JP6226533B2 - Organic electroluminescence device - Google Patents

Description

The present invention relates to an organic electroluminescent device. More specifically, the present invention relates to an organic electroluminescent element that can be used as a display device such as a display unit of an electronic device, a lighting device, or the like.

An organic electroluminescent element (organic EL element) is expected as a new light emitting element applicable to a display device or illumination.
An organic EL element has a structure in which one or more layers including a light emitting layer formed by including a light emitting organic compound are sandwiched between an anode and a cathode, and is injected from holes and cathodes injected from the anode. The light-emitting organic compound is excited using the energy when the generated electrons recombine to obtain light emission. The organic EL element is a current-driven element, and in order to utilize the flowing current more efficiently, various element structures have been improved, and various materials for the layers constituting the element have been studied.

In an organic electroluminescence device that emits light by exciting the light-emitting organic compound by utilizing the energy at the time of recombination of holes injected from the anode and electrons injected from the cathode, hole injection from the anode, Since it is important that both electron injections be performed smoothly, various materials have been studied for the hole injection layer and the electron injection layer so that the hole injection and electron injection can be performed more smoothly. A normal structure organic electroluminescent element using polyethyleneimine or a compound modified with polyethyleneimine has been reported as a layer material (see Non-Patent Documents 1 to 3).

By the way, the organic electroluminescent element in which the layers between the cathode and the anode are all formed of an organic compound is likely to be deteriorated by oxygen or water as a result, and strict sealing is indispensable to prevent these intrusions. This causes a complicated manufacturing process of the organic electroluminescent element. On the other hand, an organic-inorganic hybrid electroluminescent element (HOILED element) in which a part of a layer between a cathode and an anode is formed of an inorganic oxide has been proposed (see Patent Document 1). In this element, by changing the hole transport layer and the electron transport layer to inorganic oxides, it became possible to use FTO or ITO which is a conductive oxide electrode as a cathode and gold as an anode. This means that there are no restrictions on the electrodes from the viewpoint of element driving. As a result, it is not necessary to use a metal having a small work function such as an alkali metal or an alkali metal compound, and light can be emitted without strict sealing. In addition, this HOILED element is characterized in that the cathode is directly above the substrate, and the reverse structure is such that the anode comes to the upper electrode. Along with the development of oxide TFTs, while application to large organic EL displays is being studied, organic ELs having a reverse structure have attracted attention because of the characteristics of n-type oxide TFTs. This HOILED element is expected to develop as a candidate for an inverted organic EL element.

JP 2009-70954 A

Three people outside Tao Xiong, “Applied Physics Letters” 93, 2008, pp123310-1 21 people from Yinhua Zhou, “Science” 336, 2012, pp327 6 people from Jiangshan Chen, “Journal of Materials Chemistry”, 2012, Volume 22, pp5164

As described above, organic-inorganic hybrid type organic electroluminescent elements that do not require strict sealing have been proposed. However, in the organic-inorganic hybrid organic electroluminescent device, the injection of electrons from the cathode is less than the injection of holes from the anode, and the holes injected from the anode cannot be fully utilized for light emission. There is a problem.
Organic electroluminescent elements, which are expected to be used more widely in applications such as display devices and lighting devices, are also an important factor for their ease of manufacture, so organic-inorganic hybrid organic electric fields that do not require strict sealing Expectations for light emitting elements are high, and a method for further increasing the light emission efficiency and lifetime of organic-inorganic hybrid organic electroluminescent elements is required. In addition, in a display application, a HOILED element having an inverse structure is useful on a circuit, and its development is awaited.

The present invention has been made in view of the above-described present situation, and an object thereof is to provide an organic electroluminescent element that is easy to manufacture and has excellent luminous efficiency and lifetime.

The present inventor has conducted various studies on methods for further increasing the luminous efficiency and lifetime of organic-inorganic hybrid organic electroluminescent devices that do not require strict sealing. It was found that forming a nitrogen-containing film having a predetermined thickness improves the electron injection characteristics and prolongs the lifetime of the device. Among these, a nitrogen-containing film having a high nitrogen atom ratio in the atoms constituting the nitrogen-containing film or a nitrogen-containing film formed by a method of decomposing a nitrogen-containing compound to form a nitrogen-containing film may be more preferable. Further, the inventors found that a material formed by decomposition of a nitrogen-containing compound and having a high nitrogen atom ratio in atoms constituting the nitrogen-containing film is more suitable. When the present inventor uses such a nitrogen-containing film as a layer constituting an organic / inorganic hybrid type organic electroluminescence device, the present inventor not only has excellent luminous efficiency but also has high driving stability and long driving life. It has been found that it becomes an element, and has reached the present invention.

That is, the present invention relates to an organic electroluminescent device having a structure in which a plurality of layers are laminated between an anode and a cathode formed on a substrate, wherein the organic electroluminescent device is provided between the anode and the cathode. The organic electroluminescence device is characterized in that it comprises a metal oxide layer, and comprises a layer containing a nitrogen-containing film and an average thickness of 3 to 150 nm on the metal oxide layer.
The present invention is described in detail below.
A combination of two or more preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

The organic electroluminescent device of the present invention is an organic electroluminescent device having an inverted structure having a structure in which a plurality of layers are laminated between an anode and a cathode formed on a substrate, and is between the anode and the cathode. As long as it has a metal oxide layer and a nitrogen-containing film on the metal oxide layer and has an average thickness of 3 to 150 nm, the number of other layers and other layers are configured. There are no particular restrictions on the materials used or the order of lamination, but it is preferable that the metal oxide layer and the nitrogen-containing compound layer are between the cathode and the light-emitting layer. Nitrogen-containing compounds have excellent electron injection characteristics, and an organic electroluminescence device having such a layer structure has high electron injection characteristics, and thus has excellent luminous efficiency.

The nitrogen-containing film used in the organic electroluminescent device of the present invention includes (1) a nitrogen-containing film formed with a nitrogen-containing compound on the metal oxide layer, and (2) formed with a nitrogen-containing compound on the metal oxide layer. A high nitrogen-containing film formed, (3) a nitrogen-containing film formed by decomposing a nitrogen-containing compound on the metal oxide layer, and (4) formed by decomposing a nitrogen-containing compound on the metal oxide layer. There are a total of four types of high nitrogen-containing films.
The reason why the performance of the organic electroluminescent element is improved by forming such a film is estimated as follows.
First of all, when a nitrogen atom is included, the lone pair tends to form a bond with a metal atom in the substrate. The polarization between the metal-nitrogen bonds exhibits strong electron injection characteristics. In all the nitrogen-containing films (1) to (4) above, it is satisfied. More preferably, the above (2) having a high ratio of nitrogen atoms having a lone electron pair is suitable.
In the above (3) and (4), it is expected that a film in which nitrogen atoms are present on the base material at high density due to the phenomenon of decomposition related to film formation, and as a result, various metal-nitrogen bonds appear. It is expected. Among them, it is considered that there is also a stronger metal-nitrogen bond than before. Furthermore, depending on the state of decomposition, other components such as unnecessary carbon disappear, and thus the nitrogen atom fraction is relatively increased. As a result, a more favorable environment may be realized (4). . In these nitrogen-containing films, since the main source of nitrogen is a metal-nitrogen bond, it is expected that nitrogen atoms are accumulated at a higher density than physical adsorption of ordinary molecules. Due to these factors, it is considered that by having such a nitrogen-containing film, the organic electroluminescent element is excellent in luminous efficiency, excellent in element driving stability and element lifetime. In fact, the phenomenon resulting from the decomposition of the nitrogen-containing compound can be verified by X-ray photoelectron spectroscopy, which is one of surface analysis techniques. Specific results will be shown in the examples. By using a compound containing nitrogen and carbon as constituent elements as a nitrogen-containing compound and treating this compound, the carbon: nitrogen ratio (CN ratio) is 2: It has been observed that the nitrogen ratio is high from 1: 1 to 1: 1. At the same time, an increase in the half-value width of the nitrogen spectrum was observed by the above treatment, which indicates the spread of the chemical environment, suggesting the appearance of a stronger metal-nitrogen bond.
Therefore, it can be considered that the foundation of the layer made of a nitrogen-containing film is a film containing a metal element, which greatly contributes to the manifestation of the effect of the organic electroluminescence device of the present invention as described above.

The nitrogen-containing films of the above (1) and (2) are films made of a nitrogen-containing compound formed on the metal oxide layer, that is, films formed without decomposition of the nitrogen-containing compound. The nitrogen-containing film of (2) is formed using a nitrogen-containing compound having a high ratio of the number of nitrogen atoms to the total number of atoms constituting the nitrogen-containing compound.
The method for forming the nitrogen-containing film of the above (1) and (2) is not particularly limited, but a method of volatilizing the solvent after applying a solution of the nitrogen-containing compound on the metal oxide layer is suitably used.

The nitrogen-containing films of the above (3) and (4) are films formed by decomposing a nitrogen-containing compound on the metal oxide layer, but some of the nitrogen-containing compound remains undecomposed. Also good. Preferably, all of the nitrogen-containing compound is decomposed.
The method for forming the nitrogen-containing film in the above (3) and (4) is not particularly limited, but a method in which the nitrogen-containing compound is decomposed and formed after applying a solution of the nitrogen-containing compound on the metal oxide layer is preferable. Used.

