Luminescent material, and organic electroluminescent element

Abstract

The present invention provides: a luminescent material by which an organic electroluminescent (EL) element that emits light with high efficiency and has a long lifespan can be obtained; and the organic EL element obtained using said luminescent material.　Specifically, the present invention provides a luminescent material represented by general formula (1) below, and an organic EL element obtained using the same. Each A1 independently represents CR1, C, or N, and each R1 is independently a hydrogen or the like. Note that the number of N present in one six-membered ring that includes A1 is 2 or less.　The ring E is a heterocycle represented by formula (1a) and is fused with an adjacent ring at a desired position. A, b, c, and d are each independently 0 or 1, and a, b, c, and d are not all 0.

Description

Light-emitting material and organic electroluminescent device

[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 in a light-emitting layer.

[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. At this time, due to the statistical law of electron spin, singlet excitons and triplet excitons are generated in a ratio of 1:3. It is said that the internal quantum efficiency of fluorescent organic EL elements that use emission from singlet excitons is limited to 25%. On the other hand, it is known that the internal quantum efficiency of phosphorescent organic EL elements that use emission from triplet excitons can be increased to 100% if intersystem crossing from singlet excitons is efficiently performed.

[0003] In recent years, technology for extending the lifetime of phosphorescent organic EL elements has progressed, and they are being applied to displays of mobile phones, etc. However, with regard to blue organic EL elements, practical phosphorescent organic EL elements have not yet been developed, and there is a demand for the development of blue organic EL elements that are highly efficient and have a long lifetime.

[0004] More recently, highly efficient delayed fluorescence organic EL elements utilizing delayed fluorescence have been developed. For example, Patent Document 1 discloses an organic EL element utilizing the TTF (Triple-Triple 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 elements, further improvements in efficiency are required.

[0005] On the other hand, Patent Document 2 discloses an organic EL device utilizing the thermally activated delayed fluorescence (TADF) 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 level and the triplet level, and is thought to theoretically increase the internal quantum efficiency to 100%. Specifically, Patent Document 2 discloses a thermally activated delayed fluorescence material composed of an indolocarbazole compound.

[0006] Furthermore, Patent Documents 3, 4, and 5 disclose a material made of a polycyclic aromatic compound including an indolocarbazole skeleton fused at a specific position, and an organic EL device using the same, but do not disclose an organic EL device using, as a light-emitting material, a material made of a polycyclic aromatic compound in which a benzothiophene skeleton is further fused to an indolocarbazole skeleton fused at a specific position.

[0007] WO2010 / 134350 Publication No. WO2011 / 070963 Publication No. WO2019 / 111971 Publication No. JP2021-172592 Publication No. WO2021 / 167045 Publication

[0008] In order to apply organic EL elements as display elements or light sources for flat panel displays and the like, it is necessary to improve the luminous efficiency of the elements and at the same time ensure sufficient stability during operation. The present invention has been made in view of such current circumstances, and an object of the present invention is to provide a luminescent material that can provide a practically useful organic EL element that emits light with high efficiency and has high operating stability, and an organic EL element using the same.

[0009] That is, the present invention provides a light-emitting material represented by the following general formula (1).

[0010] Here, A １ are each independently CR １ , C or N. However, in the general formula (1), A １ The number of N atoms present in one six-membered ring containing R is 2 or less. １are each 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 formed by linking 2 to 5 of the aromatic hydrocarbon groups and aromatic heterocyclic groups. Ring E is a heterocycle represented by formula (1a), and ring E is fused to an adjacent ring at any position. However, a, b, c, and d are each 0 or 1, and a, b, c, and d cannot all be 0. It is also preferable that 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.

[0011] A preferred embodiment of the light-emitting material represented by the above general formula (1) is any of the following general formulas (2) to (21). １ has the same meaning as general formula (1).

