WO2018221173A1

WO2018221173A1 - Organic electroluminescent element, display device, and lighting device

Info

Publication number: WO2018221173A1
Application number: PCT/JP2018/018451
Authority: WO
Inventors: 小林　史明; 秀雄 ▲高▼; 鈴木　隆嗣; 一成多田; 卓史波多野
Original assignee: コニカミノルタ株式会社
Priority date: 2017-06-02
Filing date: 2018-05-14
Publication date: 2018-12-06
Also published as: JPWO2018221173A1

Abstract

The present invention provides an organic EL electroluminescent element having at least a hole injection layer and a light emitting layer laminated between a pair of electrodes, wherein the hole injection layer contains zinc sulfide, the light emitting layer is directly laminated on the hole injection layer, the light emitting layer contains an organic compound interacting with said zinc sulfide, and the density of the light emitting layer is in the range of 1.0-1.8 g/cm³.

Description

Organic electroluminescence element, display device and lighting device

The present invention relates to an organic electroluminescence element, a display device, and a lighting device, and in particular, an organic electroluminescence element that can improve the density of a light emitting layer, improve luminous efficiency and element lifetime, and is easy to manufacture, and the organic The present invention relates to a display device and an illumination device including an electroluminescence element.

There is an organic electroluminescence (hereinafter, also referred to as “EL”) element as a light-emitting electronic display device.

An organic EL element has a structure in which a light-emitting layer containing a compound that emits light (hereinafter also referred to as “light-emitting material”) is sandwiched between a cathode and an anode, and recombines by injecting electrons and holes into the light-emitting layer. This is an element that generates excitons (excitons) by light emission, and emits light by utilizing light emission (fluorescence / phosphorescence) when the excitons are deactivated. Such an organic EL element can emit light at a low voltage of several V to several tens V, and further has a wide viewing angle and high visibility because it is a self-luminous type. In addition, since the organic EL element is a thin-film type complete solid-state element, it has attracted attention from the viewpoints of space saving and portability.

As an organic EL element development in the future, an organic EL element capable of emitting light with better luminous efficiency, luminance and chromaticity is desired.

Incidentally, in recent years, there has been a demand for production of an organic EL element having a simpler layer structure. Therefore, in the case of an organic EL element having an electrode / organic layer / light emitting layer structure in which an organic layer using an organic material is laminated on an electrode and a light emitting layer is laminated on the organic layer, there is a problem in electronic durability. Therefore, the desired device life cannot be obtained. In addition, since an organic material is used for the layer directly adjacent to the light emitting layer, there is a problem that the choice of the solvent for the light emitting layer is narrowed.

Therefore, in order to broaden the choice of solvent for the light emitting layer, an organic EL element (for example, see Patent Document 1) using zinc sulfide (ZnS), which is an inorganic material, as a hole injection layer, an electron transport layer, and a protective layer An organic EL element used in the above has been proposed (see, for example, Patent Documents 2 and 3).

However, in Patent Document 1 above, zinc sulfide is used for the hole injection layer. However, the element evaluation is performed as an organic EL element using NPD as the hole transport layer between the hole injection layer and the light emitting layer. Is going. Therefore, detailed investigations have been made on the evaluation of the element lifetime and the like in a layer configuration in which electrodes / zinc sulfide / light-emitting layers are stacked in this order (that is, a configuration in which a light-emitting layer is directly stacked on a layer containing zinc sulfide). Not.

Further, the above Patent Documents 2 and 3 only describe that the use of zinc sulfide for the electron transport layer can improve the electron injection property and the response speed.

Japanese Patent No. 6041336 JP 2000-215984 A JP 2008-277799 A

The present invention has been made in view of the above problems and situations, and a solution to that problem is to improve the density of the light emitting layer, improve the light emission efficiency and the device life, and can be easily manufactured. It is providing the luminescent element, the display apparatus and illuminating device which were equipped with the said organic electroluminescent element.

In order to solve the above problems, the present inventor, in the process of examining the cause of the above problems, by directly laminating the light emitting layer on the layer containing zinc sulfide, the density of the light emitting layer is improved, The present inventors have found that an organic electroluminescence device and the like that can improve the light emission efficiency and the device life and can be easily manufactured can be provided.

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

1. An organic electroluminescence device in which at least a hole injection layer and a light emitting layer are laminated between a pair of electrodes,
The hole injection layer contains zinc sulfide;
The light emitting layer is directly laminated on the hole injection layer,
The light emitting layer contains an organic compound that interacts with the zinc sulfide, and
An organic electroluminescence device wherein the density of the light emitting layer is in the range of 1.0 to 1.8 g / cm ³ .

2. The organic electroluminescence device according to claim 1, wherein the hole injection layer contains zinc sulfide doped with a metal oxide.

3. 3. The organic electroluminescence device according to item 1 or 2, wherein the thickness of the hole injection layer is in the range of 5 to 10 nm.

4. A display apparatus provided with the organic electroluminescent element as described in any one of Claim 1 to 3.

5. An illuminating device provided with the organic electroluminescent element as described in any one of 1st term | claim to 3rd term | claim.

By the above means of the present invention, it is possible to provide an organic electroluminescence device that can improve the density of the light emitting layer, achieve high luminous efficiency and increase the lifetime of the device, and is easy to manufacture.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

In the organic electroluminescence device of the present invention, a light emitting layer containing an organic compound that interacts with ZnS is directly laminated on a hole injection layer made of at least zinc sulfide (ZnS).
Therefore, since the hole injection layer functions as a substrate of the light emitting layer, when forming the light emitting layer on the substrate, the organic compound is caused by the interaction (affinity) between ZnS (especially S) and organic compound molecules. Molecular molecules are regularly arranged at the interface between the hole injection layer and the light emitting layer, and accordingly, organic compound molecules in the vicinity of the interface and further inside are also regularly arranged. It is assumed that the regular arrangement of the organic compound molecules improves the density of the light emitting layer and suppresses the generation of defects in the light emitting layer.
As a result, it is presumed that an element having a light emitting layer with high luminous efficiency and long life could be formed.

In addition, because ZnS has a hole transport function and exciton stabilization (block) function, recombination of carriers in the vicinity of the interface between the hole injection layer and the light emitting layer is increased, which contributes to the improvement of the light emission efficiency. Is also inferred. In addition, such a phenomenon is considered to have an influence on the improvement of the density due to the temporal change of the morphology (morphology / fine structure) of the light emitting layer.
Furthermore, since ZnS which is an inorganic material is used, it is excellent in solvent tolerance, the choice of the solvent of a light emitting layer spreads, and it becomes easy to manufacture an organic EL element.

Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of display part A Schematic showing the pixel circuit Schematic diagram of passive matrix type full color display device Schematic diagram of lighting device Cross section of the lighting device

The organic electroluminescence device of the present invention is an organic electroluminescence device in which at least a hole injection layer and a light emitting layer are laminated between a pair of electrodes, wherein the hole injection layer contains zinc sulfide, and the light emission A layer is directly laminated on the hole injection layer, the light-emitting layer contains an organic compound having an interaction with the zinc sulfide, and the density of the light-emitting layer is 1.0 to 1.8 g / Within the range of cm ³ . This feature is a technical feature common to or corresponding to the claimed invention.
As an embodiment of the present invention, it is preferable that the hole injection layer contains zinc sulfide doped with a metal oxide from the viewpoint of further improving luminous efficiency.
The thickness of the hole injection layer is preferably in the range of 5 to 10 nm from the viewpoint that the light emission efficiency and the device life can be further improved.

