KR20140141573A - Light emitting element - Google Patents

Abstract

A light emitting device that achieves both high light emitting efficiency and durability is provided.
The light emitting device of the present invention is a light emitting device having at least a hole transporting layer and a light emitting layer between an anode and a cathode and emitting light by electric energy, the hole transporting layer including a compound having a specific carbazole skeleton, And a compound having an aromatic heterocyclic group containing water-soluble nitrogen.

Description

[0001] LIGHT EMITTING ELEMENT [0002]

The present invention relates to a light emitting device capable of converting electrical energy into light. More particularly, the present invention relates to a light emitting device usable in fields such as a display device, a flat panel display, a backlight, a lighting, an interior, a sign, a signboard, an electronic camera and an optical signal generator.

Research has been actively conducted on organic thin film light emitting devices in which electrons injected from a cathode and holes injected from an anode recombine in an organic fluorescent material sandwiched between positive electrodes. This light emitting device is characterized by ultra-thin, high-luminance light emission under a low driving voltage, and multicolor light emission by selecting a fluorescent material, and has attracted attention.

This study shows that organic thin film devices emit light at a high luminance by CW Tang of KODAK Co., Ltd. Many studies have been made for practical use, and organic thin film light emitting devices are being used in a main display of a cellular phone or the like steadily and practically . However, there are still many technical problems, among which the high efficiency of the device and the compatibility with the long life span are among the major problems.

The drive voltage of the device largely depends on a carrier transporting material that transports carriers such as holes and electrons to the light emitting layer. Among them, a material having a carbazole skeleton as a material for transporting holes (hole transporting material) is known (see, for example, Patent Documents 1 and 2).

Further, the material having a carbazole skeleton has a high triplet level and is therefore known as a host material for a light emitting layer (see, for example, Patent Document 3). Also disclosed is an organic electroluminescent device containing an indolocarbazole derivative as a host material together with a phosphorescent dopant (see, for example, Patent Document 4).

Japanese Patent Laid-Open No. 8-3547 Korean Patent Application Publication No. 2010-0079458 Japanese Patent Application Laid-Open No. 2003-133075 International Publication No. 2008/056746

However, in the conventional technique, it is difficult to sufficiently lower the driving voltage of the device. Further, even if the driving voltage of the device can be lowered, the luminous efficiency and the service life of the device are insufficient. Thus, no technology has been found that can achieve both a high luminous efficiency and a long life span.

It is an object of the present invention to provide an organic thin film light emitting device which solves the problems of the prior art and improves the luminous efficiency and the durability life.

In order to solve the above-described problems, a light emitting device of the present invention is a light emitting device having at least a hole transporting layer and a light emitting layer between an anode and a cathode and emitting light by electric energy, and the hole transporting layer is represented by the following general formula 1), and the light-emitting layer is a compound having an aromatic heterocyclic group containing electron-accepting nitrogen and contains a compound represented by one of the following general formulas (2) to (4) .

In the general formula (1), R ¹ to R ⁴ may be the same or different, and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, An aryl group, a heteroaryl group, a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl group, a carbamoyl group, an amino group, a silyl group, -P (= O) R ⁵ R ⁶ . R ⁵ and R ⁶ are an aryl group or a heteroaryl group. L is a single bond or a divalent linking group.]

[In the formulas (2) to (4), R ⁷ to R ¹¹ and R ²¹ to R ²⁷ may be the same or different, and may be hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, An alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group, a heteroaryl group, a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl group, a carbamoyl group, an amino group, or a silyl group. Ring A or Ring B represents a benzene ring having a substituent or having no substituent, condensed at an arbitrary position with an adjacent ring. Y ¹ to Y ³ are -N (R ²⁸ ) -, -C (R ²⁹ R ³⁰ ) -, an oxygen atom, or a sulfur atom. R ²⁸ to R ³⁰ may be the same or different, and each is an alkyl group, an aryl group, or a heteroaryl group. R ²¹ to R ³⁰ may form a ring among adjacent substituents. L ¹¹ to L ¹⁷ are a single bond or an arylene group. X ¹ to X ⁵ represent a carbon atom or a nitrogen atom, and when X ¹ to X ⁵ are nitrogen atoms, R ⁷ to R ^{11 which} are substituents on the nitrogen atom are not present. Provided that the number of nitrogen atoms in X ¹ to X ⁵ is 1 or 2.]

(Effects of the Invention)

According to the present invention, it is possible to provide an organic electroluminescent device having a high luminous efficiency and a sufficient durability life.

The present invention provides a light-emitting element comprising at least a hole-transporting layer and a light-emitting layer between an anode and a cathode and emitting light by electric energy, wherein the hole-transporting layer contains a compound represented by the following general formula (1) And a compound having an aromatic heterocyclic group containing water-soluble nitrogen.

Since the compound having an aromatic heterocyclic group containing an electron-accepting nitrogen used in the present invention has a high electron injection transporting ability, it can provide an organic thin film light emitting device having high light emission efficiency and low driving voltage by being used as a light emitting layer. However, since this light emitting layer has a very high electron injection transporting ability, depending on the kind of the hole transporting layer used, the recombination region in the light emitting layer is shifted toward the hole transporting layer side, and triplet energy and electrons leak into the hole transporting layer. The light emitting efficiency of the device may deteriorate and the durability may deteriorate.

On the other hand, the present inventors have found that the use of the compound represented by the general formula (1) as a hole transport layer enables a significant improvement in luminescence efficiency and durability. That is, the compound represented by the general formula (1) has a high electron blocking property and a high triplet energy, so that even when the recombination region in the light emitting layer is shifted to the side of the hole transporting layer, triplet energy and electrons can be confined in the light emitting layer, And long-term service life.

That is, the use of the compound represented by the general formula (1) in the hole transporting layer and the use of the compound having an aromatic heterocyclic group containing electron-accepting nitrogen in the light emitting layer is a preferable combination for achieving high luminescence efficiency and durability.

The compound represented by the general formula (1) in the present invention will be described in detail.

In the general formula (1), R ¹ to R ⁴ may be the same or different, and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, An aryl group, a heteroaryl group, a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl group, a carbamoyl group, an amino group, a silyl group, and -P (= O) R ⁵ R ⁶ . R ⁵ and R ⁶ are an aryl group or a heteroaryl group. L is a single bond or a divalent linking group.

Among these substituents, hydrogen may be deuterium.

In the compound represented by the general formula (1), the alkyl group means a saturated aliphatic hydrocarbon group such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec- , Which may or may not have a substituent. The substituent when it is substituted is not particularly limited and includes, for example, an alkyl group, an aryl group, and a heteroaryl group, and this point is common to 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, more preferably 1 to 8 in terms of availability and cost.

In the compound represented by the general formula (1), the cycloalkyl group means, for example, a saturated alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl, norbornyl, adamantyl and the like, which may or may not have a substituent. The number of carbon atoms in the alkyl group moiety is not particularly limited, but is usually in the range of 3 or more and 20 or less.

