JP2017034062A - Organic electroluminescent element, display device, illumination device, and manufacturing method of organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element capable of making electron mobility of an electron injection layer excellent and exerting other useful effects, a display device, an illumination device, and a manufacturing method of the organic electroluminescent element.SOLUTION: An organic electroluminescent element 10 is formed by laminating on a transparent substrate 1 a first electrode film (negative electrode) 2 made of an ITO film, an electron injection layer (first metal oxide film) 3 made of a GaOfilm, a buffer layer 4, an electron transport layer 4a, a light-emitting layer 5, a hole transport layer 6, a hole injection layer 7, and a second electrode film (positive electrode) 8 in this order.SELECTED DRAWING: Figure 1

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, and more particularly to an organic electroluminescent element suitable for a flexible display device, an illuminating device, or the like.

  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 device, the lower electrode serves as an anode: see the following non-patent documents 1 and 2)).

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 to be usable (see Patent Documents 1 and 2 below). 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 from the anode. There is a strong demand for new metal oxide materials that can block the holes that are carried well.

The present invention has been made in view of the above circumstances, an organic electroluminescence device capable of significantly improving the electron mobility of the electron injection layer and capable of blocking well the holes moving from the anode to the cathode, An object of the present invention is to provide a display device, a lighting device, and a method for manufacturing an organic 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, at least a plurality of layers including an electron injection layer having an electron injection function and a light emitting layer are laminated,
The electron injection layer is a layer containing Ga ₂ O ₃ .
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”.

The above-mentioned “Ga ₂ O ₃ ” is a general term for gallium oxide-based compositions, and when it is in an amorphous state, in addition to “Ga ₂ O ₃ ”, “GaO” and “GaO ₂ ”. And the like are also included.

  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. In addition, a plurality of layers including at least an electron injection layer made of Ga ₂ O ₃ having an electron injection function and a light emitting layer are disposed between the two electrode films in order from the first electrode film side. It is characterized by laminating.

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 injecting layer having an electron injecting function and a light emitting layer are stacked in this order from the electrode film side, and this electron injecting layer is a layer containing Ga ₂ O ₃ .

Although Ga ₂ O ₃ is a metal oxide, it has a good electron injection performance equal to or higher than that of zinc oxide or 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. It can be easily formed as a very good electron injection layer. Further, compared with ZnO, the energy of the valence band is large and the ionization energy from the vacuum level is large, so that the performance of blocking (blocking) the movement of holes injected from the anode to the cathode is excellent.

This makes it possible to easily realize high-luminance and high-contrast image display and light emission illumination.
In addition, since Ga ₂ O ₃ 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 applied voltage-current density characteristic at the time of driving each organic electroluminescent element which concerns on an Example and a comparative example. It is a graph which shows the applied voltage-luminance characteristic at the time of driving each organic electroluminescent element which concerns on an Example and a comparative example. Shows the energy levels of the cathode and the oxide layer ((A) is ZnO, (B) for _Ga 2 _{O 3)} it is. Shows how the energy level and holes of the cathode and the oxide layer are accumulated ((A) is ZnO, (B) for _Ga 2 _{O 3)} it is. It is a graph which shows the current density-external quantum efficiency characteristic at the time of driving each 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 Ga ₂ O ₃ .

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 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.

To solve this problem, it is formed by applying a solution containing an organic compound between an electron injection layer (Ga ₂ O ₃ film) which is a first metal oxide layer and a low molecular compound layer including a light emitting layer. When a buffer layer having an average thickness of 5 to 100 nm is provided, the crystallization of the low molecular compound in the low molecular compound layer is suppressed, whereby the organic-inorganic hybrid organic electroluminescent element can be used as a light emitting layer or the like from the low molecular compound. Even when the layer is formed, the leakage current can be suppressed and uniform surface 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 of the preferred embodiments 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 Ga ₂ O _3. An electron injection layer (first metal oxide layer) 3 made of a film, a buffer layer 4, an electron transport layer 4a, a light emitting layer 5, a hole transport layer 6, and a hole injection layer (second metal) An 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 a Ga ₂ O ₃ film, and a buffer layer 4. And a light emitting layer 5, a hole injection layer 7, and a second electrode film (anode) 8, and any of these layers also serves as a hole transport layer and an electron transport layer. It is one of the preferable forms of the organic electroluminescent element of this embodiment.

