WO2012176675A1

WO2012176675A1 - Light-emitting element

Info

Publication number: WO2012176675A1
Application number: PCT/JP2012/065171
Authority: WO
Inventors: 田中　大作; 富永　剛
Original assignee: 東レ株式会社
Priority date: 2011-06-23
Filing date: 2012-06-13
Publication date: 2012-12-27
Also published as: KR20140037826A; JPWO2012176675A1; TW201308710A

Abstract

Provided is an organic thin-film light-emitting element having improved light-emission efficiency, drive voltage, and durability life. This light-emitting element is characterized by including a compound having a triphenylene skeleton in a hole transport layer, and by either including a donor compound in an electron transport layer or using an acceptor compound in a hole injection layer.

Description

Light emitting element

The present invention relates to a light emitting element capable of converting electric energy into light. More specifically, the present invention relates to a light emitting element that can be used in fields such as a display element, a flat panel display, a backlight, illumination, interior, a sign, a signboard, an electrophotographic machine, and an optical signal generator.

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 fluorescent material. This study was conducted by C.D. W. Since Tang et al. Showed that organic thin film devices emit light with high brightness, they have been studied by many research institutions.

After that, as a result of many practical studies, organic thin-film light-emitting elements have been steadily put into practical use, such as being used in the main display of mobile phones. However, there are still many technical issues. Above all, it is one of the big issues to achieve both low voltage driving and long life of the device.

The driving voltage of the element depends greatly on the carrier transport material that transports carriers such as holes and electrons to the light emitting layer. Among these, a technique using a material having a triphenylene skeleton as a hole transport material is disclosed (for example, see Patent Documents 1 to 3).

Also, as one of the techniques for lowering the voltage of the device, a technique of doping a donor compound into a material used as an electron transport layer from the viewpoint of electron injection transport is disclosed (for example, see Patent Documents 4 to 6). Further, from the viewpoint of hole injection and transport, a technique of doping a hole transport material with an acceptor compound is disclosed (for example, Patent Documents 7 and 8).

JP-A-11-251063 JP 2005-259472 A JP 2009-292760 A JP 2003-347060 A JP 2002-352916 A Japanese Patent Laid-Open No. 2004-2297 JP 2010-1000062 A International Publication No. 2010/132236

However, in the prior art, a light emitting device that is driven at a low voltage, has high luminous efficiency, and has excellent durability life has not been found. For example, even though conventionally known hole transport materials and electron transport materials are excellent in hole transport properties and electron transport properties themselves, performance as a light emitting device is not necessarily improved when used in combination. Absent.

In particular, the technique of doping the electron transport layer with a donor compound as known in Patent Documents 4 to 6 has the effect of lowering the driving voltage, but causes a decrease in luminous efficiency and a decrease in durability life. It has been found by examination by the present inventors. The inventor presumed the reason as follows. The electron transport layer doped with an alkali metal has improved conductivity, and when this is used for the electron transport layer, the electron injection property from the cathode is good and the electron transport property is also excellent. However, due to its high performance, the inside of the light-emitting layer becomes excessive in electrons depending on the types of hole transport materials used in combination, and as a result, the above-described problems may occur.

On the other hand, the technique of doping the acceptor compound into the hole transport layer as known in Patent Documents 7 and 8 still has the effect of lowering the driving voltage, but depending on the hole transport material to be doped, it is significant. It has been found by the study by the present inventors that the effect of improving the durable life cannot be obtained. The inventor presumed the reason as follows. During driving, a single or doped acceptor compound diffuses in the hole transport layer, and the hole conductivity of the hole transport layer gradually changes during driving. For this reason, it is considered that the carrier balance gradually deviates from that before driving, causing a decrease in light emission efficiency, that is, deterioration.

An object of the present invention is to provide an organic thin-film light-emitting element that solves the problems of the prior art and has improved luminous efficiency, driving voltage, and durability life.

The present invention was made in consideration of the balance of mobility of electrons and holes in a light emitting device, and found an optimal combination as a material contained in a hole transport layer and an electron transport layer. is there. Further, the present inventors have found an optimum hole transport material for preventing diffusion during driving of the acceptor compound doped in the hole transport layer.

That is, one configuration of the present invention is a light-emitting element that includes at least a hole transport layer and an electron transport layer between an anode and a cathode and emits light by electric energy, and the hole transport layer has the following general formula ( 1) The compound represented by 1), wherein the electron transport layer is an alkali metal, an inorganic salt containing an alkali metal, a complex of an alkali metal and an organic substance, an alkaline earth metal, an inorganic salt containing an alkaline earth metal Or a light-emitting element containing a donor compound selected from the group consisting of a complex of an alkaline earth metal and an organic substance.

In the general formula (1), R ¹ to R ¹² may be the same or different, and are hydrogen, alkyl group, cycloalkyl group, amino group, aryl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl. Selected from the group consisting of a group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, a halogen, a cyano group, —P (═O) R ¹³ R ¹⁴ and a silyl group. R ¹³ and R ¹⁴ may be the same or different, and are an aryl group or a heteroaryl group. These substituents may be further substituted, and adjacent substituents may further form a ring. However, n of R ¹ to R ¹² is an amino group represented by —NR ¹⁵ R ¹⁶ . R ¹⁵ and R ¹⁶ may be the same or different and are selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group. n represents an integer of 1 to 6.

Another configuration of the present invention is a light emitting device that includes at least a hole transport layer and a hole injection layer between an anode and a cathode, and emits light by electric energy. It is a light emitting device containing a compound represented by the formula (1), wherein the hole injection layer is composed of an acceptor compound alone or contains an acceptor compound.

The light emitting device according to the present invention has an effect of being able to be driven at a low voltage and improving luminous efficiency and durability.

<Light Emitting Element According to First Configuration>
The light-emitting element according to the first configuration of the present invention is characterized in that a compound having a specific structure is used for each of the hole transport layer and the electron transport layer.

First, the compound represented by the general formula (1) will be described in detail. The hole transport layer of the light emitting device of the present invention contains a compound represented by the general formula (1).

Of these substituents, hydrogen may be deuterium. The alkyl group represents, for example, a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group, which is a substituent. It may or may not have. There is no restriction | limiting in particular in the additional substituent in the case of being substituted, For example, an alkyl group, an aryl group, etc. can be mentioned, This point is common also in the following description. The number of carbon atoms of the alkyl group is not particularly limited, but is usually in the range of 1 to 20 and more preferably 1 to 8 from the viewpoint of easy availability of raw materials and cost. Furthermore, since there exists a possibility that hole transport property may be inhibited when the carbon number of an alkyl group is large, a methyl group and an ethyl group are more preferable.

The cycloalkyl group represents, for example, a saturated alicyclic hydrocarbon group such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, etc., which may or may not have a substituent. Also good. Although carbon number of an alkyl group part is not specifically limited, Usually, it is the range of 3-20. Further, when the number of carbon atoms is large, the hole transport property may be inhibited, and therefore, a cyclopropyl, cyclopentyl, or cyclohexyl group is more preferable.

The amino group may or may not have a substituent, and examples of the substituent include an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group, and these substituents are further substituted. It may be.

The aryl group represents an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, a fluorenyl group, an anthracenyl group, a pyrenyl group, or a terphenyl group. The aryl group may or may not further have a substituent. There is no restriction | limiting in particular in the additional substituent in the case of being substituted, For example, an alkyl group, a cycloalkyl group, heteroaryl group, an alkoxy group, an amino group etc. can be mentioned. The number of carbon atoms of the aryl group is not particularly limited, but is usually in the range of 6 to 40.

The heterocyclic group is, for example, a cycloaliphatic group having atoms other than carbon, such as a pyranyl group, a piperidinyl group, and a cyclic amide group, and a furanyl group, a thiophenyl group, a pyridyl group, a quinolinyl group, a pyrazinyl group, Cyclic aromatic groups (heteroaryl groups) having one or more atoms other than carbon such as naphthyridyl group, benzofuranyl group, benzothiophenyl group, indolyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group in the ring Which may be unsubstituted or substituted. Of the heterocyclic groups, heteroaryl groups are preferred. There is no restriction | limiting in particular in the additional substituent in the case of being substituted, For example, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an amino group etc. can be mentioned. The number of carbon atoms of the heterocyclic group is not particularly limited, but is usually in the range of 2-30.

An alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond such as a vinyl group, an allyl group, or a butadienyl group, which may or may not have a substituent. The number of carbon atoms of the alkenyl group is not particularly limited, but is usually in 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 may have a substituent. You don't have to.

