JP6107657B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescence element, and more particularly to a technique suitable for obtaining white light emission excellent in power efficiency and light emission lifetime.

In general, an organic electroluminescence element (organic EL element) basically has a layer structure composed of an anode / an organic light emitting layer / a cathode, and a layer such as a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer. Is appropriately provided.
In the organic light emitting layer, holes and electrons injected from the anode and the cathode recombine to generate excitons, and light emission occurs via the excitons. The excitons generated here are a mixture of singlet excitons and triplet excitons, and are considered to be generated at a ratio of singlet excitons: triplet excitons = 1: 3 in statistical theory. ing.

  Until now, many organic EL devices have used a light emitting substance that emits fluorescence when returning from a singlet excited state to a ground state, so only 25% of singlet energy is used for light emission, and the rest 75% of the triplet energy was eventually consumed as heat. Therefore, in order to effectively use triplet energy for light emission, an organic EL element using a phosphorescent substance (phosphorescent dopant) in an organic light emitting layer (see, for example, Patent Documents 1 and 2), or a plurality of phosphorescent dopants An organic EL element in which an exciton blocking layer made of an electron transporting material is provided between organic light emitting layers (for example, see Patent Document 3) has been proposed.

By the way, in order to obtain white light suitable for illumination use or backlight use, it is necessary to have three wavelength components of blue, green, and red. In an organic EL element, for example, a blue light emitting material and a green light emitting material are used. A method for obtaining white light by mixing red light emitting materials in one element is known. For example, in the case of the phosphorescent element, blue, green, and red light emitting materials are used.
The phosphorescent light emitting element can be expected to obtain high efficiency in principle as described above, but on the other hand, the luminance life at the time of driving is not always satisfactory at present. This is mainly because the driving stability of the blue phosphorescent material is not good. Therefore, in order to obtain a highly efficient and long-life device, an organic EL element using a blue fluorescent material and green and red phosphorescent materials has been proposed (see, for example, Patent Documents 4 to 6).
In the techniques of Patent Documents 5 and 6, a special bipolar layer is provided between an organic light emitting layer containing a red or green phosphorescent dopant and an organic light emitting layer containing a blue fluorescent dopant (see Patent Document 5). For example, a non-light emitting interface layer is provided (see Patent Document 6) to improve luminous efficiency and device life.

JP 2001-284056 A Special table 2002-525808 gazette JP-T-2004-522276 JP 2004-227814 A Japanese Patent No. 4969948 Japanese Patent No. 4496949

However, according to the techniques of Patent Documents 5 and 6, it is necessary to form a special layer such as the bipolar layer or the non-light emitting interface layer, and in general organic EL elements including the techniques of Patent Documents 5 and 6, power efficiency Further improvements are required in terms of the light emission lifetime, and improvements are also required for the suppression of changes over time in chromaticity and drive voltage.
Therefore, the main object of the present invention is to improve power efficiency and light emission lifetime in an organic EL device that obtains white color using a fluorescent light-emitting material such as blue and a phosphorescent light-emitting material of another color different from that. An object of the present invention is to provide an organic EL element capable of suppressing chronological changes in chromaticity and driving voltage.

In order to solve the above problems, according to the present invention,
In an organic electroluminescence device comprising an anode, a cathode, and a plurality of light emitting layers, wherein the plurality of light emitting layers are disposed between the anode and the cathode,
The plurality of light emitting layers have a fluorescent light emitting layer and at least two or more phosphorescent light emitting layers,
Of the fluorescent light emitting layer and the phosphorescent light emitting layer, the fluorescent light emitting layer is disposed on the anode side,
Each layer of the phosphorescent layer contains a phosphorescent dopant and a host compound,
Among the phosphorescent light emitting layers, the phosphorescent light emitting layer having the longest emission wavelength is disposed on the fluorescent light emitting layer side, and
The phosphorescent light emitting layer having the longest emission wavelength has a content higher than that of the main phosphorescent light emitting dopant of the layer, and the lowest excited triplet energy T1 is larger than T1 of the main phosphorescent light emitting dopant of the layer. There is provided an organic electroluminescence device characterized by containing a phosphorescent metal complex smaller than T1 of the compound.

  According to the present invention, it is possible to improve the power efficiency and the light emission lifetime, and further suppress the change in chromaticity and drive voltage with time.

It is the schematic which shows an example of the illuminating device incorporating the organic EL element of this invention. It is sectional drawing which shows an example of the illuminating device incorporating the organic EL element of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<< Layer structure of organic EL element >>
Next, although the preferable specific example of the layer structure of the organic EL element of this invention is shown below, this invention is not limited to these.

(I) Anode / fluorescence emission layer / phosphorescence emission layer / electron transport layer / cathode (ii) anode / hole transport layer / fluorescence emission layer / phosphorescence emission layer / electron transport layer / cathode (iii) anode / hole Transport layer / fluorescence emission layer / phosphorescence emission layer / hole blocking layer / electron transport layer / cathode (iv) anode / hole transport layer / fluorescence emission layer / phosphorescence emission layer / hole blocking layer / electron transport layer / Cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / fluorescent light emitting layer / phosphorescent light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode

The fluorescent light emitting layer is disposed on the anode side of the phosphorescent light emitting layer.
The fluorescent light emitting layer is preferably a blue fluorescent light emitting layer containing a blue fluorescent light emitting dopant.
The light emission in the blue region of the blue fluorescent light-emitting layer means that the light emission maximum wavelength is in the range of 430 nm to 480 nm.
The phosphorescent light emitting layer has a layer structure of at least two layers.
The phosphorescent light emitting layer is preferably composed of a red phosphorescent light emitting layer containing a red phosphorescent light emitting dopant and a green phosphorescent light emitting layer containing a green phosphorescent light emitting dopant.
In the laminated structure of the fluorescent light emitting layer and the phosphorescent light emitting layer, the blue fluorescent light emitting layer, the red phosphorescent light emitting layer, and the green phosphorescent light emitting layer are preferably laminated in this order from the anode to the cathode.

<Light emitting layer (phosphorescent light emitting layer, fluorescent light emitting layer)>
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer. The structure 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 total thickness of the light emitting layer is not particularly limited, but it prevents the uniformity of the film to be formed, the application of unnecessary high voltage during light emission, and the improvement of the stability of the emission color with respect to the driving current. From a viewpoint, it is preferable to adjust to the range of 5 nm-200 nm, More preferably, it adjusts to the range of 20 nm or more and 150 nm or less. Moreover, in the structure prescribed | regulated by the structure of this invention, it is preferable to adjust as the film thickness of each light emitting layer in the range of 5 nm-200 nm, More preferably, by adjusting in the range of 3 nm or more and 150 nm or less. is there.

As described above, the light emitting layer according to this embodiment includes a fluorescent light emitting layer and a phosphorescent light emitting layer.
The fluorescent light emitting layer contains a fluorescent light emitting dopant and a host compound.
The phosphorescent layer also contains a phosphorescent dopant and a host compound.

  As a method for forming the light emitting layer, a light emitting dopant or a host compound described later can be used, for example, a vacuum deposition method, a spin coating method, a casting method, an LB method (Langmuir-Blodget method), an ink jet method, a spray method, a printing method, The film can be formed by a known thin film forming method such as a slot type coater method.

