JP4552417B2 - Light emitting device material and light emitting device using the same - Google Patents

Description

  The present invention is a light emitting element capable of converting electrical energy into light, and can be used in the fields of display elements, flat panel displays, backlights, lighting, interiors, signs, signboards, electrophotographic machines, optical signal generators, and the like. The present invention relates to a light emitting element.

  In recent years, research on organic thin-film light emitting devices that emit light when electrons injected from a cathode and holes injected from an anode are recombined in an organic phosphor sandwiched between both electrodes has been actively conducted. This light-emitting element is characterized by thin light emission with high luminance under a low driving voltage and multicolor light emission by selecting a light-emitting material.

This study was conducted by C.D. W. Since Tang et al. Have shown that organic thin film devices emit light with high brightness, many research institutions have studied. The representative structure of the organic thin film light emitting device presented by the Kodak research group is a hole transporting diamine compound on the ITO glass substrate, 8-hydroxyquinoline aluminum as the light emitting layer, and Mg: Ag as the cathode in sequence. It was provided, and green light emission of 1,000 cd / m ² was possible with a driving voltage of about 10 V (see Non-Patent Document 1).

  In addition, organic thin-film light-emitting elements can be obtained in various emission colors by using various fluorescent materials for the light-emitting layer, and therefore, researches for practical application to displays and the like are actively conducted. Among the three primary color luminescent materials, research on the green luminescent material is the most advanced, and at present, intensive research is being conducted to improve the characteristics of the red and blue luminescent materials.

One of the biggest challenges of organic thin film light emitting devices is to increase the durability of the devices. In particular, with respect to blue light-emitting elements, there are few blue light-emitting materials that provide elements with excellent durability and high reliability. For example, a technique using an anthracene compound for a blue light emitting element is disclosed. Blue light-emitting elements using anthracene monomers (see Patent Document 1) and anthracene dimers (see Patent Document 2) have been reported, but all have low luminous efficiency and insufficient durability. In addition, an example in which a compound in which an ethynyl group is introduced at the 9th and 10th positions of an anthracene skeleton is used for a light-emitting element has been reported, but the emission wavelength is increased and blue light emission is not obtained (see Patent Document 3). .
“Applied Physics Letters”, (USA), 1987, 51, 12, p. 913-915 Japanese Patent Laid-Open No. 11-3782 JP-A-8-12600 JP-A-11-87060

  As described above, a conventional organic thin film light emitting device has not been provided with a blue light emitting device having high luminous efficiency and excellent durability. Accordingly, an object of the present invention is to provide a blue light emitting device that solves the problems of the prior art and has high luminous efficiency and excellent durability.

  The present invention is a light emitting device material comprising an anthracene compound represented by the following general formula (1).

（ここでＲ¹〜Ｒ¹⁰はそれぞれ同じでも異なっていてもよく、水素、アルキル基、シクロアルキル基、アラルキル基、アルケニル基、シクロアルケニル基、アルキニル基、アルコキシ基、アルキルチオ基、アリールエーテル基、アリールチオエーテル基、アリール基、ヘテロアリール基、ハロゲン、シアノ基、アルデヒド基、カルボニル基、エステル基、カルバモイル基、アミノ基、シリル基の中から選ばれる。但し、Ｒ¹〜Ｒ¹⁰のうち少なくとも一つは、シアノ基、電子受容性窒素を含むヘテロアリール基および下記一般式（２）

(Wherein R ^{1 to} R ¹⁰ may be the same as or different from each other, hydrogen, alkyl group, cycloalkyl group, aralkyl group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, Arylthioether group, aryl group, heteroaryl group, halogen, cyano group, aldehyde group, carbonyl group, ester group, carbamoyl group, amino group, silyl group, provided that at least one of R ^{1 to} R ¹⁰ One is a cyano group, a heteroaryl group containing an electron-accepting nitrogen, and the following general formula (2):

（ここで、Ａｒ¹はアリール基もしくはヘテロアリール基であり、αはアントラセン骨格との連結部分を表す。）で表されるエチニル基の中から選ばれる少なくとも一つで置換されているが、Ｒ⁹とＲ¹⁰が同時に一般式（２）で表されるエチニル基になることはない。）
さらに本発明は、陽極と陰極の間に少なくとも発光層と電子輸送層が存在し、電気エネルギーにより発光する発光素子であって、該発光素子が一般式（１）で表されるアントラセン化合物を含有することを特徴とする発光素子である。

(Wherein Ar ¹ represents an aryl group or a heteroaryl group, and α represents a connecting portion with an anthracene skeleton), and is substituted with at least one selected from ethynyl groups represented by ⁹ and R ¹⁰ do not simultaneously become an ethynyl group represented by the general formula (2). )
Furthermore, the present invention is a light-emitting element that has at least a light-emitting layer and an electron transport layer between an anode and a cathode and emits light by electric energy, and the light-emitting element contains an anthracene compound represented by the general formula (1) The light emitting element is characterized in that.

  According to the present invention, a light emitting device having high luminous efficiency and excellent durability can be obtained by using an anthracene compound having a specific substituent as a light emitting device material. Therefore, the light-emitting element of the present invention can be applied to fields such as display elements, flat panel displays, backlights, lighting, interiors, signs, signboards, electrophotographic machines, and optical signal generators, and has great technical value. Is.

  First, the anthracene compound represented by the general formula (1) used in the present invention will be described in detail.

