JP6504743B2 - Light emitting element - Google Patents

Description

  The present invention relates to a light emitting element capable of converting electrical energy into light. More particularly, the present invention relates to a light emitting device that can be used in the fields of display devices, flat panel displays, backlights, lights, interiors, signs, billboards, electrophotographic machines and light signal generators.

  In recent years, research on organic thin film light emitting devices has been actively conducted in which electrons injected from the cathode and holes injected from the anode emit light when they recombine within the organic phosphor sandwiched between the electrodes. This light emitting element is characterized by its thinness and high luminance light emission under a low driving voltage, and multicolor light emission by selecting a fluorescent material, and has attracted attention.

  This study is based on Kodak C.I. W. A number of commercialization studies have been conducted since Tang et al. Showed that the organic thin film element emits light at high brightness, and the organic thin film light emitting element has been steadily put to practical use, such as being adopted in the main display of mobile phones and the like. I'm going forward. However, there are still many technical issues, among which coexistence of high efficiency and long life of the device is one of the major issues.

The driving voltage of the device largely depends on the carrier transport material that transports carriers such as holes and electrons to the light emitting layer. Among them, materials having a carbazole skeleton are known as materials for transporting holes (hole transport materials) (see, for example, Patent Documents 1 and 2).
Further, since the material having the carbazole skeleton has a high triplet level, it is known as a host material of a light emitting layer (see, for example, Patent Document 3). Furthermore, an organic electroluminescent device is disclosed that contains an indolocarbazole derivative as a host material together with a phosphorescent dopant (see, for example, Patent Document 4).

JP-A-8-3547 Korean Patent Application Publication No. 2010-0079458 Unexamined-Japanese-Patent No. 2003-133075 International Publication No. 2008/056746

However, in the prior art, it was difficult to sufficiently lower the drive voltage of the device. Moreover, even if the driving voltage of the device could be lowered, the luminous efficiency and the durable life of the device were insufficient. Thus, no technology has yet been found that can achieve both high luminous efficiency and durable life.
An object of the present invention is to solve the problems of the prior art and to provide an organic thin film light emitting device having improved luminous efficiency and durable life.

  In order to solve the problems described above and to achieve the object, the light emitting device of the present invention is a light emitting device that comprises at least a hole transport layer and a light emitting layer between an anode and a cathode and emits light by electrical energy. The hole transport layer contains a compound represented by the following general formula (1), and the light emitting layer is a compound having an aromatic heterocyclic group containing an electron accepting nitrogen, and the following general formula (2) It is characterized by containing the compound represented by either of-(4).

（一般式（１）中、Ｒ^１〜Ｒ^４は、それぞれ同じでも異なっていてもよく、水素、アルキル基、シクロアルキル基、複素環基、アルケニル基、シクロアルケニル基、アルキニル基、アルコキシ基、アルキルチオ基、アリールエーテル基、アリールチオエーテル基、アリール基、ヘテロアリール基、ハロゲン、カルボニル基、カルボキシル基、オキシカルボニル基、カルバモイル基、アミノ基、シリル基、−Ｐ（＝Ｏ）Ｒ^５Ｒ^６からなる群より選ばれる。Ｒ^５およびＲ^６は、アリール基またはヘテロアリール基である。Lは単結合または二価の連結基である。

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

In the general formulas (2) to (4), R ^{7 to} R ¹¹ and R ^{21 to} R ²⁷ may be the same as or different from each other, and hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, cyclo Alkenyl, alkynyl, alkoxy, alkylthio, arylether, arylthioether, aryl, heteroaryl, halogen, carbonyl, carboxyl, oxycarbonyl, carbamoyl, amino or silyl . Ring A or ring B represents a substituted or unsubstituted benzene ring which is fused at any position with the 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 represents an alkyl group, an aryl group or a heteroaryl group. R ^{21 to} R ³⁰ may form a ring with adjacent substituents. L ^{11 to} L ¹⁷ are a single bond or an arylene group. X ¹ to X ⁵ represents a carbon atom or a nitrogen ^atom, when X 1 to X ⁵ is a nitrogen atom, ^R 7 ^{to R 11} is a substituent on the nitrogen atom is not present. However, the number of nitrogen atoms in X ^{1 to} X ⁵ is 1 or 2. )

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

  The present invention is a light emitting device including at least a hole transporting layer and a light emitting layer between an anode and a cathode and emitting light by electrical energy, wherein the hole transporting layer is a compound represented by the following general formula (1) And a light emitting element characterized in that the light emitting layer contains a compound having an aromatic heterocyclic group containing an electron accepting nitrogen.

  The compound having an electron accepting nitrogen-containing aromatic heterocyclic group used in the present invention has a high electron injecting and transporting ability, and therefore, by using it as a light emitting layer, an organic thin film light emitting element with high luminous efficiency and low driving voltage Can be given. However, since this light emitting layer has very high electron injecting and transporting ability, depending on the type of the hole transport layer used in combination, the recombination region in the light emitting layer is localized to the hole transport layer side, and the triplet is generated. Energy and electrons leak into the hole transport layer, which may cause a decrease in light emission efficiency of the device and a deterioration in durability.

  On the other hand, the inventors of the present invention have found that by using the compound represented by the general formula (1) as the hole transport layer, it is possible to improve the luminous efficiency and the durability significantly. That is, the compound represented by the general formula (1) has high electron blocking property and high triplet energy, and even if the recombination region in the light emitting layer is localized on the hole transport layer side, it is triple. Since energy and electrons can be confined in the light emitting layer, higher efficiency and longer life can be realized.

  That is, using a compound represented by the general formula (1) for the hole transport layer and using a compound having an aromatic heterocyclic group containing an electron accepting nitrogen for the light emitting layer has high luminous efficiency and durability. It is a preferable combination to achieve both.

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 hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group Group, aryl ether group, aryl thioether group, aryl group, heteroaryl group, halogen, carbonyl group, carboxyl group, oxycarbonyl group, carbamoyl group, amino group, silyl group, -P (= O) R ⁵ R ⁶ It is chosen from the group. R ⁵ and R ⁶ are an aryl group or a heteroaryl group. L is a single bond or a divalent linking group.
Of these substituents, hydrogen may be deuterium.

  In the compound represented by the general formula (1), the alkyl group is, for example, a saturated group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, etc. An aliphatic hydrocarbon group is shown, which may or may not 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, an aryl group, heteroaryl group etc. can be mentioned, This point is common also to the following description. The carbon number of the alkyl group is not particularly limited, but is usually in the range of 1 or more and 20 or less, more preferably 1 or more and 8 or less from the viewpoint of availability and cost.