In the compound represented by the general formula (1), the heterocyclic group means an aliphatic ring having an atom other than carbon such as a pyran ring, piperidine ring and cyclic amide in the ring, which may or may not have a substituent You do not have to. The number of carbon atoms of the heterocyclic group is not particularly limited, but is usually in the range of 2 or more and 20 or less.

In the compound represented by the general formula (1), the alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond such as a vinyl group, an allyl group, and 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 usually ranges from 2 to 20 inclusive.

In the compound represented by the general formula (1), the cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond such as a cyclopentenyl group, a cyclopentadienyl group, a cyclohexenyl group and the like, It may or may not be present. The number of carbon atoms of the cycloalkenyl group is not particularly limited, but usually ranges from 2 to 20.

In the compound represented by the general formula (1), the alkynyl group refers to an unsaturated aliphatic hydrocarbon group including a triple bond such as an ethynyl group, which may or may not have a substituent. The carbon number of the alkynyl group is not particularly limited, but is usually in a range of 2 or more and 20 or less.

In the compound represented by the general formula (1), the alkoxy group represents a functional group in which an aliphatic hydrocarbon group is bonded through an ether bond such as a methoxy group, an ethoxy group or a propoxy group, and the aliphatic hydrocarbon group may or may not have a substituent You do not have to. The number of carbon atoms of the alkoxy group is not particularly limited, but is usually in the range of 1 to 20, inclusive.

In the compound represented by the general formula (1), the alkylthio group is one in which the oxygen atom of the ether bond of the alkoxy group is substituted with a sulfur atom. The hydrocarbon group of the alkylthio group may or may not have a substituent. The carbon number of the alkylthio group is not particularly limited, but is usually in the range of 1 to 20, inclusive.

In the compound represented by the general formula (1), the aryl ether group represents a functional group having an aromatic hydrocarbon group bonded through an ether bond such as a phenoxy group, and the aromatic hydrocarbon group may or may not have a substituent. The number of carbon atoms of the aryl ether group is not particularly limited, but is usually in the range of 6 or more and 40 or less.

In the compound represented by the general formula (1), the aryl thioether group is an oxygen atom of an ether bond of an aryl ether group substituted by a sulfur atom. The aromatic hydrocarbon group in the aryl ether group may or may not have a substituent. The number of carbon atoms of the aryl ether group is not particularly limited, but is usually in the range of 6 or more and 40 or less.

In the compound represented by the general formula (1), the aryl group may be an aromatic group such as a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, a phenanthryl group, an anthracenyl group, a triphenylenyl group, a terphenyl group, Represents a hydrocarbon group. The aryl group may or may not have a substituent. The number of carbon atoms of the aryl group is not particularly limited, but is usually in the range of 6 or more and 40 or less.

In the compound represented by the general formula (1), the heteroaryl group includes a phenyl group, a thiophenyl group, a pyridyl group, a pyrimidyl group, a triazyl group, a quinolinyl group, a pyrazinyl group, a naphthyridyl group, a benzofuranyl group, , Indolyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group and the like, which may be unsubstituted or substituted, in one or more rings. The number of carbon atoms of the heteroaryl group is not particularly limited, but usually ranges from 2 to 30.

In the compound represented by the general formula (1), halogen means fluorine, chlorine, bromine, or iodine.

In the compound represented by the general formula (1), the carbonyl group, the carboxyl group, the oxycarbonyl group and the carbamoyl group may or may not have a substituent. Examples of the substituent include an alkyl group, a cycloalkyl group and an aryl group , These substituents may be further substituted.

In the compound represented by the general formula (1), the amino group may or may not have a substituent, and examples of the substituent include an aryl group and a heteroaryl group, and these substituents may be further substituted.

The silyl group in the compound represented by the general formula (1) represents a functional group having a bond to a silicon atom such as a trimethylsilyl group, which may or may not have a substituent. The number of carbon atoms in the silyl group is not particularly limited, but is usually in the range of 3 or more and 20 or less. The number of silicon atoms is usually in the range of 1 to 6, inclusive.

In the compound represented by the general formula (1), L is a single bond or a divalent linking group, and examples of the divalent linking group include a phenylene group, a naphthylene group, a biphenylene group, a fluorenylene group, A thiophenylene group, a pyridylene group, a quinolinylene group, an isoquinolinylene group, a pyrazinylene group, a pyrimidylene group, a naphthyridylene group, a naphthylidene group, And heteroarylene groups such as benzofuranyl group, benzothiophenylene group, indolylene group, dibenzofuranyl group, dibenzothiophenylene group and carbazolidylene group. These may or may not have substituents.

Further, the light-emitting element of the present invention is characterized in that the light-emitting layer is a compound having an aromatic heterocyclic group containing electron-accepting nitrogen and contains a compound represented by any one of the following general formulas (2) to (4) When the compound represented by any one of the following general formulas (2) to (4), which is a compound having an aromatic heterocyclic group containing electron-accepting nitrogen, is contained in the light-emitting layer, the light emitting efficiency is improved because it exhibits high electron injection transportability. Further, since a stable thin film can be formed, durability is improved, which is preferable.

The compound having an aromatic heterocyclic group containing electron-accepting nitrogen in the present invention will be described in detail.

Herein, the electron-accepting nitrogen means a nitrogen atom forming a multiple bond with adjacent atoms. Since the nitrogen source has a high electron affinity, the multiple bonds have electron accepting properties. Therefore, aromatic heterocyclic rings containing electron-accepting nitrogen have high electron affinity. Since the compound of the present invention having electron-accepting nitrogen exhibits high electron injection transportability, the recombination probability is increased, and thus the luminous efficiency is improved.

The aromatic heterocyclic group containing electron-accepting nitrogen is preferably a pyridyl group, a quinolinyl group, an isoquinolinyl group, a quinoxanyl group, a pyrazinyl group, a pyrimidyl group, a pyridazinyl group, a phenanthrolinyl group, At least an electron-accepting nitrogen atom as an atom other than carbon in the above-mentioned heteroaryl group, such as a benzoimidazolyl group, a benzoimidazolyl group, a benzooxazolyl group, a benzothiazolyl group, a bipyridyl group or a terpyridyl group, And R < 2 > In the compound having an aromatic heterocyclic group containing electron-accepting nitrogen used in the present invention, the number of electron-accepting nitrogen included in the aromatic heterocycle of 1 is 1 or 2. However, when the compound having an aromatic heterocyclic group containing electron-accepting nitrogen has a plurality of aromatic heterocyclic rings containing electron-accepting nitrogen, it may have three or more electron-accepting nitrogen. The aromatic heterocyclic group containing electron-accepting nitrogen may have an alkyl group or a cycloalkyl group as a substituent.

In general, when depositing an organic material, it is preferable that a difference between a decomposition temperature and a sublimation temperature is large in order to perform deposition at a high temperature for a long time. When the number of the electron-accepting nitrogen included in the aromatic heterocycle of 1 in the compound having an aromatic heterocyclic group containing electron-accepting nitrogen is 3 or more, if it is required to deposit at a high temperature, the heat load applied to the compound itself becomes large, May be pyrolyzed and deposited. The incorporation of such degradation products may significantly affect the device characteristics, particularly the lifetime. In order to prevent such concern, the number of electron-accepting nitrogen included in the aromatic heterocycle of 1 is preferably 2 or less.

