Boron-containing compound and organic el element

Abstract

To provide a boron-containing compound as an emission material for a blue element, and an organic EL element.SOLUTION: A boron-containing compound has the structure of formula (1): X is -BAr-, -CR1R2- (R1 and R2 are linked to each other, forming a ring, or each independently represent H, C1-6 alkyl or alkoxy, amino or aryl with 5-30 atoms), -NAr-, -O-, -SiR3R4- (R3 and R4 are linked to each other, forming a ring, or each independently represent H, C1-6 alkyl or alkoxy, amino or aryl with 5-30 atoms) or -S-. o is 1 or 2. C1 and C2 are C and may each form a ring together with C adjacent to X. Y is F. 0≤m+n≤10 (m and n are an integer of 0-5). D1 and D2 independently represent C or N. Z is H, C1-6 alkyl or alkoxy, F, or amino).SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In order to improve the practical use of organic electroluminescence (EL) devices, it is necessary to increase the luminous efficiency. There are two types of excitons formed by organic compounds: fluorescent emission from singlet excitons (S1) and phosphorescent emission from triplet excitons (T1). The statistical generation ratio of these in a device is E S1 :E T1 Since the ratio is 1:3, the internal quantum efficiency of organic EL elements that use fluorescent emission is limited to 25%.

[0003] Recently, organic electroluminescence (EL) elements have been developed that use thermally activated delayed fluorescence (TADF) materials that can convert part of the triplet excited state into light emission, upconverting the lowest triplet excited state (T1) to the lowest singlet excited state (S1). TADF materials have an energy difference ΔE ST The energy (E T1 ) can also contribute to fluorescent emission, resulting in higher luminous efficiency than conventional fluorescent materials.

[0004] Research and development of TADF materials, which are expected to have such high luminous efficiency, is being actively conducted, but only a few of the TADF materials developed so far show good blue luminescence.

[0005] The luminous efficiency of the emitting layer can be improved not only by improving the luminescent material, but also by using a host material that traps energy in the molecules of the luminescent material. For example, when the luminescent material is a blue-emitting dopant, the excitation energy level of the dopant itself is high, so the host material to be combined with it is required to have an even higher excitation energy level. In the luminescent layer formed by combining such a dopant and a host material, excitons can be efficiently generated from the charges injected into the host, and highly efficient luminescence can be obtained.

[0006] As a dopant and host material for the light-emitting layer, for example, a benzoquinolizinoacridine derivative that serves as a dopant for the light-emitting layer of a blue light-emitting device or a hole transport material for the hole transport layer has been reported in Patent Document 1. There are also reports of a nitrogen-containing heterocyclic compound being used as a host for the light-emitting layer, hole transport layer, or hole injection layer (Patent Document 2).

[0007] There has been a report of an example in which an azaborine derivative having nitrogen and boron atoms at the 1,4-positions is used as a host for a phosphorescent OLED (Patent Document 3). Focusing on the charge transport property and high luminescence property derived from boron and the unshared electron pairs of oxygen, nitrogen or sulfur atoms, it has been reported that conjugated boron compounds having both of these atoms contribute to charge transport property and high luminescence rate, and can provide organic EL devices with excellent luminous efficiency and stability at high temperatures (Patent Documents 4, 5, 6).

[0008] In addition to azaborine derivatives, which are conjugated boron compounds having oxygen, nitrogen or sulfur atoms, polycyclic heterocyclic aromatic compounds have been reported in which the boron atom of a conjugated boron compound is replaced with a phosphorus atom, a phosphoryl group, a thiophosphoryl group, a silicon atom, a bismuth atom or a germanium atom (Patent Document 7).

[0009] Patent Document 8 reports that a light-emitting material that has a donor site and an acceptor site in the molecule, emits TADF, and enables proton transfer within the molecule has a high enough quantum efficiency for practical use and is suitable as a light-emitting material for organic EL devices.

[0010] Other light-emitting materials that have been reported for use in organic EL devices include a blue-emitting polycyclic aromatic compound having a boron atom and a nitrogen atom and / or an oxygen atom (Patent Document 9), a compound in which a part of the coronene skeleton is substituted with a boron atom and a sulfur atom (Patent Document 10), a heterocyclic compound having one boron atom and two oxygen atoms or nitrogen atoms facing it (Patent Document 11), and a heterocyclic compound having one nitrogen atom and two boron atoms facing it (Patent Document 12). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Special Publication No. 2009-512628 [Patent Document 2] Special Publication No. 2012-507507 [Patent Document 3] International Publication No. 2011 / 143563 [Patent Document 4] International Publication No. 2017 / 18326 [Patent Document 5] JP 2017-126606 A [Patent Document 6] International Publication No. 2017 / 195669 [Patent Document 7] JP 2018-43984 A [Patent Document 8] International Publication No. 2018 / 159662 [Patent Document 9] JP 2020-123721 A [Patent Document 10] China Patent Application Publication No. 113801151 [Patent Document 11] International Publication No. 2020 / 108899 [Patent Document 12] Special Publication No. 2022-527591 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a novel boron-containing compound that emits blue light, and an organic EL device that contains the boron-containing compound and has both high luminous efficiency and long life durability. [Means for solving the problem]

[0013] The boron-containing compound of the present invention has a skeleton represented by the following general formula (1). [ka]

[0014] In the general formula (1), X is -BAr- (Ar is an aryl group), -CR 1 R 2 -(R 1 and R 2 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 ring atoms. 1 and R 2 may be linked together to form a ring.), -NAr- (Ar is an aryl group), -O-, -SiR 3 R 4 -(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 ring atoms. 3 and R 4 may be linked together to form a ring; or -S-, o is 1 or 2, and C 1 and C 2 is a carbon atom or an aryl carbon atom, C 1 and C 2 may each form a ring together with X and the adjacent carbon atom, Y is a fluoro group, and 0≦m+n≦10 (m and n are integers of 0 to 5), D 1 and D. 2are each 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.

