JP2011009517A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which is fabricated through a low-cost wet process, and superior in light emission luminance, driving voltage and voltage rise rate.SOLUTION: The organic electroluminescent element has a light-emitting layer containing a light emission host and a light emission dopant, as a constituent layer between an anode and a cathode, and is characterized in that the light-emitting layer is formed through the wet process and an average concentration of the light emission dopant within a range of 0 to 5 nm from an interface between the light-emitting layer and at least one light-emitting layer adjoining the light-emitting layer is ≥50% of an average concentration of the whole light emission dopant contained in the light-emitting layer.

Description

  The present invention relates to an organic electroluminescence element.

  As a light-emitting electronic device, there is an electroluminescence element (hereinafter abbreviated as “ELD” as appropriate). As a component of ELD, an inorganic electroluminescence element (hereinafter also referred to as “inorganic EL element”) and an organic electroluminescence element (hereinafter also referred to as “organic EL element”) can be given. Inorganic EL elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements.

  On the other hand, an organic electroluminescence device has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and excitons (excitons) by injecting electrons and holes into the light emitting layer and recombining them. Is a device that emits light by using light emission (fluorescence / phosphorescence) when this exciton is deactivated, and can emit light at a voltage of several V to several tens of V, and further self-emission. Since it is a type, it has a wide viewing angle, high visibility, and since it is a thin-film type completely solid element, it has attracted attention from the viewpoints of space saving, portability, and the like.

  However, in organic EL elements for practical use in the future, development of organic EL elements with higher driving luminance at a lower driving voltage is desired.

  Another major feature of the organic electroluminescence element is that it is a surface light source, unlike main light sources that have been put to practical use, such as light-emitting diodes and cold-cathode tubes. Applications that can effectively utilize this characteristic include illumination light sources and various display backlights. In particular, it is also suitable to be used as a backlight of a liquid crystal full color display whose demand has been increasing in recent years.

  A further improvement in light emission luminance can be cited as a problem for putting the organic electroluminescence element into practical use as such an illumination light source or a display backlight. For that purpose, it is becoming common to incorporate a so-called light-emitting host and light-emitting dopant, which are formed by mixing a plurality of materials each having a different function, in a part of the organic functional layer constituting the organic electroluminescence element.

  As a means for further improving the performance, a method for producing a light emitting layer in which the distribution of the dopant material in the light emitting layer is devised has been developed. An invention has been disclosed in which the dopant concentration on the hole transport layer side in the light emitting layer is increased to reduce luminance deterioration during continuous driving (see, for example, Patent Document 1).

  However, what is clearly stated as means for continuously changing the concentration of the luminescent dopant is only the control of the deposition rate in the vacuum deposition method, and cannot be said to be a proposal of means suitable for productivity.

  As a method for producing an organic electroluminescence element, there are a vacuum deposition method, a wet process (coating method) and the like. However, a vacuum process is not required, continuous production is simple, and the production rate can be increased in recent years. The manufacturing method in the process (spin coating method, casting method, ink jet method, spray method, printing method, slot type coater method, etc.) is attracting attention, and a device for producing a light emitting layer having a light emitting host and a light emitting dopant by a wet process. However, an organic EL element produced by a wet process generally does not exhibit sufficient performance stability, particularly in terms of light emission luminance, as compared with a vapor deposition type element. Known to.

Japanese Patent Laid-Open No. 2004-6102 JP 2008-112875 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic electroluminescence element that can be manufactured by a low-cost wet process and has excellent emission luminance, driving voltage, and voltage increase rate. is there.

  The above-mentioned problem according to the present invention is solved by the following means.

  1. An organic electroluminescent device having a light emitting layer containing a light emitting host and a light emitting dopant as a constituent layer between an anode and a cathode, wherein the light emitting layer is formed by a wet process and adjacent to the light emitting layer of the light emitting layer The average concentration of the light emitting dopant in the range of 0 to 5 nm from the interface with at least one adjacent layer is 50% or more with respect to the average concentration of all the light emitting dopants contained in the light emitting layer. Luminescence element.

  2. 2. The organic electroluminescence device according to 1 above, wherein a range having an average concentration of 50% or more with respect to an average concentration of all light-emitting dopants contained in the light-emitting layer is 0 to 10 nm.

  3. 3. The range according to 1 or 2 above, wherein a range having an average concentration of 50% or more with respect to an average concentration of all light-emitting dopants contained in the light emitting layer is present on a side close to the anode in the light emitting layer. Organic electroluminescence device.

  4). 4. The organic electroluminescent element according to any one of 1 to 3, wherein the light emitting host has a molecular weight of 1500 or less.

  5. 5. The organic electroluminescent element according to any one of 1 to 4, wherein the light-emitting host has at least three or more partial structures represented by the following general formula (a) in a molecule.

(In the formula, X represents NR ′, O, S, CR′R ″ or SiR′R ″. R ′ and R ″ each represents a hydrogen atom or a substituent. Ar is necessary for forming an aromatic ring. N represents an integer of 0 to 8.)
6). One of the said adjacent layers is an electron carrying layer, The organic electroluminescent element of any one of said 1-5 characterized by the above-mentioned.

  7. One of the said adjacent layers is a positive hole transport layer, The organic electroluminescent element of any one of said 1-5 characterized by the above-mentioned.

  8). 8. The organic electroluminescence device according to any one of 1 to 7, wherein the light emitting dopant exhibits phosphorescence.

  9. 9. The organic electroluminescence device according to any one of 1 to 8, wherein the light-emitting dopant is an organometallic complex represented by the following general formula (1).

(In the formula, Z represents a hydrocarbon ring group, an aromatic heterocyclic group or a heterocyclic group. R _{81 to} R ₈₆ represent a hydrogen atom or a substituent. P ₁ -L ₁ -P ₂ is a bidentate coordination. P ₁ and P ₂ each independently represents a carbon atom, a nitrogen atom or an oxygen atom, L 1 represents an atomic group which forms a bidentate ligand together with P ₁ and P ₂ , j 1 is 1 to 1 represents the integer 3, j2 is an integer of 0 to 2, j1 + j2 is 2 or 3 .M ₁ represents a metal element of group 8 to group 10 in the periodic table.)
10. 10. The organic electroluminescence device as described in 9 above, wherein M _{1 in the} general formula (1) is iridium.

  According to the present invention, it is possible to provide an organic electroluminescence element that can be manufactured by a low-cost wet process and has excellent emission luminance, driving voltage, and voltage increase rate.

