JP6496183B2 - ORGANIC ELECTROLUMINESCENT ELEMENT, DISPLAY DEVICE, LIGHTING DEVICE, AND METHOD FOR PRODUCING ORGANIC ELECTROLUMINESCENT ELEMENT - Google Patents

Description

  The present invention relates to an organic electroluminescent element, a display device, an illuminating device, and a method for manufacturing the organic electroluminescent element.

  The organic electroluminescent element has a structure in which a plurality of layers such as an electron transport layer, a light emitting layer, and a hole transport layer are laminated between a cathode and an anode, and is a material suitable for constituting each layer. Research and development are being conducted.

  Of these, materials that are easily deteriorated due to the influence of moisture and oxygen in the atmosphere, such as alkali metals such as LiF and aluminum, have been used for the cathode. Therefore, when applying an organic electroluminescent element to a display or the like, strict sealing is required, and it is difficult to reduce costs and make flexible. In contrast, in recent years, by depositing a metal oxide that is stable in the atmosphere and has a low work function on the surface of the lower electrode, electron injection into the organic layer is promoted, and an electroluminescent element that can operate stably in the atmosphere ( It has been reported that an organic-inorganic hybrid organic EL element (Hybrid Organic Inorganic LED: HOILED) can be realized.

Features of this hybrid organic EL device include <1> high atmospheric stability and <2> the lower electrode serving as the contact portion with the transistor used as a cathode in consideration of application to a display ( In a normal organic EL element, the lower electrode serves as an anode (see Non-Patent Documents 1 and 2 below).
As a metal oxide constituting such an electron injecting oxide semiconductor layer, one having a high conduction band energy level is preferable. Titanium oxide (TiO ₂ ), zinc oxide (ZnO), tungsten oxide (WO ₃ ). Niobium oxide (Nb ₂ O ₅ ), iron oxide (Fe ₂ O ₃ ), tin oxide (SnO ₂ ) and the like have already been reported (see Patent Documents 1 and 2 below), and among them, oxidation A material such as zinc (ZnO) has attracted particular attention.

JP 2012-4492 A JP 2007-53286 A

APPLIED PHYSICS LETTERS Volume 89, page 183510 (2006) Advanced Materials Volume 23, page 1829 (2011)

  However, there is currently a demand for metal oxide materials having various excellent characteristics other than the materials described above, and in particular, has an electron injection property equal to or higher than that of the above-described zinc oxide (ZnO), and is, for example, a thin film There is a strong demand for a new metal oxide material that can achieve effects such as crystallization.

  The present invention has been made in view of the above circumstances, and can provide an organic electroluminescent element, a display device, a lighting device, and an organic device that can significantly improve the electron mobility of the electron injection layer and can also exhibit other useful effects. An object of the present invention is to provide a method for manufacturing an electroluminescent element.

The organic electroluminescent device according to the present invention is
An organic electroluminescence device in which a plurality of layers are laminated between a first electrode film that is a cathode and a second electrode film that is an anode, wherein the plurality of layers includes the first electrode film. In order from the side, comprising at least a plurality of layers including an electron injection layer having an electron injection function and a light emitting layer,
The electron injection layer is a layer containing InSnZnO.
In the following description, the “electron injection layer” may be referred to as a first metal oxide layer, and the “light-emitting layer” is often laminated sequentially with other low-molecular compound layers. The term “low molecular compound layer including a light emitting layer” may be used instead of the term “light emitting layer”.

  Preferably, the plurality of layers are at least an electron injection layer having an electron injection function, a light emitting layer, and a hole injection layer having a hole injection function in order from the first electrode film side.

  More specifically, the plurality of layers, in order from the first electrode film side, have at least an electron injection layer having an electron injection function, a buffer layer, a light emitting layer, a hole transport layer, and a hole injection function. It is preferable that the hole injection layer which has is laminated | stacked.

The display device of the present invention is formed using any one of the above organic electroluminescent elements.
In addition, the lighting device of the present invention is characterized by being formed using any one of the above organic electroluminescent elements.

  According to the method for manufacturing an organic electroluminescent element of the present invention, a first electrode film as a cathode and a second electrode film as an anode are arranged on a substrate in this order or reverse order from the substrate side. At the same time, the two electrode films are stacked so that a plurality of layers including at least an electron injection layer made of InSnZnO having an electron injection function and a light emitting layer are disposed in this order from the first electrode film side. It is characterized by doing.

  According to the organic electroluminescent element, the display device, the illuminating device, and the manufacturing method of the organic electroluminescent element of the present invention, the first electrode film as the cathode and the second electrode film as the anode are disposed between the first electrode film and the second electrode film. A plurality of layers including at least an electron injection layer having an electron injection function and a light emitting layer are stacked in this order from the electrode film side, and the electron injection layer is a layer containing InSnZnO.

