Light-emitting material and organic electroluminescent element

Abstract

Provided are: a light-emitting material with which it is possible to obtain an organic EL element that emits light with high efficiency and has a long service life; and an organic EL element using the light-emitting material. Specifically disclosed are: a light-emitting material represented by general formula (1); and an organic EL element using the light-emitting material. Each A1 independently represents CR1, C, or N, and each R1 independently represents hydrogen or the like; wherein the number of N present in one six-membered ring including A1 is 2 or less. Ring E is a heterocyclic ring represented by formula (1a) and is condensed at an arbitrary position with an adjacent ring. A, b, c, and d are each 0 or 1, and a, b, c, and d are not all 0. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a light-emitting material and an organic electroluminescent element (referred to as an organic EL element) using the light-emitting material for a light-emitting layer.

[0002] By applying voltage to an organic EL (electroluminescence) element, holes are injected from the anode into the light-emitting layer, and electrons are injected from the cathode into the light-emitting layer. In addition, in the light-emitting layer, the injected holes recombine with electrons to generate excitons. At this time, according to the statistical law of electron spin, singlet excitons and triplet excitons are generated in a ratio of 1:3. Regarding fluorescent organic EL elements using light generated by singlet excitons, the limit of the internal quantum efficiency is considered to be 25%. On the other hand, it is known that phosphorescent organic EL elements using light generated by triplet excitons can increase the internal quantum efficiency to 100% when intersystem crossing is efficiently performed from singlet excitons.

[0003] In recent years, the technology of extending the life of phosphorescent organic EL elements has been developed and is being applied to displays of mobile phones, etc. However, as for blue organic EL elements, practical phosphorescent organic EL elements have not yet been developed, and there is a demand for the development of a blue organic EL element with high efficiency and long life.

[0004] Furthermore, a highly efficient delayed fluorescence type organic EL element utilizing delayed fluorescence is being developed recently. For example, Patent Document 1 discloses an organic EL element utilizing a triplet-triplet fusion (TTF) mechanism, which is one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon of generating singlet excitons by the collision of two triplet excitons, and is believed to theoretically increase the internal quantum efficiency to 40%. However, compared with phosphorescent organic EL elements, the efficiency is low, and therefore further efficiency improvement is required.

[0005] On the other hand, Patent Document 2 discloses an organic EL element that utilizes a thermally activated delayed fluorescence (TADF) mechanism. The TADF mechanism utilizes the following phenomenon: in a material with a small energy difference between a singlet energy level and a triplet energy level, reverse intersystem crossing from a triplet exciton to a singlet exciton occurs; it is believed that the internal quantum efficiency is theoretically increased to 100%. Specifically, Patent Document 2 discloses a thermally activated delayed fluorescence material comprising an indolecarbazole compound.

[0006] In addition, a material comprising a polycyclic aromatic compound containing an indolecarbazole skeleton condensed at a specific position and an organic EL element using the material are disclosed in Patent Documents 3, 4 and 5. However, an organic EL element using a material comprising a polycyclic aromatic compound containing a benzothiophene skeleton further condensed on an indolecarbazole skeleton condensed at a specific position as a light-emitting material is not disclosed.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: WO2010 / 134350

[0010] Patent Document 2: WO2011 / 070963

[0011] Patent Document 3: WO2019 / 111971

[0012] Patent Document 4: Japanese Patent Application Publication No. 2021-172592

[0013] Patent Document 5: WO2021 / 167045 Summary of the invention

[0014] Problems to be solved by the invention

[0015] In order to use an organic EL element as a display element or light source such as a flat panel display, it is necessary to improve the luminous efficiency of the element while fully ensuring the stability during driving. The present invention is completed in view of such a situation, and its purpose is to provide a luminescent material that can obtain an organic EL element that emits light with high efficiency and has high driving stability and is practically useful, and an organic EL element using the luminescent material.

[0016] [Technical means to solve the problem]

[0017] That is, the present invention is a light-emitting material represented by the following general formula (1).

[0018] [Chemistry 1]

[0019]

[0020] Here, A 1 CR 1 , C or N. In the general formula (1), A 1 The number of N present in one six-membered ring is 2 or less. 1Each of them is independently hydrogen, cyano, deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted 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 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or a substituted or unsubstituted linked aromatic group in which two to five of the above aromatic hydrocarbon groups and aromatic heterocyclic groups are linked.

[0021] Ring E is a heterocyclic ring represented by the formula (1a), and ring E is condensed with an adjacent ring at any position.

[0022] Among them, a, b, c, and d are 0 or 1 respectively, and a, b, c, and d are not all 0.