[0012] Of the general formulas (2) to (21), the light-emitting material is preferably represented by any one of the general formulas (2) to (11), more preferably by any one of the general formulas (2) to (7), and even more preferably by the light-emitting material represented by the general formula (2). １ is CR １ or C.

[0013] The light-emitting material represented by any one of the general formulas (1) to (21) above has at least one or two R １is preferably 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 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.

[0014] The light-emitting material represented by any one of the general formulas (1) to (21) preferably has a difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of 0.40 eV or less.

[0015] The present invention also 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 a light-emitting material represented by any one of the general formulas (1) to (21) above.

[0016] The light-emitting layer may further contain a biscarbazole compound, a tricarbazole compound, or an anthracene compound as a host material.

[0017] The light-emitting material of the present invention can provide a practically useful organic EL device that emits light with high efficiency and has high driving stability. Furthermore, the light-emitting material of the present invention exhibits a maximum wavelength in the blue, light blue, or green spectral region. This light-emitting material exhibits a maximum wavelength, particularly, between 410 nm and 550 nm, preferably between 430 nm and 495 nm. The photoluminescence quantum yield of the light-emitting material of the present invention can be 40% or more. Use of the light-emitting material of the present invention leads to more efficient devices. Furthermore, organic EL devices having a light-emitting layer containing the material exhibit high luminous efficiency.

[0018] FIG. 1 is a cross-sectional view showing an example of the structure of an organic EL element used in the present invention.

[0019] The light-emitting material of the present invention is represented by any one of the general formulas (1) to (21). Preferably, it is a light-emitting material represented by any one of the general formulas (2) to (11), more preferably a light-emitting material represented by any one of the general formulas (2) to (7), and even more preferably a light-emitting material represented by the general formula (2). The organic EL device of the present invention has one or more light-emitting layers between an opposing anode and cathode, and at least one of the light-emitting layers contains a compound represented by any one of the general formulas (1) to (21) as a light-emitting material. This organic EL device has multiple layers between the opposing anode and cathode, at least one of which is a light-emitting layer, and the light-emitting layer may contain a host material as needed. General formula (1) is described below. The compounds represented by general formulas (1) to (21) typically have a structure in which a benzothiophene skeleton is further fused to an indolocarbazole skeleton fused at a specific position, or a structure similar thereto.

[0020] In general formula (1), A １ is CR １ , N, or carbon atom. １ A present in one six-membered ring containing １ The number of N in this A is 2 or less. １ A six-membered ring containing １ Two of A are carbon atoms, and these carbon atoms are shared with ring E. Preferably, all A １ is CR １ , or C.

[0021] R １are each independently hydrogen, a cyano group, 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 formed by linking 2 to 5 of the aromatic hydrocarbon groups and the aromatic heterocyclic groups. 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 formed by linking 2 to 4 of the aromatic hydrocarbon groups and the aromatic heterocyclic groups. More preferred are 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 formed by linking two or three of the aromatic hydrocarbon groups and aromatic heterocyclic groups.

[0022] At least one R １ is preferably 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 at least two R １is more preferably 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 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.

[0023] R １ Specific examples of when represents an unsubstituted diarylamino group, an unsubstituted arylheteroarylamino group, an unsubstituted diheteroarylamino group, or an aliphatic hydrocarbon group include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, bisdibenzofuranylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl. Preferred are diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, bisdibenzofuranylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl. More preferred are diphenylamino, phenylbiphenylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, and butyl. When it represents an aliphatic hydrocarbon group, it may be linear, branched or cyclic.

[0024] R １Specific examples of when is an unsubstituted aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxal Examples of such a group include quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, indolocarbazole, and a group formed by removing one hydrogen atom from a compound formed by linking 2 to 5 of these. Preferred examples include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, 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, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, and a group formed by removing one hydrogen atom from a compound formed by linking 2 to 4 of these.More preferred are 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, carbazole, or a group formed by removing one hydrogen from a compound formed by linking two or three of these.

