JP2020125287A - Arylamine derivative, hole transport material comprising the same, and organic el element using the same - Google Patents

Abstract

To provide: an arylamine derivative with a high triplet energy that can be a host material, specifically a hole transport material, of an organic EL element; and an organic EL element using the same.SOLUTION: The arylamine derivative is represented by general formula (1). (Rto Rare each independently a hydrogen atom, an alkyl group, an alkoxy group, or a mono- or di-alkylamino group; and X is an oxygen atom, a sulfur atom or an alkylene group (-CRR-).)SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an arylamine derivative having a high triplet energy, a hole transport material made of the same, and an organic EL device using the same.

In an organic EL element, by applying a voltage between a pair of electrodes, holes are injected from the anode and electrons from the cathode, respectively, into a light emitting layer containing an organic compound as a light emitting material, and the injected electrons and holes are injected. By recombination, excitons are formed in the light-emitting organic compound, and light emission can be obtained from the excited organic compound.

The problems of such an organic EL element are to improve luminous efficiency and durability. Excitons formed by an organic compound include singlet excitons (E _S1 ) and triplet excitons (E _T1 ). Fluorescence emission from singlet excitons (E _S1 ) and triplet excitons (E _S1 ) There is phosphorescence emission from _T1 ), but the statistical production ratio of these in the device is E _S1 :E _T1 =1:3, and the internal quantum efficiency of 25% is the limit in the organic EL device using fluorescence emission. It is said that. Therefore, in order to improve the conversion efficiency (internal quantum efficiency) from electrons to photons, a phosphorescent material capable of converting a triplet excited state into light emission has been developed, and development aiming at improvement of durability, An organic EL device utilizing phosphorescence has been reported.

Further, utilization of heat activated delayed fluorescence (TADF) is also important for improving the performance of the organic EL device. Although the TADF material is a fluorescent material composed of hydrogen, carbon, and nitrogen, it can theoretically achieve 100% probability of exciton generation, like the phosphorescent material, and is useful for high efficiency. Furthermore, because no precious metals such as iridium and platinum are required, development costs can be reduced. Therefore, it is considered that by developing a light emitting material using this TADF, a low cost and high efficiency light emitting element can be obtained.

On the other hand, in order to increase the efficiency and the longevity of the organic EL device using TADF, not only the light emitting material but also various carrier transporting materials such as a host material, an electron transporting material and a hole transporting material used together with the light emitting material. You will need it. However, for example, α-NPD, which is a typical hole transport material, has high durability but low triplet energy (T ₁ =2.28 eV), and is not suitable for phosphorescence or TADF organic EL devices. Therefore, development of a wide-gap hole transport material having high triplet energy is being studied. In 2013, Fukagawa et al. developed DBTPB in which dibenzothiophene was introduced at the end of arylamine derivative, and made the green phosphorescent device approximately 1.5 times more efficient than α-NPD and approximately 2 times longer in life. Has been realized (Non-Patent Document 1). On the other hand, in Cui et al., in the delayed fluorescence organic EL device, an n-type host (which usually has an acceptor part in the chemical structure) that transports electrons adjusts the carrier balance between electrons and holes, expands the recombination region, and at the same time, It was proved that formation of high-energy excitons is prevented and the life is extended (Non-Patent Document 2). According to Cui et al., the life of the green delayed fluorescent element exceeds 30 times and that of the blue delayed fluorescent element is 1000 times longer than that of a general p-type host material by using this n-type host. Is suitable for realizing a stable delayed fluorescence organic EL device.

H. Fukagawa et al., Appl. Phys. Lett., 103, 143306 (2013) Nature Communications, 8: 2250 (2017)

However, the triplet energy (T ₁ ) of DBTPB reported by Fukagawa et al. is about 2.37 eV (Non-patent Document 1), and a typical green color such as Ir(ppy) ₃ (T ₁ =2.53 eV). The triplet energy is insufficient for the use of phosphorescent dopant, blue phosphorescent, or green/blue TADF dopant, and there is a concern that efficiency will decrease due to quenching of excitons at the interface between the hole transport layer and the light emitting layer. There is. Further, Non-Patent Document 2 realizes a longer life by improving an n-type host instead of a hole transport material. It is thought that improvement of not only the host but also the hole transport material can contribute to higher efficiency and longer life. However, the conventional hole transport material has durability and triplet energy (T ₁ ). There is still a trade-off, and development of a hole transport material having all of durability, high triplet energy (T ₁ ) and hole transportability is still a challenge.
Therefore, it is an object of the present invention to provide an arylamine derivative having durability, high triplet energy (T ₁ ) and high mobility, and a hole transport material and an organic EL device using the arylamine derivative.

The present invention comprises the following items.
The arylamine derivative of the present invention is characterized by being represented by the following general formula (1).

However, in the general formula (1), R ^{1 to} R ⁷ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a linear or branched carbon atom having 1 to 6 carbon atoms. alkoxy group, or a linear or branched mono-1 to 6 carbon atoms - alkyl amino group, X is an oxygen atom, a sulfur atom or an alkylene group - or di (-CR ⁸ R ⁹ -) is (R ⁸ and R ⁹ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxy group having 1 to 6 carbon atoms, or a linear or branched It is a mono- or di-alkylamino group having 1 to 6 carbon atoms.) and Ar is a substituent represented by the following general formula (2).