The alkynyl group indicates, for example, an unsaturated aliphatic hydrocarbon group containing a triple bond such as an ethynyl group, which may or may not have a substituent. The number of carbon atoms of the alkynyl group is not particularly limited, but is usually in the range of 2-20.

The alkoxy group refers to, for example, a functional group having an aliphatic hydrocarbon group bonded through an ether bond such as a methoxy group, an ethoxy group, or a propoxy group, and the aliphatic hydrocarbon group may have a substituent. It may not have. Although carbon number of an alkoxy group is not specifically limited, Usually, it is the range of 1-20. Furthermore, since there exists a possibility that hole transport property may be inhibited when the carbon number of an alkoxy group is large, it is more preferably a methoxy group or an ethoxy group.

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 hydrocarbon group of the alkylthio group may or may not have a substituent. Although carbon number of an alkylthio group is not specifically limited, Usually, it is the range of 1-20.

An aryl ether group refers to a functional group to which an aromatic hydrocarbon group is bonded via an ether bond, such as a phenoxy group, and the aromatic hydrocarbon group may or may not have a substituent. Good. Although carbon number of an aryl ether group is not specifically limited, Usually, it is the range of 6-40.

The aryl thioether group is a group in which an oxygen atom of an ether bond of an aryl ether group is substituted with a sulfur atom. The aromatic hydrocarbon group in the aryl ether group may or may not have a substituent. Although carbon number of an aryl ether group is not specifically limited, Usually, it is the range of 6-40.

Halogen means fluorine, chlorine, bromine and iodine.

In the substituent —P (═O) R ¹³ R ¹⁴ , R ¹³ and R ¹⁴ are an aryl group or a heteroaryl group, and in the substituent —P (═O) R ¹³ R ¹⁴ , an aryl group or a heteroaryl group Has the same meaning as above.

The silyl group refers to, for example, a functional group having a bond to a silicon atom such as a trimethylsilyl group, which may or may not have a substituent. The carbon number of the silyl group is not particularly limited, but is usually in the range of 3-20. The number of silicon is usually 1-6.

Adjacent substituents form a ring when any adjacent two substituents (for example, R ¹ and R ^{2 in} formula (1)) are bonded to each other to form a conjugated or non-conjugated condensed ring. It means that As a constituent element of the condensed ring, in addition to carbon, nitrogen, oxygen, sulfur, phosphorus and silicon atoms may be contained, or further condensed with another ring.

Preferred examples of R ¹ to R ¹² include hydrogen, an alkyl group, an amino group, an alkoxy group, an aryl group, or a heteroaryl group in consideration of the deposition stability (thermal stability) of the material, the synthesis cost, and the availability of raw materials. It is. More preferred are hydrogen, amino group, aryl group or heteroaryl group. In the case of an aryl group or heteroaryl group, an aryl group or heteroaryl group having 6 to 18 carbon atoms is preferable in consideration of vapor deposition stability (thermal stability) of the material. Specifically, a phenyl group, a naphthyl group, or biphenylyl. Group, fluorenyl group, anthracenyl group, phenanthryl group, pyrenyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group. These groups may further have a substituent.

In the general formula (1), n of R ¹ to R ¹² is an amino group represented by —NR ¹⁵ R ¹⁶ , and R ¹⁵ and R ¹⁶ are alkyl groups in view of synthesis cost and availability of raw materials. A group, an aryl group or a heteroaryl group is preferred. Among them, an aryl group or a heteroaryl group is preferable in consideration of vapor deposition stability (thermal stability), amorphous thin film stability (having a high glass transition temperature), and good hole transport properties. Specifically, an aryl group or heteroaryl group having 6 to 20 carbon atoms is preferable, and phenyl group, naphthyl group, biphenylyl group, terphenyl group, fluorenyl group, anthracenyl group, phenanthryl group, pyrenyl group, triphenylenyl group, dibenzofuran group. Preferred examples include nyl group, dibenzothiophenyl group, carbazolyl group and the like. These groups may further have a substituent. Among them, excellent amorphous thin film stability (high glass transition temperature) can be obtained, and the lifetime of the device can be extended, and if the energy gap (HOMO-LUMO energy difference) is narrowed, the light emitting layer is excited. A phenyl group, a naphthyl group, a biphenylyl group, a terphenyl group, a fluorenyl group, a phenanthryl group, and a triphenylenyl group are more preferable because there is no fear of deactivating the child energy.

In the general formula (1), n as the number of substituents —NR ¹⁵ R ¹⁶ represents an integer of 1 to 6, but n is preferably 1 to 3 in consideration of deposition stability (thermal stability), and more appropriate 2 or 3 is more preferable from the viewpoint of having a good ionization potential and facilitating injection of holes. When n = 1, it is preferable that R ¹ is —NR ¹⁵ R ¹⁶ in view of ease of synthesis. In the case of n = 2, considering the ease of synthesis, it is preferable that R ¹ and R ⁶ , R ² and R ⁵ , or R ³ and R ¹² are —NR ¹⁵ R ¹⁶ , and further suitable ionization potential From the viewpoint of having R ¹ , R ¹ and R ⁶ are more preferably —NR ¹⁵ R ¹⁶ . In the case of n = 3, considering the ease of synthesis, R ¹ , R ⁵ and R ⁹ or R ¹ , R ⁶ and R ⁹ are preferably —NR ¹⁵ R ¹⁶ , and an appropriate ionization potential is obtained. From the viewpoint of having R ¹ , R ^6, and R ⁹ are more preferably —NR ¹⁵ R ¹⁶ . In the case of n = 4, R ¹ , R ² , R ⁵ and R ⁶ , or R ¹ , R ⁶ , R ⁸ and R ¹¹ , or R ² , R ⁵ , R ⁸ and R are considered in consideration of the ease of synthesis. ¹¹ is preferably —NR ¹⁵ R ¹⁶ , and more preferably R ¹ , R ⁶ , R ⁸ and R ¹¹ are —NR ¹⁵ R ¹⁶ from the viewpoint of having an appropriate ionization potential.

The compound represented by the general formula (1) is not particularly limited, but specific examples include the following compounds.

The compound represented by the general formula (1) can be synthesized by combining known methods. A synthesis example of diamino type with n = 2 is shown below.

Also, as a monoamino type synthesis method of n = 1, for example, it can be easily synthesized by a coupling reaction using commercially available bromotriphenylene and a desired diarylamine using a palladium catalyst. Note that the synthesis method is not limited to these.

The electron transport layer in the light emitting device according to the first configuration of the present invention contains a donor compound. In the electron transport layer containing a donor compound, the carrier density in the electron transport layer is increased and the electron conductivity is improved as compared with an electron transport layer not containing the donor compound. Therefore, in combination with the conventional hole transporting material, the inside of the light emitting layer becomes excessive in electrons, and as a result, it is considered that the light emitting efficiency is lowered and the durability life is shortened. However, combining the electron transport layer containing the donor compound and the hole transport layer containing the compound represented by the general formula (1) has the effect of improving the light emission efficiency and the durability life while driving at a low voltage. It was found to be obtained. This is because the hole transport material represented by the general formula (1) has higher hole mobility and better hole injection characteristics than, for example, a well-known arylamine-based hole transport material. Therefore, it is considered that, when combined with the electron transport layer containing a donor compound, the excess of electrons in the light emitting layer is eliminated, and injection of electrons into the hole transport layer can be prevented.

The donor compound in the present invention is a compound that facilitates electron injection from the cathode or the electron injection layer to the electron transport layer by improving the electron injection barrier, and further improves the electrical conductivity of the electron transport layer.

Preferred examples of the donor compound in the present invention include an alkali metal, an inorganic salt containing an alkali metal, a complex of an alkali metal and an organic substance, an alkaline earth metal, an inorganic salt containing an alkaline earth metal, or an alkaline earth metal. And a complex of organic substance. Preferred types of alkali metals and alkaline earth metals include alkaline metals such as lithium, sodium, potassium, rubidium, and cesium that have a large effect of improving the electron transport ability with a low work function, and alkaline earths such as magnesium, calcium, cerium, and barium. A metal is mentioned.