  In the compound represented by the general formula (1), the cycloalkyl group is, for example, a saturated alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl, norbornyl, adamantyl or the like, which may have a substituent. You do not need to have it. The carbon number of 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 is, for example, an aliphatic ring having an atom other than carbon, such as a pyran ring, a piperidine ring and a cyclic amide in the ring, and this represents a substituent It may or may not have. The carbon number 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 is, for example, an unsaturated aliphatic hydrocarbon group containing a double bond such as a vinyl group, an allyl group or a butadienyl group, which has a substituent. It may or may not have. The carbon number of the alkenyl 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 cycloalkenyl group means, for example, an unsaturated alicyclic hydrocarbon group containing a double bond such as cyclopentenyl group, cyclopentadienyl group, cyclohexenyl group and the like This may or may not have a substituent. The carbon number of the cycloalkenyl 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 alkynyl group is, for example, an unsaturated aliphatic hydrocarbon group containing a triple bond such as an ethynyl group, which has a substituent even if it has one or more substituents. It does not have to be. The carbon number of the alkynyl 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 alkoxy group means a functional group in which an aliphatic hydrocarbon group is linked via an ether bond, such as a methoxy group, an ethoxy group or a propoxy group, for example. The hydrocarbon group may or may not have a substituent. The carbon number of the alkoxy group is not particularly limited, but is usually in the range of 1 or more and 20 or less.

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 by 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 or more and 20 or less.
In the compound represented by the general formula (1), the aryl ether group represents a functional group to which an aromatic hydrocarbon group such as a phenoxy group is bonded via an ether bond, for example. The aromatic hydrocarbon group is a substituent Or may not have. The carbon number of the aryl ether group is not particularly limited, but is usually in the range of 6 to 40.

  In the compound represented by the general formula (1), the arylthioether group is one in which the oxygen atom of the ether bond of the arylether group is substituted by a sulfur atom. The aromatic hydrocarbon group in the aryl ether group may or may not have a substituent. The carbon number of the aryl ether group is not particularly limited, but is usually in the range of 6 to 40.

  In the compound represented by the general formula (1), the aryl group is, for example, an aromatic group such as phenyl group, naphthyl group, biphenyl group, fluorenyl group, phenanthryl group, anthracenyl group, triphenylenyl group, terphenyl group, pyrenyl group, etc. Indicates a hydrocarbon group. The aryl group may or may not have a substituent. The carbon number 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 is a furanyl 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, a benzothiophenyl group, A cyclic aromatic group having one or more atoms other than carbon atoms in the ring, such as indolyl group, dibenzofuranyl group, dibenzothiophenyl group and carbazolyl group, may be unsubstituted or substituted. The carbon number of the heteroaryl group is not particularly limited, but is usually in the range of 2 or more and 30 or less.

In the compound represented by the general formula (1), halogen represents 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, and examples of the substituent include an alkyl group, A cycloalkyl group, an aryl group, etc. are mentioned, 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, a heteroaryl group and the like, and these substituents The group may be further substituted.
In the compound represented by the general formula (1), the silyl group indicates, 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. It is also good. The carbon number of the silyl group is not particularly limited, but is usually in the range of 3 or more and 20 or less. The silicon number is usually in the range of 1 or more and 6 or less.

  In the compound represented by the general formula (1), L is a single bond or a divalent linking group, and as the divalent linking group, for example, a phenylene group, a naphthylene group, a biphenylene group, a fluorenylene group, a phenanthrylene group, Arylene groups such as terphenylene group, anthracenylene group, pyrenylene group, furanylene group, thiophenylene group, pyridylene group, quinolinylene group, isoquinolinylene group, pyrazinylene group, pyrimidylene group, naphthyrylene group, benzofuranylene group, benzothiophenylene group, indolylene group, Examples thereof include heteroarylene groups such as dibenzofuranylene group, dibenzothiophenylene group and carbazolylene group. These may or may not have a substituent.

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

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

  The electron accepting nitrogen as referred to herein represents a nitrogen atom which forms a multiple bond with the adjacent atom. Since the nitrogen atom has a high electronegativity, the multiple bond has electron accepting properties. Therefore, aromatic heterocycles containing an electron accepting nitrogen have high electron affinity. The compounds of the present invention having an electron accepting nitrogen show high electron injection and transport properties, so that the recombination probability is high, and the light emission efficiency is improved.

  Examples of the aromatic heterocyclic group containing an electron accepting nitrogen include pyridyl group, quinolinyl group, isoquinolinyl group, quinoxanyl group, pyrazinyl group, pyrimidyl group, pyridazinyl group, phenanthrolinyl group, imidazopyridyl group, acridyl group, benzoimidazolyl group Among the above heteroaryl groups, such as benzoxazolyl group, benzothiazolyl group, bipyridyl group, terpyridyl group, etc., as an atom other than carbon, an aromatic heterocyclic ring having at least one or more electron accepting nitrogen atoms in the ring Indicates a group. In the compound having an aromatic heterocyclic group containing an electron accepting nitrogen used in the present invention, the number of the electron accepting nitrogen contained in one aromatic heterocyclic ring is 1 or 2. However, when the compound having an aromatic heterocyclic group containing an electron accepting nitrogen has a plurality of aromatic heterocycles containing an electron accepting nitrogen, it may have three or more electron accepting nitrogens. The aromatic heterocyclic group containing an electron accepting nitrogen may have an alkyl group or a cycloalkyl group as a substituent.

  In general, when depositing an organic material, it is desirable that the difference between the decomposition temperature and the sublimation temperature be large because the deposition is performed under high temperature for a long time. In a compound having an aromatic heterocyclic group containing an electron accepting nitrogen, if the number of electron accepting nitrogen contained in one aromatic heterocycle is 3 or more, the compound itself must be deposited at a high temperature. The heat load applied to is increased, and part of it may be thermally decomposed and deposited. There is a concern that such contamination with decomposition products may greatly affect the device characteristics, particularly the life. In order to reduce the concern, the number of electron accepting nitrogens contained in one aromatic heterocyclic ring is preferably 2 or less.

  When the compound having an aromatic heterocyclic group containing an electron accepting nitrogen is a monoazine compound or a diazine compound in which the number of electron accepting nitrogens contained in one aromatic heterocyclic ring is 2 or less, from the electron transporting layer It is preferable because the electron can be easily received and the electron injection property to the light emitting layer becomes high, the recombination probability becomes high and the light emission efficiency is improved.