[0015] In the general formula (1), D 1 and D. 2 are all 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.

[0016] In the general formula (1), D 1 and D. 2 It is preferable that at least one of the following is a nitrogen atom, Y is a fluoro group, 0≦m+n≦10 (m and n are integers of 0 to 5), and Z is a hydrogen atom.

[0017] The organic EL device of the present invention contains the above-mentioned boron-containing compound. The organic EL device of the present invention contains the above boron-containing compound in the light-emitting band. The organic EL device of the present invention contains the above boron-containing compound in the light-emitting layer. The organic EL device of the present invention contains the above boron-containing compound in an amount of 0.1 to 20 wt % in the light-emitting layer. Effect of the Invention

[0018] 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 large HOMO-LUMO gap and a high triplet energy (E T1 In addition, since the energy difference between the triplet excited state (T1) and the singlet excited state (S1) is small and the compound exhibits thermally activated delayed fluorescence (TADF), it is useful as a light-emitting material for organic electroluminescence devices.

[0019] An organic EL device using the above boron-containing compound as a blue dopant in the light-emitting layer has significantly improved luminous efficiency and life span compared to conventional blue devices. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view showing an organic EL element according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention will be described in detail below. The boron-containing compound of the present invention has a skeleton represented by the following general formula (1). [ka]

[0022] In the general formula (1), X is -BAr- (Ar is an aryl group), -CR 1 R 2 -(R 1 and R 2 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 ring atoms. 1 and R 2 may be linked together to form a ring.), -NAr- (Ar is an aryl group), -O-, -SiR 3 R 4 -(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 ring atoms. 3 and R 4 may be linked together to form a ring. ) or -S-. o is 1 or 2.

[0023] X is -BAr-, -NAr-, -CR 1 R 2 -, -SiR 3 R 4 -, an ether bond (-O-), or a sulfide bond (-S-). In the -NAr- and -BAr-, Ar is an aryl group having 5 to 30 ring atoms. The aryl group having 5 to 30 ring atoms is represented by R 1 ~R 4 is the same as the specific example when is an aryl group having 5 to 30 nuclear atoms. Specific examples of the -NAr- include a phenylamino group, a naphthylamino group, and a pyridinylamino group. Specific examples of the -BAr- include a phenylboranyl group, a naphthylboranyl group, and a pyridinylboranyl group.

[0024] -CR 1 R 2 -Medium, R 1 and R 2 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 ring atoms. -SiR 3 R 4 -Medium, 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 ring atoms.

[0025] 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, s-butyl, t-butyl, n-pentyl, neopentyl, isopentyl, s-pentyl, 3-pentyl, t-pentyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, and 2,3-dimethylbutyl groups.

[0026] Examples of the alkoxy group having 1 to 6 carbon atoms include linear or branched alkyl groups, specifically, methoxy, ethoxy, propyloxy, isopropyloxy, n-butoxy, isobutoxy, s-butoxy, t-butoxy, n-pentoxy, neopentoxy, isopentoxy, s-pentoxy, 3-pentoxy, t-pentoxy, n-hexoxy, 2-methylpentoxy, 3-methylpentoxy, 2,2-dimethylbutoxy, and 2,3-dimethylbutoxy groups.

[0027] The aryl group having 5 to 30 ring atoms includes a monocyclic or condensed polycyclic aromatic hydrocarbon group or a heteroaromatic compound group which may have a substituent. Specific examples include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a p-methoxyphenyl group, a pt-butylphenyl group, a p-tolyl group, a m-tolyl group, an o-tolyl group, a pentafluorophenyl group, a phenanthryl group, a pyrenyl group, a fluorenyl group, a fluoranthenyl group, a pyridyl group, a quinoxanyl group, a pyrrole group, an indolyl group, a carbazolyl group, an imidazolyl group, a benzimidazolyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a thiophenyl group, a benzothiophenyl group, a dibenzothiophenyl group, a benzoxazolyl group, and a benzothioxazolyl group.

[0028] -CR 1 R 2 -and-SiR 3 R 4 - In R 1 and R 2 , or R 3 and R 4 may be linked to each other to form a 4- to 8-membered ring, preferably a 5- or 6-membered ring. Specific examples of the 5- or 6-membered ring include a cyclopentyl ring and a cyclohexyl group. o represents the number of X. o is an integer of 1 or 2.

