JP2018127402A - Novel benzofuropyrimidine compound, and organic el element prepared therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel benzofuropyrimidine compound that has excellent heat resistance and achieves the improved efficiency and life of a deep red phosphorescence organic EL element, and an organic EL element prepared therewith.SOLUTION: The present invention provides a benzofuropyrimidine compound represented by formula (1) (A is formula (2),(3)).SELECTED DRAWING: None

Description

  The present invention relates to a novel benzofuropyrimidine compound having high luminous efficiency, and an organic EL device using the same.

A liquid crystal display (LCD) is used for a small and medium-sized display device. However, since it is basically a light emitting / receiving type from a backlight, the configuration of the display for extracting light is complicated.
In contrast, organic electroluminescence displays (OLEDs) are self-luminous, do not require a backlight like LCDs, are simple in structure, can be made thinner and lighter, and are therefore portable display means. Suitable as
Furthermore, organic electroluminescence has been attracting attention as a light source element for several years, and research related to lighting using organic electroluminescence emission has been made for practical application throughout the country and abroad. Recently, it has become possible to produce a curved light source by depositing or applying an organic electroluminescent material on a plastic substrate. The use of display lighting using OLED is also being promoted in museums and the like, because light emission by organic electroluminescence does not emit ultraviolet rays that affect the exhibits.

When organic electroluminescence is used as a display, a material suitable for extracting three primary colors (blue, green, red) of light is important. For example, 4,4′-bis [2,2- Bis (4-methylphenyl) ethenyl] -1,1′-biphenyl (DTVBi) is a green fluorescent material such as tris (8-hydroxyquinolinolato) aluminum (Alq ₃ ) or tris [2-phenylpyridy]. inert -C ^2, N] iridium (III) is, as the red fluorescent material, 4- (dicyanomethylene) -2-t-butyl-6- (1,1,7,7-tetramethyljulolidyl -9 A pyran compound such as -ethenyl) -4H-pyran (DCJTB) is 2,3,7,8,12,13,17,18-octaethyl-21H, 23 as a red phosphorescent material. - and porphyrin platinum complex [Pt (OEP)] it is known.

Recently, attention has been focused on light sources for plant cultivation. Open-air cultivation is generally used for plant cultivation, but indoor cultivation is promoted as a means of avoiding salt damage and radioactive contamination due to the tsunami of the Great East Japan Earthquake with the assistance of the relevant ministries and agencies. Under such circumstances, construction of a plant factory for producing plants indoors has been promoted by entry from different industries. Some plant factories use sunlight and others use artificial light. As light sources of artificial light, fluorescent lamps, HID lamps, and LED lamps are generally used.
However, fluorescent lamps are in a direction to be deceived by national measures and emit light in a wide range from ultraviolet to infrared together with HID lamps, so they are not efficient for plant cultivation. Moreover, although the LED lamp can take out single light required for cultivation, since it is a point light source, in order to illuminate the whole cultivation area | region, it is necessary to arrange | position many light sources, and wiring and a drive device become complicated. For this reason, the equipment becomes larger than necessary, and installation is restricted.
On the other hand, since the organic electroluminescence light source is a planar light emitter, it can be easily configured to illuminate a required area by singly or connecting a plurality of them, and even for a larger area, Roll to Roll It can be manufactured by applying a printing technique based on the method (Non-Patent Document 1).

  Plants grow by photosynthesis, but the wavelength regions that can be absorbed by chlorophylls possessed by plants are blue of 430 nm to 460 nm and red of 645 nm to 665 nm. Therefore, blue and red light is necessary for plant cultivation. Plants also absorb near-infrared light of 680 nm or more, but a phenomenon called red drop occurs, and the efficiency of photosynthesis sharply decreases. In order to suppress this, when light of about 650 nm is irradiated at the same time, the light absorption effect of chlorophyll contained in the plant becomes very high as compared with the case where each is irradiated alone. This is generally called the Emerson effect (Non-Patent Document 2). Therefore, it is necessary to develop a red light emitting element that emits light at around 650 nm in organic electroluminescence.

