JP2024007687A - Organic light-emitting element using new material and method for extending life of organic light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-life organic light-emitting element containing a novel compound in a light-emitting layer.

SOLUTION: A light-emitting layer of an organic light-emitting element includes a novel compound represented by the following formula (I). Further, by using the compound as a host compound in the light emitting layer of the organic light emitting element, the device life of the organic light emitting element can be extended.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an organic light emitting device using a novel material. The present invention also relates to a method for improving the lifetime of an organic light emitting device.

2. Description of the Related Art Research on organic light-emitting devices such as organic electroluminescent devices (organic EL devices) is actively being conducted.
Organic light-emitting materials are known that have the function of emitting light (fluorescence) in response to a certain type of energy stimulation. At this time, light emission using electrical energy as an energy source is called electroluminescence, and an organic light emitting device using this is called an organic EL device. Organic EL elements with various configurations are known, and the device structure of a simple organic EL element includes at least an anode, a cathode, and various layers such as a light emitting layer between the anode and the cathode on a substrate. It contains an organic layer containing.

Compounds having various structures have been proposed so far as being usable in organic layers such as light-emitting layers of organic EL devices (Patent Documents 1 to 3).
Various attempts have been made to improve the device lifetime of such organic light emitting devices.
For example, it is known that the device life can be extended by using a compound having a structure having a twisted aryl substituted with a bulky alkyl as a light-emitting dopant compound contained in the light-emitting layer (Patent Document 4) ). In addition, in organic light-emitting devices containing thermally activated delayed fluorescence (TADF) material in the light-emitting layer, we are optimizing the device structure. It is also known that the device life can be extended by inserting the film with a film thickness of (Non-Patent Document 1). Furthermore, it has been reported that the durability of a light emitting element is improved by replacing all the hydrogen in the light emitting material compound in the organic layer with deuterium (Non-Patent Documents 2 to 4).

International Publication No. 2021/166552 International Publication No. 2021/166553 China Patent Publication No. 104560018 Japanese Patent Application Publication No. 2016-155858

Scientific Reports volume 6, Article number: 22463 (2016) Taiyo Nippon Sanso Technical Report No.32 pp.5-8(2013) Wako Organic Square, No.36 pp.2-3 https://www.bunsekik.com/Organic EL news/Past news/Deuterium-substituted fluorescent material - Will it become the mainstream of next-generation blue materials?/

The present application aims to provide an organic light emitting device using a new material with a specific structure and improved device lifetime. It is also an object of the present invention to provide a novel method for improving the lifetime of organic light emitting devices.
The compound represented by formula (I), which will be described in detail below, was discovered for the first time by the present inventors. By using such a compound as a host compound in the light-emitting layer of an organic light-emitting device, the device life of the organic light-emitting device can be extended (improved device life).

（ここで、Ｒはフェニレン基を表し、
ジベンゾフラン骨格の水素原子は、１または複数の置換または非置換のアルキル基、シクロアルキル基、アリール基、またはヘテロアリール基で置換されていてもよい。）
［２］有機発光素子であって、発光層に含まれる式（Ｉ）で示される化合物が

である、［１］の有機発光素子。
［３］下記式（Ｉ）で示される、有機発光素子用ホスト化合物。

（ここで、Ｒはフェニレン基を表し、
ジベンゾフラン骨格の水素原子は、１または複数の置換または非置換のアルキル基、シクロアルキル基、アリール基、またはヘテロアリール基で置換されていてもよい。） Specifically, it includes the following aspects.
[1] An organic light-emitting device, the light-emitting layer containing a compound represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. )
[2] An organic light-emitting device, in which the compound represented by formula (I) contained in the light-emitting layer is

The organic light emitting device according to [1].
[3] A host compound for organic light emitting devices, represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. )

である、［３］の有機発光素子用ホスト化合物。
［５］下記式（Ｉ）で示される化合物。

（ここで、Ｒはフェニレン基を表し、
ジベンゾフラン骨格の水素原子は、１または複数の置換または非置換のアルキル基、シクロアルキル基、アリール基、またはヘテロアリール基で置換されていてもよい。）
［６］式（Ｉ）で示される化合物が、

である、［５］の化合物。 [4] The compound represented by formula (I) is

The host compound for an organic light emitting device according to [3].
[5] A compound represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. )
[6] The compound represented by formula (I) is

The compound of [5].