（ここでＲ^１〜Ｒ^８はそれぞれ同じでも異なっていてもよく、水素、アルキル基、アリール基、ヘテロアリール基、シアノ基、シリル基および下記一般式（２）で表されるエチニル基の中から選ばれる。Ｒ^９およびＲ^１０はそれぞれ同じでも異なっていてもよく、フェニル基、アルキル置換フェニル基、アルコキシ置換フェニル基、ヘテロアリール基および下記一般式（２）で表されるエチニル基の中から選ばれる。ただし、Ｒ^１〜Ｒ^１０の少なくとも１つは下記一般式（２）で表されるエチニル基である。また、Ｒ^９とＲ^１０が同時に一般式（２）で表されるエチニル基になることはない。）

(May be the same or different, respectively wherein R ¹ to R ⁸ represents hydrogen, an alkyl group, the aryl group, a heteroaryl group, shea Anomoto, ethynyl represented by silyl groups and represented by the following general formula (2) R ⁹ and R ¹⁰ may be the same or different from each other, and may be a phenyl group, an alkyl-substituted phenyl group, an alkoxy-substituted phenyl group, a heteroaryl group, or ethynyl represented by the following general formula (2) However, at least one of R ^{1 to} R ¹⁰ is an ethynyl group represented by the following general formula (2), and R ⁹ and R ¹⁰ are represented by the general formula (2) at the same time. Never become an ethynyl group.)

（ここで、Ａｒ^１はアリール基もしくはヘテロアリール基であり、αはアントラセン骨格との連結部分を表す。）

(Here, Ar ¹ is an aryl group or a heteroaryl group, and α represents a connecting portion with an anthracene skeleton .)

  Among these substituents, the alkyl group represents, for example, a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, a propyl group, or a butyl group, which may be unsubstituted or substituted. The substituent in the case of being substituted is not particularly limited, and examples thereof include an alkyl group, an aryl group, a heteroaryl group, and the like, and this point is common to the following description. Further, the number of carbon atoms of the alkyl group is not particularly limited, but is usually in the range of 1 to 20 from the viewpoint of availability and cost.

  The cycloalkyl group represents a saturated alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl, norbornyl, adamantyl, and the like, which may be unsubstituted or substituted. Although carbon number of an alkyl group part is not specifically limited, Usually, it is the range of 3-20.

  The aralkyl group refers to an aromatic hydrocarbon group via an aliphatic hydrocarbon such as a benzyl group or a phenylethyl group, and both the aliphatic hydrocarbon and the aromatic hydrocarbon are unsubstituted or substituted. It doesn't matter. Although carbon number of an aliphatic part is not specifically limited, Usually, it is the range of 1-20.

  Moreover, an alkenyl group shows the unsaturated aliphatic hydrocarbon group containing double bonds, such as a vinyl group, an allyl group, and a butadienyl group, for example, and this may be unsubstituted or substituted. Although carbon number of an alkenyl group is not specifically limited, Usually, it is the range of 2-20.

  The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond such as a cyclopentenyl group, a cyclopentadienyl group, or a cyclohexenyl group, which is unsubstituted or substituted. It doesn't matter.

  The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond such as an ethynyl group, which may be unsubstituted or substituted. Although carbon number of an alkynyl group is not specifically limited, Usually, it is the range of 2-20.

  The alkoxy group refers to, for example, an aliphatic hydrocarbon group via an ether bond such as a methoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. Although carbon number of an alkoxy group is not specifically limited, Usually, it is the range of 1-20.

  The alkylthio group is a group in which an oxygen atom of an ether bond of an alkoxy group is substituted with a sulfur atom.

  The aryl ether group refers to, for example, an aromatic hydrocarbon group via an ether bond such as a phenoxy group, and the aromatic hydrocarbon group may be unsubstituted or substituted. Although carbon number of an aryl ether group is not specifically limited, Usually, it is the range of 6-40.

  The arylthioether group is a group in which the oxygen atom of the ether bond of the arylether group is substituted with a sulfur atom.

  Moreover, an aryl group shows aromatic hydrocarbon groups, such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, a terphenyl group, a pyrenyl group, for example. The aryl group may be unsubstituted or substituted. Although carbon number of an aryl group is not specifically limited, Usually, it is the range of 6-40.

  The heteroaryl group refers to, for example, a cyclic structure group having an atom other than carbon, such as a furanyl group, a thiophenyl group, an oxazolyl group, a pyridyl group, a quinolinyl group, or a carbazolyl group, which is unsubstituted or substituted It doesn't matter. Although carbon number of a heteroaryl group is not specifically limited, Usually, it is the range of 2-30.

  Halogen is fluorine, chlorine, bromine or iodine.

  The aldehyde group, carbonyl group, ester group, carbamoyl group, and amino group may include those substituted with aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, heteroaryl rings, and the like.

  Further, the aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon and heteroaryl ring may be unsubstituted or substituted.

  The silyl group indicates, for example, a silicon compound group such as a trimethylsilyl group, which may be unsubstituted or substituted. Although carbon number of a silyl group is not specifically limited, Usually, it is the range of 3-20. Moreover, the number of silicon is 1-6 normally.

  The electron-accepting nitrogen in the present invention represents a nitrogen atom that forms a multiple bond with an adjacent atom. Since the nitrogen atom has a high electronegativity, the multiple bond has an electron accepting property. Therefore, heteroaryl groups containing electron-accepting nitrogen have a high electron affinity. Examples of the heteroaryl ring having an electron-accepting nitrogen include, for example, a pyridine ring, pyrazine ring, pyrimidine ring, quinoline ring, quinoxaline ring, naphthyridine ring, pyrimidopyrimidine ring, benzoquinoline ring, phenanthroline ring, imidazole ring, oxazole ring, Examples thereof include an oxadiazole ring, a triazole ring, a thiazole ring, a thiadiazole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring and a phenanthrimidazole ring.

Further, R ⁹ and R ¹⁰ in the general formula (1) do not simultaneously become an ethynyl group represented by the general formula (2). When both R ⁹ and R ¹⁰ are ethynyl groups represented by the general formula (2), the emission wavelength becomes longer and blue light emission cannot be obtained.