In addition, the donor compound contained in the electron transport layer is preferably in the form of a complex with an inorganic salt or an organic substance rather than a single metal because it is easy to deposit in a vacuum and is excellent in handling. Furthermore, it is more preferable that it is in the state of a complex with an organic substance in terms of facilitating handling in the air and easy control of the addition concentration. Examples of inorganic salts include oxides such as LiO and Li ₂ O, nitrides, fluorides such as LiF, NaF, and KF, Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Rb ₂ CO ₃ , And carbonates such as Cs ₂ CO ₃ . Further, preferred examples of the alkali metal or alkaline earth metal include lithium and cesium from the viewpoint that a large low-voltage driving effect can be obtained. In addition, preferable examples of the organic substance when the donor compound is a complex of an alkali metal or an alkaline earth metal and an organic substance include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole. Etc. Among them, a complex of an alkali metal and an organic substance is preferable from the viewpoint that the effect of lowering the voltage of the light emitting device is larger, and a complex of lithium and an organic substance is more preferable from the viewpoint of ease of synthesis and thermal stability, Particularly preferred is lithium quinolinol, which can be obtained at a low cost. The electron transport layer may contain two or more donor compounds.

The preferred doping concentration varies depending on the material and the thickness of the doped region. For example, when the donor compound is an inorganic material such as an alkali metal or alkaline earth metal, the deposition rate ratio of the electron transport material and the donor compound is 10,000: It is preferable to use an electron transport layer by co-evaporation so as to be in the range of 1 to 2: 1. The deposition rate ratio is more preferably 100: 1 to 5: 1, further preferably 100: 1 to 10: 1. When the donor compound is a complex of a metal and an organic substance, the electron transport layer and the donor compound are co-deposited so that the deposition rate ratio of the electron transport material and the donor compound is in the range of 100: 1 to 1: 100. Is preferred. The deposition rate ratio is more preferably 10: 1 to 1:10, and more preferably 7: 3 to 3: 7.

Next, the electron transport material used in combination with the donor compound will be described. The electron transport material used in combination with the donor compound is not particularly limited, but is a compound having a skeleton in which a plurality of benzene rings are connected, such as biphenyl, terphenyl, and triphenylbenzene, and derivatives thereof, fluorene, fluoranthene, and benzofluoranthene. Compounds having a condensed polycyclic aromatic skeleton such as naphthalene, anthracene, phenanthrene, triphenylene, pyrene and derivatives thereof, styryl aromatic ring derivatives represented by 4,4′-bis (diphenylethenyl) biphenyl, perylene derivatives, Perinone derivatives, coumarin derivatives, naphthalimide derivatives, quinone derivatives such as anthraquinone and diphenoquinone, phosphorus oxide derivatives, carbazole derivatives and indole derivatives, tris (8-quinolinolato) aluminum (I I) alkali metal and alkaline earth metal other than quinolinol complexes such as, hydroxyazole complexes such as hydroxyphenyl oxazole complex, azomethine complexes, and tropolone metal complexes and flavonol metal complexes. Since the driving voltage can be reduced, the electron transport material is composed of an element selected from carbon, hydrogen, nitrogen, oxygen, silicon and phosphorus, and a compound having a heteroaryl ring structure containing electron-accepting nitrogen is used. preferable.

The electron-accepting nitrogen 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, has an excellent electron transporting ability, and can be used for an electron transporting layer to reduce the driving voltage of the light emitting element. Therefore, heteroaryl rings containing electron-accepting nitrogen have a high electron affinity. Examples of the heteroaryl ring containing an electron-accepting nitrogen include, for example, a pyridine ring, pyrazine ring, pyrimidine ring, triazine ring, quinoline ring, quinoxaline ring, acridine ring, naphthyridine ring, pyrimidopyrimidine ring, benzoquinoline ring, phenanthroline ring, Examples include an imidazole ring, an oxazole ring, 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.

Examples of these compounds having a heteroaryl ring structure include benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, phenanthroline. Derivatives, quinoxaline derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives and naphthyridine derivatives, phenanthroline derivatives and the like are preferable compounds. Among these derivatives, considering electrochemical stability, benzimidazole derivatives, pyridine derivatives, bipyridine derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, and oligopyridine derivatives are more preferable. Further, it is more preferable that these derivatives have a condensed polycyclic aromatic skeleton because the glass transition temperature is improved, the electron mobility is increased, and the effect of lowering the voltage of the light emitting element is great. Furthermore, considering that the device durability life is improved, the synthesis is easy, and the availability of raw materials is easy, the condensed polycyclic aromatic skeleton is particularly preferably an anthracene skeleton, a phenanthrene skeleton or a pyrene skeleton. The electron transport material may be used alone, but two or more of the electron transport materials may be mixed and used, or one or more of the other electron transport materials may be mixed with the electron transport material.

The electron transport material used in combination with the donor compound is preferably a material containing electron-accepting nitrogen as described above, or the addition of a donor compound even if the material does not contain electron-accepting nitrogen. If the conductivity and the electron injecting / transporting property are improved, it is also suitable.

The electron transport material used in combination with such a donor compound is not particularly limited, but specific examples include the following.

In addition, the structure which concerns on the other layer of a light emitting element is mentioned later.

<Light Emitting Element According to Second Configuration>
Next, the light-emitting element according to the second configuration of the present invention is characterized in that a compound having a specific structure is used for the hole transport layer and an acceptor compound is used for the hole injection layer.

The compound used for the hole transport layer is a compound represented by the general formula (1), and the detailed description thereof is the same as the description of the light-emitting element according to the first configuration. From the viewpoint of preventing the diffusion of the acceptor compound, it is preferable that the glass transition temperature in the amorphous film state is high or the interaction with the acceptor compound is strong. Therefore, at least one of R ¹⁵ and R ^{16 in} the general formula (1) Is preferably a polyphenyl group or a condensed aromatic hydrocarbon group. Here, the polyphenyl group represents a substituent in which a plurality of benzene rings such as a biphenyl group and a terphenyl group are connected, and preferred polyphenyl groups are a biphenyl group, a terphenyl group and a quarterphenyl group. Furthermore, a biphenyl group and a terphenyl group are preferable. Preferred examples of the condensed aromatic hydrocarbon group include fluorenyl group, benzofluorenyl group, dibenzofluorenyl group, naphthalenyl group, phenanthrenyl group, triphenylenyl group, anthracenyl group, benzoanthracenyl group, pyrenyl group, chrysenyl group, A dibenzocrisenyl group is mentioned. Of these, a fluorenyl group, a naphthalenyl group, a phenanthrenyl group, and a triphenylenyl group are more preferable.

In addition, the hole injection layer in the light emitting device according to the second configuration of the present invention contains an acceptor compound. More specifically, the hole injection layer is composed of an acceptor compound alone, or the acceptor compound is doped with another hole injection material or a compound represented by the general formula (1). It is used. When a hole injection layer having an acceptor compound is used, although there is an effect in driving the device at a low voltage, there is a case where the effect of greatly improving the durability life cannot be obtained depending on the combined hole transport material. This is thought to be due to the fact that single or doped acceptor compounds diffuse into the hole transport layer during driving, and the hole conductivity of the hole injection layer or hole transport layer changes. It is done. However, when the compound represented by the general formula (1) is used for the hole transport layer and the hole injection layer has an acceptor compound, it is found that the effect of driving at a low voltage and improving the durability life can be obtained. It was done. This is considered to be due to the following reason. That is, since the compound represented by the general formula (1) has a glass transition temperature higher than that of the conventional hole transport material, and further has a triphenylene ring that is a large π-electron plane at the center, the acceptor compound. It is considered that the diffusion during the driving of the acceptor compound can be prevented. For this reason, it is considered that the hole conductivity of the hole injection layer or the hole transport layer does not easily change during driving, and it is difficult to cause a decrease in light emission efficiency due to a change in carrier balance.

The acceptor compound is a material that forms a charge transfer complex with a material that forms a hole-injecting layer in contact with a hole-transporting layer when used as a single-layer film, and a material that forms a hole-injecting layer when used as a dope. When such a material is used, the conductivity of the hole injection layer is improved, which contributes to lowering of the driving voltage of the device, and the effects of improving the light emission efficiency and improving the durability life can be obtained.