The organic electroluminescence element of the present invention is suitably used for display devices and lighting devices.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
[Outline of the present invention]
The organic electroluminescence device of the present invention (hereinafter also referred to as “organic EL device”) is an organic electroluminescence device in which at least a hole injection layer and a light emitting layer are laminated between a pair of electrodes, The injection layer contains zinc sulfide, the light emitting layer is laminated directly on the hole injection layer, the light emitting layer contains an organic compound that interacts with the zinc sulfide, and the light emitting layer Is in the range of 1.0 to 1.8 g / cm ³ .

The density of the light emitting layer according to the present invention is preferably in the range of 1.4 to 1.7 g / cm ³ from the viewpoint of further improving the density of the light emitting layer and further improving the light emission efficiency and the device lifetime.

The density of the light emitting layer can be determined by the X-ray reflectivity method. It is obtained by measuring the reflectance at a very low angle, for example, in the range of 0.2 to 2 degrees, and fitting the obtained reflectance curve to the reflectance formula of the multilayer film sample obtained from the Fresnel formula. . For the fitting method, see L.C. G. Parrat. Phis. Rev. 95 359 (1954).
Specifically, the X-ray generation source uses copper as a target, operates at 50 kV-300 mA, and uses X-rays monochromatic with a multilayer mirror and a Ge (111) channel cut monochromator. The measurement was performed using the software-ATX-Crystal Guide Ver. Using 6.5.3.4, after alignment adjustment, scan 2θ / ω = 0 to 1 degree at 0.002 degree / step at 0.05 degree / min. After measuring the reflectance curve under the above measurement conditions, GXRR Ver. 2.1.0 Measured using analysis software.

The pair of electrodes is an anode and a cathode. In the organic EL device of the present invention, preferably, an anode and a cathode, and at least a hole injection layer and a light emitting layer are laminated between these electrodes on a substrate. ing.
In a broad sense, the light-emitting layer refers to a layer that emits light when an electric current is applied to an electrode composed of a cathode and an anode. Specifically, when an electric current is applied to an electrode composed of a cathode and an anode, It refers to a layer containing an organic compound that emits light.
The organic EL device of the present invention may have an electron injection layer and an electron transport layer in addition to the hole injection layer and the light emitting layer as necessary, and these layers are sandwiched between the cathode and the anode. Take the structure.

In addition, preferred specific examples of the layer configuration of the organic EL element on the substrate are shown below, but other configurations are limited as long as the light emitting layer is directly laminated on the hole injection layer containing ZnS. Not.
(I) Anode / hole injection layer / emission layer / cathode (ii) Anode / hole injection layer / emission layer / electron injection layer / cathode (iii) Anode / hole injection layer / emission layer / electron transport layer / electron Injection layer / cathode (vi) Anode / hole injection layer / light emitting layer / electron transport layer / cathode

Further, a cathode buffer layer (for example, lithium fluoride) may be inserted between the electron injection layer and the cathode, and an anode buffer layer (for example, copper phthalocyanine) may be inserted between the anode and the hole injection layer. ) May be inserted.
Hereinafter, the structure of each layer of the substrate and the organic EL element will be described in detail.

(substrate)
The substrate that can be used in the organic EL device of the present invention (hereinafter also referred to as a base, a support substrate, a base material, a support, etc.) is not particularly limited, and a glass substrate, a plastic substrate, or the like can be used. It may be transparent or opaque. When extracting light from the substrate side, the substrate is preferably transparent. Examples of the transparent substrate preferably used include glass, quartz, and a transparent plastic substrate.
In order to prevent oxygen and water from entering from the substrate side, the substrate has a thickness of 1 μm or more and a water vapor transmission rate of 1 g / (m ² · 24 h · atm in a test based on JIS Z-0208. ) (25 ° C.) or less is preferred.

Specific examples of the glass substrate include alkali-free glass, low alkali glass, and soda lime glass. Alkali-free glass is preferable from the viewpoint of low moisture adsorption, but any of these may be used as long as it is sufficiently dried.

In recent years, plastic substrates have been attracting attention for reasons such as high flexibility, light weight and resistance to cracking, and further reduction in thickness of organic EL elements.
The resin film used as the base material of the plastic substrate is not particularly limited. For example, polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC) ), Cellulose acetates such as cellulose acetate butyrate, cellulose acetate propionate (CAP), cellulose acetate phthalate, cellulose nitrate, or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate , Norbornene resin, polymethylpentene, polyetherketone, polyimide, polyethersulfone PES), polyphenylene sulfide, polysulfones, polyetherimides, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, a resin film made of an organic-inorganic hybrid resin. Examples of the organic-inorganic hybrid resin include those obtained by combining an organic resin and an inorganic polymer (for example, silica, alumina, titania, zirconia, etc.) obtained by a sol-gel reaction. Among these, norbornene (or cycloolefin-based) resins such as Arton (manufactured by JSR) or Apel (manufactured by Mitsui Chemicals) are particularly preferable.

Normally produced plastic substrates have a relatively high moisture permeability and may contain moisture inside the substrate. Therefore, when using such a plastic substrate, it is preferable to provide a film (hereinafter referred to as “barrier film” or “water vapor sealing film”) that suppresses intrusion of water vapor, oxygen, or the like on the resin film.
The material constituting the barrier film is not particularly limited, and an inorganic film, an organic film, a hybrid of both, or the like is used. A film may be formed, and the water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 is 0.01 g / ( m ² · 24 h) or less, and the oxygen permeability measured by a method according to JIS K 7126-1987 is preferably 1 × 10 ⁻³ mL / (m ² · 24 h). It is preferably a high gas barrier film having a water vapor permeability of 1 × 10 ⁻⁵ g / (m ² · 24 h) or less.

The material constituting the barrier film is not particularly limited as long as it is a material having a function of suppressing intrusion of elements that cause deterioration of the element such as moisture and oxygen. For example, a metal oxide, a metal oxynitride, a metal nitride, or the like Inorganic materials, organic materials, hybrid materials of the both, or the like can be used. Metal oxides, metal oxynitrides or metal nitrides include metal oxides such as silicon oxide, titanium oxide, indium oxide, tin oxide, indium tin oxide (ITO) and aluminum oxide, and metal nitrides such as silicon nitride And metal oxynitrides such as silicon oxynitride and titanium oxynitride.

Furthermore, 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 barrier membrane had a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) of 0.01 g / (m ² · 24 h) measured by a method according to JIS K 7129-1992. The following gas barrier film is preferable, and further, the oxygen permeability measured by a method according to JIS K 7126-1987 is 1 × 10 ⁻³ mL / (m ² · 24 h · atm) or less, A high gas barrier film having a water vapor permeability of 1 × 10 ⁻⁵ g / (m ² · 24 h) or less is preferable.

The method of providing the barrier film on the resin film is not particularly limited, and any method may be used. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam method, ion plating Method, plasma polymerization method, atmospheric pressure plasma polymerization method, CVD method (chemical vapor deposition: for example, plasma CVD method, laser CVD method, thermal CVD method, etc.), coating method, sol-gel method, etc. can be used. . Of these, the method by plasma CVD treatment at or near atmospheric pressure is preferable from the viewpoint that a dense film can be formed.
Examples of the opaque substrate include a metal plate such as aluminum and stainless steel, a film, an opaque resin substrate, a ceramic substrate, and the like.