In the anthracene compound represented by the general formula (1) of the present invention, at least one of R ^{1 to} R ¹⁰ is a heteroaryl group containing a cyano group, an electron-accepting nitrogen, and an ethynyl represented by the general formula (2). By being substituted with at least one selected from the group, a light-emitting element having high efficiency and excellent durability is provided. Further, it is preferable that either one of R ^{9 and} R ¹⁰ is an ethynyl group represented by the general formula (2) because higher luminous efficiency can be obtained. Furthermore, Ar ¹ in the general formula (2) is preferably an aryl group substituted with a cyano group or a heteroaryl group containing an electron-accepting nitrogen because durability is further improved.

  Specific examples of the anthracene compound as described above include the following.

一般式（１）で表されるアントラセン化合物の合成には、公知の方法を使用することができる。アントラセン骨格へシアノ基を導入する方法としては、例えば、アミノ置換アントラセンをジアゾ塩にした後、シアン化物と反応させる方法、アントラセンカルボン酸アミドの脱水反応を用いる方法、メチル置換アントラセンを酸化しアルデヒドとした後、ヒドロキシルアミンと脱水縮合反応させる方法などが挙げられるが、これらに限定されるものではない。電子受容性窒素を含むヘテロアリール基をアントラセン骨格に導入する方法としては、例えば、ハロゲン化アントラセンと電子受容性窒素を含むヘテロアリール金属試薬によるパラジウムやニッケル触媒下でのカップリング反応を用いる方法、アセチル基置換アントラセンと芳香族アミノアルデヒドとの脱水縮合反応を用いる方法などが挙げられるが、これらに限定されるものではない。アントラセン骨格へのエチニル基の導入方法としては、例えば、ハロゲン化アントラセンとエチニル基を有する化合物による銅触媒下でのカップリング反応を用いる方法が挙げられるが、これに限定されるものではない。

A known method can be used for the synthesis of the anthracene compound represented by the general formula (1). Examples of the method for introducing a cyano group into the anthracene skeleton include a method in which an amino-substituted anthracene is converted to a diazo salt and then reacted with a cyanide, a method using a dehydration reaction of an anthracene carboxylic acid amide, a methyl-substituted anthracene is oxidized and an aldehyde is obtained. Thereafter, a method of dehydration condensation reaction with hydroxylamine can be mentioned, but it is not limited thereto. As a method for introducing a heteroaryl group containing an electron-accepting nitrogen into an anthracene skeleton, for example, a method using a coupling reaction under a palladium or nickel catalyst with a heteroaryl metal reagent containing a halogenated anthracene and an electron-accepting nitrogen, Examples thereof include, but are not limited to, a method using a dehydration condensation reaction between an acetyl group-substituted anthracene and an aromatic aminoaldehyde. Examples of a method for introducing an ethynyl group into an anthracene skeleton include a method using a coupling reaction under a copper catalyst with a compound having a halogenated anthracene and an ethynyl group, but are not limited thereto.

  In the present invention, the anthracene compound represented by the general formula (1) is suitably used as a light emitting device material.

  Next, embodiments of the light-emitting element of the present invention will be described in detail with examples. The light emitting device of the present invention comprises at least an anode and a cathode, and an organic layer made of a light emitting device material interposed between the anode and the cathode.

  In order to extract light, the anode used in the present invention may be transparent, and conductive metal oxides such as tin oxide, indium oxide and indium tin oxide (ITO), or metals such as gold, silver and chromium, Inorganic conductive materials such as copper iodide and copper sulfide, and conductive polymers such as polythiophene, polypyrrole and polyaniline are not particularly limited, but it is particularly desirable to use ITO glass or Nesa glass.

  The resistance of the transparent electrode is sufficient if a current sufficient for light emission of the light emitting element can be supplied, and it is desirable that the resistance is low from the viewpoint of power consumption of the light emitting element. For example, an ITO substrate of 300Ω / □ or less will function as a device electrode, but since it is now possible to supply a substrate of about 10Ω / □, use a low-resistance product of 100Ω / □ or less. Is particularly desirable. The thickness of ITO can be arbitrarily selected according to the resistance value, but is usually used in a range of 100 to 300 nm.

In order to maintain the mechanical strength of the light emitting element, the light emitting element is preferably formed over a substrate. As the substrate, a glass substrate such as soda glass or non-alkali glass is preferably used. As the thickness of the glass substrate, it is sufficient that the thickness is sufficient to maintain the mechanical strength. The glass material is preferably alkali-free glass because it is better to have less ions eluted from the glass, but soda-lime glass with a barrier coat such as SiO ₂ is also available on the market. it can. Furthermore, if the anode functions stably, the substrate does not have to be glass. For example, the anode may be formed on a plastic substrate. The ITO film forming method is not particularly limited, such as an electron beam method, a sputtering method, and a chemical reaction method.

  The material used for the cathode used in the present invention is not particularly limited as long as it can efficiently inject electrons into the organic layer, but generally platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, Examples thereof include chromium, lithium, sodium, potassium, calcium and magnesium, and alloys thereof. Lithium, sodium, potassium, calcium, magnesium, or alloys containing these low work function metals are effective for increasing the electron injection efficiency and improving device characteristics. However, these low work function metals are generally unstable in the atmosphere. For example, the organic layer is doped with a small amount of lithium or magnesium (1 nm or less in the vacuum vapor deposition thickness meter display) to be stable. A method using a high electrode can be cited as a preferred example. Also, an inorganic salt such as lithium fluoride can be used. Furthermore, for electrode protection, metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium, or alloys using these metals, and inorganic substances such as silica, titania and silicon nitride, polyvinyl alcohol, vinyl chloride Lamination of hydrocarbon polymer compounds and the like is a preferred example. The method for producing these electrodes is not particularly limited as long as conduction can be achieved, such as resistance heating, electron beam, sputtering, ion plating, and coating.

  The light emitting device of the present invention is composed of a light emitting device material in which the organic layer contains an anthracene compound represented by the general formula (1). The light emitting device material corresponds to both a material that emits light by itself and a material that assists the light emission, and refers to a compound that participates in light emission. Specifically, a hole transport material, a light emitting material, and an electron This includes transportation materials.