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), InSnZnO (indium zinc oxide tin, ITZO), In ₃ O ₃ , SnO ₂ , Sb-containing SnO ₂ , oxides such as Al-containing ZnO, and the like. 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 Ga ₂ O ₃ (gallium oxide) 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, as in the organic electroluminescent device of the present embodiment includes the electrode an electron injection layer made of an electron injection layer (Ga ₂ O ₃ containing Ga ₂ O ₃ on the surface of the (cathode, the first electrode film) : The same applies hereinafter), a 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 Ga ₂ O ₃ is about 3.5 eV, and the electron injection property of zinc oxide or the like Compared with the metal oxide layer, the Ga ₂ O ₃ electron injection is equivalent or higher.

Moreover, since Ga ₂ O ₃ has a larger valence band energy than zinc oxide or the like, it is considered that the hybrid organic EL element is more suitable as an electron injection layer. This is because it is difficult to inject electrons from the cathode in the hybrid organic EL device, and hole injection / transport from the anode is dominant, and holes are observed as leakage current when the hole blocking property is poor. This is because a decrease in luminous efficiency is expected.

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 (Ga ₂ O ₃ ) 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.

In the organic electroluminescent element of the present invention, the material for forming the light emitting layer may be a low molecular compound or a high molecular compound, or a mixture thereof.
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 Japanese Patent Application No. 2010-230995 And boron compound polymer materials described in Japanese Patent Application No. 2011-6457.

As the low molecular weight material forming the light emitting layer, in addition to a metal complex functioning as a host described later and a phosphorescent light emitting material, 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); benzene compounds such as distyrylbenzene (DSB) and diaminodistyrylbenzene (DADSB), naphthalene such as naphthalene and nile red Compounds, phenanthrene compounds such as phenanthrene, chrysene, chrysene compounds such as 6-nitrochrysene, perylene, N, N′-bis (2,5-di-t-butylphenyl) -3,4,9 , 10-perylene-di-carboximide (BPPC), perylene compounds such as coronene, anthracene compounds such as anthracene and bisstyrylanthracene, pyrene compounds such as pyrene, 4- ( Di-cyanomethylene) -2-methyl-6- (para-dimethyl) Pyryl compounds such as tilaminostyryl) -4H-pyran (DCM), acridine compounds such as acridine, stilbene compounds such as stilbene, 4,4′-bis [9-dicarbazolyl] -2,2 ′ -Carbazole compounds such as biphenyl (CBP), 4,4'-bis (9-ethyl-3-carbazovinylene) -1,1'-biphenyl (BCzVBi), and thiophene compounds such as 2,5-dibenzoxazolethiophene Benzoxazole compounds such as benzoxazole, benzimidazole compounds such as benzimidazole, benzothiazole compounds such as 2,2 ′-(para-phenylenedivinylene) -bisbenzothiazole, bistyryl (1,4 -Diphenyl-1,3-butadiene), tetraphenylbut Butadiene compounds such as diene, naphthalimide compounds such as naphthalimide, coumarin compounds such as coumarin, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, Cyclopentadiene compounds such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP), quinacridone compounds such as quinacridone and quinacridone red, pyrrolopyridine, and thiadiazolopyridine Pyridine compounds, spiro compounds such as 2,2 ′, 7,7′-tetraphenyl-9,9′-spirobifluorene, phthalocyanine (H ₂ Pc), metal or non-metal phthalocyanines such as copper phthalocyanine Compounds, and further, JP2009-155325A Boron compound material, and the like according to broadcast and 2010-28273 Japanese Patent Application No., it can be used alone or in combination of two or more thereof.