  Although InSnZnO is a metal oxide, it has a good electron injection performance equal to or better than that of zinc oxide and the like. Therefore, a layer containing a metal oxide that is originally not suitable as an electron injection layer because of its low electron mobility is extremely good. It can be easily formed as a simple electron injection layer.

This makes it possible to easily realize high-luminance and high-contrast image display and light emission illumination.
Further, since InSnZnO generally has an amorphous structure, useful effects such as thinning can be easily achieved, and it is possible to meet the demand for thinning the entire device.

It is a schematic diagram which shows the layer structure of the organic electroluminescent element which concerns on this embodiment. It is a graph which shows the drive voltage-luminance characteristic of each organic electroluminescent element which concerns on an Example and a comparative example. It is a graph which shows the EL emission spectrum (intensity) of the organic electroluminescent element which concerns on an Example and a comparative example.

Hereinafter, an organic electroluminescent element and a manufacturing method thereof according to an embodiment of the present invention will be described in detail with reference to the drawings and examples.
In addition, what combined two or more each form of this invention described below is also embodiment of this invention. In the present embodiment, “parts” means “parts by weight” and “%” means “mass%” unless otherwise specified, regardless of the description.

  In the organic electroluminescent element of the present embodiment, a first electrode film that is a cathode and a second electrode film that is an anode are disposed and formed from the substrate side, and a plurality of layers are provided between these two electrode films. And a plurality of layers, at least a first metal oxide layer functioning as an electron injection layer in order from the first electrode film side, and a light emitting layer A low molecular compound layer containing The first metal oxide layer is configured as a layer containing InSnZnO (hereinafter referred to as ITZO).

The plurality of layers function as a low-molecular compound layer and a hole injection layer including at least a first metal oxide layer functioning as an electron injection layer, and a light emitting layer in order from the first electrode film side. Preferably, the second metal oxide layer is laminated.
The organic electroluminescence device of this embodiment is a device having a reverse laminated structure in which a first metal oxide layer for electron injection is formed adjacently on a pixel electrode, and the pixel electrode Between the (cathode) and the anode, the first metal oxide layer and the light emitting layer, and between the first metal oxide layer and the light emitting layer, if necessary, an electron transport layer, An element having a hole transport layer and / or a hole injection layer between the light emitting layer and the anode is preferable.

  The organic electroluminescent element of the present invention may have other layers between these layers, but may be an element composed only of these layers. Further, it is possible to insert a buffer layer between layers as appropriate. That is, the cathode, the electron injection layer, the electron transport layer (or buffer layer), if necessary, the light emitting layer, the hole transport layer and / or the hole injection layer, and the anode layer are stacked in this order. Is preferred. Each of these layers may be composed of one layer, or may be composed of two or more layers.

  In the organic electric field element having the above configuration, when the element does not have an electron transport layer (or buffer 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 embodiment, the material forming each layer may be a low molecular compound or a high molecular compound, or a mixture thereof may be used.
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.

Furthermore, in the organic electroluminescent element of this embodiment, the average thickness of the organic layer forming each layer is not particularly limited, but is preferably 1 to 150 nm. More preferably, it is 20-100 nm.
The average thickness of each layer can be measured using a stylus type step gauge or spectroscopic ellipsometry. When the light emitting layer is formed by a vacuum deposition method, it is manufactured using a quartz oscillator thickness meter. It can be measured at the time of filming.

  Hereinafter, each structure of the said embodiment is demonstrated sequentially.

  In the organic electroluminescence device of this embodiment, when a low molecular compound layer including a buffer layer and a light emitting layer is laminated on the electron injection layer, crystallization of the low molecular compound layer in contact with the electron injection layer occurs. As a result, the leakage current increases and the current efficiency is lowered. In the case where the leakage current is remarkable, there is a possibility that a problem that uniform surface light emission cannot be obtained by crystallization may occur. In the organic-inorganic hybrid type organic electroluminescence device, the cause of the crystallization of the low molecular compound layer is considered as follows.

  In an organic-inorganic hybrid organic electroluminescent device, a first electrode film disposed on a substrate such as glass and a first metal oxide layer are present, and a low molecular compound layer including a light emitting layer is formed thereon. A film will be formed. Here, according to the conventional method, the first metal oxide layer is formed by a spray pyrolysis method, a sol-gel method, a sputtering method, or the like, and the surface is not smooth but has irregularities. When a low molecular compound layer including a light emitting layer is formed on the first metal oxide layer by a method such as vacuum deposition, the surface irregularities of the first metal oxide layer become crystal nuclei, and the first Crystallization of the low molecular compound layer in contact with the metal oxide 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 cannot be obtained.

  On the other hand, in the so-called normal structure organic electroluminescence device that does not have the first metal oxide layer on the first electrode film, the surface of the first electrode film that is sufficiently smooth is available. Even if a low molecular compound layer including a light emitting layer is directly formed on the surface of the first electrode film, the problem of crystallization hardly occurs. Therefore, such crystallization is a problem peculiar to the organic-inorganic hybrid organic electroluminescence device, and is a problem newly generated when a low molecular compound is used as a host of the light emitting layer.