（ここで、Ｒはフェニレン基を表し、
ジベンゾフラン骨格の水素原子は、１または複数の置換または非置換のアルキル基、シクロアルキル基、アリール基、またはヘテロアリール基で置換されていてもよい。） [7] A method for extending the life of an organic light emitting device using a compound represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. )

1 is a schematic cross-sectional view showing an example of a layer structure of an organic light emitting device.

The organic EL element will be explained again.
A typical organic EL device includes, on a substrate, at least an anode, a cathode, and an organic layer between the anode and the cathode. Examples of the organic layer include a light emitting layer, a hole transport layer, layer, hole injection layer, electron injection layer, electron transport layer, hole blocking layer, electron blocking layer, etc.
Although an example of a specific configuration of an organic EL device is shown in FIG. 1, the organic light emitting device of the present invention is not limited to such a configuration.
Each layer will be briefly explained below.

[substrate]
Preferably, the organic EL element is supported by a substrate.
There are no particular restrictions on this substrate, and any substrate that has been conventionally used in organic EL devices may be used, such as glass, transparent plastic, quartz, silicon, or the like.

[anode]
In some embodiments, the anode is fabricated from a metal, an alloy, a conductive compound, or a combination thereof. Examples include CuI, indium tin oxide (ITO), SnO ₂ and ZnO.
In some embodiments, the thickness of the anode is between 10 and 1,000 nm. In some embodiments, the thickness of the anode is 10-200 nm. In some embodiments, the thickness of the anode varies depending on the material used.

[cathode]
In some embodiments, the cathode is made of an electrode material such as an alloy, a conductive compound, or a combination thereof. Such materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium-copper mixtures, magnesium-silver mixtures, magnesium-aluminum mixtures, magnesium-indium mixtures, aluminum-aluminum oxide (Al ₂ O ₃ ) mixtures, indium. , lithium-aluminum mixture, and rare earth elements.
In some embodiments, the thickness of the cathode is between 10 nm and 5 μm. In some embodiments, the thickness of the cathode is between 50 and 200 nm.

[Light-emitting layer]
The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and cathode, respectively, and a light-emitting material may be used alone in the light-emitting layer. , preferably including a luminescent material and a host material.
When a host material is used, the amount contained in the light emitting layer is not particularly limited and can be 0.1% by weight to 99.9% by weight. It is more preferably 1% by weight or more, more preferably 50% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.
The host material in the light-emitting layer is an organic compound that has hole-transporting ability and electron-transporting ability, and/or a compound that prevents emitted light from increasing in wavelength, and/or an organic compound that has a high glass transition temperature. It is preferable that there be.
The compound of the present application is used as a host material, but the following can also be used as a host material. Host materials that can be used include, but are not limited to:

[Hole transport layer]
The hole transport layer includes a hole transport material. In some embodiments, the hole transport layer is a single layer. In some embodiments, the hole transport layer has multiple layers.
In some embodiments, the hole transport material has one of hole injection or transport properties and electron barrier properties. In some embodiments, the hole transport material is an organic material. In some embodiments, the hole transport material is an inorganic material.
Examples of hole transport materials include, but are not limited to, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, allylamines. derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers and conductive polymer oligomers (particularly thiophene oligomers), or combinations thereof. In some embodiments, the hole transport material is selected from porphyrin compounds, aromatic tertiary amine compounds, and styryl amine compounds. In some embodiments, the hole transport material is an aromatic tertiary amine compound.

