WO2009116414A1

WO2009116414A1 - Organic electroluminescence element

Info

Publication number: WO2009116414A1
Application number: PCT/JP2009/054405
Authority: WO
Inventors: 邦雅檜山; 充良内藤
Original assignee: コニカミノルタホールディングス株式会社
Priority date: 2008-03-19
Filing date: 2009-03-09
Publication date: 2009-09-24
Also published as: JPWO2009116414A1

Abstract

Provided is an organic electroluminescence element, which has improved white light emitting efficiency, and furthermore, can be manufactured even by a simple process such as a wet process. The organic electroluminescence element has, on a substrate, at least an anode, a cathode, a light emitting layer sandwiched by the anode and the cathode, and a hole transport layer, and the color of light emitted from the element is white. The light emitting layer contains at least phosphorescent dopant of two types or more having different λmax values, and an intermediate layer is arranged between the light emitting layer and the hole transport layer.

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescence element. Specifically, an organic electroluminescence device with improved white light emission efficiency. Furthermore, the present invention relates to an organic electroluminescent device that can be manufactured by a simple process such as a wet process.

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

On the other hand, an organic electroluminescence device has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and excitons (excitons) by injecting electrons and holes into the light emitting layer and recombining them. This is a device that emits light by utilizing light emission (fluorescence / phosphorescence) when the exciton is deactivated. Light emission is possible at a voltage of several volts to several tens of volts. Furthermore, since it is a self-luminous type, it has a wide viewing angle and high visibility. It is attracting attention from the viewpoint.

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

Improvement of luminous efficiency is mentioned as a problem for putting an organic electroluminescence element into practical use as such a light source for illumination or a backlight of a display. Luminous efficiency is greatly related to the energy relationship between the light-emitting layer constituting the organic electroluminescence element and the adjacent hole transport layer. A technique for providing a mixed layer in which respective components are continuously mixed between two different layers is disclosed (for example, see Patent Document 1). This is effective for relaxing the injection barrier between the layers, but if such a mixed layer exists between the phosphorescent light emitting layer and the hole transport layer, the excitation energy of the phosphorescent material is transferred to the hole transport material. As a result, the luminous efficiency may be reduced. In particular, when a light emitting layer containing a blue phosphorescent light emitting material having a high triplet excitation energy is used, the tendency is remarkable. Further, a blue light emitting material, a green phosphorescent light emitting material, a red phosphorescent light emitting material, etc. are mixed to form a white light emitting layer. In the case of forming, green and red light emission is considered to be caused by energy transfer from the blue light emitting material. When energy transfer occurs in the hole transport material of the mixed layer, not only the light emission efficiency is lowered, but also the white chromaticity is destabilized.

On the other hand, a technique for controlling the mixing of a hole transport layer and a light emitting layer by using a reactive organic compound as a hole transport material to form a three-dimensional crosslinked film is disclosed (for example, see Patent Document 2). Although leakage of excitation energy to the hole transport material is suppressed to some extent by this technique, the effect is not sufficient particularly in combination with a white phosphorescent light emitting layer. This is probably because the interface between the hole transport layer and the light emitting layer is disturbed due to factors such as film shrinkage when forming the three-dimensional cured film, resulting in a state close to interlayer mixing.
JP 2007-42312 A Japanese Patent No. 3157589

The present invention has been made in view of the above problems, and its object is to provide an organic electroluminescent device with improved white light emission efficiency, and further an organic electroluminescent device that can be manufactured by a simple process such as a wet process. It is to provide.

The above object of the present invention can be achieved by the following configuration.

1. In an organic electroluminescent device having at least an anode, a cathode, a light emitting layer sandwiched between the anode and the cathode, and a hole transport layer on a substrate, and the resulting light emitting color is white, the light emitting layer is at least λmax An organic electroluminescence device comprising two or more types of phosphorescent dopants different from each other and an intermediate layer provided between the light emitting layer and the hole transport layer.

2. The lowest excited triplet energy (T _I ) of the material constituting the intermediate layer and the lowest excited triplet energy (T _H ) of the material constituting the hole transport layer are in a relationship represented by the following formula: 2. The organic electroluminescence device as described in 1 above.