(anode)
As the anode of the organic EL element, a material having a work function (4 eV or more) metal, alloy, metal electrically conductive compound, or a mixture thereof is preferably used. Here, the “metal conductive compound” refers to a compound of a metal and another substance having electrical conductivity, and specifically, for example, a metal oxide, a halide or the like. That has electrical conductivity.

Specific examples of such an electrode substance include a conductive transparent material such as a metal such as Au, CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. The anode can be produced by forming a thin film made of these electrode materials on the substrate by a known method such as vapor deposition or sputtering.
In addition, a pattern having a desired shape may be formed on the thin film by a photolithography method, and when a pattern accuracy is not required (about 100 μm or more), a desired shape can be formed at the time of vapor deposition or sputtering of the electrode material. A pattern may be formed through a mask.
When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%. The sheet resistance as the anode is several hundred Ω / sq. The following is preferred. Furthermore, although the layer thickness of the anode depends on the material constituting it, it is usually selected within the range of 10 nm to 1 μm, preferably 10 to 200 nm.

(Hole injection layer)
The material used for the hole injection layer (also referred to as “hole injection / transport layer”) according to the present invention contains zinc sulfide (ZnS) applicable as a hole injection material and a hole transport material. .
Therefore, the hole injection layer in the present invention is a hole injection layer having a hole transport function.
The hole injection material has either hole injection or electron barrier properties. The hole transport material has an electron barrier property and has a function of transporting holes to the light emitting layer.

The hole injection layer according to the present invention may be doped with a metal oxide or the like as long as it contains ZnS.
Examples of metal oxides that can be doped with ZnS include molybdenum oxide, vanadium oxide, and tungsten oxide.
The doping concentration of the metal oxide is preferably in the range of 25 to 75%.

In addition to ZnS, the hole injection material used for the hole injection layer may be either organic or inorganic.
Specifically, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives , Hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, porphyrin compounds, thiophene oligomers and other conductive polymer oligomers. Of these, arylamine derivatives and porphyrin compounds are preferred. Among the arylamine derivatives, aromatic tertiary amine compounds and styrylamine compounds are preferable, and aromatic tertiary amine compounds are more preferable.

Representative examples of the aromatic tertiary amine compound and styrylamine compound 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; Bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p- Tolylaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, '-Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) biphenyl 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-diphenylaminostilbene; N-phenylcarbazole, as well as two fused aromatics described in US Pat. No. 5,061,569 Having a ring in the molecule, for example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter abbreviated as α-NPD), 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (MTDATA) in which triphenylamine units described in No. 308688 are linked in three starburst types In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material.

The hole injection layer may be formed by either a dry process or a wet process, and the hole injection material may be formed using, for example, a vacuum deposition method, a spin coating method, a casting method, an LB method, an ink jet method, a transfer method, or a printing method. The thin film can be formed by a known method such as a method.
The thickness of the hole injection layer is in the range of 5 to 10 nm, the density of the light emitting layer can be in the range of 1.0 to 1.7 g / cm ³ , and the light emission efficiency and the device life can be reduced. It is preferable in that it can be further improved.

(Light emitting layer)
The light emitting layer according to the present invention is directly laminated on the hole injection layer, the light emitting layer contains an organic compound having an interaction with zinc sulfide contained in the hole injection layer, and the density of the light emitting layer is It is within the range of 1.0 to 1.8 g / cm ³ .
The density of the light emitting layer is more preferably in the range of 1.4 to 1.7 g / cm ³ . As means for obtaining such a density range, for example, the thickness of the hole injection layer is adjusted within the range of 5 to 10 nm as described above, or the ZnS layer is doped with a metal oxide.

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 injection 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 light emitting layer may be a layer having a single composition, or may be a laminated structure including a plurality of layers having the same or different compositions.
The light emitting layer itself may be provided with functions such as a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer. That is, (1) an injection function capable of injecting holes from an anode or a hole injection layer and applying electrons from a cathode or an electron injection layer when an electric field is applied to the light emitting layer, and (2) injection At least one of a transport function that moves electric charges (electrons and holes) by the force of an electric field, and (3) a light-emitting function that provides a recombination field of electrons and holes inside the light-emitting layer and connects it to light emission. A function may be added. Note that the light emitting layer may have a difference in the ease of hole injection and the ease of electron injection, and the transport function represented by the mobility of holes and electrons may be large or small. The one having a function of moving at least one of the charges is preferable.

(Organic compounds used in the light emitting layer)
As an organic compound used for a light emitting layer, it is preferable that the host compound and the light emission dopant are contained.
The light emitting dopant contained in the light emitting layer may be contained at a uniform concentration or may have a concentration distribution in the thickness direction of the light emitting layer.
In the case of an organic EL element having a tandem structure, the thickness of each light emitting layer included in each light emitting unit is not particularly limited, but the homogeneity of a layer to be formed and a high voltage unnecessary for light emission are not required. From the viewpoint of preventing the application and improving the stability of the emission color with respect to the drive current, it is preferably adjusted within the range of 5 to 200 nm, more preferably within the range of 10 to 100 nm.
Hereinafter, the phosphorescent host compound and phosphorescent dopant contained in the light emitting layer will be described.

(1) Phosphorescent host compound The phosphorescent host compound used in the present invention is not particularly limited in terms of structure, but typically includes, for example, a carbazole derivative, a triarylamine derivative, an aromatic borane derivative, Those having basic skeletons such as nitrogen heterocyclic compounds, thiophene derivatives, furan derivatives, oligoarylene compounds, carboline derivatives and diazacarbazole derivatives (here, diazacarbazole derivatives are carbonizations constituting the carboline ring of carboline derivatives) And the like in which at least one carbon atom of the hydrogen ring is substituted with a nitrogen atom.

The phosphorescent host compound may be used alone or in combination of two or more.

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

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

In the general formula (a), examples of the substituent represented by R ′ and R ″ include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a tert-butyl group, a pentyl group, a hexyl 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, aryl group, 1-propenyl group, 2- Butenyl, 1,3-butadienyl, 2-pentenyl, isopropenyl, etc.), alkynyl (eg, ethynyl, propargyl, etc.), aromatic hydrocarbon (aromatic carbocyclic, aryl, etc.) For example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, ant 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, 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) ), Phthalazinyl group, etc.), heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, Hexyloxy group, octyl Xyl 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, phenyloxy Carbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecyl) Aminosulfonyl 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 group ( For example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonyl) Amino 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, Hexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethyl Ureido 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, 2-pyridyl Sulfinyl 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, pentaf) Oroethyl 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 group, etc. Is mentioned.
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 preferably represents NR ′ or O, and R ′ particularly preferably represents 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.
The aromatic ring represented by Ar may be either a single ring or a condensed ring, and further has a substituent represented by the above R ′ and R ″ even if it is unsubstituted. May be.

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, and 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, pyranthrene ring, anthraanthrene ring and the like.

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 A ring, an isoquinoline ring, a phthalazine ring, a naphthyridine ring, a carbazole ring, a carboline ring, a diazacarbazole ring (indicating a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is substituted with a nitrogen atom). Can be mentioned.

In the general formula (a), the aromatic ring represented by Ar is preferably a carbazole ring, carboline ring, dibenzofuran ring or benzene ring, more preferably a carbazole ring, carboline ring or benzene ring, Preferred is a benzene ring having a substituent, and most preferred is a benzene ring having a carbazolyl group.

