0 to 3; q represents an integer of 0 to 2;

[0015] Preferred embodiments of the general formula (2) include the following formula (6) or formula (7). [ka] where Ar 3 and X 1 is the same as general formula (2). R 2 each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group, 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, h, i and j each independently represent an integer of 0 to 4.

[0016] A preferred embodiment of the general formula (1) is the following formula (8a) or formula (8b). [ka] [ka] where L 3 , L 4 , Ar 4 , Ar 5 , k and l are L in general formula (1), 1 , L 2 , Ar 1 , Ar 2 , a and b.

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

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

[0019] 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.

[0020] The organic EL device of the present invention contains a specific luminescent dopant and a plurality of specific host materials in the light-emitting layer, and therefore can be an organic EL device with high luminous efficiency and long life at a low driving voltage. The organic EL device of the present invention exhibits a low driving voltage because the indolocarbazole compound, which is the first host material, has a property of easily injecting holes, and the nitrogen-containing six-membered ring compound, which is the second host material, has a property of easily injecting electrons, thereby allowing holes and electrons to be injected and excitons to be generated at a lower voltage. The organic EL device of the present invention exhibits high luminous efficiency because the indolocarbazole compound has a property of easily injecting holes, and the nitrogen-containing six-membered ring compound has a property of easily injecting electrons, thereby maintaining a balance between holes and electrons in the emissive layer. The organic EL device of the present invention exhibits a long life because, when a voltage is applied to the organic EL device, holes are preferentially injected into the first host, which is made of the indolocarbazole compound, and electrons are preferentially injected into the second host, which is made of the nitrogen-containing six-membered ring compound, thereby reducing the electrochemical load on the luminescent dopant. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an organic EL element. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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, as a luminescent dopant, a first host selected from the compounds represented by the above general formula (1), a second host selected from the compounds represented by the above general formula (2), and a polycyclic aromatic compound represented by the above general formula (3) or a polycyclic aromatic compound having the structure represented by the general formula (3) as a partial structure.

[0023] The compound represented by the general formula (1) used as the first host in the present invention will be explained below. In general formula (1), Z is an indolocarbazole ring-containing formula represented by general formula (1a), and ring A is a heterocycle represented by formula (1b), which is fused to the adjacent ring at any position. 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. Preferably, a is 1 to 2, b is 0 to 2, c and d are 0 to 1, e is 0 to 2, and f is 0 to 2.

[0024] A preferred embodiment of general formula (1) is the above formula (8a) or formula (8b), with formula (8b) being more preferred.

[0025] In the general formula (1), the formula (8a) and the formula (8b), the common symbols have the same meaning. k and l each represent an integer of 0 to 3. More preferably, k and l each represent an integer of 0 to 2.

[0026] L 1 , L 2 , L 3 and L 4each 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. An aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 3 to 15 carbon atoms is preferred. A phenyl group, a naphthyl group, a pyridine group, a triazine group, a dibenzofuran group, or a carbazole group is more preferred. 1 , L 2 , L 3 and L 4 are a+b, f+1, k+1 and l+1 valent groups, respectively.

[0027] Specific examples of the unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms or the substituted or 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, tetracene, pentacene, hexacene, coronene, heptacene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, Examples include groups derived from thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole.

[0028] Ar 1 , Ar 2 , Ar 4 and Ar 5are 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. A substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 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 is preferred. A phenyl group, a biphenyl group, or a terphenyl group is more preferred.

[0029] Ar 1 , Ar 2 , Ar 4 and Ar 5 Specific examples of the unsubstituted aromatic hydrocarbon group and the unsubstituted aromatic heterocyclic group include 1 This is the same as in the case of (the valence may differ; the same applies below). Preferred examples include groups derived by removing one hydrogen from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, pyridine, triazine, dibenzofuran, dibenzothiophene, carbazole, or a compound formed by linking 2 to 4 of these rings together. More preferred examples include groups derived from benzene or a compound formed by linking 2 to 3 benzene rings together.

[0030] 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. When a group corresponds to a linked aromatic group, it is different from a substituted aromatic hydrocarbon group or aromatic heterocyclic group.

[0031] 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.

[0032] 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.