T _I > T _H
3. The lowest excited triplet energy (T _I ) of the material constituting the intermediate layer, the lowest excited triplet energy (T _H ) of the material constituting the hole transport layer, and λmax having the shortest wavelength among the light emitting layers. 2. The organic electroluminescence device as described in 1 above, wherein the excited triplet energy (T _L ) of the phosphorescent dopant has a relationship satisfying the following formula.

T _I > T _H
T _I > T _L
4). 4. The organic electroluminescence device according to any one of 1 to 3, wherein the light emitting layer is formed by a wet process.

5. The material constituting the hole transport layer is an organic compound having the following reactive group, and is a material that is polymerized by energy applied from the outside after film formation and becomes insoluble in an organic solvent. 5. The organic electroluminescence device according to any one of 4 above.

6. 6. The organic electroluminescence device as described in 5 above, wherein the external energy source is ultraviolet light.

7. 7. The organic electroluminescence device as described in 5 or 6 above, wherein the organic compound having a reactive group is a compound represented by the following general formula (1).

(In the formula, Ar ₁ to Ar ₅ represent a substituted or unsubstituted phenyl group or naphthyl group. At least one of Ar ₁ to Ar ₅ has the following reactive group. N represents an integer of 1 or 2. )

8. 8. The organic electroluminescence device according to any one of 1 to 7, wherein the material constituting the intermediate layer is a compound represented by the following general formula (2).

(In the formula, X represents O, S or NR ₀ , and R ₀ to R _{8 each} represents a hydrogen atom or an optionally substituted alkyl group, aryl group or heteroaryl group, provided that either At least one of the following reactive groups at the site:

9. 8. The organic electroluminescence device according to any one of 1 to 7, wherein the material constituting the intermediate layer is a compound represented by the following general formula (3).

(In the formula, Z ₁ and Z ₂ represent a nonmetallic atom group necessary for forming a 5- to 7-membered ring. L ₁ represents an atomic group forming a bidentate ligand together with X ₁ and X _2. M1 represents an integer of 1, 2 or 3, m2 represents an integer of 0, 1 or 2, and m1 + m2 is 2 or 3. In addition, at least one of the following reactive groups is present at any position in the formula: I have one.)

According to the present invention, it was possible to provide an organic electroluminescence device having improved white light emission efficiency and capable of being manufactured by a simple process such as a wet process.

The present invention will be described in more detail. Hereinafter, the detail of each component of the organic electroluminescent element of this invention is demonstrated sequentially.

<< Layer structure of organic EL element >>
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 / hole transport layer / intermediate layer / light emitting layer unit / electron transport layer / cathode (ii) Anode / hole transport layer / intermediate layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode iii) Anode / hole transport layer / intermediate layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode (iv) Anode / anode buffer layer / hole transport layer / intermediate layer / light emitting layer unit / Hole blocking layer / electron transport layer / cathode buffer layer / cathode << 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 film thickness of the light emitting layer is not particularly limited, but it is 2 from the viewpoint of 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 drive current. It is preferable to adjust to a range of ˜200 nm, and more preferably to a range of 5 nm or more and 100 nm or less.

The light emitting layer of the organic electroluminescence element according to claim 4 of the present invention is formed by a wet process. As a known wet process coating method, there are a spin coating method, a casting method, an ink jet method, a spray method, a printing method, etc., but from the point that a homogeneous film is easily obtained and pinholes are difficult to generate, etc. In the present invention, film formation by a coating method such as a spin coating method, an ink jet method, a spray method, or a printing method is preferable.

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

(Host compound (also called luminescent host))
The host compound used in the present invention will be described.

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

As the host compound, known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the efficiency of the organic EL element can be increased. Moreover, it becomes possible to mix different light emission by using multiple types of light emission dopants mentioned later, and, thereby, arbitrary luminescent colors can be obtained.

In addition, the light emitting host used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (evaporation polymerization light emission). Host).

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

Specific examples of known host compounds include compounds described in the following documents.

JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002 -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

(Luminescent dopant)
The light emitting dopant according to the present invention will be described. As the light emitting dopant according to the present invention, a phosphorescent dopant is used from the viewpoint of obtaining an organic EL device having higher light emission efficiency.