Examples of acceptor compounds include metal chlorides such as iron (III) chloride, aluminum chloride, gallium chloride, indium chloride, antimony chloride, metal oxides such as molybdenum oxide, vanadium oxide, tungsten oxide, ruthenium oxide, A charge transfer complex such as tris (4-bromophenyl) aminium hexachloroantimonate (TBPAH). In addition, organic compounds having a nitro group, cyano group, halogen or trifluoromethyl group in the molecule, quinone compounds, acid anhydride compounds, fullerenes, and the like are also preferably used. Specific examples of these compounds include hexacyanobutadiene, hexacyanobenzene, tetracyanoethylene, tetracyanoquinodimethane (TCNQ), tetrafluorotetracyanoquinodimethane (F4-TCNQ), 2, 3, 6, 7 , 10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN6), p-fluoranyl, p-chloranil, p-bromanyl, p-benzoquinone, 2,6-dichlorobenzoquinone 2,5-dichlorobenzoquinone, tetramethylbenzoquinone, 1,2,4,5-tetracyanobenzene, o-dicyanobenzene, p-dicyanobenzene, 1,4-dicyanotetrafluorobenzene, 2,3-dichloro-5 , 6-Dicyanobenzoquinone, p-dinitrobenzene, m-dini Lobenzene, o-dinitrobenzene, p-cyanonitrobenzene, m-cyanonitrobenzene, o-cyanonitrobenzene, 1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 1-nitronaphthalene, 2-nitronaphthalene, 1,3-dinitro Naphthalene, 1,5-dinitronaphthalene, 9-cyanoanthracene, 9-nitroanthracene, 9,10-anthraquinone, 1,3,6,8-tetranitrocarbazole, 2,4,7-trinitro-9-fluorenone, 2 , 3,5,6-tetracyanopyridine, maleic anhydride, phthalic anhydride, C60, and C70.

Among these, metal oxides and cyano group-containing compounds are preferable because they are easy to handle and can be easily deposited, so that the above-described effects can be easily obtained. Examples of preferred metal oxides include molybdenum oxide, vanadium oxide, or ruthenium oxide. Among the cyano group-containing compounds, (a) a compound having at least one electron-accepting nitrogen other than the nitrogen atom of the cyano group in the molecule and further having a cyano group, (b) a halogen and a cyano group in the molecule (C) a compound having both a carbonyl group and a cyano group in the molecule, or (d) an electron-accepting nitrogen other than the nitrogen atom of the cyano group, a halogen and a cyano group. A compound having all is more preferable because it becomes a strong electron acceptor. Specific examples of such a compound include the following compounds.

In any case where the hole injection layer is composed of an acceptor compound alone or when the hole injection layer is doped with an acceptor compound, the hole injection layer may be a single layer, A plurality of layers may be laminated. In addition, the hole injection material used in combination when the acceptor compound is doped is preferably a compound represented by the general formula (1) from the viewpoint that the hole injection barrier to the hole transport layer can be relaxed. More preferably, it is the same compound as the pore transport layer.

When the acceptor compound is doped in the hole injection layer, the material used for the hole injection layer is not particularly limited except that the material represented by the general formula (1) is used as it is. , 4′-bis (N- (3-methylphenyl) -N-phenylamino) biphenyl (TPD), 4,4′-bis (N- (1-naphthyl) -N-phenylamino) biphenyl (NPD), 4,4′-bis (N, N-bis (4-biphenylyl) amino) biphenyl (TBDB), bis (N, N′-diphenyl-4-aminophenyl) -N, N-diphenyl-4,4′- Benzidine derivatives such as diamino-1,1′-biphenyl (TPD232), 4,4 ′, 4 ″ -tris (3-methylphenyl (phenyl) amino) triphenylamine (m-MTDATA) A group of materials called starburst arylamines such as 4,4 ′, 4 ″ -tris (1-naphthyl (phenyl) amino) triphenylamine (1-TNATA), bis (N-arylcarbazole) or bis (N-alkyl) Biscarbazole derivatives such as carbazole), pyrazoline derivatives, stilbene compounds, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, porphyrin derivatives and other heterocyclic compounds, and polymer systems side by side with the monomers Polycarbonate, styrene derivatives, polythiophene, polyaniline, polyfluorene, polyvinyl carbazole, polysilane, etc. used in the chain are used. Among them, there are more benzidine derivatives and starburst arylamine group materials from the viewpoint of having a shallower HOMO level than the compound represented by the general formula (1) and smoothly injecting and transporting holes from the anode to the hole transport layer. Preferably used.

Next, an embodiment of the light emitting device in the present invention will be described in detail with an example. The following explanation applies to both the first configuration and the second configuration unless otherwise specified. The light-emitting element of the present invention includes an anode, a cathode, and at least a hole transport layer and an electron transport layer or a hole transport layer and a hole injection layer between the anode and the cathode.

The layer structure between the anode and the cathode in such a light-emitting element includes a hole injection layer / a hole transport layer / a light emission in addition to a structure composed of a hole transport layer / a light emission layer / an electron transport layer in the first configuration. Examples of the layer structure include layer / electron transport layer, hole transport layer / light emitting layer / electron transport layer / electron injection layer, hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer. Each of the layers may be a single layer or a plurality of layers. In addition, in the second configuration, in addition to the configuration consisting of a hole injection layer / hole transport layer / light emitting layer, a hole injection layer / hole transport layer / light emitting layer / electron transport layer, hole injection layer / hole transport Examples include a layered structure of layer / light emitting layer / electron transport layer / electron injection layer. Each of the above layers may be either a single layer or a plurality of layers.

The compound represented by the general formula (1) is contained in the hole transport layer in the light emitting device. The hole transport layer is a layer that transports holes injected from the anode to the light emitting layer. The hole transport layer may be a single layer or may be configured by laminating a plurality of layers. Since the compound represented by the general formula (1) has a high electron blocking performance, the compound represented by the general formula (1) is used from the viewpoint of preventing intrusion of electrons when it is composed of a plurality of layers. The hole transport layer contained is preferably in direct contact with the light emitting layer.

The hole transport layer may be composed of only the compound represented by the general formula (1), or may be mixed with other materials as long as the effects of the present invention are not impaired. In this case, as other materials used, for example, 4,4′-bis (N- (3-methylphenyl) -N-phenylamino) biphenyl (TPD), 4,4′-bis (N- (1 -Naphthyl) -N-phenylamino) biphenyl (NPD), 4,4'-bis (N, N-bis (4-biphenylyl) amino) biphenyl (TBDB), bis (N, N'-diphenyl-4-amino) Benzidine derivatives such as phenyl) -N, N-diphenyl-4,4′-diamino-1,1′-biphenyl (TPD232), 4,4 ′, 4 ″ -tris (3-methylphenyl (phenyl) amino) triphenyl Starburst aryl such as amine (m-MTDATA), 4,4 ′, 4 ″ -tris (1-naphthyl (phenyl) amino) triphenylamine (1-TNATA) A group of materials called min, biscarbazole derivatives such as bis (N-arylcarbazole) or bis (N-alkylcarbazole), pyrazoline derivatives, stilbene compounds, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanines Derivatives, heterocyclic compounds such as porphyrin derivatives, in the case of polymer systems, polycarbonates and styrene derivatives, polythiophene, polyaniline, polyfluorene, polyvinylcarbazole, polysilane and the like having the above-mentioned monomer in the side chain are exemplified.

Next, the electron transport layer in the present invention will be described. The electron transport layer is a layer that transports electrons injected from the cathode to the light emitting layer. In the light emitting device according to the first structure of the present invention, the electron transport layer contains a donor compound, but in the light emitting device according to the second structure, the electron transport also contains a donor compound. Is preferred. The electron transport layer may be a single layer or a plurality of layers may be laminated. In the case where a plurality of layers are stacked and a donor compound is used, any one layer may contain the donor compound. When the donor compound is an inorganic material such as an alkali metal, an alkaline earth metal, or oxides, nitrides, fluorides, or carbonates thereof, if the layer containing these is in direct contact with the light emitting layer, the light emitting layer Therefore, it is preferable that the layer containing the donor compound is not in direct contact with the light emitting layer. However, when the donor compound is a complex with an organic substance, the light emitting layer is not easily quenched, and thus the layer containing the donor compound may be in direct contact with the light emitting layer. When a plurality of electron transport layers are stacked, the undoped electron transport material and the doped electron transport material may be the same or different. In addition, the electron transport layer containing a donor compound in the present invention may be used as a charge generation layer in a tandem structure type element that connects a plurality of light emitting elements.

The hole injection layer is a layer inserted between the anode and the hole transport layer. In the light emitting device according to the second configuration of the present invention, the hole injection layer is composed of an acceptor compound alone, or the acceptor compound is used by doping another hole injection material. Similarly, in the light-emitting element according to the configuration 1, it is preferable that the hole injection layer is composed of the acceptor compound alone or the acceptor compound is doped into another hole injection material. The hole injection layer may be either a single layer or a plurality of layers stacked. If a hole injection layer is present between the positive hole transport layer containing the compound represented by the general formula (1) and the anode, it not only operates at a lower voltage and the durability life is improved, but also the carrier of the device. This is preferable because the balance is improved and the luminous efficiency is improved. In addition, the acceptor compound in the present invention alone may be used, or the hole injection layer containing the acceptor compound may be used as a charge generation layer in a tandem structure type element connecting a plurality of light emitting elements.