[0029] C 1 and C 2is a carbon atom or an aryl carbon atom. Specifically, the aryl carbon atom is a carbon atom having an aryl group having 6 to 10 carbon atoms. The aryl group is preferably a phenyl group. C 1 and C 2 may each form a ring together with X and the carbon atom adjacent thereto, for example, may form a ring as shown in the following structural formula. [ka]

[0030] Y is a fluoro group. m+n represents the number of fluoro groups. m+n is an integer of 0 to 10, and m and n are each an integer of 0 to 5. It is preferable that 1≦m+n≦10 and m and n are each an integer of 0 to 5.

[0031] D 1 and D. 2 are each independently a carbon atom or a nitrogen atom. 1 and D. 2 Either one of them may be a carbon atom or a nitrogen atom, or both of them may be carbon atoms or nitrogen atoms. 1 and D. 2 The carbon atom between is a nitrogen atom, and D 1 and D. 2 When either or both of the above are nitrogen atoms or carbon atoms, blue light emission cannot be obtained.

[0032] 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. The alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms are represented by R 1 ~R 4 is the same as the specific examples when is an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms.

[0033] Specifically, the boron-containing compound of the present invention is a compound having the following structural formula: [ka]

[0034] 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 many of them can function as dyes. However, when the π-conjugated system is extended, the HOMO increases and the LUMO decreases, resulting in a large gap between the HOMO and LUMO (band gap E g On the other hand, the boron-containing compound of the present invention, as shown in general formula (1), has a boron atom in an aromatic ring and a nitrogen atom facing it, and therefore has low aromaticity, and even if the conjugated system is expanded, the decrease in the HOMO-LUMO gap is suppressed.

[0035] The boron-containing compound of the present invention has a high triplet excitation energy (E T In addition, in the boron-containing compound, the triplet excited state (E T ) are localized, and the exchange interaction between the two orbitals becomes small, resulting in a singlet excited state (E S ) and triplet excited states (E T ) and the energy gap (ΔE ST ) and exhibits thermally activated delayed fluorescence (TADF).

[0036] The boron-containing compound of the present invention has a bulky structure in which a ring structure containing boron atoms and nitrogen atoms is surrounded by a plurality of aromatic rings, and therefore has a structure that is relatively rigid and in which rotation and bending are moderately suppressed. By having such a structure, the boron-containing compound of the present invention has very small vibration energy even in the S1-S0 transition (transition from excited singlet state (S1) to ground state (S0)) that accompanies torsional vibration of the entire molecule, and can obtain an emission spectrum with an extremely narrow half-width, i.e., high color purity. As reported for a known organic blue-emitting material (DABNA-1), it is believed that the S1-S0 transition in the boron-containing compound of the present invention is not accompanied by stretching vibration due to the multiple resonance effect between boron and nitrogen atoms.

[0037] Among the boron-containing compounds of the present invention, in FS2Me, the excitation peak to the excited state of S1 (HOMO → LUMO) is 3.09 eV and the oscillator strength (f) of the S1-S0 transition is 0.1473, while in FD2A, S1 is 3.11 eV and the oscillator strength (f) of the S1-S0 transition is 0.1374, indicating that a highly pure blue emission spectrum can be obtained.

[0038] In the present invention, the band gap E g In addition to adjusting the singlet-triplet energy gap (ΔE ST ) as small as possible, and once in the triplet excited state (E T ) is transferred back to the singlet excited state (E S ), making it possible to extract blue fluorescence with high efficiency.

[0039] 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 below. [ka]

[0040] In a four-neck flask, 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 are added under a nitrogen atmosphere, and 230mg (0.4mmol) of bis(dibenzylideneacetone)palladium(0) and 93mg (0.32mmol) of tri-tert-butylphosphonium tetrafluoroborate are added and refluxed overnight. The reaction mixture is purified to obtain 2.20g (4.5mmol) of compound 1-2 in a yield of 45%. Next, 1.10 g (2.25 mmol) of compound 1-2 and 20 ml of dehydrated dichlorobenzene are placed in a two-neck flask, and 9 ml (9 mmol) of 1 M boron tribromide solution is added dropwise, followed by stirring for 2 hours at a bath temperature of 180°C. Then, 2.35 ml (13.5 mmol) of diisopropylethylamine is added dropwise while the reaction mixture is being stirred, and the mixture is stirred for 5 minutes and then stirred at room temperature for 30 minutes. The temperature is raised to 120°C and the mixture is heated and stirred overnight to terminate the reaction. After purification, 290 mg (0.58 mmol) of compound BD1 is obtained with a yield of 26%. Compound BD1 is identified by field desorption mass spectrometry (FD-MS). The method for producing the boron-containing compound of the present invention is not limited to the above, but can be produced by various known methods.

[0041] The organic EL device of the present invention is formed using the boron-containing compound. The boron-containing compound is included in the emission band of the organic EL device. The emission band is a region where holes and electrons recombine to emit light, and in many cases, the emission band corresponds to the light-emitting layer 5.