The following can be used as hole transport materials, but are not limited to these:

[Electron transport layer]
The electron transport layer includes an electron transport material. In some embodiments, the electron transport layer is a single layer. In some embodiments, the electron transport layer has multiple layers.
In some embodiments, the electron transport material need only function to transport electrons injected from the cathode to the emissive layer. In some embodiments, the electron transport material also functions as a hole blocking material.
Examples of electron transport layers include, but are not limited to, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrane dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethanes, anthrone derivatives, oxadiazole derivatives, azole derivatives. , azine derivatives or combinations thereof, or polymers thereof. In some embodiments, the electron transport material is a thiadiazole derivative or a quinoxaline derivative. In some embodiments, the electron transport material is a polymeric material. (Furthermore, it is also possible to use a polymer material in which these materials are introduced into the polymer chain or in which these materials are used as the main chain of the polymer.

The following can be used as electron transport materials, but are not limited to these:

[Injection layer]
The injection layer is a layer provided between an electrode and an organic layer in order to reduce driving voltage and improve luminance, and includes a hole injection layer and an electron injection layer. It can be provided between the anode and the light emitting layer (hole transport layer) or between the cathode and the light emitting layer (electron transport layer), if necessary.
Preferred examples of compounds that can be used as hole injection materials are listed below, but the invention is not limited thereto.

Next, preferred examples of compounds that can be used as electron injection materials will be listed, but the invention is not limited to these.

[Barrier layer]
The barrier layer is a layer that can prevent charges (electrons or holes) and/or excitons present in the emissive layer from diffusing outside the emissive layer.
In some embodiments, an electron blocking layer is present between the emissive layer and the hole transport layer (in FIG. 1, between 4: hole transport layer and 5: emissive layer) so that electrons are This prevents the hole from passing through the layer to the hole transport layer. In some embodiments, the hole blocking layer is present between the emissive layer and the electron transport layer (in FIG. 1, between 5: the emissive layer and 6: the electron transport layer), so that holes are This prevents electrons from passing through the layer to the electron transport layer. In some embodiments, the barrier layer prevents excitons from diffusing outside the emissive layer. In some embodiments, the electron blocking layer and the hole blocking layer constitute an exciton blocking layer. As used herein, the term "electron blocking layer" or "exciton blocking layer" includes layers that have both the functionality of an electron blocking layer and of an exciton blocking layer.

[Electronic barrier layer]
The electron barrier layer transports holes. In some embodiments, during hole transport, the electron barrier layer prevents electrons from reaching the hole transport layer. In some embodiments, the electron blocking layer increases the probability of recombination of electrons and holes in the emissive layer. The material used for the electron barrier layer may be the same material as described above for the hole transport layer. Specific examples of preferred compounds that can be used as electron barrier materials are listed below, but the invention is not limited to these.

[Hole blocking layer]
The hole blocking layer functions as an electron transport layer. In some embodiments, during transport of electrons, the hole blocking layer prevents holes from reaching the electron transport layer. In some embodiments, the hole blocking layer increases the probability of recombination of electrons and holes in the emissive layer. The material used for the hole blocking layer may be the same material as described above for the electron transport layer.
Preferred examples of compounds that can be used in the hole blocking layer are listed below, but the invention is not limited thereto.

（ここで、Ｒはフェニレン基を表し、
ジベンゾフラン骨格の水素原子は、１または複数の置換または非置換のアルキル基、シクロアルキル基、アリール基、またはヘテロアリール基で置換されていてもよい。） The compound used in the light emitting layer of the organic light emitting device according to the present invention is a compound represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. )