(Phosphorescent dopant)
The phosphorescent dopant according to the present invention will be described. The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, the phosphorescent dopant is a compound that emits phosphorescence at room temperature (25 ° C.), and the phosphorescence quantum yield is 25 ° C. It is a compound of 0.01 or more, and a preferable phosphorescence quantum yield is 0.1 or more.

In the present invention, the light emitting layer contains two or more phosphorescent dopants having different λmax.

The phosphorescent quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of the Fourth Edition Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

The lowest excited triplet energy of the phosphorescent dopant can be determined from the rising wavelength on the short wavelength side of the phosphorescent spectrum by measuring the phosphorescent spectrum of the phosphorescent dopant. In the invention according to claim 3, the lowest excited triplet energy of the phosphorescent dopant having the shortest wave length of λmax among the light emitting layers is smaller than the lowest excited triplet energy of the intermediate layer material.

There are two types of light emission of phosphorescent dopants in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent dopant. Energy transfer type to obtain light emission from the phosphorescent dopant, and the other is that the phosphorescent dopant becomes a carrier trap, carrier recombination occurs on the phosphorescent dopant, and light emission from the phosphorescent dopant is obtained. It is a trap type. In any case, it is a condition that the excited state energy of the phosphorescent dopant is lower than the excited state energy of the host compound.

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

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 compound). Rare earth complexes, most preferably iridium compounds.

Next, an intermediate layer used as a constituent layer of the organic EL element of the present invention will be described.

《Middle layer》
The intermediate layer in the organic EL device of the present invention is provided between the hole transport layer and the light emitting layer, and a known material having a hole transport property can be used as the intermediate layer material. For the intermediate layer, the same material as the hole transport layer may be used again for the purpose of alleviating the interface disturbance between the hole transport layer and the light emitting layer, but a material having a high minimum excited triplet energy is used for the intermediate layer. It is preferable to use it for the purpose of preventing the transfer of excitation energy from the light emitting layer.

The lowest excited triplet energy level of each material was determined from the rising wavelength on the short wave side of the phosphorescence spectrum by measuring the phosphorescence spectrum of each material. In the invention according to claim 2, the lowest excited triplet energy of the intermediate layer material is larger than the lowest excited triplet energy of the hole transport material. In the invention according to claim 3, the lowest excited triplet energy of the intermediate layer material is larger than the lowest excited triplet energy of the hole transport material, and among the light emitting layers, λmax is the short-wave phosphorescent dopant. Greater than lowest excited triplet energy.

Hereinafter, specific examples of the compounds represented by the general formulas (2) and (3) used as the intermediate layer material according to claims 8 and 9 are shown, but the present invention is not limited thereto.

Next, an injection layer, a blocking layer, an electron transport layer, and the like used as a constituent layer of the organic EL element of the present invention will be described.

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

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

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

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

<Blocking layer: hole blocking layer, electron blocking layer>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258 and 11-204359, and “Organic EL elements and their forefront of industrialization” (issued by NTS 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. By preventing this, the recombination probability of electrons and holes can be improved. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

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

The hole blocking layer preferably contains the azacarbazole derivative mentioned as the host compound described above.

In the present invention, when a plurality of light emitting layers having different light emission colors are provided, the light emitting layer having the shortest wavelength of light emission is preferably closest to the anode among all the light emitting layers. In this case, it is preferable to additionally provide a hole blocking layer between the shortest wave layer and the light emitting layer next to the anode next to the anode. Furthermore, it is preferable that 50% by mass or more of the compound contained in the hole blocking layer provided at the position has an ionization potential of 0.3 eV or more larger than the host compound of the shortest wave emitting layer.

The ionization potential is defined by the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of the compound to the vacuum level, and can be determined by, for example, the following method.

(1) Gaussian 98 (Gaussian 98, Revision A.11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), a molecular orbital calculation software manufactured by Gaussian, USA, is used as a keyword. The ionization potential can be obtained as a value obtained by rounding off the second decimal place of a value (eV unit converted value) calculated by performing structural optimization using B3LYP / 6-31G *. This calculation value is effective because the correlation between the calculation value obtained by this method and the experimental value is high.