  In the case where the compound having an aromatic heterocyclic group containing an electron accepting nitrogen is a compound represented by the following general formulas (2) to (4), high electron injection transportability is exhibited, so that the light emission efficiency is improved. Moreover, since a stable thin film can be formed, it leads to the improvement of durability, 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 a single bond, hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl Group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, arylether group, arylthioether group, aryl group, heteroaryl group, halogen, carbonyl group, carboxyl group, oxycarbonyl group, carbamoyl group, amino group or silyl It is a group. In addition, R ^{7 to} R ¹¹ may form a ring with adjacent substituents. Ring A or ring B represents a substituted or unsubstituted benzene ring which is fused at any position with the 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 represents an alkyl group, an aryl group or a heteroaryl group. R ^{21 to} R ³⁰ may form a ring with adjacent substituents. L ^{11 to} L ¹⁷ are a single bond or an arylene group. X ¹ to X ⁵ represents a carbon atom or a nitrogen ^atom, when X 1 to X ⁵ is a nitrogen atom, ^R 7 ^{to R 11} is a substituent on the nitrogen atom is not present. However, 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 of L ^{11 to} L ¹⁷ is formed by removing one hydrogen atom from each of two ring carbon atoms of an aromatic compound (arene). And a phenylene group, a naphthylene group, a biphenylene group, a fluorenylene group, a phenanthrylene group, a terphenylene group, an anthracenylene group, a pyrenylene group and the like. These may or may not have a substituent.
The description of the other substituents is the same as that of 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 adjacent two of X ^{1 to} X ⁵ can not be nitrogen atoms simultaneously. . Since adjacent two of X ^{1 to} X ⁵ can not simultaneously be nitrogen atoms, the thermally weak nitrogen-nitrogen double bond disappears, and the thermal stability of the whole molecule is improved. In addition, when the number of nitrogen atoms in X ^{1 to} X ⁵ is 1 or 2, the electron can easily be received from the electron transport layer, and the electron injection property to the light emitting layer can be enhanced. It is preferable because the probability is increased and the light emission efficiency is improved.

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 the thermal stability and the electron injection / transport characteristics.

Furthermore, it is preferable that at least two of R ^{7 to} R ¹¹ are aryl groups. When at least two of R ^{7 to} R ¹¹ are aryl groups, the height of planarity and ease of stacking of the ring structure composed of X ^{1 to} X ⁵ and carbon atoms can be suppressed and stable. Since a thin film can be formed and energy can be efficiently transferred to the dopant, highly efficient light emission is possible.

Among them, in view of easiness of synthesis, at least two of R ^{7 to} R ¹¹ each have 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 It is preferable that a stable thin film can be formed by using a phenyl group as a group.

  Since the indolocarbazole skeleton has a high triplet level, compounds having the indolocarbazole skeleton represented by the general formulas (2) to (4) can also maintain a high triplet level, which is easy. High emission efficiency can be achieved.

Among them, a compound in which L ^{11 to} L ¹⁷ is a single bond and R ^{21 to} R ²⁶ are hydrogen is preferable in terms of easiness of synthesis.

Furthermore, R ²⁷ is preferably an aryl group in terms of ease of synthesis. Among them, it is preferable that R ²⁷ is a phenyl group because a stable thin film can be formed.

  As compounds having an aromatic heterocyclic group containing an electron accepting nitrogen, WO 2011/148909 pamphlet, WO 2011/1322683 pamphlet, WO 2011/132684 pamphlet, WO 2008/056746 Pamphlet, WO 2009/084546 Pamphlet, WO 2010/136109 Pamphlet, WO 2011/001956 Pamphlet, WO 2011/139055 Pamphlet, WO 2011/055934 Pamphlet, Korean Patent Publication No. 2011-120075, WO 2011/136755 pamphlet, WO 2011/136520 pamphlet, WO 2011/132865 bread Let, although compounds described in WO 2012/023947 pamphlet can be mentioned, and specific examples thereof include the following compounds.

The compound represented by the general formula (1) is preferably such that carbazoles are linked as represented by the following general formula (5) from the viewpoint of easiness of synthesis and hole transportability.

Furthermore, from the viewpoint of improving the durability of the light emitting element, an asymmetric carbazole dimer is preferable. In the symmetrical structure, the crystallinity is high and the stability of the thin film is lacking, and the durability of the device is reduced.
Further, from the viewpoint of heat resistance, R ¹ and R ² in the general formula (1) are more preferably an aryl group having a substituent or no substituent.

  As compounds represented by such general formula (1), International Publication No. 2011/122132, International Publication No. 2011/125680, International Publication No. 2011/48821, International Publication No. 2011/48822, International Publication No. The compounds having a carbazole skeleton described in 2011/24451, WO 2012/1986, and Korean Patent Publication 2010-79458 can be mentioned, and specifically, the following compounds can be mentioned.

  The compound represented by General formula (1) can be manufactured by a well-known method. That is, the compound can be easily synthesized by the Suzuki coupling reaction of a bromo compound of carbazole substituted at position 9 and a monoboronic acid of carbazole substituted at position 9; however, the production method is not limited thereto.

  Next, the embodiment of the light emitting device of the present invention will be described in detail. The light emitting device of the present invention has an anode and a cathode, and a hole transport layer and a light emitting layer interposed between the anode and the cathode, and the light emitting layer emits light by electrical energy.

The layer structure between the anode and the cathode in such a light emitting element is not limited to the structure comprising a hole transport layer and a light emitting layer,
1) Hole transport layer / luminescent layer / electron transport layer 2) Hole injection layer / hole transport layer / luminescent layer / electron transport layer 3) Hole transport layer / luminescent layer / electron transport layer / electron injection layer 4) A laminated structure of hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer may be mentioned. Each of the layers described above 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 device, and at least one of them preferably is transparent or semitransparent in order to extract light. . In general, the anode formed on the substrate is a transparent electrode.

  In the light emitting device of the present invention, the material used for the anode is a material capable of efficiently injecting holes into the organic layer, and zinc oxide, tin oxide, indium oxide, tin oxide if it is transparent or semitransparent to take out light. Conductive metal oxides such as indium (ITO) and zinc indium oxide (IZO) or metals such as gold, silver and chromium, inorganic conductive substances such as copper iodide and copper sulfide, polythiophene, polypyrrole and polyaniline The conductive polymer and the like are not particularly limited, but it is particularly desirable to use ITO glass or Nesa glass. Although these electrode materials may be used alone, 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 current sufficient for light emission of the element, but the resistance is preferably low from the viewpoint of the power consumption of the element. For example, an ITO substrate of 300 Ω / sq or less functions as a device electrode, but now it is also possible to supply a substrate of about 10 Ω / sq, so use a substrate with a low resistance of 20 Ω / sq or less Is particularly desirable. The thickness of ITO can be arbitrarily selected in accordance with the resistance value, but it is usually used usually in the range of 50 to 300 nm.