The nitrogen-containing film is preferably formed by a method including a step of applying a solution containing a nitrogen-containing compound on the metal oxide layer. By forming the nitrogen-containing film by a method including such steps, the following effects can be obtained.
The metal oxide layer of the organic electroluminescent element is formed by a method such as a spray pyrolysis method, a sol-gel method, or a sputtering method as will be described later, and the surface is not smooth but has irregularities. When a light-emitting layer is formed on the metal oxide layer by a method such as vacuum deposition, depending on the type of components used as the raw material of the light-emitting layer, the unevenness on the surface of the metal oxide layer becomes crystal nuclei, and metal oxidation The crystallization of the material forming the light emitting layer in contact with the physical layer is promoted. For this reason, even if the organic electroluminescent element is completed, a large leak current flows, the light emitting surface becomes non-uniform, and an element that can withstand practical use may not be obtained.
However, when a layer is formed by applying a solution, a smooth surface layer can be formed. Therefore, when a nitrogen-containing compound layer is formed by coating between a metal oxide layer and a light emitting layer, a light emitting layer is formed. Thus, the crystallization of the material to be suppressed is suppressed, whereby the organic electroluminescent element having the metal oxide layer can suppress the leakage current and obtain uniform surface light emission.

The nitrogen-containing film contains a nitrogen element and a carbon element as elements constituting the film, and the abundance ratio of nitrogen atoms and carbon atoms constituting the film is the number of nitrogen atoms / (number of nitrogen atoms + number of carbon atoms)> 1/8
It is preferable to satisfy the relationship.
Thus, when the ratio of the number of nitrogen atoms in the nitrogen-containing film is high, the total number of metal-nitrogen bonds increases, and as a result, electron injection characteristics are further improved due to stronger polarization. The number of nitrogen atoms / (number of nitrogen atoms + number of carbon atoms) in the nitrogen-containing film is more preferably larger than 1/5.
The abundance ratio of nitrogen element and carbon element in the nitrogen-containing film can be measured by photoelectron spectroscopy (XPS).

As long as the nitrogen-containing films of the above (3) and (4) are formed by decomposing the nitrogen-containing compound on the metal oxide layer, the method for decomposing the nitrogen-containing compound is not particularly limited. It is preferably formed by decomposing the contained compound by heating.
When the nitrogen-containing compound is decomposed by heating, the bond between the metal atom and the nitrogen atom in the metal oxide layer is strengthened, whereby the organic electroluminescent device exhibits high driving stability over a longer period of time. .

Accordingly, the nitrogen-containing film is most preferably formed by a method in which a solution containing a nitrogen-containing compound is applied on the metal oxide layer, and then the nitrogen-containing compound is decomposed by heating. By forming by this method, the effect of suppressing leakage current, obtaining uniform surface light emission, and the effect that the organic electroluminescence device exhibits high driving stability over a longer period of time can be obtained.
A method of manufacturing such a HOILED device, that is, a method of manufacturing an organic electroluminescent device having a structure in which a plurality of layers are laminated between an anode and a cathode formed on a substrate, And a step of applying a solution containing a nitrogen-containing compound on the metal oxide layer, and a step of producing a layer comprising the nitrogen-containing film of the present invention by heat treatment at a temperature at which the nitrogen-containing compound is decomposed. A method for producing an organic electroluminescent element is also one aspect of the present invention.

The heat treatment for decomposing the nitrogen-containing compound is preferably performed in the atmosphere. By carrying out under air | atmosphere, decomposition | disassembly of a nitrogen-containing compound is fully accelerated | stimulated and an organic electroluminescent element can exhibit higher driving stability over a long period of time.
The temperature of the heat treatment for decomposing the nitrogen-containing compound is preferably 80 to 200 ° C., and the time is preferably 1 to 30 minutes.
What is necessary is just to set the temperature and time of heat processing suitably according to the kind of nitrogen-containing compound in the said range. For example, when using a polymer having the following polyalkyleneimine structure in the main chain skeleton as a nitrogen-containing compound, the decomposition temperature increases as the molecular weight of the polymer increases. The temperature and time of the heat treatment can be appropriately set with reference to the heat treatment conditions.
Whether or not the nitrogen-containing compound is decomposed can be confirmed by X-ray photoelectron spectroscopy (XPS) measurement.

The nitrogen-containing film is formed by performing a step of decomposing a nitrogen-containing compound on the metal oxide layer and then performing a step of cleaning the surface of the film with an organic solvent such as ethanol or methoxyethanol. Also good.

Examples of the nitrogen-containing compound include pyrrolidones such as polyvinyl pyrrolidone, pyrroles such as polypyrrole or anilines such as polyaniline, or pyridines such as polyvinyl pyridine, as well as pyrrolidines, imidazoles, and piperidines. , Pyrimidines, triazines and other compounds having a nitrogen-containing heterocycle, and amine compounds. Of these, compounds having a high nitrogen content are preferred, and polyamines or triazine ring-containing compounds are preferred.
Polyamines are suitable because the ratio of the number of nitrogen atoms to the total number of atoms constituting the compound is high, so that the organic electroluminescent device has high electron injection properties and driving stability.
As the polyamines, those capable of forming a layer by coating are preferable, and they may be low molecular compounds or high molecular compounds. A polyalkylene polyamine such as diethylenetriamine is preferably used as the low molecular compound, and a polymer having a polyalkyleneimine structure is preferably used as the high molecular compound. Polyethyleneimine is particularly preferable.
In addition, a low molecular compound means the compound which is not a high molecular compound (polymer) here, and does not necessarily mean a compound with a low molecular weight.

Among the polyamines described above, the use of a linear polymer having a polyalkyleneimine structure in the main chain skeleton is one of the preferred embodiments of the present invention.
Among the polyamines, by using a polymer having such a structure, the device driving stability and the device lifetime are improved. This is presumed to be because the polymer having such a polyalkyleneimine structure in the main chain skeleton is a solid because it has a linear structure, and thus exists stably in the device.
The nitrogen-containing film formed on the metal oxide layer by the polymer having a linear structure having such a polyalkyleneimine structure in the main chain skeleton becomes the nitrogen-containing film (1).
In addition, the polymer having a linear structure having a polyalkyleneimine structure in the main chain skeleton may be one in which most of the polyalkyleneimine structures forming the main chain skeleton are linearly linked and partially branched. It may have a structure. Preferably, 80% or more of the polyalkyleneimine structures forming the main chain skeleton are linearly connected, more preferably 90% or more are linearly connected, and more preferably, More than 95% are linearly linked, and most preferably, 100% or more of the polyalkyleneimine structure forming the main chain skeleton is linearly linked.

The polyalkyleneimine structure of the polymer having the polyalkyleneimine structure is preferably a structure formed of an alkyleneimine having 2 to 4 carbon atoms. More preferably, it is a structure formed by alkyleneimine having 2 or 3 carbon atoms.

The polymer having the polyalkyleneimine structure may be any polymer having a polyalkyleneimine structure in the main chain skeleton, and may be a copolymer having a structure other than the polyalkyleneimine structure.

When the polymer having a polyalkyleneimine structure has a structure other than the polyalkyleneimine structure, examples of the monomer that is a raw material for a structure other than the polyalkyleneimine structure include ethylene, propylene, butene, acetylene, and acrylic acid. , Styrene, vinyl carbazole, or the like, and one or more of these can be used. Moreover, the thing of the structure where the hydrogen atom couple | bonded with the carbon atom of these monomers was substituted by the other organic group can also be used suitably. Examples of the other organic group substituted with a hydrogen atom include a hydrocarbon group having 1 to 10 carbon atoms that may contain at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, and a sulfur atom. Is mentioned.

The polymer having a polyalkyleneimine structure is preferably 50% by mass or more of the monomer that forms a polyalkyleneimine structure out of 100% by mass of the monomer component that forms the main chain skeleton of the polymer. . More preferably, it is 66 mass% or more, More preferably, it is 80 mass% or more. Most preferably, the monomer forming the polyalkyleneimine structure is 100% by mass, that is, the polymer having the polyalkyleneimine structure is a homopolymer of polyalkyleneimine.

The polymer having a polyalkyleneimine structure preferably has a weight average molecular weight of 100,000 or less. By using a material having such a weight average molecular weight and performing a heat treatment at a temperature at which the polymer is decomposed to form a layer, the organic electroluminescent device can be made more excellent in driving stability. More preferably, it is 10,000 or less, More preferably, it is 100-1000.
Further, when the polymer having a polyalkyleneimine structure is a polymer having a linear structure as described above, the weight average molecular weight of the polymer is more preferably 250,000 or less, and still more preferably 10,000 to 50,000. It is.
The weight average molecular weight can be determined by GPC (gel permeation chromatography) measurement under the following conditions.
Measuring instrument: Waters Alliance (2695) (trade name, manufactured by Waters)
Molecular weight column: TSKguard column α, TSKgel α-3000, TSKgel α-4000, TSKgel α-5000 (all manufactured by Tosoh Corporation) are connected in series. Eluent: 100 mM boric acid aqueous solution 14304 g and 50 mM sodium hydroxide aqueous solution 96 g Standard material for solution calibration curve in which 3600 g of acetonitrile is mixed: Polyethylene glycol (manufactured by Tosoh Corporation)
Measurement method: The molecular weight is measured by dissolving the object to be measured in the eluent so that the solid content is about 0.2% by mass, and using the product filtered through a filter as the measurement sample.

As the above-mentioned triazine ring-containing compound, melamine and guanamines are more suitable because they are nitrogen-containing cyclic compounds, and the ratio of the number of nitrogen atoms to the total number of atoms constituting the compound is high and they are rigid. When a film made of melamine or guanamine is formed on the metal oxide layer, the above-described high nitrogen-containing film (2) is obtained.

As said triazine ring containing compound, 1 type or 2 types of compounds which have melamine / guanamine skeletons, such as melamine and guanamines, such as melamine and benzoguanamine / acetoguanamine, methylolated melamine and guanamine, melamine resin / guanamine resin Although the above can be used, among these, a melamine is preferable at a point with the high ratio of the nitrogen atom in all the atoms which comprise a compound.