  The above-described effects of the present invention are related to the concentration of the light-emitting dopant in the light-emitting layer. In the vicinity of the interface between the light emitting layer and the adjacent layer, if there is a range of less than 50% with respect to the average concentration of all the light emitting dopants contained in the light emitting layer, carrier injection from the adjacent layer is hindered, and organic EL As a result of our intensive studies, it became clear that the light emission luminance of the device decreases. Although it is not clear why such a low emission dopant concentration range can be formed in the vicinity of the light emitting layer interface, when forming a light emitting layer by a wet process, the solubility and volatility of the solvent used in the wet process and the light emitting layer It is thought that the film forming method is related.

  As described in the present invention, the inventors set the average concentration of the luminescent dopant in the vicinity of the interface with the adjacent layer to 50% or more with respect to the average concentration of all the luminescent dopants contained in the luminescent layer. In particular, the present inventors have found that an organic EL element in which a decrease in emission luminance is suppressed can be obtained except for factors that hinder carrier injection.

The figure which shows an example of the organic EL element of this invention

  In the organic electroluminescent element of this invention, by having the structure of any one of Claims 1-10, it can produce with a low-cost wet process and obtains an organic electroluminescent element with high light-emitting luminance. I was able to.

  Hereinafter, details of each component according to the present invention will be sequentially described.

  In the present invention, a light emitting layer is formed by a film forming process using a wet process, and the average concentration of the light emitting dopant in the range of 0 to 5 nm from the interface with at least one adjacent layer of the light emitting layer is included in the light emitting layer. It was possible to provide an organic electroluminescence device having a concentration of 50% or more with respect to the average concentration of all luminescent dopants.

  In the present invention, the “light-emitting layer containing a light-emitting host and a light-emitting dopant” refers to a light-emitting layer containing a light-emitting host and a light-emitting dopant as a compound that contributes to light emission.

  As an embodiment of the present invention, from the viewpoint of the effect of the present invention, the average concentration of the luminescent dopant in the range of 0 to 10 nm from the interface with the adjacent layer is 50% or more with respect to the average concentration of all the luminescent dopants. Preferably, a range having an average concentration of 50% or more with respect to the average concentration of all light-emitting dopants is present on the side close to the anode in the light emitting layer. Moreover, it is preferable that the molecular weight of the light emission host of the said light emitting layer is 1500 or less, and it is still more preferable that the light emission dopant of the said light emitting layer is a phosphorescence dopant.

  In the present invention, the adjacent layer is preferably a hole transport layer, and the adjacent layer is preferably an electron transport layer.

  Hereinafter, the present invention, its components, and modes for carrying out the invention will be described in detail.

  The range which is an average concentration of 50% or more with respect to the average concentration of all luminescent dopants in the present invention will be described.

  The range having an average concentration of 50% or more with respect to the average concentration of all luminescent dopants in the present invention is the average concentration of luminescent dopants of 50% or more with respect to the average concentration of all luminescent dopants contained in the light emitting layer. It refers to a certain range and includes that all are luminescent dopants. In this invention, although the said range is 0-5 nm from the interface with an adjacent layer, It is preferably 0-10 nm. Even if the range which is an average concentration of 50% or more with respect to the average concentration of all luminescent dopants contained in the light emitting layer exists on both sides of the light emitting layer near the anode and near the cathode, May be present only. When it exists only on one side, it is preferable to exist on the side close to the anode.

  The formation method of the range which is an average density | concentration of 50% or more with respect to the average density | concentration of all the luminescent dopants in this invention is demonstrated.

  As a method for forming a range having an average concentration of 50% or more with respect to the average concentration of all the light-emitting dopants in the vicinity of the interface with the adjacent layer, for example, a method of drying the solvent at a high speed during coating film formation of the light-emitting layer. is there. Examples of means for drying the solvent at high speed include using a solvent having a high vapor pressure and drying the solvent by blowing air. The solvent having a high vapor pressure is a solvent having a vapor pressure of 1.0 kPa or more at 20 ° C. Examples of such a solvent include toluene (20 ° C. vapor pressure: 2.9 kPa), ethyl acetate (20 ° C. vapor). Pressure: 2.9 kPa), isopropyl acetate (20 ° C. vapor pressure: 5.3 kPa), normal propyl acetate (20 ° C. vapor pressure: 3.3 kPa), and methyl ethyl ketone (20 ° C. vapor pressure: 10.5 kPa). Drying the solvent by blowing is to blow and blow immediately after applying the light emitting layer, and depends on the characteristics and material purity of the light emitting host or dopant used, or the characteristics of the solvent used. In general, it cannot be specified. However, as long as the air temperature and the air speed do not affect the formation of the light emitting layer according to the present invention, the larger the air temperature and the air speed, the faster the drying speed and the faster drying.

  A measurement method in the range of an average concentration of 50% or more with respect to the average concentration of all light-emitting dopants contained in the light emitting layer in the present invention will be described.

  There are several methods for measuring the concentration range of 50% or more of the average concentration of all light-emitting dopants contained in the light-emitting layer, but the amount of elements in the film can be analyzed with high sensitivity. In addition, it is preferable to use secondary ion mass spectrometry (SIMS) because the concentration change of the element in the depth direction can be followed. As for secondary ion mass spectrometry, for example, Japanese Society for Surface Science “Secondary ion mass spectrometry (Surface Science and Technology Selection)” (Maruzen) can be referred to.

In the secondary ion mass spectrometry, a sample surface is irradiated with an ion beam called primary ions under a high vacuum of about 10 ⁻⁸ Pa to perform sputtering. This is a method of analyzing elements present on the surface by mass spectrometry of secondary ions in the constituent particles released thereby. Although the surface is sputtered and scraped off, it is possible to analyze the change in element concentration from the surface to a depth of μm or more, although it is a destructive analysis.

As the primary ions, for example, metal ion species such as Cs ⁺ , In ⁺ , and Ga ⁺ are preferable. Which ion species is preferably used depends on the element to be measured.

In the present invention, specifically, ADEPT 1010 manufactured by Physical Electronics is used, the primary ion species is Cs ⁺ , and the acceleration voltage of the primary ions is 2 kV. The distribution amounts of various elements in the depth direction in the organic EL element Was measured.

  The adjacent layer in this invention is demonstrated.