The alkyl group that can substitute the dibenzofuran skeleton can be linear or branched, and the number of carbon atoms can be, for example, 1 or more, 2 or more, or 4 or more. Further, the number of carbon atoms can be 30 or less, 20 or less, 10 or less, 6 or less, or 4 or less. Specific examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, n-hexyl group, isohexyl group, Examples include, but are not limited to, 2-ethylhexyl group, n-heptyl group, isoheptyl group, n-octyl group, isooctyl group, n-nonyl group, isononyl group, n-decanyl group, and isodecanyl group. do not have.
The cycloalkyl group capable of substituting the dibenzofuran skeleton can be a monocyclic or condensed cycloalkyl group, and the number of carbon atoms thereof can be, for example, 1 or more, 2 or more, or 4 or more. Further, the number of carbon atoms can be 30 or less, 20 or less, 10 or less, 6 or less, or 4 or less. Specific examples include, but are not limited to, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. Note that those substituted with an adamantyl group are not related to the present invention.
Examples of aryl groups and heteroaryl groups that can substitute the dibenzofuran skeleton include monocyclic or condensed aryl groups and heteroaryl groups having 5 to 12 carbon atoms, and specifically, phenyl groups, Examples include, but are not limited to, a naphthyl group, an indenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a phenanthryl group, a triphenylenyl group, and a dibenzofuran group.
The alkyl group, cycloalkyl group, aryl group, or heteroaryl group that substitutes the hydrogen atom of the dibenzofuran skeleton may be further substituted with various substituents such as an alkyl group and a cyano group.
The alkyl group, cycloalkyl group, aryl group, or heteroaryl group substituting the hydrogen atom of the dibenzofuran skeleton can be one or more, and when there are multiple substituents, each group is They can be the same, or they can be different in number of carbon atoms, types of substituents, etc.

In the phenylene group of R in formula (I), the dibenzofuran ring may be located at any of the ortho, meta, and para positions of the carbazole ring. Phenylene can also be bonded to any position on the dibenzofuran ring.

The specific structure of the compound represented by formula (I) used in the organic light emitting device of the present invention is illustrated below. However, this is not intended to limit the compounds used in the organic light emitting device of the present invention.

として示される構造式は、ジベンゾフラン環のフェニル基上の置換可能な４つの水素原子のいずれか１つが、カルバゾール環のＮ原子に結合するフェニル基（メタ位）で置換されている化合物を集合的に示したもの（ジベンゾフラン環上の置換位置が異なる４つの化合物を一の構造式で示したもの）である。 In addition, in the above, for example,

The structural formula shown as collectively refers to compounds in which any one of the four substitutable hydrogen atoms on the phenyl group of the dibenzofuran ring is substituted with a phenyl group (meta position) bonded to the N atom of the carbazole ring. (four compounds with different substitution positions on the dibenzofuran ring are shown in one structural formula).

The compound represented by the above formula (I) can be produced, for example, by reacting a deuterium-substituted carbazole with a halogen-substituted dibenzofuran skeleton.

There is no particular restriction on the amount of the compound represented by formula (I) in the light emitting layer, but it is preferable that the amount of the compound represented by formula (I) in the light emitting layer is 0.1% by weight or more; More preferably, it is at least % by weight. Further, it can be present in the light emitting layer in an amount of 99% by weight or less.

The present invention also relates to extension (improvement) of the device life of an organic light emitting device using the compound represented by the above formula (I). As shown in the examples, the luminance of the device is measured at a specific current density, and confirmed by the length of time (LT95) until the initial emission intensity decreases by 5%.

The compound represented by the above formula (I) is preferably used as a host compound, particularly in the light emitting layer of an organic light emitting device, in combination with a compound that emits delayed fluorescence (delayed fluorescence compound).
Delayed fluorescence compounds that can be used together with the compound represented by formula (I) are listed below, but the delayed fluorescence compounds that can be used together with the compound represented by formula (I) are limited by the examples of these compounds. It cannot be interpreted literally.