  The number of layers constituting the light emitting layer is not particularly limited as long as it satisfies the requirements defined in the present invention, but at least two phosphorescent light emitting layers and blue light emitting in one blue region. And a fluorescent light emitting layer.

  The phosphorescent light emitting or fluorescent light emitting dopant contained in each light emitting layer may be contained in the light emitting layer at a uniform concentration in the film thickness direction, but has a concentration distribution. Also good.

(1) Host Compound Next, a host compound (also referred to as a light emitting host compound) contained in the light emitting layer will be described.

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

  As the phosphorescent host compound, the host compound may be used alone or in combination of two or more.

  The phosphorescent host compound used in the present invention is not particularly limited in terms of structure, but is typically a carbazole derivative, triarylamine derivative, aromatic borane derivative, nitrogen-containing heterocyclic compound, thiophene derivative, furan derivative. A compound having a basic skeleton such as an oligoarylene compound, or a carboline derivative or a diazacarbazole derivative (herein, a diazacarbazole derivative is at least one carbon atom of a hydrocarbon ring constituting a carboline ring of a carboline derivative) Represents the one substituted with a nitrogen atom).

  As the phosphorescent host compound used in the light emitting layer according to the present invention, a compound represented by the following general formula (a) is preferable.

  In the general formula (a), X represents NR ′, O, S, CR′R ″ or SiR′R ″, R ′ and R ″ each represent a hydrogen atom or a substituent. Ar represents an aromatic ring. N represents an integer of 0 to 8.

  In X in the general formula (a), the substituents represented by R ′ and R ″ are alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group). Group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (for example, vinyl group, allyl group, 1-propenyl group, 2 -Butenyl group, 1,3-butadienyl group, 2-pentenyl group, isopropenyl group, etc.), alkynyl group (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon group (aromatic carbocyclic group, aryl group, etc.) For example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, an Ryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc., aromatic heterocyclic group (for example, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group) Group, triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolinyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom) ), A phthalazinyl group, etc.), a heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), an alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, Hexyloxy group, oct Ruoxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group). Propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (for example, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (Eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, etc.) Xycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, Dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group) 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy (For example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethyl group) Carbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (For example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, A cyclohexylaminocarbonyl group, an octylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, a dodecylaminocarbonyl group, a phenylaminocarbonyl group, a naphthylaminocarbonyl group, a 2-pyridylaminocarbonyl group, etc.), a ureido group (for example, a methylureido group, Ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl) Group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, Dilsulfinyl group etc.), alkylsulfonyl group (eg methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group etc.), arylsulfonyl group or heteroarylsulfonyl group (eg , Phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), 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, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, Tafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), phosphono Groups and the like.

  These substituents may be further substituted with the above substituents. In addition, a plurality of these substituents may be bonded to each other to form a ring.

  In the general formula (a), X is preferably NR ′ or O, and R ′ is particularly preferably an aromatic hydrocarbon group or an aromatic heterocyclic group.

  In the general formula (a), examples of the aromatic ring represented by Ar include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. Further, the aromatic ring may be a single ring or a condensed ring, and may be unsubstituted or may have a substituent as described later.

  In the general formula (a), examples of the aromatic hydrocarbon ring represented by Ar include a benzene ring, biphenyl ring, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, 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, picene ring, pyrene ring, Examples include a pyranthrene ring and anthraanthrene ring. These rings may further have a substituent.

  In 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, a pyrimidine ring, a pyrazine ring, and a triazine ring. , Benzimidazole ring, oxadiazole ring, triazole ring, imidazole ring, pyrazole ring, thiazole ring, indazole 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 (showing a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom), etc. Can be mentioned. These rings may further have a substituent.

  Among these, 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 particularly preferably used is a carbazole ring, A carboline ring or a benzene ring. Among these, a benzene ring having a substituent is preferable, and a benzene ring having a carbazolyl group is particularly preferable.

  In the general formula (a), the aromatic ring represented by Ar is preferably a condensed ring having three or more rings, as shown below, and is an aromatic hydrocarbon in which three or more rings are condensed. Specific examples of the condensed ring include 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, naphthoperylene ring, pentabenzoperylene ring, benzoperylene ring, pentaphen ring, picene ring, pyranthrene ring, coronene ring , Naphthocoronene ring, Ovalene ring, Anse Antoren ring and the like. In addition, these rings may further have a 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, Quindrine 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.

  Here, in the general formula (a), the substituents that the aromatic ring represented by Ar may have are the same as the substituents represented by R ′ and R ″.

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

  Specific examples of the light-emitting host compound represented by the general formula (a) are shown below, but are not limited thereto.

  The phosphorescent host compound used in the present invention may be a 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 (evaporation polymerizable light emitting host). But it is good.

  As the phosphorescent host compound, a compound that has a hole transporting ability and an electron transporting ability, prevents emission light from being increased in wavelength, and has a high Tg (glass transition temperature) is preferable.

  As specific examples of conventionally known host compounds, compounds described in the following documents are suitable. For example, Japanese Patent Application Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787 gazette, 2002-15871 gazette, 2002-334788 gazette, 2002-43056 gazette, 2002-334789 gazette, 2002-75645 gazette, 2002-338579 gazette. No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453. No. 2003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060. 2002-302516, 2002-305083, 2002-305084, 2002-308837, and the like.

  In the present invention, in the case of having a plurality of light emitting layers, the host compound may be different for each light emitting layer, but the same compound is preferable because excellent driving life characteristics are obtained.

  Further, the phosphorescent host compound preferably has a lowest excited triplet energy (T1) larger than 2.2 eV because higher luminous efficiency can be obtained. The lowest excited triplet energy as used in the present invention refers to the peak energy of the emission band corresponding to the transition between the lowest vibrational bands of the phosphorescence emission spectrum observed at a liquid nitrogen temperature after dissolving the host compound in a solvent.

  In the present invention, a compound having a glass transition point of 90 ° C. or higher is preferable, and a compound having a glass transition temperature of 130 ° C. or higher is preferable because excellent driving life characteristics can be obtained.

  Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).

  In the organic EL device of the present invention, since the host material is responsible for carrier transport, a material having carrier transport capability is preferable. Carrier mobility is used as a physical property representing carrier transport ability, but the carrier mobility of an organic material generally depends on the electric field strength. Since a material having a high electric field strength dependency easily breaks the balance of hole and electron injection / transport, it is preferable to use a material having a low electric field strength dependency of mobility for the intermediate layer material and the host material.

  In addition, the said phosphorescent host compound can be used suitably also as a host compound with respect to a fluorescence emission dopant.

(2) Luminescent dopant Next, the luminescent dopant according to the present invention will be described.

(2.1) Fluorescent light emitting dopant (also called fluorescent dopant, fluorescent light emitter, etc.)
Examples of the fluorescent dopant used as the luminescent material according to the present invention include a coumarin dye, a pyran dye, a cyanine dye, a croconium dye, a squalium dye, an oxobenzanthracene dye, a fluorescein dye, a rhodamine dye, Examples include pyrylium dyes, perylene dyes, stilbene dyes, polythiophene dyes, and rare earth complex phosphors.