[0025] In this specification, the aromatic hydrocarbon group, aromatic heterocyclic group, and linking aromatic group may each have a substituent. The same applies to the aryl group and heteroaryl group contained in the diarylamino group, arylheteroarylamino group, and diheteroarylamino group.

[0026] When the substituent is substituted, 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. When the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, the substituent may be linear, branched, or cyclic. When the diarylamino group, arylheteroarylamino group, diheteroarylamino group, aryloxy group, or arylthio group substitutes for the aromatic hydrocarbon group, aromatic heterocyclic group, aromatic ring of the linking aromatic group, or the aryl group or heteroaryl group contained in the diarylamino group, arylheteroarylamino group, or diheteroarylamino group, a single bond bonds nitrogen and carbon, oxygen and carbon, or sulfur and carbon. The number of substituents is 0 to 5, preferably 0 to 2. When the aromatic hydrocarbon group or aromatic heterocyclic group has a substituent, the number of carbon atoms in the substituent is not included in the calculation of the number of carbon atoms. However, it is preferable that the total number of carbon atoms, including the number of carbon atoms in the substituent, falls within the above range.

[0027] Specific examples of the substituent include cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, 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 is used.

[0028] In this specification, a linking aromatic group refers to an aromatic group in which aromatic groups are linked by single bonds. It is an aromatic group in which two or more aromatic groups are linked, and these may be linear or branched. The aromatic group may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and the multiple aromatic groups may be the same or different. An aromatic group that corresponds to a linking aromatic group is different from a substituted aromatic group.

[0029] In this specification, it is understood that hydrogen may be deuterium. That is, in general formulas (1) to (21), R １ A part or all of the H in the substituents may be deuterium.

[0030] Each ring E is independently a heterocycle represented by formula (1a), and ring E is fused to the adjacent ring at any position.

[0031] a, b, c, and d each independently represent 0 or 1, and a, b, c, and d are not all represented by 0. It is preferable that any 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 it is more preferable that a=b=c=0 and d=1 is satisfied.

[0032] Preferred embodiments of the general formula (1) include the general formulae (2) to (11). More preferred are the general formulae (2) to (7), and even more preferred is the general formula (2). The general formulae (2) to (7) correspond to the structure in general formula (1) where a, b, and c are all 0 and d is 1, and the general formulae (8) to (11) correspond to the structure in which a, c, and d are all 0 and b is 1. Furthermore, the general formulae (12) to (17) correspond to the structure in which a and d are all 1 and b and c are all 0, and the general formulae (18) to (21) correspond to the structure in which a and d are all 0 and b and c are all 1.

[0033] Specific examples of the light-emitting materials represented by the general formulas (1) to (21) are shown below, but the light-emitting materials are not limited to these exemplary compounds.

[0034]

[0035] By incorporating the light-emitting material represented by any one of the general formulas (1) to (21) into the light-emitting layer, it is possible to obtain an organic EL device that emits light with high efficiency and has high driving stability, making it excellent for practical use.

[0036] 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.

[0037] 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 cathode side or the anode side of the emitting layer, or both 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.

[0038] 1 , it is also possible to laminate the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, hole injection layer 3, and anode 2 in this order on the substrate 1, and in this case too, layers can be added or omitted as necessary. In the organic EL element described above, layers constituting the laminated structure on the substrate other than electrodes such as the anode and cathode may be collectively referred to as organic layers.

[0039] The organic EL device of the present invention is preferably supported on a substrate. There are no particular limitations on the substrate, and any substrate conventionally used in organic EL devices, such as glass, transparent plastic, or quartz, can be used.