  As a material of the light emitting layer of the organic electroluminescent element of the present invention, when a metal complex that functions as a host below and a low molecular material that forms the light emitting layer in addition to the guest material, the content ratio of the low molecular material is It is preferable that it 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 organic electroluminescent device of the present invention can use the above-mentioned polymer compound and low-molecular compound as a material for the light-emitting layer, but the light-emitting layer contains one kind of metal complex that functions as a host, and the low-molecular compound as a guest therein It is preferable that the luminescent material is dispersed. By using such a light-emitting layer in which a host-guest, which is a low molecular compound, is combined, the organic electroluminescent element has excellent light emission characteristics such as light emission efficiency and drive life.

  The host of the light emitting layer has a role of moving the energy and electrons to and from the guest to bring the guest into an excited state, and the excitation energy of the host that moves energy and electrons to and from the guest is the excitation energy of the guest Is preferably larger. The metal complex used as the host of the light emitting layer can be used as long as it has electrical conductivity and is an amorphous material and has such a relationship with the light emitting material used as the host. As a metal complex used as a host, the following formula (1);

(In the formula (1), the dotted arc represents that a ring structure is formed together with a part of the skeleton part connecting the oxygen atom and the nitrogen atom, and the ring structure formed including Z and the nitrogen atom. Is a heterocyclic ring structure, and X ^′ and X ^″ are the same or different and each represents a hydrogen atom or a monovalent substituent serving as a substituent of the ring structure and forms a dotted arc portion. And X ^′ and X ^″ may combine to form a new ring structure together with a part of two ring structures represented by dotted arcs. The dotted line in the skeletal part connecting the nitrogen atom represents that two atoms connected by the dotted line are bonded by a single bond or a double bond, M represents a metal atom, and Z represents a carbon atom or a nitrogen atom. The arrow from the nitrogen atom to M indicates that the nitrogen atom is coordinated to the M atom. ^0, monovalent .m representing a substituent or a divalent linking group represents the number of R ^0, a number of 0 or 1 .n is .r representing the valence of the metal atom M is 1 Or a number of 2.), a metal complex represented by the following formula (2);

(In the formula (2), X ^′ and X ^″ are the same or different and each represents a hydrogen atom or a monovalent substituent serving as a substituent of the quinoline ring structure, and a plurality of X ^′ and X ^″ are bonded to the quinoline ring structure. M represents a metal atom, and an arrow from the nitrogen atom to M represents that the nitrogen atom is coordinated to the M atom, and R ⁰ is a monovalent substituent or a divalent linkage. M represents the number of R ^{0 and is} the number of 0 or 1. n represents the valence of the metal atom M. r is the number of 1 or 2. Complex,
Following formula (3);

(In the formula (3), the dotted arc represents that a ring structure is formed together with a part of the skeleton part connecting the oxygen atom and the nitrogen atom, and the ring structure formed including Z and the nitrogen atom. Is a heterocyclic ring structure, and X ^′ and X ^″ are the same or different and each represents a hydrogen atom or a monovalent substituent serving as a substituent of the ring structure and forms a dotted arc portion. And X ^′ and X ^″ may combine to form a new ring structure together with a part of two ring structures represented by dotted arcs. The dotted line in the skeletal part connecting the nitrogen atom represents that two atoms connected by the dotted line are bonded by a single bond or a double bond, M represents a metal atom, and Z represents a carbon atom or a nitrogen atom. The arrow from the nitrogen atom to M indicates that the nitrogen atom is coordinated to the M atom. The solid line arc connecting the .X ^a and X ^b representing the valence of the metal atom M represents that the X ^a and X ^b are bonded via at least one other atom, X ^a and X ^b with may form a ring structure. in addition may contain a coordinate bond in binding between X ^a and X ^b via at least one other atom .X ^a, X ^b Are the same or different and each represents an oxygen atom, a nitrogen atom, or a carbon atom, and an arrow from ^Xb to M represents that ^Xb is coordinated to an M atom. It is the number of -3.) The metal complex represented by this is mentioned, These 1 type (s) or 2 or more types can be used.