  Conventionally known dopants can also be used in the present invention. For example, International Publication No. 00/70655 pamphlet, JP-A Nos. 2002-280178, 2001-181616, 2002-280179, 2001 181617, 2002-280180, 2001-247859, 2002-299060, 2001-313178, 2002-302671, 2001-345183, 2002. No. 324679, International Publication No. 02/15645, JP 2002-332291 A, 2002-50484, 2002-332292, 2002-83684, JP 2002-540572, JP 2 No. 02-117978, No. 2002-338588, No. 2002-170684, No. 2002-352960, Pamphlet of International Publication No. 01/93642, JP 2002-50483, No. 2002-1000047. No. 2002-173684, No. 2002-359082, No. 2002-17584, No. 2002-363552, No. 2002-184582, No. 2003-7469, No. 2002-525808. JP-A 2003-7471, JP-T 2002-525833, JP-A 2003-31366, JP-A 2002-226495, JP-A 2002-234894, JP-A 2002-2335076, JP-A 2002-24175 Gazette, 2001-319779, 2001-319780, 2002-62824, 2002-1000047, 2002-203679, 2002-343572, 2002-203678. A gazette etc. are mentioned.

(2.2) Phosphorescent dopant The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescence at room temperature (25 ° C.). The phosphorescence quantum yield is defined as a compound of 0.01 or more at 25 ° C., but the preferred phosphorescence quantum yield is 0.1 or more.

  The phosphorescence quantum yield can be measured, for example, by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of 4th edition Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescent emitter according to the present invention has the phosphorescence quantum yield (0.01 or more) in any solvent. It only has to be achieved.

There are two types of light emission principle of the phosphorescent dopant.
One type is that a carrier (electron, hole) is combined on the host compound to which the carrier is transported, and an excited state of the host compound is generated, and this excitation energy is transferred to the phosphorescent dopant. It is an energy transfer type that obtains light emission from.
The other type is a carrier trap type in which the phosphorescent light emitting dopant becomes a carrier trap, carrier recombination occurs on the phosphorescent light emitting dopant, and light emission from the phosphorescent light emitting dopant is obtained.
In any case, the excited state energy of the phosphorescent dopant is preferably lower than the excited state energy of the host compound in order to obtain high light emission efficiency.

  The phosphorescent light emitting 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, or a platinum compound (platinum complex system). Compound) and rare earth complexes, and most preferred is an iridium compound.

  Specific examples of compounds that can be used in the present invention are shown below. These compounds are described in, for example, Inorg. Chem. 40, 1704-1711, and the like.

(2.3) Characteristics of Phosphorescence Emission Dopant As described above, the phosphorescence emission layer has a layer configuration of at least two layers.
Among these phosphorescent light emitting layers, the phosphorescent light emitting layer having the longest emission wavelength contains a special phosphorescent metal complex in addition to the main phosphorescent light emitting dopant of the layer. Yes.
The phosphorescent light-emitting layer mainly has the characteristics (i) and (ii).
(I) The content of the special phosphorescent metal complex is larger than the content of the phosphorescent dopant that is the main light emission.
(Ii) The lowest excited triplet energy (T1) of the special phosphorescent metal complex is larger than T1 of the phosphorescent dopant that mainly emits light and smaller than T1 of the host compound.

T1 of each compound of a phosphorescence emission dopant and a host compound can be measured by a general method in this field.
As a specific measuring apparatus, any measuring apparatus of each device company may be used. For example, excitation light is emitted at a low temperature using a spectrofluorometer (F-4500 or F-7000 type spectrofluorometer, Hitachi High-Tech). It is possible to calculate the energy level of the lowest excited triplet state by emitting phosphorescence and measuring the absorption and emission spectra.

<< Injection layer: electron injection layer, hole injection layer >>
The injection layer can be provided as necessary, and may exist 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.

  An injection layer is a layer provided between an electrode and an organic layer in order to lower drive voltage and improve light emission luminance. For example, “Organic EL element and its forefront of industrialization (November 30, 1998, NTS Corporation) Issue) ”, Chapter 2, Chapter 2,“ Electrode Materials ”(pages 123-166), which is described in detail, and has a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer). .

  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 Phthalocyanine buffer layer typified by (1), oxide buffer layer typified by vanadium oxide, amorphous carbon buffer layer, polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene, and the like. Moreover, it is also preferable to use the material described in Japanese translations of PCT publication No. 2003-519432 gazette.

  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 although it depends on the material used, the film thickness is preferably in the range of 0.1 nm to 5 μm.

<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. For example, it is described in JP-A Nos. 11-204258, 11-204359, and “Organic EL elements and their forefront of industrialization” (issued by NTT, Inc. on November 30, 1998). There is a hole blocking (hole blocking) layer.

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

  The hole blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.

  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 transport layer according to the present invention is preferably 3 nm to 100 nm, and more preferably 5 nm to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the 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.

  The above-mentioned materials can be used as the hole transport material, but it is further preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly 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-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (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 two more 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-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. , 95, 5773 (2004), JP-A-11-251067, J. MoI. Huang et. al. It is also possible to use a hole transport material that has a so-called p-type semiconducting property as described in the literature (Applied Physics Letters 80 (2002), p. 139), JP 2003-519432 A. it can. In the present invention, it is preferable to use these materials because a light-emitting element with higher efficiency can be obtained.

  For the hole transport layer, the hole transport material may be selected from, for example, vacuum deposition method, spin coating method, casting method, LB method (Langmuir-Blodget method), ink jet method, spray method, printing method, slot type coater method, etc. The film can be formed by a known thin film forming method. 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 nm-200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

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

  Conventionally, when a single electron transport layer and a plurality of layers are used, 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 transmitting the generated electrons to the light-emitting layer, any material selected from conventionally known compounds can be selected and used. For example, nitro-substituted fluorene derivatives, diphenylquinone Derivatives, thiopyran dioxide 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 similarly to the hole injection layer and the hole transport layer, inorganic such as n-type-Si and n-type-SiC can be used. A semiconductor can also be used as an electron transport material.

  For the electron transport layer, the above-mentioned electron transport material may be a known material such as a vacuum deposition method, a spin coat method, a cast method, an LB method (Langmuir-Blodget method), an ink jet method, a spray method, a printing method, or a slot type coater method. The film can be formed by a thin film forming method. 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 addition, an electron transport material that has n-type semiconductor properties doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

  In the present invention, it is preferable to use an electron transport material having such n-type semiconductor properties because an element with lower power consumption can be produced.

In the electron transport layer according to this embodiment, a compound having a phenylpyridine skeleton is contained, and at least one of an electron donating metal (metal atom), metal ion, or metal complex is doped.
The compound having a phenylpyridine skeleton is preferably represented by the general formula (1).
Note that the electron-donating metal, metal ion, or metal complex is preferably doped with respect to the electron transport layer and not with the exciton blocking layer (hole blocking layer).