However, in the general formula (2), R ^{10 to} R ³⁷ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a linear or branched carbon atom having 1 to 6 carbon atoms. It is an alkoxy group or a linear or branched mono- or di-alkylamino group having 1 to 6 carbon atoms.
In the general formula (1), X is preferably an oxygen atom or a sulfur atom.
In the general formula (1), R ^{1 to} R ³⁷ are preferably hydrogen atoms or phenyl groups.
The hole transport material of the present invention is formed of the arylamine derivative.
The organic EL device of the present invention uses the arylamine derivative.

According to the present invention, an arylamine derivative represented by the general formula (1), specifically, a symmetric arylamine derivative having four dibenzofuran moieties can be efficiently synthesized. Since the hole transport material composed of the arylamine derivative has a high triplet energy (T ₁ ), the green TADF light emitting material can efficiently emit light. Therefore, according to the present invention, a highly efficient organic EL element can be provided.

¹ represents the ¹ H NMR spectrum (FIG. 1 a) and ¹³ C NMR spectrum (FIG. 1 b) of T4DBFHPB. PYS measurement results of T4DBFHPB (FIG. 2a), UV-vis absorption spectrum (FIG. 2b), PL spectrum (FIG. 2c), transient photocurrent decay curve (electric field intensity 1.8×10 ⁵ Vcm ⁻¹ ) (FIG. 2d), The low temperature phosphorescence spectrum (FIG. 2e) and the electric field strength dependence of the hole mobility are shown (FIG. 2f). Current density-luminance-voltage characteristics (Fig. 3a), external quantum efficiency-luminance characteristics (Fig. 3b), and power of the green TADF device in which T4DBFHPB was used for the hole transport layer (HTL) and 4CzIPN was doped in the mCBP host layer at 15 wt%. The efficiency-luminance characteristics (FIG. 3c) and the EL emission spectrum (FIG. 3d) are shown. Current density-luminance-voltage characteristics (FIG. 4a), external quantum efficiency-luminance characteristics of a green TADF device in which T4DBFHPB was used for the hole transport layer (HTL) and 4CzIPN was doped in the mCBP host layer at 10 wt%, 15 wt% and 20 wt%. (FIG. 4b), power efficiency-luminance characteristics (FIG. 4c), EL emission spectrum (FIG. 4d), device lifetime at current density of 10 mAcm ⁻² (FIG. 4e), and luminance half life initial luminance acceleration test results (FIG. 4f). ) Represents. 1 shows a schematic diagram of a Time-of-Flight (TOF) measurement system and an equation for determining mobility. 1 shows a structure of an organic EL element of the present invention. ¹ shows the ¹ H NMR spectrum (FIG. 7a) and ¹³ C NMR spectrum (FIG. 7b) of TDBFBP.

¹ shows the ¹ H NMR spectrum (FIG. 8a) and ¹³ C NMR spectrum (FIG. 8b) of TDBFP. ¹ represents the ¹ H NMR spectrum of TDBFTP. ¹ represents the ¹ H NMR spectrum of TDBFSBF1. ¹ shows the ¹ H NMR spectrum (FIG. 11 a) and ¹³ C NMR spectrum (FIG. 11 b) of TDBFSBF2. The UV-vis absorption spectrum (FIG. 12 a ), the PL spectrum (FIG. 12 b ), the low temperature phosphorescence spectrum (FIG. 12 c ), and the PYS measurement result (FIG. 12 d) of TDBFBP are shown. Current density-voltage characteristics (FIG. 13a), brightness-voltage characteristics (FIG. 13b) of a green TADF device in which T4DBFHPB was used for the hole transport layer (HTL) and 4CzIPN was doped in the mCBP host layer at 10 wt%, 15 wt% and 20 wt%. , Current efficiency-luminance characteristics (Fig. 13c), power efficiency-luminance characteristics (Fig. 13d), external quantum efficiency-luminance characteristics (Fig. 13e), and EL emission spectrum (Fig. 13f). Current density-voltage characteristics (FIG. 14a), brightness-voltage characteristics of a sky blue TADF device in which T4DBFHPB is used for the hole transport layer (HTL) and 5TCzBN is doped in the mCBP host layer at 10 wt%, 20 wt%, 30 wt%, and 40 wt%. (Fig. 14b), current efficiency-luminance characteristic (Fig. 14c), power efficiency-luminance characteristic (Fig. 14d), external quantum efficiency-luminance characteristic (Fig. 14e), and EL emission spectrum (Fig. 14f).

Hereinafter, the present invention will be described in detail.
[Arylamine derivative]
The arylamine derivative of the present invention is characterized by being represented by the general formula (1).
In formula (1), R ^{1 to} R ⁷ are each a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxy group having 1 to 6 carbon atoms, or a straight chain. chain or branched mono-1 to 6 carbon atoms - or di - alkylamino group, X is an oxygen atom, a sulfur atom or an alkylene group - is (-CR ⁸ R ^9). R ⁸ and R ⁹ are a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxy group having 1 to 6 carbon atoms, or a linear or branched carbon atom number. 1 to 6 mono- or di-alkylamino groups.

A straight-chain or branched alkyl group having 1 to 6 carbon atoms includes methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group. Group, neopentyl group, isopentyl group, s-pentyl group, 3-pentyl group, t-pentyl group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, and 2 , 3-dimethylbutyl group and the like.

The linear or branched alkoxy group having 1 to 6 carbon atoms includes methoxy group, ethoxy group, propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, s-butoxy group, t-butoxy group, n- Pentoxy group, neopentoxy group, isopentoxy group, s-pentoxy group, 3-pentoxy group, t-pentoxy group, n-hexoxy group, 2-methylpentoxy group, 3-methylpentoxy group, 2,2-dimethylbutoxy group , And a 2,3-dimethylbutoxy group.

