Boron-containing compound and organic EL element

Abstract

Provided are: a boron-containing compound which is a light-emitting material for a blue element; and an organic EL element. A boron-containing compound having a skeleton represented by general formula (1): # imgabs0 # X is-BAr-,-CR1R2-,-NAr-,-O-,-SiR3R4-or-S-(Ar is an aryl group, R1, R2, R3 and R4 are each independently hydrogen, an alkyl group having 1-6 carbon atoms, an alkoxy group having 1-6 carbon atoms, an amino group or an aryl group having 5-30 nuclear atoms; r1 and R2, or R3 and R4 may be linked to each other to form a ring). O is 1 or 2. C1 and C2 are carbon or aryl carbon, and C1 and C2 may each form a ring together with a carbon atom adjacent to X. And Y represents a fluorine group. 0 < = m + n < = 10 (m and n are integers of 0-5). D1 and D2 are each independently carbon or nitrogen. And Z represents hydrogen, an alkyl group having 1-6 carbon atoms, an alkoxy group having 1-6 carbon atoms, a fluoro group, or an amino group.

Description

Technical Field

[0001] The present invention relates to an organic EL element having a light-emitting layer containing a boron-containing compound as a dopant material. Background Art

[0002] In order to improve the practicality of organic electroluminescent (EL) elements, it is necessary to improve the luminous efficiency. The excitons formed by organic compounds come from singlet excitons (S 1 ) and the fluorescence from triplet excitons (T 1 ) of phosphorescence, but since their statistical generation ratio in the element is E S1 :E T1 =1:3, so in organic EL elements that use fluorescent light, the internal quantum efficiency of 25% is the limit.

[0003] Therefore, recently, a material that can convert a part of the triplet excited state into light emission has been developed by using the lowest triplet excited state (T 1 ) is upconverted to the lowest singlet excited state (S 1 ) based on thermally activated delayed fluorescence (TADF) materials. TADF materials are designed to have the lowest singlet excited state (S 1 ) and the lowest triplet excited state (T 1 ) ST becomes smaller, making S 1 -T 1 The transition between the two states (antisystem crossing) becomes easy, and fluorescence is emitted by radiative deactivation from its lowest singlet excited state. In TADF materials, the singlet exciton (S 1 ), thereby generating a higher ratio of triplet exciton energy (E T1 ) can also contribute to fluorescent luminescence, thus achieving higher luminous efficiency compared to general fluorescent materials.

[0004] Research and development of TADF materials that can achieve such high luminescence efficiency is in full swing. However, among the TADF materials developed so far, only a very small number of them show good blue luminescence.

[0005] The luminous efficiency of the luminescent layer can be improved by improving the luminescent material and also by using a host material that seals energy into the molecules of the luminescent material. For example, when the luminescent material is a blue luminescent dopant, the excitation energy level of the dopant itself is high, so the host material combined with it is required to have a higher excitation energy level. In the luminescent layer formed by combining such a dopant and a host material, excitons can be efficiently generated by the charge injected into the host, and high-efficiency luminescence can be obtained.

[0006] As a dopant and host material for the light-emitting layer, for example, a benzoquinoline acridine derivative is reported in Japanese Patent Table No. 2009-512628, which is a dopant for the light-emitting layer of a blue light-emitting element or a hole transport material for the hole transport layer. There are also reports of using nitrogen-containing heterocyclic compounds in the host of the light-emitting layer, the hole transport layer, or the hole injection layer (Japanese Patent Table No. 2012-507507).

[0007] As the main body of phosphorescent OLED, an example of using azaborine derivatives having nitrogen atoms and boron atoms at the 1,4-position has been reported (WO2011 / 143563). It has been reported that an organic EL element can be provided, which focuses on the charge transport and high luminescence efficiency derived from boron, and the unshared electron pairs of oxygen atoms, nitrogen atoms or sulfur atoms, and a conjugated boron compound having both of these atoms contributes to the charge transport and high luminescence efficiency, and has excellent luminescence efficiency or stability at high temperatures (WO2017 / 18326, Japanese Patent Publication No. 2017-126606, WO2017 / 195669).

[0008] In addition to conjugated boron compounds having oxygen atoms, nitrogen atoms or sulfur atoms as azaborine derivatives, a polycyclic heterocyclic aromatic compound has been reported, which is obtained by replacing the boron atom of the conjugated boron compound with a phosphorus atom, a phosphoryl group, a thiophosphoryl group, a silicon atom, a bismuth atom or a germanium atom (Japanese Patent Publication No. 2018-43984).

[0009] WO2018 / 159662 reports that a light-emitting material having a donor site and an acceptor site in a molecule, emitting TADF, and enabling protons to move in the molecule has a sufficiently high quantum efficiency in practical use and is suitable for a light-emitting material for an organic EL element.

[0010] In addition, a blue-light-emitting polycyclic aromatic compound having a boron atom, and a nitrogen atom and / or an oxygen atom as a light-emitting material for an organic EL element has been reported (Japanese Patent Publication No. 2020-123721); a compound in which a portion of the coronene skeleton is substituted with a boron atom and a sulfur atom (Chinese Patent Application Publication No. 113801151); a heterocyclic compound having a boron atom and two oxygen atoms or nitrogen atoms opposite thereto (WO2020 / 108899); and a heterocyclic compound having a nitrogen atom and two boron atoms opposite thereto (Japanese Patent Publication No. 2022-527591), etc. Summary of the invention

[0011] An object of the present invention is to provide a novel boron-containing compound that emits blue light, and an organic EL device containing the boron-containing compound and having both high luminous efficiency and life durability.

[0012] The boron-containing compound of the present invention has a skeleton represented by the following general formula (1).