In the general formula (1), “Ar1” represents an m-valent aryl group, and “R” and “R ′” each represents a hydrogen atom or a substituent. “N” represents an integer of 1 to 6. When a plurality of R and R ′ are present, adjacent substituents may be condensed with each other to form a ring.
In the general formula (1), when R and R ′ represent a substituent, specific examples of these substituents include an alkyl group (for example, a methyl group, an ethyl group, an isopropyl group, a hydroxyethyl group, a methoxymethyl group, a trimethyl group). Fluoromethyl group, perfluoropropyl group, perfluoro-n-butyl group, perfluoro-t-butyl group, t-butyl group, benzyl group, etc.) and alicyclic hydrocarbon residues such as cycloalkyl group ( A cyclopentyl group, a cyclohexyl group, etc.) and a cycloalkenyl group (for example, a cyclohexenyl group, a cyclopentenyl group), and the like, and an aralkyl group (for example, a benzyl group, a 2-phenethyl group, etc.) p-tolyl group, p-chlorophenyl group, fluorenyl group, etc.), alkoxy group (for example, ethoxy group, isopropo group) Xy group, butoxy group etc.), aryloxy group (eg phenoxy group etc.), alkylthio group (methylthio, ethylthio, isopropylthio group etc.), arylthio group (eg phenylthio group, naphthylthio group, p-tolylthio group, p-chlorophenylthio) Group), hydroxyl group, amino group (dimethylamino group, diarylamino group), alkenyl group (for example, allyl group, 1-ethenyl group, 1-propenyl group, 1-butenyl group, 1-octadecenyl group, etc.), halogen atom ( Fluorine atom, chlorine atom, bromine atom, iodine atom, etc.).
These groups may be further substituted, and examples of the substituent include a halogen atom, hydroxyl group, nitro group, cyano group, carboxyl group, sulfo group, alkyl group, aryl group, alkoxy group, aryloxy group, alkylthio group. Group, arylthio group, alkylsulfonyl group, arylsulfonyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyl group, acyloxy group, amino group, carbonamido group, sulfonamido group, carbamoyl group, sulfamoyl group, ureido group, alkoxycarbonyl An amino group, a sulfamoylamino group, etc. are mentioned.
Preferable examples of R and R ′ include a hydrogen atom, an alkyl group, and an aryl group, and a hydrogen atom is more preferable.

In the general formula (1), the benzene ring and the pyridine ring may be bonded at any position, but preferably bonded to the benzene ring at the 2-position of the pyridine, and the benzene ring side is bonded to Ar1. It is preferably bonded to the pyridine ring at the ortho position. In addition, a structure in which a benzene ring and a pyridine ring are condensed via R and R ′ may be employed.
In the general formula (1), the aryl group represented by Ar1 is an aromatic hydrocarbon group such as phenyl group, naphthyl group, triphenylene group, biphenyl group, terphenyl group, pyridyl group, pyrimidyl group, triazinyl group, thienyl group, Examples include an aromatic heterocyclic group such as a furyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothienyl group, a quinolyl group, an isoquinolyl group, an azacarbazolyl group, and the aryl group represented by Ar1 may have a substituent. Further, it may have a structure in which a plurality of aryl groups are linked. Examples of the aryl group represented by Ar1 include a phenyl group, a dibenzofuranyl group, a carbazolyl group, a dibenzothienyl group, and azacarbazolyl.
In the general formula (1), n represents an integer of 1 to 6, and is bonded to the phenylpyridine structure through n bonds from the aryl group. n is preferably 2 or 3, and as specific Ar1 structures, the following structures or combinations thereof are preferably used.
In the following structure, “Ar2” represents an aryl group and is bonded to the benzene ring of the general formula (1) at the position of “*”.

  Although the specific example of the compound which concerns on General formula (1) is shown, it is not limited to these.

《Support substrate》
The support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) applied to the organic EL element of the present invention is not particularly limited in the type of glass, plastic, etc., and may be transparent. It may be opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support 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, Cycloolefin resins such as polyether imide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned. An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film, and the water vapor permeability measured by a method according to JIS K 7129-1992 is 0.01 g / (m ² · 24 h · atm) or less, and the oxygen permeability measured by a method according to JIS K 7126-1992 is preferably 10 ⁻³ g / (m ² · 24 h) or less. The water vapor permeability is preferably a high barrier film of 10 ⁻³ g / (m ² · 24 h) or less, and both the water vapor permeability and the oxygen permeability are 10 ⁻⁵ g / (m ² · 24h) or less is more preferable.

  As a material for forming the barrier film, any material may be used as long as it 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 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 layers made of organic materials. 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, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma. A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is also preferable.

  Examples of the opaque support substrate include metal plates / films such as aluminum and stainless steel, opaque resin substrates, ceramic substrates, and the like.

<Sealing>
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support substrate with an adhesive.

  The sealing member may be disposed so as to cover the display area of the organic EL element, and may be concave or flat. Moreover, 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 organic EL element can be thinned. Furthermore, the polymer film preferably has an oxygen permeability of 10 ⁻³ g / (m ² · 24 h) or less and a water vapor permeability of 10 ⁻³ g / (m ² · 24 h) or less. Moreover, it is more preferable that both the water vapor permeability and the oxygen permeability are 10 ⁻⁵ 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 the adhesive include photocuring and thermosetting adhesives having a reactive vinyl group of acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylate. be able to. Moreover, the 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 it like screen printing.

  In addition, it is also preferable to coat the electrode and the organic layer on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and form an inorganic or organic layer in contact with the support substrate to form a sealing film. it can. 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 the element such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like is used. it can. Furthermore, 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 method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization 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 is injected in the gas phase and the liquid phase. Is preferred. A vacuum can also be used. 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) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg, calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchloric acids (eg, barium perchlorate) , Magnesium perchlorate, etc.), 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 outside the sealing film or the sealing film on the side facing the support substrate with the organic layer interposed therebetween. In particular, when sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus 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, but the polymer film is light and thin. Is preferably used.

"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 an electrode substance include conductive transparent materials such as metals such as Au, 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. ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. 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 nm to 1000 nm, preferably 10 nm to 200 nm.

"cathode"
On the other hand, as the cathode, a material having a low 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 a 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 nm 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 emission luminance is advantageously improved.

  Moreover, after producing the said metal by the film thickness of 1 nm-20 nm to a cathode, the 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.

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

  First, a desired electrode material, for example, a thin film made of a material for an anode is formed on a suitable support substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 nm to 200 nm, thereby producing an anode. To do. Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, and an electron transport layer, which are organic EL element materials, is formed thereon.

  As a method for thinning the organic compound thin film, as described above, the vapor deposition method, the wet process (spin coating method, casting method, ink jet method, printing method, LB method (Langmuir-Blodgett method), spray method, printing method, However, vacuum deposition, spin coating, ink-jet, printing, and slot-type coater methods are particularly preferred from the standpoint that a homogeneous film is easily obtained and pinholes are not easily formed. preferable.

Further, different film forming methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 ° C. to 450 ° C., a vacuum degree of 10 ⁻⁶ Pa to 10 ⁻² Pa, and a vapor deposition rate of 0. It is desirable to select appropriately within the range of 01 nm / second to 50 nm / second, substrate temperature −50 ° C. to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 nm to 200 nm. After forming these layers, 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 in the range of 50 nm to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained.