[0040] Anode—Preferably, the anode material in an organic EL device is a material consisting of a metal, alloy, electrically conductive compound, or mixture thereof with a high work function (4 eV or greater). 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 producing transparent conductive films, such as IDIXO (In2O3-ZnO), may also be used. The anode may be formed by forming a thin film of these electrode materials by methods such as vapor deposition or sputtering, followed by forming a pattern of the desired shape using a photolithography method. Alternatively, if pattern precision is not required (approximately 100 μm or greater), a pattern may be formed using a mask of the desired shape during vapor deposition or sputtering of the electrode material. Alternatively, when a coatable material such as an organic conductive compound is used, wet film formation methods such as printing or coating can also be used. When light is extracted from this anode, it is desirable for the transmittance to be greater than 10%, and the sheet resistance of the anode as a whole to be 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.

[0041] Cathode On the other hand, the cathode material is made of a metal (referred to as an electron injecting metal), alloy, electrically conductive compound, or mixture thereof having a low work function (4 eV or less). Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, a magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, indium, a lithium / aluminum mixture, and rare earth metals. Among these, from the viewpoints of electron injection properties and durability against oxidation, etc., mixtures of an electron injecting metal and a second metal that is a metal with a larger and more stable work function than the electron injecting metal are preferred, such as a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, a lithium / aluminum mixture, and aluminum. The cathode can be produced by forming a thin film of these cathode materials by methods such as vapor deposition or sputtering. The cathode preferably has a sheet resistance of several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit emitted light, it is advantageous if either the anode or cathode of the organic EL element is transparent or semitransparent, as this improves the luminance of emitted light.

[0042] Furthermore, a transparent or semitransparent cathode can be fabricated by forming the above-mentioned metal as a cathode with a film thickness of 1 to 20 nm 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.

[0043] -Light-emitting layer- The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and cathode, respectively. In the light-emitting layer, a light-emitting material represented by any of general formulas (1) to (21) may be used alone, or this light-emitting material may be used together with a host material. When a light-emitting material is used together with a host material, the light-emitting material is responsible for emitting light in the device.

[0044] The content of the light-emitting material is preferably 0.1 to 50 wt %, more preferably 0.1 to 40 wt %, based on the host material.

[0045] The host material in the light-emitting layer can be a known host material used in phosphorescent or fluorescent light-emitting devices. Usable known host materials are compounds having hole-transporting ability and electron-transporting ability and a high glass transition temperature, and preferably have a triplet excitation energy (T1) greater than the triplet excitation energy (T1) of the light-emitting material represented by general formula (1). A TADF-active compound may also be used as the host material, and in this case, the difference between the singlet excitation energy (S1) and the triplet excitation energy (T1) (ΔEST=S1-T1) is preferably 0.20 eV or less.

[0046] Such host materials can be selected from many known patent documents, etc. Specific examples of the host material include, but are not limited to, indole compounds, carbazole compounds and polymers thereof, anthracene compounds, indolocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, triazole compounds, oxazole compounds, oxadiazole compounds, imidazole compounds, phenylenediamine compounds, arylamine compounds, anthracene compounds, fluorenone compounds, stilbene compounds, triphenylene compounds, carborane compounds, porphyrin compounds, phthalocyanine compounds, metal complexes of 8-quinolinol compounds, metal phthalocyanines, various metal complexes typified by metal complexes of benzoxazole and benzothiazole compounds, poly(N-vinylcarbazole) compounds, aniline copolymer compounds, thiophene oligomers, polythiophene compounds, polyphenylene compounds, polyphenylenevinylene compounds, and polyfluorene compounds. Preferred examples include carbazole compounds and their polymers, anthracene compounds, indolocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, anthracene compounds, triphenylene compounds, carborane compounds, and porphyrin compounds. More preferred examples include biscarbazole compounds, tricarbazole compounds, and anthracene compounds, which are polymers of carbazole compounds. Note that hydrogen in the host materials typified by the above compounds may be substituted with deuterium.

[0047] Specific examples of the biscarbazole compound are shown below, but the invention is not limited to these exemplary compounds.

[0048] Specific examples of the anthracene compound are shown below, but the anthracene compound is not limited to these exemplary compounds.