[0023] Preferably, any one of a=b=c=0 and d=1, a=c=d=0 and b=1, a=d=1 and b=c=0, or a=d=0 and b=c=1 is satisfied.

[0024] A preferred embodiment of the light-emitting material represented by the general formula (1) is any one of the following general formulas (2) to (21). 1 It has the same meaning as in the general formula (1).

[0025] [Chemistry 2-1]

[0026]

[0027] [Chemistry 2-2]

[0028]

[0029] [Chemistry 2-3]

[0030]

[0031] [Chemistry 2-4]

[0032]

[0033] In the general formulae (2) to (21), the luminescent material is preferably a luminescent material represented by any one of the general formulae (2) to (11), more preferably a luminescent material represented by any one of the general formulae (2) to (7), and even more preferably a luminescent material represented by the general formula (2). 1 Preferably, CR 1 Or the form represented by C.

[0034] In the luminescent material represented by any one of the general formulae (1) to (21), it is preferred that at least one or two R 1 is deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms. 1 It is a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms.

[0035] In the light-emitting material represented by any one of the general formulae (1) to (21), the difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) is preferably 0.40 eV or less.

[0036] In addition, the present invention is an organic electroluminescent element comprising one or more light-emitting layers between opposing anodes and cathodes, wherein at least one light-emitting layer contains a light-emitting material of any one of the general formulae (1) to (21).

[0037] The light-emitting layer may further contain a biscarbazole compound, a triscarbazole compound or an anthracene compound as a host material.

[0038] Effects of the Invention

[0039] According to the luminescent material of the present invention, an organic EL element that emits light with high efficiency and has high driving stability and is practically useful can be obtained. In addition, the luminescent material of the present invention shows a maximum wavelength in the blue, light blue or green spectral region. The luminescent material particularly shows a maximum wavelength in the range of 410nm to 550nm, preferably in the range of 430nm to 495nm. The photoluminescence quantum yield of the luminescent material of the present invention can be 40% or more. The use of the luminescent material of the present invention provides a device with higher efficiency. In addition, an organic EL element having a luminescent layer containing the luminescent material has high luminescence efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] [ Figure 1 ] is a cross-sectional schematic diagram showing a structural example of an organic EL element used in the present invention. DETAILED DESCRIPTION

[0041] The light-emitting material of the present invention is represented by any one of the general formulae (1) to (21). Preferably, it is a light-emitting material represented by any one of the general formulae (2) to (11), more preferably a light-emitting material represented by any one of the general formulae (2) to (7), and further preferably a light-emitting material represented by the general formula (2). The organic EL element of the present invention has one or more light-emitting layers between the opposing anode and cathode, and at least one of the light-emitting layers contains a compound represented by any one of the general formulae (1) to (21) as a light-emitting material. The organic EL element has a plurality of layers between the opposing anode and cathode, but at least one of the plurality of layers is a light-emitting layer, and the light-emitting layer may contain a host material as needed. The general formula (1) is explained below. Typically, the compounds represented by the general formulae (1) to (21) have a structure in which a benzothiophene skeleton is further condensed on an indolecarbazole skeleton condensed at a specific position, or a structure similar thereto.

[0042] In the general formula (1), A 1 CR 1 , N or carbon atoms. In the general formula (1), A 1 A in a six-membered ring 1 The number of N in is less than 2. 1 The six-membered ring of is sometimes condensed with the adjacent ring E. In such a case, A 1 Two of are carbon atoms, and they share the carbon atoms with ring E. Preferably, all A 1 By CR 1 Or C represents.

[0043] R 1Each of them is independently hydrogen, cyano, deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted 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 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or a substituted or unsubstituted linked aromatic group in which two to five of the above aromatic hydrocarbon groups and aromatic heterocyclic groups are linked. Preferred are hydrogen, cyano, deuterium, a substituted or unsubstituted diarylamino group having 12 to 24 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 24 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 24 carbon atoms, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group in which two to four of the above aromatic hydrocarbon groups and the above aromatic heterocyclic groups are linked. More preferably, it is hydrogen, a substituted or unsubstituted diarylamino group having 12 to 18 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 18 carbon atoms, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which two or three of the above aromatic hydrocarbon groups and aromatic heterocyclic groups are linked.

[0044] Preferably at least one R 1 is deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and more preferably at least two R 1 is deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms. 1 It is a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms.

[0045] As R 1Specific examples of unsubstituted diarylamino, unsubstituted arylheteroarylamino, unsubstituted diheteroarylamino or aliphatic hydrocarbon groups include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenanthrylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, bisdibenzofuranylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl. Preferred examples include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, bisdibenzofuranylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl. More preferred examples include diphenylamino, phenylbiphenylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, and butyl. When it represents an aliphatic hydrocarbon group, it may be linear, branched, or cyclic.