The anode is not particularly limited as long as it can efficiently inject holes into the organic layer, but it is preferable to use a material having a relatively large work function. Examples of the material for the anode include conductive metal oxides such as tin oxide, indium oxide, indium zinc oxide, and indium tin oxide (ITO), metals such as gold, silver, and chromium, copper iodide, and copper sulfide. Examples include inorganic conductive materials, conductive polymers such as polythiophene, polypyrrole, and polyaniline. These electrode materials may be used alone, or a plurality of materials may be laminated or mixed.

The resistance of the anode is not limited as long as a current sufficient for light emission of the light emitting element can be supplied, but it is desirable that the resistance is low in terms of power consumption of the light emitting element. For example, if the resistance is 300Ω / □ or less, it functions as an electrode. However, since it is now possible to supply an ITO substrate of about 10Ω / □, it is possible to use a low resistance product of 100Ω / □ or less. Particularly desirable. The thickness of the anode 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, it is preferable to form the anode on the 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 method for forming the anode is not particularly limited, and for example, an electron beam method, a sputtering method, a chemical reaction method, or the like can be used.

The material used for the cathode is not particularly limited as long as it can efficiently inject electrons into the organic layer, but platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium , Cesium, calcium and magnesium, and alloys thereof. Lithium, sodium, potassium, cesium, calcium, magnesium, or alloys containing these low work function metals are effective for increasing the electron injection efficiency and improving device characteristics. However, since these low work function metals are generally unstable in the atmosphere, the organic layer is doped with a small amount of lithium or magnesium (1 nm or less in the thickness gauge display of vacuum deposition) to stabilize the organic layer. A preferred example is a method for obtaining a high electrode. 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, inorganic substances such as silica, titania and silicon nitride, polyvinyl alcohol, polyvinyl chloride Lamination of organic polymer compounds such as hydrocarbon polymer compounds is a preferred example. The method for forming the cathode is not particularly limited, and for example, resistance heating, electron beam, sputtering, ion plating and coating can be used.

The light emitting layer may be either a single layer or a plurality of layers, each formed by a light emitting material (host material, dopant material), which may be a mixture of a host material and a dopant material or a host material alone, Either is acceptable. 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. From the viewpoint of efficiently using electric energy and obtaining light emission with high color purity, the light emitting layer is preferably composed of a mixture of a host material and a dopant material. Further, the host material and the dopant material may be either one kind or a plurality of combinations, respectively. The dopant material may be included in the entire host material or may be partially included. The dopant material may be laminated or dispersed. The dopant material can control the emission color. When the amount of the dopant material is too large, a concentration quenching phenomenon occurs, so that it is preferably used in an amount of 20% by mass or less, more preferably 10% by mass or less based on the host material. The doping method can be formed by a co-evaporation method with a host material, but may be simultaneously deposited after being previously mixed with the host material.

Specifically, the light-emitting material includes condensed ring derivatives such as anthracene and pyrene, which have been known as light emitters, metal chelated oxinoid compounds such as tris (8-quinolinolato) aluminum, bisstyrylanthracene derivatives, diesters, and the like. Bisstyryl derivatives such as styrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, oxadiazole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole In derivatives, indolocarbazole derivatives, and polymer systems, polyphenylene vinylene derivatives, polyparaphenylene derivatives, polythiophene derivatives, etc. can be used, but are not particularly limited. Not shall.

The host material contained in the light emitting material is not particularly limited, but is a compound having a condensed aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, indene, and derivatives thereof, N, Aromatic amine derivatives such as N′-dinaphthyl-N, N′-diphenyl-4,4′-diphenyl-1,1′-diamine, metal chelating oxinoids including tris (8-quinolinato) aluminum (III) Compounds, bisstyryl derivatives such as distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives For thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, polymer systems, polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinyl carbazole derivatives, polythiophene derivatives, etc. can be used, but in particular limited It is not done. The dopant material is not particularly limited, but is a compound having a condensed aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, triphenylene, perylene, fluoranthene, fluorene, indene or a derivative thereof (for example, 2- (benzothiazole-2) -Yl) -9,10-diphenylanthracene, 5,6,11,12-tetraphenylnaphthacene), furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9'-spirobisilafluorene, benzo Compounds having heteroaryl rings such as thiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline, pyridine, pyrazine, naphthyridine, quinoxaline, pyrrolopyridine, thioxanthene Derivatives thereof, borane derivatives, distyrylbenzene derivatives, 4,4′-bis (2- (4-diphenylaminophenyl) ethenyl) biphenyl, 4,4′-bis (N- (stilben-4-yl) -N— Aminostyryl derivatives such as phenylamino) stilbene, aromatic acetylene derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyromethene derivatives, diketopyrrolo [3,4-c] pyrrole derivatives, 2,3,5,6-1H, Coumarin derivatives such as 4H-tetrahydro-9- (2′-benzothiazolyl) quinolidino [9,9a, 1-gh] coumarin, azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole and triazole and their metals Complex and N, '- diphenyl -N, etc. N'- di (3-methylphenyl) -4,4'-aromatic amine derivative typified by diphenyl-1,1'-diamine can be used.

Further, a phosphorescent material may be included in the light emitting layer. A phosphorescent material is a material that exhibits phosphorescence even at room temperature. As a dopant, it is basically necessary to obtain phosphorescence even at room temperature, but it is not particularly limited, and iridium (Ir), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt ), Organometallic complex compounds containing at least one metal selected from the group consisting of osmium (Os) and rhenium (Re). Among these, from the viewpoint of having a high phosphorescence emission yield even at room temperature, an organometallic complex having iridium or platinum is more preferable. Hosts of phosphorescent materials include indole derivatives, carbazole derivatives, indolocarbazole derivatives, pyridine, pyrimidine, nitrogen-containing aromatic compound derivatives having a triazine skeleton, polyarylbenzene derivatives, spirofluorene derivatives, truxene derivatives, triphenylene derivatives, etc. A compound containing a chalcogen element such as an aromatic hydrocarbon compound derivative, a dibenzofuran derivative or a dibenzothiophene derivative, or an organometallic complex such as a beryllium quinolinol complex is preferably used. As long as holes are smoothly injected and transported from the respective transport layers, the present invention is not limited thereto. Two or more triplet light-emitting dopants may be contained, or two or more host materials may be contained. Further, one or more triplet light emitting dopants and one or more fluorescent light emitting dopants may be contained.

Preferred phosphorescent dopants are not particularly limited, but specific examples include the following.

In addition, the preferred host of the phosphorescent light emitting layer is not particularly limited, but specific examples include the following.

The compound represented by the general formula (1) has a high triplet level in addition to good hole injection and transport properties and high electron blocking performance. Therefore, when the phosphorescence layer and the hole transport layer containing the compound represented by the general formula (1) are combined, triplet energy transfer from the phosphorescence layer to the hole transport layer is suppressed, Thermal deactivation of phosphorescence energy in the transport layer can be prevented. For this reason, it is possible to prevent a decrease in light emission efficiency and to obtain a light emitting element with low voltage drive and long life, which is preferable.

In the present invention, an electron injection layer may be provided between the cathode and the electron transport layer. In general, the electron injection layer is inserted for the purpose of assisting injection of electrons from the cathode to the electron transport layer, but in the case of insertion, the compound having a heteroaryl ring structure containing the electron accepting nitrogen described above is used as it is. Alternatively, a layer containing the above donor compound may be used. An insulator or a semiconductor inorganic substance can also be used for the electron injection layer. Use of these materials is preferable because a short circuit of the light emitting element can be effectively prevented and the electron injection property can be improved. As such an insulator, it is preferable to use at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides and alkaline earth metal halides. If the electron injection layer is composed of these alkali metal chalcogenides or the like, it is more preferable because the electron injection property can be further improved. Specifically, preferred alkali metal chalcogenides include, for example, Li ₂ O, Na ₂ S, and Na ₂ Se, and preferred alkaline earth metal chalcogenides include, for example, CaO, BaO, SrO, BeO, BaS, and CaSe. Is mentioned. Further, preferable alkali metal halides include, for example, LiF, NaF, KF, LiCl, KCl, and NaCl. Examples of preferable alkaline earth metal halides include fluorides such as CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ and BeF ₂ , and halides other than fluorides. Furthermore, a complex of an organic substance and a metal is also preferably used. When an insulator or a semiconductor inorganic material is used for the electron injection layer, if the film thickness is too large, there may be a problem that the light emitting element is insulated or the driving voltage becomes high. That is, there is a possibility that the film thickness margin of the electron injection layer is reduced, which may lead to a decrease in yield at the time of manufacturing a light-emitting element. Preferable examples of the organic substance in such a complex of an organic substance and a metal include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, hydroxytriazole and the like. Among these, a complex of an alkali metal and an organic substance is preferable, a complex of lithium and an organic substance is more preferable, and lithium quinolinol is particularly preferable.