  For this problem, the average thickness formed by applying a solution containing an organic compound between the electron injection layer (ITZO film), which is the first metal oxide layer, and the low molecular weight compound layer including the light emitting layer. When a buffer layer having a thickness of 5 to 100 nm is provided, crystallization of the low molecular compound in the low molecular compound layer is suppressed, whereby an organic-inorganic hybrid organic electroluminescent device is formed from the low molecular compound as a light emitting layer or the like. Even in the case of having a layer, the leakage current can be suppressed and uniform surface light emission can be obtained.

  The organic electroluminescent element of this embodiment includes a low molecular compound layer including a light emitting layer laminated on a buffer layer, and the low molecular compound layer including a light emitting layer is one layer formed of a low molecular compound. Alternatively, a plurality of layers formed of low molecular compounds are stacked, and one of the layers is a light emitting layer. That is, a low molecular compound layer including a light emitting layer is a light emitting layer formed of a low molecular compound, or a light emitting layer formed of a low molecular compound and another layer formed of a low molecular compound. One of things. The other layer formed of the low molecular compound may be one layer or two or more layers. The order in which the light emitting layer and other layers are stacked is not particularly limited.

  The other layer formed of the low molecular compound is preferably a hole transport layer or an electron transport layer. That is, when the low molecular compound layer is composed of a plurality of layers, it is preferable to have a hole transport layer and / or an electron transport layer as other layers other than the light emitting layer. As described above, the organic electroluminescent device having the hole transport layer and / or the electron transport layer as an independent layer different from the light emitting layer is one of the preferred embodiments of the organic electroluminescent device of the present embodiment. It is.

  When the organic electroluminescent element of this embodiment has a hole transport layer as an independent layer, it is preferable to have a hole transport layer between the light emitting layer and the second metal oxide layer. When the organic electroluminescent element of this embodiment has an electron transport layer as an independent layer and also has the above-described buffer layer, it has an electron transport layer between the buffer layer formed from the organic compound and the light emitting layer. Is preferred.

  When the organic electroluminescent element of this embodiment does not have a hole transport layer or an electron transport layer as an independent layer, any of the layers that are included as an essential component of the organic electroluminescent element of this embodiment It also serves as a function.

  One preferred form of the organic electroluminescent element of the present embodiment is, for example, as shown in FIG. 1, on a transparent substrate 1, a first electrode film (cathode) 2 made of an ITO film and an ITZO film. Electron injection layer (first metal oxide layer) 3, buffer layer 4, electron transport layer 4 a, light emitting layer 5, hole transport layer 6, hole injection layer (second metal oxide layer) ) 7 and a second electrode film (anode) 8 are laminated in this order.

  In addition, each independent layer of the organic electroluminescent element includes, for example, a first electrode film (cathode) 2, an electron injection layer (first metal oxide layer) 3 made of an ITZO film 4a, a buffer layer 4, This embodiment also includes a light emitting layer 5, a hole injection layer 7, and a second electrode film (anode) 8, and any one of these layers serves as a hole transport layer and an electron transport layer. It is one of the preferable forms of the organic electroluminescent element of a form.

In the organic electroluminescence device of this embodiment, the material constituting the first electrode film is ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), In ₃ O ₃ , SnO _2. And oxides such as Sb-containing SnO ₂ and Al-containing ZnO. Among these, ITO, IZO, and FTO are preferable.
Examples of the material constituting the second electrode film include Au, Pt, Ag, Cu, Al, and alloys containing these. Among these, Au, Ag, and Al are preferable.

  The average thickness of the first electrode film is not particularly limited, but is preferably 10 to 500 nm, for example. More preferably, it is 100-200 nm.

The average thickness of the second electrode film is not particularly limited, but is preferably 10 to 1000 nm, for example. More preferably, it is 30-150 nm. Even when an opaque material is used for the irradiation light, it can be used as a top emission type or transparent type anode by setting the average thickness to about 10 to 30 nm, for example.
The average thickness of the second electrode film can be measured at the time of film formation by a crystal oscillator thickness meter.

The first metal oxide layer functions as an electron injection layer, and the second metal oxide layer functions as a hole injection layer.
The main point of this embodiment is that ITZO (indium tin zinc oxide (InSnZnO)) is used as the first metal oxide layer. That is, in an organic electroluminescent element provided with an electrode made of ITO (cathode, first electrode film), electron injection from ITO does not occur so much, and a high driving voltage is required for high luminance. In contrast, an electron injection layer containing ITZO (including an electron injection layer made of ITZO; hereinafter the same) is formed on the surface of the electrode (cathode, first electrode film) as in the organic electroluminescence device of this embodiment. In the case of filming, high luminance can be obtained with a low driving voltage. This is because the work function of ITO is about 5 eV, which is inappropriate for electron injection, whereas the energy level of the conduction band of ITZO is about 4 eV. In comparison, ITZO's electronic injection is higher than equivalent.
Further, ITZO has high crystallinity and has a higher electron mobility than zinc oxide or the like, and thus is considered more suitable as an electron injection layer.