[0042] An organic EL element has a structure in which one or more organic layers are laminated between electrodes, and examples of such elements include "anode 1 / hole injection layer 2 / hole transport layer 3 / light emitting layer 5 / electron transport layer 7 / electron injection layer 8 / cathode 9", "anode 1 / hole transport layer 3 / light emitting layer 5 / electron transport layer 7 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 ...hole transport layer 3 / light emitting layer 5 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 / hole transport layer 3 / light emitting layer 5 / electron injection layer 8 / cathode 9", and "anode 1 / hole injection layer 2 / hole transport layer 3 / light emitting layer 5 The configurations are "anode 1 / light-emitting layer 5 / electron transport layer 7 / electron injection layer 8 / cathode 9", "anode 1 / hole transport layer 3 / light-emitting layer 5 / electron injection layer 8 / cathode 9", "anode 1 / hole transport layer 3 / light-emitting layer 5 / electron transport layer 7 / cathode 9", "anode 1 / hole transport layer 3 / light-emitting layer 5 / electron transport layer 7 / cathode 9", "anode 1 / hole injection layer 2 / light-emitting layer 5 / electron injection layer 8 / cathode 9", "anode 1 / hole injection layer 2 / light-emitting layer 5 / electron transport layer 7 / cathode 9", "anode 1 / light-emitting layer 5 / electron transport layer 7 / cathode 9", and "anode 1 / light-emitting layer 5 / electron injection layer 8 / cathode 9". In the embodiment of the present invention, as shown in FIG. 1, the structure in which the electron barrier layer 4 and the hole barrier layer 6 are added to the above configuration and "anode 1 / hole injection layer 2 / hole transport layer 3 / electron barrier layer 4 / light-emitting layer 5 / hole barrier layer 6 / electron transport layer 7 / electron injection layer 8 / cathode 9" are laminated in this order. The organic layer refers to layers 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 light emitting layer 5, the hole blocking layer 6, the electron transport layer 7, the electron injection layer 8, and the like.

[0043] The substrate is transparent, smooth, and has a total light transmittance of at least 70%. Specifically, a flexible transparent substrate such as a glass substrate several micrometers thick or a special transparent plastic is used.

[0044] Thin films formed on a substrate, such as an anode 1, a hole injection layer 2, a hole transport layer 3, an electron blocking layer 4, an emitting layer 5, a hole blocking layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9, are laminated by a vacuum deposition method or a coating method. When using a vacuum deposition method, it is usually -3The deposition is performed by heating the deposition material in an atmosphere reduced in pressure to below Pa. The thickness of each layer varies depending on the type of layer and the material used, but typically the anode 1 and cathode 9 are about 100 nm, and other organic layers including the light-emitting layer 5 are less than 50 nm.

[0045] A material with a large work function and a total light transmittance of typically 80% or more is used for the anode 1. Specifically, in order to transmit the light emitted from the anode 1, transparent conductive ceramics such as indium tin oxide (ITO) and zinc oxide (ZnO), transparent conductive polymers such as polythiophene-polystyrene sulfonate (PEDOT-PSS) and polyaniline, and other transparent conductive materials are used.

[0046] In order to efficiently transport holes from the anode 1 to the light-emitting layer, a hole injection layer 2 and a hole transport layer 3 are provided between the anode and the light-emitting layer 5 . Examples of hole injection materials for forming the hole injection layer 2 include poly(arylene ether ketone)-containing triphenylamine (KLHIP:PPBI), 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HATCN), and PEDOT-PSS. The hole injection layer 2 made of these materials is also called a polymer buffer layer, and has the effect of lowering the driving voltage of the organic EL element.

[0047] The hole transport layer 3 is provided between the anode 1 and the light emitting layer 5, and is a layer for efficiently transporting holes from the anode 1 to the light emitting layer. As the hole transport material, one having a small ionization potential, that is, one in which electrons are easily excited from the HOMO and holes are easily generated, is used. For example, poly(9,9-dioctylfluorene-alt-N-(4-butylphenyl)diphenylamine) (TFB), 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (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''-tris[phenyl(m-tolyl)amino]triphenylamine).

[0048] For the light-emitting layer 5, like other light-emitting layers used in organic EL devices, it is preferable to use a light-emitting material consisting of a dopant and a host. As the dopant, a boron-containing compound represented by the general formula of the present invention is used. The amount of the dopant added is preferably 0.1 to 20 wt % based on the total amount of the dopant and the host. As the host, a wide variety of known materials can be used as long as they minimize the charge injection barrier from the hole transport layer 3 or the electron transport layer 7, confine the charge in the light emitting layer 5, and prevent quenching of the light emitting excitons. For example, an anthracene derivative having the following structural formula can be used as the host.

[0049] [ka]

[0050] [ka]

[0051] The amount of the host added is preferably 50 to 99.9 wt %, more preferably 80 to 95 wt %, of the entire material for the light emitting layer 5 .

[0052] An electron blocking layer 4 may be provided between the light emitting layer 5 and the hole transport layer 3 as needed. By providing the electron blocking layer 4, electrons can be confined within the light emitting layer, increasing the probability of charge recombination in the light emitting layer and improving the light emitting efficiency. As the electron blocking material forming the electron blocking layer 4, an amine derivative such as bis(biphenyl-4-yl)(3'-(9H-carbazol-9-yl)biphenyl-4-yl)amine is used.