[0033] 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 iso Examples of groups include groups formed by removing one hydrogen atom from oxazole, 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, 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 are 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, or carbazole.

[0034] In this specification, these aromatic hydrocarbon groups, aromatic heterocyclic groups, and linking aromatic groups may each have a substituent. When substituted, 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.

[0035] 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.

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

[0038] [ka] [ka] [ka]

[0039] [ka] [ka] [ka]

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

[0041] [ka] [ka] [ka]

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

[0043] The compound represented by the general formula (2) used as the second host in the present invention will be explained below.

[0044] In general formula (2), X 1 independently represent N or CH, but at least one X 1 represents N. Preferably, two X 1 represents N. Preferably, three X 1 is a triazine compound in which

[0045] Preferred embodiments of general formula (2) include the above formula (6) or formula (7), with formula (7) being more preferred. In general formula (2), formula (6) and formula (7), common symbols have the same meaning. g, h, i and j each represent an integer of 0 to 4. More preferably, g, h, i and j are 0 to 2.

[0046] Ar 3represents 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 2 to 8 of these aromatic rings being linked together. Preferably, it represents 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 2 to 6 of these aromatic rings being linked together. More preferably, it represents 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 2 to 4 of these aromatic rings being linked together.

[0047] Ar 3 Specific examples of the unsubstituted aromatic hydrocarbon group or unsubstituted aromatic heterocyclic group include the above Ar 1 or R 1 The unsubstituted linking aromatic group is the same as the above Ar 1 is the same as in these cases. Preferred examples include groups derived by removing one hydrogen from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, pyridine, triazine, dibenzofuran, dibenzothiophene, carbazole, or a compound formed by linking 2 to 4 of these rings together. More preferred examples include groups derived from benzene, carbazole, or a compound formed by linking 2 to 3 benzene rings together.

[0048] In equations (6) and (7), R 2 independently represent deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group, 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 an aromatic hydrocarbon group having 6 to 10 carbon atoms. g, h, i, and j represent integers of 0 to 4.

[0049] R 2Specific examples of when R 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 include 1 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, triphenylsilane, or carbazole.

[0050] Specific examples of the compounds represented by general formula (2), formula (6) or formula (7) are shown below, but the compounds are not limited to these exemplary compounds.

[0051] [ka] [ka] [ka]

[0052] [ka] [ka] [ka]

[0053] [ka] [ka] [ka]

[0054] [ka] [ka] [ka]

[0055] The light-emitting dopant used in the organic EL device of the present invention is a polycyclic aromatic compound represented by the general formula (3) or a polycyclic aromatic compound having a structure represented by the general formula (3) as a partial structure (also referred to as a partial structure type polycyclic aromatic compound). The partial structure polycyclic aromatic compound is preferably a partial structure polycyclic aromatic compound represented by the general formula (4), and more preferably a boron-containing partial structure polycyclic aromatic compound represented by the formula (5). Furthermore, the partial structure type polycyclic aromatic compound represented by the general formula (4) or (5) can be considered as a condensation product of the compound represented by the general formula (3) or an analogue thereof.

[0056] In general formula (3) and general formula (4), 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.

[0057] 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.

[0058] In general formula (3), Y 4 is B, P, P=O, P=S, Al, Ga, As, Si-R 4 or Ge-R 5 and preferably B, P, P═O or P═S, more preferably B.

[0059] R 4 and R 5 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.

[0060] R 4and R 5 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.

[0061] 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.

[0062] 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 groups. A phenyl group, a biphenyl group, or a terphenyl group is preferred.

[0063] 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 The same applies to these groups, except that the number of carbon atoms in the aromatic hydrocarbon group is different.

[0064] 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.

[0065] R 3represent 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.

[0066] R 3When 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.

[0067] 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.

[0068] The partial structure type polycyclic aromatic compounds include compounds represented by the above general formula (4) or formula (5). In general formula (3), general formula (4) and formula (5), common symbols have the same meaning. 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. In formula (5), m and n represent integers of 0 to 4, o and p represent integers of 0 to 3, and q represents an integer of 0 to 2. Preferably, w, y, z, m, and n are independently 0 or 1.