(2) The ionization potential can also be obtained by a method of directly measuring by photoelectron spectroscopy. For example, a low energy electron spectrometer “Model AC-1” manufactured by Riken Keiki Co., Ltd. or a method known as ultraviolet photoelectron spectroscopy can be suitably used.

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. By blocking, the recombination probability of electrons and holes can be improved. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The film thickness of the hole blocking layer and the electron transporting layer according to the present invention is preferably 3 to 100 nm, more preferably 5 to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, 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 either hole injection or transport or 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 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 ' Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino -(2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and also two described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 are linked in a starburst type ( MTDATA) and the like.

Further, 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.

Also, JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used.

In the present invention, the material constituting the hole transport layer is preferably an organic compound having the reactive group. Specifically, it is a compound shown by the said General formula (1), The specific example is shown below.

The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. The thickness of the hole transport layer is not particularly limited, but is usually about 5 nm to 5 μm, preferably 5 to 200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

It is also possible to use a hole transport layer having a high p property doped with impurities. Examples thereof include JP-A-4-297076, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

In the present invention, it is preferable to use a hole transport layer having such a high p property because a device with lower power consumption can be produced.

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

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. Further, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and like the hole injection layer and the hole transport layer, inorganic semiconductors such as n-type-Si and n-type-SiC Can also be used as an electron transporting material.

The electron transport layer can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. The thickness of the electron transport layer is not particularly limited, but is usually about 5 nm to 5 μm, preferably 5 to 200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

In the present invention, an n-type electron transport layer doped with impurities may be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

In the present invention, it is preferable to use an electron transport layer having such a high n property because an element with lower power consumption can be produced.

<< Organic compound having a reactive group >>
In the present invention, an organic compound having a reactive group is preferably used for the hole transport layer and the intermediate layer, but the layer to be used is not particularly limited, and can be used for each layer.

An organic compound having a reactive group can be reacted on a substrate to form a network polymer of organic molecules. Generation | occurrence | production of a network polymer can suppress element deterioration by Tg (glass transition point) adjustment of a structure layer.

It is also possible to change the emission wavelength of the organic EL element, suppress deterioration of the specific wavelength, etc. by adjusting the reaction accompanied by the cleavage or generation of the conjugated system of the molecule using the active radical in use. is there.

On the other hand, on the manufacturing side, for example, in the case of the step of laminating by coating, it is preferable that the lower layer is not dissolved in the upper layer coating solution, and the upper layer can be applied by making the lower layer resin and degrading solvent solubility. Can do.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode substances include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) that can form a transparent conductive film may be used. For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
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, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the emission luminance is advantageously improved.

In addition, a transparent or semi-transparent cathode can be produced by producing the conductive transparent material mentioned in the description of the anode on the cathode after producing the metal with a film thickness of 1 to 20 nm. By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

《Support substrate》
As a support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention, there is no particular limitation on the type of glass, plastic, etc., and it is transparent. 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, polysulfone , Polyetherimide, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, and cycloolefin resins such as ARTON (manufactured by JSR) or APEL (manufactured by Mitsui Chemicals).

An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film, and it is preferably a barrier film having a water vapor permeability of 0.01 g / m ² / day · atm or less. Furthermore, a high barrier film having an oxygen permeability of 10 ⁻³ g / m ² / day or less and a water vapor permeability of 10 ⁻⁵ g / m ² / day or less is preferable.

The material for forming the barrier film may be any material that has a function of suppressing the 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 organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

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

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

The external extraction quantum efficiency at room temperature of light emission of the organic EL device of the present invention is preferably 1% or more, more preferably 5% or more. Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.

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

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

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

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

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned. Furthermore, the polymer film, measured oxygen permeability by the method based on JIS K 7126-1987 is ^{^{1 × 10 -3 ml / m 2}} / 24h or less, as measured by the method based on JIS K 7129-1992 water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is preferably that of ^{1 × 10 -3 g / (m} 2 / 24h) 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 reactive vinyl groups of acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.