[0053] 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 electron transport materials that form 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-hydroxyquinolinolatolithium (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-biphenylyl)-5-(pt-butylphenyl)-2-pyrimidine (B5PyPPm), and 2-(4-biphenylyl)-5-(pt-butylphenyl)-2-pyrimidine (B6PyPPm). )-1,3,4-oxadiazole (tBu-PBD), 1,3-bis[5-(4-t-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (OXD-7), 3-(biphenyl-4-yl)-5-(4-t-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ), bathocuproine (BCP), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) and 3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ). Among these, a mixed layer of DPB and Liq is preferred.

[0054] The hole blocking layer 6 is a layer for confining holes within the light emitting layer 5 to increase the probability of charge recombination in the light emitting layer 5 and improve the light emitting efficiency. As a hole blocking material for forming the hole blocking layer 6, benzothiophene-triphenyltriazine (DBT-TRZ) and 1-(3'-(4-dibenzofuran-4-yl)biphenyl-3-yl)-3,5-diphenyltriazine, etc. are used. The thickness of the hole blocking layer 6 and the electron transport layer 7 is usually 3 to 50 nm, and can be appropriately changed according to the intended design.

[0055] Examples of electron injection materials that form the electron injection layer 8 include lithium fluoride (LiF) and 2-hydroxy-(2,2')-bipyridinyl-6-yl-phenolatolithium (Libpp).

[0056] The cathode 9 is made of a material that has a low work function (4 eV or less) and is chemically stable. Specifically, cathode materials such as Al, alloys of Al and alkali metals such as AlLi, AlCa alloys, and MgAg alloys are used. These cathode materials are formed into films by, for example, resistance heating deposition, electron beam deposition, sputtering, or ion plating. EXAMPLES

[0057] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples. [Synthesis of boron-containing compounds] [Example 1] Synthesis of boron-containing compound BD1 (i) Synthesis of Compound 1-2 [ka] Compound 1-1 4.13g (10mmol), 4,6-dibromopyrimidine 2.38g (10mmol), sodium-tert-butoxide 2.88g (30mmol), and dehydrated toluene 1000mL were added to a 1000mL four-neck flask equipped with a nitrogen inlet tube, and nitrogen was bubbled for 1 hour. Then, bis(dibenzylideneacetone)palladium(0) 230mg (0.4mmol) and tri-tert-butylphosphonium tetrafluoroborate 93mg (0.32mmol) were added and refluxed overnight. The reaction mixture was confirmed to have disappeared by TLC. The reaction mixture was extracted with toluene, washed with brine, dried over MgSO4, and the solvent was distilled off. The resulting residue was purified by silica gel column chromatography to obtain compound 1-2 2.20g (4.5mmol) in a yield of 45%.

[0058] (ii) Synthesis of compound BD1 (boron-containing compound) [ka] Compound 1-2 (1.10 g, 2.25 mmol) and dehydrated dichlorobenzene (20 ml) were added to a degassed 50 mL two-neck flask and dissolved. 1M boron tribromide solution (9 ml, 9 mmol) was added dropwise and stirred for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. Then, the mixture was placed in an ice bath at 0°C, diisopropylethylamine (2.35 ml, 13.5 mmol) was added dropwise, stirred for 5 minutes, and then stirred at room temperature for 30 minutes. Then, the mixture was heated to 120°C and stirred overnight. After cooling to room temperature, a short column was performed with silica gel. The resulting residue was purified by silica gel column chromatography and recrystallization to obtain compound BD1 (290 mg, 0.58 mmol) in a yield of 26%. The obtained compound BD1 was observed to have a mass spectrum of m / Z=496 by FD-MS (field desorption mass spectrometry), and thus the compound BD1 was identified as the compound having the structure described above.

[0059] [Example 2] Synthesis of boron-containing compound BD2 (i) Synthesis of Compound 2-2 [ka] Compound 2-1 (7.76g, 20.0mmol), aniline (4.48g, 48mmol), sodium tert-butoxide (10.76g, 112mmol), and dehydrated toluene (200ml) were added to a 300mL four-neck flask equipped with a stirrer and nitrogen was bubbled for 1 hour. Tris(dibenzylideneacetone)dipalladium(0) (740mg, 0.80mmol), (±)-BINAP (1.12g, 1.8mmol) were added thereto and refluxed overnight with stirring. The reaction mixture was confirmed to have disappeared by TLC. Insoluble matter was filtered off using Celite, and the filtrate was concentrated. The resulting residue was purified by silica gel column chromatography to obtain compound 2-2 (8.18g, 16.4mmol) in 82% yield.

[0060] (ii) Synthesis of Compound 2-3 [ka] Compound 2-2 4.99g (10mmol), 4,6-dibromopyrimidine 2.38g (10mmol), sodium-tert-butoxide 2.88g (30mmol), and dehydrated toluene 1000mL were added to a 1000mL four-neck flask equipped with a nitrogen inlet tube, and nitrogen was bubbled for 1 hour. Then, bis(dibenzylideneacetone)palladium(0) 230mg (0.4mmol) and tri-tert-butylphosphonium tetrafluoroborate 93mg (0.32mmol) were added and refluxed overnight. The reaction mixture was confirmed to have disappeared by TLC. The reaction mixture was extracted with toluene, washed with brine, and dried over MgSO4, after which the solvent was distilled off. The resulting residue was purified by silica gel column chromatography to obtain compound 2-3 2.41g (4.2mmol) in a yield of 42%.