In addition, in order to maintain the mechanical strength of the light emitting element, it is preferable to form the light emitting element on a substrate. As the substrate, a glass substrate such as soda glass or non-alkali glass is preferably used. The thickness of the glass substrate is sufficient if it has a thickness sufficient to maintain the mechanical strength, so 0.5 mm or more is sufficient. As for the material of the glass, non-alkali glass is preferable because it is preferable that the amount of ions eluted from the glass be small. Alternatively, a soda lime glass with a barrier coating such as SiO ₂ may also be used, as it is commercially available. Furthermore, if the first electrode functions stably, the substrate does not have to be glass, and for example, the anode may be formed on a plastic substrate. The ITO film forming method is not particularly limited, such as an electron beam method, a sputtering method and a chemical reaction method.

  In the light emitting element of the present invention, the material used for the cathode is not particularly limited as long as it is a substance that can efficiently inject electrons into the light emitting layer. Generally, metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium, or alloys of these metals with low work function metals such as lithium, sodium, potassium, calcium and magnesium, etc. Is preferred. Among them, aluminum, silver and magnesium are preferable as main components from the viewpoints of electric resistance value, ease of film formation, stability of film, luminous efficiency and the like. In particular, when it is composed of magnesium and silver, it is preferable because electron injection to the electron transporting layer and the electron injecting layer in the present invention becomes easy and low voltage driving becomes possible.

  Furthermore, metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium, or alloys using these metals for cathodic protection, inorganic substances such as silica, titania and silicon nitride, polyvinyl alcohol, polyvinyl chloride It is mentioned as a preferable example to laminate organic polymer compounds, such as a hydrocarbon type polymer compound, on a cathode as a protective film layer. However, in the case of an element structure (top emission structure) in which light is extracted from the cathode side, the protective film layer is selected from materials having optical transparency in the visible light region. The method of producing these electrodes is not particularly limited, such as resistance heating, electron beam, sputtering, ion plating and coating.

  In the light emitting device of the present invention, the hole injection layer is a layer inserted between the anode and the hole transport layer. The hole injection layer may be a single layer or a plurality of stacked layers. The presence of a hole injection layer between the hole transport layer and the anode is preferable because it can be driven at a lower voltage and not only the durability life is improved but also the carrier balance of the device is improved and the light emission efficiency is improved.

  The material used for the hole injection layer is not particularly limited. 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-) Benzidine derivatives such as 4-aminophenyl) -N, N-diphenyl-4,4'-diamino-1,1'-biphenyl (TPD 232), 4,4 ', 4 "-tris (3-methylphenyl (phenyl) amino ) Starbursts such as triphenylamine (m-MTDATA), 4,4 ′, 4 ′ ′-tris (1-naphthyl (phenyl) amino) triphenylamine (1-TNATA) Material group called arylamine, biscarbazole derivative such as bis (N-arylcarbazole) or bis (N-alkylcarbazole), pyrazoline derivative, stilbene compound, hydrazone compound, benzofuran derivative, thiophene derivative, oxadiazole derivative, As the heterocyclic compounds such as phthalocyanine derivatives and porphyrin derivatives, polycarbonates and styrene derivatives having the above-mentioned monomers in the side chain, polythiophenes, polyanilines, polyfluorenes, polyvinylcarbazoles, polysilanes and the like are used in the polymer system. The compounds represented by the general formula (1) or (5) can be similarly used in the hole injection layer, and among these, those having a shallow HOMO level smoothly smoothly from the anode to the hole transport layer. It is more preferably used from the viewpoint of injecting and transporting the holes.

  These materials may be used alone or in combination of two or more. Alternatively, a plurality of materials may be stacked to form a hole injection layer. Furthermore, it is more preferable that this hole injection layer is made of an acceptor material alone or when the hole injection material as described above is doped with an acceptor material, because the above-mentioned effects are more remarkably obtained. . An acceptor property material is a material which forms a charge transfer complex with the material which comprises a positive hole transport layer which contact | connects when using it as a single layer film, and the material which comprises a positive hole injection layer when using it doped. When such a material is used, the conductivity of the hole injection layer is improved, which further contributes to the reduction of the drive voltage of the device, and effects such as the improvement of the light emission efficiency and the improvement of the durable life are obtained.

  Examples of the acceptor material include iron chloride (III), aluminum chloride, gallium chloride, indium chloride, metal chloride such as antimony chloride, molybdenum oxide, vanadium oxide, tungsten oxide, metal oxide such as ruthenium oxide, Charge transfer complexes such as tris (4-bromophenyl) aminium hexachloroantimonate (TBPAH). Further, 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 suitably used. Specific examples of these compounds include hexacyanobutadiene, hexacyanobenzene, tetracyanoethylene, tetracyanoquinodimethane (TCNQ), tetrafluorotetracyanoquinodimethane (F4-TCNQ), radiarene derivative, p-fluoranil, p-chloranil, p-bromonyl, p-benzoquinone, 2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone, tetramethylbenzoquinone, 1,2,4,5-tetracyanobenzene, o-dicyanobenzene, p-dicyano Benzene, 1,4-dicyanotetrafluorobenzene, 2,3-dichloro-5,6-dicyanobenzoquinone, p-dinitrobenzene, m-dinitrobenzene, o-dinitrobenzene, p-cyanonitrobenzene, m-cyanonitrobenzene, o - Anonitrobenzene, 1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 1-nitronaphthalene, 2-nitronaphthalene, 1,3-dinitronaphthalene, 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 easy to deposit, and the above-described effects can be easily obtained. In either case where the hole injection layer is composed of the acceptor material alone or in the case where the hole injection layer is doped with the acceptor material, the hole injection layer may be a single layer, A plurality of layers may be stacked.

  The acceptor property material is not particularly limited, but it is 0.1 to 50 parts by mass, more preferably 0.5 to 20 parts by mass with respect to the compound represented by the general formula (1) or (5). It is preferable to use in the range.

  In the light emitting device of the present invention, the hole transport 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) is suitably used for the hole transport layer of the light emitting device because it has high triplet level, high hole transport property and thin film stability. . The hole transport layer may be either a single layer or a plurality of stacked layers.