Moreover, as a compound and amine compound which have the said nitrogen-containing heterocyclic ring, the polymer which has a repeating unit of the structure represented by following formula (1)-(9), the triethylamine of Formula (10), Formula (11) Ethylenediamine can also be suitably used.

Further, when these nitrogen-containing compounds are decomposed on the metal oxide layer, the nitrogen-containing film (3) or the high nitrogen-containing film (4) is obtained. It is considered that the decomposition product of the nitrogen-containing compound can be deposited more densely on the metal oxide layer by using a compound having a high nitrogen-containing ratio such as a polyamine or a triazine ring-containing compound as the nitrogen-containing compound. . Such a nitrogen-containing thin film on a metal oxide is also one of the inventions of this patent. The nitrogen-containing thin film will be described later.

The average thickness of the nitrogen-containing film in the present invention is 3 to 150 nm. When the nitrogen-containing film has such an average thickness, the above-described effect of having the nitrogen-containing film can be satisfactorily exhibited. The average thickness of the nitrogen-containing film is preferably 5 to 100 nm. More preferably, it is 5 to 50 nm. In particular, in the case of a nitrogen-containing film obtained by decomposing a nitrogen-containing compound, the thickness is preferably 5 to 100 nm, more preferably 5 to 50 nm.
The average thickness of the nitrogen-containing film can be measured at the time of film formation by a contact type step meter. The contact level difference meter greatly depends on the measurement environment when measuring an ultra-thin film, resulting in large variations in measurement values. Therefore, when measuring the average thickness in this patent, it is determined by the average value of a plurality of measurements.

The organic electroluminescent element of the present invention has an anode and a cathode, and one or more organic compound layers sandwiched between the anode and the cathode, and between the cathode and the organic compound layer, It is preferable to have a metal oxide layer and further to have a layer comprising the nitrogen-containing film of the present invention between the metal oxide layer and the organic compound layer. Here, the organic compound layer is a layer including a light emitting layer and, if necessary, an electron transport layer and a hole transport layer.
Among them, the organic electroluminescent device of the present invention is an organic-inorganic hybrid organic electroluminescent device having a cathode formed adjacent to a substrate and having a metal oxide layer between the anode and the cathode, and emitting light. A layer and an anode, an electron injection layer between the cathode and the light emitting layer, and an electron transport layer as necessary, and a hole transport layer and / or a positive layer between the anode and the light emitting layer. An element having a hole injection layer is preferable. Although the organic electroluminescent element of this invention may have another layer between these each layer, it is preferable that it is an element comprised only from these each layer. That is, it is preferably an element in which a cathode, an electron injection layer, and if necessary, an electron transport layer, a light emitting layer, a hole transport layer and / or a hole injection layer, and an anode are laminated in this order. Each of these layers may be composed of one layer, or may be composed of two or more layers.
As described above, since the nitrogen-containing film has excellent electron injection characteristics, it is preferably used on the electron injection side, that is, the cathode side. Further, as described later, the metal oxide layer is preferably laminated as a part of the cathode or one layer of the electron injection layer and / or as a part of the anode or one layer of the hole injection layer.
In the organic electric field element having the above configuration, when the element does not have an electron transport layer, the electron injection layer and the light emitting layer are adjacent to each other. When the device has only one of a hole transport layer and a hole injection layer, the one layer is stacked adjacent to the light emitting layer and the anode, and the device transports the hole. When both the layer and the hole injection layer are provided, these layers are laminated adjacently in the order of the light emitting layer, the hole transport layer, the hole injection layer, and the anode.

In the organic electroluminescent element of the present invention, as a material for forming the light emitting layer, any compound that can be usually used as the material of the light emitting layer can be used, whether it is a low molecular compound or a high molecular compound. It is also possible to use a mixture of these.
In the present invention, the low molecular weight material means a material that is not a polymer material (polymer), and does not necessarily mean an organic compound having a low molecular weight.

Examples of the polymer material for forming the light emitting layer include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), and poly (alkyl, phenylacetylene) (PAPA); Poly (para-phenvinylene) (PPV), poly (2,5-dialkoxy-para-phenylenevinylene) (RO-PPV), cyano-substituted-poly (para-phenvinylene) (CN-PPV), poly ( Polyparaphenylene vinylenes such as 2-dimethyloctylsilyl-para-phenylene vinylene (DMOS-PPV), poly (2-methoxy, 5- (2′-ethylhexoxy) -para-phenylene vinylene) (MEH-PPV) Compound; poly (3-alkylthiophene) (PAT), poly (oxy) Polythiophene compounds such as propylene) triol (POP); poly (9,9-dialkylfluorene) (PDAF), poly (dioctylfluorene-alt-benzothiadiazole) (F8BT), α, ω-bis [N, N ′ -Di (methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2,7-zyl] (PF2 / 6am4), poly (9,9-dioctyl-2,7-divinylene) Polyfluorene-based compounds such as fluorenyl-ortho-co (anthracene-9,10-diyl); poly (para-phenylene) (PPP), poly (1,5-dialkoxy-para-phenylene) (RO— Polyparaphenylene compounds such as PPP); polycarbazo such as poly (N-vinylcarbazole) (PVK) A polysilane compound such as poly (methylphenylsilane) (PMPS), poly (naphthylphenylsilane) (PNPS), poly (biphenylylphenylsilane) (PBPS); and further, Japanese Patent Application No. 2010-230995, Examples thereof include boron compound polymer materials described in Japanese Patent Application No. 2011-6457.

Examples of the low molecular weight material forming the light emitting layer include a tricoordinate iridium complex having 2,2′-bipyridine-4,4′-dicarboxylic acid as a ligand, and factory (2-phenylpyridine). Iridium (Ir (ppy) ₃ ), 8-hydroxyquinoline aluminum (Alq ₃ ), tris (4-methyl-8 quinolinolate) aluminum (III) (Almq ₃ ), 8-hydroxyquinoline zinc (Znq ₂ ), (1, 10-phenanthroline) -tris- (4,4,4-trifluoro-1- (2-thienyl) -butane-1,3-dionate) europium (III) (Eu (TTA) ₃ (phen)), 2, Various metal complexes such as 3,7,8,12,13,17,18-octaethyl-21H, 23H-porphine platinum (II); Benzene compounds such as zen (DSB) and diamino distyryl benzene (DADSB); naphthalene compounds such as naphthalene and nile red; phenanthrene compounds such as phenanthrene; chrysene compounds such as chrysene and 6-nitrochrysene A perylene compound such as perylene, N, N′-bis (2,5-di-t-butylphenyl) -3,4,9,10-perylene-di-carboximide (BPPC); Coronene compounds; anthracene compounds such as anthracene and bisstyrylanthracene; pyrene compounds such as pyrene; 4- (di-cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM) pyran compounds; acridine compounds such as acridine Compound; stilbene compound such as stilbene; thiophene compound such as 2,5-dibenzoxazole thiophene; benzoxazole compound such as benzoxazole; benzimidazole compound such as benzimidazole; 2,2′- Benzothiazole compounds such as (para-phenylenedivinylene) -bisbenzothiazole; butadiene compounds such as bistyryl (1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene; naphthalimides such as naphthalimide Phthalimide compounds; coumarin compounds such as coumarin; perinone compounds such as perinone; oxadiazole compounds such as oxadiazole; aldazine compounds; 1,2,3,4,5-pentaphenyl-1 , 3-Cyclopentadiene Cyclopentadiene compounds such as PPCP); quinacridone compounds such as quinacridone and quinacridone red; pyridine compounds such as pyrrolopyridine and thiadiazolopyridine; 2,2 ′, 7,7′-tetraphenyl-9, Spiro compounds such as 9′-spirobifluorene; metal or metal-free phthalocyanine compounds such as phthalocyanine (H ₂ Pc) and copper phthalocyanine; and Japanese Patent Application Laid-Open No. 2009-155325 and Japanese Patent Application No. 2010-230995, Examples thereof include boron compound materials described in Japanese Patent Application No. 2011-6458.

Although the average thickness of the said light emitting layer is not specifically limited, It is preferable that it is 10-150 nm. More preferably, it is 20-100 nm, More preferably, it is 40-100 nm.
The average thickness of the light emitting layer can be measured with a quartz oscillator thickness meter in the case of a low molecular compound, and with a contact-type step meter in the case of a polymer compound.

When the organic electroluminescent element of the present invention has an electron transport layer, as the material, any compound that can be usually used as a material for the electron transport layer can be used, or a mixture thereof may be used.
Examples of compounds that can be used as the material for the electron transport layer include pyridine derivatives such as tris-1,3,5- (3 ′-(pyridin-3 ″ -yl) phenyl) benzene (TmPyPhB), ( Quinoline derivatives such as 2- (3- (9-carbazolyl) phenyl) quinoline (mCQ)), pyrimidine derivatives such as 2-phenyl-4,6-bis (3,5-dipyridylphenyl) pyrimidine (BPyPPM), Pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), 2,4-bis (4-biphenyl) -6- (4 ′-(2-pyridinyl) -4-biphenyl)-[1,3,5] triazine Triazine derivatives such as (MPT), 3-phenyl-4- (1′-naphthyl) -5-phenyl-1,2,4-triazole (T A triazole derivative such as Z), an oxazole derivative, an oxadiazole derivative such as 2- (4-biphenylyl) -5- (4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), Imidazole derivatives such as 2,2 ′, 2 ″-(1,3,5-bentriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBI), aromatic ring tetracarboxylic such as naphthalene and perylene Various metal complexes represented by acid anhydride, bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (Zn (BTZ) ₂ ), tris (8-hydroxyquinolinato) aluminum (Alq3), 2,5- Shiro such as bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) An organosilane derivative represented by a ruthenium derivative can be used, and one or more of these can be used.
Among these, a metal complex such as Alq ₃ and a pyridine derivative such as TmPyPhB are preferable.