The monoazinic compound or diazin compound having the number of electron-accepting nitrogen atoms contained in the aromatic heterocyclic ring of the compound having an aromatic heterocyclic group containing an electron-accepting nitrogen is 2 or less, the reception of electrons from the electron-transporting layer becomes easy, The electron injecting property is increased, so that the recombination probability is increased and the luminescence efficiency is improved.

When a compound having an aromatic heterocyclic group containing an electron-accepting nitrogen is represented by the following general formulas (2) to (4), the compound exhibits high electron injection transportability, and thus the luminous efficiency is improved. Further, since a stable thin film can be formed, durability is improved, which is preferable.

In the general formulas (2) to (4), R ⁷ to R ¹¹ and R ²¹ to R ²⁷ may be the same or different and each represents a single bond, a hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, An aryl group, an aryl group, a heteroaryl group, a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl group, a carbamoyl group, an amino group, or a silyl group. R ⁷ to R ¹¹ may form a ring with adjacent substituents. Ring A or Ring B represents a benzene ring having a substituent or having no substituent, condensed at an arbitrary position with an adjacent ring. Y ¹ to Y ³ are -N (R ²⁸ ) -, -C (R ²⁹ R ³⁰ ) -, an oxygen atom, or a sulfur atom. R ²⁸ to R ³⁰ may be the same or different, and each is an alkyl group, an aryl group, or a heteroaryl group. R ²¹ to R ³⁰ may form a ring among adjacent substituents. L ¹¹ to L ¹⁷ are a single bond or an arylene group. X ¹ to X ⁵ represent a carbon atom or a nitrogen atom, and when X ¹ to X ⁵ are nitrogen atoms, R ⁷ to R ^{11 which} are substituents on the nitrogen atom are not present. Provided that the number of nitrogen atoms in X ¹ to X ⁵ is 1 or 2.

In the general formulas (2) to (4), the arylene group represented by L ¹¹ to L ¹⁷ is a bivalent group formed by removing one hydrogen atom from two ring carbon atoms of an aromatic compound (arene) Examples include a phenylene group, a naphthylene group, a biphenylene group, a fluorenylene group, a phenanthrylene group, a terphenylene group, an anthracenylene group, and a pyrenylene group. These may or may not have substituents.

The description of the other substituents is the same as the compound represented by the general formula (1).

In the general formulas (2) to (4), the number of nitrogen atoms in X ¹ to X ⁵ is 1 or 2, and the adjacent two of X ¹ to X ⁵ are not simultaneously a nitrogen atom. Since two adjacent X ¹ to X ⁵ do not become nitrogen atoms at the same time, thermally weak nitrogen-nitrogen double bond is eliminated, and the thermal stability of the whole molecule is improved. Further, X ¹ to X ⁵ The number of nitrogen atoms in the electron-transporting layer is 1 or 2, which facilitates the reception of electrons from the electron-transporting layer and increases the electron-injecting property into the light-emitting layer.

Among them, X ¹ and X ⁵ , X ³ and X ⁵ , or X ¹ and X ³ are more preferably nitrogen atoms in terms of both thermal stability and electron injecting and transporting characteristics.

It is preferable that at least two of R ⁷ to R ¹¹ are aryl groups. At least two of R ⁷ to R ¹¹ are aryl groups, the planarity of a ring structure composed of X ¹ to X ⁵ and a carbon atom can be suppressed from being easily stacked to form a stable thin film, and energy can be efficiently supplied to the dopant So that high-efficiency light emission is possible.

Among them, from the viewpoint of ease of synthesis, at least two of R ⁷ to R ¹¹ are a phenyl group having no substituent, a phenyl group having an alkyl group as a substituent, a phenyl group having a halogen as a substituent, or a phenyl group having a phenyl group as a substituent, It is preferable.

Since the indolocarbazole skeleton has a high triplet level, compounds having an indolocarbazole skeleton represented by the general formulas (2) to (4) can maintain a high triplet level, High emission efficiency can be achieved because deactivation can be suppressed.

Among them, a compound wherein L ¹¹ to L ¹⁷ are a single bond and R ²¹ to R ²⁶ are hydrogen is preferable from the viewpoint of ease of synthesis.

Further, R < ²⁷ > is preferably an aryl group from the ease of synthesis. Among them, R ²⁷ is preferably a phenyl group because a stable thin film can be formed.

As a compound having an aromatic heterocyclic group containing an electron-accepting nitrogen, there can be mentioned, for example, International Publication No. 2011/148909 pamphlet, International Publication No. 2011/132683 pamphlet, International Publication No. 2011/132684 pamphlet, International Publication No. 2008/056746 pamphlet, International A pamphlet of the publication No. 2009/084546, a pamphlet of the International Publication No. 2010/136109, a pamphlet of the International Publication No. 2011/019156, a pamphlet of the International Publication No. 2011/139055, a pamphlet of the International Publication No. 2011/055934, A pamphlet, a pamphlet of International Publication No. 2011/136755, a pamphlet of International Publication No. 2011/136520, a pamphlet of International Publication No. 2011/132865, and a pamphlet of International Publication No. 2012/023947, The following compounds may be mentioned.

From the viewpoint of easiness of synthesis and hole transportability, the compound represented by the general formula (1) is preferably carbazole-linked as shown by the following general formula (5).

From the viewpoint of improving the durability of the light emitting element, it is preferable that the dimer is an asymmetric carbazole dimer. In the symmetrical structure, the crystallinity is high and the stability of the thin film is insufficient, so that the durability of the device is lowered.

From the viewpoint of heat resistance, R ¹ , R ² is more preferably an aryl group having a substituent or having no substituent.

As a compound represented by the general formula (1), there can be mentioned compounds disclosed in International Publication No. 2011/122132, International Publication No. 2011/125680, International Publication No. 2011/48821, International Publication No. 2011/48822, International Publication No. 2011/24451 , International Publication No. 2012/1986, and Korean Patent Publication No. 2010-79458, and specific examples thereof include the following compounds.

The compound represented by the general formula (1) can be produced by a known method. Namely, the Suzuki coupling reaction of carbobenzene-substituted carbazole and carbazole-substituted monoboronic acid at 9-position can be easily synthesized, but the production method is not limited thereto.

Next, embodiments of the light emitting device of the present invention will be described in detail. The light emitting device of the present invention has a positive electrode and a negative electrode, and a hole transporting layer and a light emitting layer interposed between the positive electrode and the negative electrode, and the light emitting layer emits light by electric energy.

The layer structure between the anode and the cathode in such a light emitting element is not limited to the structure comprising the hole transporting layer and the light emitting layer,

1) hole transporting layer / light emitting layer / electron transporting layer

2) Hole injection layer / hole transporting layer / light emitting layer / electron transporting layer

3) hole transporting layer / light emitting layer / electron transporting layer / electron injecting layer

4) Hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer

And the like. Each of the layers may be either a single layer or a plurality of layers and may be doped.