[0013]

Chemical formula 1

[0014]

[0015] In the general formula (1), X is -BAr-, -CR 1 R 2 -、-NAr-、-O-、-SiR 3 R 4 - or -S-(Ar is aryl, R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group, or an aryl group having 5 to 30 nuclei, 1 and R 2 , or R 3 and R 4 can be connected to each other to form a ring), o is 1 or 2, C 1 and C 2 is a carbon atom or an aromatic carbon atom, C 1 and C 2 can form a ring together with the carbon atom adjacent to X, Y is a fluoro group, 0≤m+n≤10 (m and n are integers of 0 to 5), D 1 and D 2 Each of them is independently a carbon atom or a nitrogen atom, and Z is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a fluoro group, or an amino group.

[0016] In the general formula (1), preferably, D 1 and D 2 All are carbon atoms, Y is a fluoro group, 1≤m+n≤10 (m and n are integers of 0 to 5), and Z is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a fluoro group, or an amino group.

[0017] In the general formula (1), preferably, D 1 and D 2 At least one of them is a nitrogen atom, Y is a fluorine group, 0≤m+n≤10 (m and n are integers of 0 to 5), and Z is a hydrogen atom.

[0018] The organic EL device of the present invention contains the boron-containing compound.

[0019] The organic EL device of the present invention contains the boron-containing compound in the light-emitting wavelength band.

[0020] The organic EL device of the present invention contains the boron-containing compound in the light-emitting layer.

[0021] The organic EL device of the present invention contains 0.1 to 20 wt % of the boron-containing compound in the light-emitting layer.

[0022] The boron-containing compound of the present invention is a novel compound having a fused heterocyclic structure containing a boron atom and a nitrogen atom in the molecule. The novel compound has a larger HOMO-LUMO gap and a higher triplet energy (E T1 ). In addition, the triplet excited state (T 1 ) and the singlet excited state (S 1 ) has a small energy difference and exhibits thermally activated delayed fluorescence (TADF), and is therefore useful as a light-emitting material for an organic EL element.

[0023] The luminous efficiency and life of an organic EL element using the boron-containing compound as a blue dopant in a light-emitting layer are greatly improved compared to conventional blue elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic cross-sectional view showing an organic EL element according to one embodiment of the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, the present invention will be described in detail.

[0026] The boron-containing compound of the present invention has a skeleton represented by the following general formula (1).

[0027]

Chemical formula 2

[0028]

[0029] In the general formula (1), X is -BAr-, -CR 1 R 2 -、-NAr-、-O-、-SiR 3 R 4 -or-S-. o is 1 or 2.

[0030] Ar is aryl.

[0031] R 1 and R 2 R is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group, or an aryl group having 5 to 30 nuclei. 1 and R 2 Can be connected to each other to form a ring.

[0032] R 3 and R 4 R is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group, or an aryl group having 5 to 30 nuclei. 3 and R 4 Can be connected to each other to form a ring.

[0033] X is -BAr-, -NAr-, -CR 1 R 2 -、-SiR 3 R 4 -, ether bond (-O-), or thioether bond (-S-).

[0034] In the above-mentioned -NAr- and -BAr-, Ar is an aryl group having 5 to 30 nuclear atoms. The aryl group having 5 to 30 nuclear atoms and R 1 ~R 4 The specific examples in the case of an aryl group having 5 to 30 nuclear atoms are the same.

[0035] Specific examples of the -NAr- group include phenylamino, naphthylamino, and pyridylamino.

[0036] Specific examples of the -BAr- group include phenylboryl, naphthylboryl, and pyridylboryl.

[0037] -CR 1 R 2 -Middle, R 1 and R 2 Each of them is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group, or an aryl group having 5 to 30 nuclear atoms.

[0038] -SiR 3 R 4 -Middle, R 3 and R 4 Each of them is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group, or an aryl group having 5 to 30 nuclear atoms.

[0039] Examples of the alkyl group having 1 to 6 carbon atoms include linear or branched alkyl groups, specifically, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, isopentyl, sec-pentyl, 3-pentyl, tert-pentyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, and 2,3-dimethylbutyl.

[0040] Examples of the alkoxy group having 1 to 6 carbon atoms include linear or branched alkyl groups, and specifically include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, neopentoxy, isopentoxy, sec-pentoxy, 3-pentoxy, tert-pentoxy, n-hexoxy, 2-methylpentoxy, 3-methylpentoxy, 2,2-dimethylbutoxy, and 2,3-dimethylbutoxy.

[0041] Among the aryl groups having 5 to 30 nuclei, there can be mentioned monocyclic or condensed polycyclic aromatic hydrocarbon groups or heteroaromatic compound groups having substituents, specifically, phenyl, 1-naphthyl, 2-naphthyl, p-methoxyphenyl, p-tert-butylphenyl, p-tolyl, m-tolyl, o-tolyl, pentafluorophenyl, phenanthryl, pyrenyl, fluorenyl, fluoranthenyl, pyridyl, quinoxalinyl, pyrrolyl, indolyl, carbazolyl, imidazolyl, benzimidazolyl, furyl, benzofuranyl, dibenzofuranyl, phenylthio, benzothiophenyl, dibenzophenylthio, benzoxazolyl, and benzothioxazolyl.

[0042] In-CR 1 R 2 -and-SiR 3 R 4 -Middle, R 1 and R 2 , or R 3 and R 4 They may be linked to each other to form a 4- to 8-membered ring, preferably a 5- to 6-membered ring. Specifically, the 5- to 6-membered ring is a cyclopentyl group or a cyclohexyl group.

[0043] o represents the number of X. o is an integer of 1 or 2.