When the organic electroluminescent element of the present invention has a hole transport layer, various p-type high molecular materials and various p-type low molecular materials are used alone as the hole transport organic material used as the hole transport layer. Or they can be used in combination.
Examples of the p-type polymer material (organic polymer) include polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly (N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, Examples thereof include polyalkylthiophene, polyhexylthiophene, poly (p-phenylene vinylene), polytinylene vinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin, and derivatives thereof.
These compounds can also be used as a mixture with other compounds. As an example, the polythiophene-containing mixture includes poly (3,4-ethylenedioxythiophene / styrene sulfonic acid) (PEDOT / PSS).

Examples of the p-type low molecular weight material include 1,1-bis (4-di-para-triaminophenyl) cyclohexane, 1,1′-bis (4-di-para-tolylaminophenyl)- Arylcycloalkane compounds such as 4-phenyl-cyclohexane, 4,4 ′, 4 ″ -trimethyltriphenylamine, N, N, N ′, N′-tetraphenyl-1,1′-biphenyl-4, 4′-diamine, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine (TPD1), N, N′-diphenyl-N , N′-bis (4-methoxyphenyl) -1,1′-biphenyl-4,4′-diamine (TPD2), N, N, N ′, N′-tetrakis (4-methoxyphenyl) -1,1 '-Biphenyl-4,4'-diamine (TPD3), N N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (α-NPD), arylamine compounds such as TPTE, N, N, N ', N'-tetraphenyl-para-phenylenediamine, N, N, N', N'-tetra (para-tolyl) -para-phenylenediamine, N, N, N ', N'-tetra (meta-tolyl) ) -Phenylenediamine compounds such as meta-phenylenediamine (PDA), carbazole compounds such as carbazole, N-isopropylcarbazole, N-phenylcarbazole, stilbenes, and stilbenes such as 4-di-para-tolylaminostilbene. system compounds, oxazole-based compounds such as _{O x} Z, triphenylmethane, triphenylmethane compounds such as m-MTDATA, 1-off Pyrazoline compounds such as nil-3- (para-dimethylaminophenyl) pyrazoline, benzine (cyclohexadiene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, 1,3,4-oxa Diazole, oxadiazole compounds such as 2,5-di (4-dimethylaminophenyl) -1,3,4-oxadiazole, anthracene, anthracene such as 9- (4-diethylaminostyryl) anthracene Compound, fluorenone, 2,4,7-trinitro-9-fluorenone, fluorenone compound such as 2,7-bis (2-hydroxy-3- (2-chlorophenylcarbamoyl) -1-naphthylazo) fluorenone, polyaniline Aniline compounds, silane compounds Pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo- (3,4-c) pyrrolopyrrole, fluorene compounds such as florene, porphyrins, porphyrins such as metal tetraphenylporphyrin Compounds, quinacridone compounds such as quinacridone, phthalocyanine, copper phthalocyanine, tetra (t-butyl) copper phthalocyanine, metal or metal-free phthalocyanine compounds such as iron phthalocyanine, copper naphthalocyanine, vanadyl naphthalocyanine, monochlorogallium naphthalocyanine Of metal or metal-free naphthalocyanine compounds such as N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine, N, N, N ′, N′-tetraphenylbenzidine Benzidine compounds like And the like.

When the organic electroluminescent element of the present invention has an electron transport layer or a hole transport layer, the average thickness of these layers is not particularly limited, but is preferably 10 to 150 nm. More preferably, it is 20-100 nm, More preferably, it is 40-100 nm.
The average thickness of the electron transport layer and the hole transport layer can be measured with a quartz oscillator film thickness meter in the case of a low molecular compound, and with a contact step meter in the case of a polymer compound.

The organic electroluminescent element of the present invention has a metal oxide layer either from the cathode to the light emitting layer, or from the anode to the light emitting layer, or both. It is preferable to have a metal oxide layer both between the light emitting layer and the anode. The metal oxide layer between the cathode and the light emitting layer is the first metal oxide layer, and the metal oxide layer between the anode and the light emitting layer is the second metal oxide layer, and the organic electroluminescent device of the present invention An example of the configuration of the preferred element is that the cathode, the first metal oxide layer, the layer comprising a nitrogen-containing film, the light emitting layer, the hole transport layer, the second metal oxide layer, and the anode are adjacent in this order. It is a laminated structure. In addition, you may have an electron carrying layer between the layer which consists of a nitrogen-containing film | membrane, and a light emitting layer as needed. The importance of the metal oxide layer is higher in the first metal oxide layer, and the second metal oxide layer can be replaced by an organic material extremely deep in the lowest unoccupied molecular orbital, for example, HATCN. .

The first metal oxide layer is a layer composed of a single layer of a single metal oxide film, or a layer of a semiconductor or insulator stacked thin film that is a single layer or a layer in which two or more types of metal oxides are stacked and / or mixed. Is a layer. The metal elements constituting the metal oxide include magnesium, calcium, strontium, barium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, indium, gallium, iron, cobalt, nickel, copper , Zinc, cadmium, aluminum, and silicon. Among these, it is preferable that at least one of the metal elements constituting the laminated or mixed metal oxide layer is a layer made of magnesium, aluminum, calcium, zirconium, hafnium, silicon, titanium, zinc, and among them, a single metal If it is an oxide, it is preferable to include a metal oxide selected from the group consisting of magnesium oxide, aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide, titanium oxide, and zinc oxide.

Examples of the layer obtained by laminating and / or mixing the single substance or two or more kinds of metal oxides include titanium oxide / zinc oxide, titanium oxide / magnesium oxide, titanium oxide / zirconium oxide, titanium oxide / aluminum oxide, titanium oxide / Lamination and / or combination of metal oxides such as hafnium oxide, titanium oxide / silicon oxide, zinc oxide / magnesium oxide, zinc oxide / zirconium oxide, zinc oxide / hafnium oxide, zinc oxide / silicon oxide, calcium oxide / aluminum oxide Mixed, titanium oxide / zinc oxide / magnesium oxide, titanium oxide / zinc oxide / zirconium oxide, titanium oxide / zinc oxide / aluminum oxide, titanium oxide / zinc oxide / hafnium oxide, titanium oxide / zinc oxide / silicon oxide, Such as indium oxide / gallium oxide / zinc oxide Like those laminating and / or mixing a combination of species of metal oxides. These include IGZO, which is an oxide semiconductor that exhibits good characteristics as a special composition, and 12CaO.7Al ₂ O ₃ , which is an electride.
These first metal oxide layers can be said to be electron injection layers and electrodes (cathodes).
In the present invention, an object having a sheet resistance lower than 100Ω / □ is classified as a conductor, and an object having a sheet resistance higher than 100Ω / □ is classified as a semiconductor or an insulator. Therefore, ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped indium oxide), etc., known as transparent electrodes The thin film does not correspond to one layer constituting the first metal oxide layer of the present invention because it has high conductivity and is not included in the category of semiconductor or insulator.

The metal oxide that forms the second metal oxide layer is not particularly limited, but vanadium oxide (V ₂ O ₅ ), molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), ruthenium oxide (RuO ₂ ). 1 type or 2 types or more can be used. Among these, those containing vanadium oxide or molybdenum oxide as a main component are preferable. When the second metal oxide layer is composed mainly of vanadium oxide or molybdenum oxide, the second metal oxide layer injects holes from the anode and transports them to the light emitting layer or the hole transport layer. The function as the hole injection layer is excellent. In addition, vanadium oxide or molybdenum oxide has its own high hole transport property, so that it is possible to suitably prevent the efficiency of hole injection from the anode to the light emitting layer or the hole transport layer from being lowered. There is. More preferably, it is composed of vanadium oxide and / or molybdenum oxide.

The average thickness of the first metal oxide layer is acceptable from 1 nm to about several μm, but is preferably 1 to 1000 nm from the viewpoint of an organic electroluminescent device that can be driven at a low voltage. More preferably, it is 2 to 100 nm.
The average thickness of the second metal oxide layer is not particularly limited, but is preferably 1 to 1000 nm. More preferably, it is 5-50 nm.
The average thickness of the first metal oxide layer can be measured by a stylus profilometer or spectroscopic ellipsometry.
The average thickness of the second metal oxide layer can be measured at the time of film formation with a crystal oscillator thickness meter.

In the organic electroluminescent element of the present invention, as the anode and the cathode, known conductive materials can be used as appropriate, but at least one of them is preferably transparent for light extraction. Examples of known transparent conductive materials include ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), and FTO (fluorine-doped indium oxide). Is raised. Examples of the opaque conductive material include calcium, magnesium, aluminum, tin, indium, copper, silver, gold, platinum, and alloys thereof.
Among these, ITO, IZO, and FTO are preferable as the cathode.
Among these, Au, Ag, and Al are preferable as the anode.
As described above, since the metal generally used for the anode can be used for the cathode and the anode, it is possible to easily realize light extraction from the upper electrode (in the case of a top emission structure). Various selections can be made for each electrode. For example, Al is used for the lower electrode and ITO is used for the upper electrode.

The average thickness of the cathode is not particularly limited, but is preferably 10 to 500 nm. More preferably, it is 100-200 nm. The average thickness of the cathode can be measured by a stylus profilometer or spectroscopic ellipsometry.
The average thickness of the anode is not particularly limited, but is preferably 10 to 1000 nm. More preferably, it is 30-150 nm. Even when an opaque material is used, for example, by setting the average thickness to about 10 to 30 nm, it can be used as a top emission type or transparent type anode.
The average thickness of the anode can be measured at the time of film formation with a crystal oscillator thickness meter.