[0046] As R 1 Specific examples of unsubstituted aromatic hydrocarbon groups, aromatic heterocyclic groups, and aromatic groups linked thereto include: benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, Pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, 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, pyrone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, indolocarbazole, or a group formed by removing one hydrogen from a compound composed of two to five of these linked together. Preferred examples include: benzene, naphthalene, dihydroacenaphthene, acenaphthene, azulene, anthracene, Pyrene, phenanthrene, fluorene, benzo[a]anthracene, 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, pyrone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or a group formed by removing one hydrogen atom from a compound in which two to four of these are linked together. More preferably, there can be mentioned a group formed by removing one hydrogen atom 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, pyrone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or a compound in which two or three of these are linked together.

[0047] In the present specification, the aromatic hydrocarbon group, the aromatic heterocyclic group or the linked aromatic group may have a substituent, respectively. The same applies to the aryl group or heteroaryl group contained in the diarylamino group, the arylheteroarylamino group and the diheteroarylamino group.

[0048] When there is a substituent, the substituent is a cyano group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a diarylamino group having 12 to 30 carbon atoms, an arylheteroarylamino group having 12 to 30 carbon atoms, a diheteroarylamino group having 12 to 30 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 18 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, or an arylthio group having 6 to 18 carbon atoms. Here, when the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear, branched, or cyclic. In addition, when the diarylamino group, arylheteroarylamino group, diheteroarylamino group, aryloxy group, and arylthio group replace the aromatic hydrocarbon group, the aromatic heterocyclic group, the aromatic ring connected to the aromatic group, or the aryl or heteroaryl group contained in the diarylamino group, the arylheteroarylamino group, and the diheteroarylamino group, nitrogen and carbon, oxygen and carbon, or sulfur and carbon are bonded by a single bond. The number of substituents is preferably 0 to 5, and more preferably 0 to 2. When calculating the carbon number of an aromatic hydrocarbon group or an aromatic heterocyclic group having a substituent, the carbon number of the substituent is not included. However, it is preferred that the total carbon number including the carbon number of the substituent satisfies the above range.

[0049] Specific examples of the substituent include cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenanthrenylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, bisdibenzofuranylamino, methoxy, ethoxy, phenol, diphenyloxy, methylthio, ethylthio, thiophenol, or diphenylthio. Preferably, cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, bisdibenzofuranylamino, phenol, or thiophenol can be mentioned.

[0050] In this specification, a linked aromatic group refers to an aromatic group in which aromatic groups are linked by a single bond. It is an aromatic group in which two or more aromatic groups are linked, and these may be straight-chain 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. The aromatic group equivalent to the linked aromatic group is different from the substituted aromatic group.

[0051] In this specification, it is understood that hydrogen may be deuterium. That is, in the general formulas (1) to (21), R 1 Alternatively, a part or all of the H atoms in the substituent may be deuterium.

[0052] Ring E is independently a heterocyclic ring represented by formula (1a), and ring E is condensed with an adjacent ring at any position.

[0053] a, b, c, and d each independently represent 0 or 1, and a, b, c, and d are not all represented by 0. Preferably, any one of a=b=c=0 and d=1, a=c=d=0 and b=1, a=d=1 and b=c=0, or a=d=0 and b=c=1 is satisfied, and more preferably, a=b=c=0 and d=1 is satisfied.

[0054] Preferred forms of the general formula (1) include the general formulas (2) to (11). More preferred are the general formulas (2) to (7), and even more preferred is the general formula (2). In the general formula (1), the general formulas (2) to (7) correspond to structures in which a, b, and c are all 0, and d is 1, and the general formulas (8) to (11) correspond to structures in which a, c, and d are all 0, and b is 1. In addition, the general formulas (12) to (17) correspond to structures in which a and d are all 1, and b and c are all 0, and the general formulas (18) to (21) correspond to structures in which a and d are all 0, and b and c are all 1.

[0055] Specific examples of the light-emitting materials represented by general formulae (1) to (21) are shown below, but the materials are not limited to these exemplified compounds.

[0056] [Chemistry 3]

[0057]

[0058] [Chemistry 4]

[0059]

[0060] [Chemistry 5]

[0061]

[0062] [Chemistry 6]

[0063]

[0064] [Chemistry 7]

[0065]

[0066] [Chemistry 8]

[0067]

[0068] [Chemistry 9]

[0069]

[0070] By incorporating the light-emitting material represented by the general formula (1) to the general formula (21) in the light-emitting layer, an organic EL device that emits light with high efficiency and has high driving stability and is excellent in practical use can be obtained.