In the light emitting device of the present invention, the anode and the cathode have a role of supplying a sufficient current for light emission of the element, and at least one of them is preferably transparent or semitransparent in order to extract light. Normally, a positive electrode formed on a substrate is a transparent electrode.

In the light emitting device of the present invention, the material used for the anode is preferably a material that can efficiently inject holes into the organic layer, and a transparent or translucent material such as zinc oxide, tin oxide, indium oxide, indium tin oxide ) And zinc oxide indium (IZO), metals such as gold, silver and chromium, inorganic conductive substances such as copper iodide and copper sulfide, and conductive polymers such as polythiophene, polypyrrole and polyaniline However, it is particularly preferable to use ITO glass or nese glass. These electrode materials may be used alone, but a plurality of materials may be laminated or mixed. The resistance of the transparent electrode is not limited as long as it can supply a sufficient current for light emission of the element, but it is preferable that the resistance is low in view of power consumption of the element. For example, an ITO substrate of 300 OMEGA / & squ & or less functions as an element electrode. However, since it is now possible to supply a substrate of about 10 OMEGA / & squ & Thickness of ITO can be arbitrarily selected in accordance with the resistance value, but it is often used between 50 and 300 nm.

In order to maintain the mechanical strength of the light emitting element, it is preferable to form the light emitting element on the substrate. As the substrate, a glass substrate such as soda glass or non-alkali glass is suitably used. The thickness of the glass substrate should be sufficient to maintain the mechanical strength, so it is sufficient that the glass substrate has a thickness of 0.5 mm or more. With respect to the material of the glass, it is preferable that the amount of elution ions from the glass is small, and therefore, it is preferable that the glass is an alkali-free glass. Alternatively, soda lime glass on which a barrier coating such as SiO ₂ is applied is also commercially available, so that it may be used. Further, if the first electrode functions stably, the substrate need not be glass, and for example, a positive electrode may be formed on a plastic substrate. The ITO film formation method is not particularly limited, such as an electron beam method, a sputtering method, and a chemical reaction method.

In the light emitting device of the present invention, the material used for the cathode is not particularly limited as long as it can efficiently inject electrons into the light emitting layer. In general, metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium, or alloys or multi-layered layers of these metals with low-function metals such as lithium, sodium, potassium, calcium and magnesium are preferable. Among them, aluminum, silver, and magnesium are preferred as the main components in terms of electric resistance and ease of film formation, film stability, luminescence efficiency, and the like. Particularly, when composed of magnesium and silver, electron injection into the electron transporting layer and the electron injecting layer in the present invention is facilitated and low voltage driving becomes possible, which is preferable.

In order to protect the negative electrode, 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, As a protective film layer, an organic polymer compound such as a polyimide-based polymer compound is laminated on a negative electrode. However, in the case of a device structure (top emission structure) in which light is extracted from the cathode side, the protective film layer is selected from a material having light transmittance in the visible light region. Methods for manufacturing these electrodes are not particularly limited, such as resistance heating, electron beam beam, sputtering, ion plating and coating.

In the light emitting device of the present invention, the hole injecting layer is a layer inserted between the anode and the hole transporting layer. The hole injection layer may be a single layer or a plurality of layers may be laminated. If a hole injection layer is present between the hole transport layer and the anode, it is preferable to drive at a lower voltage and to improve durability life as well as to improve the carrier balance of the device and improve the light emitting efficiency.

The material used for the hole injection layer is not particularly limited, and examples thereof include 4,4'-bis (N- (3-methylphenyl) -N-phenylamino) biphenyl (TPD), 4,4'- Bis (N, N-bis (4-biphenylyl) amino) biphenyl (TBDB), bis (N, N'- Benzidine derivatives such as N, N'-diphenyl-4-aminophenyl) -N, N-diphenyl-4,4'- diamino-1,1'- biphenyl (TPD232) -Tris (3-methylphenyl (phenyl) amino) triphenylamine (m-MTDATA), 4,4 ', 4 "-tris (1-naphthyl A material group called starburst arylamine, a biscarbazole derivative such as bis (N-arylcarbazole) or bis (N-alkylcarbazole), a pyrazoline derivative, a stilbene compound, a hydrazone compound, a benzofuran derivative, Heterocyclic compounds such as thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives and porphyrin derivatives, A polythiophene, a polyaniline, a polyfluorene, a polyvinylcarbazole, a polysilane, or the like is used. The compounds represented by the general formula (1) or (5) can also be used for the hole injection layer. Of these, those having a shallow HOMO level are preferable from the viewpoint of smoothly injecting and transporting holes from the anode to the hole transport layer Is used.

These materials may be used alone, or two or more kinds of materials may be mixed and used. A plurality of materials may be laminated to form a hole injection layer. Further, it is more preferable that the hole injection layer is composed solely of the acceptor material or the above-described effect is more remarkably obtained when the hole injection material is doped with the acceptor material. The acceptor material is a material for forming a hole transporting layer which is in contact with the hole transporting layer when used as a single layer film and a material and a charge transporting complex which form the hole injecting layer when doped. 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 effects such as improvement in luminous efficiency and lifetime durability can be obtained.

Examples of acceptor materials 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, tris Phenyl) aminium hexachloroantimonate (TBPAH). An organic compound having a nitro group, a cyano group, a halogen or a trifluoromethyl group in the molecule, a quinone-based compound, an acid anhydride-based compound, fullerene and the like are also suitably used. Specific examples of these compounds include hexacyano-butadiene, hexacyanobenzene, tetracyanoethylene, tetracyanoquinodimethane (TCNQ), tetrafluorotetracyanoquinodimethane (F4-TCNQ), radialene derivatives, p Fluororanyl, p-bromenyl, p-benzoquinone, 2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone, tetramethylbenzoquinone, 1,2,4,5- Tetracyano benzene, o-dicyanobenzene, p-dicyanobenzene, 1,4-dicyanotetrafluorobenzene, 2,3-dichloro-5,6-dicyanobenzoquinone, p-dinitrobenzene, m -Dinitrobenzene, o-dinitrobenzene, p-cyanonitrobenzene, m-cyanonitrobenzene, o-cyanonitrobenzene, 1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 1 -Nitronaphthalene, 2-nitronaphthalene, 1,3-dinitronaphthalene, 1,5-dinitronaphthalene, 9-cyananoanthracene, 9-nitroanthracene, 9,10-anthraquinone, 1,3,6,8 - Tetrany Rocca Carbazole, 2,4,7- trinitro-9-fluorenone, 2,3,5,6-dicyano pyridine, maleic anhydride, phthalic anhydride, and the like C60, and C70.

Among them, the metal oxide and the cyano group-containing compound are preferable because they can easily be handled and evaporated easily, and the above-mentioned effects can be easily obtained. In the case where the hole injecting layer is composed solely of the acceptor material or when the acceptor material is doped in the hole injecting layer, the hole injecting layer may be a single layer or a plurality of layers may be laminated do.