In the organic electroluminescent device of the present invention, the method for forming the layer formed from the organic compound is not particularly limited, and various methods can be appropriately used according to the characteristics of the material. Spin coating method, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, slit coating method, dip coating method, spray coating method, screen printing method, flexographic printing method, offset The film can be formed using various coating methods such as a printing method and an ink jet printing method. Among these, the spin coat method and the slit coat method are preferable because the film thickness can be more easily controlled. When not applied or when the solvent solubility is low, a vacuum deposition method, an ESDUS (Evaporative Spray Deposition Ultra-dilute Solution) method, or the like can be cited as a suitable example.

When the layer formed from the organic compound is formed by applying an organic compound solution, examples of the solvent used for dissolving the organic compound include nitric acid, sulfuric acid, ammonia, hydrogen peroxide, water, carbon disulfide. , Inorganic solvents such as carbon tetrachloride, ethylene carbonate, ketone solvents such as methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), cyclohexanone, methanol, ethanol, isopropanol, Alcohol solvents such as ethylene glycol, diethylene glycol (DEG), glycerin, diethyl ether, diisopropyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (T P), ether solvents such as anisole, diethylene glycol dimethyl ether (diglyme), diethylene glycol ethyl ether (carbitol), cellosolv solvents such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, aliphatic carbonization such as hexane, pentane, heptane, cyclohexane Hydrogen solvents, aromatic hydrocarbon solvents such as toluene, xylene, benzene, aromatic heterocyclic compounds solvents such as pyridine, pyrazine, furan, pyrrole, thiophene, methylpyrrolidone, N, N-dimethylformamide (DMF), Amide solvents such as N, N-dimethylacetamide (DMA), halogen compound solvents such as chlorobenzene, dichloromethane, chloroform, 1,2-dichloroethane, ethyl acetate, methyl acetate, ethyl formate, etc. Tellurium solvents, sulfur compound solvents such as dimethyl sulfoxide (DMSO), sulfolane, nitrile solvents such as acetonitrile, propionitrile, acrylonitrile, organic acid solvents such as formic acid, acetic acid, trichloroacetic acid, trifluoroacetic acid Various organic solvents, mixed solvents containing these, etc. are mentioned.
Among these, as the solvent, a nonpolar solvent is suitable, for example, an aromatic hydrocarbon solvent such as xylene, toluene, cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene, tetramethylbenzene, pyridine, pyrazine, furan, Examples include aromatic heterocyclic compound solvents such as pyrrole, thiophene, and methylpyrrolidone, and aliphatic hydrocarbon solvents such as hexane, pentane, heptane, and cyclohexane. These can be used alone or in combination.

When polyamines are used as the nitrogen-containing compound, water or a lower alcohol can be used as a solvent for the solution containing the nitrogen-containing compound. As the lower alcohol, an alcohol having 1 to 4 carbon atoms is preferably used, and methanol, ethanol, propanol, ethoxyethanol, methoxyethanol or the like can be used alone or in combination.

The cathode, anode, and oxide layer can be formed by sputtering, vacuum deposition, sol-gel, spray pyrolysis (SPD), atomic layer deposition (ALD), vapor deposition, liquid deposition, etc. Can be formed. Metal foil bonding can also be used to form the anode and cathode. These methods are preferably selected according to the characteristics of the material of each layer, and the manufacturing method may be different for each layer. Among these, it is more preferable to form the second metal oxide layer using a vapor deposition method. According to the vapor deposition method, the surface of the organic compound layer can be formed cleanly and in good contact with the anode, and as a result, the effect of having the second metal oxide layer as described above. Becomes more prominent.

For the purpose of further improving the characteristics of the organic electroluminescent device of the present invention, for example, a hole blocking layer, an electronic device layer and the like may be included as necessary. As a material for forming these layers, materials usually used for forming these layers can be used, and the layers can be formed by a method usually used for forming these layers.

The organic electroluminescent device of the present invention does not require strict sealing as compared with an organic electroluminescent device in which all layers constituting the device are composed of an organic compound, but may be sealed if necessary. . As the sealing step, a normal method can be used as appropriate. For example, a method of adhering a sealing container in an inert gas, a method of forming a sealing film directly on the organic EL element, or the like can be given. In addition to these, a method of enclosing a moisture absorbing material may be used in combination.

The organic electroluminescent element of the present invention is an organic electroluminescent element having an inverted structure in which a cathode is formed adjacent to a substrate. The organic electroluminescence device of the present invention may be a top emission type that extracts light to the side opposite to the side where the substrate is present, or may be a bottom emission type that extracts light to the side where the substrate is present. .
As the material of the substrate, resin materials such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, polyarylate, quartz glass, soda glass, etc. A glass material etc. are mentioned, These 1 type (s) or 2 or more types can be used.
In the case of the top emission type, an opaque substrate can be used. For example, an oxide film (insulating film) is formed on the surface of a ceramic substrate such as alumina or a metal substrate such as stainless steel. A substrate made of a resin material or the like can also be used.

The average thickness of the substrate is preferably 0.1 to 30 mm. More preferably, it is 0.1-10 mm.
The average thickness of the substrate can be measured with a digital multimeter or a caliper.

The electroluminescent element of the present invention can emit light by applying a voltage (usually 15 volts or less) between the anode and the cathode. Normally, a DC voltage is applied, but an AC component may be included.
The organic electroluminescent element of the present invention can change the emission color by appropriately selecting the material of the organic compound layer, and can also obtain a desired emission color by using a color filter or the like in combination. Therefore, it can be suitably used as a light emitting part of a display device or a lighting device. In particular, a display device combined with an oxide TFT is preferable because of its reverse structure.
Such a display device including the organic electroluminescent element of the present invention and an illumination device including the organic electroluminescent element of the present invention are also one aspect of the present invention.

As described above, the organic electroluminescent device of the present invention has a layer made of a nitrogen-containing film on the metal oxide layer, so that the electron injection characteristics are improved and the luminous efficiency is excellent, and the driving stability of the device and the device are improved. The service life is also excellent.
Such an effect of improving the electron injection characteristics is beneficial not only for organic electroluminescence elements but also for other optoelectronic devices such as solar cells and organic semiconductors, which contributes to performance improvement. Nitrogen-containing films that contribute to the performance improvement of such optoelectronic devices, that is,
A film containing nitrogen, the film being formed on a metal-containing substrate and formed of a solid nitrogen-containing compound, or nitrogen and carbon elements as elements constituting the film The abundance ratio of nitrogen atoms and carbon atoms constituting the film is the number of nitrogen atoms / (number of nitrogen atoms + number of carbon atoms)> 1/8
A nitrogen-containing film characterized by satisfying this relationship is also one aspect of the present invention.
The preferable form and manufacturing method of the nitrogen-containing film of the present invention are the same as those of the layer made of the nitrogen-containing film in the organic electroluminescence device of the present invention described above.

The organic electroluminescent element of the present invention is an organic electroluminescent element having an organic-inorganic hybrid type reverse structure that has the above-described configuration and does not require strict sealing, has excellent luminous efficiency, and repeats light emission. It has high driving stability with excellent stability and uniformity of light emission, and has a long device life. The organic electroluminescent element of the present invention having these characteristics can be suitably used for a display device, a certification device, and the like.

It is the schematic which showed an example of the laminated structure of the organic electroluminescent element shown by this invention. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 1, and (b) current density-current efficiency characteristic. (C-1) Continuous drive characteristics under constant current density (equivalent to 100 cd / m ² ) of the organic electroluminescent device produced in Example 1, and (c-2) under constant current density (equivalent to 1000 cd / m ²⁾ It is the figure which showed the measurement result of the continuous drive characteristic in). It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in the comparative example 1, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 2, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic under the (c-2) constant current density (equivalent to 1000 cd / m < ² >) of the organic electroluminescent element produced in Example 2. FIG. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 3, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic under the (c-2) constant current density (equivalent to 1000 cd / m < ² >) of the organic electroluminescent element produced in Example 3. FIG. The measurement results of (a) voltage-current density / luminance characteristics and (c-1) continuous drive characteristics under a constant current density (equivalent to 100 cd / m ² ) of the organic electroluminescence device fabricated in Example 4 are shown. It is a figure. It is the figure which showed the measurement result of (a) voltage-current density and luminance characteristic of the organic electroluminescent element produced in Example 5, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic in the organic electroluminescent element (c-1) produced in Example 5 under a constant current density (equivalent to 100 cd / m < ² >). It is the figure which showed the measurement result of (a) voltage-current density and luminance characteristic of the organic electroluminescent element produced in Example 6, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic under the (c-1) constant current density (equivalent to 100 cd / m < ² >) of the organic electroluminescent element produced in Example 6. FIG. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 7, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic under the (c-2) constant current density (equivalent to 1000 cd / m < ² >) of the organic electroluminescent element produced in Example 7. FIG. It is the figure which showed the measurement result of (a) voltage-current density and luminance characteristic of the organic electroluminescent element produced in Example 8, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic under the (c-2) constant current density (equivalent to 1000 cd / m < ² >) of the organic electroluminescent element produced in Example 8. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 9, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic under the (c-1) constant current density (equivalent to 100 cd / m < ² >) of the organic electroluminescent element produced in Example 9. FIG. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 10, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of the continuous drive characteristic under the (c-2) constant current density (equivalent to 1000 cd / m < ² >) of the organic electroluminescent element produced in Example 10. FIG. It is the figure which showed the result of having performed the photoelectron spectroscopy measurement of the nitrogen containing film | membrane produced in manufacture example 1. FIG. It is the figure which showed the result of having performed the photoelectron spectroscopy measurement of the nitrogen-containing film | membrane produced in manufacture example 2. FIG. It is the figure which showed the result of having performed the photoelectron spectroscopy measurement of the nitrogen-containing film | membrane produced in manufacture example 3. FIG. It is the figure which showed the result of having performed the photoelectron spectroscopy measurement of the nitrogen containing film | membrane produced in manufacture example 4. FIG. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 11-1, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 11-2, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in Example 12, and (b) current density-current efficiency characteristic. It is the figure which showed the measurement result of (a) voltage-current density and a brightness | luminance characteristic of the organic electroluminescent element produced in the comparative example 2, and (b) current density-current efficiency characteristic.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