  The organic layer constituting the light emitting device of the present invention is formed of at least a light emitting layer and an electron transport layer made of a light emitting device material. Examples of the structure of the organic layer include 1) a hole transport layer / light-emitting layer / electron transport layer and 2) a light-emitting layer / electron transport layer. Moreover, each said layer may consist of a single layer, respectively, and may consist of multiple layers.

  The hole transport layer is formed by laminating and mixing one or more hole transport materials or a mixture of the hole transport material and the polymer binder. Examples of the hole transport material include N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine, N, N′-dinaphthyl- Triphenylamine derivatives such as N, N′-diphenyl-4,4′-diphenyl-1,1′-diamine, 4,4 ′, 4 ″ -tris (3-methylphenyl (phenyl) amino) triphenylamine, Biscarbazole derivatives such as bis (N-allylcarbazole) or bis (N-alkylcarbazole), pyrazoline derivatives, stilbene compounds, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, porphyrin derivatives, etc. For heterocyclic compounds and polymers, polycarbonates and Derivatives, polyvinylcarbazole, polysilane, and the like are preferable, but the compound is not particularly limited as long as it is a compound that forms a thin film necessary for manufacturing a light-emitting element, can inject holes from the anode, and can further transport holes. .

  In the present invention, the light emitting layer may be either a single layer or a plurality of layers, each formed of a light emitting material (host material, dopant material), which may be a mixture of a host material and a dopant material, Either the material alone or the material may be used. That is, in the light emitting element of the present invention, only the host material or the dopant material may emit light in each light emitting layer, or both the host material and the dopant material may emit light. Each of the host material and the dopant material may be one kind or a plurality of combinations. The dopant material may be included in the host material as a whole, or may be included partially. The dopant material may be either laminated or dispersed. If the amount of the dopant material is too large, a concentration quenching phenomenon occurs, so that it is preferably used at 20% by weight or less, more preferably 10% by weight or less with respect to the host material. As a doping method, it can be formed by a co-evaporation method with a host material, but it may be pre-mixed with the host material and then simultaneously deposited.

  The anthracene compound represented by the general formula (1) of the present invention is suitably used as a light emitting material. Moreover, since the anthracene compound of the present invention exhibits strong light emission in the blue region, it is suitably used as a light emitting material for blue. The blue light emission in the present invention refers to light emission having a peak wavelength of an emission spectrum in a region of 420 nm to 490 nm. Although the anthracene compound of the present invention may be used as a host material, it has a high fluorescence quantum yield, a small half-value width of the emission spectrum, and a small peak wavelength difference (Stokes shift) between the emission spectrum and the excitation spectrum. It is preferably used as a dopant material.

  The dopant material contained in the light emitting material need not be limited to only one kind of the anthracene compound, and a plurality of anthracene compounds may be used in combination, or one or more kinds of known dopant materials may be used in combination with the anthracene compound. Good. Specifically, conventionally known aromatic hydrocarbon compounds such as naphthalene, anthracene, phenanthrene, pyrene, triphenylene, perylene, fluorene, indene and derivatives thereof, furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9'-spirobisilafluorene, benzothiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline, pyrazine, naphthyridine, quinoxaline, pyrrolopyridine, thioxanthene and other heteroaryl ring compounds and derivatives thereof, distyryl Benzene derivative, tetraphenylbutadiene derivative, stilbene derivative, aldazine derivative, coumarin derivative, imidazole, thiazole, thiadiazole, carbazole, oxazole Representative examples include azole derivatives such as oxadiazole and triazole and metal complexes thereof, and N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine. Aromatic amine derivatives and the like, but are not limited thereto.

  The host material used in the present invention is not particularly limited, but metal chelates such as fused ring derivatives such as anthracene and pyrene, tris (8-quinolinolato) aluminum, which have been known as light emitters. Oxinoid compounds, bisstyryl derivatives such as distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, oxadiazole derivatives, polyphenylene in polymer systems Vinylene derivatives, polyparaphenylene derivatives, and polythiophene derivatives are preferably used. Among these, a compound represented by the following general formula (3) is preferably used because it has excellent durability.

ここでＲ¹¹〜Ｒ¹⁸はそれぞれ同じでも異なっていてもよく、水素、アルキル基、シクロアルキル基、アラルキル基、アルケニル基、シクロアルケニル基、アルキニル基、アルコキシ基、アルキルチオ基、アリールエーテル基、アリールチオエーテル基、アリール基、ヘテロアリール基、ハロゲン、シアノ基、アルデヒド基、カルボニル基、エステル基、カルバモイル基、アミノ基、シリル基、ホスフィノ基、ホスフィンオキサイド基の中から選ばれる。Ａｒ²およびＡｒ³はアリール基もしくはヘテロアリール基を表す。

R ^{11 to} R ¹⁸ may be the same or different from each other, and may be hydrogen, alkyl group, cycloalkyl group, aralkyl group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl. It is selected from among thioether groups, aryl groups, heteroaryl groups, halogens, cyano groups, aldehyde groups, carbonyl groups, ester groups, carbamoyl groups, amino groups, silyl groups, phosphino groups, and phosphine oxide groups. Ar ² and Ar ³ represent an aryl group or a heteroaryl group.

  Among these substituents, the phosphino group and phosphine oxide group may include those substituted with aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, heteroaryl rings, and the like. About another substituent, it is the same as that of description of the said General formula (1).

  Specific examples of the compound represented by the general formula (3) include the following.