Although the acceptor material is not particularly limited, it is preferably used in an amount of 0.1 to 50 parts by mass, more preferably 0.5 to 20 parts by mass, based on the compound represented by the general formula (1) or (5) .

In the light emitting device of the present invention, the hole transporting layer is a layer for transporting holes injected from the anode to the light emitting layer. The compound represented by the general formula (1) or (5) has a high triplet level, high hole transporting property and thin film stability, and thus is suitably used for the hole transporting layer of the light emitting device. The hole transporting layer may be a single layer or may be formed by stacking a plurality of layers.

In the case of constituting a plurality of hole transporting layers, it is preferable that the hole transporting layer containing the compound represented by the general formula (1) or (5) is in direct contact with the light emitting layer. The compound represented by the general formula (1) or the general formula (5) has a high electron blocking property and can prevent the intrusion of electrons emitted from the light emitting layer. Further, the compound represented by the general formula (1) or (5) has a high triplet level and thus has an effect of blocking the excitation energy of the triplet light emitting material. Therefore, when a triplet light emitting material is contained in the light emitting layer, it is preferable that the hole transporting layer containing the compound represented by the general formula (1) or (5) is in direct contact with the light emitting layer.

The hole transporting layer may be composed of only the compound represented by the general formula (1) or the general formula (5), and other materials may be mixed within the range not to impair the effect of the present invention. In this case, the same material group as the material used for the hole injection layer may be mentioned as a preferable example. However, when used for the hole transport layer, the material of the HOMO level equal to or deeper than the material used for the hole injection layer It is more preferable to select it. Examples of other materials used in this case include 4,4'-bis (N- (3-methylphenyl) -N-phenylamino) biphenyl (TPD), 4,4'- (N, N'-diphenyl) -N-phenylamino) biphenyl (NPD), 4,4'- (4-aminophenyl) -N, N-diphenyl-4,4'-diamino-1,1'-biphenyl (TPD232) Starburst arylamine such as methylphenyl (phenyl) amino) triphenylamine (m-MTDATA), 4,4 ', 4 "-tris (1-naphthyl (phenyl) amino) triphenylamine , A biscarbazole derivative such as bis (N-arylcarbazole) or bis (N-alkylcarbazole), a pyrazoline derivative, a stilbene compound, a hydrazone compound, a benzofuran derivative, a thiophene derivative, A heterocyclic compound such as a pyridine derivative, a diazole derivative, a phthalocyanine derivative, or a porphyrin derivative; There may be mentioned a polycarbonate, a styrene derivative, a polythiophene, a polyaniline, a polyfluorene, a polyvinylcarbazole and a polysilane.

In the light emitting device of the present invention, the light emitting layer may be a single layer or a plurality of layers. When the light emitting layer is a plurality of layers, each light emitting layer is formed by a light emitting material (host material, dopant material), and each light emitting layer may be a mixture of a host material and a dopant material, Or a mixture of the dopant materials of the above-mentioned materials. That is, in the light emitting device of the present invention, only the host material or the dopant material may emit light in each light emitting layer, or the host material and the dopant material may emit light together. From the viewpoint of efficiently utilizing electric energy to obtain light of high color purity, it is preferable that the light emitting layer is made of a mixture of a host material and a dopant material. Each of the host material and the dopant material may be one type or a combination of a plurality of types. The dopant material may be included in the entire host material or may be partly contained in the host material. The dopant material may be laminated or dispersed, and any of them may be used. The dopant material can control the luminescent color. If the amount of the dopant material is excessively large, the concentration quenching phenomenon occurs. Therefore, the amount of the dopant material is preferably 30% by mass or less, more preferably 20% by mass or less, with respect to the host material. The doping method may be formed by a co-evaporation method with a host material, but may be vapor-deposited at the same time after being mixed with the host material in advance.

A compound having an aromatic heterocyclic group containing an electron-accepting nitrogen has high electron transporting property and thin film stability, and thus is suitably used for a light emitting layer of a light emitting device. Further, since the compound having an aromatic heterocyclic group containing an electron-accepting nitrogen has high electron transporting property and thin film stability, it is preferably used in a host material.

Further, since a compound having an aromatic heterocyclic group containing an electron-accepting nitrogen often has a high triplet level, it is preferable to use it as a host material for a device using a triplet light emitting material. Particularly suitable as the compound having an aromatic heterocyclic group containing an electron-accepting nitrogen is a compound represented by the general formula (2) to the general formula (4).

In the light emitting device of the present invention, in addition to the compound having an aromatic heterocyclic group containing electron-accepting nitrogen, the luminescent material may be a condensed ring derivative such as anthracene or pyrene, which has been known as a light emitting body, tris (8-quinolinolato) aluminum Metal chelated oxinoid compounds such as bis-styryl anthracene derivatives and distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, and perinone derivatives , A cyclopentadiene derivative, an oxadiazole derivative, a thiadiazolopyridine derivative, a dibenzofuran derivative, a carbazole derivative, an indolocarbazole derivative, a polymer type polyphenylene vinylene derivative, a polyparaphenylene derivative, and a poly Thiophene derivatives and the like can be used, but it is not particularly limited .

The host material contained in the light emitting material is not limited to only one type of compound and may be a mixture of a plurality of compounds represented by formulas (2) to (4) ) And other host materials may be mixed and used. In addition, a compound represented by the general formula (2) to the general formula (4) may be laminated or a compound represented by the general formula (2) to the general formula (4) may be laminated with other host material. Other host materials include, but are not limited to, compounds having condensed aryl rings such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, , Aromatic amine derivatives such as N, N'-dinaphthyl-N, N'-diphenyl-4,4'-diphenyl-1,1'-diamine, tris (8- quinolinate) aluminum A metal chelated oxinoid compound such as a metal chelated oxinoid compound such as a bisphenol compound, a bisstyryl derivative such as a distyrylbenzene derivative, a tetraphenylbutadiene derivative, an indene derivative, a coumarin derivative, an oxadiazole derivative, a pyrrolopyridine derivative, a perinone derivative, a cyclopentadiene derivative, Indazole derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, polyphenylenevinylene derivatives, polyparaphenylene derivatives, A polyfluorene derivative, a polyvinylcarbazole derivative, a polythiophene derivative, and the like, but the present invention is not limited thereto. Among these, as the host used when the light emitting layer performs triplet light emission (phosphorescence emission), metal chelated oxinoid compounds, dibenzofuran derivatives, dibenzothiophen derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives , Triphenylene derivatives and the like are suitably used.

The dopant material to be contained in the light emitting material is not particularly limited, but a compound having an aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, triphenylene, perylene, fluorene, 9,10-diphenylanthracene or 5,6,11,12-tetraphenylnaphthacene), furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9 Benzothiophene, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline, pyrazine, naphthyridine, quinoxaline, pyrrolopyridine, thioxanthine, etc. Bis (2- (4-diphenylaminophenyl) ethenyl) biphenyl, 4,4'-bis (N- (styrene) Aminostyryl derivatives such as benzyl-4-yl) -N-phenylamino) stilbene, aromatic acetylene derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, (2'-benzothiazolyl) quinolinone [9, 9-c] pyrrole derivatives, pyrocatechol derivatives, pyromethene derivatives, diketopyrrolo [3,4-c] pyrrole derivatives, 2,3,5,6-1H, 4H-tetrahydro- , Coumarin derivatives such as 9a, 1-gh] coumarin, azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole and triazole, metal complexes thereof and N, Aromatic amine derivatives represented by phenyl-N, N'-di (3-methylphenyl) -4,4'-diphenyl-1,1'-diamine.