(Production of organic electroluminescence device)
Example 1
[1] A commercially available transparent glass substrate 1 with an ITO electrode layer having an average thickness of 0.7 mm was prepared. At this time, the ITO electrode 2 of the substrate used was patterned to a width of 2 mm. This substrate was subjected to ultrasonic cleaning in acetone and isopropanol for 10 minutes, and then boiled in isopropanol for 5 minutes. This substrate was taken out from isopropanol, dried by nitrogen blowing, and UV ozone cleaning was performed for 20 minutes.
[2] This substrate was fixed again to the substrate holder of the Miratron sputtering apparatus having a zinc metal target. After reducing the pressure to about 1 × 10 ⁻⁴ Pa, sputtering was performed with argon and oxygen introduced, and a zinc oxide layer having a thickness of about 2 nm was formed as the first metal oxide layer 3. At this time, a metal mask was used in combination so that a portion of the ITO electrode was not deposited with zinc oxide for electrode extraction.
[3] The substrate is again cleaned in [1] (ultrasonic cleaning in acetone and isopropanol for 10 minutes, boiled in isopropanol for 5 minutes, then dried by nitrogen blowing, and UV ozone cleaning is performed for 20 minutes. After that, annealing was performed on a hot plate at 400 ° C. for 1 hour.
[4] Next, in order to form the layer 4 of the nitrogen-containing film, a polyethyleneimine (registered trademark: Epomin) manufactured by Nippon Shokubai Co., Ltd. diluted to 0.5% by weight with ethanol was spin-coated under the conditions of 2000 rpm and 30 seconds. did.
The epomin used here was sp003 having a molecular weight of 300.
[5] The thin film (substrate) produced in [4] was annealed at 150 ° C. for 5 minutes on a hot plate in the atmosphere. The average thickness of the nitrogen-containing film layer measured after annealing was 5 nm.
[6] Next, the substrate subjected to the processing of [5] is introduced into a vacuum apparatus, and the pressure is reduced to 1 × 10 ⁻⁴ Pa or less. As the organic compound layer 5, 32.5 nm of Alq ₃ on each turn alpha-NPD as a hole transport layer as a light emitting layer was deposited by 60nm vacuum deposition method.
[7] Next, the second metal oxide layer 6 was formed on the organic compound layer 5. Here, molybdenum oxide was formed by a vacuum evaporation method which is a 10 nm vapor phase film forming method.
[8] Next, an anode 7 was formed on the second metal oxide layer 6 as a final step. Here, aluminum was formed into a film by a 150 nm vacuum evaporation method.
[9] Organic electroluminescence device characteristics (voltage-current density / luminance characteristics, current density-current efficiency characteristics, constant current density) by the following (measurement of light emission characteristics of organic electroluminescence elements) and (measurement of lifetime characteristics of organic electroluminescence elements) The lower (equivalent to 100 cd / m ² , continuous drive characteristics at 1000 cd / m ² ) was measured. The measurement results are shown in FIGS. 2-1 and 2-2, respectively (a), (b), (c-1) and (c-2).

(Measurement of light emission characteristics of organic electroluminescence device)
Voltage application to the device and current measurement were performed using a “2400 type source meter” manufactured by Keithley. Luminance was measured with “BM-7” manufactured by Topcon Corporation. The measurement was performed in an argon atmosphere.
(Measurement of lifetime characteristics of organic electroluminescent devices)
Application of voltage to the element and measurement of relative luminance were performed using an “organic EL lifetime measuring device” manufactured by System Giken. This device can measure relative luminance by a photodiode while automatically adjusting the voltage so that a constant current flows through the element. The current value was set for each element so that the luminance at the start of measurement was 100 cd / m ² and 1000 cd / m ² . These results are shown in (c-1) and (c-2) in the respective examples and comparative examples.
In addition, the description such as “t _1/2 = 200h @ 1000 cd / m ² ” outside the column of FIGS. (C-1) and (c-2) represents a half-life, and in the above case, the initial 1000 cd / m ^This means that the luminance half-life when the current density equivalent to ^{2 is} continuously applied at a constant current is 200 hours.

(Comparative Example 1)
An organic electroluminescent device was produced in the same manner except that steps [4] and [5] in Example 1 were omitted, and the voltage-current density / luminance characteristics and current density of the organic electroluminescent device were obtained in the same manner as in Example 1. -Current efficiency characteristics were measured. These results are shown in FIGS. 3 (a) and 3 (b), respectively.

(Example 2)
An organic electroluminescent device was produced in the same manner except that the step [4] in Example 1 was changed to the following [4-2], and the voltage-current density of the organic electroluminescent device in the same manner as in Example 1 was obtained. The luminance characteristics, current density-current efficiency characteristics, and continuous drive characteristics under a constant current density (equivalent to 1000 cd / m ² ) were measured. These results are shown in FIGS. 4-1 and 4-2 (a), (b) and (c-2), respectively. The average film thickness of the nitrogen-containing film was 6 nm.
[4-2] Next, in order to form the layer 4 of the nitrogen-containing film, a polyethyleneimine (registered trademark: epomine) manufactured by Nippon Shokubai Co., Ltd. was diluted to 0.5% by weight with ethanol under the condition of 2000 rpm for 30 seconds. Spin coat. The epomin used here is P1000 having a molecular weight of 70,000.

(Example 3)
An organic electroluminescent element was produced in the same manner as in Example 1 except that the steps [4] and [5] in Example 1 were changed to [4-3] and [5-3] below. The voltage-current density / luminance characteristics, current density-current efficiency characteristics, and continuous drive characteristics under a constant current density (equivalent to 1000 cd / m ² ) of the light-emitting element were measured. These results are shown in FIGS. 5-1, 5-2 (a), (b) and (c-2), respectively. The average film thickness of the nitrogen-containing film layer was 5 nm.
[4-3] Next, in order to form the layer 4 of the nitrogen-containing film, a solution obtained by diluting diethylenetriamine to 1.0% by weight with ethanol is spin-coated at 2000 rpm for 30 seconds.
[5-3] The thin film (substrate) produced in [4-3] was annealed at 100 ° C. for 2 minutes on a hot plate in the atmosphere.

Example 4
An organic electroluminescent device was produced in the same manner except that the step [5] of Example 1 was omitted, and the voltage-current density / luminance characteristics and constant current density of the organic electroluminescent device were reduced in the same manner as in Example 1 ( The continuous drive characteristics at 100 cd / m ² were measured. These results are shown in FIGS. 6 (a) and (c-1), respectively. The film thickness of the nitrogen-containing film layer was not measured because it was not annealed, and the thin film was not solidified and could not be measured. Since it is known that the film thickness is reduced by the lower annealing, it is estimated to be about 10 nm.

(Example 5)
An organic electroluminescent device was produced in the same manner except that the step [4] in Example 1 was changed to the above [4-2] and the step [5] was changed to the following [5-5]. In the same manner as in Example 1, the voltage-current density / luminance characteristics, current density-current efficiency characteristics, and continuous drive characteristics under a constant current density (equivalent to 100 cd / m ² ) were measured. These results are shown in FIGS. 7-1 and 7-2 (a), (b) and (c-1), respectively. The average film thickness of the nitrogen-containing film was 8 nm.
[5-5] The thin film (substrate) produced in [4-2] was annealed at 100 ° C. for 10 minutes on a hot plate in the atmosphere.

(Example 6)
An organic electroluminescent device was produced in the same manner except that the step [4] in Example 1 was changed to the above [4-2] and the step [5] was changed to the following [5-6]. In the same manner as in Example 1, the voltage-current density / luminance characteristics, current density-current efficiency characteristics, and continuous drive characteristics under a constant current density (equivalent to 100 cd / m ² ) were measured. These results are shown in FIGS. 8-1 and 8-2 (a), (b) and (c-1), respectively. The average film thickness of the nitrogen-containing film was 7 nm.
[5-6] The thin film (substrate) produced in [4-2] was annealed at 150 ° C. for 10 minutes on a hot plate in the atmosphere.

(Example 7)
An organic electroluminescent element was produced in the same manner except that the step [4] in Example 1 was changed to [4-2] and the step [5] was changed to [5-7] below. In the same manner as in Example 1, the voltage-current density / luminance characteristics, current density-current efficiency characteristics, and continuous driving characteristics under a constant current density (equivalent to 1000 cd / m ² ) were measured. These results are shown in FIGS. 9-1 and 9-2 (a), (b) and (c-2), respectively. The average film thickness of the nitrogen-containing film layer was 5 nm.
[5-7] The thin film (substrate) produced in [4-2] was annealed at 150 ° C. for 30 minutes on a hot plate in the atmosphere.

(Example 8)
An organic electroluminescent device was produced in the same manner except that the step [5] of Example 1 was changed to the following [5-8], and the voltage-current density / voltage of the organic electroluminescent device was obtained in the same manner as in Example 1. The luminance characteristics, current density-current efficiency characteristics, and continuous drive characteristics under a constant current density (equivalent to 1000 cd / m ² ) were measured. These results are shown in FIGS. 10-1 and 10-2 (a), (b) and (c-2), respectively. The average film thickness of the nitrogen-containing film layer was 5 nm.
[5-8] The thin film (substrate) produced in [4] was annealed at 100 ° C. for 30 minutes on a hot plate in the atmosphere.