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

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

In the matrix method, pixels for display are arranged two-dimensionally such as a lattice shape or a mosaic shape, and characters and images are displayed 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. However, 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. Although the structure of the line sequential drive is simple, the active matrix may be superior in consideration of the operation characteristics, and it is necessary to use it depending on the application.

The segment system in the present invention is a system in which a pattern is formed so as to display predetermined information and a region determined by the arrangement of the pattern 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, etc. The matrix display and the segment display may coexist in the same panel.

The light-emitting element 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, the light-emitting element of the present invention is preferably used for a backlight for a liquid crystal display device, particularly a personal computer for which a reduction in thickness is being considered, and a backlight that is thinner and lighter than conventional ones can be provided.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. In addition, the number of the compound in each following Example points out the number of the compound described above. In Tables 1 to 5, the first electron transporting layer is an electron transporting layer in contact with the light emitting layer, and the second electron transporting layer is not in contact with the light emitting layer, and is further laminated on the first electron transporting layer. Refers to the electron transport layer formed. However, when the first electron transport layer is “none”, the electron transport layer is composed of only the second electron transport layer, and the second electron transport layer is in contact with the light emitting layer.

<Examples 1 to 21: Light-emitting devices having a compound represented by the general formula (1) in the hole transport layer and a donor compound in the electron transport layer>
Example 1
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. As a hole transport layer, HT-1 was deposited to 60 nm by a resistance heating method. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as the second electron transport layer, the compound E-1 is used as the electron transport material, Liq is used as the donor compound, and the deposition rate ratio of E-1 and Liq is 1: 1. Laminated.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 5.4 V and an external quantum efficiency of 4.1%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 160 hours. Compounds HT-1, H-1, D-1, E-1, and Liq are the compounds shown below.

(Examples 2 to 7)
Using the materials described in Table 1 as the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, and the second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 1. The results of each example are shown in Table 1. HT-2, HT-3, HT-4, HT-5, HT-6, and HT-7 are the compounds shown below.

(Example 8)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. As a hole transport layer, HT-1 was deposited to 60 nm by a resistance heating method. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, E-1 is vapor-deposited as a first electron transport layer at a thickness of 5 nm, compound E-1 is used as an electron transport material as a second electron transport layer, cesium is used as a donor compound, and E-1 and cesium are deposited. The layers were laminated to a thickness of 15 nm so that the ratio was 20: 1.
Next, magnesium and silver were vapor-deposited 1000 nm so that mass ratio might be 1: 1, and it was set as the cathode, and the 5 * 5-mm square element was produced. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The light-emitting element had characteristics of 1000 cd / m ^{2 and} emitted blue light with a driving voltage of 5.2 V and an external quantum efficiency of 4.2%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 164 hours.

(Examples 9 to 21)
Using the materials described in Table 1 as the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, the first electron transport layer, and the second electron transport layer, a light emitting device was produced in the same manner as in Example 8. evaluated. The results of each example are shown in Table 1. E-2 is a compound shown below.

<Examples 22 to 77: Light-emitting device having a compound represented by the general formula (1) in the hole transport layer and an acceptor compound in the hole injection layer>
(Example 22)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. By the resistance heating method, first, HAT-CN6, which is an acceptor compound, was deposited as a hole injection layer by 10 nm, and then HT-1 was deposited as a hole transport layer by 50 nm. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as a second electron transport layer, Compound E-1 was laminated to an electron transport material to a thickness of 20 nm.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 5.2 V and an external quantum efficiency of 4.1%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time for a 20% decrease from the initial luminance was 162 hours. HAT-CN6 is a compound shown below.

(Examples 23 to 28)
Using the materials described in Table 2 as a hole injection layer, a hole transport layer, a light emitting layer host material, a light emitting layer dopant material, and a second electron transport layer, a light emitting device was fabricated and evaluated in the same manner as in Example 22. did. The results of each example are shown in Table 2.

(Example 29)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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, HT-1 was used as a hole injection material as a hole injection layer and F4-TCNQ was used as an acceptor compound by a resistance heating method, and 30 nm was deposited so that the acceptor compound had a doping concentration of 10% by mass. Next, 30 nm of HT-1 was deposited as a hole transport layer. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as a second electron transport layer, Compound E-1 was laminated to an electron transport material to a thickness of 20 nm.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 5.2 V and an external quantum efficiency of 4.2%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 159 hours. F4-TCNQ is a compound shown below.

(Examples 30 to 35)
Using the materials described in Table 2 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 29. did. The results of each example are shown in Table 2.

(Example 36)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. By resistance heating, molybdenum oxide (MoO ₃ ) was first deposited as a hole injection layer by 1 nm, and then HT-1 was deposited as a hole transport layer by 59 nm. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as a second electron transport layer, Compound E-1 was laminated to an electron transport material to a thickness of 20 nm.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 5.2 V and an external quantum efficiency of 4.2%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time required for a 20% reduction from the initial luminance was 157 hours.

(Examples 37 to 42)
Using the materials described in Table 2 as a hole injection layer, a hole transport layer, a light emitting layer host material, a light emitting layer dopant material, and a second electron transport layer, a light emitting device was fabricated and evaluated in the same manner as in Example 36. did. The results of each example are shown in Table 2.

(Examples 43 to 49)
Using the materials described in Table 2 as a hole injection layer, a hole transport layer, a light emitting layer host material, a light emitting layer dopant material, and a second electron transport layer, a light emitting device was fabricated and evaluated in the same manner as in Example 22. did. The results of each example are shown in Table 2.

(Examples 50 to 56)
Using the materials described in Table 2 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 29. did. The results of each example are shown in Table 2.

(Examples 57 to 63)
Using the materials described in Table 2 as a hole injection layer, a hole transport layer, a light emitting layer host material, a light emitting layer dopant material, and a second electron transport layer, a light emitting device was fabricated and evaluated in the same manner as in Example 36. did. The results of each example are shown in Table 2.

(Example 64)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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, HT-1 was used as a hole injection material as a hole injection layer and PD-1 was used as an acceptor compound by a resistance heating method, and vapor deposition was performed at 30 nm so that the acceptor compound had a doping concentration of 3 mass%. Next, 30 nm of HT-1 was deposited as a hole transport layer. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as a second electron transport layer, Compound E-1 was laminated to an electron transport material to a thickness of 20 nm.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light-emitting element at 1000 cd / m ² were a driving voltage of 5.1 V and an external quantum efficiency of 4.3%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time to decrease 20% from the initial luminance was 172 hours. PD-1 is a compound shown below.

(Examples 65 to 77)
Using the materials described in Table 3 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 64. did. The results of each example are shown in Table 3.

<Comparative Examples 1 to 14: The hole transport layer has the compound represented by the general formula (1), but the electron transport layer does not have a donor compound and does not have a hole injection layer containing an acceptor compound. Light emitting element>
(Comparative Example 1)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. As a hole transport layer, HT-1 was deposited to 60 nm by a resistance heating method. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as a second electron transport layer, Compound E-1 was laminated to a thickness of 20 nm on the electron transport material.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 6.6 V and an external quantum efficiency of 3.1%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 135 hours.

(Comparative Examples 2 to 14)
Using the materials described in Table 3 as the hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was prepared and evaluated in the same manner as in Comparative Example 1. The results of each comparative example are shown in Table 4.

<Comparative Examples 15 to 23: Light-emitting devices having a donor compound in the electron transport layer but not having the compound represented by the general formula (1) in the hole transport layer>
(Comparative Examples 15 to 17)
Using the materials described in Table 4 as the hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 1. The results of each comparative example are shown in Table 4. HT-8, HT-9 and HT-10 are the compounds shown below.

(Comparative Examples 18 to 23)
Using the materials described in Table 4 as the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, the first electron transport layer, and the second electron transport layer, a light emitting device was produced in the same manner as in Example 8, evaluated. The results of each comparative example are shown in Table 4.