[0069] In the general formula (4), 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 (3), 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.

[0070] In equation (5), X 9 are independently N-Ar 6 , O, or S, but at least one X 9 is N-Ar 6 Represents Ar 6 is Ar in general formula (3) 4 This is the same as N-Ar. 6 may be bonded to the aromatic ring to form a heterocyclic ring containing N.

[0071] R 9 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 3 is the same as in these cases.

[0072] The partial structure type polycyclic aromatic compound will be explained below with reference to general formula (4) and formula (5). General formula (4) consists of the structure represented by general formula (3) and a partial structure thereof. From another perspective, there are two structures represented by general formula (3), but they share the I ring. In other words, the structure represented by general formula (3) is a partial structure. Similarly, formula (5) 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 (3) 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 (3) as a partial structure. A compound having a structure in which any one of rings C to E in general formula (3) is missing as another partial structure is suitable. A compound having one structure represented by general formula (3) as a partial structure and 1 to 3 of the other partial structures is preferred. The bond between the structure represented by general formula (3) 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.

[0073] Preferred embodiments of the above general formula (3), general formula (4) or formula (5), or partial structure type polycyclic aromatic compounds include the following formulae (4-a) to (4-h). [ka]

[0074] The partial structure type polycyclic aromatic compound represented by the above formula (4-a) corresponds to, for example, a compound represented by the below-mentioned formula (3-64). That is, formula (4-a) has a structure in which two structures of general formula (3) are shared by a central benzene ring, but it is understood to be a compound containing a structural unit of general formula (3) and one partial structure thereof.

[0075] The partial structure type polycyclic aromatic compound represented by formula (4-b) corresponds to a compound represented by formula (3-65) described later, for example. That is, formula (4-b) has a structure in which two structures of general formula (3) are shared by the central benzene ring, but it is understood to be a compound containing a structural unit of general formula (3) and one partial structure thereof. Explained in terms of general formula (3), X 4 One of them is N-Ar 4 This is then bonded to another aromatic ring to form a ring (fused ring structure).

[0076] The partial structure type polycyclic aromatic compound represented by formula (4-c) corresponds to, for example, a compound represented by formula (3-66) described later. That is, in terms of general formula (3), it has a structure having three unit structures represented by general formula (3) 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 (3) as a partial structure, and also containing two partial structures which are structures obtained by removing one benzene ring from general formula (3). In addition, X 4 N-Ar 4 This is bonded to the other adjacent ring to form a ring.

[0077] [ka]

[0078] 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 (3-67), formula (3-68), formula (3-69), and formula (3-70) described later, for example. That is, it is a compound having two or three unit structures represented by general formula (3) 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 (3) as a partial structure, and including one partial structure that is a structure obtained by removing one benzene ring from general formula (3).

[0079] The partial structure polycyclic aromatic compound represented by formula (4-h) corresponds to, for example, compounds represented by formulas (3-71), (3-72), (3-73), (3-74), and (3-75) described below. That is, in terms of general formula (3), the C ring is a naphthalene ring, and the partial structure polycyclic aromatic compound has two unit structures represented by general formula (3) in one compound, sharing the ring. That is, it is understood to be a compound having the unit structure represented by general formula (3) as a partial structure, and containing one or two partial structures that are the structure of general formula (3) minus one C ring (naphthalene ring).

[0080] In formulas (4-a) to (4-h), X 4 and Y 4 is the same as general formula (3), and R 6 , k, l, and m are R in Eq. (5). 9 , m, o, and q. s is 0 to 1, and is preferably 0.

[0081] 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.

[0082] Specific examples of polycyclic aromatic compounds and partial structure type polycyclic aromatic compounds represented by general formula (3), general formula (4), or formula (5) are shown below, but the compounds are not limited to these exemplary compounds.

[0083] [ka] [ka] [ka]

[0084] [ka] [ka] [ka]

[0085] [ka] [ka] [ka]

[0086] [ka] [ka] [ka]

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

[0088] The organic light-emitting material used as a light-emitting dopant in the organic EL device of the present invention may have a ΔEST of 0.20 eV or less, preferably 0.15 eV or less, and more preferably 0.10 eV or less.

[0089] 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.