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

In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . In this case, the material for forming the film may be a material having a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can. Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. The method for forming these films is not particularly limited. For example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, 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 can be injected in the gas phase and liquid phase. preferable. 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 perchloric acid) Barium, magnesium perchlorate, and the like), and anhydrous salts are preferably used in sulfates, metal halides, and perchloric acids.

《Protective film, protective plate》
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided on the outer side of the sealing film on the side facing the support substrate with the organic layer interposed therebetween or on the sealing film. In particular, when the sealing is performed by the sealing film, the mechanical strength is not necessarily high, 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, and the like used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

《Light extraction》
The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1) and can extract only about 15% to 20% of the light generated in the light emitting layer. It is generally said. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because the light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the element side surface.

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

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

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

When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the efficiency of taking out the light from the transparent electrode to the outside increases as the refractive index of the medium decreases.

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. Further, it is preferably 1.35 or less.

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

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

As described above, the position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated.

At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium.

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

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

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

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

Further, in order to control the light emission angle from the light emitting element, a light diffusion plate / film may be used in combination with the light collecting sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<< 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 / electron transport layer / electron injection 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 substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm, thereby producing an anode.

Next, organic compound thin films of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer, which are organic EL element materials, are formed thereon.

The light emitting layer of the organic EL device of the present invention is formed by a wet process as described above. As a method for forming an organic layer other than the light emitting layer, there are a vapor deposition method, a wet process (spin coating method, casting method, ink jet method, spray method, printing method), etc., but a homogeneous film can be easily obtained and a pinhole is used. In the present invention, a part or all of the organic layer is preferably formed by a coating method such as a spin coating method, an ink jet method, a spray method, or a printing method.

Examples of the liquid medium for dissolving or dispersing the organic EL material according to the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, and mesitylene. Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used. Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.

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 to 200 nm. By providing, a desired organic EL element can be obtained.

It is also possible to reverse the production order to produce a cathode, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an 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 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Production of organic EL element >>
[Production of Organic EL Element 101]
After patterning an ITO (indium tin oxide) 100 nm film-formed substrate (NH Technoglass NA45) on a 100 mm × 100 mm × 1.1 mm glass substrate as an anode, the substrate provided with this ITO transparent electrode was isopropyl. Ultrasonic cleaning with alcohol, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes. On this substrate, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, manufactured by HC Starlk, Baytron P AI 4083) to 70% with pure water, 3000 rpm, 30 After forming a film by spin coating in seconds, the film was dried at 200 ° C. for 1 hour to provide a hole injection layer having a thickness of 30 nm.

This substrate was transferred to a nitrogen atmosphere, and a solution prepared by dissolving 50 mg of Exemplified Compound 1-8 in 10 ml of toluene on the hole injection layer was formed by spin coating under a condition of 1500 rpm for 30 seconds (film thickness of about 20 nm). The film was irradiated with ultraviolet light for 60 seconds and then heated and dried at 120 ° C. for 30 minutes to form a hole transport layer.

Further, a solution obtained by dissolving 30 mg of Exemplified Compound 2-11 in 10 ml of toluene on the hole transport layer was formed into a film (thickness: about 20 nm) by spin coating under the condition of 1000 rpm for 30 seconds. After second irradiation, it was dried at 120 ° C. for 30 minutes to form an intermediate layer.

This substrate is fixed to the substrate holder of the vacuum evaporation system, while HA, Ir-A, Ir (ppy) ₃ , Ir (piq) ₃ , ET-A, and CsF are respectively attached to six molybdenum resistance superheated boats. And attached to a vacuum deposition apparatus. After depressurizing the vacuum tank to 4 × 10 ⁻⁴ Pa, first, the heated boat containing HA, the boat containing Ir-A, the boat containing Ir (ppy) ₃ and the Ir (piq) ₃ The entrained boats were energized independently, and the deposition rate of HA as the light emitting host and Ir-A, Ir (ppy) ₃ and Ir (piq) _{3 as} the light emitting dopant was 100: 10: 0.2: The light emitting layer was provided by adjusting the film thickness to 0.2 so that the film thickness was 40 nm. The phosphorescent dopant having the shortest λmax in this light emitting layer is Ir-A, and the value of the lowest excited triplet energy (T _L ) obtained from the short wavelength rising wavelength of the phosphorescence spectrum was 2.8 eV. . Further, the heating boat containing ET-A and CsF was energized and heated, and deposited on the light-emitting layer at a deposition rate of 0.2 nm / second and 0.03 nm / second, respectively, and a film thickness of 40 nm was further obtained. An electron transport layer was provided. Subsequently, 110 nm of aluminum was vapor-deposited to form a cathode, and an organic EL element 101 was produced.