Among these dopants, iridium (Ir), ruthenium (Ru), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re) may be used as the dopant used when the light emitting layer performs triplet light emission And at least one metal selected from the group consisting of metal complex compounds. The ligand preferably has a nitrogen-containing aromatic heterocycle such as a phenylpyridine skeleton, a phenylquinoline skeleton, or an N-heterocyclic carbene skeleton. However, the present invention is not limited to these, and suitable complexes are selected from the relationship with the required emission color, device performance, and host compound. Specific examples thereof include tris (2-phenylpyridyl) iridium complex, tris {2- (2-thiophenyl) pyridyl} iridium complex, tris {2- (2-benzothiophenyl) pyridyl} iridium complex, tris (2-phenylbenzothiazole) iridium complex, tris (2-phenylbenzoxazole) iridium complex, trisbenzoquinoline iridium complex, bis (2-phenylpyridyl) (acetylacetonate) iridium complex, bis {2- (2-benzothiophenyl) pyridyl} (acetylacetonate) iridium complex, bis (2-phenylbenzothiazole) (acetylacetonate) iridium complex, bis (2-phenylbenzooxazole) (acetylacetonate) iridium complex, bisbenzoquinoline (acetylacetonate) iridium complex, bis {2- (2,4-difluorophenyl) pyridyl} Tetraethylporphyrin platinum complex, {tris (senonyltrifluoroacetone) mono (1,10-phenanthroline)} europium complex, { (4,7-diphenyl-1,10-phenanthroline)} euramium complex, {tris (1,3-diphenyl-1,3-propanedione) mono , 10-phenanthroline)} euramium complex, trisacetylacetone terbium complex, and the like. A phosphorescent dopant described in JP-A-2009-130141 is also suitably used. Although not limited to these, iridium complexes or platinum complexes are preferably used because high-efficiency light emission is easily obtained.

The triplet light emitting material used as a dopant material may include only one type of each of the triplet light emitting materials, or two or more types of them may be used in combination. When two or more triplet light emitting materials are used, the total mass of the dopant material is preferably 30 mass% or less, more preferably 20 mass% or less, with respect to the host material. Preferable examples of the dopant include the following.

The light emitting layer may contain a third component for the purpose of adjusting the carrier balance in the light emitting layer or stabilizing the layer structure of the light emitting layer in addition to the host material and the triplet light emitting material. Specifically, the following examples can be mentioned.

In the light emitting device of the present invention, the electron transporting layer is a layer that injects electrons from a cathode and transports electrons. The efficiency of electron injection is high in the electron transporting layer, and it is desired to efficiently transport injected electrons. Therefore, the electron transporting layer is required to be a substance which has a large electron affinity, a high electron mobility, an excellent stability, and an impurity which is a trap, which is hard to occur at the time of production and use. Particularly, when a film having a large thickness is laminated, a compound having a molecular weight of 400 or more, which maintains a stable film quality, is preferable because a compound having a low molecular weight tends to crystallize and deteriorate the film quality. However, considering the transport balance of holes and electrons, when the electron transporting layer mainly plays a role of effectively preventing the holes from the anode from flowing to the cathode side without recombining, it is possible to use a material having a high electron transporting ability The effect of improving the luminous efficiency is equivalent to the case of being made of a material having a high electron transporting ability. Therefore, the electron transporting layer in the present invention includes a hole blocking layer capable of efficiently blocking the movement of holes.

Examples of the electron transporting material used for the electron transporting layer include condensed polycyclic aromatic derivatives such as naphthalene and anthracene, styryl-based aromatic ring derivatives represented by 4,4'-bis (diphenylethenyl) biphenyl, anthraquinone and diphenoquinone Quinoline derivatives such as quinone derivatives, phosphorus oxide derivatives, quinolinol complexes such as tris (8-quinolinolato) aluminum (III), benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes and flavonol metal complexes And various metal complexes such as complexes. The electron transporting material used in the electron transporting layer of the present invention is preferably an electron transporting material which contains an electron-accepting nitrogen and an aromatic suffix composed of elements selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus in view of low driving voltage and high- It is preferable to use a compound having a recall structure.

Herein, the electron-accepting nitrogen means a nitrogen atom forming a multiple bond with adjacent atoms. Since the nitrogen source has a high electron affinity, the multiple bonds have electron accepting properties. Therefore, aromatic heterocyclic rings containing electron-accepting nitrogen have high electron affinity. The electron transporting material having electron-accepting nitrogen easily receives electrons from the cathode having a high electron affinity, and can be driven at a lower voltage. Further, the supply of electrons to the light emitting layer is increased, and the recombination probability is increased, so that the light emitting efficiency is improved.

Examples of the heteroaryl ring containing electron-accepting nitrogen include a pyridine ring, a pyrazine ring, a pyrimidine ring, a quinoline ring, a quinoxaline ring, a naphthyridine ring, a pyrimidopyrimidine ring, a benzoquinoline ring, a phenanthroline ring, Oxadiazole ring, thiazole ring, thiazole ring, thiadiazole ring, benzoxazole ring, benzothiazole ring, benzoimidazole ring, phenanthroididazole ring, and the like.

Examples of the compound having a heteroaryl ring structure include a benzoimidazole derivative, a benzoxazole derivative, a benzothiazole derivative, an oxadiazole derivative, a thiadiazole derivative, a triazole derivative, a pyrazine derivative, a phenanthroline derivative, Quinoxaline derivatives, benzoquinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives and naphthyridine derivatives, and the like. Among them, imidazole derivatives such as tris (N-phenylbenzimidazol-2-yl) benzene, 1,3-bis [(4-tert- butylphenyl) -1,3,4-oxadiazolyl] , Triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole, benzocyclines such as bathocuproine and 1,3-bis (1,10 Phenanthroline-9-yl) benzene, benzoquinoline derivatives such as 2,2'-bis (benzo [h] quinolin-2-yl) -9,9'-spirobifluorene, Bipyridine derivatives such as 2,5-bis (6 '- (2', 2 "-bipyridyl)) - 1,1-dimethyl- - (2,2 ': 6'2 "-terpyridinyl)) benzene, bis (1-naphthyl) -4- (1,8-naphthyridin-2-yl) phenylphosphine Naphthyridine derivatives such as oxides are preferably used from the viewpoint of electron transporting ability. In addition, when these derivatives have a condensed polycyclic aromatic skeleton, the glass transition temperature is improved, and the electron mobility is also increased, which is more preferable because the effect of lowering the voltage of the light emitting device is great. In addition, in consideration of improvement in element lifetime, easiness of synthesis, and ease of obtaining raw materials, it is particularly preferable that the condensed polycyclic aromatic skeleton is an anthracene skeleton, a pyrene skeleton, or a phenanthroline skeleton. The electron transporting material may be used alone, but two or more kinds of the electron transporting materials may be used in combination or at least one of other electron transporting materials may be mixed with the electron transporting material.