From Tables 1 and 4, according to the comparison between Examples 1 to 7 and Comparative Examples 1 to 7, and Examples 15 to 21 and Comparative Examples 8 to 14, the compound represented by the general formula (1) was added to the hole transport layer. When used, it can be seen that when the electron transport layer contains a donor compound, effects such as low voltage driving, improved luminous efficiency, and improved durable life can be seen. Further, in comparison with Examples 1 to 7 and Comparative Examples 15 to 17, Examples 8 to 14 and Comparative Examples 18 to 20, and Examples 15 to 21 and Comparative Examples 21 to 23, the electron transport layer contains a donor compound. When it contains, it turns out that the effect of a low voltage drive, the improvement of luminous efficiency, and the improvement of a durable life is seen by using the compound represented by General formula (1) for a positive hole transport layer.

<Comparative Examples 24 to 47: A light emitting device having an acceptor compound in the hole injection layer but not having the compound represented by the general formula (1) in the hole transport layer>
(Comparative Examples 24-26)
Using the materials described in Table 5 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 22. did. The results of each example are shown in Table 5.

(Comparative Examples 27 to 29)
Using the materials described in Table 5 as the hole injection layer, the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, and the second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 29. did. The results of each example are shown in Table 5.

(Comparative Examples 30 to 32)
Using the materials described in Table 5 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 36. did. The results of each example are shown in Table 5.

(Comparative Examples 33 to 35)
Using the materials described in Table 5 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 22. did. The results of each example are shown in Table 5.

(Comparative Examples 36-38)
Using the materials described in Table 5 as the hole injection layer, the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, and the second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 29. did. The results of each example are shown in Table 5.

(Comparative Examples 39 to 41)
Using the materials described in Table 5 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 36. did. The results of each example are shown in Table 5.

(Comparative Examples 42 to 47)
Using the materials described in Table 5 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 64. did. The results of each example are shown in Table 5.

From Tables 2, 3 and 5, Examples 22 to 28 and Comparative Examples 24 to 26, Examples 29 to 35, Comparative Examples 27 to 29, Examples 36 to 42, Comparative Examples 30 to 32, and Examples 43 to 49 Comparative Examples 33 to 35, Examples 50 to 56 and Comparative Examples 36 to 38, Examples 57 to 63 and Comparative Examples 39 to 41, Examples 64 to 70, Comparative Examples 42 to 44, Examples 71 to 77 and Comparative Examples By comparison with 45 to 47, when the hole injection layer is composed of an acceptor compound alone or contains an acceptor compound, the compound represented by the general formula (1) is used for the hole transport layer. Thus, it can be seen that effects such as low voltage driving, improved luminous efficiency, and improved durable life can be seen.

<Examples 78 to 138: Light-emitting devices having a compound represented by the general formula (1) in the hole transport layer, a donor compound in the electron transport layer, and an acceptor compound in the hole injection layer>
(Example 78)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. By the resistance heating method, first, HAT-CN6, which is an acceptor compound, was deposited as a hole injection layer by 10 nm, and then HT-1 was deposited as a hole transport layer by 50 nm. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as the second electron transport layer, the compound E-1 is used as the electron transport material, Liq is used as the donor compound, and the deposition rate ratio of E-1 and Liq is 1: 1. Laminated.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 4.1 V and an external quantum efficiency of 5.5%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 305 hours.

(Examples 79 to 82)
Using the materials described in Table 6 as a hole injection layer, a hole transport layer, a light emitting layer host material, a light emitting layer dopant material, and a second electron transport layer, a light emitting device was fabricated and evaluated in the same manner as in Example 78. did. The results of each example are shown in Table 6.

(Example 83)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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, HT-1 was used as a hole injection material as a hole injection layer and F4-TCNQ was used as an acceptor compound by a resistance heating method, and 30 nm was deposited so that the acceptor compound had a doping concentration of 10% by mass. Next, 30 nm of HT-1 was deposited as a hole transport layer. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as the second electron transport layer, the compound E-1 is used as the electron transport material, Liq is used as the donor compound, and the deposition rate ratio of E-1 and Liq is 1: 1. Laminated.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 4.1 V and an external quantum efficiency of 5.3%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 310 hours.

(Examples 84 to 87)
Using the materials described in Table 6 as a hole injection layer, a hole transport layer, a light emitting layer host material, a light emitting layer dopant material, and a second electron transport layer, a light emitting device was fabricated and evaluated in the same manner as in Example 83. did. The results of each example are shown in Table 6.

(Example 88)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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, HAT-CN6 was deposited as a hole injection layer by 10 nm by a resistance heating method, and then HT-1 was deposited as a hole transport layer by 50 nm. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, E-1 is vapor-deposited as a first electron transport layer at a thickness of 5 nm, compound E-1 is used as an electron transport material as a second electron transport layer, cesium is used as a donor compound, and E-1 and cesium are deposited. The layers were laminated to a thickness of 15 nm so that the ratio was 20: 1.
Next, magnesium and silver were vapor-deposited 1000 nm so that mass ratio might be 1: 1, and it was set as the cathode, and the element of a 5 * 5-mm square was produced. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 4.0 V and an external quantum efficiency of 5.4%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time to decrease 20% from the initial luminance was 313 hours.

(Examples 89 to 92)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 88. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Example 93)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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, HT-1 was used as a hole injection material and F4-TCNQ was used as an acceptor compound and 30 nm was deposited by a resistance heating method so that the acceptor compound had a doping concentration of 10% by mass. Next, 30 nm of HT-1 was deposited as a hole transport layer. Next, as a light-emitting layer, Compound H-1 was used as the host material, Compound D-1 was used as the dopant material, and vapor deposition was performed to a thickness of 40 nm so that the dopant concentration was 5% by mass. Next, E-1 is vapor-deposited as a first electron transport layer at a thickness of 5 nm, compound E-1 is used as an electron transport material as a second electron transport layer, cesium is used as a donor compound, and E-1 and cesium are deposited. The layers were laminated to a thickness of 15 nm so that the ratio was 20: 1.
Next, magnesium and silver were vapor-deposited 1000 nm so that mass ratio might be 1: 1, and it was set as the cathode, and the element of a 5 * 5-mm square was produced. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The light-emitting element had characteristics of 1000 cd / m ^{2 and} emitted blue light with a driving voltage of 4.0 V and an external quantum efficiency of 5.5%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 301 hours.

(Examples 94 to 97)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 93. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Example 98)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. By resistance heating, molybdenum oxide (MoO ₃ ) was first deposited as a hole injection layer by 1 nm, and then HT-1 was deposited as a hole transport layer by 59 nm. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as the second electron transport layer, the compound E-1 is used as the electron transport material, Liq is used as the donor compound, and the deposition rate ratio of E-1 and Liq is 1: 1. Laminated.
Next, magnesium and silver were vapor-deposited 1000 nm so that mass ratio might be 1: 1, and it was set as the cathode, and the element of a 5 * 5-mm square was produced. The film thickness here is a display value of a crystal oscillation type film thickness monitor. This property of at 1000 cd / ^{m 2} of the light-emitting element drive voltage 4.2 V, and an external quantum efficiency of 5.4%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time to decrease 20% from the initial luminance was 294 hours.

(Examples 99 to 102)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, and second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 98. did. The results of each example are shown in Table 6.

(Example 103)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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. By resistance heating, molybdenum oxide (MoO ₃ ) was first deposited as a hole injection layer by 1 nm, and then HT-1 was deposited as a hole transport layer by 59 nm. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, E-1 is vapor-deposited as a first electron transport layer at a thickness of 5 nm, compound E-1 is used as an electron transport material as a second electron transport layer, cesium is used as a donor compound, and E-1 and cesium are deposited. The layers were laminated to a thickness of 15 nm so that the ratio was 20: 1.
Next, magnesium and silver were vapor-deposited 1000 nm so that mass ratio might be 1: 1, and it was set as the cathode, and the element of a 5 * 5-mm square was produced. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light emitting element at 1000 cd / m ² were a driving voltage of 4.0 V and an external quantum efficiency of 5.4%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time of 20% reduction from the initial luminance was 301 hours.

(Examples 104 to 107)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 103. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Examples 108 to 112)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 88. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Examples 113 to 117)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 93. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Examples 118 to 122)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 103. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Example 123)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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, HT-3 was used as a hole injection material and PD-1 was used as an acceptor compound by a resistance heating method, and 30 nm was deposited so that the acceptor compound had a doping concentration of 3 mass%. Next, HT-3 was deposited as a hole transport layer by 30 nm. Next, as a light emitting layer, the compound H-1 was used as the host material, the compound D-1 was used as the dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration was 5 mass%. Next, as the second electron transport layer, the compound E-1 is used as the electron transport material, Liq is used as the donor compound, and the deposition rate ratio of E-1 and Liq is 1: 1. Laminated.
Next, Liq was deposited as an electron injection layer to a thickness of 0.5 nm, and then magnesium and silver were deposited at a thickness of 1000 nm so as to have a mass ratio of 1: 1 to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The characteristics of this light-emitting element at 1000 cd / m ² were a driving voltage of 4.0 V and an external quantum efficiency of 5.3%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time required for a 20% decrease from the initial luminance was 364 hours.