[0090] 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) as a first host, and a material selected from the compounds represented by the general formula (2) as a second host.

[0091] In another embodiment of the present invention, a compound having a ΔEST of 0.20 eV or less is used as the luminescent dopant. In this case, the compound as the luminescent dopant does not need to be the polycyclic aromatic compound material described above, but may be a 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] -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.

[0096] -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. These electrode materials may be formed into thin films by methods such as vapor deposition or sputtering, and then patterned into the desired shape by photolithography. Alternatively, if pattern precision is not required (approximately 100 μm or higher), a mask of the desired shape may be used during vapor deposition or sputtering of the electrode material to form the pattern. 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.

[0097] -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.

[0098] 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.

[0099] -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.

[0100] The hosts in the light-emitting layer are the first host and the second host described above. The first host and the 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 of the total amount of the host material. Other known hosts that can be used are compounds that have hole transporting ability, electron transporting ability, and a high glass transition temperature, and preferably have a T1 greater than that of the luminescent dopant.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] When the light-emitting layer contains two or more types of light-emitting dopants, the first dopant is a compound represented by general formula (2), (3), or (4), or a partial structure-type polycyclic aromatic compound having the structure represented by general formula (2) as a partial structure, 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% relative to the host material, and the content of the second dopant is preferably 0.050 to 50% relative to the host material, and the total content of the first dopant and the second dopant does not exceed 50% relative to the host material.

[0108] Such other luminescent dopants are known in many patent documents, etc., and can be selected from them. 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, benzophenone ... 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.

[0109] The luminescent dopant and the first host or the second host can be deposited from different deposition sources, or 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.

[0110] -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.

[0111] -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-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 second host can also be used as the material for the hole-blocking layer. Multiple hole-blocking materials may also be used in combination.

[0112] -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.

[0113] -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.

[0114] 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.

[0115] -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.

[0116] 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.

[0117] -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.

[0118] 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.

[0119] 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]

[0120] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0121] The compounds used in the examples and comparative examples are listed below. [ka]

[0122] The S1 and T1 of the compounds (3-2) and (5-2) were measured, and the results are shown in Table 1.

[0123] S1 and T1 were measured as follows. Vacuum deposition method on a quartz substrate at a vacuum level of 10 -4A 100-nm-thick film was formed by co-evaporating BH1 as a host and compound (3-2) or (5-2) as an emitting dopant from different evaporation sources under conditions of 0.01 Pa or less, with the concentration of compound (3-2) or (5-2) 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)

[0124] 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)

[0125] The measurement results are shown in Table 1. [Table 1]

[0126] 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 as a hole injection layer on ITO 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 (1-56) was formed as an electron blocking layer to a thickness of 5 nm. Next, compound (1-56) was used as the first host, compound (2-6) was used as the second host, and compound (5-2) was used as the luminescent dopant, and these were co-deposited from different evaporation sources to form an emitting layer to a thickness of 30 nm. The co-deposition conditions were such that the concentration of compound (5-2) was 2% and the mass ratio of the first host to the second host was 70:30. Next, compound (2-6) 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.

[0127] Examples 2 to 11 An organic EL device was produced in the same manner as in Example 1, except that the types of the luminescent dopant, first host, and second host, and the mass ratio of the first host to the second host were as shown in Table 2.

[0128] 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 on the ITO as a hole-injection layer to a thickness of 10 nm, followed by HT-1 as a hole-transport layer to a thickness of 25 nm. Next, compound (1-56) was formed as an electron-blocking layer to a thickness of 5 nm. Next, compound (1-56) was co-deposited from separate evaporation sources as the first host and compound (5-2) as the luminescent dopant to form an emitting layer to a thickness of 30 nm. The co-deposition was carried out under evaporation conditions that resulted in a 2% concentration of compound (5-2). Next, compound (2-6) 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, thereby completing the fabrication of an organic EL device.

[0129] Comparative Examples 2, 3, 5, 6, and 7 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.

[0130] Comparative Examples 4 and 8 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.

[0131] [Table 2]

[0132] 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.