  The organic EL element is preferably produced from the hole injection layer to the cathode consistently by a single evacuation, but may be taken out halfway and subjected to different film forming methods. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere.

  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 DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 V 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.

《Light extraction improvement technology》
An organic electroluminescence element emits light inside a layer having a higher refractive index than air (refractive index of about 1.6 to 2.1), and can extract only about 15% to 20% of the light generated in the light emitting layer. It is generally said 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 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 side surface of the device.

  As a technique for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the transparent substrate and the air interface (for example, US Pat. No. 4,774,435), A method for improving efficiency by providing light condensing property (for example, JP-A-63-314795), a method for forming a reflective surface on a side surface of an element (for example, JP-A-1-220394), a substrate, etc. A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (for example, Japanese Patent Application Laid-Open No. 62-172691), lower refraction than the substrate between the substrate and the light emitter A method of introducing a flat layer having a refractive index (for example, Japanese Patent Application Laid-Open No. 2001-202827), and a method of forming a diffraction grating between any one of the substrate, the transparent electrode layer and the light emitting layer (including between the substrate and the outside world) ( JP-A-11 No. 283,751 Publication), and the like.

  In the present invention, these methods can be used in combination with the organic electroluminescence device of the present invention, but a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, A method of forming a diffraction grating between any layers of the transparent 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 low refractive index medium 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 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. Furthermore, it is preferable that it is 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 that causes total reflection or in any medium has a feature that the effect of improving the light extraction efficiency is high. 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 or second-order diffraction. The light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating into any layer or medium (in the transparent substrate or transparent electrode). , Trying to extract light 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. 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.

  The position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or 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 gratings is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

  The organic electroluminescence device of the present invention is processed to provide a structure on the microlens array, for example, on the light extraction side of the support substrate (substrate), or combined with a so-called condensing sheet, for example, in a specific direction, By condensing in the front direction with respect to the element light emitting surface, 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 μm 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, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, a substrate may be formed with a Δ-shaped stripe having an apex angle of 90 degrees and a pitch of 50 μm, or the apex angle is rounded and the pitch is changed randomly. Other shapes may also be used.

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

<Display device>
A display device to which the organic EL element of the present invention is applied will be described.
The organic EL element of the present invention is used for a multicolor or white display device. In the case of a multicolor or white display device, a shadow mask is provided only at the time of forming a light emitting layer, and a film can be formed on one surface by vapor deposition, casting, spin coating, ink jet, printing, slot coater, or the like. When patterning is performed only on the light-emitting layer, the method is not limited, but a vapor deposition method, an inkjet method, and a printing method are preferable. In the case of using a vapor deposition method, patterning using a shadow mask is preferable.

  Further, it is also possible to produce the cathode, the electron transport layer, the hole blocking layer, the light emitting layer, the hole transport layer, and the anode in this order by reversing the production order. When a DC voltage is applied to the multicolor or white display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode.

  Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

《Lighting device》
A lighting device to which the organic EL element of the present invention is applied will be described.
The organic EL device of the present invention may be used as a kind of lamp such as an illumination or exposure light source, a projection device that projects an image, or a display device that directly recognizes a still image or a moving image. (Display) may be used. The driving method when used as a display device for moving image reproduction may be either a simple matrix (passive matrix) method or an active matrix method.

  In the white organic electroluminescent element used for this invention, you may pattern by a metal mask, the inkjet printing method, etc. at the time of film forming as needed. When patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire element layer may be patterned.

  The light emitting dopant used in the light emitting layer is not particularly limited. For example, in the case of a backlight in a liquid crystal display element, the platinum complex according to the present invention is adapted so as to conform to the wavelength range corresponding to the CF (color filter) characteristics. Any one of known light-emitting dopants may be selected and combined, or combined with the light extraction and / or light collecting sheet according to the present invention to be whitened.

  As described above, the white organic EL element of the present invention is taken out from the organic electroluminescence element by combining the CF (color filter) and arranging the element and the driving transistor circuit in accordance with the CF (color filter) pattern. Using white light as a backlight, blue light, green light, and red light are obtained through a blue filter, a green filter, and a red filter, so that a full-color organic electroluminescence display with a low driving voltage and a long life can be obtained.

<< Characteristics of organic EL elements, etc. >>
According to the above organic EL element, a white light emitting organic EL element using a blue fluorescent light emitting dopant and a longer wave (green and red) phosphorescent light emitting dopant in combination is provided. White light-emitting organic EL devices using a blue fluorescent dopant and a longer-wave phosphorescent dopant in combination have been developed since long life and high color rendering properties can be expected. In order to achieve high efficiency, and from the viewpoint of production suitability, a three-layer structure having three different colors of B (blue), G (green), and R (red) is preferable.
The inventors of the present invention have a preferable stacking order of blue / phosphorescent light (at least two layers) from the anode side, particularly blue / red / green with less energy loss (excitation energy diffusion) to the outside of the light emitting unit (light emitting layer). I found out.

  On the other hand, in such a configuration, the light emitting intensity of the central light emitting layer where the energy tends to concentrate tends to be strong, and it is necessary to reduce the thickness of the light emitting layer as compared with the multilayer in order to achieve white balance. In general, the luminance life of an organic EL element tends to be shortened when the light emitting layer is thin. It is also presumed that the carrier trap frequency per molecule of the light emitting material is increased and the material is easily deteriorated from radicals. In the case of white, for example, chromaticity is likely to change due to a change in carrier balance during storage over time.

The present inventors have incorporated a phosphorescent metal complex having the above-described characteristics into the red light emitting layer located in the center in the above light emitting layer structure, particularly the blue / red / green light emitting layer structure. It has been found that the luminance life can be improved while maintaining high efficiency (see Example 1).
The cause of this is not clear, but it is presumed that, for example, the presence of the metal complex could reduce the radical state existence frequency of the red light emitting material.
Furthermore, the present inventors can relax the change over time by doping an electron-donating metal in the electron transport layer and suppress fluctuations in chromaticity and driving voltage, and particularly with an electron transport material having a phenylpyridine skeleton. It has been found that the combination exhibits an excellent fluctuation suppressing effect (see Example 2).

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
The film thickness of each blue, red, and green light emitting layer of each organic EL element shown below is selected so as to exhibit white light emission in the range of the correlated color temperature from 4400K to 4000K at a luminance of 1000 cd / m ² .
The compounds used below have the following structures.

In addition, the value [eV] of the lowest excited triplet energy T1 of each compound of GD-1 (green phosphorescent dopant), AD-1, RD-1 (red phosphorescent dopant), and H-1 (host compound) is measured. As a result, the values were as follows.
GD-1 2.4 [eV]
AD-1 2.6 [eV]
RD-1 2.0 [eV]
H-1 2.8 [eV]

<< Production of organic EL element >>
(1) Preparation of organic EL element 101 After patterning on a support substrate in which ITO (indium tin oxide) was formed to a thickness of 110 nm on a glass substrate having a thickness of 30 mm × 30 mm and a thickness of 0.7 mm as an anode, The transparent support substrate with the ITO transparent electrode is ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. Then, the transparent support substrate is placed on a substrate holder of a commercially available vacuum deposition apparatus. Fixed.

Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an optimum amount for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.
After depressurizing to a vacuum of 1 × 10 ⁻⁴ Pa, the deposition crucible containing Compound M-1 was energized and heated, deposited on a transparent support substrate at a deposition rate of 0.1 nm / second, and 20 nm holes An injection layer was provided.
Next, α-NPD was deposited in the same manner to provide a 70 nm hole transport layer.

Next, Compound GD-1 and Compound H-1 are co-deposited at a deposition rate of 0.1 nm / second so that Compound GD-1 has a concentration of 9% by volume, thereby forming a green phosphorescent light emitting layer having a thickness of 15 nm. did.
Next, the compounds GD-1, RD-1 and the compound H-1 were co-deposited at a deposition rate of 0.1 nm / second so that the concentration of the compound GD-1 was 9% by volume and the RD-1 was 2% by volume. A red phosphorescent light emitting layer having a thickness of 7 nm was formed.
In the red phosphorescent light emitting layer, main light emission is brought about by the compound RD-1.
In the red phosphorescent light emitting layer, the compound RD-1 corresponds to a phosphorescent dopant that mainly emits light, and the compound GD-1 corresponds to a special phosphorescent metal complex.
In the red phosphorescent light emitting layer, the content of compound GD-1 is greater than the content of compound RD-1.
In the red phosphorescent light emitting layer, the value of T1 of compound GD-1 is larger than the value of T1 of compound RD-1, and smaller than the value of T1 of compound H-1.
Subsequently, Compound BD-1 and Compound H-2 were co-deposited at a deposition rate of 0.1 nm / second so that Compound BD-1 had a concentration of 7%, and a blue fluorescent light-emitting layer having a thickness of 35 nm was formed. .

Thereafter, compound HB-1 was deposited to a thickness of 10 nm at a deposition rate of 0.1 nm / second to form an exciton blocking layer, and then compound E-1 was deposited to a thickness of 25 nm at a deposition rate of 0.1 nm / second. Thus, an electron transport layer was formed.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.

Next, the non-light-emitting surface of the element was covered with a glass case, and an “organic EL element 101” having the configuration shown in FIGS. 1 and 2 was produced.
FIG. 1 shows a schematic diagram of an organic EL element.
As shown in FIG. 1, the organic EL element 101 is covered with a glass cover 102. The sealing operation with the glass cover 102 was performed in a glove box (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) in a nitrogen atmosphere without bringing the organic EL element 101 into contact with the atmosphere.
FIG. 2 shows a cross-sectional view of the organic EL element.
As shown in FIG. 2, an organic EL layer 106 and a cathode 105 are laminated and formed on a glass substrate 107 with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.

(2) Preparation of organic EL element 102 It carried out similarly to the organic EL element 1, and provided to the positive hole transport layer.
Next, Compound BD-1 and Compound H-2 were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of Compound BD-1 was 7%, thereby forming a blue fluorescent light-emitting layer having a thickness of 10 nm.
Next, Compound RD-1 and Compound H-1 are co-evaporated at a deposition rate of 0.1 nm / second so that Compound RD-1 has a concentration of 8% by volume, thereby forming a red phosphorescent light emitting layer having a thickness of 7 nm. did.
Next, Compound GD-1 and Compound H-1 are co-deposited at a deposition rate of 0.1 nm / second so that Compound GD-1 has a concentration of 9% by volume to form a green phosphorescent light emitting layer having a thickness of 25 nm. did.

Thereafter, compound HB-1 was deposited to a thickness of 10 nm at a deposition rate of 0.1 nm / second to form an exciton blocking layer, and then compound E-1 was deposited to a thickness of 25 nm at a deposition rate of 0.1 nm / second. Thus, an electron transport layer was formed.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 101, the non-light-emitting surface was covered with a glass case, and an “organic EL element 102” was produced.

(3) Preparation of organic EL element 103 It carried out similarly to the organic EL element 102, and provided even the blue fluorescence light emitting layer.
Next, the compounds GD-1, RD-1, and H-1 were co-polymerized at a deposition rate of 0.1 nm / second so that the concentration of the compound GD-1 was 9% by volume and the concentration of the compound RD-1 was 2% by volume. Evaporation was performed to form a red phosphorescent light emitting layer having a thickness of 5 nm.
In the red phosphorescent light emitting layer, main light emission is brought about by the compound RD-1.
In the red phosphorescent light emitting layer, the compound RD-1 corresponds to a phosphorescent dopant that mainly emits light, and the compound GD-1 corresponds to a special phosphorescent metal complex.
In the red phosphorescent light emitting layer, the content of compound GD-1 is greater than the content of compound RD-1.
In the red phosphorescent light emitting layer, the value of T1 of compound GD-1 is larger than the value of T1 of compound RD-1, and smaller than the value of T1 of compound H-1.
Next, Compound GD-1 and Compound H-1 are co-deposited at a deposition rate of 0.1 nm / second so that Compound GD-1 has a concentration of 9% by volume to form a green phosphorescent light emitting layer having a thickness of 30 nm. did.

Thereafter, Compound HB-1 was deposited at a film thickness of 10 nm at a deposition rate of 0.1 nm / second to form an exciton blocking layer (hole blocking layer), and then Compound E-1 was deposited at a film thickness of 25 nm at a deposition rate of 0. The electron transport layer was formed by vapor deposition at a rate of 1 nm / second.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 101, the non-light-emitting surface was covered with a glass case to produce an "organic EL element 103".

(4) Preparation of organic EL element 104 It carried out similarly to the organic EL element 102, and provided even the blue fluorescence light emitting layer.
Next, Compound GD-1 and Compound H-1 are co-evaporated at a deposition rate of 0.1 nm / second so that Compound GD-1 has a concentration of 9% by volume to form a green phosphorescent light emitting layer having a thickness of 18 nm. did.
Next, the compounds GD-1, RD-1, and H-1 were co-polymerized at a deposition rate of 0.1 nm / second so that the concentration of the compound GD-1 was 9% by volume and the concentration of the compound RD-1 was 2% by volume. Evaporation was performed to form a red phosphorescent light emitting layer having a thickness of 8 nm.
In the red phosphorescent light emitting layer, main light emission is brought about by the compound RD-1.
In the red phosphorescent light emitting layer, the compound RD-1 corresponds to a phosphorescent dopant that mainly emits light, and the compound GD-1 corresponds to a special phosphorescent metal complex.
In the red phosphorescent light emitting layer, the content of compound GD-1 is greater than the content of compound RD-1.
In the red phosphorescent light emitting layer, the value of T1 of compound GD-1 is larger than the value of T1 of compound RD-1, and smaller than the value of T1 of compound H-1.

Thereafter, compound HB-1 was deposited to a thickness of 10 nm at a deposition rate of 0.1 nm / second to form an exciton blocking layer, and then compound E-1 was deposited to a thickness of 25 nm at a deposition rate of 0.1 nm / second. Thus, an electron transport layer was formed.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 101, the non-light-emitting surface was covered with a glass case, and an “organic EL element 104” was produced.