[0044] C 1 and C 2 is a carbon atom or an aryl carbon atom. Specifically, the aryl carbon atom is a carbon atom of an aryl group having a carbon number of 6 to 10. The aryl group is preferably a phenyl group.

[0045] C 1 and C 2 They may form a ring together with the carbon atom adjacent to X, for example, a ring as shown in the following structural formula may be formed.

[0046]

Chemical formula 3

[0047]

[0048] Y is a fluoro group. m+n represents the number of fluoro groups. m+n is an integer from 0 to 10, and m and n are integers of 0 to 5, respectively. Preferably, 1≤m+n≤10, and m and n are integers of 0 to 5, respectively.

[0049] D1 and D 2 are independently a carbon atom or a nitrogen atom. 1 and D 2 Any one of them is a carbon atom or a nitrogen atom, or both of them are carbon atoms or nitrogen atoms. 1 and D 2 The carbon atoms between them are used as nitrogen atoms and D 1 and D 2 When either or both of them are nitrogen atoms or carbon atoms, blue luminescence cannot be obtained.

[0050] Z is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a fluoro group, or an amino group. 1 ~R 4 The specific examples of the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms are the same.

[0051] Specifically, the boron-containing compound of the present invention is a compound having the following structural formula.

[0052]

Chemical formula 4

[0053]

[0054] The boron-containing compound of the present invention has a structure in which the π conjugated system is extended. It is known that molecules having a π conjugated system have a light absorption band in the visible region, and most of them can function as pigments. However, if the π conjugated system is extended, the HOMO increases and the LUMO decreases, thereby increasing the gap between the HOMO and LUMO (band gap E g On the other hand, as shown in the general formula (1), the boron-containing compound of the present invention has a boron atom and a nitrogen atom opposite thereto in the aromatic ring, and therefore has low aromaticity, and even if the conjugated system is extended, the reduction of the gap between HOMO-LUMO can be suppressed.

[0055] The boron-containing compounds of the present invention have high triplet excitation energy (E T ). In addition, in the boron-containing compound, the triplet excited state (E T ) are localized by electron perturbations of heteroelements, especially boron atoms, and the exchange interaction between the two orbitals becomes smaller, so the singlet excited state (E S ) and triplet excited state (E T ) between the energy gap (ΔE ST ) is small, showing thermally activated delayed fluorescence (TADF).

[0056] The boron-containing compound of the present invention has a bulky structure in which a ring structure containing a boron atom and a nitrogen atom is surrounded by a plurality of aromatic rings, so it is relatively rigid and has a structure that appropriately suppresses rotation or bending. By having such a structure, the boron-containing compound of the present invention can be used even in the case of S with the torsional vibration of the entire molecule. 1 -S 0 Transition (from singlet excited state (S 1 ) to the ground state (S 0 ) transition), a luminescence spectrum with very small vibration energy and extremely narrow half-value width, that is, high color purity, can be obtained.

[0057] It should be noted that, as described in the report on the known organic blue light-emitting material (DABNA-1), it is believed that even in the boron-containing compound of the present invention, S 1 -S 0 The transition is not accompanied by stretching vibration due to the multiple resonance effect of boron and nitrogen atoms.

[0058] Among the boron-containing compounds of the present invention, in FD2Me, S 1 The excitation peak from (HOMO→LUMO) to the excited state is 3.09 eV and S 1 -S 0 The oscillator strength (f) of the transition is 0.1473. In FD2A, S 1 is 3.11eV and S 1 -S 0 The oscillator strength (f) of the transition is 0.1374, which indicates that a high-purity blue emission spectrum is obtained.

[0059] In the present invention, functional groups added to the molecules of boron-containing compounds are studied to change the electronic properties and thus adjust the band gap E g While minimizing the singlet-triplet energy gap (ΔE ST ), which can temporarily transfer to the triplet excited state (E T ) returns to the singlet excited state (E S ), can extract high-efficiency blue fluorescence.

[0060] The boron-containing compound of the present invention can be produced, for example, by the method shown below. As an example, a method for producing compound BD1, which is one of the boron-containing compounds of the present invention, is shown in one example.

[0061]

Chemical formula 5

[0062]

[0063] In a four-necked flask, 4.13 g (10 mmol) of compound 1-1, 2.38 g (10 mmol) of 4,6-dibromopyrimidine, 2.88 g (30 mmol) of sodium tert-butoxide, and 1000 mL of dehydrated toluene were added, and 230 mg (0.4 mmol) of bis(dibenzylideneacetone)palladium (0) and 93 mg (0.32 mmol) of tri-tert-butylphosphonium tetrafluoroborate were added under nitrogen atmosphere, and refluxed and stirred overnight. The reaction mixture was purified to obtain 2.20 g (4.5 mmol) of compound 1-2 with a yield of 45%.

[0064] Next, 1.10 g (2.25 mmol) of compound 1-2 and 20 ml of dehydrated dichlorobenzene were added to a two-necked flask, and 9 ml (9 mmol) of 1 M boron tribromide solution was added dropwise, and the mixture was stirred at a bath temperature of 180°C for 2 hours. After that, 2.35 ml (13.5 mmol) of diisopropylethylamine was added dropwise to the reaction mixture and stirred for 5 minutes, and then stirred at room temperature for 30 minutes. The temperature was raised to 120°C, heated and stirred overnight to terminate the reaction. After purification, 290 mg (0.58 mmol) of compound BD1 was obtained with a yield of 26%. It should be noted that compound BD1 was identified by field desorption mass spectrometry (FD-MS).

[0065] It should be noted that the boron-containing compound of the present invention is not limited to the above method, and can be produced by various known methods.