  In the above formula (1), when r is 1, a metal complex represented by the following formula (4-1) having one M atom in the structure is obtained, and when r is 2, M atom is in the structure. It becomes a metal complex represented by the following formula (4-2).

  In the above formulas (1) and (3), the ring structure represented by the dotted arc may be a ring structure consisting of one ring or a ring structure consisting of two or more rings. . Examples of such a ring structure include aromatic rings and heterocyclic rings having 2 to 20 carbon atoms, and aromatic rings such as benzene ring, naphthalene ring and anthracene ring; diazole ring, thiazole ring, isothiazole ring, oxazole ring, Oxazole ring, thiadiazole ring, oxadiazole ring, triazole ring, imidazole ring, imidazoline ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, diazine ring, triazine ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, Heterocycles such as a benzotriazole ring can be mentioned.

  Among these, benzene ring, thiazole ring, isothiazole ring, oxazole ring, isoxazole ring, thiadiazole ring, oxadiazole ring, triazole ring, imidazole ring, imidazoline ring, pyridine ring, pyridazine ring, pyrimidine ring, benzimidazole ring , A benzothiazole ring, a benzoxazole ring, and a benzotriazole ring are preferable.

In the above formulas (1) to (3), the substituent that the ring structure represented by X ^′ and X ^″ has as a halogen atom, an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, carbon An aralkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, an aryl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, Arylamino group, cyano group, amino group, acyl group, C1-C20, preferably C1-C10 alkoxycarbonyl group, carboxyl group, C1-C20, preferably C1-C10 alkoxy group An alkylamino group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, a dialkylamino group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. The Alla Kiruamino group, having 1 to 20 carbon atoms, preferably a haloalkyl group having 1 to 10 carbon atoms, a hydroxyl group, an aryloxy group, and a carbazolyl group.
In addition, when the substituent which the ring structure represented by X ^′ and X ^″ has is an aryl group or an arylamino group, the aromatic ring contained in the aryl group or arylamino group may further have a substituent. Often, the substituents in that case are the same as the specific examples of the substituents represented by X ^′ and X ^″ .

  A new ring structure together with a part of the two ring structures represented by the dotted arc by combining the substituents of the two ring structures represented by the dotted arc shown in the above formulas (1) and (3) As a newly formed ring structure, a 5-membered ring structure or a 6-membered ring structure can be cited, and a ring structure combining two ring structures represented by dotted arcs and a new ring structure Examples of the structure include structures represented by the following formulas (5-1) and (5-2).

  In the above formulas (1) to (3), the metal atom represented by M is preferably a metal atom of Group 1, Group 3, Group 10, Group 10, Group 12 or Group 13 of the periodic table, zinc, aluminum Any of gallium, platinum, rhodium, iridium, beryllium, and magnesium is preferable.

In the above formulas (1) and (2), when R ⁰ is a monovalent substituent, the monovalent substituent may be any of the following formulas (6-1) to (6-3). preferable.

(In the formula, Ar ^{1 to} Ar ⁵ represent an aromatic ring, a heterocyclic ring, or a structure in which two or more aromatic rings or heterocyclic rings are directly bonded, and Ar ^{3 to} Ar ^5. May be the same structure or different structures, and Q ⁰ represents a silicon atom or a germanium atom.)

Specific examples of the aromatic ring or heterocyclic ring of Ar ^{1 to} Ar ⁵ include the same examples as the specific examples of the aromatic ring or heterocyclic ring having the ring structure represented by the dotted arc in the above formula (1). Examples of the structure in which two or more aromatic rings or heterocyclic rings are directly bonded include a structure in which two or more ring structures mentioned as specific examples of these aromatic rings or heterocyclic rings are directly bonded. In this case, the two or more aromatic rings or heterocyclic rings directly bonded may have the same ring structure or different ring structures.
Specific examples of the substituent for the aromatic ring or the heterocyclic ring include the same examples as the specific examples of the substituent for the aromatic ring or the heterocyclic ring having a ring structure represented by the dotted arc in the above formula (1). .