Preferable examples of the electron transporting material are not particularly limited, but specific examples thereof include the following.

The electron transporting material may be used alone, but a donor material may be used in combination. Here, the donor material is a compound that facilitates injection of electrons from the cathode or electron injection layer into the electron transport layer by improving the electron injection barrier, and further improves the electric conductivity of the electron transport layer.

Preferable examples of the donor material include an alkali metal, an inorganic salt containing an alkali metal, a complex of an alkali metal and an organic material, an alkaline earth metal, an inorganic salt containing an alkaline earth metal, or a complex of an alkaline earth metal and an organic material . Preferred examples of the alkali metal and alkaline earth metal include alkaline metals such as lithium, sodium, potassium, rubidium and cesium which are low-temperature functions and have a great effect of improving the electron transporting ability, and alkaline earth metals such as magnesium, calcium, .

In addition, from the standpoint of ease of vapor deposition in vacuum and excellent handling, it is preferable that the metal is in a state of complex with an inorganic salt or an organic substance rather than a single metal. In addition, from the viewpoint of easy handling in the atmosphere and easy control of the concentration of the additive, it is more preferable to be in a state of complex with the organic material. Examples of the inorganic salt include oxides such as LiO and Li ₂ O, nitrides, fluorides such as LiF, NaF and KF, and fluorides such as Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Rb ₂ CO ₃ and Cs ₂ CO ₃ Carbonate and the like. Preferred examples of the alkali metal or alkaline earth metal include lithium and cesium from the viewpoint of obtaining a large low voltage driving effect. Preferred examples of the organic compound in the complex with the organic material include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole. Among them, a complex of an alkali metal and an organic compound is preferable from the viewpoint of the effect of lowering the voltage of the light emitting element more, and from the viewpoint of easiness of synthesis and thermal stability, complexation of lithium and an organic material is more preferable, Lithium quinolinol is particularly preferred.

The ionization potential of the electron transporting layer is not particularly limited, but is preferably 5.6 eV or more and 8.0 eV or less, and more preferably 6.0 eV or more and 7.5 eV or less.

The method of forming each of the layers constituting the light emitting element is not particularly limited, such as resistance heating deposition, electron beam deposition, sputtering, molecular lamination, or coating method, but resistance heating deposition or electron beam deposition is preferable in view of device characteristics.

In the light emitting device of the present invention, the thickness of the organic layer, which is the sum of the above layers, is not limited as it depends on the resistance value of the light emitting material, but is preferably 1 to 1000 nm. The film thicknesses of the light emitting layer, the electron transporting layer, and the hole transporting layer are preferably 1 nm or more and 200 nm or less, and more preferably 5 nm or more and 100 nm or less.

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

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

In the light emitting device of the present invention, the matrix method is a method in which pixels for display are arranged two-dimensionally, such as a lattice shape or a mosaic shape, and characters or images are displayed as a set of pixels. The shape and size of the pixel are determined depending on the application. For example, a square pixel of 300 mu m or less on one side is usually used for image and character display of a personal computer, a monitor, and a television, and in the case of a large display such as a display panel, a pixel on the order of one side is used. In the case of monochrome display, pixels of the same color can be arranged. In the case of color display, pixels of red, green and blue are aligned and displayed. In this case, there are typically a delta type and a stripe type. The driving method of the matrix may be either a line-sequential driving method or an active matrix. Since the structure of the line-sequential driving is simple, the active matrix may be superior in consideration of the operating characteristics.

In the light emitting device of the present invention, the segment method is a method of forming a pattern so as to display predetermined information, and emitting an area determined by the arrangement of the pattern. For example, a time or temperature display in a digital clock or a thermometer, an operation status display of an audio device or an electromagnetic cooker, or a panel display of an automobile. The matrix display and the segment display may coexist in the same panel.

The light emitting device of the present invention is also preferably used as a backlight for various devices. The backlight is mainly used 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 watch, an audio device, an automobile panel, a display panel, and a cover. Particularly, the light-emitting element of the present invention is preferably used for a liquid crystal display device, a backlight for personal computer use in which thinning is considered among them, and it is possible to provide an ultra-thin and lightweight backlight than conventional ones.

Example

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.

Example 1

A glass substrate (11 Ω / □, manufactured by Geomatec Co., Ltd., sputtered product) having 50 nm of an ITO transparent conductive film deposited was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with "Semicloclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultra pure water. This substrate was subjected to UV-ozone treatment for one hour immediately before the device was manufactured, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 10 ^-4 Pa or less. Thereafter, HI-1 was deposited as a hole injection layer to a thickness of 10 nm on the substrate by a resistance heating method. Next, NPD was deposited to a thickness of 100 nm as the first hole transporting layer. Subsequently, HT-1 was deposited to a thickness of 20 nm as a second hole transporting layer. Subsequently, a compound H-1 was used as a host material and a compound D-1 was used as a dopant material, and the dopant material was deposited to a thickness of 40 nm so that the doping concentration of the dopant material was 5 mass%. Subsequently, Compound E-1 as an electron transporting layer was laminated to a thickness of 20 nm.

Subsequently, 0.5 nm of lithium fluoride and 60 nm of aluminum were deposited to form a negative electrode, and a device having a square of 5 x 5 mm was produced. The film thickness referred to herein is the value of the crystal oscillation film thickness monitor display value. When this light emitting device was driven by direct current at 10 mA / cm 2, green luminescence with a luminous efficiency of 25.0 lm / W was obtained. When the light emitting device was continuously driven with a direct current of 10 mA / cm 2, the luminance was reduced by half in 2500 hours. The compounds NPD, HI-1, HT-1, H-1, D-1 and E-1 are shown below.

Examples 2 to 11

A light emitting device was fabricated in the same manner as in Example 1 except that the material described in Table 1 was used as the second hole transporting layer, the host material, and the dopant material. The results are shown in Table 1. HT-2 to HT-6, H-2 to H-4, D-2 and D-3 are shown below.

Comparative Examples 1 to 9

Emitting device was produced in the same manner as in Example 1 except that the material described in Table 1 was used as the second hole transporting layer and the host material. The results are shown in Table 1. HT-7 and H-5 to H-7 are shown below.

Example 12

A co-evaporation film of a compound E-1 and a donor metal (Li: lithium) was used instead of the compound E-1 at a deposition rate ratio of 100: 1 (= 0.2 nm / s: 0.002 nm / s), a light emitting device was fabricated in the same manner as in Example 1. The results are shown in Table 1.