The linear or branched mono- or di-alkylamino group having 1 to 6 carbon atoms includes methylamino group, ethylamino group, propylamino group, isopropylamino group, n-butylamino group, isobutylamino group, s. -Butylamino group, t-butylamino group, n-pentylamino group, neopentylamino group, isopentylamino group, s-pentylamino group, 3-pentylamino group, t-pentylamino group, n-hexylamino group , 2-methylpentylamino group, 3-methylpentylamino group, 2,2-dimethylbutylamino group, and 2,3-dimethylbutylamino group, dimethylamino group, diethylamino group, dipropylamino group, diisopropylamino group, Examples thereof include an ethylmethylamino group, a methylpropylamino group, an isopropylmethylamino group, an ethylpropylamino group, an ethylisopropylamino group, and an isopropylpropylamino group.

Ar is a substituent represented by the following general formula (2).

In formula (2), R ^{10 to} R ³⁷ are each a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxy group having 1 to 6 carbon atoms, or a straight chain. A chain or branched mono- or di-alkylamino group having 1 to 6 carbon atoms. In general formula (2), the double wavy line represents the position of the bond.
Linear or branched alkyl group having 1 to 6 carbon atoms, linear or branched alkoxy group having 1 to 6 carbon atoms, or linear or branched mono- or di-alkyl having 1 to 6 carbon atoms The amino group is the same as described above for R ^{1 to} R ⁷ , R ⁸ and R ⁹ .
Of these, R ^{1 to} R ⁷ and R ^{10 to} R ³⁷ are preferably hydrogen atoms, methyl groups or phenyl groups, and more preferably hydrogen atoms.
X is preferably an oxygen atom, a sulfur atom, or a methyl group or a phenyl group for R ⁸ and R ^9, and more preferably an oxygen atom.

The arylamine derivative represented by the general formula (1) is particularly preferably a compound represented by the following structural formula (T4DBFHPB, TDBFBP, TDBFP, TDBFTP, TDBFSBF1 or TDBFSBF2).

The arylamine derivative has a structure in which a π-conjugated system is spread. As the π-conjugated system spreads, HOMO rises and LUMO falls. 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 dyes. Furthermore, the energy gap can be adjusted by appropriately adding a functional group to such a molecule to change the electronic property. In the present invention, in the arylamine derivative, molecular design is performed so as to minimize the energy gap between the singlet excited state (E _S1 ) and the triplet excited state (E _T1 ), so that the energy which has once been transferred to the triplet excited state is obtained. Can be returned to the singlet excited state again, and highly efficient fluorescence can be extracted. Therefore, the arylamine derivative of the present invention is suitably used for a green phosphorescent device using a phosphorescent light emitting material Ir(ppy) ₃ having a peak wavelength of 514 nm as a green fluorescent material.

The arylamine derivative of the present invention can be produced, for example, by the method shown below. An example of the method for producing T4DBFHPB is shown.

4-Bromodibenzofuran (4-BrDBF) and benzophenoneimine are cross-coupled in the presence of Pd ₂ (dba) ₃ , a phosphine ligand ± BINAP and a base to synthesize 4DBNCPh ₂ , and then hydrochloric acid is added. Then, 4DBFNH ₂ is synthesized by heating and refluxing. The obtained 4DBFNH ₂ and 4-BrDBF are cross-coupled again in the same manner to obtain B4DBFNH. Further, B4DBFNH and dibromohexaphenylbenzene are subjected to the same cross-coupling reaction to obtain T4DBFHPB in high yield.
The arylamine derivative of the present invention is not limited to the above method and can be produced by various known methods.

[Hole transport materials, organic EL devices]
The hole transport material and the organic EL device of the present invention use the above arylamine derivative.
The organic EL element has a structure in which one or more organic layers are laminated between electrodes, and for example, (i) electrode 2/hole transport layer 4/light emitting layer 5/electron transport layer 7/electrode 8 or ( ii) It has a structure in which the electrode 2, the hole transport layer 4, the light emitting layer 5, the electron transport layer 7, the electron injection layer, and the electrode 8 are laminated in this order. FIG. 6 shows a layer structure of the organic EL device of the example, in which an electrode 2 is formed on a substrate 1, and a hole injecting and transporting layer 3, a hole transporting layer 4, a light emitting layer 5, and a hole are formed on the electrode 2. The structure in which the blocking layer 6, the electron transport layer 6, and the electrode 8 are laminated in this order is shown. The organic layer refers to layers other than the electrodes, that is, a hole injecting and transporting layer, a hole transporting layer, a light emitting layer, a hole blocking layer, an electron transporting layer, and the like.

As the substrate 1, a transparent and smooth substrate having a total light transmittance of at least 70% or more is used. Specifically, it is a flexible transparent substrate such as a glass substrate having a thickness of several μm or a special transparent substrate. Plastic or the like is used.

The thin films formed on the substrate 1, such as the electrode 2, the hole injecting and transporting layer 3, the hole transporting layer 4, the light emitting layer 5, the hole blocking layer 6, the electron transporting layer 7 and the electrode 8, are formed by a vacuum deposition method or a coating method. Stacked. When the vacuum vapor deposition method is used, the vapor deposition is usually heated in an atmosphere reduced to 10 ⁻³ Pa or less. The film thickness of each layer varies depending on the type of layer and the material used, but is usually about 100 nm for the electrodes 2 and 8 and less than 50 nm for the other organic layers including the light emitting layer 5.