  When it is configured of a plurality of hole transport layers, the hole transport layer containing the compound represented by the general formula (1) or (5) is preferably in direct contact with the light emitting layer. It is because the compound represented by General formula (1) or (5) has high electron blocking property, and can prevent the penetration | invasion of the electron which flows out from a light emitting layer. Furthermore, since the compound represented by General Formula (1) or (5) has a high triplet level, it also has the effect of confining the excitation energy of a triplet light emitting material. Therefore, even when the light emitting layer contains a triplet light emitting material, the hole transport layer containing the compound represented by the general formula (1) or (5) 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 (5), or other materials may be mixed as long as the effects of the present invention are not impaired. In this case, the same material group as the material used for the above-mentioned hole injection layer is mentioned as a preferable example, but when it is used for the hole transport layer, the HOMO standard equivalent to or deeper than the material used for the hole injection layer It is more preferable to select the order material. In this case, as other materials to be 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 (TPD 232), 4,4 ', 4 "-tris (3-methylphenyl (phenyl) amino) triphenyl Starburst aryls such as amines (m-MTDATA), 4,4 ', 4 "-tris (1-naphthyl (phenyl) amino) triphenylamine (1-TNATA) Material group called “min”, biscarbazole derivative such as bis (N-arylcarbazole) or bis (N-alkylcarbazole), pyrazoline derivative, stilbene compound, hydrazone compound, benzofuran derivative, thiophene derivative, oxadiazole derivative, phthalocyanine Derivatives, heterocyclic compounds such as porphyrin derivatives, polycarbonates and styrene derivatives having the above-mentioned monomer in the side chain in polymer systems, polythiophenes, polyanilines, polyfluorenes, polyvinylcarbazoles and polysilanes, etc. may be mentioned.

  In the light emitting device of the present invention, the light emitting layer may be either a single layer or a plurality of layers. When the light emitting layer is a plurality of layers, each light emitting layer is respectively formed of a light emitting material (host material, dopant material), and each light emitting layer is a mixture of host material and dopant material, or host material alone. Also, a mixture of two types of host materials and one type of dopant material may be used. That is, in the light emitting device of the present invention, in each light emitting layer, only the host material or the dopant material may emit light, or both the host material and the dopant material may emit light. From the viewpoint of efficiently using electric energy and obtaining light emission of high color purity, the light emitting layer is preferably made of a mixture of a host material and a dopant material. Further, each of the host material and the dopant material may be of one type or a combination of two or more. The dopant material may be contained in the entire host material or may be partially contained. The dopant material may be either laminated or dispersed. The dopant material can control emission color. The amount of the dopant material is preferably 30% by mass or less, more preferably 20% by mass or less, based on the host material, because concentration quenching occurs if the amount is too large. The doping method can be formed by co-evaporation with a host material, but may be simultaneously mixed with the host material and then simultaneously deposited.

  A compound having an aromatic heterocyclic group containing an electron accepting nitrogen is suitably used for a light emitting layer of a light emitting device because it has high electron transporting property and thin film stability. In addition, since a compound having an aromatic heterocyclic group containing an electron accepting nitrogen has high electron transportability and thin film stability, it is preferably used as a host material.

  Furthermore, since many compounds having an aromatic heterocyclic group containing an electron accepting nitrogen have high triplet levels, they are preferably used as a host material of a device using a triplet light emitting material. As the compound having an aromatic heterocyclic group containing an electron accepting nitrogen, particularly preferable compounds include compounds represented by General Formulas (2) to (4).

  In the light emitting device of the present invention, the light emitting material includes, in addition to a compound having an aromatic heterocyclic group containing an electron accepting nitrogen, a fused ring derivative such as anthracene or pyrene which has long been known as a light emitter; -Quinolinola) metal chelated oxinoid compounds such as aluminum, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives Cyclopentadiene derivatives, oxadiazole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, polymer systems, polyphenylene vinylene derivatives, polyparaf Vinylene derivatives, and, polythiophene derivative is not particularly limited but can be used.

  The host material contained in the light emitting material need not be limited to only one kind of compound, and a plurality of compounds represented by General Formulas (2) to (4) may be mixed and used, or General Formulas (2) to (4) And the other host materials may be used as a mixture. Further, the compounds represented by the general formulas (2) to (4) may be laminated, or the compounds represented by the general formulas (2) to (4) and another host material may be laminated and used. Other host materials include, but are not limited to, compounds having a fused aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, indene and derivatives thereof, N, N'- Aromatic amine derivatives such as dinaphthyl-N, N'-diphenyl-4,4'-diphenyl-1,1'-diamine; metal chelated oxinoid compounds such as tris (8-quinolinate) aluminum (III); Bis-styryl derivatives such as styrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives, thiadiazo For pyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, and polymer systems, polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives, etc. can be used, but are limited thereto It is not a thing. Among them, as a host used when the light emitting layer performs triplet light emission (phosphorescent light emission), metal chelated oxinoid compounds, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, triphenylene derivatives, etc. Is preferably used.

  Although the dopant material contained in the light emitting material is not particularly limited, a compound having an aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, triphenylene, perylene, fluorene, indene or a derivative thereof (eg, 2- (benzothiazole-2-) Yl) -9,10-diphenyl anthracene, 5,6,11,12-tetraphenyl naphthacene, etc., furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9'-spirobisilafluorene, benzothiophene Compounds having a heteroaryl ring such as benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline, pyrazine, naphthyridine, quinoxaline, pyrrolopyridine, thioxanthene and derivatives thereof, distyryl bees Aminostyryls such as Zen derivatives, 4,4'-bis (2- (4-diphenylaminophenyl) ethenyl) biphenyl, 4,4'-bis (N- (stilbene-4-yl) -N-phenylamino) stilbene and the like Derivative, aromatic acetylene derivative, tetraphenyl butadiene derivative, stilbene derivative, aldazine derivative, pyrromethene derivative, diketopyrrolo [3,4-c] pyrrole derivative, 2,3,5,6-1H, 4H-tetrahydro-9- (2 Coumarin derivatives such as' -benzothiazolyl) quinolizino [9,9a, 1-gh] coumarin, imidazoles, such as imidazole, thiazoles, thiadiazoles, carbazoles, oxazoles, oxadiazoles, triazoles and metal complexes thereof and N, N'-diphenyl -N, N'-di (3-meth And aromatic amine derivatives typified by phenyl) -4,4'-diphenyl-1,1'-diamine.