  Further, for example, IGZO, which has been conventionally used for an electron injection layer, does not necessarily have a high resistance to acids and alkalis, and may be damaged by a photolithography developer or the like. On the other hand, it is considered that the resistance to acids and alkalis can be improved by configuring the electron injection layer with ITZO.

The hole injection layer is not particularly limited to an organic substance / oxide, but in the case of an organic substance, for example, F4TCNQ or HAT-CN can be used. In the case of an oxide, one or more of vanadium oxide (V ₂ O ₅ ), molybdenum trioxide (molybdenum oxide: MoO ₃ ), ruthenium oxide (RuO ₂ ), and the like 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 of the organic material, vanadium oxide, or molybdenum oxide as a main component, the second metal oxide layer injects holes from the second electrode film. It becomes more excellent by the function as a hole injection layer of transporting to a light emitting layer or a hole transport layer. In addition, vanadium oxide or molybdenum oxide has a high hole transport property by itself, and therefore suitably prevents the efficiency of hole injection from the second electrode film to the light emitting layer or the hole transport layer from being lowered. There is an advantage that you can also.

  The average thickness of the first metal oxide layer (ITZO) is not particularly limited, but is preferably 1 to 1000 nm. 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.

  Note that the average thickness of the first metal oxide layer can be measured by a stylus profilometer or spectroscopic ellipsometry.

  In addition, the average thickness of the second metal oxide layer can be measured at the time of film formation with a crystal oscillator thickness meter.

  As a material for the light emitting layer, any low molecular weight compound that can be usually used as a material for the light emitting layer can be used, or a mixture thereof may be used.

As a low molecular weight type, a tricoordinate iridium complex having 2,2′-bipyridine-4,4′-dicarboxylic acid as a ligand, 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)), 2,3,7,8,12 , 13, 17, 18-octaethyl-21H, 23H-porphine Various metal complexes such as platinum (II); distyrylbenzene (DSB), diamino Benzyl compounds such as styrylbenzene (DADSB), naphthalene compounds such as naphthalene and nile red, phenanthrene compounds such as phenanthrene, chrysene, chrysene compounds such as 6-nitrochrysene, perylene, N, N ′ -Perylene compounds such as bis (2,5-di-t-butylphenyl) -3,4,9,10-perylene-di-carboximide (BPPC), coronene compounds such as coronene, anthracene, bis Anthracene compounds such as styrylanthracene, pyrene compounds such as pyrene, pyrans such as 4- (di-cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM) Compounds, acridine compounds such as acridine, and stilbenes Like tilbene compounds, carbazole compounds such as 4,4′-bis [9-dicarbazolyl] -2,2′-biphenyl (CBP), thiophene compounds such as 2,5-dibenzoxazole thiophene, and benzoxazole Benzoxazole compounds, benzimidazole compounds such as benzimidazole, benzothiazole compounds such as 2,2 ′-(para-phenylenedivinylene) -bisbenzothiazole, bistyryl (1,4-diphenyl-1, 3-butadiene), butadiene compounds such as tetraphenylbutadiene, naphthalimide compounds such as naphthalimide, coumarin compounds such as coumarin, perinone compounds such as perinone, oxadiazoles such as oxadiazole Compounds, aldazines Compound, cyclopentadiene compound such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP), quinacridone compound such as quinacridone and quinacridone red, pyrrolopyridine, thiadiazolo Pyridine compounds such as pyridine, spiro compounds such as 2,2 ′, 7,7′-tetraphenyl-9,9′-spirobifluorene, metals such as phthalocyanine (H ₂ Pc), copper phthalocyanine or Examples thereof include metal phthalocyanine compounds, and boron compound materials described in JP-A-2009-155325 and Japanese Patent Application No. 2010-28273, and one or more of these can be used.

The light emitting layer may contain a dopant. As the dopant, any compound that can be usually used as a dopant can be used. Examples of compounds that can be used as the dopant include iridium tris (1-phenylisoquinoline) (Ir (piq) ₃ ), iridium tris (2-phenylpyridine) (Ir (ppy) ₃ ), iridium tris [2- ( Iridium compounds such as (tolyl) pyridine] (Ir (mppy) ₃ ), iridium bis (2-methyldibenzo- [f, h] quinoxaline) (acetylacetonate) (Ir (MDQ) ₂ (acac)); Examples include low-molecular organic compounds such as' -bis (9-ethyl-3-carbazovinylene) -1,1'-biphenyl (BCzVBi), and one or more of these can be used.

  When the said light emitting layer contains a dopant, it is preferable that content of a dopant is 0.5-20 mass% with respect to 100 mass% of materials which form a light emitting layer. With such a content, the light emission characteristics can be improved. More preferably, it is 0.5-10 mass%, More preferably, it is 1-6 mass%.