The electrode 2 is usually an anode, has a large work function, and has a total light transmittance of usually 80% or more. Specifically, in order to transmit light emitted from the anode, transparent conductive ceramics such as indium tin oxide (ITO) and ZnO, transparent conductive polymers such as PEDOT/PSS and polyaniline, and other transparent conductive materials are used. Used. The film thickness of the anode is usually 10 to 200 nm.

In the light emitting layer 5, it is preferable to use a host compound together with a light emitting material, as in the case of other light emitting layers used in an organic EL device. Examples of the light emitting material include tris(2-phenylpyridinato)iridium(III)(Ir(ppy) ₃ ) and bis[2-(4,6-difluorophenyl)pyridinato-C2, which are phosphorescent materials. N](picolinato)iridium(III)(FIrpic), tris[1-phenylisoquinoline-C2,N]iridium(III)(Ir(piq) ₃ ), and thermally activated delayed fluorescent materials (4s, 6s). -2,4,5,6-Tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN), 2,3,4,5,6-pentakis-(3,6-di-t-butyl-9H -Carbazolyl-9-yl)benzonitrile (5TCzBN),10,10'-(4,4'-sulfonylbis(4,1-phenylene))bis(9,9-dimethyl-9,10-dihydroacridine)) (DMAC-DPS) and the like. Examples of the host compound include bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO), 3,6-bis(diphenylphophoryl)-9-phenylcarbazole (PO9), and 4,4′-bis. (N-carbazolyl)-1,1′-biphenyl (CBP), 3,3′-bis(N-carbazolyl)-1,1′-biphenyl (mCBP), tris(4-carbazoyl-9-ylphenyl)amine (TCTA), 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT), adamantane anthracene (Ad-Ant), rubrene, and 2,2′-bi(9,10-diphenylanthracene) (TPBA) Can be mentioned.

A hole injecting and transporting layer 3 and a hole transporting layer 4 are provided between the anode and the light emitting layer 5 in order to efficiently transport holes from the anode to the light emitting layer.
Examples of the hole injecting/transporting material forming the hole injecting/transporting layer 3 include (poly(arylene ether ketone)-containing triphenylamine (KLHIP:PPBI), hexaazatriphenylenecarbonitrile (HATCN), and PEDOT:PSS. The hole injecting and transporting layer 3 has an effect of lowering the driving voltage of the organic EL element, and the film thickness of the hole injecting and transporting layer 3 is usually 1 to 20 nm.

The hole transport layer 4 is provided between the anode (electrode 2) and the light emitting layer 5 and is a layer for efficiently transporting holes from the anode to the light emitting layer. As the hole transport material, a material having a low ionization potential, that is, a material in which electrons are easily excited from HOMO and holes are easily generated, is used. Specifically, the arylamine derivative of the present invention is used. In addition, poly(9,9-dioctylfluorene-alto-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) , 4,4′,4″-tri-9-carbazolyltriphenylamine (TCTA) and 4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine) in combination. May be.

The electrode 8 is usually the cathode. In order to efficiently transport electrons from the cathode to the light emitting layer 5, a hole blocking layer 6 and an electron transport layer 7 are provided between the electrode 8 and the light emitting layer 5. Examples of the electron transport material forming the electron transport layer 7 include 1,4-bis(1,10-phenanthrolin-2-yl)benzene (DPB), 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-phenyl Pyrimidine (B4PyPPm), 2-(4-biphenylyl)-5-(pt-butylphenyl)-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), 3-(4-biphenylyl) -4-Phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ) and the like can be mentioned. Among these, TPBi and TAZ are electron transport materials having excellent hole blocking properties. Examples of the hole blocking material include dibenzothiophene-triazine (DBT-TRZ). The thicknesses of the hole blocking layer 6 and the electron transport layer 7 can be appropriately changed depending on the intended design, but are usually 3 to 50 nm.

The electrode 8 has a low work function (4 eV or less) and is chemically stable. Specifically, a cathode material such as Al, a MgAg alloy, or an alloy of Al and an alkali metal such as AlLi or AlCa is used. These cathode materials are formed by, for example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, or an ion plating method. The thickness of the cathode is usually 10 nm to 1 μm, preferably 50 to 500 nm.

In addition, layers such as the hole blocking layer 6, the electron blocking layer, and the exciton blocking layer are further formed as needed.

Hereinafter, the present invention will be described more specifically based on Examples, but the present invention is not limited to the following Examples.

[Synthesis of arylamine derivative]
The equipment and measurement conditions used for identifying the compound are as follows.
(1) ¹ H nuclear magnetic resonance method (NMR)
JEOL Ltd., 400MHz, JNM-EX270FT-NMR
(2) ¹³ C nuclear magnetic resonance method (NMR)
JEOL Ltd., 100MHz, JNM-EX270FT-NMR
(3) Mass spectrometry (MS)
JMS-K9 [desktop GCQMS] manufactured by JEOL Ltd.
(4) Elemental analyzer Perkin Elmer 2400II CHNS/O analyzer Measurement mode: CHN mode

[Example 1] Synthesis of T4DBFHPB (i) Synthesis of 4DBFNCPh ₂

To a 25 ml three-necked flask, 2.47 g (10 mmol) of 4-BrDBF, 1.68 ml (10 mmol) of benzophenone imine, 2.5 mg (2.6 mmol) of t-BuONa, and 50 ml of dry toluene were added, and N ₂ bubbling was performed for 1 hour. Then, 370 mg (0.4 mmol) of Pd ₂ (dba) _{3 and} 560 mg (0.9 mmol) of ±BINAP were added, and the mixture was stirred at 90° C. under nitrogen. After confirming consumption of the raw materials by TLC, the mixture was cooled to room temperature, then filtered through a glass filter filled with silica gel, concentrated and dried under reduced pressure to obtain the desired product.
Yield 3.39g, yield 98%
MS: [M ⁺ ]=348.1 m/z