As an example of an organic electroluminescence element emitting in 600 nm or more in the red or near infrared region, a bis (2,3-diphenylquinoxaline) iridium (acetylacetonato) complex [(QH) ₂ having an emission maximum at 680 nm. There is an element using Ir (acac)] having an external quantum efficiency of 10.2% at 600 cd / m ² (Non-patent Document 3).
In addition, an element using a 5,10,15,20-tetraphenyl-21H, 23H-tetrabenzoporphyrin platinum complex [Pt (tpbp)] having an emission maximum at 765 nm and an external quantum at 0.1 mA / cm ² . Some have an efficiency of 6.3% (Non-Patent Document 4).
In addition, an element using a 2,3-dicyanopyrazinophenanthrene compound (TPA-DCPP) showing an emission maximum at 708 nm, the external quantum efficiency when the doping amount is set to 20% is 9.8%. There is a thing (nonpatent literature 5).
In addition, an element using 2,3-bis [4 ′-(diphenylamino)-(1,1′-biphenyl) -4-yl] fumaronitrile (TPATCN), which exhibits an emission maximum at 670 nm, has an external quantum efficiency of There is 2.58% (Non-Patent Document 6).
However, although all of the above compounds have emission maxima at 600 nm or more, they are insufficient for practical use in terms of efficiency, characteristics and effects, and further development of compounds and optimization for device application are necessary. It is.

Konica Minolta Holdings, Inc. website, http: // www. konicaminolta. jp / about / release / 2010 / 0412_01_01. html Japanese Society of Plant Physiology, http: // jspp. org / H. Fujii, H .; Sakurai, K .; Tani, K .; Wakisaka and T.W. Hirao, IEICE Electronics Express, 2005, 2 (8), 260-266. C. Borek, et al. , Angew. Chem. 2007, 119, 1277-1130 S. Wang et al. , Angew. Chem. Int. Ed. 2015, 54, 13068-13072 X. Han et al. , Adv. Funct. Mater. DOI: 10.1002 / adfm. 2015503344.

  It is an object of the present invention to provide a benzofuropyrimidine compound having excellent heat resistance and realizing high efficiency, low voltage and long life of a deep red phosphorescent organic EL device, and an organic EL device using the same. And

The present invention comprises the following items.
The benzofuropyrimidine compound of the present invention is represented by the following general formula (1), and is characterized in that the triplet energy (E _T ) level is higher than 2.5 eV.

In General Formula (1), R ¹ and R ² each independently represent a hydrogen atom, an aliphatic substituent or an aromatic substituent, n represents an integer of 1 or more, and A represents General Formula (2) or In the general formula (2), X ¹ represents —CH or N. In the general formula (3), X ² represents —CH ₂ —, —S—, —O—, —NH— or —Si— is represented.
In the general formula (1), A is a substituent represented by the general formula (3), and in the general formula (3), X is preferably —S— or —O—.
In the general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an aromatic substituent, n is an integer of 1 to 3, and A is a substituent represented by the general formula (3) Further, in the general formula (3), X ² is preferably —S— or —O—.
The organic EL device of the present invention is characterized by containing the benzofuropyrimidine compound.

The benzofuropyrimidine compound of the present invention is excellent in heat resistance and realizes high efficiency, low voltage, and long life of the deep red phosphorescent organic EL device.
Use of such a benzofuropyrimidine compound particularly contributes to high performance of phosphorescence using triplet excitons or a thermally activated organic EL device.

FIG. 1 shows a ¹ HNMR spectrum (a) and a mass spectrum (b) of DBTBFPm. FIG. 2 shows the ¹ HNMR spectrum (a) and the mass spectrum (b) of DBFBFPm. FIG. 3 shows a ¹ HNMR spectrum (a) and a mass spectrum (b) of CzBFPm. FIG. 4 shows the UV-vis absorption spectrum (a) and PL spectrum (b) of the NPD vapor deposition film, the DBTBFPm vapor deposition film, and the DBTBFPm: NPD co-deposition film, respectively. FIG. 5 shows the UV-vis absorption spectrum (a) and the PL spectrum (b) of the NPD vapor deposition film, the DBFBFPm vapor deposition film, and the DBFBFPm: NPD co-deposition film, respectively. FIG. 6 shows UV-vis absorption spectrum (a) and PL spectrum (b) of an NPD vapor deposition film, a CzBFPm vapor deposition film, and a CzBFPm: NPD co-deposition film, respectively. FIG. 7 is a schematic cross-sectional view schematically showing the structure of the organic EL element of the present invention. The numbers in parentheses represent the film thickness (nm). FIG. 8 is an energy diagram of the element configuration of Example 2. FIG. 9 shows the voltage-current density relationship of the device of Example 2. FIG. 10 shows the voltage-luminance relationship of the element of Example 2. FIG. 11 shows the relationship between the voltage of the device of Example 2 and the external quantum efficiency. FIG. 12 shows an EL emission spectrum of the device of Example 2. FIG. 13 shows the element lifetime of the element of Example 2 (initial luminance L ₀ = 160 cdm ⁻² ).