[0061] (iii) Synthesis of compound BD2 (boron-containing compound) [ka] Compound 2-3 (1.29 g, 2.25 mmol) and dehydrated dichlorobenzene (20 ml) were added to a degassed 50 mL two-neck flask and dissolved. 1M boron tribromide solution (9 ml, 9 mmol) was added dropwise and stirred for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. Then, the mixture was placed in an ice bath at 0°C, diisopropylethylamine (2.35 ml, 13.5 mmol) was added dropwise, stirred for 5 minutes, and then stirred at room temperature for 30 minutes. Then, the mixture was heated to 120°C and stirred overnight. After cooling to room temperature, a short column was performed with silica gel. The resulting residue was purified by silica gel column chromatography and recrystallization to obtain compound BD2 (275 mg, 0.47 mmol) in a yield of 21%. The resulting compound BD2 was observed to have a mass spectrum of m / Z=582 by FD-MS (field desorption mass spectrometry), and thus the compound BD2 was identified as the compound having the structure described above.

[0062] [Example 3] Synthesis of boron-containing compound BD3 (i) Synthesis of Compound 2-4 [ka] Compound 2-2 4.99g (10mmol), 1,3-dibromo-5-fluorobenzene 2.54g (10mmol), sodium-tert-butoxide 2.88g (30mmol), and dehydrated toluene 1000mL were added to a 1000mL four-neck flask equipped with a nitrogen inlet tube, and nitrogen was bubbled for 1 hour. Then, bis(dibenzylideneacetone)palladium(0) 230mg (0.4mmol) and tri-tert-butylphosphonium tetrafluoroborate 93mg (0.32mmol) were added and refluxed overnight. The reaction mixture was confirmed to have disappeared by TLC. The reaction mixture was extracted with toluene, washed with brine, and dried over MgSO4, after which the solvent was distilled off. The resulting residue was purified by silica gel column chromatography to obtain compound 2-4 2.54g (4.3mmol) in a yield of 43%.

[0063] (ii) Synthesis of compound BD3 (boron-containing compound) [ka] Compound 2-4 (1.33 g, 2.25 mmol) and dehydrated dichlorobenzene (20 ml) were added to a degassed 50 mL two-neck flask and dissolved. 1M boron tribromide solution (9 ml, 9 mmol) was added dropwise and stirred for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. Then, the mixture was placed in an ice bath at 0°C, diisopropylethylamine (2.35 ml, 13.5 mmol) was added dropwise, stirred for 5 minutes, and then stirred at room temperature for 30 minutes. Then, the mixture was heated to 120°C and stirred overnight. After cooling to room temperature, a short column was performed with silica gel. The resulting residue was purified by silica gel column chromatography and recrystallization to obtain compound BD3 (417 mg, 0.70 mmol) in a yield of 31%. The resulting compound BD3 was observed to have a mass spectrum of m / Z=598 by FD-MS (field desorption mass spectrometry), and thus the compound BD3 was identified as the compound having the structure described above.

[0064] [Example 4] Synthesis of boron-containing compound BD4 (i) Synthesis of Compound 3-2 [ka] Compound 3-1 2.00g (10mmol), 1,3-dibromo-5-chlorobenzene 2.70g (10mmol), sodium-tert-butoxide 2.88g (30mmol), and dehydrated toluene 1000mL were added to a 1000mL four-neck flask equipped with a nitrogen inlet tube, and nitrogen was bubbled for 1 hour. Next, tris(dibenzylideneacetone)dipalladium(0) 366mg (0.4mmol) and JohnPhos 95mg (0.32mmol) were added and refluxed overnight. The reaction mixture was confirmed to have disappeared by TLC. The reaction mixture was extracted with toluene, washed with brine, and dried with MgSO4, after which the solvent was distilled off. The resulting residue was purified by silica gel column chromatography to obtain compound 3-2 988mg (3.2mmol) in a yield of 32%.

[0065] (ii) Synthesis of Compound 3-3 [ka] Compound 3-2 (988 mg, 3.2 mmol), 4-bromofluorobenzene (1.34 g, 7.7 mmol), sodium tert-butoxide (1.72 g, 17.9 mmol), and dehydrated toluene (30 ml) were added to a 50 mL four-necked flask equipped with a stirrer and nitrogen was bubbled for 1 hour. Tris(dibenzylideneacetone)dipalladium(0) (117 mg, 0.13 mmol), JohnPhos (78 mg, 0.26 mmol) were added thereto and refluxed overnight with stirring. The disappearance of the raw materials was confirmed by TLC in the reaction mixture. Insoluble matter was filtered off by celite filtration, and the filtrate was concentrated. The obtained residue was purified by silica gel column chromatography to obtain compound 3-3 (1.54 g, 3.1 mmol) in a yield of 97%.

[0066] (iii) Synthesis of Compound 3-4 [ka] 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 1 hour. Tris(dibenzylideneacetone)dipalladium(0) 117mg (0.13mmol) and tri-tert-butylphosphonium tetrafluoroborate 75mg (0.26mmol) were added thereto and stirred under reflux overnight. The disappearance of the raw materials was confirmed by TLC in the reaction mixture. Insoluble matter was filtered off by celite filtration, and the filtrate was concentrated. The obtained residue was purified by silica gel column chromatography to obtain 1.85g (2.9mmol) of compound 3-4 in a yield of 95%.