[0071] 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 thereto.

[0072] Figure 1 It is a cross-sectional view showing a structural example of a general organic EL element used in the present invention, 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents a light-emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. In the organic EL element of the present invention, an exciton blocking layer may be adjacent to the light-emitting layer, and an electron blocking layer may also be provided between the light-emitting layer and the hole injection layer. The exciton blocking layer may be inserted into either the cathode side or the anode side of the light-emitting layer, and may also be inserted into both sides at the same time. In the organic EL element of the present invention, an anode, a light-emitting layer, and a cathode are provided as necessary layers, but in addition to the necessary layers, a hole injection transport layer and an electron injection transport layer may also be provided, and a hole blocking layer may also be provided between the light-emitting layer and the electron injection transport layer. In addition, a hole injection transport layer refers to either or both of a hole injection layer and a hole transport layer, and an electron injection transport layer refers to either or both of an electron injection layer and an electron transport layer.

[0073] It can also be used with Figure 1 The opposite structure is that the cathode 7, the electron transport layer 6, the light-emitting layer 5, the hole transport layer 4, the hole injection layer 3, and the anode 2 are sequentially stacked on the substrate 1. In the above case, the layers can be added or omitted as needed. In addition, in the organic EL element as described above, in addition to the electrodes such as the anode or the cathode, the layers constituting the stacked structure on the substrate are sometimes collectively referred to as organic layers.

[0074] -Substrate-

[0075] The organic EL element of the present invention is preferably supported on a substrate. The substrate is not particularly limited as long as it is a substrate conventionally used for organic EL elements, and for example, a substrate made of glass, transparent plastic, quartz, etc. can be used.

[0076] -anode-

[0077] As the anode material in the organic EL element, a material containing a metal, alloy, electrically conductive compound or a mixture of these with a large work function (4 eV or more) can be preferably used. Specific examples of such electrode materials include: metals such as Au; conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO. In addition, amorphous materials such as IDIXO (In2O3-ZnO) that can be made into transparent conductive films can also be used. The anode can be formed into a thin film by methods such as evaporation or sputtering, and a pattern of the desired shape can be formed by photolithography. Or, when the pattern accuracy is not very required (about 100 μm or more), a mask of the desired shape can be used to form a pattern during the evaporation or sputtering of the electrode material. Alternatively, when using a coatable substance such as an organic conductive compound, a wet film forming method such as printing or coating can also be used. When light is taken out from the anode, the transmittance is preferably greater than 10%, and the sheet resistance of the anode is preferably less than several hundred Ω / Y. The film thickness also depends on the material, and is usually selected in the range of 10nm to 1000nm, preferably 10nm to 200nm.

[0078] -cathode-

[0079] On the other hand, as a cathode material, a material containing a metal (called an electron injecting metal) with a small work function (less than 4 eV), an alloy, an electrically conductive compound, or a mixture of these can be used. 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, rare earth metals, etc. Among these, in terms of electron injectability and durability to oxidation, etc., a mixture of an electron injecting metal and a second metal that is a metal with a larger work function value than the metal and stable, such as a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, a lithium / aluminum mixture, aluminum, etc. is suitable. The cathode can be made as follows: these cathode materials are formed into a thin film by a method such as evaporation or sputtering. In addition, as a cathode, the sheet resistance is preferably less than several hundred Ω / Υ, and the film thickness is usually selected in the range of 10nm to 5μm, preferably 50nm to 200nm. Furthermore, in order to transmit the emitted light, it is preferable that either the anode or cathode of the organic EL element is transparent or semi-transparent, because the emission brightness is improved.

[0080] In addition, after the metal is formed on the cathode with a film thickness of 1nm to 20nm, the conductive transparent material listed in the description of the anode is formed thereon, thereby making a transparent or translucent cathode. By applying the method, an element in which both the anode and the cathode are transparent can be made.

[0081] -Luminous layer-

[0082] The light-emitting layer is a layer that emits light after the holes and electrons injected from the anode and cathode are recombined to generate excitons. The light-emitting layer may use the light-emitting materials represented by general formula (1) to general formula (21) alone, or may use the light-emitting materials together with a host material. When the light-emitting material is used together with the host material, the light-emitting material is responsible for emitting light in the element.

[0083] The content of the light emitting material is preferably 0.1 wt% to 50 wt%, more preferably 0.1 wt% to 40 wt%, based on the content of the host material.