[0066] The organic EL element of the present invention is formed using the boron-containing compound. The boron-containing compound is included in the light-emitting band of the organic EL element. The light-emitting band refers to the region where holes and electrons recombine to generate light, and in many cases, the light-emitting layer 5 corresponds to this region.

[0067] An organic EL element has a structure in which one or more organic layers are stacked between electrodes, for example, "anode 1 / hole injection layer 2 / hole transport layer 3 / luminescent layer 5 / electron transport layer 7 / electron injection layer 8 / cathode 9", "anode 1 / hole transport layer 3 / luminescent layer 5 / electron transport layer 7 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 / luminescent layer 5 / electron transport layer 7 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 / hole transport layer 3 / luminescent layer 5 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 / hole transport layer 3 / luminescent layer 5 / electron injection layer 8 / cathode 9", Electron transport layer 7 / cathode 9", "anode 1 / luminescent layer 5 / electron transport layer 7 / electron injection layer 8 / cathode 9", "anode 1 / hole transport layer 3 / luminescent layer 5 / electron injection layer 8 / cathode 9", "anode 1 / hole transport layer 3 / luminescent layer 5 / electron transport layer 8 / cathode 9", "anode 1 / hole injection layer 2 / luminescent layer 5 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 / luminescent layer 5 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 / luminescent layer 5 / electron transport layer 7 / cathode 9", "anode 1 / luminescent layer 5 / electron transport layer 7 / cathode 9", and "anode 1 / luminescent layer 5 / electron injection layer 8 / cathode 9". In the embodiments of the present invention, as Figure 1 , an electron blocking layer 4 and a hole blocking layer 6 are added to the above structure, and a structure in which “anode 1 / hole injection layer 2 / hole transport layer 3 / electron blocking layer 4 / luminescent layer 5 / hole blocking layer 6 / electron transport layer 7 / electron injection layer 8 / cathode 9” are stacked in this order. It should be noted that the organic layer refers to the layer other than the electrodes 1 and 9, that is, the hole injection layer 2, the hole transport layer 3, the electron blocking layer 4, the luminescent layer 5, the hole blocking layer 6, the electron transport layer 7 and the electron injection layer 8.

[0068] The substrate used is a transparent and smooth substrate having a total light transmittance of at least 70%. Specifically, a flexible transparent substrate, that is, a glass substrate with a thickness of several μm or a special transparent plastic or the like is used.

[0069] The thin films such as the anode 1, the hole injection layer 2, the hole transport layer 3, the electron blocking layer 4, the light emitting layer 5, the hole blocking layer 6, the electron transport layer 7, the electron injection layer 8, and the cathode 9 formed on the substrate are stacked by vacuum deposition or coating. In the case of vacuum deposition, the pressure is usually reduced to 10 -3 The deposition is performed by heating the deposited material in an atmosphere of less than Pa. The thickness of each layer varies depending on the type of layer or the material used, but is usually about 100 nm for the anode 1 and cathode 9 and less than 50 nm for other organic layers including the light-emitting layer 5.

[0070] Anode 1 uses a material with a large work function and a total light transmittance of generally 80% or more. Specifically, in order to transmit light other than that emitted by anode 1, transparent conductive ceramics such as indium tin oxide (ITO) or zinc oxide (ZnO), transparent conductive polymers such as polythiophene-polystyrene sulfonate (PEDOT-PSS) or polyaniline phosphorus, and other transparent conductive materials are used.

[0071] In order to efficiently transport holes from the anode 1 to the light-emitting layer 5 , a hole injection layer 2 and a hole transport layer 3 are provided between the anode 1 and the light-emitting layer 5 .

[0072] The hole injection material forming the hole injection layer 2 includes, for example, (poly(aryletherketone))triphenylamine (KLHIP:PPBI), 1,4,5,8,9,11-hexaazatriphenylhexanitrile (HATCN), and PEDOT-PSS. The hole injection layer 2 composed of these materials is also called a polymer buffer layer, and has the effect of reducing the driving voltage of the organic EL element.

[0073] The hole transport layer 3 is provided between the anode 1 and the light emitting layer 5 and is used to efficiently transport holes from the anode 1 to the light emitting layer. The hole transport material uses a material with ionization potential, that is, a material that easily excites electrons from HOMO and easily generates holes. For example, poly(9,9-dioctylfluorene-alt-N-(4-butylphenyl)diphenylamine) (TFB), 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline] (TAPC), N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (TPD), N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (NPD), N4,N4"-bis(4-dibenzofuranyl)-N4,N4",2',3',5',6'-hexaphenyl-[1,1':4',1"-terphenyl]-4,4"-diamine (4DBFHPB), 4,4',4"-tri-9-carbazolyltriphenylamine (TCTA) and 4,4',4"-tri[phenyl(m-tolyl)amino]triphenylamine) and the like.

[0074] As with other light-emitting layers used in an organic EL device, the light-emitting layer 5 preferably uses a light-emitting material composed of a dopant and a host.

[0075] As the dopant, a boron-containing compound represented by the general formula of the present invention is used.

[0076] The amount of the dopant added is preferably 0.1 to 20 wt % based on the total amount of the dopant and the host.

[0077] As the host, any known material can be used as long as it minimizes the charge injection barrier from the hole transport layer 3 or the electron transport layer 7, confines the charge to the light emitting layer 5, and prevents the extinction of the light emitting excitons. For example, an anthracene derivative having the following structural formula can be used as the host.

[0078]

Chemical formula 6

[0079]

[0080]

Chemical formula 7

[0081]

[0082] The amount of the host added is preferably 50 to 99.9 wt % of the total weight of the material for the light emitting layer 5 , and more preferably 80 to 95 wt %.