Hereinafter, the present invention will be described in detail.
[Benzofuropyrimidine compounds]
The benzofuropyrimidine compound of the present invention is represented by the following general formula (1), and is characterized in that the triplet energy (E _T ) level is higher than 2.5 eV.

In General Formula (1), R ¹ and R ² each independently represent a hydrogen atom, an aliphatic substituent or an aromatic substituent, n represents an integer of 1 or more, and A represents General Formula (2) or In the general formula (2), X ¹ represents —CH or N. In the general formula (3), X ² represents —CH ₂ —, —S—, —O—, —NH— or —Si— is represented.

The aliphatic substituent includes a hydrocarbon group having 1 to 20 carbon atoms, specifically, an alkyl group having 1 to 20 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, a t-butyl group, and an isobutyl group. A part of the hydrogen atoms constituting the aliphatic substituent and the alkyl group may be substituted with a nitrogen atom, an oxygen atom, a sulfur atom or the like within a range not impairing the effects of the present invention.
Of these, the aliphatic substituent of R ¹ is preferably a methyl group, an ethyl group, a propyl group, a 2-propyl group, a butyl group, an isobutyl group, or a t-butyl group, and the aliphatic substituent of R ² is , Methyl group, ethyl group, propyl group, 2-propyl group, butyl group, isobutyl group and t-butyl group are preferred.
Aromatic substituents include aromatic substituents having 6 to 22 carbon atoms, specifically phenyl, biphenyl, naphthyl, anthracenyl, phenanthrenyl, triphenylenyl, and terphenyl groups. . Among these, a phenyl group, a biphenyl group, a terphenyl group, and a triphenylenyl group are preferable. Some of the hydrogen atoms constituting the aromatic substituent, within a range that does not impair the effects of the present invention, a nitrogen atom, an oxygen atom, a sulfur atom, etc. Among these may be substituted with, for R ¹ aromatic The group substituent is more preferably a phenyl group, a biphenyl group, and a terphenyl group, and the aromatic substituent of R ² is more preferably a phenyl group, a biphenyl group, or a terphenyl group.
n is an integer of 1 or more, specifically, an integer of 1 to 3.
A represents a substituent represented by the general formula (2) or (3). In the general formula (2), X ¹ represents -CH or N, in the general formula (3), X ² is _{-CH 2 -, - S -,} - O -, - represents a NH- or -Si-.

Specifically, the substituent represented by the general formula (2) or (3) is preferably the following substituent.

  The benzofuropyrimidine compound represented by the general formula (1) is preferably a compound represented by the following structural formula.

The benzofuropyrimidine compound has a π-conjugated system. 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 a dye. Furthermore, the energy gap can be adjusted by appropriately adding functional groups to such molecules to change the electronic properties. That is, in the present invention, a singlet excited state (E _S1 ) and a triplet excited state are obtained by designing the benzofuropyrimidine compound so that the triplet energy (E _T ) level is higher than 2.5 eV. The energy gap with (E _T1 ) becomes sufficiently small, and the energy once transferred to the triplet excited state can be returned to the singlet excited state again, so that highly efficient fluorescence can be extracted.

The benzofuropyrimidine compound of the present invention is a compound that has a 5% weight decay temperature (T _d5 ) of 400 to 440 ° C. and excellent heat resistance, and emits light in deep red (380 to 500 nm). Furthermore, since the benzofuropyrimidine compound can stably maintain a π-conjugated system, it can exhibit long-life deep red light emission.

[Method for producing benzofuropyrimidine compound]
The benzofuropyrimidine compound of this invention can be manufactured by the method shown below, for example. A method for producing DBTBFPm is shown as an example.