In the general formula (a), the aromatic ring represented by Ar is preferably a condensed ring having three or more rings, as shown below.
Specific examples of the aromatic hydrocarbon condensed ring in which three or more rings are condensed include, for example, naphthacene ring, anthracene ring, tetracene ring, pentacene ring, hexacene ring, phenanthrene ring, pyrene ring, benzopyrene ring, benzoazulene ring, Chrysene ring, benzochrysene ring, acenaphthene ring, acenaphthylene ring, triphenylene ring, coronene ring, benzocoronene ring, hexabenzocoronene ring, fluorene ring, benzofluorene ring, fluoranthene ring, perylene ring, naphthoperylene ring, pentabenzoperylene ring, benzoperylene ring , Pentaphen ring, picene ring, pyranthrene ring, coronene ring, naphtho coronene ring, ovalen ring, anthraanthrene ring and the like.

Specific examples of the aromatic heterocyclic condensed ring in which three or more rings are condensed include, for example, an acridine ring, a benzoquinoline ring, a carbazole ring, a carboline ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, and a carboline ring. , Cyclazine ring, quindrine ring, tepenidine ring, quinindrin ring, triphenodithiazine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, diazacarbazole ring (carbon of hydrocarbon ring constituting carboline ring) One of the atoms is replaced by a nitrogen atom.), Phenanthroline ring, dibenzofuran ring, dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, benzodifuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring Anthradithiophene furan ring, anthracite thiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, such as thio fan train ring (naphthothiophene ring).

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

Specific examples of the phosphorescent host compound represented by the general formula (a) are shown below, but the present invention is not limited to these.

In addition, 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 ’s okay.

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

In the present invention, a conventionally known host compound can also be used.
As specific examples of conventionally known host compounds, compounds described in the following documents can be suitably used. For example, Japanese Patent Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579 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. No. 2002-302516, No. 2002-305083, No. 2002-305084, No. 2002-308837, and the like.

In an organic EL device having a tandem structure, the phosphorescent host compound may be different for each light emitting layer of each light emitting unit, but the same compound is preferable in terms of production efficiency and process management.

In addition, the phosphorescent host compound preferably has a lowest excited triplet energy (T1) larger than 2.7 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 an emission band corresponding to the transition between the lowest vibrational bands of a phosphorescence emission spectrum observed at a liquid nitrogen temperature after dissolving a host compound in a solvent.

(2) Phosphorescence emission dopant The phosphorescence emission dopant which can be used for this invention can be selected from a well-known thing. For example, it can be selected from complex compounds containing metals of Group 8 to Group 10 in the periodic table of elements, preferably iridium compounds, osmium compounds or platinum compounds (platinum complex compounds), or rare earth complexes. Of these, iridium compounds are most preferred.
In the case of producing an organic EL element that emits white light, a phosphorescent light emitting material is preferable as a light emitter that emits light in at least the green, yellow, and red regions.

(Partial structures represented by general formulas (A) to (C))
In addition, when a blue phosphorescent dopant is used as the phosphorescent dopant, it can be appropriately selected from known ones used for the light emitting layer of the organic EL device, and the following general formulas (A) to (C It is preferable to have at least one partial structure selected from

In general formula (A), Ra represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Rb and Rc each independently represents a hydrogen atom or a substituent. A1 represents a residue necessary for forming an aromatic ring or an aromatic heterocyclic ring. M represents Ir or Pt.

In general formula (B), Ra represents a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group. Rb, Rc, Rb ₁ and Rc ₁ each independently represent a hydrogen atom or a substituent. A1 represents a residue necessary for forming an aromatic ring or an aromatic heterocyclic ring. M represents Ir or Pt.

In general formula (C), Ra represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Rb and Rc each independently represents a hydrogen atom or a substituent. A1 represents a residue necessary for forming an aromatic ring or an aromatic heterocyclic ring. M represents Ir or Pt.

In the general formulas (A) to (C), examples of the aliphatic group represented by Ra include an alkyl group (eg, methyl group, ethyl group, propyl group, butyl group, pentyl group, isopentyl group, 2-ethyl group). -Hexyl group, octyl group, undecyl group, dodecyl group, tetradecyl group) and cycloalkyl group (for example, cyclopentyl group, cyclohexyl group).
Examples of the aromatic group represented by Ra include a phenyl group, a tolyl group, an azulenyl group, an anthranyl group, a phenanthryl group, a pyrenyl group, a chrycenyl group, a naphthacenyl group, an o-terphenyl group, an m-terphenyl group, p -Terphenyl group, acenaphthenyl group, coronenyl group, fluorenyl group, perylenyl group and the like.
Examples of the heterocyclic group represented by Ra include pyrrolyl, indolyl, furyl, thienyl, imidazolyl, pyrazolyl, indolizinyl, quinolinyl, carbazolyl, indolinyl, thiazolyl, pyridyl, pyridazinyl. Group, thiadiazinyl group, oxadiazolyl group, benzoquinolinyl group, thiadiazolyl group, pyrrolothiazolyl group, pyrrolopyridazinyl group, tetrazolyl group, oxazolyl group, chromanyl group and the like.
These groups may have a substituent represented by R ′ and R ″ in the general formula (a).

In the general formulas (A) to (C), examples of the substituent represented by Rb, Rc, Rb ₁ and Rc ₁ include an alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, tert- Butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group) Etc.), alkynyl groups (eg ethynyl group, propargyl group etc.), aryl groups (eg phenyl group, naphthyl group etc.), aromatic heterocyclic groups (eg furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group) Group, pyrazinyl group, triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolyl Group, phthalazinyl group, etc.), heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxyl group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group) Octyloxy group, dodecyloxy group, etc.), cycloalkoxyl 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 (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group) Etc.), alkoxycarbonyl groups (eg methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group etc.), aryloxycarbonyl groups (eg phenyloxycarbonyl group, naphthyloxy) Carbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenyl) Aminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propyl group) Rubonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyl group) Oxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, Pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group Group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octyl) Aminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group) Cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl Groups (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group ( For example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group (for example, 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, dodecylamine) 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, Pentafluoroethyl 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.) Can be mentioned.
These substituents may be further substituted with the above substituents.

In the general formulas (A) to (C), examples of the aromatic ring represented by A1 include a benzene ring, biphenyl ring, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, and 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, pyranthrene ring, anthraanthrene ring and the like.
As the aromatic heterocycle represented by A1, for example, furan ring, thiophene ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, benzimidazole ring, oxadiazole ring, triazole ring, imidazole ring, Pyrazole ring, thiazole ring, indole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, phthalazine ring, carbazole ring, carboline ring, diazacarbazole ring (the hydrocarbon ring constituting the carboline ring) A ring in which one of the carbon atoms is substituted with a nitrogen atom.) And the like.

In the general formulas (A) to (C), M represents Ir or Pt, with Ir being preferred.

The structures of the general formulas (A) to (C) are partial structures, and a ligand corresponding to the valence of the central metal is necessary for the structure itself to be a light-emitting dopant of a completed structure. Specific examples of such ligands include, for example, halogen (eg, fluorine atom, chlorine atom, bromine atom or iodine atom), aryl group (eg, phenyl group, p-chlorophenyl group, mesityl group, Tolyl group, xylyl group, biphenyl group, naphthyl group, anthryl group, phenanthryl group, etc.), alkyl group (for example, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl) Group), alkyloxy group, aryloxy group, alkylthio group, arylthio group, aromatic heterocyclic group (for example, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, Pyrazolyl group, thiazolyl group, quinazolinyl group, carbazolyl group, cal Riniru group, phthalazinyl group, etc.), the general formula (A) ~ partial structure such as metal except for the (C) can be mentioned.