[0084] As the host material in the light-emitting layer, a known host material used in a phosphorescent light-emitting element or a fluorescent light-emitting element can be used. As a known host material that can be used, a compound having hole transport ability, electron transport ability and a high glass transition temperature is used, and preferably has a triplet excitation energy (T1) greater than the triplet excitation energy (T1) of the light-emitting material represented by the general formula (1). In addition, a TADF-active compound can also be used as the host material. In the above case, the compound is preferably a compound having a difference (ΔEST=S1-T1) between the singlet excitation energy (S1) and the triplet excitation energy (T1) of 0.20 eV or less.

[0085] Such a host material is known through a large number of patent documents, etc., and can be selected from these. Specific examples of host materials are not particularly limited, and include: indole compounds, carbazole compounds and polymers thereof, anthracene compounds, indole and carbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, triazole compounds, oxazole compounds, oxadiazole compounds, imidazole compounds, phenylenediamine compounds, arylamine compounds, anthracene compounds, fluorenone compounds, distilbenes, triphenylene compounds, carborane compounds, porphyrin compounds, phthalocyanine compounds, various metal complexes represented by metal complexes of 8-hydroxyquinoline compounds or metal phthalocyanines, benzoxazole or benzothiazole compounds; polymer compounds such as poly (N-vinyl carbazole) compounds, aniline copolymer compounds, thiophene oligomers, polythiophene compounds, polyphenylene compounds, polystyrene vinylene compounds, and polyfluorene compounds. Preferred examples include: carbazole compounds and polymers thereof, anthracene compounds, indolecarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, anthracene compounds, triphenylene compounds, carborane compounds, and porphyrin compounds. More preferred examples include: biscarbazole compounds, triscarbazole compounds, or anthracene compounds, which are polymers of carbazole compounds. In addition, hydrogen in the host material represented by the above compounds may be substituted with deuterium.

[0086] Specific examples of the biscarbazole compound are shown below, but the compound is not limited to these examples.

[0087] [Chemistry 10]

[0088]

[0089] [Chemistry 11]

[0090]

[0091] Specific examples of the anthracene compound are shown below, but the anthracene compound is not limited to these exemplified compounds.

[0092] [Chemistry 12]

[0093]

[0094] The subject in one light-emitting layer may be only one, or two or more subjects may be used. In the case of using two or more subjects, at least one is preferably an electron-transporting compound such as the described bicarbazole compound, tricarbazole compound or anthracene compound, and the other subjects are preferably hole-transporting compounds such as carbazole compounds or indolecarbazole compounds. In the case of using multiple subjects, each subject may be evaporated from different evaporation sources, or pre-mixed before evaporation to form a premix, thereby simultaneously evaporating multiple subjects from one evaporation source.

[0095] The luminescent material and the host material may be separately deposited from different deposition sources, or pre-mixed before deposition to form a pre-mixed mixture, thereby simultaneously depositing the luminescent material and the host material from one deposition source.

[0096] As a method for premixing, a method that can mix as uniformly as possible is desirable, and examples thereof include pulverization mixing, a method of heating and melting under reduced pressure or in an inert gas atmosphere such as nitrogen, and sublimation, but are not limited to these methods.

[0097] The main body and its premix can be in the form of powder, rod, or granule.

[0098] -Injection layer-

[0099] The so-called injection layer is a layer provided between the electrode and the organic layer in order to reduce the driving voltage or increase the luminous brightness. There are hole injection layer and electron injection layer, which can exist 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.

[0100] -Hole blocking layer-

[0101] The so-called hole blocking layer, in a broad sense, has the function of an electron transport layer, and includes a hole blocking material that has the function of transporting electrons and has a significantly lower ability to transport holes, and can increase the probability of recombination of electrons and holes in the light-emitting layer by transporting electrons and blocking holes. In the hole blocking layer, a known hole blocking material can be used. In addition, multiple hole blocking materials can also be used in combination.

[0102] -Electron blocking layer-

[0103] The electron blocking layer, in a broad sense, has the function of a hole transport layer, and can increase the probability of electrons and holes recombination in the light-emitting layer by transporting holes and blocking electrons. As the material of the electron blocking layer, a known electron blocking layer material can be used.

[0104] - Exciton blocking layer -

[0105] The so-called exciton blocking layer is a layer used to block the excitons generated by the recombination of holes and electrons in the light-emitting layer from diffusing to the charge transport layer. By inserting this layer, the excitons can be efficiently enclosed in the light-emitting layer, which can improve the luminous efficiency of the element. The exciton blocking layer can be inserted between two adjacent light-emitting layers in an element with two or more light-emitting layers adjacent. As the material of such an exciton blocking layer, a known exciton blocking layer material can be used.

[0106] Examples of layers adjacent to the light-emitting layer include a hole blocking layer, an electron blocking layer, and an exciton blocking layer. However, when these layers are not provided, a hole transport layer, an electron transport layer, and the like become adjacent layers.