[0067] (iv) Synthesis of compound BD4 (boron-containing compound) [ka] Compound 3-4 (1.42g, 2.25mmol) and dehydrated dichlorobenzene (20ml) were added to a degassed 50mL two-neck flask and dissolved. 1M boron tribromide solution (9ml, 9mmol) was added dropwise and stirred for 5 minutes, then stirred at a bath temperature of 180°C for 2 hours. Then, the mixture was placed in an ice bath at 0°C, diisopropylethylamine (2.35ml, 13.5mmol) was added dropwise, stirred for 5 minutes, and then stirred at room temperature for 30 minutes. Then, the mixture was heated to 120°C and stirred overnight. After cooling to room temperature, a short column was performed with silica gel. The resulting residue was purified by silica gel column chromatography and recrystallization to obtain compound BD4 (502mg, 0.79mmol) in a yield of 35%. The resulting compound BD4 was observed to have a mass spectrum of m / Z=637 by FD-MS (field desorption mass spectrometry), and thus the compound BD4 was identified as the compound having the structure described above.

[0068] [Example 5] Synthesis of boron-containing compound BD5 (i) Synthesis of Compound 4-2 [ka] Compound 4-1 (1.86g, 20mmol), 1-bromo-3-chlorobenzene (4.59g, 24mmol), sodium-tert-butoxide (11.53g, 120mmol), and dehydrated toluene (200ml) were added to a 300mL four-necked flask equipped with a stirrer and nitrogen was bubbled for 1 hour. Tris(dibenzylideneacetone)dipalladium(0) (732mg, 0.8mmol) and JohnPhos (477mg, 1.6mmol) were added thereto and refluxed overnight with stirring. The disappearance of the raw materials was confirmed by TLC in the reaction mixture. Insoluble matter was filtered off by celite filtration, and the filtrate was concentrated. The resulting residue was purified by silica gel column chromatography to obtain compound 4-2 (4.27g, 13.6mmol) in a yield of 68%.

[0069] (ii) Synthesis of Compound 4-3 [ka] Compound 4-2 4.27g (13.6mmol), 2,4-difluoroaniline 4.21g (32.6mmol), sodium-tert-butoxide 7.32g (76.2mmol), and dehydrated toluene 140ml were added to a 200mL four-neck flask equipped with a stirrer, and nitrogen was bubbled for 1 hour. Tris(dibenzylideneacetone)dipalladium(0) 498mg (0.54mmol), tri-tert-butylphosphonium tetrafluoroborate 313mg (1.08mmol) were added thereto, and the mixture was refluxed and stirred overnight. The disappearance of the raw materials was confirmed by TLC in the reaction mixture. Insoluble matter was filtered off by celite filtration, and the filtrate was concentrated. The resulting residue was purified by silica gel column chromatography to obtain compound 4-3 5.16g (10.3mmol) in a yield of 76%.

[0070] (iii) Synthesis of compound 4-4 [ka] Compound 4-3 5.00g (10mmol), 3,5-dibromotoluene 2.50g (10mmol), sodium-tert-butoxide 2.88g (30mmol), and dehydrated toluene 1000mL were added to a 1000mL four-neck flask equipped with a nitrogen inlet tube, and nitrogen was bubbled for 1 hour. Then, bis(dibenzylideneacetone)palladium(0) 230mg (0.4mmol) and tri-tert-butylphosphonium tetrafluoroborate 93mg (0.32mmol) were added and refluxed overnight. The reaction mixture was confirmed to have disappeared by TLC. The reaction mixture was extracted with toluene, washed with brine, and dried with MgSO4, after which the solvent was distilled off. The resulting residue was purified by silica gel column chromatography to obtain compound 4-4 2.23g (3.8mmol) in a yield of 38%.

[0071] (iv) Synthesis of compound BD5 (boron-containing compound) [ka] Compound 4-4 (1.32 g, 2.25 mmol) and dehydrated dichlorobenzene (20 ml) were added to a degassed 50 mL two-neck flask and dissolved. 1M boron tribromide solution (9 ml, 9 mmol) was added dropwise and stirred for 5 minutes, and then stirred at a bath temperature of 180°C for 2 hours. Then, the mixture was placed in an ice bath at 0°C, diisopropylethylamine (2.35 ml, 13.5 mmol) was added dropwise, stirred for 5 minutes, and then stirred at room temperature for 30 minutes. Then, the mixture was heated to 120°C and stirred overnight. After cooling to room temperature, a short column was performed with silica gel. The resulting residue was purified by silica gel column chromatography and recrystallization to obtain compound BD5 (442 mg, 0.74 mmol) in a yield of 33%. The resulting compound BD5 was observed to have a mass spectrum of m / Z=595 by FD-MS (field desorption mass spectrometry), and thus the compound BD5 was identified as the compound having the structure described above.