  In the present invention, the adjacent layer is a layer having a function different from that of the light emitting layer adjacent to the light emitting layer containing the light emitting host and the light emitting dopant, and the adjacent layer is formed between the anode and the light emitting layer. It may be between. There is no particular limitation on the adjacent layer, for example, an anode buffer layer, a cathode buffer layer, a hole blocking layer, an electron blocking layer, a hole transporting layer, an electron transporting layer, and an intermediate layer, which can move carriers to the light emitting layer. In order to facilitate, the adjacent layer is preferably an electron transport layer or a hole transport layer.

<< Layer structure of organic EL element >>
The layer structure of the organic EL element of the present invention will be described.

  The constituent layers of the organic EL device of the present invention include, for example, an anode buffer layer, a cathode buffer layer, a hole blocking layer, an electron blocking layer, a hole transport layer, an electron transport layer, an intermediate layer, and a light emitting layer. Specific examples of preferred layer structures using these layers are shown below, but the present invention is not limited thereto.

(I) Anode / light emitting layer / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer / hole blocking layer / electron Transport layer / cathode (iv) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) Anode / anode buffer layer / hole transport layer / light emitting layer / electron transport Layer / cathode buffer layer / cathode (vi) anode / anode buffer layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (vii) anode / anode buffer layer / hole transport Layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode.

<Light emitting layer>
The light emitting layer in the present invention will be described.

  The light emitting layer is a layer that emits light by recombination of injected electrons and holes, and the light emitting part may be in the layer of the light emitting layer or at the interface between the light emitting layer and the adjacent layer. However, since the deactivation of excitons between layers can be considered, it is preferably within the light emitting layer.

  The configuration of the light emitting layer according to the present invention is not particularly limited as long as it satisfies the requirements defined in the present invention.

  The thickness of the light emitting layer is not particularly limited, but from the viewpoint of improving the uniformity of the film to be formed and applying an unnecessary high voltage during light emission, and improving the stability of the emission color with respect to the driving current. It is preferable to adjust to a range of 200 nm, and more preferably to a range of 5 to 100 nm.

  The light-emitting layer of the organic EL device of the present invention is characterized by containing a light-emitting host and at least one light-emitting dopant, and the range of 0 to 5 nm from the interface between the light-emitting layer and the adjacent layer is light emission. It is characterized by an average concentration of 50% or more with respect to the average concentration of all luminescent dopants contained in the layer.

  When the light emitting layer according to the present invention was formed, it was possible to suppress a decrease in light emission luminance and an increase in driving voltage. Although the reason is not clear, there is a factor that hinders carrier injection by setting the vicinity of the interface with the adjacent layer to an average concentration of 50% or more with respect to the average concentration of all light-emitting dopants contained in the light-emitting layer. It is estimated that the decrease in the light emission luminance and the increase in the drive voltage are suppressed, and the drive at the low voltage is possible.

  In the present invention, the light emitting layer has a light emitting host and a light emitting dopant. Thereby, the light emission luminance, the external extraction quantum efficiency, and the like can be improved, and the performance can be improved.

  Hereinafter, the light emitting host and the light emitting dopant contained in the light emitting layer will be described.

(Light emitting host)
The light emitting host is a compound having a phosphorescence quantum yield of phosphorescence emission of less than 0.1 at room temperature (25 ° C.) among compounds contained in the light emitting layer. The phosphorescence quantum yield is preferably less than 0.01. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer.

  As the light emitting host, a known light emitting host may be used alone or in combination of two or more kinds. By using a plurality of types of light-emitting hosts, the movement of charges can be adjusted, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of light emission dopants mentioned later, and, thereby, arbitrary luminescent colors can be obtained.

  As a known light-emitting host that may be used in combination, a compound conventionally used in an organic EL device can be used, but it has a hole-transporting ability and an electron-transporting ability, and prevents emission of longer wavelengths. A compound having a high Tg (glass transition temperature) is preferred. The light emitting host used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (polymerizable light emission). Host), but preferably a light emitting host having a molecular weight of 1500 or less.

  Specific examples of the light emitting host preferably used in the present invention are shown below, but the present invention is not limited thereto.

  Specific examples of known luminescent hosts other than those described above include compounds described in the following documents.

  JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445 gazette, 2002-343568 gazette, 2002-141173 gazette, 2002-352957 gazette, 2002-203683 gazette, 2002-363227 gazette, 2002-231453 gazette, No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060, No. 2002. -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

  Among them, the light emitting host according to the present invention is preferably a light emitting host having at least three partial structures represented by the general formula (a). Three or more connections may be connected at the X portion or at other portions.

  Among these, as the luminescent host according to the present invention, a luminescent host having at least three partial structures represented by the general formula (a) is preferable. Three or more connections may be connected at the X portion or at other portions.

<Partial structure represented by general formula (a)>
The partial structure represented by the general formula (a) of the present invention will be described.

  In the partial structure X represented by the general formula (a), the substituents represented by R ′ and R ″ may be alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group). Group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group), alkenyl group (for example, vinyl group, allyl group), alkynyl Group (for example, ethynyl group, propargyl group), aromatic hydrocarbon ring group (also called aromatic carbocyclic group, aryl group, etc., for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group) Group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyreth Group, biphenylyl group), aromatic heterocyclic group (for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4- Triazol-1-yl group, 1,2,3-triazol-1-yl group), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl group, quinolyl group, benzofuryl group Dibenzofuryl group, benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (one in which one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom) Quinoxalinyl group, pyridazinyl group, Azinyl group, quinazolinyl group, phthalazinyl group), heterocyclic group (for example, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group) Group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group), aryloxy group (for example, phenoxy group, naphthyloxy group), alkylthio group (for example, methylthio group, ethylthio group) Group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group), cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group), arylthio group (for example, phenylthio group, naphthyl) Thio group), alkoxycarbonyl group (for example, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group), aryloxycarbonyl group (for example, phenyloxycarbonyl group, naphthyloxy) Carbonyl group), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylamino) Sulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group), acyl group (for example, acetyl group, ethylcarbonyl group, propyl group) Bonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group) Group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonyl) Amino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group Phenylcarbonylamino group, naphthylcarbonylamino group), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, Octylureido group, dodecylureido group, phenylureido group naphthylureido group, 2-pyridylaminoureido group), sulfinyl group (for example, Methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group), alkylsulfonyl group (for example, methylsulfonyl group) , Ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group), arylsulfonyl group or heteroarylsulfonyl group (for example, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group), Amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group) , Dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group), halogen atom (for example, fluorine atom, chlorine atom, bromine atom), fluorinated hydrocarbon group (for example, fluoromethyl group, trifluoromethyl group, Pentafluoroethyl group, pentafluorophenyl group), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group). These substituents may be further substituted with the above substituents. A plurality of these substituents may be bonded to each other to form a ring.