Example 9
An organic electroluminescent element was produced in the same manner except that the step [4] in Example 1 was changed to [4-2] and the step [5] was changed to [5-9] below. In the same manner as in Example 1, the voltage-current density / luminance characteristics, current density-current efficiency characteristics, and continuous drive characteristics under a constant current density (equivalent to 100 cd / m ² ) were measured. These results are shown in FIGS. 11-1 and 11-2 (a), (b) and (c-1), respectively. The average film thickness of the nitrogen-containing film was 8 nm.
[5-9] The thin film (substrate) produced in [4-2] was annealed at 150 ° C. for 10 minutes on a hot plate under nitrogen.

(Example 10)
An organic electroluminescent device was produced in the same manner except that the step [5] in Example 1 was changed to the following [5-11], and the voltage-current density / voltage of the organic electroluminescent device was obtained in the same manner as in Example 1. The luminance characteristics, current density-current efficiency characteristics, and continuous drive characteristics under a constant current density (equivalent to 1000 cd / m ² ) were measured. These results are shown in FIGS. 12-1 and 12-2 (a), (b) and (c-2), respectively. The average film thickness of the nitrogen-containing film layer was 5 nm.
[5-11] The thin film (substrate) produced in [4] was annealed at 150 ° C. for 5 minutes on a hot plate in the atmosphere. Thereafter, rinsing was performed with ethanol.

(Production Example 1)
The following photoelectron spectroscopy measurement was performed on the nitrogen-containing film obtained by the operations from [1] to [5] in Example 1.
Quantitative analysis was performed by measuring carbon 1S orbital and nitrogen 1S orbital at the same time.
These are shown in FIGS. 13 (d) and (e).

(Measurement of X-ray photoelectron spectroscopy)
Using a JEOL (JPS-9000MX) photoelectron spectrometer, measurement was performed under the following conditions.
X-ray source: MgKα
Beam output (acceleration voltage-current amount): 10 kV-10 mA
PassEnergy: 10eV
Step: 0.1 eV

(Production Example 2)
The above-mentioned photoelectron spectroscopic measurement was performed on the nitrogen-containing film obtained by the operations from [1] to [4] in Example 1.
Quantitative analysis was performed by measuring carbon 1S orbital and nitrogen 1S orbital at the same time.
These are shown in FIGS. 14 (d) and (e).

(Production Example 3)
The above-mentioned photoelectron spectroscopic measurement was performed on the nitrogen-containing film produced by the steps [1] to [3] of Example 1 and the following steps [4-12] and [5-12]. The average film thickness of the nitrogen-containing film layer was 10 nm.
[4-12] Next, Aldrich polyethyleneimine ethoxylate (molecular weight: 70000) diluted to 0.4% by weight with ethoxyethanol was formed at 5000 rpm for 60 seconds to form layer 4 of the nitrogen-containing film. Spin coat.
[5-12] The thin film (substrate) produced in [4-12] was annealed at 100 ° C. for 10 minutes on a hot plate in the atmosphere.
Quantitative analysis was performed by measuring carbon 1S orbital and nitrogen 1S orbital at the same time.
These are shown in FIGS. 15 (d) and 15 (e).

(Production Example 4)
[1] to [3] of Example 1, [4-13] and [5] shown below were sequentially performed, and the above-mentioned photoelectron spectroscopy measurement was performed on the obtained nitrogen-containing film. The film thickness of the nitrogen-containing film layer was such that the average film thickness could not be estimated by multiple measurements. From this, it is guessed that it is less than 3 nm.
[4-13] Next, in order to form the layer 4 of the nitrogen-containing film, polyethyleneimine (registered trademark: epomine) manufactured by Nippon Shokubai Co., Ltd. was diluted to 0.125% by weight with ethanol under the condition of 2000 rpm for 30 seconds. Spin coat. The epomin used here is P1000 having a molecular weight of 70,000.
Quantitative analysis was performed by measuring carbon 1S orbital and nitrogen 1S orbital at the same time.
These are shown in FIGS. 16 (d) and 16 (e).

(Example 11-1)
An organic electroluminescent element was produced in the same manner as in Example 1 except that the steps [4] and [5] in Example 1 were changed to the following [4-18] [5-18]. The voltage-current density / brightness characteristics and current density-current efficiency characteristics of the electroluminescent element were measured. These results are shown in FIGS. 17 (a) and (b), respectively. The average film thickness of the nitrogen-containing film layer was 10 nm.
[4-18] Next, in order to form the layer 4 of the nitrogen-containing film, a linear polyethyleneimine (purchased from Polysciences, molecular weight: 25000) diluted to 0.1% by weight with ethanol was conditioned at 2000 rpm for 30 seconds. Spin coat with.
[5-18] The thin film (substrate) produced in [4-18] was annealed at 150 ° C. for 5 minutes on a hot plate in the atmosphere.

(Example 11-2)
An organic electroluminescent element was produced in the same manner except that step [5-18] in Example 11-1 was omitted. The voltage-current density / luminance characteristics and current density of the organic electroluminescent element were the same as in Example 1. -Current efficiency characteristics were measured. These results are shown in FIGS. 18 (a) and 18 (b), respectively. The average film thickness of the nitrogen-containing film was 12 nm.

Example 12
An organic electroluminescence device was produced in the same manner as in Example 1 except that the steps [4] and [5] in Example 1 were changed to the following [4-20] [5-20]. The voltage-current density / brightness characteristics and current density-current efficiency characteristics of the electroluminescent element were measured. These results are shown in FIGS. 19 (a) and 19 (b), respectively. The average film thickness of the nitrogen-containing film layer was 10 nm.
[4-20] Next, in order to apply a melamine resin as a nitrogen-containing compound for forming the layer 4 of the nitrogen-containing film, melamine and formaldehyde are mixed 1: 3, and a mixed solvent of methanol: water = 1: 1 The material dissolved in 0.1 wt% is spin-coated under the condition of 2000 rpm for 30 seconds.
[5-20] The thin film (substrate) produced in [4-20] was annealed at 80 ° C. for 60 minutes on a hot plate in the atmosphere.

(Comparative Example 2)
An organic electroluminescent device was produced in the same manner as in Example 1 except that the steps [4] and [5] in Example 1 were changed to the following [4-21] [5-21]. The voltage-current density / brightness characteristics and current density-current efficiency characteristics of the electroluminescent element were measured. These results are shown in FIGS. 20 (a) and (b), respectively.
[4-21] Next, instead of the layer 4 of the nitrogen-containing film, a polystyrene film (10 nm) was formed by spin coating using toluene as an organic film not containing nitrogen.
[5-21] The thin film (substrate) produced in [4-21] was annealed at 150 ° C. for 5 minutes on a hot plate in the atmosphere.

2 to 12 and FIGS. 17 to 20, (a) to (c) show the following contents, respectively.
(A) Voltage-current density (black circle) / luminance (white circle) characteristics. First, high brightness is good. Second, it is better to be able to express high luminance at a lower voltage.
(B) Current density-current efficiency (black rhombus) characteristics. First, it is good that the current efficiency (hereinafter referred to as “efficiency”) is high. Second, it is good that it is constant. In particular, it is good to be high and constant in a high current density region (high luminance region).
(C) shows a change with time of voltage and a change with time of relative luminance under a constant current (here, a current value with an initial luminance of 1000 cd / m ² ). First, it is better to use a material that has a small change in relative luminance with time (it can maintain the initial luminance for a long time) (hereinafter referred to as “long life”). The content related to this, but secondly, it is better that the voltage rise between them is small.
All three elements of brightness, efficiency, and lifetime are important, but among them, lifetime is the first priority in practical use.

Based on the above assumption, the results of FIGS.
FIG. 2: Light is emitted from a low voltage (around 2V), and reaches a high luminance of 3000 cd / m ^{2 at} 6V. The efficiency is generally high and is 4 cd / A or more. In addition, regarding long-term changes, high reliability of about 200 hours was realized until the luminance was reduced to half. Under different driving conditions with an initial luminance of 100 cd / m ² , it was estimated to have a half-life of several thousand hours, and thus it was revealed that reproducibility was also high.
FIG. 3: FIG. 3 shows the measurement results of an element having no layer between the metal oxide layer and the light emitting layer. It can be seen that both the luminance and the efficiency are 1/10 or less of FIG. In the measurement results shown in FIG. 4 and the subsequent figures, the values shown in FIG.
FIG. 4: Although the efficiency is superior to that of FIG. 2 (the device of Example 1), the brightness declines rapidly in the initial few hours, and FIG. 2 is superior in terms of life. From this result, it is presumed that the device of Example 1 is superior in terms of stability under oxidation-reduction as a film.
FIG. 5: Both luminance and efficiency are comparable to FIG. 2 (element of Example 1). Also in the lifetime, the transition up to about initial 10 hours is equivalent to FIG. However, after that, rapid deterioration occurs.
From the results of FIGS. 4 and 5, even when polyethyleneimines having different molecular weights are used, there is no significant difference in the initial characteristics, and both are superior to those having no nitrogen-containing film. However, there is a difference in long-term stability.

In FIGS. 6 to 12 (Examples 4 to 10), the influence (process dependence) of the process (annealing conditions (temperature, time, atmosphere) and rinsing) after applying a nitrogen-containing compound to form a film is affected. )It was confirmed. In addition, they showed molecular weight dependence on them.
FIG. 6: Measurement results of device characteristics when liquid branched polyethyleneimine (low molecular weight) is used without annealing. There is almost no light emission, and it is not at a level that can be called a characteristic.
FIG. 7 and FIG. 8 are the results of measuring the characteristics of the element obtained by changing the annealing temperature using a liquid branched polyethyleneimine (high molecular weight). The higher the temperature, the better the brightness and efficiency. The influence of the annealing temperature is somewhat remarkable in the lifetime, and a better result is obtained when annealing at a high temperature more than twice the half-life. The difference seems to be due to the fact that the initial brightness drop is smaller when annealing at a high temperature. This, including FIG. 6, suggests that annealing is effective in extending the life, that is, the long-term stability of redox. Although not shown here, when the annealing was performed at 200 ° C., the element was not measured because it turned brown. From this, it can be inferred that there is an optimum value for the annealing temperature.
FIG. 9: Example 7 shows the result of producing a nitrogen-containing film by changing the annealing time at 150 ° C., which is the best annealing temperature obtained from the results of Examples 4 to 6 (FIGS. 6 to 8). It is. Both luminance and efficiency are slightly lower than in FIG. 8 (Example 6). It can also be seen that the initial deterioration is beginning to appear slightly stronger with respect to the life curve. From these facts, it is presumed that there is an optimum value for the annealing time.