Moreover, the compound represented by formula (I) can also be used in combination with a known delayed fluorescence compound other than those mentioned above. It is also possible to use it in combination with delayed fluorescent compounds that are currently unknown.
As delayed fluorescent compounds, for example, paragraphs 0008 to 0048 and 0095 to 0133 of WO2013/154064, and paragraph 000 of WO2013/011954.
7-0047 and 0073-0085, paragraphs 0007-0033 and 0059-0066 of WO2013/011955, paragraphs 0008-0071 and 0118-0133 of WO2013/081088, paragraphs 0009-0046 of JP2013-256490 and 0093-0134, paragraphs 0008-0020 and 0038-0040 of JP2013-116975, paragraphs 0007-0032 and 0079-0084 of WO2013/133359, paragraphs 0008-0054 and 0101- of WO2013/161437 0121, paragraphs 0007 to 0041 and 0060 to 0069 of JP2014-9352, paragraphs 0008 to 0048 and 0067 to 0076 of JP2014-9224, paragraphs 0013 to 0025 of JP2017-119663, Paragraphs 0013 to 0026 of JP 2017-119664, Paragraphs 0012 to 0025 of JP 2017-222623, Paragraphs 0010 to 0050 of JP 2017-226838, Paragraphs 0012 to 0043 of JP 2018-100411 , compounds included in the general formula described in paragraphs 0016 to 0044 of WO2018/047853, particularly exemplary compounds that emit delayed fluorescence. In addition, JP2013-253121, WO2013/133359, WO2014/034535, WO2014/115743, WO2014/122895, WO2014/126200, WO2014/136758, WO2 No. 014/133121 Publications, WO2014/136860, WO2014/196585, WO2014/189122, WO2014/168101, WO2015/008580, WO2014/203840, WO2015/002213, W O2015/016200 publication, WO2015/019725, WO2015/072470, WO2015/108049, WO2015/080182, WO2015/072537, WO2015/080183, JP2015-129240, WO20 Publication No. 15/129714, WO2015/129715, WO2015/133501, WO2015/136880, WO2015/137244, WO2015/137202, WO2015/137136, WO2015/146541, WO20 Described in Publication No. 15/159541 It is also possible to employ a luminescent material that emits delayed fluorescence. Note that the above-mentioned publications described in this paragraph are cited here as part of this specification.

Furthermore, in the light emitting layer of the organic light emitting device according to the present invention, in addition to the compound of formula (I) and the delayed fluorescent compound shown above, a fluorescent compound that does not emit delayed fluorescence can also be added. .
Examples of such fluorescent compounds are anthracene derivatives, tetracene derivatives, naphthacene derivatives, pyrene derivatives, perylene derivatives, chrysene derivatives, rubrene derivatives, coumarin derivatives, pyran derivatives, stilbene derivatives, fluorene derivatives, anthryl derivatives, pyrromethene derivatives, terphenyls. derivatives, terphenylene derivatives, fluoranthene derivatives, amine derivatives, quinacridone derivatives, oxadiazole derivatives, malononitrile derivatives, pyran derivatives, carbazole derivatives, julolidine derivatives, thiazole derivatives, derivatives containing metals (Al, Zn), etc. These exemplary skeletons may or may not have substituents. Furthermore, these exemplary skeletons may be combined. Fluorescent compounds are not limited to those mentioned above.

The organic light-emitting device according to the present invention is produced by vacuum evaporation (degree of vacuum: 1×10 ^-5 Pa) on a glass substrate on which an anode made of indium tin oxide (ITO) with a film thickness of 100 nm is formed, for example. , can be manufactured by laminating them in the following order. However, the type of compound used, the amount used, the thickness of the layer, etc. are not limited to the following, and other methods employed in the technical field can also be used.

(1) Form HAT-CN to a thickness of 10 nm on ITO.
(2) Form NPD to a thickness of 30 nm.
(3) TrisPCz was formed to a thickness of 10 nm.
(4) Form H1 to a thickness of 5 nm.
(5) H1, a delayed fluorescence compound, and a compound according to the present invention were co-deposited from different deposition sources to form a 40 nm thick light-emitting layer. (The contents of H1, the delayed fluorescence compound, and the compound according to the present invention are 64.5% by mass, 35.0% by mass, and 0.5% by mass, in order).
(6) SF3-TRZ was formed to a thickness of 10 nm.
(7) Liq and SF3-TRZ were co-deposited from different deposition sources to form a 30 nm thick layer. (The contents of Liq and SF3-TRZ are 30% by mass and 70% by mass, respectively).
(8) Form Liq to a thickness of 2 nm.
(9) Form a cathode by depositing aluminum (Al) to a thickness of 100 nm.