[0107] -Hole transport layer-

[0108] The hole transport layer includes a hole transport material having the function of transporting holes, and the hole transport layer may be provided as a single layer or multiple layers.

[0109] As a hole transport material, it is a material having any of the properties of hole injection or transport and electron barrier, and can be any of organic and inorganic substances. In the hole transport layer, any one of the previously known compounds can be selected and used. As the hole transport material, for example, porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, distyrene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, especially thiophene oligomers, etc., preferably using porphyrin derivatives, arylamine derivatives and styrylamine derivatives, more preferably using arylamine derivatives.

[0110] -Electron transport layer-

[0111] The electron transport layer includes a material having a function of transporting electrons, and the electron transport layer may be provided as a single layer or multiple layers.

[0112] As an electron transport material (sometimes also serving as a hole blocking material), it is sufficient as long as it has the function of transmitting the electrons injected from the cathode to the light-emitting layer. The electron transport layer can be selected from any of the previously known compounds, for example, polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline, tris (8-hydroxyquinoline) aluminum (III) derivatives, phosphine oxide derivatives, nitro-substituted fluorene derivatives, diphenylquinone derivatives, dioxide thiopyran derivatives, carbodiimide, fluorenyl methane derivatives, anthraquinone dimethane and anthrone derivatives, bipyridine derivatives, quinoline derivatives, oxadiazole derivatives, benzimidazole derivatives, benzothiazole derivatives, indole and carbazole derivatives, etc. Furthermore, polymer materials that introduce these materials into polymer chains or use these materials as the main chain of polymers can also be used.

[0113] The film-forming method of each layer when producing the organic EL device of the present invention is not particularly limited, and the device can be produced by either a dry process or a wet process.

[0114] Example

[0115] Synthesis example 1

[0116] [Chemistry 13]

[0117]

[0118] Under a nitrogen atmosphere, 4.0 g of raw material (A), 77.3 g of raw material (B), 21.0 g of cesium carbonate (Cs2CO3), and 35.0 ml of dimethylacetamide (DMAc) were placed in a three-necked flask and stirred at 100°C for 64 hours. The reaction solution was returned to room temperature, water was added little by little, and the obtained precipitate was filtered. The filtrate was purified by silica gel column chromatography. Then, it was washed with methanol and the obtained solid was dried under reduced pressure to obtain 4.5 g of compound (T1) (yield: 40%). APCI-TOFMS (Atmospheric pressure chemical ionization-time-of-flight mass spectrometer) m / z 530 [M+1] +

[0119] Synthesis example 2

[0120] [Chemistry 14]

[0121]

[0122] Under nitrogen atmosphere, 2.3 g of raw material (C), 4.5 g of raw material (T1), 8.1 g of cesium carbonate (Cs2CO3), and 13.0 ml of dimethylacetamide (DMAc) were placed in a three-necked flask and stirred at 130°C for 8 hours. The reaction solution was returned to room temperature, water was added little by little, and the obtained precipitate was filtered. The filtrate was purified by silica gel column chromatography. Then, it was washed with methanol and the obtained solid was dried under reduced pressure to obtain 4.7 g of compound (T2) (yield: 71%). APCI-TOFMS m / z 783[M+1] +

[0123] Synthesis example 2

[0124] [Chemistry 15]

[0125]

[0126] Under nitrogen atmosphere, 1.4 g of raw material (T2), 0.1 g of palladium acetate (Pd(OAc)2), 0.3 g of triphenylphosphine (PPh3), 2.0 g of potassium carbonate (K2CO3), 0.8 g of benzyl triethylammonium chloride (BTEAC), and 28.0 ml of dimethylacetamide (DMAc) were placed in a three-necked flask and stirred at 120°C for 3 hours. The reaction solution was returned to room temperature, water was added little by little, and the obtained precipitate was filtered. The filtrate was washed with xylene and methanol, and the obtained solid was dried under reduced pressure to obtain 0.4 g of compound (D1) (yield: 36%). APCI-TOFMS m / z623[M+1] +

[0127] Example 1

[0128] On a quartz substrate, the vacuum evaporation method was used with a vacuum degree of 4.0×10 -5 Pa film-formed the thin film shown below. The compound (H23) as the main body and the compound (D1) as the dopant were co-deposited from different evaporation sources to form a light-emitting layer with a thickness of 100 nm. At this time, the co-evaporation was performed under the evaporation condition that the concentration of the compound (D1) was 1% by mass. The organic thin film of Example 1 was prepared.