  Among these, X is preferably NR ′ or O, and R ′ is an aromatic hydrocarbon group (also called an aromatic carbocyclic group or aryl group, such as phenyl group, p-chlorophenyl group, mesityl group, tolyl group). Group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group) or aromatic heterocyclic group (for example, furyl group, thienyl group, pyridyl group) , Pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolinyl group, phthalazinyl group and the like are particularly preferable.

  The above aromatic hydrocarbon group and aromatic heterocyclic group each may have a substituent represented by R ′ or R ″ in X of the partial structure represented by the general formula (a).

  In the partial structure represented by the general formula (a), examples of the aromatic ring represented by Ar include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The aromatic ring may be a single ring or a condensed ring, and may be unsubstituted, or may have a substituent represented by each of R ′ and R ″ in X of the partial structure represented by the general formula (a). May be.

  In the partial structure represented by the general formula (a), the aromatic hydrocarbon ring represented by Ar includes a benzene ring, a biphenyl ring, a naphthalene ring, an azulene ring, an anthracene ring, a phenanthrene ring, a pyrene ring, a chrysene ring, Naphthacene ring, triphenylene ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaphthene ring, coronene ring, fluorene ring, fluoranthrene ring, naphthacene ring, pentacene ring, perylene ring, pentaphen ring, Examples include a picene ring, a pyrene ring, a pyranthrene ring, and an anthraanthrene ring. These rings may further have substituents each represented by R ′ and R ″ in X of the partial structure represented by the general formula (a).

  In the partial structure represented by the general formula (a), examples of the aromatic heterocycle represented by Ar include a furan ring, a dibenzofuran ring, a thiophene ring, an oxazole ring, a pyrrole ring, a pyridine ring, a pyridazine ring, and a pyrimidine ring. , Pyrazine ring, triazine ring, benzimidazole ring, oxadiazole ring, triazole ring, imidazole ring, pyrazole ring, thiazole ring, indole ring, indazole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline Ring, cinnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, naphthyridine ring, carbazole ring, carboline ring, diazacarbazole ring (one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom) Etc.) It is below.

  These rings may further have substituents represented by R ′ and R ″ in X of the partial structure represented by the general formula (a).

  Among the above, in the general formula (a), the aromatic ring represented by Ar is preferably a carbazole ring, a carboline ring, a dibenzofuran ring, or a benzene ring, and more preferably a carbazole ring, A carboline ring and a benzene ring, more preferably a benzene ring having a substituent, and particularly preferably a benzene ring having a carbazolyl group.

  In the general formula (a), the aromatic ring represented by Ar is preferably a condensed ring having 3 or more rings, and the aromatic hydrocarbon condensed ring in which 3 or more rings are condensed is a specific example. Naphthacene ring, anthracene ring, tetracene ring, pentacene ring, hexacene ring, phenanthrene ring, pyrene ring, benzopyrene ring, benzoazulene ring, chrysene ring, benzochrysene ring, acenaphthene ring, acenaphthylene ring, triphenylene ring, coronene ring, benzocoronene Ring, hexabenzocoronene ring, fluorene ring, benzofluorene ring, fluoranthene ring, perylene ring, naphthperylene ring, pentabenzoperylene ring, benzoperylene ring, pentaphen ring, picene ring, pyrantolen ring, coronene ring, naphthocoronene ring, ovalen ring, Anthracanthrene ring, etc. And the like.

  In addition, these rings may further have the above substituent.

  Specific examples of the aromatic heterocycle condensed with three or more rings include an acridine ring, a benzoquinoline ring, a carbazole ring, a carboline ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, a carboline ring, a cyclazine ring, Kindin ring, tepenidine ring, quinindrin ring, triphenodithiazine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, diazacarbazole ring (any one of the carbon atoms constituting the carboline ring is a nitrogen atom Phenanthroline ring, dibenzofuran ring, dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, benzodifuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, A Tiger thiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, such as thio fan Tren ring (naphthaldehyde thiophene ring), and the like. In addition, these rings may further have a substituent.

  In the general formula (a), n represents an integer of 0 to 8, preferably 0 to 2, particularly preferably 1 to 2 when X is O or S.

<Light emitting host represented by general formula (a-1), (a-2) or (a-3)>
The light-emitting host according to the present invention has at least three partial structures represented by the above general formula (a). Preferred embodiments include the following general formula (a-1), (a-2) or (a The compound represented by -3) is preferable.

  In the formula, Ar ′ and Ar ″ represent an aromatic ring, and the aromatic ring has the same meaning as the aromatic ring represented by Ar in the general formula (a). N represents an integer of 1 or more, and m represents 0 or more. Represents an integer.

(Luminescent dopant)
As the light-emitting dopant according to the present invention, a fluorescent dopant or a phosphorescent dopant can be used. From the viewpoint of obtaining an organic EL element having higher emission luminance, light emission used in the light-emitting layer or light-emitting unit of the organic EL element. As a dopant, it is preferable to contain a phosphorescence dopant simultaneously with containing said light emission host.

  Representative examples of fluorescent dopants include compounds with high fluorescence quantum yields such as laser dyes, coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, and fluorescein. And dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes, polythiophene dyes, rare earth complex phosphors, and the like.

  The phosphorescent dopant is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescence at room temperature (25 ° C.), and a phosphorescence quantum yield of 0.01 at 25 ° C. Although it is the above compound, a preferable phosphorescence quantum yield is 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

  The phosphorescent dopant can be appropriately selected from known materials used for the light emitting layer of the organic EL device.

  The phosphorescent dopant according to the present invention is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, a europium complex, or a platinum compound (platinum complex system). Compound) and rare earth complexes, and most preferred is an iridium compound.

  The phosphorescent dopant according to the present invention is more preferably an organometallic complex represented by the general formula (1). In addition, specific examples include compounds described in the following patent publications.