(5) Production of Organic EL Element 105 In the same manner as the organic EL element 102, a blue fluorescent light emitting layer was provided.
Next, Compound AD-1, RD-1, and Compound H-1 were deposited at a deposition rate of 0.1 nm / second so that the concentration of Compound AD-1 was 7% by volume and the concentration of Compound RD-1 was 2% by volume. Co-evaporation was performed to form a red phosphorescent light emitting layer having a thickness of 5 nm.
In the red phosphorescent light emitting layer, main light emission is brought about by the compound RD-1.
In the red phosphorescent light emitting layer, the compound RD-1 corresponds to a phosphorescent dopant that mainly emits light, and the compound AD-1 corresponds to a special phosphorescent metal complex.
In the red phosphorescent light emitting layer, the content of compound AD-1 is greater than the content of compound RD-1.
In the red phosphorescent light emitting layer, the value of T1 of compound AD-1 is larger than the value of T1 of compound RD-1, and smaller than the value of T1 of compound H-1.
Next, Compound GD-1 and Compound H-1 are co-deposited at a deposition rate of 0.1 nm / second so that Compound GD-1 has a concentration of 9% by volume to form a green phosphorescent light emitting layer having a thickness of 30 nm. did.

Thereafter, compound HB-1 was deposited to a thickness of 10 nm at a deposition rate of 0.1 nm / second to form an exciton blocking layer, and then compound E-1 was deposited to a thickness of 25 nm at a deposition rate of 0.1 nm / second. Thus, an electron transport layer was formed.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 101, the non-light emitting surface was covered with a glass case, and an “organic EL element 105” was produced.

<< Evaluation of organic EL elements >>
(1) Measurement of power efficiency Using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing Co., Ltd.), by measuring the front luminance and luminance angle dependency of each organic EL element at room temperature, the substrate of the organic EL element The amount of light radiated from the front surface to the outside was measured, and the power efficiency of each organic EL element was determined from the amount of energization that gave 1000 cd / m ² and the drive voltage.
Table 1 shows the power efficiency of each of the organic EL elements as a relative value when the power efficiency of the organic EL element 101 is 100.

(2) Measurement of continuous driving luminance life Continuous driving was performed at room temperature under the driving condition giving the luminance of 5000 cd / m ² measured by the above method, and the time until the luminance decreased by 30% was determined as the driving life.
Table 1 shows the power efficiency of each organic EL element as a relative value when the driving life of the organic EL element 101 is 100.

(3) Evaluation of storage stability Each organic EL device produced as described above was stored (left) in a 60 ° C. environment for 300 hours, and when driven at 5 mA / cm ² , emission chromaticity before and after storage, The change in driving voltage was measured.
Table 1 shows the emission chromaticity of each organic EL element and the fluctuation range of the driving voltage as relative values when the fluctuation range of the organic EL element 101 is 100.
In addition, the fluctuation range of the emission chromaticity is the chromaticity coordinate between before and after storage in the CIE1931 color coordinate system of the front luminance of each organic EL element measured by a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing). It is calculated as a distance.

(4) Summary As shown in Table 1, the organic EL elements 103 to 105 of the present invention have improved power efficiency and light emission lifetime relative to the comparative organic EL elements 101 to 102, and also have storage stability. It was excellent.
In particular, the organic EL elements 103 and 105 in which a blue fluorescent light emitting layer, a red phosphorescent light emitting layer, and a green phosphorescent light emitting layer are laminated in this order from the anode side to the cathode side show better performance.
From the above, phosphorescence in which the blue fluorescent light emitting layer is formed on the anode side and the red phosphorescent light emitting layer has a higher content than the phosphorescent light emitting dopant (compound RD-1), and the lowest excited triplet energy is the main light emitting phosphorescence. Inclusion of a special phosphorescent metal complex (Compound GD-1 or Compound AD-1) that is larger than the luminescent dopant and smaller than the host compound (Compound H-1) is useful for at least improving power efficiency and luminescence lifetime. It can be seen that it is.

<< Production of organic EL element >>
(1) Production of Organic EL Element 201 The hole blocking layer was provided in the same manner as the organic EL element 103.
Next, the compounds E-1 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 17% by volume to form an electron transport layer having a thickness of 20 nm.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Thereafter, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case, and an "organic EL element 201" was produced.

(2) Production of Organic EL Element 202 Similarly to the organic EL element 103, the hole blocking layer was provided.
Next, the compounds E-1 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 17% by volume to form an electron transport layer having a thickness of 20 nm.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Thereafter, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case, and an "organic EL element 202" was produced.

(3) Preparation of organic EL element 203 It carried out similarly to the organic EL element 103, and provided to the hole-blocking layer.
Next, Compound E-1 and CsF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of CsF was 14% by volume to form an electron transport layer having a thickness of 20 nm.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Thereafter, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case to produce an "organic EL element 203".

(4) Preparation of organic EL element 204 It carried out similarly to the organic EL element 103, and provided to the hole-blocking layer.
Next, the compound E-1 and the 8-hydroxyquinoline lithium complex were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of the 8-hydroxyquinoline lithium complex was 30% by volume, and an electron transport layer having a thickness of 20 nm was formed. Formed.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Thereafter, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case, and an “organic EL element 204” was produced.

(5) Production of Organic EL Element 205 The hole blocking layer was provided in the same manner as the organic EL element 103.
Next, Compound E-2 was deposited to a thickness of 20 nm at a deposition rate of 0.1 nm / second to form an electron transport layer.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case, and an "organic EL element 205" was produced.

(6) Preparation of organic EL element 206 It carried out similarly to the organic EL element 103, and provided to the hole-blocking layer.
Next, the compounds E-2 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 17% by volume to form an electron transport layer having a thickness of 20 nm.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Thereafter, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case, and an "organic EL element 206" was produced.

(7) Production of Organic EL Element 207 The hole blocking layer was provided in the same manner as the organic EL element 103.
Next, Compound E-3 was deposited to a thickness of 20 nm at a deposition rate of 0.1 nm / second to form an electron transport layer.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case, and an “organic EL element 207” was produced.

(8) Production of Organic EL Element 208 The hole blocking layer was provided in the same manner as the organic EL element 103.
Next, Compound E-3 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 20% by volume to form an electron transport layer having a thickness of 20 nm.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Next, in the same manner as in the case of the organic EL element 103, the non-light emitting surface was covered with a glass case, and an “organic EL element 208” was produced.

(9) Production of Organic EL Element 209 The hole blocking layer was provided in the same manner as the organic EL element 103.
Next, Compound E-4 was deposited to a thickness of 20 nm at a deposition rate of 0.1 nm / second to form an electron transport layer.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 103, the non-light emitting surface was covered with a glass case, and an "organic EL element 209" was produced.

(10) Production of Organic EL Element 210 Similarly to the organic EL element 103, up to the hole blocking layer was provided.
Next, Compound E-4 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 20% by volume to form an electron transport layer having a thickness of 20 nm.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Next, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case to produce an "organic EL element 210".