As the luminescent dopant, a tris body having a completed structure with three partial structures of the general formulas (A) to (C) is preferable.

Hereinafter, phosphorescent dopants having the partial structures of the general formulas (A) to (C) will be exemplified, but the invention is not limited thereto.

(3) Fluorescent luminescent dopant Fluorescent luminescent dopants (also referred to as fluorescent dopants, fluorescent luminescent materials, etc.) include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes. Fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes, polythiophene dyes, rare earth complex phosphors, and the like.

(Electron injection layer and electron transport layer)
The electron injecting layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and any material can be selected from conventionally known compounds. Examples of materials for organic EL elements used in this electron injection layer (hereinafter also referred to as “electron injection materials”) include heterocyclic rings such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, and the like. Examples include tetracarboxylic anhydride, carbodiimide, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like.

In addition, a series of electron transfer compounds described in Japanese Patent Application Laid-Open No. 59-194393 is disclosed as a material for forming a light emitting layer in the publication, but as a result of investigations by the present inventors, electron injection is performed. It was found that it can be used as a material. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, or a quinoxaline derivative having a quinoxaline ring known as an electron-withdrawing group can also be used as an electron injection material.

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (abbreviated as Alq ₃ ), 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), etc., and the central metal of these metal complexes is In Metal complexes replaced with Mg, Cu, Ca, Sn, Ga, or Pb can also be used as the electron injection material.

In addition, metal-free or metal phthalocyanine, or those in which the terminal is substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron injection material. Similarly to the hole injection layer, an inorganic semiconductor such as n-type-Si or n-type-SiC can also be used as the electron injection material.
A preferable material for an organic EL element used for the electron transport layer preferably has a fluorescence maximum wavelength at 415 nm or less. That is, the organic EL element material used for the electron transport layer is preferably a compound that has an electron transport ability, prevents the emission of light from becoming longer, and has a high Tg.
The electron injection layer is formed by thinning the electron injection material by a known method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, an ink jet method, a transfer method, or a printing method. Can do.
The thickness of the electron injection layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm. The electron injection layer may have a single layer structure composed of one or more of these electron injection materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.

In the present specification, when the ionization energy of the electron injection layer is larger than that of the light emitting layer, it is particularly referred to as an electron transport layer. Therefore, in this specification, an electron carrying layer is contained in an electron injection layer.
The electron transport layer is also referred to as a hole blocking layer (hole block layer). Examples thereof include, for example, WO00 / 70655, JP2001-313178, JP11-204258, and 11-204359. And the like described in page 237 of “Organic EL devices and their forefront of industrialization” (issued on November 30, 1998 by NTS). In particular, in the so-called “phosphorescent light emitting device” using an ortho metal complex dopant in the light emitting layer, it is preferable to adopt a configuration having an electron transport layer (hole blocking layer) as in the above (v) and (vi).

(Buffer layer)
A buffer layer (electrode interface layer) may exist between the anode and the hole injection layer and between the cathode and the light emitting layer or the electron injection layer. The buffer layer is a layer that is provided between the electrode and the organic layer in order to lower the driving voltage and improve the light emission efficiency. “The organic EL element and the forefront of its industrialization (issued on November 30, 1998 by NTS Corporation) ) ”, Chapter 2, Chapter 2,“ Electrode Materials ”(pages 123 to 166), which includes an anode buffer layer and a cathode buffer layer.

Details of the anode buffer layer are also described in JP-A-9-45479, 9-260062, 8-28869, etc., and specific examples thereof include a phthalocyanine buffer layer represented by copper phthalocyanine, vanadium oxide. And an oxide buffer layer, 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 are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, a metal buffer layer typified by strontium or aluminum, Examples thereof include an alkali metal compound buffer layer typified by lithium fluoride, an alkaline earth metal compound buffer layer typified by magnesium fluoride, and an oxide buffer layer typified by aluminum oxide.

The buffer layer is desirably a very thin film, and depending on the material, the thickness is preferably in the range of 0.1 to 100 nm. Furthermore, in addition to the basic constituent layers, layers having other functions may be appropriately laminated as necessary.

(cathode)
As the cathode of the organic EL element, a metal having a low work function (less than 4 eV) (hereinafter referred to as an electron injecting metal), an alloy, a metal electrically conductive compound, or a mixture thereof is used. .
Specific examples of such electrode materials include sodium, magnesium, lithium, aluminum, indium, rare earth metals, sodium-potassium alloys, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / Aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture and the like.

In the present invention, those listed above may be used as the electrode material of the cathode. However, from the viewpoint of more effectively exerting the effects of the present invention, the cathode may contain a Group 13 metal element. preferable. That is, in the present invention, as described later, the surface of the cathode is oxidized with oxygen gas in a plasma state to form an oxide film on the cathode surface, thereby preventing further oxidation of the cathode and improving the durability of the cathode. Can be made.

Therefore, the electrode material of the cathode is preferably a metal having a preferable electron injection property required for the cathode and capable of forming a dense oxide film.
Specific examples of the electrode material of the cathode containing the Group 13 metal element include, for example, aluminum, indium, a magnesium / aluminum mixture, a magnesium / indium mixture, and an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture. And lithium / aluminum mixtures. In addition, the mixing ratio of each component of the said mixture can employ | adopt a conventionally well-known ratio as a cathode of an organic EL element, However It is not limited to this in particular. The cathode can be produced by forming a thin film on the organic functional layer by depositing the electrode material described above by a method such as vapor deposition or sputtering.
The sheet resistance as a cathode is several hundred Ω / sq. The following is preferable, and the layer thickness is usually selected in the range of 10 nm to 1 μm, preferably 50 to 200 nm. In order to transmit the emitted light, it is preferable that either one of the anode and the cathode of the organic EL element is made transparent or semi-transparent because the light emission efficiency is improved.

[Method of manufacturing organic EL element]
As an example of the method for producing an organic EL device according to the present invention, a method for producing an organic EL device comprising anode / hole injection layer / light emitting layer / electron transport layer / electron injection layer / cathode will be described.
First, a thin film made of a desired electrode material, for example, an anode material is formed on a suitable substrate by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably 10 to 200 nm. Make it.
Next, the organic compound thin film of the hole injection layer, the light emitting layer, the electron transport layer, the electron injection layer, and the hole blocking layer containing at least ZnS described above is sequentially formed thereon. Here, it is preferable to form a light emitting layer using the composition of the present invention.
As described above, there are spin coating methods, casting methods, ink jet methods, vapor deposition methods, printing methods, and the like as methods for thinning these organic compound thin films. A vacuum deposition method or a spin coating method is preferable from the viewpoint that it is difficult to form. In the present invention, the spin coating method is particularly preferable because the composition of the present invention can be used as a coating solution.

Different film formation 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 to 450 ° C., a vacuum degree of 10 ⁻⁶ to 10 ⁻² Pa, a vapor deposition rate of 0.01 It is desirable to select appropriately within the range of ˜50 nm / second, substrate temperature of −50 to 300 ° C., and thickness of 0.1 nm to 5 μm.
After these layers are formed, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained. The organic EL element is preferably manufactured from the hole injection layer to the cathode consistently by a single evacuation, but it 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.

[Encapsulation of organic EL elements]
The organic EL element sealing means is not particularly limited. For example, after sealing the outer periphery of the organic EL element with a sealing adhesive, a sealing member is provided so as to cover the light emitting region of the organic EL element. The method of arranging is mentioned.