(Ii) Synthesis of 4DBFNH ₂
4DBFNCPH ₂ 3.39mg eggplant flask 100 ml (9.8 mmol), added THF 50 ml and 2M HClaq 50 ml, was stirred at reflux for 5 hours. After confirming the disappearance of the raw material and the formation of the target substance by TLC, the sample was cooled to room temperature. Then, 0.5M HClaq and hexane:ethyl acetate=2:1 were used for liquid separation, the target substance was transferred to the aqueous layer, NaOHaq was added to the aqueous layer to release the target substance, and the mixture was extracted with toluene. The organic layer was dried over anhydrous magnesium sulfate, filtered, concentrated, and dried under reduced pressure to obtain the desired product. The target product was identified by ¹ H-NMR and MS.
Yield 1.62g, 88% yield
MS: [M+]=181.7 m/z

(Iii) Synthesis of B4DBFNH
4DBFNH ₂ 378 mg (2.0 mmol), 4BrDBF 494 mg (2.0 mmol), t-BuONa 500 mg (5.2 mmol) and dry toluene 20 ml were added to a 25 ml three-necked flask, and N ₂ bubbling was performed for 1 hour. Then, 74 mg (0.08 mmol) of Pd ₂ (dba) _{3 and} 112 mg (0.18 mmol) of ±BINAP were added, and the mixture was stirred under reflux for 21 hours under a nitrogen stream. After confirming the disappearance of the raw materials by TLC, it was cooled to room temperature. Then, extraction was performed 3 times with 100 ml of toluene, and the organic layer was dried over anhydrous magnesium sulfate and filtered. The filtrate was filtered through a glass filter filled with silica gel, concentrated and dried under reduced pressure to obtain the desired product.
Yield 0.57g, 81%
MS: [M ⁺ ]=350.1 m/z

(Iv) Synthesis of T4DBFHPB
350 mg (1.0 mmol) of B4DBFNH, 346 mg (0.5 mmol) of DBrHPB, 250 mg (2.6 mmol) of t-BuONa and 10 ml of dry toluene were added to a 25 ml three-necked flask, and N ₂ bubbling was performed for 1 hour. _{Then, Pd 2 (dba) 3 45.8mg} (0.05mmol), t-Bu 3 P + BF 4 - 29mg a (0.1 mmol) added, and the mixture was stirred under reflux under a nitrogen flow for 20 hours. After confirming the disappearance of the raw materials by TLC, it was cooled to room temperature. Then, extraction with 100 ml of toluene was performed 3 times, and the organic layer was dried over anhydrous magnesium sulfate, filtered, and concentrated to obtain a brown viscous body. The product was purified by silica gel column chromatography (developing solvent: toluene/hexane=1/1) to obtain the desired product (470 mg, yield 78%). The target product was identified by ¹ H-NMR, ¹³ C-NMR, MS and elemental analysis.
¹ HNMR (400 MHz, CDCl ₃ ) δ=7.90 (d, J=7.8 Hz, 4 H), 7.66 (dd, J=7.5, 1.1 Hz, 4 H), 7.35-7. 39 (m, 4H), 7.27-7.31 (m, 8H), 7.15 (t, J = 7.8 Hz, 4H), 6.84-6.97 (m, 24H), 6 .67-6.70 (m, 4H), 6.57 (dd, J=6.6, 2.1 Hz, 4H);
¹³ CNMR (100 MHz, CDCl ₃ ) δ=156.06, 149.95, 143.95, 140.93, 140.50, 140.28, 135.48, 132.08, 131.90, 131.71, 126.98, 126.78, 125.87, 125.24, 124.40, 123.36, 123.25, 122.71, 120.72, 120.60, 116.07, 112.25, 77. 48, 77.16, 76.84 ppm;
MS: m/z 1230 [M] ⁺ ;
Elemental analysis (%) calcdfor C ₉₀ H ₅₆ N ₂ O ₄ :C87.92, H 4.59, N 2.28; found: C87.84, H4.58, N2.30.

[Example 2] Synthesis of TDBFBP
In a 30 ml four-necked flask, B4DBFNH 1.048 g (3.0 mmol) synthesized in Example 1, 3,3′-dibromobiphenyl 468 mg (1.5 mmol), t-BuONa 750 mg (7.8 mmol) and dry toluene. 30 ml was added and N ₂ bubbling was performed for 2 hours. _{Then, Pd 2 (dba) 3 137mg} (0.15mmol) and ^{_{t-Bu 3 P + BF 4}} - 87mg a (0.3 mmol) were added, followed 22 hours reflux stirred under a nitrogen stream. After confirming the disappearance of the raw materials by TLC, the temperature was returned to room temperature. Then, extraction was performed 3 times with 100 ml of toluene, and the organic layer was dried over anhydrous magnesium sulfate, filtered, and concentrated. Purification by silica column chromatography (developing solvent: toluene/hexane=1/1) gave 1.082 g of the desired product in a yield of 78%. The target product was identified by ¹ H-NMR, ¹³ C-NMR and MS.
¹ H-NMR (400 MHz, CDCl ₃ ) δ=7.92 (dd, J=8.0, 1.1 Hz, 4 H), 7.71 (dd, J=7.3, 1.4 Hz, 4 H), 7.38-7.32 (m, 4H), 7.31 (s, 4H), 7.30-7.27 (m, 4H), 7.24 (dd, J=8.2, 1.4Hz) , 4H), 7.19(t, J=7.8Hz, 4H), 7.16-7.09(m, 4H), 7.02(d, J=7.8Hz, 2H), 6.83. (Dd, J=7.5, 2.1 Hz, 2H);
¹³ C-NMR (100 MHz, CDCl ₃ ) δ=156.02, 150.55, 147.08, 141.94, 131.18, 129.01, 127.03, 126.01, 124.33, 123. 45, 122.62, 120.57, 119.05, 116.80, 112.11, 30.95;
MS: m/z 849.7 [M] ⁺