(11) Production of Organic EL Element 211 Similarly to the organic EL element 103, up to the hole blocking layer was provided.
Subsequently, Compound E-5 was deposited at a film thickness of 20 nm at a deposition rate of 0.1 nm / second to form an electron transport layer.
Further, after KF was formed to a thickness of 2 nm, aluminum was deposited with a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 103, the non-light emitting surface was covered with a glass case, and an “organic EL element 211” was produced.

(12) Production of Organic EL Element 212 In the same manner as the organic EL element 103, a hole blocking layer was provided.
Next, Compound E-5 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 20% by volume to form an electron transport layer having a thickness of 20 nm.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Next, in the same manner as in the case of the organic EL element 103, the non-light emitting surface was covered with a glass case, and an organic EL element 212 was produced.

<< Evaluation of organic EL elements >>
(1) Evaluation of power efficiency, continuous drive brightness life and storage stability In the same manner as in Example 1, power efficiency, continuous drive brightness life and storage stability were evaluated. Table 2 shows relative values when each evaluation value of the organic EL element 103 is 100.

(2) Summary As shown in Table 2, an electron transport layer containing electron transport materials E-1, E-2, and E-3 having a phenylpyridine skeleton and doped with an alkali metal compound or an alkali metal organic complex is used. The organic EL elements 201 to 204, 206, 208 having the organic EL elements 103, 205, 207 not doped with the metal compound, and the electron transport materials E-4, E having no phenylpyridine skeleton in the molecule. It can be seen that the organic EL elements 209 to 212 containing -5 have favorable performance with small chromaticity fluctuation and voltage increase during storage.
In particular, it can be seen from the comparison between the organic EL elements 201 and 202 and the organic EL elements 203 and 204 that the organic EL element doped with K has good performance.
In addition, in the organic EL elements 209 to 212 containing the electron transport materials E-4 and E-5 that do not have a phenylpyridine skeleton in the molecule, the metal compound is almost doped with chromaticity and voltage during storage. It can be seen that there is no effect of suppressing fluctuation.

<< Production of organic EL element >>
(1) Preparation of organic EL element 301 It carried out similarly to the organic EL element 103, and provided to the electron carrying layer.
Next, after forming LiF to a thickness of 1.5 nm, aluminum was deposited to have a thickness of 110 nm to form a cathode.
Next, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case to produce an "organic EL element 301".

(2) Production of Organic EL Element 302 Similarly to the organic EL element 103, the hole blocking layer was provided.
Next, the compound E-1 and LiF were co-evaporated at a deposition rate of 0.1 nm / second so that the LiF concentration was 20% by volume to form an electron transport layer having a thickness of 20 nm.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Thereafter, in the same manner as in the case of the organic EL element 103, the non-light emitting surface was covered with a glass case, and an "organic EL element 302" was produced.

<< Evaluation of organic EL elements >>
(1) Evaluation of power efficiency, continuous drive brightness life and storage stability In the same manner as in Example 1, power efficiency, continuous drive brightness life and storage stability were evaluated. Table 3 shows relative values when each evaluation value of the organic EL element 301 is 100.

(2) Summary As shown in Table 3, it can be seen that even when LiF is used as the doping material of the electron transport layer, the chromaticity variation and voltage increase during storage are reduced.
However, compared with the result of Example 2, the effect is smaller than when KF is used as the doping material.

<< Production of organic EL element >>
(1) Production of Organic EL Element 401 Similar to the organic EL element 201, the green phosphorescent light emitting layer was provided.
Thereafter, compounds HB-1 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 17% by volume to form an exciton blocking layer having a thickness of 10 nm. 1 and KF were co-evaporated at a deposition rate of 0.1 nm / second so that the concentration of KF was 17% by volume to form an electron transport layer having a thickness of 35 nm.
Subsequently, aluminum 110nm was vapor-deposited and the cathode was formed.
Next, in the same manner as in the case of the organic EL element 103, the non-light-emitting surface was covered with a glass case to produce an "organic EL element 401".

<< Evaluation of organic EL elements >>
(1) Evaluation of power efficiency, continuous drive brightness life and storage stability In the same manner as in Example 1, power efficiency, continuous drive brightness life and storage stability were evaluated. Table 4 shows relative values when each evaluation value of the organic EL element 201 is 100.

(2) Summary As shown in Table 4, although the organic EL element 401 doped with KF in the hole blocking layer has no difference in power efficiency compared to the organic EL element 201 not doped with KF, the luminance life is slightly higher. It can be seen that the chromaticity variation and the voltage increase during storage are large. From this result, it can be seen that better performance can be obtained when the exciton blocking layer does not contain a metal compound.

  The present invention can be particularly suitably used for obtaining white light emission excellent in power efficiency and light emission lifetime.

DESCRIPTION OF SYMBOLS 101 Organic EL element 102 Glass cover 105 Cathode 106 Organic EL layer 107 Glass substrate with a transparent electrode 108 Nitrogen gas 109 Water catching agent

Claims (4)

In an organic electroluminescence device comprising an anode, a cathode, and a plurality of light emitting layers, wherein the plurality of light emitting layers are disposed between the anode and the cathode,
The plurality of light emitting layers have a fluorescent light emitting layer and at least two or more phosphorescent light emitting layers,
Of the fluorescent light emitting layer and the phosphorescent light emitting layer, the fluorescent light emitting layer is disposed on the anode side,
Each layer of the phosphorescent layer contains a phosphorescent dopant and a host compound,
Among the phosphorescent light emitting layers, the phosphorescent light emitting layer having the longest emission wavelength is disposed on the fluorescent light emitting layer side, and
The phosphorescent light emitting layer having the longest emission wavelength has a content higher than that of the main phosphorescent light emitting dopant of the layer, and the lowest excited triplet energy T1 is larger than T1 of the main phosphorescent light emitting dopant of the layer. An organic electroluminescence device comprising a phosphorescent metal complex smaller than T1 of the compound. The organic electroluminescent device according to claim 1,
An electron transport layer is formed between the light emitting layer and the cathode,
The organic electroluminescence device, wherein the electron transport layer contains a compound having a phenylpyridine skeleton and is doped with at least one of an electron donating metal, a metal ion, or a metal compound. The organic electroluminescent device according to claim 1,
An electron transport layer is formed between the light emitting layer and the cathode,
An exciton or hole blocking layer is formed between the light emitting layer and the electron transport layer,
The electron transport layer contains a compound having a phenylpyridine skeleton, and is doped with at least one of an electron donating metal, a metal ion, or a metal compound,
The organic electroluminescence device, wherein the exciton or hole blocking layer is not doped with any of the electron donating metal, metal ion or metal compound. In the organic electroluminescent element as described in any one of Claims 1-3,
The fluorescent light emitting layer is composed of a blue fluorescent light emitting layer containing a blue fluorescent light emitting dopant,
The phosphorescence layer is composed of a red phosphorescence layer containing a red phosphorescence dopant and a green phosphorescence layer containing a green phosphorescence dopant,
An organic electroluminescence element, wherein the blue fluorescent light emitting layer, the red phosphorescent light emitting layer, and the green phosphorescent light emitting layer are laminated in this order from the anode side to the cathode side.

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