[0083] An electron blocking layer 4 may be appropriately provided between the light-emitting layer 5 and the hole transport layer 3. By providing the electron blocking layer 4, electrons can be enclosed in the light-emitting layer to increase the probability of recombination of charges in the light-emitting layer and improve the light-emitting efficiency. The electron blocking material forming the electron blocking layer 4 uses amine derivatives such as bis(biphenyl-4-yl)(3'-(9H-carbazole-9-yl)biphenyl-4-yl)amine.

[0084] In order to efficiently transport electrons from the cathode 9 to the light-emitting layer 5, a hole blocking layer 6 and an electron transport layer 7 are provided between the cathode 9 and the light-emitting layer 5. Examples of the electron transport material forming the electron transport layer 7 include 1,4-bis(1,10-phenanthroline-2-yl)benzene (DPB), 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (NBPhen), 8-hydroxyquinoline lithium (Liq), 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PymPm), 4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-phenylpyrimidine (B4PyPPm), 2-(4-biphenyl)-5-(p-tert-butylbenzene)- 1,3,4-triazole (tBu-PBD), 1,3-bis[5-(4-tert-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (OXD-7), 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ), basoproin (BCP), 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) and 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ). Among them, a mixed layer of DPB and Liq is preferred.

[0085] The hole blocking layer 6 is a layer for sealing holes in the light-emitting layer 5 to increase the probability of recombination of charges in the light-emitting layer 5 and improve the light-emitting efficiency. The hole blocking material forming the hole blocking layer 6 uses benzothiophene-triphenyltriazine (DBT-TRZ) and 1-(3'-(4-dibenzofuran-4-yl)biphenyl-3-yl)-3,5-diphenyltriazine, etc. The film thickness of the hole blocking layer 6 and the electron transport layer 7 is usually 3 to 50 nm, which can be appropriately changed according to the target.

[0086] Examples of the electron injection material forming the electron injection layer 8 include lithium fluoride (LiF) and lithium 2-hydroxy-(2,2′)-bipyridin-6-yl-phenolate (Libpp).

[0087] The cathode 9 uses a material with a low work function (less than 4 eV) and chemical stability. Specifically, cathode materials such as alloys of Al and alkali metals such as Al, AlLi, AlCa alloys, or MgAg alloys can be used. These cathode materials are formed into films by, for example, resistance heating evaporation, electron beam evaporation, sputtering, or ion plating.

[0088] Example

[0089] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

[0090] [Synthesis of Boron-Containing Compounds]

[0091] [Example 1] Synthesis of boron-containing compound BD1

[0092] (i) Synthesis of Compound 1-2

[0093]

Chemical formula 8

[0094]

[0095] In a 1000mL four-necked flask with a nitrogen inlet tube, 4.13g (10mmol) of compound 1-1, 2.38g (10mmol) of 4,6-dibromopyrimidine, 2.88g (30mmol) of sodium tert-butoxide, and 1000mL of dehydrated toluene were added, and nitrogen was bubbled for one hour. Next, 230mg (0.4mmol) of bis(dibenzylideneacetone)palladium (0) and 93mg (0.32mmol) of tri-tert-butylphosphonium tetrafluoroborate were added, and refluxed with stirring overnight. The disappearance of the raw material was confirmed by thin layer chromatography (TLC) for the reaction mixture. The reaction mixture was extracted with toluene, washed with brine, and MgSO 4 After drying, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography to obtain 2.20 g (4.5 mmol) of Compound 1-2 in a yield of 45%.

[0096] (ii) Synthesis of Compound BD1 (boron-containing compound)

[0097]

Chemical formula 9

[0098]

[0099] 1.10 g (2.25 mmol) of compound 1-2 and 20 ml of dehydrated dichlorobenzene were added to a degassed 50 mL two-necked flask and dissolved. 9 ml (9 mmol) of 1 M boron tribromide solution was added dropwise, stirred directly for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. After that, ice bath was added to 0°C, 2.35 ml (13.5 mmol) of diisopropylethylamine was added dropwise, stirred directly for 5 minutes, and then stirred at room temperature for 30 minutes. After that, the temperature was raised to 120°C and heated and stirred overnight. After cooling to room temperature, short column treatment was performed with silica gel. The obtained residue was refined by silica gel column chromatography and recrystallization to obtain 290 mg (0.58 mmol) of compound BD1 with a yield of 26%.

[0100] By measurement by FD-MS (field desorption mass spectrometry), a mass spectrum of m / Z=496 of the obtained compound BD1 was observed, and thus the compound BD1 was identified as a compound of the aforementioned structure.

[0101] [Example 2] Synthesis of boron-containing compound BD2

[0102] (i) Synthesis of Compound 2-2

[0103]

Chemical formula 10

[0104]

[0105] In a 300mL four-necked flask equipped with a stirrer, 7.76g (20.0mmol) of compound 2-1, 4.48g (48mmol) of aniline, 10.76g (112mmol) of sodium tert-butoxide, and 200ml of dehydrated toluene were added, and nitrogen was bubbled for one hour. 740mg (0.80mmol) of tris (dibenzylideneacetone) dipalladium (0) and 1.12g (1.8mmol) of (±)-BINAP were added thereto, and refluxed and stirred overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The insoluble matter was filtered through diatomaceous earth filtration, and the filtrate was concentrated. The obtained residue was purified by silica gel column chromatography to obtain 8.18g (16.4mmol) of compound 2-2 with a yield of 82%.