[Production of organic EL elements 102 to 108]
In the production of the organic EL element 101, organic EL elements 102 to 108 were produced in the same manner except that the intermediate layer composition and the light emitting layer configuration were changed as shown in Table 1. The values of the lowest excited triplet energy of the intermediate layer material and hole transport layer material used are as shown in Table 1.

<< Evaluation of organic EL elements >>
About the produced organic EL element, external extraction quantum efficiency and white chromaticity stability were evaluated as follows.

[External extraction quantum efficiency]
With respect to the produced organic EL element, the external extraction quantum efficiency (%) when a ^2.5 mA / cm ² constant current was passed was measured. For the measurement, a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) was used. The obtained results are shown in Table 1 as relative values when the measured value of the organic EL element 107 (comparative) is 100.

[White chromaticity stability]
CIE 1931 chromaticity coordinates x and y when a ^2.5 mA / cm ² constant current is applied to the produced organic EL element are CIE chromaticity when x ( _a ) and y ( _a ) and 10 mA / cm ² , respectively. x, respectively y x _(b), as y _(b), color variation _{Δxy = ((x (a)} -x (b)) 2 + (y (a) -y (b)) 2) 1/2 The color variation was defined as follows, and the color stability was evaluated according to the following criteria. The color variation is preferably less than 0.05, depending on the intended use. For the measurement, a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) was used.

A: Δxy is less than 0.001 B: Δxy is 0.001 or more and less than 0.01 C: Δxy is 0.01 or more and less than 0.05 D: Δxy is 0.05 or more Evaluation results are shown in Table 1. .

In Table 1 below, T _L and λmax are as follows. Here, the shortest-wavelength phosphorescent dopant of λmax is Ir-A. Accordingly, the lowest excited triplet energy (T _L ) of the shortest phosphorescent dopant of λmax is 2.8 eV.

H−A T _L = 2.9 eV
Ir-A T _L = 2.8 eV λmax = 472 nm
Ir (ppy) ₃ T _L = 2.6 eV λmax = 518 nm
Ir (piq) ₃ T _L = 2.4 eV λmax = 622 nm

Table 1 shows that the organic EL device of the present invention has excellent luminous efficiency and improved white chromaticity stability.

Example 2
<< Production of organic EL element >>
[Production of Organic EL Element 201]
After patterning an ITO (indium tin oxide) 100 nm film-formed substrate (NH Technoglass NA45) on a 100 mm × 100 mm × 1.1 mm glass substrate as an anode, the substrate provided with this ITO transparent electrode was isopropyl. Ultrasonic cleaning with alcohol, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes. On this substrate, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, manufactured by HC Starlk, Baytron P AI 4083) to 70% with pure water, 3000 rpm, 30 After forming a film by spin coating in seconds, the film was dried at 200 ° C. for 1 hour to provide a hole injection layer having a thickness of 30 nm.

Further, a solution of 30 mg of Exemplified Compound 2-11 dissolved in 10 ml of toluene on the hole transport layer was formed into a film by spin coating (film thickness: about 20 nm) under the condition of 1000 rpm for 30 seconds, and ultraviolet light was applied. After irradiation for 30 seconds, the film was dried at 120 ° C. for 30 minutes to form an intermediate layer.

Next, a light emitting layer composition having the following composition was formed by spin coating (film thickness: about 40 nm) under the condition of 2000 rpm for 30 seconds, and then dried at 120 ° C. for 30 minutes to obtain a light emitting layer.