本発明において、電子輸送層とは、陰極から電子が注入され、さらに電子を輸送することを司る層であり、電子注入効率が高く、注入された電子を効率良く輸送することが望ましい。そのためには電子親和力が大きく、しかも電子移動度が大きく、さらに安定性に優れ、トラップとなる不純物が製造時および使用時に発生しにくい物質であることが要求される。しかしながら、正孔と電子の輸送バランスを考えた場合に、陽極からの正孔が再結合せずに陰極側へ流れるのを効率よく阻止できる役割を主に果たす場合には、電子輸送能力がそれ程高くなくても、発光効率を向上させる効果は電子輸送能力が高い材料と同等に有する。したがって、本発明における電子輸送層は、正孔の移動を効率よく阻止できる正孔阻止層も同義のものとして含まれる。

In the present invention, the electron transport layer is a layer that administers electrons injected from the cathode and further transports electrons. It is desirable that the electron transport efficiency is high and the injected electrons are transported efficiently. For this purpose, it is required that the material has a high electron affinity, a high electron mobility, excellent stability, and a substance that does not easily generate trapping impurities during manufacturing and use. However, considering the transport balance between holes and electrons, if the role of effectively preventing the holes from the anode from flowing to the cathode side without recombination is mainly played, the electron transport capability is much higher. Even if it is not high, the effect of improving the luminous efficiency is equivalent to that of a material having a high electron transport capability. Therefore, the electron transport layer in the present invention includes a hole blocking layer that can efficiently block the movement of holes as the same meaning.

  The electron transport material used for the electron transport layer is not particularly limited, but is a condensed ring aromatic ring derivative such as naphthalene or anthracene, and styryl represented by 4,4′-bis (diphenylethenyl) biphenyl. Aromatic ring derivatives, perylene derivatives, perinone derivatives, coumarin derivatives, naphthalimide derivatives, quinone derivatives such as anthraquinone and diphenoquinone, phosphorus oxide derivatives, carbazole derivatives and indole derivatives, quinolinol complexes such as tris (8-quinolinolato) aluminum and hydroxyphenyl Examples thereof include hydroxyazole complexes such as oxazole complexes, azomethine complexes, tropolone metal complexes and flavonol metal complexes, and compounds composed of heteroaryl rings having electron-accepting nitrogen. Among them, from the viewpoint of lowering driving voltage and improving durability, a compound comprising a heteroaryl ring having an electron-accepting nitrogen, and the compound comprising the heteroaryl ring is formed only by a covalent bond, Preferably used. A compound comprising a heteroaryl ring having an electron-accepting nitrogen is used. Examples of the compound comprising a heteroaryl ring include benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, and triazole derivatives. Preferred examples include pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives, and naphthyridine derivatives. Among them, imidazole derivatives such as tris (N-phenylbenzimidazol-2-yl) benzene, oxadiazole derivatives such as 1,3-bis [(4-tert-butylphenyl) 1,3,4-oxadiazolyl] phenylene, Triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole, phenanthroline derivatives such as bathocuproine and 1,3-bis (2-phenyl-1,10-phenanthroline-9-yl) benzene, Benzoquinoline derivatives such as 2,2′-bis (benzo [h] quinolin-2-yl) -9,9′-spirobifluorene, 1,3-bis (4 ′-(2,2 ′: 6′2 ”-Terpyridinyl)) terpyridine derivatives such as benzene, bis (1-naphthyl) -4- (1,8-naphthyridine-2- Le) naphthyridine derivatives such as phenyl phosphine oxide are preferably used from the viewpoint of electron transporting capability.

  These electron transport materials are used alone, but may be used in combination with different electron transport materials. The ionization potential of the electron transport layer is not particularly limited, but is preferably 5.8 eV or more and 8.0 eV or less, and more preferably 6.0 eV or more and 7.5 eV or less.

  The method for forming each layer constituting the light-emitting element is not particularly limited, such as resistance heating vapor deposition, electron beam vapor deposition, sputtering, molecular lamination method, coating method, etc., but resistance heating vapor deposition or electron beam vapor deposition is usually a characteristic. In terms of surface.

  The thickness of the layer cannot be limited because it depends on the resistance value of the luminescent material, but is selected from 1 to 1,000 nm. The film thickness of the light emitting layer, the electron transport layer, and the hole transport layer is preferably 1 nm to 200 nm, and more preferably 5 nm to 100 nm.

  The light-emitting element of the present invention is a light-emitting element that can convert electrical energy into light. Here, the electric energy mainly indicates a direct current, but a pulse current or an alternating current can also be used. The current value and voltage value are not particularly limited, but in consideration of the power consumption and life of the element, the maximum luminance should be obtained with as low energy as possible.

  The light emitting device of the present invention is suitably used as a display for displaying in a matrix and / or segment system, for example.

  The matrix in the present invention is a matrix in which pixels for display are two-dimensionally arranged such as a lattice shape or a mosaic shape, and displays a character or an image by a set of pixels. The shape and size of the pixel are determined by the application. For example, a square pixel with a side of 300 μm or less is usually used for displaying images and characters on a personal computer, monitor, TV, and a pixel with a side of mm order for a large display such as a display panel. become. In monochrome display, pixels of the same color may be arranged, but in color display, red, green, and blue pixels are displayed side by side. In this case, there are typically a delta type and a stripe type. The matrix driving method may be either a line sequential driving method or an active matrix. The line-sequential driving has an advantage that the structure is simple. However, the active matrix may be superior in consideration of operation characteristics, so that it is necessary to use them depending on the application.

  In the segment system (type) in the present invention, a pattern is formed so as to display predetermined information, and a predetermined region is caused to emit light. For example, the time and temperature display in a digital clock or a thermometer, the operation state display of an audio device or an electromagnetic cooker, the panel display of an automobile, and the like can be mentioned. The matrix display and the segment display may coexist in the same panel.

  The light emitting device of the present invention is also preferably used as a backlight for various devices. The backlight is used mainly for the purpose of improving the visibility of a display device that does not emit light, and is used for a liquid crystal display device, a clock, an audio device, an automobile panel, a display panel, a sign, and the like. In particular, as a backlight for liquid crystal display devices, especially personal computers for which thinning is an issue, considering that conventional methods are made of fluorescent lamps and light guide plates, it is difficult to reduce the thickness. The backlight using the light emitting element in the invention is thin and lightweight.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited by these Examples. In addition, the number of the compound in each following Example points out the number in the compound group mentioned above. The evaluation method for structural analysis is shown below.