ジベンゾチオフェン−４−ボロン酸（ＤＢＴＢ（ＯＨ）₂）及び８−ブロモ−２−フェニルベンゾフロ［３，２−ｄ］ピリミジンを、Ｐｄ₂（ｄｂａ）₃触媒及びＳ−Ｐｈｏｓ配位子の存在下、炭酸カリウムを作用させてクロスカップリング反応を行うことにより、ＤＢＴＢＦＰｍを収率９０％で得る。
ただし、上記一般式（１）で表されるベンゾフロピリミジン化合物は、上記した方法に限られず、種々の公知の方法で製造することができる。

Dibenzothiophene-4-boronic acid (DBTB (OH) ₂ ) and 8-bromo-2-phenylbenzofuro [3,2-d] pyrimidine, Pd ₂ (dba) ₃ catalyst and presence of S-Phos ligand Then, DBTBFPm is obtained in a yield of 90% by performing a cross-coupling reaction by allowing potassium carbonate to act.
However, the benzofuropyrimidine compound represented by the general formula (1) is not limited to the above-described method, and can be produced by various known methods.

[Organic EL device]
The organic EL device of the present invention is characterized by containing the benzofuropyrimidine compound.
Here, FIG. 7 shows a typical layer structure of the organic EL element.
The organic EL element typically has, for example, an ITO film formed on the substrate 1 as the anode 2, and a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, and an electron transport layer formed thereon. 6, the electron injection layer 7 and the cathode 8 are laminated in this order.

  The substrate 1 is transparent and smooth and has a total light transmittance of at least 70%. Specifically, the substrate 1 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.

Thin films such as the anode 2, the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the electron transport layer 6, the electron injection layer 7 and the cathode 8 formed on the substrate are laminated by a vacuum deposition method or a coating method. Is done. When using a vacuum vapor deposition method, the deposited material is usually heated in an atmosphere reduced to 10 ⁻³ Pa or lower. The thickness of each layer varies depending on the type of layer and the material used, but usually the anode 2 and the cathode 8 are about 100 nm, and the other layers including the light emitting layer 5 are less than 50 nm. The electron injection layer 7 or the like may be formed with a thickness of 1 nm or less, for example.

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

In the light emitting layer 5, like the other light emitting layers used in the organic EL device, it is preferable to use a host compound together with the benzofuropyrimidine compound which is the light emitting material of the present invention. Examples of the host compound include bis [2- (diphenylphosphino) phenyl] ether oxide (DPEPO), PO9, 4,4′-bis (N-carbazolyl) -1,1′-biphenyl (CBP), 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) and the like. In the components constituting the light emitting layer 5, the content of the light emitting material (benzofuropyrimidine compound) and the host compound of the present invention is 1 to 50 wt%, preferably 5 to 10 wt%.
In addition, a dopant such as (DPQ) ₂ Ir (dpm) (bis (2,3-diphenylquinosaline) iridium (dipivaloylmethane)) may be added to the light emitting layer.

  In order to efficiently transport holes from the anode 2 to the light emitting layer, a hole transport layer 4 is provided between the anode 2 and the light emitting layer 5. Examples of the hole transport material forming the hole transport layer 4 include TAPC, N, N′-diphenyl-N, N′-di (m-tolyl) benzidine (TPD), N, N′-di (1 -Naphthyl) -N, N′-diphenylbenzidine (α-NPD), 1,3-di (carbazolyl-9-yl) benzene) (mCP) and 4,4 ′, 4 ″ -tris [phenyl (m- Tolyl) amino] triphenylamine and the like.

  An electron transport layer 6 is provided between the cathode 8 and the light emitting layer 5 in order to efficiently transport electrons from the cathode to the light emitting layer. Examples of the electron transport material forming the electron transport layer 6 include 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) -1,3,4-oxadi Azole (tBu-PBD), 1,3-bis [5- (4-t-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), bathocuproin (BCP), 1,4-bis (1,10-phenanthrolin-2-yl) ) Benzene (D B), 1,3,5-tris (1-phenyl--1H- benzimidazol-2-yl) benzene (TPBi), and the like.

  As the cathode 8, a cathode having a low work function (4 eV or less) and chemically stable is used. Specifically, a cathode material such as Al, 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, resistance heating vapor deposition, electron beam vapor deposition, sputtering, or ion plating. The thickness of the cathode is usually 10 nm to 1 μm, preferably 50 to 500 nm.