  WO 00/70655 pamphlet, JP 2002-280178, JP 2001-181616, JP 2002-280179, JP 2001-181617, JP 2002-280180, JP 2001-247859, JP 2002-299060, JP 2001-313178, JP 2002-302671, JP 2001-345183, JP 2002-324679, International Publication No. 02/15645 pamphlet, JP 2002-332291 A, JP 2002-50484 A, JP 2002-332292 A, JP 2002-83684 A, JP 2002-540572 A, JP 2002-2002 A. No. 117978, JP 20 JP-A-2-338588, JP-A-2002-170684, JP-A-2002-352960, WO01 / 93642, JP-A-2002-50483, JP-A-2002-1000047, JP-A-2002. No. -173744, JP-A No. 2002-359082, JP-A No. 2002-17584, JP-A No. 2002-363552, JP-A No. 2002-184582, JP-A No. 2003-7469, JP-T-2002-525808. Gazette, JP2003-7471, JP2002-525833, JP2003-31366, JP2002-226495, JP2002-234894, JP2002-2335076 JP 2002-241751 A JP 2001-319779, JP 2001-319780, JP 2002-62824, JP 2002-1000047, JP 2002-203679, JP 2002-343572, JP 2002-203678 gazette etc.

  Although the specific example of the compound used as a phosphorescence dopant below is shown, this invention is not limited to these. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like.

  In particular, when a phosphorescent dopant is used in the organic EL device of the present invention, the triplet energy of the host is preferably larger than the triplet energy of the dopant. Thereby, brightness | luminance and external extraction efficiency can be made high, and quality can be improved more.

  As the phosphorescent dopant according to the present invention, an organometallic complex represented by the general formula (1) is preferably used.

<< Organic metal complex represented by the general formula (1) >>
In the organometallic complex represented by the general formula (1), examples of the bidentate ligand represented by P ₁ -L ₁ -P ₂ include substituted or unsubstituted phenyl pyridine, phenyl pyrazole, and phenyl imidazole. , Phenyltriazole, phenyltetrazole, pyrazabole, acetylacetone, picolinic acid and the like.

As M ₁ , a transition metal element belonging to Group 8 to 10 in the periodic table of elements is used, among which iridium and platinum are preferable, and iridium is particularly preferable.

  Examples of the hydrocarbon ring group represented by Z include a non-aromatic hydrocarbon ring group and an aromatic hydrocarbon ring group. Examples of the non-aromatic hydrocarbon ring group include a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group. And may be substituted or unsubstituted.

  Examples of the aromatic hydrocarbon ring group (also referred to as aromatic hydrocarbon group, aryl group, etc.) include, for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl. Group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group and the like. These groups may be substituted or unsubstituted.

In the organometallic complex represented by the general formula (1), R _{81 to} R ₈₆ each represent a hydrogen atom or a substituent. Examples of the substituent include the partial structure represented by the general formula (a) described above. X is the same as the substituents represented by R ′ and R ″.

  Further, these substituents may be further substituted with substituents represented by R ′ and R ″ in X of the partial structure represented by the general formula (a) described above. A plurality of groups may be bonded to each other to form a ring.

<< Injection layer: electron injection layer, hole injection layer >>
The injection layer is provided as necessary, and there are a hole injection layer and an electron injection layer, and as described above, exists between the anode and the light emitting layer or the hole transport layer, and between the cathode and the light emitting layer or the electron transport layer. You may let them.

  An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2) Chapter 2 “Electrode Materials” (pages 123 to 166) in detail, and includes an anode buffer layer (hole injection layer) and a cathode buffer layer (electron injection layer).

  The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.

  The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. . The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258 and 11-204359, and “Organic EL elements and their forefront of industrialization” (issued on November 30, 1998 by NTS Corporation). There is a hole blocking (hole blocking) layer.

  The hole blocking layer has the function of an electron transport layer in a broad sense, and is made of a material that has a function of transporting electrons but has a very small ability to transport holes, and blocks holes while transporting electrons. Thus, the probability of recombination of electrons and holes can be improved. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

  On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material that has a function of transporting holes and has an extremely small ability to transport electrons, and transports electrons while transporting holes. By blocking, the recombination probability of electrons and holes can be improved. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The film thickness of the hole blocking layer and the electron transporting layer according to the present invention is preferably 3 to 100 nm, and more preferably 5 to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes. In a broad sense, the hole injection layer and the electron blocking layer also have a function of a hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

  The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

  Although the above-mentioned thing can be used as a positive hole transport material, It is preferable to use a porphyrin compound, an aromatic tertiary amine compound, and a styryl amine compound, especially an aromatic tertiary amine compound.

  Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N'- Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane '; 1,1- Bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p- Tolylaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N′-diphenyl-N, N ′ Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino -(2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and also two described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 are linked in a starburst type ( MTDATA) and the like.

  Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material.

  JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material as described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, these materials are preferably used because a light-emitting element with higher efficiency can be obtained.

  The hole transport layer is formed by a known method such as a vacuum deposition method, a wet process (spin coating method, cast method, ink jet method, spray method, printing method, slot type coater method, etc.) It can be formed by thinning. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

  Alternatively, a hole transport layer having a high p property doped with impurities can be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

  In the present invention, it is preferable to use a hole transport layer having such a high p property because a device with lower power consumption can be produced. In the present invention, the hole transport layer is preferably provided as an adjacent layer of the light emitting layer.

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons. In a broad sense, the electron injection layer and the hole blocking layer also have a function of an electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  Conventionally, in the case of a single electron transport layer and a plurality of layers, an electron transport material (also serving as a hole blocking material) used for an electron transport layer adjacent to the light emitting layer on the cathode side is injected from the cathode. As long as it has a function of transferring electrons to the light-emitting layer, any material can be selected and used from among conventionally known compounds. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives Thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

  In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material.

  In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting material.

  The electron transport layer is formed by thinning the electron transport material by a known method such as a vacuum deposition method, a wet process (spin coating method, casting method, ink jet method, spray method, printing method, slot type coater method, etc.). Can be formed. Although there is no restriction | limiting in particular about the film thickness of an electron carrying layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials. In the present invention, the electron transport layer is preferably provided as an adjacent layer of the light emitting layer.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used.

  For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
As the cathode, a material having a work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering.

  The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.

  Moreover, after producing the said metal with a film thickness of 1-20 nm on a cathode, a transparent or semi-transparent cathode can be produced by producing the electroconductive transparent material quoted by description of the anode on it, By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

"substrate"
There are no particular limitations on the type of glass, plastic, etc., which can be used in the organic EL device according to the present invention (hereinafter also referred to as a substrate, substrate, support substrate, etc.), and even if it is transparent It may be. When extracting light from the substrate side, the substrate is preferably transparent. Examples of the transparent substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable substrate is a resin film capable of giving flexibility to the organic EL element.

  Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones Polyetherimide, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, and cycloolefin resins such as ARTON (manufactured by JSR) or APEL (manufactured by Mitsui Chemicals).

On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both may be formed. Water vapor permeability measured by a method in accordance with JIS K 7129-1992 (25 ± 0.5 ° C., It is preferably a barrier film having a relative humidity (90 ± 2)% RH) of 0.01 g / (m ² · 24 h) or less, and further, oxygen permeation measured by a method according to JIS K 7126-1987. The film is preferably a high barrier film having a degree of 10 ⁻³ ml / (m ² · 24 h · MPa) or less and a water vapor permeability of 10 ⁻⁵ g / (m ² · 24 h) or less.

  As a material for forming the barrier film, any material may be used as long as it has a function of suppressing entry of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

  The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

  Examples of the opaque substrate include a metal plate such as aluminum and stainless steel, a film, an opaque resin substrate, a ceramic substrate, and the like.

  The external extraction quantum efficiency at room temperature of light emission of the organic EL device according to the present invention is preferably 1% or more, more preferably 5% or more.

  Here, external extraction quantum efficiency (%) = (number of photons emitted to the outside of the organic EL element) / (number of electrons passed through the organic EL element) × 100.

  In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor. In the case of using a color conversion filter, the λmax of light emission of the organic EL element is preferably 480 nm or less.

<Sealing>
As a sealing means of the organic EL element used for this invention, the method of adhere | attaching a sealing member, an electrode, and a support substrate with an adhesive agent can be mentioned, for example.

  The sealing member may be disposed so as to cover the display area of the organic EL element, and may be a concave plate shape or a flat plate shape. Further, transparency and electrical insulation are not particularly limited.

  Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned. Furthermore, the polymer film has an oxygen permeability of 1 × 10 ⁻³ ml / (m ² · 24 h · MPa) or less measured by a method according to JIS K 7126-1987, and a method according to JIS K 7129-1992. It is preferable that the water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured in (1) is 1 × 10 ⁻³ g / (m ² · 24 h) or less.

  For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used.

  Specific examples of adhesives include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. Can be mentioned. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.

  In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature to 80 degreeC is preferable. A desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print like screen printing.

  In addition, it is also preferable that the sealing layer is formed by coating the organic layer with the electrode on the outer side of the electrode facing the substrate with the organic layer interposed therebetween, and forming an inorganic or organic layer in contact with the substrate. In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can.

  Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. The method for forming these films is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

  In the gap between the sealing member and the display area of the organic EL element, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil can be injected in the gas phase and liquid phase. preferable. A vacuum is also possible. Moreover, a hygroscopic compound can also be enclosed inside.

  Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide), sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Metal halides (eg, calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide), perchloric acids (eg, barium perchlorate, Magnesium chlorate), and anhydrous salts are preferably used in sulfates, metal halides and perchloric acids.

《Protective film, protective plate》
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided on the outer side of the sealing film on the side facing the support substrate with the organic layer interposed therebetween or on the sealing film. In particular, when the sealing is performed by the sealing film, the mechanical strength is not necessarily high. Therefore, it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. used for the sealing can be used. It is preferable to use a film.

《Light extraction》
The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1), and only 15% to 20% of light generated in the light emitting layer can be extracted. It is generally known that there is no. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because the light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the element side surface.

  As a method of improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate and preventing total reflection at the transparent substrate and the air interface (US Pat. No. 4,774,435), A method of improving efficiency by providing a light collecting property to a substrate (Japanese Patent Laid-Open No. 63-314795), a method of forming a reflective surface on a side surface of an element (Japanese Patent Laid-Open No. 1-220394), and light emission from a substrate A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the bodies (Japanese Patent Laid-Open No. 62-172691), a flat having a lower refractive index between the substrate and the light emitter than the substrate A method of introducing a layer (Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of a substrate, a transparent electrode layer and a light emitting layer (including between the substrate and the outside) (Japanese Patent Laid-Open No. 11-283951) Gazette).

  In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitting layer, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.

  In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

  When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower.

  Examples of the medium as the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Further, it is preferably 1.35 or less.

  The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave that has exuded by evanescent enters the substrate.

  The method of introducing a diffraction grating into an interface or any medium that causes total reflection is characterized by a high effect of improving light extraction efficiency. This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction such as first-order diffraction and second-order diffraction. Light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating in any layer or medium (in a transparent substrate or transparent electrode), and the light is removed. I want to take it out.

  The introduced diffraction grating desirably has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. Therefore, the light extraction efficiency does not increase so much. However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.

  As described above, the position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or in the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated. At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium.

  The arrangement of the diffraction grating is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

《Condensing sheet》
The organic EL device of the present invention is processed on the light extraction side of the substrate so as to provide, for example, a microlens array structure, or combined with a so-called condensing sheet, for example, with respect to a specific direction, for example, the device light emitting surface. By condensing in the front direction, the luminance in a specific direction can be increased.

  As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

  As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, Sumitomo 3M brightness enhancement film (BEF) can be used. As the shape of the prism sheet, for example, the base material may be formed with a triangle stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is changed randomly. Other shapes may be used.

  Moreover, in order to control the light emission angle from a light emitting element, you may use together a light diffusing plate and a film with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<< Method for producing organic EL element >>
The method for producing an organic EL device according to the present invention is characterized in that a part or all of an organic layer sandwiched between an anode and a cathode is formed by a wet process, and at least a light emitting layer is formed by a wet process. The wet process referred to in the present invention is to form a layer by supplying a layer forming material in the form of a solution when forming a layer.

  As an example of a method for producing an organic EL device according to the present invention, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode will be described.

  First, a desired electrode material, for example, a thin film made of an anode material is formed on a suitable substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm, thereby producing an anode.

  Next, organic compound thin films (organic layers) such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, which are organic EL element materials, are formed thereon.

  As a method for forming each of these layers, there are a vapor deposition method, a wet process (spin coating method, casting method, ink jet method, spray method, printing method, slot type coater method, etc.) as described above. Further, in the present invention, a wet process such as a spin coating method, a casting method, an ink jet method, a spray method, a printing method, a slot type coater method, etc., from the viewpoint that a homogeneous film is easily obtained and pinholes are hardly generated. Film formation by the method is preferred.