Example 13

Compound E-2 was deposited to a thickness of 10 nm as the first electron transporting layer and a co-evaporation film of compound E-1 and a donor metal (Li: lithium) was deposited as the second electron transporting layer A light emitting device was fabricated in the same manner as in Example 1 except that a deposition rate ratio of 100: 1 (= 0.2 nm / s: 0.002 nm / s) was vapor-deposited to a thickness of 25 nm. The results are shown in Table 1. E-2 is a compound shown below.

Example 14

An electron transport layer with two-layer laminated structure, and a second as an electron transporting compound E-1 1 Deposition of the compound E-2 as the electron transporting layer to a thickness of 10㎚, and the donor material (Cs ₂ CO _3: Cesium carbonate) (= 0.2 nm / s: 0.002 nm / s) at a deposition rate of 100: 1 (= 0.2 nm / s: 0.002 nm / s) to form a laminate. The results are shown in Table 1.

Example 15

A co-evaporation film of a compound E-3 and a donor material (Liq: lithium quinolinol) was used instead of the compound E-1 at a deposition rate ratio of 1: 1 (= 0.05 nm / s: 0.05 nm / s), a light emitting device was fabricated in the same manner as in Example 1. The results are shown in Table 1. Further, E-3 is a compound shown below.

Examples 16-17

A light emitting device was produced in the same manner as in Example 15 except that the material shown in Table 1 was used as the electron transporting layer. The results are shown in Table 1. Further, E-4 and E-5 are the compounds shown below.

Examples 18 to 19

A light emitting device was produced in the same manner as in Example 1 except that the material shown in Table 1 was used as the electron transporting layer. The results are shown in Table 1.

Example 20

A glass substrate (11 Ω / □, manufactured by Geomatec Co., Ltd., sputtered product) having 50 nm of an ITO transparent conductive film deposited was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonically cleaned with "Semicloclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then washed with ultra pure water. This substrate was subjected to UV-ozone treatment for one hour immediately before the device was manufactured, placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 10 ^-4 Pa or less. Thereafter, a compound HI-1 as a hole injection layer was deposited on the substrate by a resistance heating method to a thickness of 10 nm. Next, NPD was deposited to a thickness of 100 nm as the first hole transporting layer. Subsequently, HT-1 was deposited to a thickness of 50 nm as a second hole transporting layer. Subsequently, a compound H-8 was used as a host material and a compound D-4 was used as a dopant material, and the dopant material was deposited to a thickness of 30 nm so that the doping concentration of the dopant material was 5 mass%. Subsequently, Compound E-1 as an electron transporting layer was laminated to a thickness of 35 nm.

Subsequently, lithium fluoride was vapor-deposited to a thickness of 0.5 nm, and aluminum was vapor-deposited to a thickness of 1000 nm to form a cathode. The film thickness referred to herein is the value of the crystal oscillation film thickness monitor display value. When the light emitting device was driven by DC at 10 mA / cm 2, high-efficiency red light emission with a luminous efficiency of 14.0 lm / W was obtained. When the light emitting device was continuously driven with a direct current of 10 mA / cm 2, the brightness was halved at 3000 hours. Compound H-8 is a compound shown below.

Examples 21 to 25

Emitting device was fabricated and evaluated in the same manner as in Example 20 except that the material described in Table 2 was used as the second hole transporting layer. The results are shown in Table 2. The compounds HT-8 and HT-9 are shown below.

Comparative Examples 10 to 13

Emitting device was manufactured in the same manner as in Example 20 except that the second hole transporting layer and the compound described in Table 2 were used as the host material. The results are shown in Table 2. The compounds HT-10 and H-9 are shown below.

Examples 26 to 27

Emitting device was manufactured and evaluated in the same manner as in Example 20 except that the second hole transporting layer and the material described in Table 2 were used as the electron transporting material. The results are shown in Table 2.

Examples 28 to 36

Emitting device was manufactured in the same manner as in Example 20 except that the second hole transporting layer and the compound described in Table 2 were used as the host material. The results are shown in Table 2. The compounds H-10 to H-18 are shown below.

Claims (7)

A light emitting device comprising at least a hole transporting layer and a light emitting layer between an anode and a cathode and emitting light by electric energy,
Wherein the hole transport layer comprises a compound represented by the following general formula (1), and the light emitting layer is a compound having an aromatic heterocyclic group containing electron-accepting nitrogen, and any one of the following general formulas (2) to And a compound represented by the formula (1).

In the general formula (1), R ¹ to R ⁴ may be the same or different, and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, An aryl group, a heteroaryl group, a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl group, a carbamoyl group, an amino group, a silyl group, -P (= O) R ⁵ R ⁶ . R ⁵ And R < ⁶ > is an aryl group or a heteroaryl group. L is a single bond or a divalent linking group.]

[In the formulas (2) to (4), R ⁷ to R ¹¹ and R ²¹ to R ²⁷ may be the same or different, and may be hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, An alkoxy group, an alkylthio group, an arylether group, an arylthioether group, an aryl group, a heteroaryl group, a halogen, a carbonyl group, a carboxyl group, an oxycarbonyl group, a carbamoyl group, an amino group, or a silyl group. R ⁷ to R ¹¹ may form a ring with adjacent substituents. Ring A or Ring B represents a benzene ring having a substituent or having no substituent, condensed at an arbitrary position with an adjacent ring. Y ¹ to Y ³ are -N (R ²⁸ ) -, -C (R ²⁹ R ³⁰ ) -, an oxygen atom, or a sulfur atom. R ²⁸ to R ³⁰ may be the same or different, and each is an alkyl group, an aryl group, or a heteroaryl group. R ²¹ to R ³⁰ may form a ring among adjacent substituents. L ¹¹ to L ¹⁷ are a single bond or an arylene group. X ¹ to X ⁵ represent a carbon atom or a nitrogen atom, and when X ¹ to X ⁵ are nitrogen atoms, R ⁷ to R ^{11 which} are substituents on the nitrogen atom are not present. Provided that the number of nitrogen atoms in X ¹ to X ⁵ is 1 or 2.] The method according to claim 1,
Wherein the hole transport layer is a compound represented by the following general formula (5).

[In the formula (5), R ¹ to R ⁴ are as defined above] 3. The method according to claim 1 or 2,
Wherein R ¹ and R ² in the general formula (1) are different groups. 4. The method according to any one of claims 1 to 3,
In the general formula (1), R ¹ and R ² together are an aryl group having a substituent or having no substituent. 5. The method according to any one of claims 1 to 4,
Wherein R ¹ is a phenyl group and R ² is a diphenyl phenyl group, a triphenyl phenyl group, a tetraphenyl phenyl group or a pentaphenyl phenyl group in the general formula (1). 6. The method according to any one of claims 1 to 5,
Wherein X ¹ and X ⁵ , or X ³ and X ⁵ , or X ¹ and X ³ in the general formulas (2) to (4) are nitrogen atoms. 7. The method according to any one of claims 1 to 6,
And at least an electron transporting layer is provided between the anode and the cathode and the electron transporting layer is a compound having a heteroaryl ring structure composed of electron accepting nitrogen and elements selected from carbon, hydrogen, nitrogen, oxygen, silicon, And a light emitting layer.