  Of the hole transport layer 4 and the electron transport layer 6, a layer having a function of improving the charge injection efficiency from the anode 2 or the cathode 8, respectively, and exhibiting an effect of lowering the driving voltage of the organic EL element, A hole injection layer 3 and an electron injection layer 7 may be provided.

  Examples of the hole injection material for forming the hole injection layer 3 include phthalocyanine complexes such as copper phthalocyanine, N, N′-bis [4- (di-m-methylphenylenylamino) phenyl] -N, N. '-Di-phenyl-1,1'-biphenyl-4,4'-diamine (DNTPD), 4-isopropyl-4'-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate (PPBI) or 4,4', 4 "Aromatic amine derivatives such as -tris (3-methylphenylphenylamino) triphenylamine, hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having amino groups, and polythiophene. The film thickness of the hole injection layer 3 is usually 5 to 300 nm.

Examples of the electron injection material for forming the electron injection layer 7 include Ba, Ca, CaF, LiF, Li, and NaF in addition to 8-hydroxyquinolinolato-lithium (Liq). The film thickness of the electron injection layer 7 is usually 3 to 50 nm.
In addition, layers such as a hole blocking layer, an electron blocking layer, and an exciton blocking layer are further formed as necessary.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.

[Synthesis of benzofuropyrimidine derivatives]
The equipment and measurement conditions used for product identification are as follows.
(1) ¹ H nuclear magnetic resonance (NMR) apparatus JEOL Ltd. (400 MHz) JNM-EX270FT-NMR type (2) mass spectrometry (MS) apparatus JEOL Ltd. JMS-K9 [desktop GCQMS] and Zspray (SQ detector 2) manufactured by Waters
(3) Elemental analyzer Perkin Elmer 2400II CHNS / O analyzer Measurement mode: CHN mode

[Example 1]
Synthesis Example 1 Synthesis of 8- (3- (dibenzo [b, d] thiophen-4-yl) 2-phenylbenzofuro [3,2-d] pyrimidine (DBTBFPm)

In a four-necked flask, DBTB (OH) ₂ 2.05 g (6.76 mol), 8-bromo-2-phenylbenzofuro [3,2-d] pyrimidine 2.0 g (6.15 mol), K ₂ CO ₃ 1.7 g (12.3 mmol) ), 50 mL of 1,4-dioxane was added, and nitrogen bubbling was performed for 1 hour. Pd ₂ (dba) ₃ 0.11 g (0.12 mmol) and S-Phos 0.10 g (0.24 mmol) were added, and the mixture was heated to reflux under a nitrogen flow. After 30 minutes, the disappearance of the spot of the raw material was confirmed by TLC, so the reaction was stopped. The reaction solution was washed with saturated brine and extracted with chloroform. The organic layer was recovered and dispersed and washed with a large amount of methanol. The back product after filtration was collected and subjected to hot filtration with toluene. The filtrate was collected and dried under reduced pressure. A white solid was obtained (yield 3.06 g, yield 90%).
^{The 1} H-NMR spectrum is shown in FIG. 1 (a), and the MS results are shown in FIG. 1 (b).
The results of elemental analysis are as follows (numbers in parentheses are theoretical values).
Carbon: 80.81 (80.93), Hydrogen: 3.92 (4.00)
Nitrogen: 5.55 (5.53), Sulfur: 6.15 (6.35)
Oxygen: (3.17)

Synthesis Example 2 Synthesis of 8- (3- (dibenzo [b, d] furan-4-yl) 2-phenylbenzofuro [3,2-d] pyrimidine (DBFBFPm)