In the above formulas (1) and (2), when R ⁰ is a divalent linking group, R ⁰ is preferably either —O— or —CO—.

In the above formula (3), X ^a, and X ^b, structure formed by the solid line arc connecting the X ^a and X ^b is a ring structure may have one or more comprise. The ring structure may include X ^a and X ^b, and the ring structure in that case is the same as the ring structure represented by the dotted arc in the above formulas (1) and (3). And a pyrazole ring. A structure in which a pyrazole ring is formed including X ^a and X ^b is preferable.

In the above formula (3), the solid arc connecting X ^a and X ^b may be composed of only carbon atoms or may contain other atoms. Examples of other atoms include a boron atom, a nitrogen atom, and a sulfur atom.
The solid line arc connecting the X ^a and X ^b is, X ^a, the ring structure other than the ring structure formed including a X ^b may include one or more, as a ring structure of the case Is the same as the ring structure represented by the dotted arc in the above formulas (1) and (3), and a pyrazole ring.

  Examples of the structure represented by the above formula (3) include the structure of the following formula (7).

In the above formula (7), R ^{1 to} R ³ are the same or different and each represents a hydrogen atom or a monovalent substituent. The arrow from the nitrogen atom to M and the arrow from the oxygen atom to M represent that the nitrogen atom and the oxygen atom are coordinated to the M atom. The dotted arc, the dotted line in the skeleton part connecting the oxygen atom and the nitrogen atom, X ^′ , X ^″ , M, Z, n, m ′ are the same as in the above formula (3).
As monovalent substituents of R ^{1 to} R ^{3 in} the above formula (7), the same substituents as those in the ring structures represented by X ^′ and X ^″ in the above formulas (1) to (3) Is mentioned.

  Specific examples of the compound represented by the above formula (1) include compounds having structures represented by the following formulas (8-1) to (8-40).

Specific examples of the compound represented by the above formula (2) include compounds having structures represented by the following formulas (9-1) to (9-3).

  Specific examples of the compound represented by the above formula (3) include compounds having structures represented by the following formulas (10-1) to (10-8).

As the metal complex in the present invention, one or more of the above-mentioned compounds can be used, and among these, bis [2- (2-benzothiazolyl) phenolate represented by the above formula (8-11)] Zinc, bis (10-hydroxybenzo [h] quinolinato) beryllium (Bebq ₂ ) represented by the above formula (8-34), bis [10] represented by the above formula (8-35)
2- (2-Hydroxyphenyl) -pyridine] beryllium (Bep ₂ ) is preferred.

The light emitting layer of the organic electroluminescent element of the present invention preferably contains a phosphorescent material. By including the phosphorescent light emitting material as a guest, the organic electroluminescent element of the present invention is superior in luminous efficiency and driving life.
Moreover, as a phosphorescence-emitting material, the compound represented by either of following formula (11), (12) can be used conveniently.

In the above formula (11), the dotted arc represents that a ring structure is formed together with a part of the skeleton portion composed of oxygen atoms and three carbon atoms, and a ring formed including a nitrogen atom The structure is a heterocyclic structure. X ^′ and X ^″ may be the same or different and each represents a hydrogen atom or a monovalent substituent serving as a substituent of the ring structure, and a plurality of X ^′ and X ^″ may be bonded to the ring structure forming the dotted arc portion. Good. X ^′ and X ^″ may combine to form a new ring structure together with a part of two ring structures represented by dotted arcs. Further, when n is 2 or more, a plurality of X ^′ or X ^″ may be bonded to form one substituent. A dotted line in a skeleton portion composed of a nitrogen atom and three carbon atoms represents that two atoms connected by the dotted line are bonded by a single bond or a double bond. M ′ represents a metal atom. The arrow from the nitrogen atom to M ′ represents that the nitrogen atom is coordinated to the M ′ atom. n represents the valence of the metal atom M ′.