[0106] (ii) Synthesis of Compound 2-3

[0107]

Chemical formula 11

[0108]

[0109] In a 1000mL four-necked flask with a nitrogen inlet tube, 4.99g (10mmol) of compound 2-2, 2.38g (10mmol) of 4,6-dibromopyrimidine, 2.88g (30mmol) of sodium tert-butoxide, and 1000mL of dehydrated toluene were added, and nitrogen was bubbled for one hour. Next, 230mg (0.4mmol) of bis(dibenzylideneacetone)palladium (0) and 93mg (0.32mmol) of tri-tert-butylphosphonium tetrafluoroborate were added, and refluxed with stirring overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The reaction mixture was extracted with toluene, washed with brine, and MgSO 4 After drying, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography to obtain 2.41 g (4.2 mmol) of compound 2-3 with a yield of 42%.

[0110] (iii) Synthesis of Compound BD2 (boron-containing compound)

[0111]

Chemical formula 12

[0112]

[0113] 1.29 g (2.25 mmol) of compound 2-3 and 20 ml of dehydrated dichlorobenzene were added to a degassed 50 mL two-necked flask and dissolved. 9 ml (9 mmol) of 1 M boron tribromide solution was added dropwise, stirred directly for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. After that, ice bath was added to 0°C, 2.35 ml (13.5 mmol) of diisopropylethylamine was added dropwise, stirred directly for 5 minutes, and then stirred at room temperature for 30 minutes. After that, the temperature was raised to 120°C and heated and stirred overnight. After cooling to room temperature, short column treatment was performed with silica gel. The obtained residue was refined by silica gel column chromatography and recrystallization to obtain 275 mg (0.47 mmol) of compound BD2 with a yield of 21%.

[0114] By measurement by FD-MS (field desorption mass spectrometry), a mass spectrum of m / Z=582 of the obtained compound BD2 was observed, and thus compound BD2 was identified as a compound of the described structure.

[0115] [Example 3] Synthesis of boron-containing compound BD3

[0116] (i) Synthesis of Compound 2-4

[0117]

Chemical formula 13

[0118]

[0119] In a 1000mL four-necked flask with a nitrogen inlet tube, 4.99g (10mmol) of compound 2-2, 2.54g (10mmol) of 1,3-dibromo-5-fluorobenzene, 2.88g (30mmol) of sodium tert-butoxide, and 1000mL of dehydrated toluene were added, and nitrogen was bubbled for one hour. Next, 230mg (0.4mmol) of bis(dibenzylideneacetone)palladium (0) and 93mg (0.32mmol) of tri-tert-butylphosphonium tetrafluoroborate were added, and refluxed with stirring overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The reaction mixture was extracted with toluene, washed with brine, and MgSO 4 After drying, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography to obtain 2.54 g (4.3 mmol) of Compound 2-4 with a yield of 43%.

[0120] (ii) Synthesis of Compound BD3 (boron-containing compound)

[0121]

Chemical formula 14

[0122]

[0123] 1.33 g (2.25 mmol) of compound 2-4 and 20 ml of dehydrated dichlorobenzene were added to a degassed 50 mL two-necked flask and dissolved. 9 ml (9 mmol) of 1 M boron tribromide solution was added dropwise, stirred directly for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. After that, ice bath was added to 0°C, 2.35 ml (13.5 mmol) of diisopropylethylamine was added dropwise, stirred directly for 5 minutes, and then stirred at room temperature for 30 minutes. After that, the temperature was raised to 120°C and heated and stirred overnight. After cooling to room temperature, short column treatment was performed with silica gel. The obtained residue was refined by silica gel column chromatography and recrystallization to obtain 417 mg (0.70 mmol) of compound BD3 with a yield of 31%.

[0124] By measurement by FD-MS (field desorption mass spectrometry), a mass spectrum of m / Z=598 of the obtained compound BD3 was observed, and thus the compound BD3 was identified as a compound of the aforementioned structure.

[0125] [Example 4] Synthesis of boron-containing compound BD4

[0126] (i) Synthesis of Compound 3-2

[0127]

Chemical formula 15

[0128]

[0129] In a 1000mL four-necked flask with a nitrogen inlet tube, 2.00g (10mmol) of compound 3-1, 2.70g (10mmol) of 1,3-dibromo-5-chlorobenzene, 2.88g (30mmol) of sodium tert-butoxide, and 1000mL of dehydrated toluene were added, and nitrogen was bubbled for one hour. Then, 366mg (0.4mmol) of tris(dibenzylideneacetone)dipalladium (0) and 95mg (0.32mmol) of JohnPhos were added, and refluxed and stirred overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The reaction mixture was extracted with toluene, washed with brine, and MgSO 4 After drying, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography to obtain 988 mg (3.2 mmol) of compound 3-2 with a yield of 32%.

[0130] (ii) Synthesis of Compound 3-3

[0131]

Chemical formula 16

[0132]

[0133] In a 50mL four-necked flask equipped with a stirrer, 988mg (3.2mmol) of compound 3-2, 1.34g (7.7mmol) of 4-bromofluorobenzene, 1.72g (17.9mmol) of sodium tert-butoxide, and 30ml of dehydrated toluene were added, and nitrogen was bubbled for one hour. 117mg (0.13mmol) of tris (dibenzylideneacetone) dipalladium (0) and 78mg (0.26mmol) of JohnPhos were added thereto, and refluxed and stirred overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The insoluble matter was filtered through diatomaceous earth filtration, and the filtrate was concentrated. The obtained residue was purified by silica gel column chromatography to obtain 1.54g (3.1mmol) of compound 3-3 with a yield of 97%.