[Example 3] Synthesis of TDBFP
To a 100 ml four-necked flask, B4DBFNH 2.795 g (8.0 mmol), 1,3-dibromobenzene 944 mg (4.0 mmol), t-BuONa 2.000 g (20.8 mmol) and dry toluene 80 ml were added, and N ₂ was added. Bubbling was performed for 2 hours. _{Then, Pd 2 (dba) 3 366mg} (0.40mmol) and ^{_{t-Bu 3 P + BF 4}} - 232mg of (0.8 mmol) were added, followed 22 hours reflux stirred under a nitrogen stream. After confirming the disappearance of the raw materials by TLC, the mixture was filtered through Celite and the filtrate was concentrated. The product was purified by silica gel chromatography (developing solvent: toluene), concentrated, and washed with methanol to obtain 2.866 g of the desired product with a yield of 93%. The target product was identified by ¹ H-NMR, ¹³ C-NMR and MS.
¹ H-NMR (600 MHz, CDCl ₃ ) δ=7.90 (d, J=7.6 Hz, 4 H), 7.60-7.56 (m, 4 H), 7.41-7.35 (m, 8H), 7.34-7.29 (m, 4H), 7.14 (d, J=6.9Hz, 4H), 7.06 (t, J=7.9Hz, 1H), 6.84( t, J=7.6 Hz, 4H), 6.71 (t, J=2.4 Hz, 1H), 6.60 (dd, J=7.9, 2.4 Hz, 2H);
¹³ C-NMR (100 MHz, CDCl ₃ ) δ=156.04, 150.35, 147.38, 131.15, 129.32, 126.97, 125.77, 124.21, 123.13, 122. 59, 120.52, 116.43, 114.30, 113.13, 112.03
MS: m/z 773.5 [M] ⁺

Example 4 Synthesis of TDBFTP
In a 100 ml four-necked flask, 1.048 g (3.0 mmol) of B4DBFNH, 582 mg (1.5 mmol) of 3,3′-dibromo-1,1′:3′,1-terphenyl, and 750 mg of t-BuONa (7). 0.8 mmol) and 40 ml of dry toluene were added, and N ₂ bubbling was carried out for 1 hour. _{Then, Pd 2 (dba) 3 134mg} (0.15mmol) and ^{_{t-Bu 3 P + BF 4}} - 87mg (0.3mmol) were added. The resulting 20 hour reflux stirring under a nitrogen flow. After confirming the disappearance of the raw materials by TLC, the mixture was filtered through Celite and the filtrate was concentrated. It was purified by silica gel chromatography (developing solvent: toluene/hexane=1/1) to obtain the desired product (770 mg, yield 56%). The target product was identified by ¹ H-NMR.
¹ H-NMR (600 MHz, CDCl ₃ ) δ=7.95 (d, J=7.6 Hz, ⁰ H), 7.76 (d, J=7.6 Hz, ⁰ H), 7.53 (s, 0 H) , 7.39-7.32 (m, 1H), 7.32-7.27 (m, 1H), 7.25-7.16 (m, 1H), 7.06 (d, J=7. 6Hz, 0H), 6.89 (dd, J=8.3, 2.1Hz, 0H)

Example 5 Synthesis of TDBFSBF1
In a 100 ml four-necked flask, 2.096 g (6.0 mmol) of B4DBFNH, 1.423 g (3.0 mmol) of 2,7-dibromo-9,9'-spirobifluorene, 1.500 g of t-BuONa (15.6 mmol). ) And 60 ml of dry toluene were added, and N ₂ bubbling was performed for 1.5 hours. _{Then, Pd 2 (dba) 3 275mg} (0.30mmol) and ^{_{t-Bu 3 P + BF 4}} - 174mg of (0.6 mmol) were added, followed 25 hours reflux stirred under a nitrogen stream. After confirming the disappearance of the raw materials by TLC, the mixture was filtered through Celite and the filtrate was concentrated. Purification by silica gel chromatography (developing solvent: toluene/hexane=1/1) gave 1.71 g of the desired product in a yield of 60%. The target product was identified by ¹ H-NMR and MS.
¹ H-NMR (600 MHz, DMSO-D6) δ 8.07 (d, J=7.6 Hz, 4 H), 7.85 (d, J=7.6 Hz, 4 H), 7.77 (d, J=8). .3 Hz, 2 H), 7.49-7.43 (m, 6 H), 7.41 (d, J=8.3 Hz, 4 H), 7.37 (t, J=6.9 Hz, 4 H), 7 .21 (t, J=7.9 Hz, 4H), 7.00 (d, J=7.6 Hz, 4H), 6.92-6.85 (m, 4H), 6.65 (d, J= 7.6 Hz, 2 H), 6.59 (t, J=7.6 Hz, 2 H), 5.94 (d, J=2.1 Hz, 2 H)
MS: m/z 849.7 [M] ⁺