The structures of the various compounds used above are as follows.

EXAMPLES The present invention will be specifically explained below with reference to Examples.
Note that the materials, processing details, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the Examples specifically shown below.
Evaluation of the luminescent properties of organic light emitting devices is
・High performance UV-visible near-infrared spectrophotometer (PerkinElmer: Lambda950),
・Fluorescence spectrophotometer (Horiba, Ltd.: FluoroMax-4),
・Absolute PL quantum yield measurement device (Hamamatsu Photonics: C11347),
・Source meter (manufactured by Keithley: 2400 series),
・Semiconductor parameter analyzer (manufactured by Agilent Technologies: E5273A),
・Optical power meter measuring device (manufactured by Newport: 1930C),
・Optical spectrometer (Ocean Optics: USB2000),
・Spectroradiometer (manufactured by Topcon: SR-3) and ・Streak camera (model C4334, manufactured by Hamamatsu Photonics Co., Ltd.)
This was done using

窒素雰囲気化、2-(3-ブロモフェニル)ジベンゾフラン(16.8 g, 51.9 mmol)、カルバゾール-1,2,3,4,5,6,7,8-d8（10 g, 57.1 mmol)、トリス(ジベンジリデンアセトン)ジパラジウム(0)(4.75 g, 5.19 mmol)、トリ-tert-ブチルホスホニウムテトラフルオロボラート(3.01 g, 10.4 mmol)およびナトリウム tert-ブトキシド(9.97 g, 103.7 mmol)を330 mlのトルエンに加え、２４時間還流した。反応溶液を室温まで冷却し、クロロホルムを加えた。得られた有機層を水で２回洗浄し、硫酸マグネシウムで乾燥、溶媒を除去した。得られた固体をシリカゲルカラムクロマトグラフィー（展開溶媒：クロロホルム/ n-ヘキサン= 2：8）により精製した。さらに再結晶(トルエン/ヘキサン)により、化合物１を白色固体として得た(15.1 g, 70％)。
¹H NMR (400MHz, CDCl₃, δ): 8.20 (s, 1H), 7.98 (d, J = 7 Hz, 1H), 7.90 (s, 1H), 7.80-7.70 (m, 3H), 7.65 (d, J = 9 Hz, 1H), 7.61-7.57 (m, 2H), 7.49 (t, J = 7 Hz, 1H), 7.37 (t, J = 7 Hz, 1H).
MS (ASAP): 418.27 (M+H⁺). Calcd for C₃₀H₁₁D₈NO: 417.20. Example 1 (Production of compound 1)

Nitrogen atmosphere, 2-(3-bromophenyl)dibenzofuran (16.8 g, 51.9 mmol), carbazole-1,2,3,4,5,6,7,8-d8 (10 g, 57.1 mmol), Tris( dibenzylideneacetone)dipalladium(0) (4.75 g, 5.19 mmol), tri-tert-butylphosphonium tetrafluoroborate (3.01 g, 10.4 mmol) and sodium tert-butoxide (9.97 g, 103.7 mmol) in 330 ml of The mixture was added to toluene and refluxed for 24 hours. The reaction solution was cooled to room temperature and chloroform was added. The obtained organic layer was washed twice with water, dried over magnesium sulfate, and the solvent was removed. The obtained solid was purified by silica gel column chromatography (developing solvent: chloroform/n-hexane = 2:8). Further recrystallization (toluene/hexane) gave Compound 1 as a white solid (15.1 g, 70%).
¹ H NMR (400MHz, CDCl ₃ , δ): 8.20 (s, 1H), 7.98 (d, J = 7 Hz, 1H), 7.90 (s, 1H), 7.80-7.70 (m, 3H), 7.65 (d , J = 9 Hz, 1H), 7.61-7.57 (m, 2H), 7.49 (t, J = 7 Hz, 1H), 7.37 (t, J = 7 Hz, 1H).
MS (ASAP): 418.27 (M+H ⁺ ). Calcd for C ₃₀ H ₁₁ D ₈ NO: 417.20.