  The light emitting layer of the organic electroluminescent element of the present embodiment preferably includes a phosphorescent material among the above. When the light emitting layer contains a phosphorescent light emitting material, the organic electroluminescent element becomes more excellent in luminous efficiency.

  In the case where the light-emitting layer includes a phosphorescent light-emitting material, the light-emitting layer is preferably formed using a material in which the host material includes a phosphorescent light-emitting material as a guest material (dopant). It is preferable that content of the phosphorescence-emitting material in the said light emitting layer is 0.5-20 mass% with respect to 100 mass% of materials which form a light emitting layer. With such a content, the light emission characteristics can be improved. More preferably, it is 0.5-10 mass%, More preferably, it is 1-6 mass%.

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.
The average thickness of the light emitting layer can be measured at the time of film formation with a quartz oscillator film thickness meter.

  As the material for the hole transport layer, any low molecular weight compound that can be usually used as the material for the hole transport layer can be used, or a mixture of these may be used.

Examples of the low molecular weight compound include 1,1-bis (4-di-para-triaminophenyl) cyclohexane and 1,1′-bis (4-di-para-tolylaminophenyl) -4-phenyl-cyclohexane. Such arylcycloalkane compounds, 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-na Til) -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) -meta-phenylenediamine ( Phenylenediamine compounds such as PDA), carbazole compounds such as carbazole, N-isopropylcarbazole, N-phenylcarbazole, stilbenes, stilbene compounds such as 4-di-para-tolylaminostilbene, and OxZ Oxazole compounds, triphenylmethane, triphenylmethane compounds such as m-MTDATA, 1-phenyl-3- (para Pyrazoline compounds such as dimethylaminophenyl) pyrazoline, benzine (cyclohexadiene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, 1,3,4-oxadiazole, 2,5- Oxadiazole compounds such as di (4-dimethylaminophenyl) -1,3,4, -oxadiazole, anthracene, anthracene compounds such as 9- (4-diethylaminostyryl) anthracene, fluorenone, 2, Fluorenone compounds such as 4,7, -trinitro-9-fluorenone, 2,7-bis (2-hydroxy-3- (2-chlorophenylcarbamoyl) -1-naphthylazo) fluorenone, aniline compounds such as polyaniline, Silane compounds, 1,4-dithio Pyrrole compounds such as oketo-3,6-diphenyl-pyrrolo- (3,4-c) pyrrolopyrrole, fluorene compounds such as fluorene, porphyrins, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone Quinacridone compounds, metal such as phthalocyanine, copper phthalocyanine, tetra (t-butyl) copper phthalocyanine, iron phthalocyanine or metal-free phthalocyanine compounds, metal such as copper naphthalocyanine, vanadyl naphthalocyanine, monochlorogallium naphthalocyanine or Metal-free naphthalocyanine compounds, benzidine compounds such as N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine, N, N, N ′, N′-tetraphenylbenzidine Etc. These 1 type (s) or 2 or more types can be used.
Among these, arylamine compounds such as α-NPD and TPTE are preferable.

When the organic electroluminescent element of this embodiment has a hole transport layer as an independent layer, the average thickness of the hole transport layer is not particularly limited, but is preferably 10 to 150 nm. More preferably, it is 40-100 nm.
The average thickness of the hole transport layer can be measured at the time of film formation using a quartz oscillator thickness meter.

  As the material for the electron transport layer, any low molecular weight compound that can be usually used as the material for the electron transport layer can be used, or a mixture of these may be used.

Examples of low molecular weight compounds that can be used as the material for the electron transport layer include tris-1,3,5- (3 ′-(pyridine) in addition to a boron-containing compound represented by the following chemical formula 1 (Chemical Formula 1). Pyridine derivatives such as -3 ″ -yl) phenyl) benzene (TmPyPhB), quinoline derivatives such as (2- (3- (9-carbazolyl) phenyl) quinoline (mCQ)), 2-phenyl-4,6 -Pyrimidine derivatives such as bis (3,5-dipyridylphenyl) pyrimidine (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), 2,4-bis (4-biphenyl) -6- (4 ' Triazine derivatives such as-(2-pyridinyl) -4-biphenyl)-[1,3,5] triazine (MPT), 3-phenyl-4- Triazole derivatives such as (1′-naphthyl) -5-phenyl-1,2,4-triazole (TAZ), oxazole derivatives, 2- (4-biphenylyl) -5- (4-tert-butylphenyl-1, Oxadiazole derivatives such as 3,4-oxadiazole) (PBD), 2,2 ′, 2 ″-(1,3,5-bentriyl) -tris (1-phenyl-1-H-benzimidazole) ) Imidazole derivatives such as (TPBI), aromatic ring tetracarboxylic anhydrides such as naphthalene and perylene, bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (Zn (BTZ) ₂ ), tris (8-hydroxyquino) Various metal complexes represented by linato) aluminum (Alq3), 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl Examples include organosilane derivatives represented by silole derivatives such as 3,4-diphenylsilole (PyPySPyPy), 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 this embodiment has an electron transport layer as an independent layer, the average thickness of the electron transport layer is not particularly limited, but is preferably 10 to 150 nm. More preferably, it is 40-100 nm.
The average thickness of the electron transport layer can be measured at the time of film formation with a crystal oscillator thickness meter.