In a four-necked flask, DBFB (OH) ₂ 1.9 g (6.76 mol), 8-bromo-2-phenylbenzofuro [3,2-d] pyrimidine 2.0 g (6.15 mol), K ₂ CO ₃ 1.7 g (12.3 mmol) ), 50 mL of 1,4-dioxane was added, and nitrogen bubbling was performed for 1 hour. Pd ₂ (dba) ₃ 0.11 g (0.12 mmol) and PCy ₃ 0.07 g (0.24 mmol) were added, and the mixture was heated to reflux under a nitrogen flow. After 30 minutes, the disappearance of the spot of the raw material was confirmed by TLC, so the reaction was stopped. The reaction solution was washed with saturated brine and extracted with chloroform. The organic layer was recovered and dispersed and washed with a large amount of methanol. The back product after filtration was collected and subjected to hot filtration with toluene. The filtrate was collected and dried under reduced pressure. A white solid was obtained (yield 1.2 g, yield 36%).
The measurement result of ¹ H-NMR spectrum is as follows.
¹ H-NMR (400 MHz, CHLOROFORM-D) δ 9.10 (s, 1H), 8.65 (d, J = 2.3 Hz, 1H), 8.61-8.56 (m, 2H), 8.30-8.16 (1H), 8.14- 7.90 (m, 4H), 7.78 (dd, J = 8.2, 2.7 Hz, 2H), 7.73-7.61 (m, 3H), 7.57-7.45 (m, 5H), 7.38 (t, J = 7.6 Hz, 1H)
^{The 1} H-NMR spectrum is shown in FIG. 2 (a), and the MS results are shown in FIG. 2 (b).
The results of elemental analysis are as follows (numbers in parentheses are theoretical values).
Carbon: 83.47 (83.59), Hydrogen: 3.83 (4.13)
Nitrogen: 5.72 (5.73), Oxygen: (6.55)

(Synthesis Example 3) Synthesis of CzBFPm

In a four-necked flask, CzB (OH) ₂ 1.94 g (6.76 mol), 8-bromo-2-phenylbenzofuro [3,2-d] pyrimidine 2.0 g (6.15 mol), K ₂ CO ₃ 1.7 g (12.3 mmol) ), 50 mL of 1,4-dioxane was added, and nitrogen bubbling was performed for 30 minutes. Pd ₂ (dba) ₃ 0.11 g (0.12 mmol) and PCy ₃ 0.07 g (0.24 mmol) were added, and the mixture was heated to reflux under a nitrogen flow. Since the disappearance of the spot of the raw material was confirmed by TLC, the reaction was stopped. The reaction solution was washed with saturated brine and extracted four times with 10 ml of chloroform. The organic layer was collected, dried over magnesium sulfate, filtered, and the filtrate was concentrated. The obtained fraction was heated and dissolved in toluene and subjected to hot filtration using silica gel. The filtrate was collected, concentrated and dried under reduced pressure. A white solid was obtained. (Yield 1.68g, Yield 56%)
The measurement result of ¹ H-NMR spectrum is as follows.
¹ H-NMR (400 MHz, CHLOROFORM-D) δ 9.10 (s, 1H), 8.68-8.49 (m, 3H), 8.26-8.08 (m, 2H), 7.99 (dd, J = 8.7, 2.3 Hz, 1H ), 7.92 (t, J = 1.8 Hz, 1H), 7.83 (d, J = 7.8 Hz, 1H), 7.75 (t, J = 8.0 Hz, 2H), 7.64-7.59 (m, 1H), 7.56-7.42 (m, 7H), 7.35-7.29 (m, 2H)
^{The 1} H-NMR spectrum is shown in FIG. 3 (a), and the MS results are shown in FIG. 3 (b).
The results of elemental analysis are as follows (numbers in parentheses are theoretical values).
Carbon: 83.81 (83.76), Hydrogen: 4.16 (4.34)
Nitrogen: 8.59 (8.62), Oxygen: (3.28)

(Evaluation of various characteristics)
For thermal analysis of DBTBFPm, DBFBFPm, and CzBFPm (hereinafter also referred to as “BFPm” or “BFPm derivative”) obtained in Synthesis Examples 1 to 3, TGA diamond and DSCDTA manufactured by PerkinElmer Japan Co., Ltd. were used.
The results are shown in Table 1.

Next, in order to measure various characteristics of these benzofuropyrimidine derivatives, a host material single film (thickness 40 nm) and a co-deposited film with NPD were prepared by a resistance heating vapor deposition method using a vacuum integrated vapor deposition apparatus.
About the said single film | membrane, UV-vis absorption spectrum was measured using the ultraviolet-visible (UV-vis) spectrophotometer UV-3150 made from Shimadzu Corporation, and Fluoro Max-4 made from Horiba Ltd. was measured. Used to measure the photoluminescence (PL) spectrum. The results are shown in FIGS.
From the α-NPD: BFPm (1: 1) co-deposited film, different results from the respective photoluminescence regions were obtained, and thus both formed an exciplex, and it was considered that the photoluminescence was observed. It is done.