[0134] (iii) Synthesis of Compound 3-4

[0135]

Chemical formula 17

[0136]

[0137] In a 50mL four-necked flask equipped with a stirrer, 1.54g (3.1mmol) of compound 3-3, 630mg (3.7mmol) of diphenylamine, 890mg (9.3mmol) of sodium tert-butoxide, and 30ml of dehydrated toluene were added, and nitrogen was bubbled for one hour. 117mg (0.13mmol) of tris (dibenzylideneacetone) dipalladium (0) and 75mg (0.26mmol) of tri-tert-butylphosphonium tetrafluoroborate were added thereto, and refluxed and stirred overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The insoluble matter was filtered through diatomaceous earth filtration, and the filtrate was concentrated. The obtained residue was refined by silica gel column chromatography to obtain 1.85g (2.9mmol) of compound 3-4 with a yield of 95%.

[0138] (iv) Synthesis of Compound BD4 (boron-containing compound)

[0139]

Chemical formula 18

[0140]

[0141] In a degassed 50mL two-necked flask, 1.42g (2.25mmol) of compound 3-4 and 20ml of dehydrated dichlorobenzene were added and dissolved. 9ml (9mmol) of 1M boron tribromide solution was added dropwise, stirred directly for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. After that, ice bath was added to 0°C, 2.35ml (13.5mmol) of diisopropylethylamine was added dropwise, stirred directly for 5 minutes, and then stirred at room temperature for 30 minutes. After that, the temperature was raised to 120°C and heated and stirred overnight. After cooling to room temperature, short column treatment was performed with silica gel. The obtained residue was refined by silica gel column chromatography and recrystallization to obtain 502mg (0.79mmol) of compound BD4 with a yield of 35%.

[0142] By measurement by FD-MS (field desorption mass spectrometry), a mass spectrum of m / Z=637 of the obtained compound BD4 was observed, and thus compound BD4 was identified as a compound of the aforementioned structure.

[0143] [Example 5] Synthesis of boron-containing compound BD5

[0144] (i) Synthesis of Compound 4-2

[0145]

Chemical formula 19

[0146]

[0147] In a 300mL four-necked flask equipped with a stirrer, 1.86g (20mmol) of compound 4-1, 4.59g (24mmol) of 1-bromo-3-chlorobenzene, 11.53g (120mmol) of sodium tert-butoxide, and 200ml of dehydrated toluene were added, and nitrogen was bubbled for one hour. 732mg (0.8mmol) of tris (dibenzylideneacetone) dipalladium (0) and 477mg (1.6mmol) of JohnPhos were added thereto, and refluxed and stirred overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The insoluble matter was filtered through diatomaceous earth filtration, and the filtrate was concentrated. The obtained residue was purified by silica gel column chromatography to obtain 4.27g (13.6mmol) of compound 4-2 with a yield of 68%.

[0148] (ii) Synthesis of Compound 4-3

[0149]

Chemical formula 20

[0150]

[0151] In a 200mL four-necked flask with a stirrer, 4.27g (13.6mmol) of compound 4-2, 4.21g (32.6mmol) of 2,4-difluoroaniline, 7.32g (76.2mmol) of sodium tert-butoxide, 140ml of dehydrated toluene were added, and nitrogen was bubbled for one hour. 498mg (0.54mmol) of tris (dibenzylideneacetone) dipalladium (0) and 313mg (1.08mmol) of tri-tert-butylphosphonium tetrafluoroborate were added thereto, and refluxed and stirred overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The insoluble matter was filtered through diatomaceous earth filtration, and the filtrate was concentrated. The obtained residue was purified by silica gel column chromatography to obtain 5.16g (10.3mmol) of compound 4-3 with a yield of 76%.

[0152] (iii) Synthesis of Compound 4-4

[0153]

Chemical formula 21

[0154]

[0155] In a 1000mL four-necked flask with a nitrogen inlet tube, 5.00g (10mmol) of compound 4-3, 2.50g (10mmol) of 3,5-dibromotoluene, 2.88g (30mmol) of sodium tert-butoxide, and 1000mL of dehydrated toluene were added, and nitrogen was bubbled for one hour. Then, 230mg (0.4mmol) of bis(dibenzylideneacetone)palladium (0) and 93mg (0.32mmol) of tri-tert-butylphosphonium tetrafluoroborate were added, and refluxed and stirred overnight. The disappearance of the raw material was confirmed by TLC for the reaction mixture. The reaction mixture was extracted with toluene, washed with brine, and MgSO 4 After drying, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography to obtain 2.23 g (3.8 mmol) of compound 4-4 with a yield of 38%.

[0156] (iv) Synthesis of Compound BD5 (boron-containing compound)

[0157]

Chemical formula 22

[0158]

[0159] 1.32 g (2.25 mmol) of compound 4-4 and 20 ml of dehydrated dichlorobenzene were added to a degassed 50 mL two-necked flask and dissolved. 9 ml (9 mmol) of 1 M boron tribromide solution was added dropwise, stirred directly for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. After that, ice bath was added to 0°C, 2.35 ml (13.5 mmol) of diisopropylethylamine was added dropwise, stirred directly for 5 minutes, and then stirred at room temperature for 30 minutes. After that, the temperature was raised to 120°C and heated and stirred overnight. After cooling to room temperature, short column treatment was performed with silica gel. The obtained residue was refined by silica gel column chromatography and recrystallization to obtain 442 mg (0.74 mmol) of compound BD5 with a yield of 33%.

[0160] By measurement by FD-MS (field desorption mass spectrometry), a mass spectrum of m / Z=595 of the obtained compound BD5 was observed, and thus compound BD5 was identified as a compound of the aforementioned structure.

[0161] [Production and evaluation of components]

[0162] [Example 6]

[0163] An ITO film having a thickness of 180 nm produced by sputtering was polished to 150 nm, and the resulting glass substrate of 26 mm×28 mm×0.7 mm (manufactured by OptoScience Co., Ltd.) was used as a transparent supporting substrate.