  Among them, as a dopant used when the light emitting layer performs triplet light emission (phosphorescent light emission), iridium (Ir), ruthenium (Ru), palladium (Pd), platinum (Pt), osmium (Os), and rhenium are used. It is preferable that it is a metal complex compound containing at least one metal selected from the group consisting of (Re). The ligand preferably has a nitrogen-containing aromatic heterocyclic ring such as a phenylpyridine skeleton, a phenylquinoline skeleton, or an N-heterocyclic carbene skeleton. However, the present invention is not limited to these, and an appropriate complex is selected depending on the required emission color, the device performance, and the relationship with the host compound. Specifically, tris (2-phenyl pyridyl) iridium complex, tris {2- (2- thiophenyl) pyridyl} iridium complex, tris {2- (2-benzothio phenyl) pyridyl} iridium complex, tris (2- phenyl) Benzothiazole) iridium complex, tris (2-phenylbenzoxazole) iridium complex, tris benzoquinoline iridium complex, bis (2-phenyl pyridyl) (acetylacetonato) iridium complex, bis {2- (2-thiophenyl) pyridyl} iridium Complex, bis {2- (2-benzothiophenyl) pyridyl} (acetylacetonato) iridium complex, bis (2-phenylbenzothiazole) (acetylacetonato) iridium complex, bis (2-phenylbenzoxazole) (acetylaceto) And iridium complexes, bisbenzoquinoline (acetylacetonate) iridium complexes, bis {2- (2,4-difluorophenyl) pyridyl} (acetylacetonato) iridium complexes, tetraethyl porphyrin platinum complexes, {tris (senoyl trifluoro) Acetone) Mono (1,10-phenanthroline)} europium complex, {tris (cenoyltrifluoroacetone) mono (4,7-diphenyl-1,10-phenanthroline)} europium complex, {tris (1,3-diphenyl-1) 3, 3-propanedione) mono (1, 10-phenanthroline)} europium complex, trisacetylacetone terbium complex and the like. Moreover, the phosphorescence dopant described in Unexamined-Japanese-Patent No. 2009-130141 is also used suitably. Although not limited to these, an iridium complex or a platinum complex is preferably used because high efficiency light emission is easily obtained.

  The above-mentioned triplet light-emitting materials used as a dopant material may each be contained alone in the light-emitting layer, or may be used as a mixture of two or more. When two or more triplet light emitting materials are used, the total mass of the dopant material is preferably 30% by mass or less, more preferably 20% by mass or less, based on the host material. Examples of preferred dopants include the following.

  Furthermore, the light emitting layer may contain, in addition to the host material and the triplet light emitting material, 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. Specifically, the following examples may be mentioned.

  In the light emitting device of the present invention, the electron transport layer is a layer into which electrons are injected from the cathode and which further transports electrons. In the electron transport layer, it is desirable that the electron injection efficiency is high, and the injected electrons be efficiently transported. Therefore, the electron transport layer is required to be a substance having a large electron affinity, a large electron mobility, and a high stability, so that an impurity serving as a trap is not easily generated at the time of production and use. In particular, when laminating a thick film, a low molecular weight compound is likely to be deteriorated due to crystallization or the like, and therefore a compound having a molecular weight of 400 or more maintaining a stable film quality is preferable. However, when considering the transport balance of holes and electrons, if the electron transport layer mainly plays a role of efficiently blocking the flow of holes from the anode to the cathode side without recombination, electron transport Even if it is made of a material whose capacity is not so high, the effect of improving the luminous efficiency is equivalent to that of a material whose electron transporting ability is high. Therefore, the electron transporting layer in the present invention includes the same hole blocking layer capable of efficiently blocking the movement of holes.

  Electron transport materials used for the electron transport layer include fused polycyclic aromatic derivatives such as naphthalene and anthracene, styryl aromatic ring derivatives represented by 4,4'-bis (diphenylethenyl) biphenyl, anthraquinone and diphenoquinone, etc. And quinolinol complexes such as tris (8-quinolinolato) aluminum (III), benzoquinolinol complexes, hydroxyquinol complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes, and various metal complexes such as flavonol metal complexes. As the electron transport material used in the electron transport layer of the present invention, among the electron accepting nitrogen, carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus because the drive voltage is reduced and high efficiency light emission can be obtained. It is preferable to use a compound having an aromatic heterocyclic structure composed of an element selected from

  The electron accepting nitrogen as referred to herein represents a nitrogen atom which forms a multiple bond with the adjacent atom. Since the nitrogen atom has a high electronegativity, the multiple bond has electron accepting properties. Therefore, aromatic heterocycles containing an electron accepting nitrogen have high electron affinity. The electron transport material having electron accepting nitrogen facilitates receiving of electrons from the cathode having high electron affinity and enables lower voltage drive. In addition, since the supply of electrons to the light emitting layer is increased and the recombination probability is increased, the light emission efficiency is improved.

  The heteroaryl ring containing an electron accepting nitrogen includes, for example, pyridine ring, pyrazine ring, pyrimidine ring, quinoline ring, quinoxaline ring, naphthyridine ring, pyrimidopyrimidine ring, benzoquinoline ring, phenanthroline ring, imidazole ring, oxazole ring, Oxadiazole ring, triazole ring, thiazole ring, thiadiazole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, phenanthroimidazole ring and the like.

  Examples of compounds having these heteroaryl ring structures include benzoimidazole derivatives, benzoxazole derivatives, benzothiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, quinoline derivatives, benzo Preferred compounds include quinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives and naphthyridine derivatives. Among others, imidazole derivatives such as tris (N-phenylbenzimidazol-2-yl) benzene, oxadiazole derivatives such as 1,3-bis [(4-tert-butylphenyl) -1,3,4-oxadiazolyl] phenylene , Triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole, phenanthroline derivatives such as vasocuproin and 1,3-bis (1,10-phenanthrolin-9-yl) benzene, 2,2 Benzoquinoline derivatives such as' -bis (benzo [h] quinolin-2-yl) -9,9'-spirobifluorene, 2,5-bis (6 '-(2', 2 ''-bipyridyl))-1 Bipyridine derivatives such as 1,1-dimethyl-3,4-diphenylsilole, 1,3-bis (4 '-(2,2': 6'2 ")- Pirijiniru)) terpyridine derivatives such as benzene, naphthyridine derivatives such as bis (1-naphthyl) -4- (1,8-naphthyridin-2-yl) phenylphosphine oxide are preferably used from the viewpoint of electron transporting capability. In addition, when these derivatives have a fused polycyclic aromatic skeleton, the glass transition temperature is improved, the electron mobility is also increased, and the effect of lowering the voltage of the light emitting element is large, which is more preferable. Furthermore, in consideration of the improvement of the device endurance life, the ease of synthesis, and the easy availability of raw materials, the fused polycyclic aromatic skeleton is particularly preferably an anthracene skeleton, a pyrene skeleton or a phenanthroline skeleton. The electron transport material may be used alone, or 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 preferable electron transporting material is not particularly limited, and specifically, the following examples may be mentioned.

  Although the said electron transport material is used individually, you may mix and use a donor property material. Here, the donor material 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 material include alkali metals, inorganic salts containing alkali metals, complexes of alkali metals and organic substances, alkaline earth metals, inorganic salts containing alkaline earth metals, or alkaline earth metals and organic substances And the like. Preferred types of alkali metals and alkaline earth metals are lithium, sodium, potassium, rubidium, cesium, alkali metals such as magnesium, calcium, cerium, barium, and alkaline earth metals such as magnesium, calcium, cerium, and barium, which have a large effect of improving electron transport ability at low work function Metal is mentioned.