[0133] [Table 3]

[0134] From Table 3, it can be seen that the organic EL devices of the examples have the characteristics of low voltage, high efficiency, and long life, and emit blue light based on the maximum emission wavelength. [Explanation of symbols]

[0135] 1 substrate, 2 anode, 3 hole injection layer, 4 hole transport layer, 5 light-emitting layer, 6 electron transport layer, 7 cathode

Claims

1. The organic electroluminescent device includes one or more emitting layers between an anode and a cathode facing each other, wherein at least one emitting layer contains a first host selected from compounds represented by the following general formula (1), a second host selected from compounds represented by the following general formula (2), and a luminescent dopant which is a polycyclic aromatic compound represented by the following general formula (3) or a polycyclic aromatic compound having a structure represented by the following general formula (3) as a partial structure, and which has a difference (ΔEST) between excited singlet energy (S1) and excited triplet energy (T1) of 0.20 eV or less: 【Chemical 1】 Here, Z is an indolocarbazole ring-containing group represented by general 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】 Here, X １ Each independently represents N or CH, provided that at least one X １ represents N. Ar ３ 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. 【Chemistry 3】 wherein ring C, ring D, and ring E are each independently a substituted or unsubstituted benzene ring; ４ is B and X ４ are each independently N-Ar ４ and Ar ４ are each independently a substituted or unsubstituted phenyl group, biphenyl group, or dibenzofuranyl group, and N-Ar ４ may be bonded to any of ring C, ring D, or ring E to form a heterocycle containing N, R ３ 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, C ring, D ring, E ring, R ３ , and Ar ４ At least one hydrogen atom in the formula (I) may be substituted with a halogen atom or deuterium atom. Each v independently represents an integer of 0 to 4; x represents an integer of 0 to 3;

2. 2. The organic electroluminescent device according to claim 1, wherein the polycyclic aromatic compound having the structure represented by the general formula (3) as a partial structure is a polycyclic aromatic compound represented by the following general formula (4): 【Chemistry 4】 wherein ring F, ring G, ring H, ring I, and ring J are each independently a substituted or unsubstituted benzene ring; ４ , Y ４ , R ３ , x, and v have the same meaning as in formula (3), 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. At least one hydrogen atom in rings F, G, H, I, and J may be substituted with halogen or deuterium.

3. 3. The organic electroluminescent device according to claim 1, wherein the polycyclic aromatic compound having the structure represented by the general formula (3) as a partial structure is a boron-containing polycyclic aromatic compound represented by the following formula (5): 【Chemistry 5】 Here, X ９ are each independently N-Ar ６ Represents. Ar ６ each independently represents a substituted or unsubstituted phenyl group, biphenyl group, or dibenzofuranyl group. ６ may be bonded to the aromatic ring to form a heterocyclic ring containing nitrogen. R ９ 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. m and n each independently represent an integer of 0 to 4; o and p each independently represent an integer of 0 to 3; and q represents an integer of 0 to 2.

4. 4. The organic electroluminescent device according to claim 1, wherein the general formula (2) is the following formula (6): 【Chemistry 6】 Here, Ar ３ and X １ is the same as general formula (2). R ２ each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group, 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;

5. 5. The organic electroluminescent device according to claim 1, wherein the general formula (2) is the following formula (7): 【Chemistry 7】 Here, Ar ３ and X 1 is the same as in general formula (2), and R ２ is the same as equation (6). g, h, i and j each independently represent an integer of 0 to 4;

6. X in the general formula (2) １ 6. The organic electroluminescent device according to claim 1, wherein all of are N.

7. 7. The organic electroluminescent device according to claim 1, wherein the general formula (1) is the following formula (8a) or formula (8b): 【Chemistry 8】 Here, L ３ , and L ４ 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 6 to 17 carbon atoms. Ar ４ , and Ar ５ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 6 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 8 of these. k and l each independently represent an integer of 0 to 3;

8. 8. The organic electroluminescent device according to claim 1, wherein the ΔEST is 0.10 eV or less.

9. 9. The organic electroluminescent device according to claim 1, comprising 0.10 to 10 mass % of a light-emitting dopant and 99.9 to 90 mass % of a host, wherein the host comprises 10 to 90 mass % of the first host and 90 to 10 mass % of the second host.

Images