The ionization potential (Ip) of the single film was measured in vacuum using a photoelectron yield (PYS) apparatus manufactured by Sumitomo Heavy Industries, Ltd.
Furthermore, since the organic EL element is an all-solid-state light-emitting element, optical characteristics in the solid state are important. According to the measurement result, the energy gap (Eg) is estimated from the absorption edge of the UV-vis absorption spectrum. The electron affinity (Ea) can be calculated by subtracting Eg from Ip.
Table 2 shows the results of ionization potential (Ip), electron affinity (Ea), and energy gap (Eg) of DBT-TRZ.

[Example 2]
Since the photoluminescence of the α-NPD: DBTBFPm (1: 1) co-deposited film (thickness 30 nm) formed an exciplex on the long wavelength side, the deep red phosphorescent material Ir (DPQ) ₂ (dpm) The overlap with the triplet exciplex ( ³ MLCT) is large, and an efficient energy transfer from the exciplex to the light emitting material can be expected. Therefore, an organic EL device using an exciplex host (α-NPD: BFPm derivative) as a light emitting layer was produced.
The layer structure of the organic EL element is as follows (see FIG. 7), and x: y of the light emitting layer corresponds to the mixing ratio (weight ratio) of α-NPD and BFPm derivative. Note that the light emitting layer was doped with 1 wt% of Ir (DPQ) ₂ (dpm). The number in parentheses is the film thickness.
ITO (anode) / DNTPD: PPBI (20 nm) (hole injection layer) / α-NPD (20 nm) (hole transport layer) / α-NPD: BFPm derivative = x: y [1 wt% Ir (DPQ) ₂ (dpm) Dope] (40 nm) (light emitting layer) / BFPm derivative (20 nm) (light emitting layer) / DPB (30 nm) (electron transport layer) / DPB: 20 wt% Liq (20 nm) (electron injection layer) / Liq (1 nm) (electrons Injection layer) / Al (cathode)
The chemical structure of the main materials used is as follows.

An energy diagram of the element configuration is shown in FIG.
FIG. 9 shows the voltage-current density characteristics of the fabricated device, FIG. 10 shows the voltage-luminance characteristics, FIG. 11 shows the luminance-external quantum efficiency characteristics, FIG. 12 shows the EL emission spectrum, and FIG. , Respectively.
When a host material of α-NPD / DBTBFPm (1 wt% Ir (DPQ) ₂ (dpm) dope) is used for the light emitting layer, the device is 6.8 V at 1 cd / m ² and external quantum efficiency is 16.7. % (Fig. 11), 100 cd / m ² , 11.6 V (Fig. 9), external quantum efficiency 15.3% (Fig. 11), 1000 cd / m ² , 15.1 V (Fig. 9), external quantum efficiency 13.2% ( The high efficiency of FIG. 11) was realized.
In addition, at 7.75 mA / cm ² (equivalent to 160 cd / m ² @CIE (0.71, 0.28)), 70% luminance decay life was over 500 hours. [S1]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Electron injection layer 8 Cathode

Claims (4)

A benzofuropyrimidine compound represented by the following general formula (1), wherein the triplet energy (E _T ) level is higher than 2.5 eV.

(In General Formula (1), R ¹ and R ² each independently represent a hydrogen atom, an aliphatic substituent or an aromatic substituent, n represents an integer of 1 or more, and A represents General Formula (2). Or a substituent represented by (3),
In the general formula (2), X ¹ represents —CH or N,
In the general formula (3), X ² represents —CH ₂ —, —S—, —O—, —NH— or —Si—. ) In the general formula (1),
The benzofuropyrimidine compound according to claim 1, wherein A is a substituent represented by the general formula (3), and in the general formula (3), X ² is -S- or -O-. In the general formula (1),
R ¹ and R ² each independently represents a hydrogen atom or an aromatic substituent,
n is an integer of 1 to 3,
The benzofuropyrimidine according to claim 1 or 2, wherein A is a substituent represented by the general formula (3), and in the general formula (3), X ² is -S- or -O-. Compound.   The organic EL element containing the benzofuropyrimidine compound as described in any one of Claims 1-3.

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