In addition, it is preferable to be in a state of a complex with an inorganic salt or an organic substance rather than a single metal, because vapor deposition in vacuum is easy and handling is excellent. Furthermore, it is more preferable to be in the state of a complex with an organic substance in terms of facilitating the handling in the atmosphere and the ease of control of the concentration to be added. 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 , Carbonates such as Cs ₂ CO _{3 and the} like can be mentioned. Moreover, lithium and cesium are mentioned as a preferable example of an alkali metal or alkaline-earth metal from a viewpoint that a big low voltage drive effect is acquired. Preferred examples of the organic substance in the complex with the organic substance include quinolinol, benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, hydroxytriazole and the like. 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 large, and a complex of lithium and an organic substance is more preferable from the viewpoint of easiness of synthesis Particularly preferred is lithium quinolinol which is commercially available.

The ionization potential of the electron transport 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 the above-mentioned layers constituting the light emitting element is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination method, coating method, etc. Usually, resistance heating evaporation or electron beam evaporation is preferable from the point of element characteristics. preferable.

  In the light emitting element of the present invention, the thickness of the organic layer which is the total of the above layers depends on the resistance value of the light emitting material and can not be limited, but is preferably 1 to 1000 nm. The film thickness of each of the light emitting layer, the electron transporting layer, and the hole transporting layer is 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 element of the present invention has a function capable of converting electrical energy into light. Here, although direct current is mainly used as the electrical energy, it is also possible to use pulse current or alternating current. The current value and the voltage value are not particularly limited, but in consideration of the power consumption and the lifetime of the device, they should be selected so as to obtain the maximum luminance with the lowest possible energy.

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

  In the light emitting element of the present invention, in the matrix type, pixels for display are two-dimensionally arranged in a lattice or mosaic, and a character or an image is displayed by a set of pixels. The shape and size of the pixels depend on the application. For example, for displaying images and characters on personal computers, monitors, and televisions, square pixels with one side of 300 μm or less are usually used, and in the case of a large display such as a display panel, pixels with one side of mm order become. In monochrome display, pixels of the same color may be arranged, but in color display, red, green and blue pixels are displayed side by side. In this case, there are typically delta types and stripe types. And, the method of driving this matrix may be either a line sequential driving method or an active matrix. Although the line sequential drive has a simple structure, the active matrix may be superior in some cases in consideration of the operation characteristics, so it is necessary to use this in accordance with the application.

  In the light emitting element of the present invention, the segment method is a method in which a pattern is formed to display predetermined information, and a region determined by the arrangement of the pattern is made to emit light. Examples include time and temperature displays on digital watches and thermometers, operation state displays on audio devices and induction cookers, and panel displays on automobiles. 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 of various devices. Backlights are mainly used for the purpose of improving the visibility of display devices that do not emit light themselves, and are used for liquid crystal display devices, clocks, audio devices, automobile panels, display boards, signs, and the like. In particular, the light-emitting element of the present invention is preferably used for a liquid crystal display device, particularly a backlight for personal computer applications in which a reduction in thickness is under consideration, and a thin and lightweight backlight can be provided as compared with the conventional one.

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

Example 1
A glass substrate (Geomatech Co., Ltd. product, 11 Ω / □, sputtered product) on which an ITO transparent conductive film was deposited to 50 nm was cut into 38 × 46 mm and etching was performed. The obtained substrate was subjected to ultrasonic cleaning for 15 minutes with “SEMICOCLEAN 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.), and then washed with ultrapure water. The substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the device, placed in a vacuum evaporation apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁴ Pa or less. Then, HI-1 was vapor-deposited 10 nm as a positive hole injection layer by the resistance heating method on the board | substrate. Next, NPD was vapor-deposited 100 nm as a 1st positive hole transport layer. Next, HT-1 was vapor-deposited 20 nm as a 2nd positive hole transport layer. Next, as a light emitting layer, Compound H-1 was used as a host material, Compound D-1 was used as a dopant material, and the doping concentration of the dopant material was 5% by mass to deposit 40 nm thick. Next, Compound E-1 was laminated to a thickness of 20 nm as an electron transport layer.
Subsequently, 0.5 nm of lithium fluoride and 60 nm of aluminum were vapor deposited to form a cathode, and a 5 × 5 mm square element was fabricated. The film thickness referred to here is a crystal oscillation type film thickness monitor display value. When this light emitting element was DC driven at 10 mA / cm ² , green light emission with a luminous efficiency of 25.0 lm / W was obtained. When this light emitting element was continuously driven at 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 compounds shown below.

Examples 2 to 11
A light emitting device was produced in the same manner as in Example 1 except that the second hole transporting layer, the host material, and the materials described in Table 1 were used as 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 compounds shown below.

Comparative Examples 1 to 9
A light emitting device was produced in the same manner as in Example 1 except that the second hole transporting layer and the materials described in Table 1 as a host material were used. The results are shown in Table 1. In addition, HT-7 and H-5-H-7 are the compounds shown below.

Example 12
Using the materials listed in Table 1 as the electron transport material, a vapor deposition film of a compound E-1 and a donor metal (Li: lithium) is deposited at a deposition rate of 100: 1 (= 0.2 nm /) instead of the compound E-1. A light emitting device was produced in the same manner as in Example 1 except that s: 0.002 nm / s) was used. The results are shown in Table 1.

Example 13
The electron transport layer has a two-layer laminated structure, compound E-2 is vapor-deposited to a thickness of 10 nm as a first electron transport layer, and a compound of compound E-1 and a donor metal (Li: lithium) as a second electron transport layer. A light emitting device was produced in the same manner as in Example 1 except that the vapor deposition film was vapor deposited and laminated at a deposition speed ratio of 100: 1 (= 0.2 nm / s: 0.002 nm / s) to a thickness of 25 nm. The results are shown in Table 1. E-2 is a compound shown below.

Example 14
The electron transport layer is a two-layer laminated structure, compound E-2 is vapor-deposited to a thickness of 10 nm as a first electron transport layer, compound E-1 and a donor material (Cs ₂ CO ₃ : carbonic acid as a second electron transport layer) A light-emitting device was manufactured in the same manner as in Example 1, except that a co-evaporated film of cesium was deposited to a thickness of 25 nm at a deposition rate ratio of 100: 1 (= 0.2 nm / s: 0.002 nm / s) Was produced. The results are shown in Table 1.