FIG. 11: Finally, the results of investigations under the above-mentioned best conditions for the atmosphere in which annealing is performed. When the production of the nitrogen-containing film under the conditions shown in FIG. 8 (Example 6) is performed under nitrogen, the initial characteristics (luminance / efficiency) are not significantly different from those in FIG. From this, it can be inferred that the effect of having a nitrogen-containing film here is an electron-attracting effect due to metal-nitrogen polarization and physical-carbon-nitrogen polarization in physisorption rather than chemical adsorption. The It should be noted that the lifetime is extremely short in FIG. From this, it is considered that the annealing process in the present invention that causes a long life is likely to be accompanied by not only solvent removal and morphological changes, but also chemical changes. (What kind of chemical change will be described later)
FIG. 10: From the result of the above consideration, it is presumed that the annealing condition depends on the molecular weight as well as the material.
As a result of annealing the liquid branched polyethyleneimine (low molecular weight) for a long time at a temperature lower than the best temperature, the results were similar to those in FIG. It was observed that the current density value was high in voltage and in reverse bias. This means that there is a wasteful current flow (hereinafter referred to as “leakage current”) that does not contribute to light emission, and in many cases, there is a problem with long-term stability. This time as well, the lifetime is short, such as a sharp drop in brightness from the beginning, which is considered to be due to the leakage current.
From this result, it was clarified that the best value of the annealing condition depends not only on the material but also on the molecular weight. In addition, it is suggested that there is a temperature threshold depending on the material and molecular weight because good characteristics cannot be obtained even if annealing is performed for a long time below the optimum temperature.
FIG. 12: When the rinsing effect under the above best conditions (conditions of Example 1) is confirmed, the initial characteristics (luminance / efficiency) are almost the same as those of FIG. 2 (Example 1), but the leakage current is slightly large. . This is considered to be a factor that makes the life characteristics worse than in FIG. 2 (Example 1). However, although it does not appear in this figure, the variation in the characteristics between the manufacturing elements is reduced, and the reproducibility is improved. This is considered an important process from the viewpoint of practical application. In terms of life, it can be improved by finding better rinsing conditions.

FIG. 17 and FIG. 18 are results of using linear polyethyleneimine as the nitrogen-containing compound. Regardless of the presence or absence of annealing treatment, all show good initial characteristics (brightness and efficiency). Unlike branched polyethyleneimine, this is considered to be due to the fact that it is solid. That is, the effect of annealing is assumed to be the following three points. (I) Solidify. (Ii) Prepare strong bond species by diversifying metal-nitrogen bonds. (Iii) The carbon element: nitrogen element ratio is changed to relatively improve the nitrogen element abundance ratio.
The effects of these annealing will be further described later.

FIG. 19 shows the result of studying application of melamine resin as a material having a high nitrogen ratio. Compared to FIG. 3, good results were obtained and it was confirmed that there was an effect. Since there is unevenness in light emission, it is considered that better results can be obtained if detailed detailed conditions can be found.
FIG. 20 shows the result of applying an organic film that does not contain nitrogen. It can be seen that the luminance and efficiency are inferior to those of FIG. 3 in the initial characteristics. From this, it is considered that this organic film functions as a simple insulating layer. In addition, the lifetime of this element is extremely short, such as several minutes, and it is expected that the electron injection mechanism is due to band bending of the light emitting layer due to charge accumulation in the light emitting layer. From the detailed examination of the conditions, it seems that the initial characteristics can be improved also in polystyrene, but since the driving mechanism is as described above, it is considered that long-term reliability cannot be expected as in the element of the present invention.

Next, FIGS. 13 to 16 (Production Examples 1 to 4) will be described.
In Production Examples 1 to 4, before annealing of the nitrogen-containing film, measurement was impossible in all cases of liquid branched polyethyleneimine. On the other hand, measurement became possible by annealing. From this, it was suggested that the annealing solidified due to some effect (the result cannot be concluded as a decomposition from this result alone) (the above effect (i)).
The results (d) of the carbon 1s orbital X-ray photoelectron spectroscopy measurement and the nitrogen 1s orbital X-ray photoelectron spectroscopy measurement results (e) in FIGS. 13 to 16 are all the measurement results after annealing. Prior to annealing, it was confirmed that all C: N≈2: 1 except for FIG. FIG. 15 shows C: N≈4: 1 before annealing. These ratios correspond to the stoichiometric ratio estimated from the chemical structure. This element abundance ratio is estimated from the ratio of the peak area of each orbit. In comparison between FIG. 13 and FIG. 14, it was confirmed that there was a change in the ratio depending on the presence or absence of annealing and a change in ratio. By annealing, the peak areas of both carbon and nitrogen are reduced, but the phenomenon of the carbon peak is larger, leading to a relatively improved nitrogen element ratio. In FIG. 15, it can be seen that there is no significant chemical change since there is no change after annealing (with the stoichiometric ratio). This is because the thin film formed from polyethyleneimine or a compound modified with polyethyleneimine described in Non-Patent Documents 1 to 3 described above is a branched polyethylenimine (low molecular weight) that is liquid in the present invention. It was suggested that the effect of the thin film changed by annealing is not equivalent. FIG. 16 shows the result of the same annealing treatment by thinning the liquid branched polyethyleneimine (high molecular weight) to a thickness equal to or higher than that of the low molecular weight. Also in this result, the high molecular weight polyethyleneimine does not change the element abundance ratio. From this, it was suggested that the abundance ratio of carbon element: nitrogen element does not occur unless under certain conditions, for example, low molecular weight (the above effect (iii)).
(F) of FIGS. 13-15 is the figure which showed the result of having peak-divided about the result of the X-ray photoelectron spectroscopy measurement of the nitrogen 1s orbit. In this system, two types of nitrogen atom bonds are assumed, a carbon-nitrogen bond and a metal-nitrogen bond. From the past literature, it is attributed that the peak on the lowest energy side is a metal-nitrogen bond. Furthermore, when the second peak is assigned to the carbon-nitrogen bond, the energy difference between all the two peaks is almost equal to 0.6 eV to 0.7 eV, and these peak splits and assignments are correct. Things are suggested.
Although not shown here, the full width at half maximum is 1.2 eV in all the examples of FIGS. 13 to 15 before annealing. From this, in the case of FIG. 13 and FIG. 15, the full width at half maximum is increased, which is considered to lead to a longer life (the above effect (ii)).
From the above, in the case of FIG. 13, all the effects (i) to (iii) are exhibited, and it is considered that initial characteristics (luminance / efficiency) and long-term reliability (lifetime) can be realized. In FIG. 15, it is assumed that (i) and (ii) can realize the initial characteristics and a certain lifetime, and similarly, in FIG. 14, the effects (i) can realize the initial characteristics and a certain lifetime. . Although there is no result of the X-ray photoelectron spectroscopy measurement, the solid linear polyethyleneimine used in FIGS. 17 and 18 has no effect of annealing because (i) is realized. It is thought that a certain lifetime can be realized. The same applies to FIG.

From the above results, the following became clear.
From a comparison between FIG. 3 and other figures, it was confirmed that when the nitrogen-containing thin film was disposed on the oxide on the lower cathode, the characteristics of the organic electroluminescent device such as luminance and efficiency were improved. With respect to the annealing treatment, it was confirmed from FIG. 18 that annealing may not be necessary depending on the material, and is not necessarily required. However, it was confirmed that the life characteristics corresponding to long-term reliability were improved in many cases by annealing. As for the materials used, it was confirmed that various nitrogen-containing compounds such as polyethyleneimine (with different molecular weights or different shapes <linear and branched>), diethylenetriamine, and melamine resin can be used. It was also confirmed that it was necessary to select the process depending on the molecular weight and shape as well as the material. In particular, since linear polyethyleneimine is solid unlike other polyethyleneimines, it is considered that the effect is exhibited even without annealing. It was also confirmed that rinsing after film formation was effective.

1: Substrate 2: Cathode 3: First metal oxide layer 4: Nitrogen-containing film layer 5: Organic compound layer 6: Second metal oxide layer 7: Anode

Claims (3)

An organic electroluminescent device having a structure in which a plurality of layers are laminated between an anode and a cathode formed in contact with a substrate,
The organic electroluminescent element comprises a metal oxide layer between an anode and a cathode, an organic compound layer including a light emitting layer , a nitrogen-containing film in contact with the metal oxide layer, and an average thickness of 3 and a layer of ～150Nm, cathode, metal oxide layer, a layer made of a nitrogen-containing layer, the organic compound layer including a light-emitting layer stacked in this order,
Nitrogen-containing layer is either formed with a nitrogen-containing compound, or, and a nitrogen element and a carbon element as an element constituting the membrane, the presence ratio of nitrogen atoms to carbon atoms constituting the nitrogen-containing film nitrogen Number of atoms / (number of nitrogen atoms + number of carbon atoms)> 1/8
An organic electroluminescent element characterized by satisfying the relationship: The organic electroluminescent device according to claim 1, wherein the nitrogen-containing film includes a decomposition product of a nitrogen-containing compound. The organic electroluminescent element according to claim 1, wherein the nitrogen-containing compound is a polyamine or a triazine ring-containing compound.

Images