[0049] One light-emitting layer may contain only one type of host, or two or more types of hosts may be used. When two or more types of hosts are used, at least one is preferably an electron-transporting compound such as the above-described biscarbazole compound, tricarbazole compound, or anthracene compound, and the other hosts are preferably hole-transporting compounds such as carbazole compounds or indolocarbazole compounds. When two or more types of hosts are used, each host is vapor-deposited from a different vapor deposition source, or they are premixed before vapor deposition to form a premix, so that two or more types of hosts can be simultaneously vapor-deposited from one vapor deposition source.

[0050] The light-emitting material and the host material can be vapor-deposited from different vapor deposition sources, or they can be premixed before vapor deposition to form a premixture, allowing the light-emitting material and the host material to be simultaneously vapor-deposited from one vapor deposition source.

[0051] 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.

[0052] The host and its premix may be in the form of a powder, stick, or granules.

[0053] Injection layer: An injection layer is a layer provided between an electrode and an organic layer to reduce driving voltage and improve luminance, and includes a hole injection layer and an electron injection layer. An injection layer 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. An injection layer can be provided as needed.

[0054] -Hole Blocking Layer- In a broad sense, the hole blocking layer functions as an electron transport layer and is made of a hole blocking material that has the function of transporting electrons but has a significantly low ability to transport holes. By transporting electrons while blocking holes, the probability of electron and hole recombination in the light-emitting layer can be improved. Known hole blocking materials can be used for the hole blocking layer. Multiple hole blocking materials may also be used in combination.

[0055] - 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 is possible to improve the probability of recombination of electrons and holes in the light-emitting layer. Known electron blocking layer materials can be used as the material for the electron blocking layer.

[0056] -Exciton Blocking Layer- An 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 transport layer. Insertion of this layer makes it possible to efficiently confine excitons within the light-emitting layer, thereby improving the luminous efficiency of the device. In a device in which two or more light-emitting layers are adjacent to each other, an exciton blocking layer can be inserted between two adjacent light-emitting layers. Known exciton blocking layer materials can be used as the material for such an exciton blocking layer.

[0057] 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.

[0058] -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.

[0059] 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 derivatives are more preferred.

[0060] - Electron Transport Layer - The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer may be a single layer or multiple layers.

[0061] 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 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 any of these materials are incorporated into a polymer chain or in which any of these materials form the polymer backbone may also be used.

[0062] When the organic EL element 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.

[0063] Synthesis Example 1 Under a nitrogen atmosphere, 4.0 g of raw material (A), 77.3 g of raw material (B), and cesium carbonate (Cs ２ CO ３ 21.0 g of methylpropional (T1) 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 resulting precipitate was collected by filtration. The collected precipitate was purified by silica gel column chromatography. It was then washed with methanol, and the resulting solid was dried under reduced pressure to obtain 4.5 g of compound (T1) (yield: 40%). APCI-TOFMS m / z 530 [M+1] ＋

[0064] Synthesis Example 2 Under a nitrogen atmosphere, 2.3 g of raw material (C), 4.5 g of raw material (T1), and cesium carbonate (Cs ２ CO３ 8.1 g of methylpropional (T2) 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 resulting precipitate was collected by filtration. The collected precipitate was purified by silica gel column chromatography. It was then 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] ＋

[0065] Synthesis Example 2 Under a nitrogen atmosphere, 1.4 g of the raw material (T2), palladium acetate (Pd(OAc) ２ ) 0.1 g, triphenylphosphine (PPh3) 0.3 g, potassium carbonate (K ２ CO ３ 2.0 g of methyl methyl ammonium chloride (Methyl ammonium chloride) (BTEAC), 0.8 g of benzyltriethylammonium 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, and water was added little by little to obtain a precipitate, which was then filtered off. The filtered product 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 / z 623 [M+1] ＋

[0066] Example 1 The following thin films were deposited on a quartz substrate by vacuum deposition at a vacuum level of 4.0 × 10 －５ The organic thin film according to Example 1 was prepared. Compound (H23) as a host and compound (D1) as a dopant were co-deposited from different deposition sources to form an emitting layer having a thickness of 100 nm. The co-deposition was carried out under deposition conditions such that the concentration of compound (D1) was 1 mass %.