[0129] For the organic film, the photoluminescence quantum yield (PLQY) was measured using the Absolute PL (photoluminescence) Quantum Yield Measurement) C9920-03G system (Hamamatsu Photonics Co., Ltd.). By using the C9920-03G system, the light excitation and luminescence spectrum of the organic film can be continuously measured, and the PLQY of the organic film can be calculated by calculating the energy balance at this time. The maximum emission wavelength, half-value width, PLQY and CIE (Commission Internationale de l'Eclairage, International Commission on Illumination) coordinates are determined using software U6039-05 version 3.6.0. The maximum emission wavelength and half-value width are provided in nm, the PLQY is provided in %, and the CIE coordinates are provided as x and y values. In addition, the excitation wavelength in the PLQY measurement is set to 340nm.

[0130] The excited singlet energy (S1) and the excited triplet energy (T1) are measured as follows. For the organic thin film, regarding S1, the luminescence spectrum of the vapor-deposited film is measured and a tangent is drawn to the rise of the short-wavelength side of the luminescence spectrum, and the wavelength value λedge [nm] of the intersection of the tangent and the horizontal axis is substituted into the following formula (i) to calculate S1.

[0131] S1[eV]=1239.85 / λedge (i)

[0132] On the other hand, regarding T1, the phosphorescence spectrum of the vapor deposited film is measured, a tangent line is drawn to the rise of the phosphorescence spectrum on the short wavelength side, and the wavelength value λedge [nm] of the intersection of the tangent line and the horizontal axis is substituted into the formula (ii) to calculate T1.

[0133] T1[eV]=1239.85 / λedge (ii)

[0134] ΔEST is calculated by subtracting T1 from S1 calculated as described above.

[0135] Comparative Example 1

[0136] An organic thin film was produced in the same manner as in Example 1 except that the dopant was changed to BD-1. The maximum emission wavelength, half value width, PLQY, CIE coordinates, and ΔEST were determined in the same manner as in Example 1.

[0137] [Chemistry 16]

[0138]

[0139] The compounds used in Examples and Comparative Examples are shown below.

[0140] [Chemistry 17]

[0141]

[0142] Table 1 shows the results of measuring the maximum emission wavelength, half-value width, chromaticity (CIEx, CIEy), PLQY, and ΔEST of the emission spectrum of the produced organic thin film.

[0143] [Table 1]

[0144]

[0145] Table 1 shows that the light-emitting material of the present invention has a PLQY equivalent to that of the organic thin film of Comparative Example 1 using BD-1 as the light-emitting material, has high efficiency characteristics, and also shows that it emits blue light due to the maximum emission wavelength.

[0146] S1 and T1 can also be obtained by actual measurement in the manner described above, or by theoretical calculation using the molecular orbital method program shown below. In addition, the ΔEST (theoretical (theo)) obtained by the following calculation method has a high correlation with the actually measured ΔEST. Generally speaking, if its value is small, reverse intersystem crossing is likely to occur, so that triplet excitons can be efficiently used for luminescence, and thus high luminescence efficiency can be expected. In addition, for thermally activated delayed fluorescent materials with a small ΔEST (theoretical), the actually measured ΔEST is also generally small.

[0147] In the case of D1, D13 and D23, which are luminescent materials represented by the general formula (1), the molecular orbital method program Gaussian 16 was used to perform structural optimization calculations at the B3LYP / 6-31G* level by density functional theory (DFT), and S1 (theoretical), T1 (theoretical) and ΔEST (theoretical) were calculated at the TD-B3LYP / 6-31G* level. The results are shown in Table 2.

[0148] [Table 2]

[0149] Compound ΔEST(theoretical)[eV] D1 0.35 D13 0.27 D23 0.37

[0150] According to Table 2, the value of ΔEST (theoretical) of compound D1 obtained by theoretical calculation using the molecular orbital method program is substantially equivalent to the ΔEST actually measured for compound D1 shown in Example 1, and the ΔEST (theoretical) obtained by theoretical calculation and the ΔEST actually measured have a high correlation. Therefore, it is shown that the ΔEST (theoretical) of the theoretically calculated values ​​of D13 and D23 show values ​​equivalent to the ΔEST actually measured, and it is known that the compound represented by general formula (1) has a preferred ΔEST, and it is known that it has high characteristics and emits light like the example compound D1.