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

As the sealing member, a polymer film and a metal film can be preferably used from the viewpoint of reducing the thickness of the organic EL element.

In the gap between the sealing member and the light emitting region of the organic EL element, in addition to the sealing adhesive, in the gas phase and liquid phase, inert gases such as nitrogen and argon, fluorinated hydrocarbons, and silicone oil are used. Inert liquids can also be injected. Further, the gap between the sealing member and the display area of the organic EL element can be evacuated, or a hygroscopic compound can be sealed in the gap.

[Display device]
The multicolor display device using the organic EL element of the present invention is provided with a shadow mask only at the time of forming a light emitting layer, and the other layers are common, so patterning such as a shadow mask is unnecessary, vapor deposition method, casting method, A film can be formed by a spin coating method, an inkjet method, a printing method, 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.

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 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.

The multicolor display device can be used as a display device, a display, and various light emission sources. In a display device or display, full-color display is possible by using three types of organic EL elements of blue, red, and green light emission.
Examples of the display device and the display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in a car. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.

Light sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. For example, but not limited to.
Further, the organic EL element according to the present invention may be used as an organic EL element having a resonator structure.

Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processing machine, and a light source of an optical sensor. It is not limited. Moreover, you may use for the said use by making a laser oscillation.
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. Alternatively, it is possible to produce a full-color display device by using two or more organic EL elements of the present invention having different emission colors.

An example of a display device composed of the organic EL element of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram illustrating an example of a display device including organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element. The display 41 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like. The control unit B is electrically connected to the display unit A, and sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. The pixels for each scanning line are converted into image data signals by the scanning signal. In response to this, light is sequentially emitted and image scanning is performed to display image information on the display unit A.
FIG. 2 is a schematic diagram of the display unit A. The display unit A includes a wiring unit including a plurality of scanning lines 55 and data lines 56, a plurality of pixels 53, and the like on a substrate. The main members of the display unit A will be described below.

FIG. 2 shows a case where the light emitted from the pixel 53 is extracted in the white arrow direction (downward). The scanning lines 55 and the plurality of data lines 56 in the wiring portion are each made of a conductive material, and the scanning lines 55 and the data lines 56 are orthogonal to each other in a lattice shape and are connected to the pixels 53 at the orthogonal positions (details are shown in the figure). Not shown). When a scanning signal is applied from the scanning line 55, the pixel 53 receives an image data signal from the data line 56, and emits light according to the received image data. Full color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region that emit light on the same substrate.

Next, the light emission process of the pixel will be described.
FIG. 3 is a schematic diagram illustrating a pixel circuit. The pixel includes an organic EL element 60, a switching transistor 61, a driving transistor 62, a capacitor 63, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 60 for a plurality of pixels, and juxtaposing them on the same substrate.
3, an image data signal is applied to the drain of the switching transistor 61 from the control unit B (not shown in FIG. 3, but shown in FIG. 1) via the data line 56. When a scanning signal is applied from the control unit B to the gate of the switching transistor 61 via the scanning line 55, the switching transistor 61 is turned on, and the image data signal applied to the drain is supplied to the capacitor 63 and the driving transistor 62. Is transmitted to the gate.
By transmitting the image data signal, the capacitor 63 is charged according to the potential of the image data signal, and the drive of the drive transistor 62 is turned on. The drive transistor 62 has a drain connected to the power supply line 67 and a source connected to the electrode of the organic EL element 60, and the power supply line 67 changes to the organic EL element 60 according to the potential of the image data signal applied to the gate. Current is supplied.

When the scanning signal moves to the next scanning line 55 by the sequential scanning of the control unit B, the driving of the switching transistor 61 is turned off. However, even if the driving of the switching transistor 61 is turned off, the capacitor 63 holds the potential of the charged image data signal, so that the driving of the driving transistor 62 is kept on and the next scanning signal is applied. Until then, the organic EL element 60 continues to emit light. When the scanning signal is next applied by sequential scanning, the driving transistor 62 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 60 emits light. That is, the organic EL element 60 emits light by providing a switching transistor 61 and a drive transistor 62, which are active elements, for each of the organic EL elements 60 of a plurality of pixels, and a plurality of pixels 53 (not shown in FIG. 3). 2) Each organic EL element 60 emits light. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 60 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or on / off of a predetermined light emission amount by a binary image data signal. But you can.
The potential of the capacitor 63 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.
In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

FIG. 4 is a schematic view of a passive matrix display device. In FIG. 4, a plurality of scanning lines 55 and a plurality of image data lines 56 are provided in a lattice shape so as to face each other with the pixel 53 interposed therebetween. When the scanning signal of the scanning line 55 is applied by sequential scanning, the pixel 53 connected to the applied scanning line 55 emits light according to the image data signal. In the passive matrix method, there is no active element in the pixel 53, and the manufacturing cost can be reduced.

[Lighting device]
The lighting device of the present invention includes home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, exposure light sources of electrophotographic copying machines, light sources of optical communication processors, and optical sensors. However, the present invention is not limited to these.

An embodiment of the lighting device of the present invention provided with the organic EL element of the present invention will be described.

The non-light emitting surface of the organic EL device of the present invention is covered with a glass case, a 300 μm thick glass substrate is used as a sealing substrate, and an epoxy photocurable adhesive (LUX The track LC0629B) is applied, and this is overlaid on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured, sealed, and illuminated as shown in FIGS. A device can be formed.

FIG. 5 shows a schematic diagram of the lighting device.
As shown in FIG. 5, the organic EL element 101 is covered with a glass cover 102.
The sealing operation with the glass cover 102 is preferably 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. 6 shows a cross-sectional view of the lighting device.
As shown in FIG. 6, the lighting device mainly includes a cathode 105, an organic EL layer 106, and a glass substrate 107 with a transparent electrode, and these members are covered with a glass cover 102.
The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.
As described above, the organic EL element of the present invention is not only the display device and the display, but also various light emitting sources, lighting devices, home lighting, interior lighting, a kind of lamp such as an exposure light source, and a liquid crystal display. It is also useful for display devices such as device backlights.

In addition, backlights such as clocks, signboard advertisements, traffic lights, light sources such as optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processing machines, light sources for optical sensors, etc. There are a wide range of uses such as household appliances.

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, "mass part" or "mass%" is represented.

[Example 1]
Structural formulas of compounds used in the examples described below are shown below.

<Preparation of organic EL element 1-1>
Patterning was performed on a substrate (AvanState Co., Ltd., NA45) in which ITO (Indium Tin Oxide) 100 nm was formed as an anode on a 100 mm × 100 mm × 1.1 mm glass substrate. Thereafter, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
This transparent support substrate was attached to a vacuum deposition apparatus, and the vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa. Next, 10 nm of ZnS was deposited as a hole injection layer to provide a hole injection layer.

Next, on the hole injection layer, 1-6 as a host compound and D-28 as a dopant were deposited in a ratio of 1-6: D-28 = 100: 5 to a thickness of 70 nm to provide a light emitting layer.
Next, 1.0 nm of lithium fluoride was deposited as an electron injection layer and 110 nm of aluminum was deposited as a cathode, thereby fabricating an organic EL device 1-1.

<Preparation of organic EL elements 1-2 to 1-5>
In the production of the organic EL element 1-1, the material of the hole injection layer was changed to the material shown in Table I below. Other than that, organic EL elements 1-2 to 1-5 were produced in the same manner.