[0067] The photoluminescence quantum yield (PLQY) of the above organic thin films was measured using an Absolute PL Quantum Yield Measurement C9920-03G system (Hamamatsu Photonics K.K.). Using the C9920-03G system, the photoexcitation and emission spectra of the organic thin films can be continuously measured, and the PLQY of the organic thin films can be calculated by calculating the energy balance during this process. The maximum emission wavelength, half-width, PLQY, and CIE coordinates were determined using software U6039-05 version 3.6.0. The maximum emission wavelength and half-width are given in nm, PLQY in %, and CIE coordinates are given as x and y values. The excitation wavelength for PLQY measurements was 340 nm.

[0068] The excited singlet energy (S1) and excited triplet energy (T1) are measured as follows. For the organic thin film, S1 is calculated by measuring the emission spectrum of the evaporated film, drawing a tangent to the rising edge on the short wavelength side of the emission spectrum, and substituting the wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis into the following formula (i): S1 [eV] = 1239.85 / λedge (i)

[0069] On the other hand, T1 is calculated by measuring the phosphorescence spectrum of the 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)

[0070] ΔEST is calculated by subtracting T1 from S1 calculated above.

[0071] Comparative Example 1 An organic thin film was prepared in the same manner as in Example 1 except that the dopant was changed to BD-1, and the maximum emission wavelength, half width, PLQY, CIE coordinates, and ΔEST were determined in the same manner as in Example 1.

[0072] The compounds used in the examples and comparative examples are listed below.

[0073] The maximum emission wavelength, half width, chromaticity (CIEx, CIEy), PLQY, and ΔEST of the emission spectrum of the prepared organic thin film were measured, and the results are shown in Table 1.

[0074]

[0075] From Table 1, it can be seen that the luminescent material of the present invention exhibits a PLQY equivalent to that of the organic thin film of Comparative Example 1 using BD-1 as the luminescent material, has highly efficient characteristics, and furthermore, it can be seen that the maximum emission wavelength indicates blue light emission.

[0076] S1 and T1 can be determined by actual measurement as described above, or by theoretical calculation using a molecular orbital program as shown below. The ΔEST(theo) obtained by the calculation method described below is highly correlated with the measured ΔEST. Generally, the smaller the value, the more likely reverse intersystem crossing occurs, and triplet excitons can be efficiently utilized for light emission, which can lead to high luminous efficiency. Furthermore, thermally activated delayed fluorescence materials with small ΔEST(theo) generally also have small measured ΔEST. For D1, D13, and D23, which are luminescent materials represented by general formula (1), structural optimization calculations were performed at the B3LYP / 6-31G* level using density half-function theory (DFT) using the molecular orbital program Gaussian 16, and S1(theo), T1(theo), and ΔEST(theo) were calculated at the TD-B3LYP / 6-31G* level. The results are shown in Table 2.

[0077]

[0078] From Table 2, it can be seen that the value of ΔEST(theo) of compound D1 obtained by theoretical calculation using the molecular orbital method program is almost the same as the measured ΔEST of compound D1 shown in Example 1, and that there is a high correlation between ΔEST(theo) obtained by theoretical calculation and the measured ΔEST. This suggests that the theoretically calculated ΔEST(theo) values ​​of D13 and D23 are equivalent to the measured ΔEST, and it can be seen that the compounds represented by general formula (1) have suitable ΔEST and emit light with high properties like Example compound D1.