¹ H-NMR was measured with a deuterated chloroform solution using superconducting FTNMR EX-270 (manufactured by JEOL Ltd.).

( Reference Example 1)
Synthesis method of compound [1] A mixed solution of 5 g of 9,10-diphenylanthracene-2-carboxaldehyde, 2 g of hydroxylamine hydrochloride, 2.3 g of sodium acetate and 50 ml of acetic acid was heated and stirred at 130 ° C. for 12 hours under a nitrogen stream. . After cooling to room temperature, 100 ml of water was poured and the precipitate was filtered. The solid was washed with methanol and purified by silica gel column chromatography. After vacuum drying, 1.5 g of pale yellow crystals were obtained. The results of ¹ H-NMR analysis of the obtained powder were as follows.
¹ H-NMR (CDCl ₃ (d = ppm)): 7.35-7.47 (m, 7H), 7.55-7.68 (m, 6H), 7.71-7.78 (m, 3H), 8.14 (d, 1H)
Next, a light emitting device using the compound [1] was produced as follows. A glass substrate on which an ITO transparent conductive film was deposited to a thickness of 150 nm (Asahi Glass Co., Ltd., 15Ω / □, electron beam evaporated product) was cut into 30 × 40 mm and etched. The obtained substrate was ultrasonically washed with acetone and “Semicocrine (registered trademark) 56” (manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, respectively, and then washed with ultrapure water. Subsequently, it was ultrasonically cleaned with isopropyl alcohol for 15 minutes and then immersed in hot methanol for 15 minutes and dried. This substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the device, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁵ Pa or less. By the resistance heating method, first, copper phthalocyanine was deposited as a hole injecting material at 10 nm, and 4,4′-bis (N- (1-naphthyl) -N-phenylamino) biphenyl was deposited as a hole transporting material at 50 nm. Next, 4,4′-bis (2,2-diphenylethenyl) biphenyl is used as a light emitting material, a host material, and a compound [1] as a dopant material is 35 nm thick so that the doping concentration is 1%. Vapor deposited. Next, 1,3-bis (1,10-phenanthrolin-2-yl) benzene was laminated to a thickness of 15 nm as an electron transport material. Next, after doping lithium with a 0.5 nm organic layer, 1,000 nm of aluminum was vapor-deposited to form a cathode, and a 5 × 5 mm square device was fabricated. The film thickness referred to here is a crystal oscillation type film thickness monitor display value. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 2.1 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 1,500 hours.

( Reference Example 2)
Synthesis Method of Compound [14] A mixed solution of 5 g of 9,10-diphenylanthracene-2-carboxaldehyde, 1.8 g of 2-aminobenzenethiol and 100 ml of dimethyl sulfoxide was heated and stirred at 140 ° C. for 6 hours. After cooling to room temperature, 100 ml of water was poured and the precipitate was filtered. The solid was washed with water and methanol and purified by silica gel column chromatography. After vacuum drying, 4 g of yellow crystals were obtained. The results of ¹ H-NMR analysis of the obtained powder were as follows.
¹ H-NMR (CDCl ₃ (d = ppm)): 7.35 to 7.74 (m, 16H), 7.83 (t, 2H), 8.04 (dd, 1H), 8.11 (dd, 1H), 8.36 (d, 1H)
Next, a light emitting device using the compound [14] was produced as follows. A light emitting device was produced in the same manner as in Reference Example 1 except that Compound [14] was used as the dopant material so that the doping concentration was 1%. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 2.3 lm / W was obtained. This light emitting device was driven by direct current at 1 mA, and the luminance half time was 1,200 hours.

( Reference Example 3)
Method of synthesizing compound [4] 9-bromo-10-cyanoanthracene 8 g, 4-biphenylboronic acid 8.4 g, tetrakis (triphenylphosphine) palladium (0) 3.3 g, tripotassium phosphate 18 g and toluene 500 ml, water 300 ml of the mixed solution was heated and stirred at 120 ° C. for 24 hours under a nitrogen stream. After cooling to room temperature, the precipitate was filtered and washed with water and methanol. After purification by silica gel column chromatography and vacuum drying, 7.3 g of yellow crystals were obtained. The results of ¹ H-NMR analysis of the obtained powder were as follows.
¹ H-NMR (CDCl ₃ (d = ppm)): 7.43-7.56 (m, 7H), 7.68-7.86 (m, 8H), 8.52 (d, 2H)
Next, a light emitting device using the compound [4] was produced as follows. A light emitting device was produced in the same manner as in Reference Example 1 except that the compound [4] was used as the dopant material so that the doping concentration was 1%. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 1.8 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 1,600 hours.

( Reference Example 4)
Synthesis method of compound [11] 9-bromo-10-cyanoanthracene 8 g, 1,4-phenylenediboronic acid 2.3 g, palladium acetate 0.32 g, tripotassium phosphate 24 g, tetrabutylammonium bromide 4.6 g and dimethyl A mixed solution of 280 ml of formamide was heated and stirred at 150 ° C. for 8 hours under a nitrogen stream. After cooling to room temperature, 1 L of water was added and extracted with 1 L of dichloromethane. The dichloromethane layer was washed with a 1N aqueous hydrochloric acid solution, a saturated aqueous sodium chloride solution and water, concentrated with an evaporator, and purified by silica gel column chromatography. After vacuum drying, 0.6 g of yellow crystals was obtained. The results of ¹ H-NMR analysis of the obtained powder were as follows.
¹ H-NMR (CDCl ₃ (d = ppm)): 7.53-7.88 (m, 12H), 7.95 (d, 4H), 8.58 (d, 4H)
Next, a light emitting device using the compound [11] was produced as follows. A light emitting device was produced in the same manner as in Reference Example 1 except that the compound [11] was used as a dopant material so that the doping concentration was 1%. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 1.7 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 1,800 hours.