  Examples of the liquid medium for dissolving or dispersing the organic EL material according to the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, and mesitylene. Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used.

  After these layers are formed, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 50 to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained.

  In addition, it is also possible to reverse the production order and produce the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order. When a direct current voltage is applied to the organic EL device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the anode as + and the cathode as-. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

  Hereinafter, an example of the organic EL element of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing an example of the organic EL element of the present invention.

  In the organic EL element, an anode 20 is provided on a substrate 10, and a hole injection layer 30, a hole transport layer 40, a light emitting layer 50, an electron transport layer 60, and an electron injection layer are sequentially provided on the anode. Further, a cathode 80 is provided on the electron injection layer.

  The light emitting layer 50 has a range 51 having an average concentration of 50% or more with respect to the average concentration of all light emitting dopants contained in the light emitting layer on the anode side. The range 51 may exist on the cathode side, or may exist on both the anode side and the cathode side.

<Application>
The organic EL element of the present invention can be used as a display device, a display, and various light emission sources. For example, lighting devices (home lighting, interior lighting), clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, Especially, it can use effectively for the use as a backlight of a liquid crystal display device, and a light source for illumination.

  In the organic EL element of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as needed during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned, and a conventionally known method may be used in the fabrication of the element. it can.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

Example 1
<< Production of Organic EL Element 101 >>
After patterning a 100 mm × 100 mm × 1.1 mm glass substrate made of ITO (Indium Tin Oxide) 100 nm as an anode, the transparent support substrate provided with the ITO transparent electrode was superposed with normal propyl alcohol. Sonic cleaning, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes.

  On this transparent support substrate, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water at 3000 rpm for 30 seconds. After forming the film by spin coating, the film was dried at 200 ° C. for 1 hour to provide a hole injection layer (HTL) having a thickness of 30 nm.

  Next, the substrate was moved to a glove box under a nitrogen atmosphere, and spin coating was performed at 1500 rpm for 30 seconds using a solution in which compound HT-1 (weight average molecular weight 50000; 50 mg) was dissolved in 10 ml of monochlorobenzene ( And dried at 160 ° C. for 30 minutes under nitrogen to form a hole transport layer (HTL).

  On the hole transport layer, a solution in which compound H-33 (weight average molecular weight 50000; 128 mg) and compound D-55 (24 mg) were dissolved in 10 ml of 3-methylbutyl acetate (20 ° C. vapor pressure: 0.53 kPa) was used. Then, spin coating (film thickness of about 40 nm) was performed under conditions of 1500 rpm for 30 seconds, and dried under nitrogen at 120 ° C. for 30 minutes to obtain a light emitting layer (EML).

  On this light emitting layer, spin coating (film thickness of about 20 nm) was carried out under conditions of 1500 rpm and 30 seconds using a solution in which compound ET-1 (50 mg) was dissolved in 10 ml of 2,2,3,3-tetrafluoropropanol. And dried under nitrogen at 120 ° C. for 30 minutes to form an electron transport layer (ETL).

The substrate is attached to a vacuum deposition apparatus, the vacuum chamber is depressurized to 4 × 10 ⁻⁴ Pa, LiF is deposited as an electron injection layer at 1 nm, then aluminum 110 nm is deposited to form a cathode, and the organic EL element 101 is formed. Produced.

<< Production of Organic EL Element 102 >>
An organic EL element 102 was produced in the same manner except that the compound H-33 was changed to H-32 in the production of the organic EL element 101.

<< Production of Organic EL Element 103 >>
In production of the organic EL element 101, 1500 rpm, 30 seconds using a solution in which compound H-33 (73 mg) and compound D-55 (14 mg) were dissolved in 10 ml of normal propyl acetate (20 ° C. vapor pressure: 3.3 kPa). The organic EL device 103 was produced in the same manner except that the light-emitting layer was formed by spin coating (film thickness: about 40 nm) under the above conditions and drying under nitrogen at 120 ° C. for 30 minutes.

<< Production of Organic EL Element 104 >>
An organic EL element 104 was produced in the same manner except that the compound H-33 was changed to H-32 in the production of the organic EL element 103.

<< Production of Organic EL Element 105 >>
Organic EL element 105 was similarly manufactured except that compound H-33 was changed to H-5 and compound D-55 was changed to D-46 in preparation of organic EL element 103.

<< Production of Organic EL Element 106 >>
An organic EL element 106 was produced in the same manner except that the compound D-46 was changed to D-44 in the production of the organic EL element 105.

<< Preparation of organic EL element 107 >>
An organic EL element 107 was produced in the same manner except that the compound D-46 was changed to D-24 in the production of the organic EL element 105.

<< Preparation of Organic EL Element 108 >>
Organic EL element 105 was similarly manufactured except that compound H-33 was changed to H-31 and compound D-55 was changed to D-46 in preparation of organic EL element 103.

<< Production of Organic EL Element 109 >>
An organic EL element 109 was produced in the same manner as in the production of the organic EL element 108, except that the compound D-46 was changed to D-44.

<< Production of Organic EL Element 110 >>
An organic EL element 110 was produced in the same manner except that the compound D-46 was changed to D-24 in the production of the organic EL element 108.

<< Production of Organic EL Element 111 >>
In the production of the organic EL element 104, the organic EL element 111 was produced in the same manner except that the solvent used for forming the light emitting layer was changed from normal propyl acetate to butyl acetate.

<< Production of Organic EL Element 112 >>
In the production of the organic EL element 110, the organic EL element 112 was produced in the same manner except that the normal propyl acetate solvent used for forming the light emitting layer was changed to butyl acetate (20 ° C. vapor pressure: 1.1 kPa).

<< Evaluation of organic EL elements >>
The obtained organic EL elements 101 to 112 were evaluated as follows. The results are shown in the table.

(Average concentration of luminescent dopant)
For each device, the inside of the light emitting layer was measured by dynamic SIMS, and the distribution of metal atoms of the light emitting dopant (iridium for D-24 and D-55, platinum for D-44 and D-46) and carbon was measured. The dynamic SIMS measured the depth direction from the side close to the anode toward the side close to the cathode. Obtain the average concentration of all luminescent dopants in the luminescent layer of each device, and examine whether the average concentration of luminescent dopants in the range of 0-5 nm and 0-10 nm is 50% or more with respect to the average concentration of all luminescent dopants. It was. In each element, the following was set.