In the above formula (12), the dotted arc represents that a ring structure is formed together with a part of the skeleton composed of oxygen atoms and three carbon atoms, and includes a nitrogen atom. The ring structure is a heterocyclic structure. X ^′ and X ^″ may be the same or different and each represents a hydrogen atom or a monovalent substituent serving as a substituent of the ring structure, and a plurality of X ^′ and X ^″ may be bonded to the ring structure forming the dotted arc portion. Good. X ^′ and X ^″ may combine to form a new ring structure together with a part of two ring structures represented by dotted arcs. A dotted line in a skeleton portion composed of a nitrogen atom and three carbon atoms represents that two atoms connected by the dotted line are bonded by a single bond or a double bond. M ′ represents a metal atom. The arrow from the nitrogen atom to M ′ represents that the nitrogen atom is coordinated to the M ′ atom. n represents the valence of the metal atom M ′. Solid arcs connecting the X ^a and X ^b represents that the X ^a and X ^b are bonded via at least one other atom, form a ring structure together with X ^a and X ^b Also good. X ^a and X ^b are the same or different and each represents an oxygen atom, a nitrogen atom, or a carbon atom. The arrow from ^Xb to M ′ represents that ^Xb is coordinated to the M ′ atom. m ′ is a number from 1 to 3.

  Examples of the ring structure represented by the dotted arc in the above formula (11) and the above formula (12) include C2-C20 aromatic rings and heterocyclic rings, and aromatics such as a benzene ring, a naphthalene ring, and an anthracene ring. Hydrocarbon ring; pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, benzothiazole ring, benzothiol ring, benzoxazole ring, benzoxol ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinoxaline ring, and phenant Heterocycles such as lysine ring, thiophene ring, furan ring, benzothiophene ring and benzofuran ring are exemplified.

The formula (11) and the formula (12) X In ^', X' as the substituent represented by ^', X in the formula ^(1)', X 'is the same as the substituents represented ^by' Can be mentioned.
In the above formula (11) and the above formula (12), the substituents of the two ring structures represented by dotted arcs are bonded to each other and a new one is added together with part of the two ring structures represented by dotted arcs. In the case where a ring structure is formed, examples of the ring structure in which two ring structures represented by dotted arcs and a new ring structure are combined are as shown in the above formulas (5-1) and (5-2). Structure.

  In the above formula (11) and the above formula (12), examples of the metal atom represented by M ′ include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold.

Examples of the structure represented by the above formula (12) include the structures of the following formulas (13-1) and (13-2).

In the above formulas (13-1) and (13-2), R ^{1 to} R ³ are the same or different and each represents a hydrogen atom or a monovalent substituent. In Formula (13-2), when R ^{1 to} R ³ are monovalent substituents, the ring structure may have a plurality of monovalent substituents. The arrow from the nitrogen atom to M ′ and the arrow from the oxygen atom to M ^′ represent that the nitrogen atom and the oxygen atom are coordinated to the M ′ atom. The dotted arc, the dotted line X ^′ , X ^″ , M ′, n, and m ′ in the skeleton composed of a nitrogen atom and three carbon atoms are the same as in formula (12).
Examples of the monovalent substituent of R ^{1 to} R ³ include the same substituents as those in the ring structures represented by X ^′ and X ^″ in the above formulas (1) to (3).

  Specific examples of the compound represented by the above formula (11) or the above formula (12) include compounds represented by the following formulas (14-1) to (14-30).

As the phosphorescent material in the present invention, one or more of the above-described materials can be used. Among these, iridium tris (2-phenylpyridine) represented by the above formula (14-1) ( Ir (ppy) ₃ ), iridium tris (1-phenylisoquinoline) represented by the above formula (14-19) (Ir (piq) ₃ ), iridium bis (2- (2-27) represented by the above formula (14-27) Methyldibenzo- [f, h] quinoxaline) (acetylacetonate) (Ir (MDQ) ₂ (acac)), iridium tris [3-methyl-2-phenylpyridine] represented by the above formula (14-28) ( Ir (mpy) ₃ ) and the like are preferable.

  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.
Further, the average thickness of the light emitting layer can be measured by a quartz oscillator thickness meter in the case of a low molecular compound, and by a contact type step meter in the case of a high molecular compound.