(Example 1 )
Synthesis method of compound [23] 9-bromo-10-phenylanthracene 5 g, phenylacetylene 1.8 g, copper (I) iodide 0.29 g, tetrakis (triphenylphosphine) palladium (0) 1.7 g, triethylamine 120 ml A mixed solution of 1.2 L of toluene was heated and stirred at 60 ° C. for 24 hours under a nitrogen stream. After cooling to room temperature, 1 L of saturated aqueous sodium chloride solution was added, and the mixture was extracted with 1 L of dichloromethane. After washing with water, the solution was concentrated with an evaporator and purified by silica gel column chromatography. After vacuum drying, 1.5 g of yellow crystals were obtained. The results of ¹ H-NMR analysis of the obtained powder were as follows.
¹ H-NMR (CDCl ₃ (d = ppm)): 7.37-7.62 (m, 12H), 7.68 (d, 2H), 7.80 (d, 2H), 8.74 (d, 2H)
Next, a light emitting device using the compound [23] was produced as follows. A light emitting device was produced in the same manner as in Reference Example 1 except that Compound [23] was used as the dopant material so that the doping concentration was 1%. From this light-emitting element, high-efficiency blue light emission with a luminous efficiency of 2.6 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 1,900 hours.

(Comparative Example 1)
A light emitting device was produced in the same manner as in Reference Example 1 except that 9,10-bis (4-methoxyphenyl) anthracene was used as the dopant material so that the doping concentration was 1%. From this light emitting element, blue light emission with a luminous efficiency of 0.8 lm / W was obtained. When this light emitting device was DC driven at 1 mA, the luminance was reduced by half in 500 hours.

(Comparative Example 2)
A light emitting device was fabricated in the same manner as in Reference Example 1 except that 9,10-bis (phenylethynyl) anthracene was used as a dopant material so that the doping concentration was 1%. This light emitting element emitted green light and could not be used as a blue light emitting element.

(Comparative Example 3)
A light emitting device was produced in the same manner as in Reference Example 1 except that 4,4′-bis (2- (4-diphenylaminophenyl) ethenyl) biphenyl was used as a dopant material so that the doping concentration was 2%. From this light emitting element, blue-green light emission with a luminous efficiency of 2.5 lm / W was obtained. When this light emitting device was DC driven at 1 mA, the luminance was reduced by half in 200 hours.

(Example 2 )
After vapor deposition up to the hole injection material in the same manner as in Reference Example 1, the light emitting material is 9,10-bis (2-naphthyl) anthracene as the host material, and the compound [23] is used as the dopant material with a doping concentration of 1%. Vapor deposition was performed to a thickness of 25 nm. Next, 1,3-bis (1,10-phenanthrolin-2-yl) benzene was laminated to a thickness of 25 nm as an electron transport material. Next, after doping the organic layer with 0.5 nm of lithium, 1000 nm of aluminum was vapor-deposited to form a cathode, and a 5 × 5 mm square device was fabricated. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 1.9 lm / W was obtained. This light emitting device was DC-driven at 1 mA, and the luminance half time was 2,500 hours.

(Comparative Example 4)
A light emitting device was produced in the same manner as in Example 2 except that the dopant material was not used. From this light emitting element, blue light emission with a luminous efficiency of 0.4 lm / W was obtained, but when driven by direct current at 1 mA, the luminance was reduced by half in 300 hours.

(Example 3 )
A light emitting device was fabricated in the same manner as in Example 2 except that 9,10-bis (9-phenanthryl) anthracene was used as the host material. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 2.8 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 2,200 hours.

(Example 4 )
A light-emitting element was fabricated in the same manner as in Example 2 , except that 9,10-diphenyl-2- (1-naphthyl) anthracene was used as the host material. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 2.4 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 2,100 hours.

(Example 5 )
A light emitting device was produced in the same manner as in Example 2 except that (9,10-diphenylanthracen-2-yl) diphenylphosphine oxide was used as the host material. From this light emitting element, high efficiency blue light emission with a luminous efficiency of 2.2 lm / W was obtained. This light emitting device was dc-driven at 1 mA, and the luminance half time was 2,400 hours.

( Reference Example 5 )
A light emitting device was produced in the same manner as in Reference Example 2, except that 1,3-bis (9-phenyl-1,10-phenanthrolin-2-yl) benzene was used as the electron transport material. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 2.5 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 1,500 hours.

( Reference Example 6 )
A light emitting device was produced in the same manner as in Reference Example 2, except that 1,3-bis (4 ′-(2,2 ′: 6′2 ″ -terpyridinyl)) benzene was used as the electron transporting material. From the above, high-efficiency blue light emission with a light emission efficiency of 2.2 lm / W was obtained, and this light-emitting element was dc-driven at 1 mA, and its luminance half-life was 1,200 hours.

( Reference Example 7 )
A light emitting device was produced in the same manner as in Reference Example 2, except that bis (1-naphthyl) -4- (quinoxalin-2-yl) phenylphosphine oxide was used as the electron transport material. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 2.1 lm / W was obtained. This light emitting device was DC-driven at 1 mA, and the luminance half time was 1,000 hours.

( Reference Example 8 )
A light-emitting device was fabricated in the same manner as in Reference Example 2, except that bis (1-naphthyl) -4- (1,8-naphthyridin-2-yl) phenylphosphine oxide was used as the electron transport material. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 2.3 lm / W was obtained. This light emitting device was DC driven at 1 mA, and the luminance half time was 1,100 hours.

( Reference Example 9 )
A light emitting device was fabricated in the same manner as in Reference Example 2, except that phenylbis (1-pyrenyl) phosphine oxide was used as the electron transport material. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 1.7 lm / W was obtained. This light emitting device was DC-driven at 1 mA, and the luminance half time was 1,300 hours.