  In the organic electroluminescence device of the present embodiment, the first and second electrode films, the first and second metal oxide layers, the light emitting layer, the buffer layer, the hole transport layer, the electron transport layer, or any of them There are no particular restrictions on the method of forming a layer that also serves as several layers. Chemical vapor deposition methods (CVD) such as plasma CVD, thermal CVD, and laser CVD, which are vapor deposition methods, vacuum deposition, sputtering, and ion plating. Uses dry plating methods such as dry spraying, thermal spraying, and wet plating methods such as electrolytic plating, immersion plating, and electroless plating, sol-gel method, MOD method, spray pyrolysis method, and fine particle dispersion. A printing technique such as a doctor blade method, a spin coating method, an ink jet method, and a screen printing method can be used, and an appropriate method according to the material can be selected and used.

  As described above, the buffer layer included in the organic electroluminescent element of the present embodiment is preferably a layer formed by applying a solution containing an organic compound. By forming a buffer layer having a predetermined thickness by coating, it is possible to effectively suppress crystallization of a low molecular compound formed on the buffer layer.

The method for applying the solution containing the organic compound is not particularly limited, and spin coating method, casting method, gravure coating method, bar coating method, roll coating method, dip coating method, spray coating method, screen printing method, offset printing method. Various coating methods such as an ink jet printing method can be used. Among these, the spin coat method is preferable.
By coating and forming the buffer layer, the unevenness present on the surface of the first metal oxide layer is smoothed, so that crystallization of the low molecular compound to be formed next on the buffer layer is suppressed.

  The solvent used for preparing the solution containing the organic compound is not particularly limited as long as it can dissolve the organic compound. Tetrahydrofuran (THF), toluene, xylene, chloroform, dichloromethane, dichloroethane, chlorobenzene 1 type, or 2 or more types, such as cyclopentanone, can be used. Among these, THF, toluene, chloroform, dichloroethane, and cyclopentanone are preferable.

  The solution containing the organic compound preferably has a concentration of the organic compound in the solvent of 0.05 to 10% by mass. With such a concentration, it is possible to suppress the occurrence of uneven coating and unevenness when applied. The concentration of the organic compound in the solvent is more preferably 0.1 to 5% by mass, and still more preferably 0.1 to 3% by mass.

  The buffer layer preferably has an average thickness of 5 to 100 nm. When the average thickness is within such a range, the effect of suppressing crystallization of the low molecular compound layer including the light emitting layer can be sufficiently exhibited. If the average thickness of the buffer layer is less than 5 nm, the unevenness present on the surface of the first metal oxide cannot be sufficiently smoothed, and the effect of forming the buffer layer due to an increase in leakage current is sufficiently exhibited. There is a risk that it will not be possible. On the other hand, when the average thickness of the buffer layer is larger than 100 nm, the driving voltage is increased, which is not practically preferable. Further, when a compound having a preferable structure in the present embodiment described later is used as the organic compound, the buffer layer can sufficiently exhibit the function as the electron transport layer. The average thickness of the buffer layer is more preferably 10 to 60 nm.

  The organic electroluminescent element of this embodiment may be one in which each layer constituting the organic electroluminescent element is laminated on a substrate. When each layer is laminated on the substrate, it is preferable that each layer is formed on the first electrode film formed on the substrate. In this case, the organic electroluminescence device of this embodiment may be a top emission type that extracts light to the side opposite to the side where the substrate is present, or a bottom emission type that extracts light to the side where the substrate is present. There may be.

  Examples of the substrate material include transparent resin materials such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, and polyarylate, and quartz glass and soda glass. Glass materials and the like, and one or more of these 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.