<Evaluation of organic EL element>
The organic EL element produced above was measured by the following methods for (1) luminous efficiency, (2) durability (half-life), and (3) density of the light emitting layer. The measurement results are shown in Table I below.

(1) Evaluation of luminous efficiency (external extraction quantum efficiency (EQE)) For each organic EL element, lighting was performed under a constant current of ^2.5 mA / cm ² at a room temperature of 23 ° C. in a dry nitrogen gas atmosphere, and lighting was started. The external extraction quantum efficiency was calculated by measuring the light emission luminance (L) [cd / m ² ] immediately after. Here, the emission luminance was measured using a spectral radiance meter “CS-1000” (manufactured by Konica Minolta). This external extraction quantum efficiency was used as an index of luminous efficiency.

(2) Evaluation of durability (half life) Each organic EL element was driven at a constant current under a constant environmental condition of 50 ° C. with a current giving an initial luminance of 1000 cd / m ^2, and 1/2 of the initial luminance (500 cd) / M ² ) The time required to reach (m ² ) (half life at 50 ° C. storage) was determined and used as a measure of durability.

(3) Evaluation of the density of a light emitting layer The density of the light emitting layer of each organic EL element was computed by the X-ray reflectivity method.
The X-ray generation source was a copper target, operated at 50 kV-300 mA, and X-rays monochromatized with a multilayer mirror and a Ge (111) channel cut monochromator were used. The measurement was performed using the software-ATX-Crystal Guide Ver. Using 6.5.3.4, after alignment adjustment, 2θ / ω = 0 to 1 degree was scanned at 0.002 degree / step at 0.05 degree / min. After measuring the reflectance curve under the above measurement conditions, GXRR Ver. 2.1.0 Measured using analysis software.

As is apparent from Table I, the organic EL device using ZnS according to the present invention as the material for the hole injection layer has an initial performance higher than that of the comparative organic EL device not using ZnS as the material for the hole injection layer. It is excellent in any of luminous efficiency, half life, and density of the light emitting layer.

[Example 2]: Example in which the density of the light emitting layer can be controlled by the thickness when ZnS is used for the hole injection layer <Preparation of Organic EL Element 2-1>
Patterning was performed on a substrate (NAV 45 manufactured by AvanStrate Co., Ltd.) on which a 100 nm ITO film was formed as an anode on a 100 mm × 100 mm × 1.1 mm glass substrate. Thereafter, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
This transparent support substrate is fixed to a substrate holder of a commercially available vacuum evaporation apparatus, while ZnS is put into a molybdenum resistance heating boat, 1-6 is put into another molybdenum resistance heating boat, another molybdenum resistance heating boat D-28 was put in, LiF was put in another resistance heating boat made of molybdenum, and attached to a vacuum deposition apparatus.
Next, the pressure in the vacuum chamber was reduced to 4 × 10 ⁻⁴ Pa, and the heating boat containing ZnS was heated by energization. The vapor deposition rate was 0.1 nm / sec. A layer was provided.
Further, the heating boat containing 1-6 and D-28 was energized and heated, and co-evaporated on the hole injection layer at a ratio of 1-6: D-28 = 100: 5, and a 70 nm light emitting layer Was provided.
Further, the heating boat containing LiF was energized and heated, and was deposited as an electron injection layer to provide an electron injection layer of 0.5 nm, and aluminum 110 nm as a cathode.

<Preparation of organic EL elements 2-2 to 2-7>
In the production of the organic EL element 2-1, the thickness of ZnS in the hole injection layer was changed as shown in Table II. Otherwise, the organic EL elements 2-2 to 2-7 were produced in the same manner.

About the produced organic EL element, it carried out similarly to the said Example 1, and measured the luminous efficiency (external extraction quantum efficiency (EQE)), luminous lifetime, and the density of the light emitting layer. The measurement results are shown in Table II below.

As is clear from Table II, the organic EL device in which the thickness of the hole injection layer made of ZnS is in the range of 5 to 10 nm is higher in luminous efficiency (external extraction quantum efficiency) than other organic EL devices, Both the half life (light emission life) and the density of the light emitting layer are excellent.

[Example 3]: Example for showing the effect of ZnS contained in the hole injection layer regardless of the material of the light emitting layer <Production of Organic EL Element 3-1>
Patterning was performed on a substrate (NAV 45 manufactured by AvanStrate Co., Ltd.) on which a 100 nm ITO film was formed as an anode on a 100 mm × 100 mm × 1.1 mm glass substrate. Thereafter, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
This transparent support substrate is fixed to a substrate holder of a commercially available vacuum evaporation apparatus, while ZnS is put into a molybdenum resistance heating boat, 1-6 is put into another molybdenum resistance heating boat, another molybdenum resistance heating boat D-28 was placed in the container, KF was placed in another molybdenum resistance heating boat, and attached to a vacuum deposition apparatus.
Next, the vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, heated by energizing the heating boat containing ZnS, and deposited on a transparent support substrate at a deposition rate of 0.1 nm / second to form a 10 nm hole injection layer. Was provided.
Further, the heating boat containing 1-6 and D-28 was energized and heated, and co-evaporated on the hole injection layer at a ratio of 1-6: D-28 = 100: 5, and a 70 nm light emitting layer Was provided.
Further, the heating boat containing KF was energized and heated, evaporated as an electron injection layer, and provided with a 0.5 nm electron injection layer and an aluminum 110 nm as a cathode.

<Production of organic EL elements 3-2 to 3-10>
In the production of the organic EL element 3-1, the host material and dopant material of the light emitting layer were changed as shown in Table III below. Other than that, the organic EL elements 3-2 to 3-10 were produced in the same manner.

<Preparation of organic EL element 3-11>
Patterning was performed on a substrate (NAV 45 manufactured by AvanStrate Co., Ltd.) on which a 100 nm ITO film was formed as an anode on a 100 mm × 100 mm × 1.1 mm glass substrate. Thereafter, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
This transparent support substrate is fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus. On the other hand, ZnS is placed in a molybdenum resistance heating boat, and α-NPD (4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), 1-6 in another molybdenum resistance heating boat, D-28 in another molybdenum resistance heating boat, another molybdenum resistance KF was put into a heating boat and attached to a vacuum deposition apparatus.
Next, the vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, heated by energizing the heating boat containing ZnS, and deposited on a transparent support substrate at a deposition rate of 0.1 nm / second to form a 10 nm hole injection layer. Was provided.
Further, the heating boat containing α-NPD was energized and heated, and deposited on the hole injection layer to provide a 5 nm organic layer.
Further, the heating boat containing 1-6 and D-28 was energized and heated, and co-evaporated on the organic layer at a ratio of 1-6: D-28 = 100: 5 to form a 70 nm light emitting layer. Provided.
Further, the heating boat containing KF was energized and heated to deposit as an electron injection layer, and a 0.5 nm electron injection layer and aluminum 110 nm as a cathode were provided.

<Production of organic EL elements 3-12 to 3-20>
In the production of the organic EL element 3-11, the host material and dopant material of the light emitting layer were changed as shown in Table III below. Other than that, the organic EL elements 3-12 to 3-20 are similarly processed.
Each was produced.

About the produced organic EL element, it carried out similarly to the said Example 1, and measured the density in a light emitting layer. The measurement results are shown in Table III below.

As is apparent from Table III, the organic EL device in which ZnS is contained in the hole injection layer and the light emitting layer is directly formed on the layer containing ZnS, regardless of the types of the host material and the dopant material, It is excellent in terms of the density of the light emitting layer.