Example 6 Synthesis of TDBFSBF2
In a 100 ml four-necked flask, 2.096 g (6.0 mmol) of B4DBFNH, 1.423 g (3.0 mmol) of 2,2'-dibromo-9,9'-spirobifluorene, and 1.500 g of t-BuONa (15. 6 mmol) and 60 ml of dry toluene were added, and N ₂ bubbling was performed for 3 hours. _{Then, Pd 2 (dba) 3 275mg} (0.30mmol) and ^{_{t-Bu 3 P + BF 4}} - 174mg of (0.6 mmol) were added, followed 21 hours reflux stirred under a nitrogen stream. The disappearance of the raw materials was confirmed by TLC. It was purified by silica gel chromatography (developing solvent: toluene/hexane=1/1) and washed with methanol. 2.37 g of the target product was obtained with a yield of 78%. The target product was identified by ¹ H-NMR and ¹³ C-NMR.
¹ H-NMR (600 MHz, CDCl ₃ ) δ=7.87 (d, J=7.6 Hz, 4 H), 7.66 (d, J=7.6 Hz, 4 H), 7.51 (dd, J= 10.7, 7.9 Hz, 4H), 7.30 (dd, J=7.6, 1.4 Hz, 3H), 7.28 (d, J=1.4 Hz, 2H), 7.27 (d , J=1.4 Hz, 2 H), 7.25 (s, 1 H), 7.21 (d, J=8.3 Hz, 4 H), 7.16 (t, J=7.6 Hz, 4 H), 7 0.06 (qd, J=6.9, 1.7 Hz, 6H), 6.93 (dd, J=8.3, 2.1 Hz, 2H), 6.70-6.66 (m, 2H), 6.61 (d, J=7.6 Hz, 2H), 6.57 (d, J=2.1 Hz, 2H);
¹³ C-NMR (100 MHz, CDCl ₃ ) δ=155.89, 149.74, 148.86, 146.58, 141.16, 136.50, 131.48, 127.15, 126.89, 126. 60, 125.93, 124.13, 123.55, 123.23, 122.52, 121.50, 120.40, 120.22, 119.09, 117.59, 116.10, 112.08, 65.89

[Evaluation of arylamine derivatives]
[Molecular orbital calculation]
The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the lowest triplet excited state (T ₁ ) of T4DBFHPB obtained in Example 1 were DFT calculated (Gaussian03W, B3LYP/6-311+G(d,p) )//6-311G). The results are shown in Table 1.

[Thermophysical properties]
(I) Glass transition temperature (T _g ), crystallization temperature (T _c ), melting point (T _m ).
Sublimation-purified T4DBFHPB was sealed in an aluminum pan, and a glass transition temperature (T _g ) at a temperature rising rate of 10°C/min in nitrogen gas using a differential scanning calorimeter (manufactured by Perkin Elmer Japan; DSCDTA) and crystals. The crystallization temperature (Tc) and melting point ( _Tm ) were measured.
(Ii) Decomposition point (T _d5 ).
Sublimation-purified T4DBFHPB, TDBBFBP, TDBFPBF, TDBFSBF1 and TDBFSBF2 of Examples 1 to 5 and 6 were placed on an aluminum pan, and a differential thermogravimetric analyzer (manufactured by Perkin Elmer Japan Co., Ltd.; TGA Diamond) was used for nitrogen gas. The 5% weight decay temperature (T _d5 ) was measured at a heating rate of 10° C./min.
The results are shown in Table 2. In Table 2, "-" indicates that it was not measured.

[optical properties]
The equipment and measurement conditions used for optical property evaluation are as follows.
(1) Ultraviolet/visible (UV-vis) spectrophotometer UV-3150 manufactured by Shimadzu Corporation
Measurement conditions; scan speed medium speed, measurement range 200 to 800 nm, sampling pitch 0.5 nm, slit width 0.5 nm
(2) Photoluminescence (PL) measuring device Fluoro MAX-2 manufactured by Horiba Ltd.
A PL spectrum and a time-resolved PL spectrum (PL transient spectrum) using a streak camera (C4334 manufactured by Hamamatsu Photonics KK) were measured at room temperature (300 K) and low temperature (5 K).
(3) Photoelectron yield spectroscopy (PYS) device Sumitomo Heavy Industries, Ltd. ionization potential measuring device The ionization potential (Ip) was measured in vacuum using the ionization potential measuring device.
The electron affinity (E _a ) was calculated by estimating the energy gap (E _g ) from the absorption edge of the UV-vis absorption spectrum.

Regarding T4DBFHPB obtained in Example 1 and TDBFBP obtained in Example 2, PYS (Fig. 2a, Fig. 12d), UV-vis absorption spectrum (Fig. 2b, Fig. 12a), PL spectrum (Fig. 2c, Fig. 12b). , Low temperature phosphorescence spectrum (FIG. 2e, FIG. 12c), based on the measurement results, ionization potential (I _p ), band gap energy (E _g ), electron affinity (E _a ), exciton energy (E _T ), PL spectrum The absorption maximum (λ _PL ) of was determined. The results are shown in Table 3.