X: When the average concentration of the light-emitting dopant of 0 to 5 nm is not 50% or more with respect to the average concentration of all the light-emitting dopants in the light-emitting layer ○: The average concentration of the light-emitting dopant of 0 to 5 nm is the average concentration of all the light-emitting dopants in the light-emitting layer On the other hand, when the average concentration of 0 to 10 nm is not 50% or more with respect to the average concentration of all the light emitting dopants in the light emitting layer, the average concentration of the light emitting dopant of 0 to 10 nm is that of all the light emitting dopants in the light emitting layer. When it is 50% or more of the average concentration.

(Luminance brightness)
The light emission luminance (cd / m ² ) when a temperature of 23 ° C. and a DC voltage of 10 V were applied to the organic EL element was measured. The light emission luminance is expressed as a relative value when the organic electroluminescence element 101 is 100. The light emission luminance was measured using CS-1000 (manufactured by Konica Minolta Sensing).

(Drive voltage)
The driving voltage is a voltage when driving at ^2.5 mA / cm ² , and is expressed as a relative value when the organic electroluminescence element 101 is 100.

(Voltage increase rate)
When driven at a constant current of 10 mA / cm ² , the initial voltage and the voltage after 100 hours were measured. The initial voltage was 100, and the relative value of the voltage after 100 hours with respect to the initial voltage was defined as the voltage increase rate.

  As can be seen from Table 1, it is clear that the organic EL device of the present invention is driven at a lower voltage and has higher emission luminance than the comparison. In addition, it was found that the device was a good element with little increase in voltage when driven at a constant current.

Example 2
<< Production of Organic EL Element 201 >>
In the production of the organic EL element 103, an organic EL element 201 was produced in the same manner except that an electron blocking layer was formed between the hole transport layer and the light emitting layer as described below.

(Deposition of an electron blocking layer in the organic EL element 201)
In a glove box under a nitrogen atmosphere, spin coating (thickness: about 20 nm) was performed at 1500 rpm for 30 seconds using a solution in which compound EB-1 (50 mg) was dissolved in 10 ml of toluene on the hole transport layer. And dried at 120 ° C. for 30 minutes under nitrogen to provide an electron blocking layer (EBL).

<< Production of Organic EL Element 202 >>
In the production of the organic EL element 103, an organic EL element 202 was produced in the same manner except that a hole blocking layer was formed between the light emitting layer and the electron transport layer as described below.

(Film formation of hole blocking layer in organic EL element 202)
In a glove box under a nitrogen atmosphere, spin coating (film) was performed at 1500 rpm for 30 seconds using a solution in which compound HB-1 was dissolved in 10 ml of 2,2,3,3-tetrafluoropropanol on the light emitting layer. And dried at 120 ° C. for 30 minutes under nitrogen to provide a hole blocking layer (HBL).

<< Production of Organic EL Element 203 >>
In the production of the organic EL element 103, an electron blocking layer was formed between the hole transport layer and the light emitting layer, and a hole transport layer was formed between the light emitting layer and the electron transport layer as in the organic elements 201 and 202 described above. In the same manner, an organic EL element 203 was produced.

<< Evaluation of organic EL elements >>
The obtained organic EL elements 201 to 203 were evaluated by the same evaluation method as in Example 1. The results are shown in Table 2.

  As can be seen from Table 2, the organic EL device of the present invention has high emission luminance even when the adjacent layer is other than the hole transport layer, has a low driving voltage, and has a small voltage increase when driven at a constant current. It turned out to be a simple element.

DESCRIPTION OF SYMBOLS 10 Board | substrate 20 Anode 30 Hole injection layer 40 Hole transport layer 50 Light emitting layer 51 The range which is an average density | concentration of 50% or more with respect to the average density | concentration of all the light emission dopants contained in a light emitting layer 60 Electron transport layer 70 Electron injection layer 80 cathode

Claims (10)

  An organic electroluminescent device having a light emitting layer containing a light emitting host and a light emitting dopant as a constituent layer between an anode and a cathode, wherein the light emitting layer is formed by a wet process and adjacent to the light emitting layer of the light emitting layer The average concentration of the light emitting dopant in the range of 0 to 5 nm from the interface with at least one adjacent layer is 50% or more with respect to the average concentration of all the light emitting dopants contained in the light emitting layer. Luminescence element.   2. The organic electroluminescence device according to claim 1, wherein a range having an average concentration of 50% or more with respect to an average concentration of all light-emitting dopants contained in the light emitting layer is 0 to 10 nm.   The range which is an average concentration of 50% or more with respect to the average concentration of all the light emitting dopants contained in the light emitting layer is present on the side close to the anode in the light emitting layer. Organic electroluminescence element.   The organic electroluminescent element according to claim 1, wherein the light emitting host has a molecular weight of 1500 or less. The organic light-emitting device according to claim 1, wherein the light-emitting host has at least three or more partial structures represented by the following general formula (a) in a molecule.

(In the formula, X represents NR ′, O, S, CR′R ″ or SiR′R ″. R ′ and R ″ each represents a hydrogen atom or a substituent. Ar is necessary for forming an aromatic ring. N represents an integer of 0 to 8.)   One of the said adjacent layers is an electron carrying layer, The organic electroluminescent element of any one of Claims 1-5 characterized by the above-mentioned.   One of the said adjacent layers is a positive hole transport layer, The organic electroluminescent element of any one of Claims 1-5 characterized by the above-mentioned.   The organic electroluminescence device according to claim 1, wherein the light emitting dopant exhibits phosphorescence. The organic light-emitting device according to claim 1, wherein the light-emitting dopant is an organometallic complex represented by the following general formula (1).

(In the formula, Z represents a hydrocarbon ring group, an aromatic heterocyclic group or a heterocyclic group. R _{81 to} R ₈₆ represent a hydrogen atom or a substituent. P ₁ -L ₁ -P ₂ is a bidentate coordination. P ₁ and P ₂ each independently represents a carbon atom, a nitrogen atom or an oxygen atom, L 1 represents an atomic group which forms a bidentate ligand together with P ₁ and P ₂ , j 1 is 1 to 1 represents the integer 3, j2 is an integer of 0 to 2, j1 + j2 is 2 or 3 .M ₁ represents a metal element of group 8 to group 10 in the periodic table.) The organic electroluminescent element according to claim 9, wherein M _{1 in the} general formula (1) is iridium.

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