[Example 4]: Solvent resistance of a layer containing ZnS A glass substrate of 100 mm x 100 mm x 1.1 mm was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus, while ZnS was placed in a molybdenum resistance heating boat and attached to the vacuum deposition apparatus.
Next, the pressure in the vacuum chamber was reduced to 4 × 10 ⁻⁴ Pa, and the heating boat containing ZnS was energized and heated, and deposited on the substrate at a deposition rate of 0.1 nm / second to form a 50 nm hole injection layer. A provided single membrane was prepared.
A layer containing ZnS by adding various solvents as shown in Table IV below to the prepared hole injection layer (single film) containing ZnS, spin-coating, drying, and measuring the thickness. The solvent resistance of was examined.
The abbreviations in Table IV are as follows:
TFPO: 2,2,3,3-tetrafluoro-1-propanol THF: tetrahydrofuran 2mTHF: 2-methyltetrahydrofuran

As is clear from Table IV, various solvent resistances of the layer containing ZnS could be confirmed.

[Example 5]: Production of illumination device <Production of white light-emitting organic EL element 4-1>
The transparent support substrate provided with the ITO transparent electrode used in the production of the organic EL element 1-1 was attached to a vacuum deposition apparatus, and the vacuum chamber was decompressed to 4 × 10 ⁻⁴ Pa. Next, 10 nm of ZnS was deposited as a hole injection layer to provide a hole injection layer.
Next, using a solution obtained by dissolving HOST-56 (100 mg) as a host compound and D-86 (3 mg) and Ir-19 (3 mg) as dopants in 10 mL of toluene, spin coating was performed at 2000 rpm for 30 seconds. A thin film was formed. The first light emitting layer was formed by vacuum drying at 60 ° C. for 1 hour.
Further, on this first light-emitting layer, a solution in which HOST-94 (100 mg) as a host compound and D-84 (16 mg) as a dopant were dissolved in 6 mL of hexafluoroisopropanol (HFIP) was used, and the conditions were 2000 rpm for 30 seconds. A thin film was formed by spin coating and vacuum dried at 60 ° C. for 1 hour to form a second light emitting layer.
This substrate is fixed to a substrate holder of a vacuum deposition apparatus, and the vacuum chamber is depressurized to 4 × 10 ⁻⁴ Pa, and then ET-35 is deposited on the second light emitting layer to form an electron transport layer having a thickness of 30 nm. Subsequently, lithium fluoride was vapor-deposited to form a cathode buffer layer having a thickness of 0.5 nm, and aluminum was further vapor-deposited to form a cathode having a thickness of 110 nm. Thus, an organic EL element 4-1 was produced. .

When the produced organic EL element 4-1 was energized, it was found that almost white light was obtained and it could be used as a lighting device. In addition, it turned out that white light emission is obtained similarly even if it replaces with another exemplary compound as a host compound or a dopant.

[Example 6]: Production of full-color display device <Production of blue light-emitting element>
The organic EL device 1-1 of Example 1 was used as a blue light emitting device.

<Production of green light emitting element>
A green light emitting device was produced in the same manner as the organic EL device 1-1 except that D-86 was used as a green light emitting dopant.

<Production of red light emitting element>
A red light emitting device was produced in the same manner as the organic EL device 1-1 except that Ir-9 was used as a red light emitting dopant.

Each of the red, green and blue light emitting organic EL elements produced above was placed on the same substrate to produce an active matrix type full color display device having the form as shown in FIG. 1, and FIG. Only the schematic diagram of the display section A of the display device is shown.
That is, a wiring portion including a plurality of scanning lines 55 and data lines 56 on the same substrate, and a plurality of juxtaposed pixels 53 (light emission color is a red region pixel, a green region pixel, a blue region pixel, etc.) The scanning lines 55 and the plurality of data lines 56 in the wiring portion are each made of a conductive material, and the scanning lines 55 and the data lines 56 are orthogonal to each other in a grid pattern and are connected to the pixels 53 at orthogonal positions ( Details are not shown). The plurality of pixels 53 are driven by an active matrix system in which an organic EL element corresponding to each emission color, a switching transistor as an active element, and a driving transistor are provided, and a scanning signal is applied from a scanning line 55. Then, an image data signal is received from the data line 56, and light is emitted according to the received image data. Thus, a full color display device was produced by juxtaposing the red, green, and blue pixels appropriately.
It was found that by driving the full-color display device, a clear full-color moving image display having high luminance, high durability, and clearness can be obtained.

[Example 7]: Example of doping metal oxide into ZnS of hole injection layer <Preparation of organic EL element 6-1>
Patterning was performed on a substrate (AvanState Co., Ltd., NA45) in which ITO (Indium Tin Oxide) 100 nm was formed on a 100 mm × 100 mm × 1.1 mm glass substrate as an anode. Thereafter, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
This transparent support substrate was attached to a vacuum deposition apparatus, and the vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa. Next, as a hole transport layer, ZnS was deposited to a thickness of 10 nm to provide a hole injection layer.
Next, 1-6 as a host compound and D-28 as a dopant were deposited on the hole injection layer in a ratio of 1-6: D-28 = 100: 5 to 70 nm to provide a light emitting layer.
Next, 1.0 nm of lithium fluoride was deposited as an electron injection layer and 110 nm of aluminum was deposited as a cathode, thereby fabricating an organic EL element 6-1.

<Preparation of organic EL elements 6-2 to 6-4>
Organic EL elements 6-2 to 6-4 were prepared in the same manner as in the production of the organic EL element 6-1, except that ZnS was doped with a metal oxide shown in Table V below as a hole injection layer.

About the produced organic EL element, it carried out similarly to the said Example 1, and measured the luminous efficiency (external extraction quantum efficiency (EQE)), luminous lifetime, and the density of the light emitting layer. The measurement results are shown in Table V below.

As is clear from Table V, the organic EL device containing ZnS in which the hole injection layer is doped with a metal oxide has excellent luminous efficiency as compared with the case where the metal oxide is not doped.

INDUSTRIAL APPLICABILITY The present invention can be used for an organic electroluminescence element that can improve the density of the light emitting layer, improve the light emission efficiency and the element lifetime, and is easy to manufacture, and a display device and an illumination device equipped with the organic electroluminescence element. be able to.

41 Display (display device)
53 pixel 55 scanning line 56 data line 60 organic EL element 61 switching transistor 62 drive transistor 63 capacitor 67 power supply line 101 organic EL element 102 glass cover 105 cathode 106 organic EL layer 107 glass substrate 108 with transparent electrode nitrogen gas 109 water-absorbing agent A Display unit B Control unit

Claims

An organic electroluminescence device in which at least a hole injection layer and a light emitting layer are laminated between a pair of electrodes,
The hole injection layer contains zinc sulfide;
The light emitting layer is directly laminated on the hole injection layer,
The light emitting layer contains an organic compound that interacts with the zinc sulfide, and
An organic electroluminescence device wherein the density of the light emitting layer is in the range of 1.0 to 1.8 g / cm 3 .
The organic electroluminescence device according to claim 1, wherein the hole injection layer contains zinc sulfide doped with a metal oxide.
3. The organic electroluminescence device according to claim 1, wherein the thickness of the hole injection layer is in the range of 5 to 10 nm.
A display apparatus provided with the organic electroluminescent element as described in any one of Claim 1- Claim 3.
A lighting device comprising the organic electroluminescence element according to any one of claims 1 to 3.