Example 15
Using the materials listed in Table 1 as the electron transport layer, a vapor deposition film of a compound E-3 and a donor material (Liq: lithium quinolinol) is deposited at a deposition rate of 1: 1 (= 0.05 nm) instead of the compound E-1 A light emitting device was produced in the same manner as in Example 1 except that / s: 0.05 nm / s was used. The results are shown in Table 1. In addition, E-3 is a compound shown below.

Examples 16 to 17
A light emitting device was produced in the same manner as in Example 15 except that the materials described in Table 1 were used as the electron transporting layer. The results are shown in Table 1. In addition, E-4 and E-5 are compounds shown below.

Examples 18 to 19
A light emitting device was produced in the same manner as in Example 1 except that the materials described in Table 1 were used as the electron transporting layer. The results are shown in Table 1.

Example 20
A glass substrate (Geomatech Co., Ltd. product, 11 Ω / □, sputtered product) on which an ITO transparent conductive film was deposited to 50 nm was cut into 38 × 46 mm and etching was performed. The obtained substrate was subjected to ultrasonic cleaning for 15 minutes with “SEMICOCLEAN 56” (trade name, manufactured by Furuuchi Chemical Co., Ltd.), and then washed with ultrapure water. The substrate was subjected to UV-ozone treatment for 1 hour immediately before producing the device, placed in a vacuum evaporation apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁴ Pa or less. Then, 10 nm of compounds HI-1 were vapor-deposited as a positive hole injection layer by the resistance heating method on the board | substrate. Next, NPD was vapor-deposited 100 nm as a 1st positive hole transport layer. Next, HT-1 was vapor-deposited 50 nm as a 2nd positive hole transport layer. Next, as a light emitting layer, compound H-8 was used as a host material, compound D-4 was used as a dopant material, and the doping concentration of the dopant material was 5% by mass to deposit 30 nm thick. Next, Compound E-1 was laminated to a thickness of 35 nm as an electron transport layer.
Subsequently, lithium fluoride was deposited to a thickness of 0.5 nm, and then aluminum was deposited to a thickness of 1000 nm to be used as a cathode. The film thickness said here is a crystal oscillation type film thickness monitor display value. When this light emitting device was DC driven at 10 mA / cm ² , highly efficient red light emission with a luminous efficiency of 14.0 lm / W was obtained. When this light emitting element was continuously driven at a direct current of 10 mA / cm ² , the luminance was reduced by half in 3000 hours. Compound H-8 is a compound shown below.

Examples 21 to 25
A light emitting device was produced and evaluated in the same manner as in Example 20 except that the materials described in Table 2 were used as the second hole transporting layer. The results are shown in Table 2. The compounds HT-8 and HT-9 are compounds shown below.

Comparative Examples 10 to 13
A light emitting device was produced and evaluated in the same manner as in Example 20 except that the second hole transporting layer and the compound described in Table 2 as a host material were used. The results are shown in Table 2. Compounds HT-10 and H-9 are the compounds shown below.

Examples 26-27
A light emitting device was produced and evaluated in the same manner as in Example 20 except that the second hole transporting layer and the materials described in Table 2 as the electron transporting material were used. The results are shown in Table 2.

Examples 28 to 36
A light emitting device was produced and evaluated in the same manner as in Example 20 except that the second hole transporting layer and the compound described in Table 2 as a host material were used. The results are shown in Table 2. Compounds H-10 to H-18 are compounds shown below.

Claims (6)

What is claimed is: 1. A light emitting device comprising at least a hole transport layer and a light emitting layer between an anode and a cathode and emitting light by electrical energy,
The hole transport layer contains a compound represented by the following general formula (1), and the light emitting layer is a compound having an aromatic heterocyclic group containing an electron accepting nitrogen, and the following general formula (2) And the hole transport layer is in direct contact with the light emitting layer, and the compound represented by the general formula (1) is a compound represented by the general formula (2) The compound represented by any one of (4) has an electron blocking property, and the triplet level of the compound represented by the general formula (1) is any of the general formulas (2) to (4) A light emitting device characterized by containing a triplet light emitting material in the light emitting layer higher than a triplet level of a compound represented by か .

(In the general formula (1), R ^{1 to} R ⁴ may be the same or different, and hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, Alkylthio, arylether, arylthioether, aryl, halogen, carbonyl, carboxyl, oxycarbonyl, carbamoyl, amino, silyl, -P (基 O) R ⁵ R ⁶ R ¹ and R ² are different groups R ⁵ and R ⁶ are an aryl group or a heteroaryl group L is a single bond or an arylene group R ^{1 to} R ⁴ and L are substituted The additional substituent, if any, is an alkyl group or an aryl group.

In the general formulas (2) to (4), R ^{7 to} R ¹¹ and R ^{21 to} R ²⁷ may be the same as or different from each other, and hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, cyclo Alkenyl, alkynyl, alkoxy, alkylthio, arylether, arylthioether, aryl, heteroaryl, halogen, carbonyl, carboxyl, oxycarbonyl, carbamoyl, amino or silyl . In addition, R ^{7 to} R ¹¹ may form a ring with adjacent substituents. However, 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 is there. Ring A or ring B represents a substituted or unsubstituted benzene ring which is fused at any position with the 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 represents an alkyl group, an aryl group or a heteroaryl group. R ^{21 to} R ³⁰ may form a ring with adjacent substituents. L ^{11 to} L ¹⁷ are a single bond or an arylene group. X ¹ to X ⁵ represents a carbon atom or a nitrogen ^atom, when X 1 to X ⁵ is a nitrogen atom, ^R 7 ^{to R 11} is a substituent on the nitrogen atom is not present. However, the number of nitrogen atoms in X ^{1 to} X ⁵ is 1 or 2. ) The light emitting device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (5).

(In Formula (5), R ^{1 to} R ⁴ are the same as above.) The light emitting device according to claim 1 or 2, wherein in the general formula (1), both R ¹ and R ² are a substituted or non-substituted aryl group. In the above general formula (1), R ¹ is a phenyl group having no substituent, and R ² is a diphenylphenyl group, a triphenylphenyl group, a tetraphenylphenyl group or a pentaphenylphenyl group. The light-emitting device according to any one of Items 1 to 3. The compound according to any one of claims 1 to 4, wherein in the general formulas (2) to (4), X ¹ and X ⁵ , or X ³ and X ⁵ , or X ¹ and X ³ are nitrogen atoms. The light emitting device as described in 1).   At least an electron transport layer is provided between the anode and the cathode, and the electron transport layer is a hetero compound composed of an electron accepting nitrogen, and an element selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus. The light emitting device according to any one of claims 1 to 5, comprising a compound having an aryl ring structure.