[Hole transportability]
The hole mobility of T4DBFHPB was measured by the Time-of-Flight (TOF) method (FIGS. 2d and 2f). The TOF method measurement system and mobility equation are shown in FIG. In the TOF method, a voltage is applied between both electrodes of the sample thin film, and a short pulse laser beam of about 400 ps is applied to generate photocarriers in the light absorption region near ITO. The mobility can be calculated by measuring the time that the photo carrier drifts. The drift mobility (μ) is obtained by multiplying the electric field intensity (E) by the transit time (t _tr ) obtained by the measurement and dividing by the film thickness.
The following samples were prepared and measured. The sample film thickness was increased to about 1 to 10 μm in order to provide a traveling distance for carriers to move sufficiently with respect to the light absorption region. The measurement was performed at 298 K and 1.0 atm.
ITO (130 nm thickness)/T4DBFHPB (5.58 μm thickness)/Al
As a result of the measurement, T4DBFHPB has a hole mobility of 9.8×10 ^{−3 to} 1.0×10 ⁻² Vcm ⁻¹ s ⁻¹ at an electric field strength of 1.5×10 ^{5 to} 5.1×10 ⁵ Vcm ^1. showed that. This result indicates that T4DBFHPB has a particularly high mobility among the hole transport materials used for organic EL, and suggests that T4DBFHPB has an extremely high hole transport property.

[Production and Evaluation of Green TADF Element]
The equipment used for the evaluation of the light emitting characteristics of the organic EL element is as follows.
Device: PHOTONIC MULTI-CHANNEL ANALYZER PMA-1 manufactured by Hamamatsu Photonics Co., Ltd.

A schematic sectional view of the device is shown in FIG. The materials used are shown below.

<Production of green TADF element>
A green TADF element having the following structure was produced. In addition, HTL represents a hole transport layer, and the thickness in parentheses represents a film thickness (nm).
A green TADF element was manufactured with the following structure.
ITO (100)/triphenylamine-containing polymer: PPBI (20)/
NPD(10)/HTL(10)/mCBP: 15 wt% 4CzIPN(30)/DBT-TRZ(10)/DPB: 20 wt% Liq(40)/Libpp(1)/Al
HTL is DBTPB or T4DBFHPB.
The initial characteristics of the green TADF element are shown in Table 4 and FIGS. 3(a) to 3(d).

It was found that the voltage of T4DBFHPB was significantly lower and the efficiency thereof was higher than that of DBTPB. The reason for this is that T4DBFHPB has a sufficiently high E _T (2.8 eV) so that excitons can be effectively confined, and that hole transportability is excellent and carrier balance is improved.

<Fabrication of dope concentration optimization device>
A green TADF element having the following structure was produced. HTL represents the hole transport layer, and the thickness in parentheses represents the film thickness (nm).
A green TADF element was manufactured with the following structure.
ITO(100)/triphenylamine-containing polymer: PPBI(20)/NPD(10)/T4DBFHPB(10)/mCBP:xwt%4CzIPN(30)/DBT-TRZ(10)/DPB:20wt%Liq(40) /Libpp(1)/Al
x=10, 15 or 20 wt%
The results of device characteristics are shown in Table 5 and FIGS. 4(a) to 4(f).

(2) Green TADF element A green TADF element having the following structure was produced. HTL represents the hole transport layer, and the thickness in parentheses represents the film thickness (nm).
ITO(100)/PTPD1:PPBI(20)/NPD(10)/T4DBFHPB(10)/mCBP: x wt% 4CzIPN(30)/DBT-TRZ(10)/DPB: 20 wt% Liq(40)/Libbpp( 1)/Al(100)
x=10, 15 or 20 wt%
The results of device characteristics are shown in Table 6 and FIGS. 13(a) to 13(f).

(3) Sky blue TADF element A sky blue TADF element having the following structure was produced. HTL represents the hole transport layer, and the thickness in parentheses represents the film thickness (nm).
ITO(100)/PTPD1:PPBI(20)/NPD(10)/T4DBFHPB(10)/mCBP:x wt% 5TCzBN(30)/DBT-TRZ(10)/DPB:20 wt% Liq(40)/Libpp( 1)/Al(100)
x=10, 20, 30 or 40 wt%
The results of device characteristics are shown in Table 7 and FIGS. 14(a) to 14(f).

The voltage was lowered as the doping concentration was increased. It is considered that this is because the higher the doping concentration, the easier the electrons directly enter the dopant. Although the external quantum efficiency decreased a little as the doping concentration increased, the device life increased as the doping concentration increased. In particular, as a result of a brightness acceleration test with a device life of 20 wt %, T4DBFHPB showed an extremely long device life with a brightness half life of 28,000 hours at an initial brightness of 1,000 cdm ⁻² .

1 substrate 2 electrode 1
3 Hole Injection Transport Layer 4 Hole Transport Layer 5 Light Emitting Layer 6 Hole Blocking Layer 7 Electron Transport Layer 8 Electrode 2

Claims (5)

Arylamine derivative represented by the following general formula (1)
(In the general formula (1), R ^{1 to} R ⁷ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a linear or branched alkoxy group having 1 to 6 carbon atoms. A group or a linear or branched mono- or di-alkylamino group having 1 to 6 carbon atoms,
X is an oxygen atom, a sulfur atom or an alkylene group ^{(-CR 8 R 9 - (R} 8 and R ⁹ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, straight-chain or A branched alkoxy group having 1 to 6 carbon atoms, or a linear or branched mono- or di-alkylamino group having 1 to 6 carbon atoms)).
Ar is a substituent represented by the following general formula (2).
(In the general formula (2), R ^{10 to} R ³⁷ are a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkoxy group having 1 to 6 carbon atoms, or It is a linear or branched mono- or di-alkylamino group having 1 to 6 carbon atoms.)). The arylamine derivative according to claim 1, wherein in the general formula (1), X is an oxygen atom or a sulfur atom. The arylamine derivative according to claim 2, wherein R ^{1 to} R ³⁷ in the general formula (1) are hydrogen atoms or phenyl groups. A hole transport material comprising the arylamine derivative according to claim 1. An organic EL device using the arylamine derivative according to claim 1.