  In the organic electroluminescent element of the present embodiment, the organic compound forming the buffer layer is not particularly limited as long as the organic compound layer can be formed by coating, but examples of the organic compound include trans-type polyacetylene, Polyacetylene compounds such as cis polyacetylene, poly (di-phenylacetylene) (PDPA), poly (alkyl, phenylacetylene) (PAPA); poly (para-phenvinylene) (PPV), poly (2,5-di-) Alkoxy-para-phenylenevinylene) (RO-PPV), cyano-substituted-poly (para-phenvinylene) (CN-PPV), poly (2-dimethyloctylsilyl-para-phenylenevinylene) (DMOS-PPV), poly (2-Methoxy, 5- (2′-ethylhexoxy) -para-phenylene vinyle ) Polyparaphenylene vinylene compounds such as (MEH-PPV); polythiophene compounds such as poly (3-alkylthiophene) (PAT), poly (oxypropylene) triol (POP); poly (9,9-dioctyl) Poly (9,9-dialkylfluorene) such as fluorene (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-divinylenefluorenyl-ortho-co (anthracene) Polyfluorene compounds such as -9,10-diyl); poly (para-phenylene) (PPP) Polyparaphenylene compounds such as poly (1,5-dialkoxy-para-phenylene) (RO-PPP); polycarbazole compounds such as poly (N-vinylcarbazole) (PVK); poly (methylphenylsilane) ) (PMPS), poly (naphthylphenylsilane) (PNPS), poly (biphenylylphenylsilane) (PBPS), boron-containing compounds described in JP2013-239916A, And polyamines described in 168014. These may be used alone or in combination of two or more.

  As described above, according to the organic electroluminescent element of this embodiment, the organic electroluminescent element of the present embodiment is superior in emission characteristics such as emission efficiency and emission lifetime as compared with the so-called organic / inorganic hybrid type organic electroluminescent element. This organic-inorganic hybrid type organic electroluminescent element is one in which the necessity of strictly sealing each layer is reduced, as in the case of an organic electroluminescent element in which each layer constituting the organic electroluminescent element is composed of an organic substance. The organic electroluminescence element of this embodiment having such advantages and excellent light emission characteristics can be suitably used as a material for a display device or a lighting device.

  In addition, the electron injection layer is formed of a layer containing ITZO, and can function as an electron injection layer having good electron mobility, thereby realizing high-luminance and high-contrast display or high-luminance illumination. it can.

  The display device and the illumination device according to this embodiment are arranged to display a plurality of organic electroluminescent elements and perform image display and surface light emission using this element array group. This is because the organic electroluminescent device according to the embodiment is used. As a result, it is possible to display a high-brightness and high-contrast image and to function as a high-brightness light source.

  Hereinafter, the organic electroluminescent device and the method for manufacturing the organic electroluminescent device according to the present invention will be further described using specific examples.

<Examples of organic electroluminescence device>
The organic electroluminescent element according to this example has the configuration shown in FIG.
That is, the organic electroluminescent element 10 comprises a transparent substrate 1 made of glass, an ITO electrode film 2 that is a cathode, an electron injection layer 3 made of ITZO, a buffer layer 4, an electron transport layer 4a, and an organic layer. The light-emitting layer 5 is composed of a hole transport layer 6, a hole injection layer 7 made of HAT-CN, and an Al electrode film 8 serving as an anode.

<Examples and Comparative Examples Related to Manufacturing Method of Organic Electroluminescent Device>
In the following Examples and Comparative Examples, the average thickness of each layer constituting the organic electroluminescent element was measured using a stylus type step meter (product name “Alpha Step IQ”, manufactured by KLA Tencor).

(Example)
[1] A commercially available glass transparent substrate (hereinafter also simply referred to as a substrate) 1 with an ITO electrode film 2 having an average thickness of 0.7 mm is prepared, and this substrate 1 is used as a mirrortron having an ITO target. It fixed to the substrate holder in the chamber of a sputtering device. At this time, a metal mask was additionally provided so that the ITO electrode film 2 on the substrate 1 could be patterned to a width of 3 mm. After reducing the pressure in the chamber to about 1 × 10 ⁻⁴ Pa, sputtering was performed with argon and oxygen introduced. Thereby, the ITO electrode film 2 having a thickness of 90 nm was formed.

[2] Next, the substrate 1 was fixed to a substrate holder in a chamber of a magnetron sputtering apparatus having an ITZO target with a metal mask. After reducing the pressure in the chamber to about 1 × 10 ⁻⁴ Pa, sputtering of ITZO was performed in the same pattern as ITO with argon and oxygen introduced. Thereby, an electron injection layer (ITZO film) 3 having a thickness of 10 nm was formed. Thereafter, ultrasonic cleaning was performed in acetone and isopropanol for 10 minutes, respectively, and the mixture was further boiled in isopropanol for 5 minutes. The substrate 1 subjected to such treatment was taken out of isopropanol, dried by nitrogen blowing, and UV ozone cleaning was performed for 20 minutes.

  [3] Next, a 1% by weight cyclopentanone solution of a boron-containing compound (see Chemical Formula 1 below) was prepared. The substrate 1 prepared in the step [2] was set on a spin coater. The chemical 1 solution was dropped on the substrate 1 and rotated at 2000 rpm for 30 seconds to form a buffer layer 4 containing a boron-containing organic compound. Further, this was annealed for 1 hour with a hot plate set at 150 ° C. in a nitrogen atmosphere. Thereby, the buffer layer 4 having an average film thickness of 30 nm was formed.