( Reference Example 10 )
A light emitting device was produced in the same manner as in Reference Example 2 except that tris (8-quinolinolato) aluminum (III) was used as the electron transport material. From this light-emitting element, high-efficiency blue light emission with a light emission efficiency of 1.5 lm / W was obtained. This light emitting device was DC-driven at 1 mA, and the luminance half time was 1,000 hours.

(Example 6 )
A light emitting device was produced in the same manner as in Reference Example 1 except that Compound [23] was used as the host material and no dopant material was used. From this light-emitting element, high-efficiency blue light emission with a luminous efficiency of 1.6 lm / W was obtained.

( Reference Example 11 )
A glass substrate (manufactured by Asahi Glass Co., Ltd., 15Ω / □, electron beam evaporation product) on which ITO transparent conductive film is deposited to 150 nm is cut into 30 × 40 mm, and 300 μm pitch (remaining width 270 μm) × 32 stripes by photolithography. Patterned into a shape. One side of the ITO stripe in the long side direction is expanded to a pitch of 1.27 mm (opening width 800 μm) in order to facilitate electrical connection with the outside. The obtained substrate was ultrasonically washed with acetone and “Semicocrine (registered trademark) 56” (manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, respectively, and then washed with ultrapure water. Subsequently, it was ultrasonically cleaned with isopropyl alcohol for 15 minutes and then immersed in hot methanol for 15 minutes and dried. This substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the device, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁴ Pa or less. First, 4,4′-bis (N- (m-tolyl) -N-phenylamino) biphenyl was deposited as a hole transport material by a resistance heating method to a thickness of 150 nm. Next, 4,4′-bis (2,2-diphenylethenyl) biphenyl was deposited as a host material, and compound [14] was deposited as a dopant material to a thickness of 35 nm so that the doping concentration was 1%. Next, 1,3-bis (1,10-phenanthrolin-2-yl) benzene was laminated to a thickness of 15 nm as an electron transport material. The film thickness referred to here is a crystal oscillation type film thickness monitor display value. Next, the mask provided with 16 250 μm openings (corresponding to a remaining width of 50 μm and a pitch of 300 μm) by wet etching on a 50 μm thick Kovar plate was changed to be orthogonal to the ITO stripe in vacuum, It fixed with the magnet from the back surface so that a mask and ITO board | substrate might closely_contact | adhere. And after doping lithium with a 0.5 nm organic layer, aluminum was vapor-deposited 200 nm, and the 32x16 dot matrix element was produced. When this element was driven in matrix, characters could be displayed without crosstalk.

Claims (9)

A light-emitting element material comprising an anthracene compound represented by the following general formula (1).

(May be the same or different, respectively wherein R ¹ to R ⁸ represents hydrogen, an alkyl group, the aryl group, a heteroaryl group, shea Anomoto, ethynyl represented by silyl groups and represented by the following general formula (2) R ⁹ and R ¹⁰ may be the same or different from each other, and may be a phenyl group, an alkyl-substituted phenyl group, an alkoxy-substituted phenyl group, a heteroaryl group, or ethynyl represented by the following general formula (2) However, at least one of R ^{1 to} R ¹⁰ is an ethynyl group represented by the following general formula (2), and R ⁹ and R ¹⁰ are represented by the general formula (2) at the same time. Never become an ethynyl group.)

(Here, Ar ¹ is an aryl group or a heteroaryl group, and α represents a connecting portion with an anthracene skeleton.) 2. The light emitting device material according to claim 1, wherein either one of R ^{9 and} R ¹⁰ is an ethynyl group represented by the general formula (2). 2. The light emitting device material according to claim 1, wherein Ar ¹ is an unsubstituted aryl group, an aryl group substituted with a cyano group, or a heteroaryl group containing electron-accepting nitrogen. A light-emitting element having at least a light-emitting layer and an electron transport layer between an anode and a cathode and emitting light by electric energy, wherein the light-emitting element contains an anthracene compound represented by the general formula (1) Light emitting element.

(May be the same or different, respectively wherein R ¹ to R ⁸ represents hydrogen, an alkyl group, the aryl group, a heteroaryl group, shea Anomoto, ethynyl represented by silyl groups and represented by the following general formula (2) R ⁹ and R ¹⁰ may be the same or different from each other, and may be a phenyl group, an alkyl-substituted phenyl group, an alkoxy-substituted phenyl group, a heteroaryl group, or ethynyl represented by the following general formula (2) However, at least one of R ^{1 to} R ¹⁰ is an ethynyl group represented by the following general formula (2), and R ⁹ and R ¹⁰ are represented by the general formula (2) at the same time. Never become an ethynyl group.)

(Here, Ar ¹ is an aryl group or a heteroaryl group, and α represents a connecting portion with an anthracene skeleton.) The light-emitting element according to claim 4, wherein the light-emitting layer contains an anthracene compound represented by the general formula (1). 6. The light emitting device according to claim 5, wherein the light emitting layer contains a host material and a dopant material, and the anthracene compound represented by the general formula (1) acts as a dopant material. The light emitting device according to claim 6, wherein the host material is a compound represented by the following general formula (3).

(Wherein R ^{11 to} R ¹⁸ may be the same as or different from each other, hydrogen, alkyl group, cycloalkyl group, aralkyl group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, Ar ² and Ar are selected from aryl thioether groups, aryl groups, heteroaryl groups, halogens, cyano groups, aldehyde groups, carbonyl groups, ester groups, carbamoyl groups, amino groups, silyl groups, phosphino groups, and phosphine oxide groups. ³ represents an aryl group or a heteroaryl group.) 5. The light emitting device according to claim 4, wherein the electron transport layer contains a compound composed of a heteroaryl ring having electron-accepting nitrogen, and the compound composed of the heteroaryl ring is a compound formed only by a covalent bond. . The light emitting element according to claim 4, wherein the light emitting layer exhibits blue light emission having a peak wavelength at 420 nm to 490 nm.