(Examples 124 and 125)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 123. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Example 126)
A glass substrate (manufactured by Geomat Co., Ltd., 11Ω / □, sputtered product) on which ITO transparent conductive film was deposited at 165 nm was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with “Semico Clean 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. 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, as a hole injection layer, HT-3 was used as a hole injection material, PD-1 was used as an acceptor compound, and 30 nm was deposited by a resistance heating method so that the acceptor compound had a doping concentration of 3 mass%. Next, 30 nm of HT-3 was deposited as a hole transport layer. Next, as a light-emitting layer, Compound H-1 was used as the host material, Compound D-1 was used as the dopant material, and vapor deposition was performed to a thickness of 40 nm so that the dopant concentration was 5% by mass. Next, E-1 is vapor-deposited as a first electron transport layer at a thickness of 5 nm, compound E-1 is used as an electron transport material as a second electron transport layer, cesium is used as a donor compound, and E-1 and cesium are deposited. The layers were laminated to a thickness of 15 nm so that the ratio was 20: 1.
Next, magnesium and silver were vapor-deposited 1000 nm so that mass ratio might be 1: 1, and it was set as the cathode, and the element of a 5 * 5-mm square was produced. The film thickness here is a display value of a crystal oscillation type film thickness monitor. The light-emitting element had characteristics of 1000 cd / m ^{2 and} emitted blue light with a driving voltage of 3.9 V and an external quantum efficiency of 5.4%. When this element was set to an initial luminance of 1000 cd / m ² and the endurance life was measured, the time required for a 20% decrease from the initial luminance was 372 hours.

(Examples 127 and 128)
Using the materials described in Table 6 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 126. A device was fabricated and evaluated. The results of each example are shown in Table 6.

(Examples 129 to 138)
Using the materials described in Table 7 as a hole injection layer, a hole transport layer, a light emitting layer host material, a light emitting layer dopant material, and a second electron transport layer, a light emitting device was fabricated and evaluated in the same manner as in Example 78. did. The results of each example are shown in Table 7. HT-11, HT-12, E-3, and E-4 are the compounds shown below.

<Comparative Examples 48 to 84: a light emitting device having a donor compound in the electron transport layer and an acceptor compound in the hole injection layer, but not having the compound represented by the general formula (1) in the hole transport layer>
(Comparative Examples 48-50)
Using the materials described in Table 8 as the hole injection layer, the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, and the second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 78. did. The results of each comparative example are shown in Table 8.

(Comparative Examples 51-53)
Using the materials described in Table 8 as the hole injection layer, the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, and the second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 83. did. The results of each comparative example are shown in Table 8.

(Comparative Examples 54 to 56)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 88. A device was fabricated and evaluated. The results of each comparative example are shown in Table 8.

(Comparative Examples 57-59)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 93. A device was fabricated and evaluated. The results of each comparative example are shown in Table 8.

(Comparative Examples 60 to 62)
Using the materials described in Table 8 as the hole injection layer, the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, and the second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 98. did. The results of each comparative example are shown in Table 8.

(Comparative Examples 63 to 65)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 103. A device was fabricated and evaluated. The results of each comparative example are shown in Table 8.

(Comparative Examples 66-68)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 88. A device was fabricated and evaluated. The results of each comparative example are shown in Table 8.

(Comparative Examples 69-71)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 93. A device was fabricated and evaluated. The results of each comparative example are shown in Table 8.

(Comparative Examples 72-74)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 103. A device was fabricated and evaluated. The results of each comparative example are shown in Table 8.

(Comparative Examples 75-77)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 123. A device was fabricated and evaluated. The results of each example are shown in Table 8.

(Comparative Examples 78-80)
Using the materials described in Table 8 as the hole injection layer, hole transport layer, light emitting layer host material, light emitting layer dopant material, first electron transport layer, and second electron transport layer, light emission was performed in the same manner as in Example 126. A device was fabricated and evaluated. The results of each example are shown in Table 8.

(Comparative Examples 81-90)
Using the materials described in Table 8 as the hole injection layer, the hole transport layer, the light emitting layer host material, the light emitting layer dopant material, and the second electron transport layer, a light emitting device was produced and evaluated in the same manner as in Example 78. did. The results of each comparative example are shown in Table 8. HT-13, HT-14, and HT-15 are the compounds shown below.

From Tables 6, 7 and 8, Examples 78 to 82 and Comparative Examples 48 to 50, Examples 83 to 87, Comparative Examples 51 to 53, Examples 88 to 92, Comparative Examples 54 to 56, and Examples 93 to 97 Comparative Examples 57-59, Examples 98-102 and Comparative Examples 60-62, Examples 103-107 and Comparative Examples 63-65, Examples 108-112, Comparative Examples 66-68, Examples 113-117 and Comparative Examples 69-71, Examples 118-122 and Comparative Examples 72-74, Examples 123-125 and Comparative Examples 75-77, Examples 126-128, Comparative Examples 78-80, Examples 129-133 and Comparative Examples 81- 85. By comparing Examples 134 to 138 with Comparative Examples 86 to 90, the hole injection layer is composed of an acceptor compound alone or contains an acceptor compound, and the electron transport layer contains a donor compound. Contain Case, by using a compound represented by the general formula (1) in the hole transporting layer, a low voltage drive, improvement in luminous efficiency, it can be seen that the effect is seen such a considerable improvement in durability.

The light-emitting element according to the present invention is useful in fields that are driven at a low voltage and require high luminous efficiency and durability, and is a display element, flat panel display, backlight, illumination, interior, sign, signboard, and electrophotography. It can be used for a machine and an optical signal generator.

Claims

A light emitting device comprising at least a hole transport layer and an electron transport layer between an anode and a cathode, and emitting light by electric energy,
The hole transport layer contains a compound represented by the following general formula (1),
The electron transport layer includes an alkali metal, an inorganic salt containing an alkali metal, a complex of an alkali metal and an organic substance, an alkaline earth metal, an inorganic salt containing an alkaline earth metal, and a complex of an alkaline earth metal and an organic substance. A light emitting device comprising a donor compound selected from the group consisting of:

(In the general formula (1), R 1 to R 12 may be the same or different from each other, and hydrogen, alkyl group, cycloalkyl group, amino group, aryl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl thioether group, a halogen, a cyano group, -P (= O) .R selected from the group consisting of R 13 R 14 and a silyl group 13 and R 14 are each These substituents may be the same or different and are an aryl group or a heteroaryl group, and these substituents may be further substituted, and adjacent substituents may further form a ring, provided that R N of 1 to R 12 is an amino group represented by —NR 15 R 16. R 15 and R 16 may be the same or different. And may be selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group, where n represents an integer of 1 to 6.)
A light emitting device comprising at least a hole transport layer and a hole injection layer between an anode and a cathode, and emitting light by electric energy,
The hole transport layer contains a compound represented by the following general formula (1),
The light-emitting element, wherein the hole injection layer is composed of an acceptor compound alone or contains an acceptor compound.

(In the general formula (1), R 1 to R 12 may be the same or different from each other, and hydrogen, alkyl group, cycloalkyl group, amino group, aryl group, heterocyclic group, alkenyl group, cycloalkenyl group, An alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, a halogen, a cyano group, —P (═O) R 13 R 14 and a silyl group, each selected from R 13 and R 14 These substituents may be the same or different and are an aryl group or a heteroaryl group, and these substituents may be further substituted, and adjacent substituents may further form a ring, provided that R 1 n pieces of ~ R 12 are .R 15 and R 16 is an amino group represented by -NR 15 R 16 are the same or different And may be selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group, where n represents an integer of 1 to 6.)
The light-emitting element according to claim 2, wherein the acceptor compound is composed of a compound that is a metal oxide or a cyano group-containing compound alone or contains an acceptor compound.
There is a further electron transport layer between the anode and the cathode,
The electron transport layer includes an alkali metal, an inorganic salt containing an alkali metal, a complex of an alkali metal and an organic substance, an alkaline earth metal, an inorganic salt containing an alkaline earth metal, and a complex of an alkaline earth metal and an organic substance. The light emitting device according to claim 2, comprising a donor compound selected from the group consisting of:
The electron transport layer is composed of one or more elements selected from the group consisting of carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus, and includes a compound having a heteroaryl ring structure containing electron-accepting nitrogen. The light emitting device according to claim 1 or 4.