(Light emitting layer composition)
Toluene 10ml
HA 100mg
Ir-A 10mg
Ir (ppy) ₃ 0.2 mg
Ir (piq) ₃ 0.2 mg
This substrate was fixed to a substrate holder of a vacuum deposition apparatus, while 200 mg of ET-A was placed in a molybdenum resistance heating boat, and 100 mg of CsF was placed in another molybdenum resistance heating boat and attached to the vacuum deposition apparatus. The vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, and then heated by energizing the heating boat containing ET-A and CsF, and the light emitting layer was deposited at a deposition rate of 0.2 nm / second and 0.03 nm / second, respectively. An electron transport layer having a film thickness of 40 nm was further provided. Subsequently, 110 nm of aluminum was deposited to form a cathode, and an organic EL element 201 was produced.

[Production of organic EL elements 202 to 207]
Organic EL elements 202 to 207 were prepared in the same manner as in the preparation of the organic EL element 201 except that the intermediate layer composition and the light emitting layer configuration were changed as shown in Table 2.

<< Evaluation of organic EL elements >>
About the produced organic EL element, it carried out similarly to Example 1, and evaluated the external extraction quantum efficiency and white chromaticity stability. The results are shown in Table 2. In Table 2, the external extraction quantum efficiency is shown as a relative value when the organic EL element 205 (comparison) is 100.

In Table 2, _TL and λmax of HA, Ir-A, Ir (ppy) ₃ , and Ir (piq) ₃ are as described above.

Table 2 shows that the organic EL device of the present invention has excellent luminous efficiency and improved white chromaticity stability even when the light emitting layer is formed by a wet process.

Claims

In an organic electroluminescent device having at least an anode, a cathode, a light emitting layer sandwiched between the anode and the cathode, and a hole transport layer on a substrate, and the resulting light emitting color is white, the light emitting layer is at least λmax An organic electroluminescence device comprising two or more types of phosphorescent dopants different from each other and an intermediate layer provided between the light emitting layer and the hole transport layer.
The lowest excited triplet energy (T I ) of the material constituting the intermediate layer and the lowest excited triplet energy (T H ) of the material constituting the hole transport layer are in a relationship represented by the following formula: The organic electroluminescence device according to claim 1.
T I > T H
The lowest excited triplet energy (T I ) of the material constituting the intermediate layer, the lowest excited triplet energy (T H ) of the material constituting the hole transport layer, and λmax having the shortest wavelength among the light emitting layers. 2. The organic electroluminescence device according to claim 1, wherein the excited triplet energy (T L ) of the phosphorescent dopant is in a relationship satisfying the following formula.
T I > T H
T I > T L
The organic electroluminescence device according to any one of claims 1 to 3, wherein the light emitting layer is formed by a wet process.
The material constituting the hole transport layer is an organic compound having the following reactive group, which is a material that is polymerized by energy applied from the outside after film formation and becomes insoluble in an organic solvent. 5. The organic electroluminescence device according to any one of items 1 to 4.
6. The organic electroluminescence device according to claim 5, wherein the external energy source is ultraviolet light.
The organic electroluminescent element according to claim 5 or 6, wherein the organic compound having a reactive group is a compound represented by the following general formula (1).

(In the formula, Ar 1 to Ar 5 represent a substituted or unsubstituted phenyl group or naphthyl group. At least one of Ar 1 to Ar 5 has the following reactive group. N represents an integer of 1 or 2. )
The organic electroluminescent element according to any one of claims 1 to 7, wherein the material constituting the intermediate layer is a compound represented by the following general formula (2).

(In the formula, X represents O, S or NR 0 , and R 0 to R 8 each represents a hydrogen atom or an optionally substituted alkyl group, aryl group or heteroaryl group, provided that either At least one of the following reactive groups at the site:
The organic electroluminescent element according to any one of claims 1 to 7, wherein the material constituting the intermediate layer is a compound represented by the following general formula (3).

(In the formula, Z 1 and Z 2 represent a nonmetallic atom group necessary for forming a 5- to 7-membered ring. L 1 represents an atomic group forming a bidentate ligand together with X 1 and X 2. M1 represents an integer of 1, 2 or 3, m2 represents an integer of 0, 1 or 2, and m1 + m2 is 2 or 3. In addition, at least one of the following reactive groups is present at any position in the formula: I have one.)