Example 2 (Production and comparison of organic light emitting device)
(Production of EL element 1)
Each thin film was laminated by vacuum evaporation at a degree of vacuum of 5.0×10 ⁻⁵ Pa on a glass substrate on which a 50 nm thick anode made of indium tin oxide (ITO) was formed. First, HAT-CN was formed to a thickness of 10 nm on ITO, and NPD was formed thereon to a thickness of 30 nm. Next, PTCz was formed to a thickness of 10 nm. Next, a delayed fluorescence compound having the structure shown below, Compound 1 produced in Example 1, was co-evaporated from a different deposition source to form a layer with a thickness of 40 nm to form a light-emitting layer. The contents of the delayed fluorescent compound and Compound 1 were 70% by mass for delayed fluorescent compound and 30% by mass for Compound 1. Next, after forming SF3-TRZ to a thickness of 10 nm, Liq and SF3-TRZ were co-evaporated from different deposition sources to form a layer of 30 nm thick. The contents of Liq and SF3-TRZ in this layer were 30% by mass and 70% by mass, respectively. Furthermore, a cathode was formed by forming Liq to a thickness of 2 nm, and then depositing aluminum (Al) to a thickness of 100 nm, thereby obtaining an organic electroluminescent element (EL element 1).

（比較ＥＬ素子２の作製）
化合物１のかわりに以下の比較化合物２を用い、それ以外は素子１を作製した工程と同じ工程を行うことにより、有機エレクトロルミネッセンス素子（比較ＥＬ素子２）を作製した。

(Production of comparative EL element 1)
An organic electroluminescent device (comparative EL device 1) was produced by using the following comparative compound 1 (described in Patent Document 3 above) instead of compound 1 and performing the same steps as those for producing device 1 except for that. did.

(Production of comparative EL element 2)
An organic electroluminescent device (comparative EL device 2) was produced by using Comparative Compound 2 below instead of Compound 1 and performing the same steps as those for producing Device 1 except for that.

(Element lifespan)
The driving voltage, luminous efficiency (EQE), and LT95 of each element produced by the above method were measured (2.0 mA/cm ² ). The results are summarized in Table 1 below in comparison with Comparative EL Element 1 using Comparative Compound 1.

Compared to Comparative EL Element 1 using Comparative Compound 1 in the light emitting layer, EL Element 1 using Compound 1 had approximately the same driving voltage and luminous efficiency, but LT95 increased by about 30%.
Furthermore, Comparative EL Device 2 using Comparative Compound 2 is significantly inferior to Comparative EL Device 1 in terms of driving voltage and LT95. It was even more noticeable.
Even when a delayed fluorescent compound other than those exemplified in Example 3 is used, the same effect on extending (improving) the device life of the organic light emitting element can be confirmed.

1: Substrate 2: Anode 3: Hole injection layer 4: Hole transport layer 5: Light emitting layer 6: Electron transport layer 7: Cathode

Claims (7)

An organic light-emitting device, the light-emitting layer containing a compound represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. ) An organic light-emitting device, in which the compound represented by formula (I) contained in the light-emitting layer is

The organic light emitting device according to claim 1. A host compound for an organic light emitting device represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. ) The compound represented by formula (I) is

The host compound for an organic light emitting device according to claim 3, which is A compound represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. ) The compound represented by formula (I) is

6. The compound according to claim 5. A method for extending the lifetime of an organic light emitting device using a compound represented by the following formula (I).

(Here, R represents a phenylene group,
The hydrogen atoms of the dibenzofuran skeleton may be substituted with one or more substituted or unsubstituted alkyl, cycloalkyl, aryl, or heteroaryl groups. )

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