[0072] [Fabrication and evaluation of the device] Example 6 A 26 mm×28 mm×0.7 mm glass substrate (manufactured by Optoscience Co., Ltd.) obtained by polishing an ITO film formed to a thickness of 180 nm by sputtering to 150 nm was used as a transparent support substrate. This transparent support substrate was fixed to a substrate holder of a commercially available deposition apparatus (manufactured by Showa Shinku Co., Ltd.), and a molybdenum deposition boat containing HATCN (HIM; hole injection material), a molybdenum deposition boat containing α-NPD (HTM; hole transport material), a molybdenum deposition boat containing EBL (electron barrier material), a molybdenum deposition boat containing BH1 (host), a molybdenum deposition boat containing the compound BD1 synthesized in Example 1, a molybdenum deposition boat containing HBL (hole barrier material), a molybdenum deposition boat containing NBPhen (ETM; electron transport material), a molybdenum deposition boat containing LiF, and a tungsten deposition boat containing aluminum were attached. The structural formulas of each material are shown below.

[0073] [ka]

[0074] The following layers were formed in order on the ITO film of the transparent support substrate. -4 The pressure was reduced to 10 Pa, and the deposition boat containing HIM was heated and deposited to a thickness of 5 nm to form a hole injection layer 2. Next, the deposition boat containing HTM was heated and deposited to a thickness of 105 nm to form a hole transport layer 3. Furthermore, the deposition boat containing EBL was heated and deposited to a thickness of 20 nm to form an electron blocking layer 4. Next, the deposition boat containing BH1 and the deposition boat containing the compound BD1 were heated simultaneously to deposit a film having a thickness of 25 nm to form the light-emitting layer 5. The deposition rate was adjusted so that the weight ratio of BH1 to the compound BD1 became approximately 97:3. Next, the deposition boat containing HBL was heated and deposited to a thickness of 20 nm to form a hole blocking layer 6. Next, the deposition boat containing ETM was heated and deposited to a thickness of 10 nm to form an electron transport layer 7. The deposition rate of each layer was 0.01-2 nm / s.

[0075] Thereafter, the deposition boat containing LiF, which is the material for the electron injection layer 8, was heated and deposited at a deposition rate of 0.01 to 0.1 nm / sec to a thickness of 1 nm. Next, the deposition boat containing aluminum was heated and deposited at a deposition rate of 0.01 to 2 nm / sec to a thickness of 100 nm to form the cathode 9, thereby obtaining an organic EL device. When a direct current voltage was applied between the ITO electrode as the anode 1 and the LiF / aluminum electrode as the cathode 9, blue light was emitted. When this was driven with a constant current at an initial brightness of 1000 nit, the time until the brightness reached 95% was measured.

[0076] Example 7 A device was prepared in exactly the same manner as in Example 6, except that the compound BD2 synthesized in Example 2 was used instead of the compound BD1.

[0077] Example 8 A device was prepared in the same manner as in Example 6, except that the compound BD3 synthesized in Example 3 was used instead of the compound BD1.

[0078] Example 9 A device was prepared in exactly the same manner as in Example 6, except that the compound BD4 synthesized in Example 4 was used instead of the compound BD1.

[0079] Example 10 A device was prepared in the same manner as in Example 6, except that the compound BD5 synthesized in Example 5 was used instead of the compound BD1.

[0080] Comparative Example 1 A device was prepared in exactly the same manner as in Example 6, except that a compound represented by the following structural formula was used instead of compound BD1. [ka]

[0081] When a DC voltage was applied between the ITO electrode as the anode and the LiF / aluminum electrode as the cathode, blue light was emitted. When this was driven with a constant current at an initial brightness of 1000 nit, the time until the brightness reached 95% was measured. [Table 1] It was found that the compound of the present invention maintains blue light emission with a shorter wavelength and a longer life than those of the prior art. [Explanation of symbols]

[0082] 1 Anode 2. Hole injection layer 3. Hole transport layer 4. Electron barrier layer 5. Light-emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Electron injection layer 9 Cathode

Claims

1. A boron-containing compound having a skeleton represented by the following general formula (1): 【Chemistry 1】 (In general formula (1), X is -BAr- (Ar is an aryl group), -CR 1 R 2 - (R 1 and R 2 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 ring atoms. 1 and R 2 may be linked to each other to form a ring; —NAr— (Ar is an aryl group); —O—, —SiR 3 R 4 - (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 ring atoms. 3 and R 4 may be linked together to form a ring; or -S-, o is 1 or 2, C 1 and C 2 is a carbon atom or an aryl carbon atom, C 1 and C 2 may each form a ring together with X and the adjacent carbon atom, Y is a fluoro group, and 0≦m+n≦10 (m and n are integers from 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. In the general formula (1), D 1 and D. 2 are all 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.

3. In the general formula (1), D 1 and D. 2 The boron-containing compound according to claim 1, wherein at least one of the above is a nitrogen atom, Y is a fluoro group, 0≦m+n≦10 (m and n are integers of 0 to 5), and Z is a hydrogen atom.

4. An organic EL device comprising the boron-containing compound according to any one of claims 1 to 3.

5. 4. An organic EL device comprising the boron-containing compound according to claim 1 in an emission band.

6. 4. An organic electroluminescence device comprising the boron-containing compound according to claim 1 in a light-emitting layer.

7. 4. An organic electroluminescence device comprising a light-emitting layer containing the boron-containing compound according to claim 1 in an amount of 0.1 to 20 wt %.

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