[0079] Example 2 On a glass substrate on which an anode made of ITO with a film thickness of 70 nm was formed, each of the thin films shown below was deposited by vacuum deposition at a vacuum degree of 4.0 × 10 －５ The layers were laminated at a pressure of 10 Pa. First, HAT-CN, as previously described, was formed on ITO as a hole injection layer to a thickness of 10 nm. Next, HT-1 was formed as a hole transport layer to a thickness of 25 nm. Next, HT-2 was formed as an electron blocking layer to a thickness of 5 nm. Then, compound (H31) as a host and compound (D1) as a dopant were co-deposited from different evaporation sources to form an emitting layer having a thickness of 30 nm. At this time, the co-deposition was performed under evaporation conditions such that the concentration of compound (D1) was 1% by mass. Next, compound (H31) was formed as a hole blocking layer to a thickness of 5 nm. Next, ALQ3 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 producing an organic EL device according to Example 2.

[0080] Comparative Example 2 An organic EL device was produced in the same manner as in Example 2, except that the dopant was changed to BD-1.

[0081] The maximum emission wavelength, external quantum efficiency, and lifetime of the fabricated organic EL device are shown in Table 3. The maximum emission wavelength and external quantum efficiency were measured at a driving current density of 2.5 mA / cm ２ The values ​​are those at the time of the drive current density of 40 mA / cm. ２ The time until the luminance decreased to 90% of the initial luminance was measured.

[0082]

[0083] From Table 3, it can be seen that the organic EL element using the luminescent material of the present invention emitted blue light from the maximum emission wavelength, and also showed particularly excellent results in terms of life characteristics compared to the organic EL element using BD-1 as the luminescent material.

[0084] The light-emitting material of the present invention can provide a practically useful organic EL device that emits light with high efficiency and has high driving stability. Furthermore, the light-emitting material of the present invention exhibits a maximum wavelength in the blue, light blue, or green spectral region. This light-emitting material exhibits a maximum wavelength, particularly, between 410 nm and 550 nm, preferably between 430 nm and 495 nm. The photoluminescence quantum yield of the light-emitting material of the present invention can be 40% or more. Use of the light-emitting material of the present invention leads to more efficient devices. Furthermore, organic EL devices having a light-emitting layer containing the material exhibit high luminous efficiency.

[0085] 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 any one of the following general formulas (2) to (18) and (20) to (21): 【Chemistry 1-1】 【Chemistry 1-2】 【Chemistry 1-3】 【Chemistry 1-4】 Here, A １ are each independently CR １ , C or N. However, in the general formulae (2) to (18) and (20) to (21), A １ The number of N's present in one six-membered ring containing R is 2 or less. １ each independently represents a hydrogen atom, a cyano group, a deuterium atom, 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 formed by linking 2 to 5 of said aromatic hydrocarbon groups and said aromatic heterocyclic groups.

2. (delete)

3. (delete)

4. The light-emitting material according to claim 1, which is represented by any one of the above general formulas (2) to (11).

5. The light-emitting material according to claim 1, which is represented by any one of the above general formulas (2) to (7).

6. The light-emitting material according to claim 1 , which is represented by the general formula (2).

7. 2. The light-emitting material according to claim 1, wherein the difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) is 0.40 eV or less.

8. 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.

9. 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.

10. At least two R １ 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. All A's １ is CR １ 2. The light-emitting material according to claim 1 , wherein the light-emitting material is represented by:

12. An organic electroluminescent device comprising one or more light-emitting layers between an opposing anode and cathode, wherein at least one of the light-emitting layers contains the light-emitting material according to any one of claims 1 and 4 to 11.

13. 13. The organic electroluminescent device according to claim 12, wherein the light-emitting layer further contains a biscarbazole compound as a host material.

14. 13. The organic electroluminescent device according to claim 12, wherein the light-emitting layer further contains a tricarbazole compound as a host material.

15. 13. The organic electroluminescent device according to claim 12, wherein the light-emitting layer further contains an anthracene compound as a host material.

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