[0151] Example 2

[0152] On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, a vacuum deposition method was used at a vacuum degree of 4.0×10 -5 Pa stacks the thin films shown below. First, on ITO, the HAT-CN shown above is formed to a thickness of 10nm as a hole injection layer, and then HT-1 is formed to a thickness of 25nm as a hole transport layer. Next, HT-2 is formed to a thickness of 5nm as an electron blocking layer. Then, the compound (H31) as the main body and the compound (D1) as the dopant are co-deposited from different evaporation sources to form a light-emitting layer with a thickness of 30nm. At this time, co-evaporation is performed under evaporation conditions where the concentration of the compound (D1) is 1% by mass. Next, the compound (H31) is formed to a thickness of 5nm as a hole blocking layer. Next, ALQ3 is formed to a thickness of 40nm as an electron transport layer. Furthermore, on the electron transport layer, lithium fluoride (LiF) is formed to a thickness of 1nm as an electron injection layer. Finally, on the electron injection layer, aluminum (Al) is formed to a thickness of 70nm as a cathode to prepare the organic EL element of Example 2.

[0153] Comparative Example 2

[0154] An organic EL device was produced in the same manner as in Example 2 except that BD-1 was used as the dopant.

[0155] The maximum emission wavelength, external quantum efficiency, and lifetime of the emission spectrum of the prepared organic EL element are shown in Table 3. The maximum emission wavelength and external quantum efficiency were obtained when the driving current density was 2.5 mA / cm 2 The lifetime is measured when the driving current density is 40 mA / cm 2 The time it takes for the brightness to decay to 90% of the initial brightness.

[0156] [Table 3]

[0157]

[0158] Table 3 shows that the organic EL element using the light-emitting material of the present invention emits blue light according to the maximum emission wavelength and shows particularly excellent results in life characteristics compared with the organic EL element using BD-1 as the light-emitting material.

[0159] Industrial Applicability

[0160] According to the luminescent material of the present invention, an organic EL element that emits light with high efficiency and has high driving stability and is practically useful can be obtained. In addition, the luminescent material of the present invention shows a maximum wavelength in the blue, light blue or green spectral region. The luminescent material particularly shows a maximum wavelength in the range of 410nm to 550nm, preferably in the range of 430nm to 495nm. The photoluminescence quantum yield of the luminescent material of the present invention can be 40% or more. The use of the luminescent material of the present invention provides a device with higher efficiency. In addition, an organic EL element having a luminescent layer containing the luminescent material has high luminescence efficiency.

[0161] Description of Figure Numbers

[0162] 1: substrate, 2: anode, 3: hole injection layer, 4: hole transport layer, 5: light-emitting layer, 6: electron transport layer, 7: cathode

Claims

1. A light-emitting material represented by the following general formula (1). [Chemistry 1] Here, A 1 CR 1 , C or N; among which, In the general formula (1), A 1 The number of N in one six-membered ring is 2 or less; 1 Each of them is independently hydrogen, cyano, deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted 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 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or a substituted or unsubstituted linked aromatic group in which two to five of the above aromatic hydrocarbon groups and aromatic heterocyclic groups are linked. Ring E is a heterocyclic ring represented by formula (1a), and ring E is condensed with an adjacent ring at any position. a, b, c, and d are respectively 0 or 1, and not all of a, b, c, and d are 0. 2 . The light-emitting material according to claim 1 , satisfying any one of a=b=c=0 and d=1, a=c=d=0 and b=1, a=d=1 and b=c=0, or a=d=0 and b=c=1.

3. The light-emitting material according to claim 1, which is represented by any one of the following general formulas (2) to (21). [Chemistry 2-1] [Chemistry 2-2] [Chemistry 2-3] [Chemistry 2-4] 4 . The light-emitting material according to claim 1 , which is represented by any one of the general formulas (2) to (11). 5 . The light-emitting material according to claim 1 , which is represented by any one of the general formulas (2) to (7). The light-emitting material according to claim 1 , represented by the general formula (2).

7. The luminescent material according to claim 1, characterized in that The difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) is 0.40 eV or less.

8. The luminescent material according to claim 1, characterized in that At least one R 1 It is deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms.

9. The luminescent material according to claim 1, characterized in that At least two R's 1 It is deuterium, a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms.

10. The luminescent material according to claim 1, characterized in that At least two R's 1 It is a substituted or unsubstituted diarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 44 carbon atoms, a substituted or unsubstituted diheteroarylamino group having 12 to 44 carbon atoms, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms.

11. The luminescent material according to claim 1, characterized in that All A 1 By CR 1 Or C represents. 12 . An organic electric field light emitting device comprising one or more light emitting layers between an anode and a cathode facing each other, wherein at least one light emitting layer contains the light emitting material according to claim 1 .

13. The organic electroluminescent element according to claim 12, characterized in that: The light-emitting layer further contains a biscarbazole compound as a host material.

14. The organic electroluminescent element according to claim 12, characterized in that: The light-emitting layer further contains a tricarbazole compound as a host material.

15. The organic electroluminescent element according to claim 12, characterized in that: The light-emitting layer further contains an anthracene compound as a host material.

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