[0164] The transparent supporting substrate was fixed on a substrate holder of a commercially available vapor deposition device (manufactured by Showa Vacuum Co., Ltd.), and a molybdenum vapor deposition boat with HATCN (HIM; hole injection material), a molybdenum vapor deposition boat with α-NPD (HTM; hole transport material), a molybdenum vapor deposition boat with EBL (electron blocking material), a molybdenum vapor deposition boat with BH1 (main body), a molybdenum vapor deposition boat with compound BD1 synthesized in Example 1, a molybdenum vapor deposition boat with HBL (hole blocking material), a molybdenum vapor deposition boat with NBPhen (ETM; electron transport material), a molybdenum vapor deposition boat with LiF, and a tungsten vapor deposition boat with aluminum were installed. The structural formula of each material is shown below.

[0165]

Chemical formula 23

[0166]

[0167] The following layers were formed in sequence on the ITO film of the transparent supporting substrate. The vacuum chamber was depressurized to 5×10 -4 Pa, firstly, the evaporation boat with HIM added was heated, and evaporation was performed to a film thickness of 5 nm to form a hole injection layer 2. Next, the evaporation boat with HTM added was heated, and evaporation was performed to a film thickness of 105 nm to form a hole transport layer 3. Further, the evaporation boat with EBL added was heated, and evaporation was performed to a film thickness of 20 nm to form an electron blocking layer 4.

[0168] Next, the deposition boat containing BH1 and the deposition boat containing compound BD1 were heated simultaneously, and deposition was performed to a film thickness of 25 nm to form the light emitting layer 5. The deposition rate was adjusted so that the weight ratio of BH1 to compound BD1 was about 97:3.

[0169] Next, the deposition boat containing HBL was heated and deposition was performed to a thickness of 20 nm to form the hole blocking layer 6. Next, ETM was added to the deposition boat and deposition was performed to a thickness of 10 nm to form the electron transport layer 7.

[0170] The deposition rate of each layer is 0.01 to 2 nm / sec.

[0171] After that, the evaporation boat containing LiF as the material of the electron injection layer 8 is heated and evaporated at a evaporation rate of 0.01 to 0.1 nm / sec to a film thickness of 1 nm. Next, the evaporation boat containing aluminum is heated and heated at a evaporation rate of 0.01 to 2 nm / sec to a film thickness of 100 nm, thereby forming a cathode 9 and obtaining an organic EL element.

[0172] When an ITO electrode is used as the anode 1 and a LiF / aluminum electrode is used as the cathode 9 and a DC voltage is applied, blue light emission is obtained.

[0173] When the device was driven with a constant current at an initial brightness of 1000 nit, the time until the brightness reached 95% was measured.

[0174] [Example 7]

[0175] A device was produced in the same manner as in Example 6, except that the compound BD2 synthesized in Example 2 was used instead of the compound BD1.

[0176] [Example 8]

[0177] A device was produced in the same manner as in Example 6 except that the compound BD3 synthesized in Example 3 was used instead of the compound BD1.

[0178] [Example 9]

[0179] A device was produced in the same manner as in Example 6, except that the compound BD4 synthesized in Example 4 was used instead of the compound BD1.

[0180] [Example 10]

[0181] A device was produced in the same manner as in Example 6 except that the compound BD5 synthesized in Example 5 was used instead of the compound BD1.

[0182] [Comparative Example 1]

[0183] A device was produced in the same manner as in Example 6 except that the compound represented by the following structural formula was used instead of compound BD1.

[0184]

Chemical formula 24

[0185]

[0186] When an ITO electrode is used as the anode 1 and a LiF / aluminum electrode is used as the cathode 9 and a DC voltage is applied, blue light emission is obtained.

[0187] When the device was driven with a constant current at an initial brightness of 1000 nit, the time until the brightness reached 95% was measured.

[0188]

Table 1

[0189]

[0190] It is found that the compound of the present invention can maintain blue light emission with a short wavelength and a long lifetime compared to the conventional technology.

Claims

1. A boron-containing compound having a skeleton represented by the following general formula (1), 【Chemical formula 1】 X is -BAr-, -CR 1 R 2 -、-NAr-、-O-、-SiR 3 R 4 -or-S-, where Ar is an aryl group, R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group, or an aryl group having 5 to 30 nuclei, 1 and R 2 , or R 3 and R 4 can be connected to each other to form a ring; o is 1 or 2; C 1 and C 2 is a carbon atom or an aromatic carbon atom, C 1 and C 2 can form a ring together with the carbon atom adjacent to X; Y is a fluoro group; 0≤m+n≤10, wherein m and n are integers of 0 to 5; D 1 and D 2 are each independently a carbon atom or a nitrogen atom; Z is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a fluoro group, or an amino group.

2. The boron-containing compound according to claim 1, wherein in the general formula (1), D 1 and D 2 are all carbon atoms; Y is a fluorine group; 1≤m+n≤10, wherein, m and n are integers from 0 to 5; Z is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a fluoro group, or an amino group.

3. The boron-containing compound according to claim 1, wherein in the general formula (1), D 1 and D 2 At least one of them is a nitrogen atom; Y is a fluorine group; 0≤m+n≤10, wherein, m and n are integers of 0 to 5; Z is a hydrogen atom. 4 . An organic EL element comprising the boron-containing compound according to claim 1 .

5. An organic EL element comprising the boron-containing compound according to any one of claims 1 to 3 in a light-emitting wavelength band. 6 . An organic EL device comprising the boron-containing compound according to claim 1 in a light-emitting layer.

7. An organic EL device comprising 0.1 to 20 wt% of the boron-containing compound according to any one of claims 1 to 3 in a light-emitting layer.

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