[4] Next, the substrate 1 formed up to the buffer layer 4 was fixed to a substrate holder in a chamber of a vacuum evaporation apparatus. Bis [2- (o-hydroxyphenylbenzothiazole) zinc (II) (ZnBTZ2, Chemical Formula 2 (Chemical Formula 2)), Tris [1-phenylisoquinoline-C2, N] iridium (III) (Ir (piq) 3, Chemical Formula 3 (Chemical Formula 3)), N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (α-NPD, Chemical Formula 4 (Chemical Formula 4) ), N4, N4′-bis (dibenzo [b, d] thiophen-4-yl) -N4, N4′-diphenylbiphenyl-4,4′-diamine (DBTPB, Chemical Formula 5 (Chemical Formula 5)), 1,4 , 5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile (HATCN, chemical formula 6 (chemical formula 6)) and Al are put in a crucible and set in a vapor deposition source. It was a. the vacuum evaporation apparatus to about 1 × ¹⁰ -5 Pa Then, ZnBTZ2 was deposited to a thickness of 10 nm to form an electron transport layer 4a, and a light-emitting layer was formed by co-evaporation with ZnBTZ2 as a host and (Ir (piq) 3) as a dopant at a thickness of 25 nm. (Piq) 3) was adjusted to 6% with respect to the entire light emitting layer, DBTPB was deposited at 10 nm, and α-NPD was deposited at 30 nm to form a hole transport layer 6. Next, HATCN was deposited. Vapor deposition was performed to a film thickness of 10 nm, and finally, Al (anode) was deposited to a film thickness of 100 nm to produce an organic electroluminescent element 10. When the second electrode was deposited, stainless steel was deposited. The vapor deposition surface was made into a strip shape with a width of 3 mm using a mask, that is, the light emitting area of the produced organic electroluminescent element was 9 mm ² .

(Comparative example)
An organic electroluminescent element 10 was produced in the same manner as in the above example except that ZnO was formed instead of the ITZO film. Example [1] An ITO film was formed in the same manner as described above. Next, the substrate 1 was fixed to a substrate holder in a chamber of a magnetron sputtering apparatus having a ZnO target with a metal mask. After reducing the pressure in the chamber to about 1 × 10 ⁻⁴ Pa, sputtering of ZnO was performed in the same pattern as ITO with argon and oxygen introduced. Thereby, an electron injection layer (ZnO film) 3 having a thickness of 10 nm was formed.

(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. The light emission luminance was measured with “LS-110” manufactured by Konica Minolta.
FIG. 2 shows the drive voltage-luminance characteristics of the organic electroluminescent elements prepared in Examples and Comparative Examples. Compared with the comparative example in which ZnO is formed as the electron injection layer, the example in which the electron injection layer 3 is formed from ITZO has higher luminance at the same drive voltage.

  FIG. 3 shows the external quantum efficiency-luminance characteristics of the device. It can also be seen that the embodiment using ITZO for the electron injection layer 3 has a higher external quantum efficiency. While the ZnO electron mobility greatly depends on the film quality and high electron mobility is difficult to obtain, ITZO can easily obtain high electron mobility. Therefore, it is clear that the ITZO film is a material that can be used as the electron injection layer 3 of the organic electroluminescent element 10. In particular, when combined with an ITZO-TFT element, a high-brightness and high-contrast display can be easily realized.

1 Transparent substrate 2 Electrode film (cathode, ITO film)
3 Electron injection layer (first metal oxide layer, ITZO film)
4 Buffer Layer 4a Electron Transport Layer 5 Light Emission Layer 6 Hole Transport Layer 7 Hole Injection Layer 8 Electrode Film 10 Organic Electroluminescent Device

Claims (6)

An organic electroluminescence device in which a plurality of layers are laminated between a first electrode film that is a cathode and a second electrode film that is an anode, wherein the plurality of layers includes the first electrode film. In order from the side, comprising at least a plurality of layers including an electron injection layer having an electron injection function and a light emitting layer,
The organic electroluminescence device according to claim 1, wherein the electron injection layer is a layer containing InSnZnO.   The plurality of layers are, in order from the first electrode film side, at least an electron injection layer having an electron injection function, a light emitting layer, and a hole injection layer having a hole injection function. 2. The organic electroluminescent element according to 1.   The plurality of layers include, in order from the first electrode film side, at least an electron injection layer having an electron injection function, a buffer layer, a light emitting layer, a hole transport layer, and a hole injection layer having a hole injection function. The organic electroluminescent element according to claim 1, wherein the organic electroluminescent element is laminated.   A display device formed using the organic electroluminescent element according to claim 1.   It forms using the organic electroluminescent element of any one of Claims 1-3, The illuminating device characterized by the above-mentioned. A first electrode film that is a cathode and a second electrode film that is an anode are arranged on the substrate from the substrate side in this order or the reverse order, and the first electrode film and the anode are arranged between the two electrode films. A method of manufacturing an organic electroluminescent device comprising: laminating a plurality of layers including at least an electron injection layer made of InSnZnO having an electron injection function and a light emitting layer in order from one electrode film side .

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