  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, pyrazoline compounds such as 1-phenyl-3- (para-dimethylaminophenyl) pyrazoline, benzine (cyclohexadiene) compounds, triazoles such as triazole Compounds, imidazole compounds such as imidazole, 1,3,4-oxadiazole, oxadiazoles such as 2,5-di (4-dimethylaminophenyl) -1,3,4, -oxadiazole Compounds, anthracene, anthracene compounds such as 9- (4-diethylaminostyryl) anthracene, fluorenone, 2,4,7, -trinitro-9-fluorenone, 2,7-bis (2-hydroxy-3- (2 -Chlorophenylcarbamoyl) -1-naphthylazo) fluoreno Fluorenone compounds such as aniline compounds such as polyaniline, silane compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo- (3,4-c) pyrrolopyrrole, and fluorenes Fluorene compounds such as porphyrin, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, phthalocyanine, copper phthalocyanine, tetra (t-butyl) copper phthalocyanine, iron phthalocyanine or no metal Metal phthalocyanine compounds, copper naphthalocyanine, vanadyl naphthalocyanine, metal or non-metal naphthalocyanine compounds such as monochlorogallium naphthalocyanine, N, N′-di (naphthalen-1-yl) -N, N′— Diphenyl Benzidine, benzidine compounds such as N, N, N ′, N′-tetraphenylbenzidine, and the like can be used, and one or more of these 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 the low molecular weight compound that can be used as the material for the electron transport layer include tris-1,3,5- (3 ′-(pyridine-3) in addition to the boron-containing compound represented by the formula (1) described later. Pyridine derivatives such as '' -yl) phenyl) benzene (TmPyPhB), quinoline derivatives such as (2- (3- (9-carbazolyl) phenyl) quinoline (mCQ)), 2-phenyl-4,6-bis Pyrimidine derivatives such as (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- (1′- Thiol) -5-phenyl-1,2,4-triazole (TAZ) derivatives, oxazole derivatives, 2- (4-biphenylyl) -5- (4-tert-butylphenyl-1,3,4) Oxadiazole derivatives such as (oxadiazole) (PBD), 2,2 ′, 2 ″-(1,3,5-benztriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBI) Imidazole derivatives such as, aromatic ring tetracarboxylic anhydrides such as naphthalene and perylene, bis [2- (
2-hydroxyphenyl) benzothiazolate] zinc (Zn (BTZ) ₂ ), various metal complexes represented by tris (8-hydroxyquinolinato) aluminum (Alq3) and the like, 2,5-bis (6 ′-(2 ′, 2 ''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) and other organic silane derivatives represented by silole derivatives, and the use of one or more of these Can do.
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. Doctors using dry plating methods such as dry plating, thermal spraying, and wet phase plating methods such as electrolytic plating, immersion plating, and electroless plating, sol-gel method, MOD method, spray pyrolysis method, and fine particle dispersion Printing techniques such as a 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-phenylenevinylene ) 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) -9,10-diyl) such as polyfluorene compounds; poly (para-phenylene) (PPP), Poly (p-phenylene) compounds such as li (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 Ga ₂ O ₃ and can function as an electron injection layer having good electron mobility and a property of blocking holes well. Contrast display or high-luminance illumination can be realized.

  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, this organic electroluminescent element 10 includes an ITO electrode film 2 as a cathode, an electron injection layer 3 made of Ga ₂ O ₃ , a buffer layer 4, an electron transport layer 4 a, an organic material on a transparent substrate 1 made of glass. The light-emitting layer 5 is composed of a layer, a hole transport layer 6, a hole injection layer 7 composed 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 a Ga ₂ O ₃ target with a metal mask. After reducing the pressure in the chamber to about 1 × 10 ⁻⁴ Pa, sputtering of Ga ₂ O ₃ was performed in a pattern similar to that of ITO with argon and oxygen introduced. Thereby, an electron injection layer (Ga ₂ O ₃ 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 0.5 wt% cyclopentanone solution of a boron-containing compound (see the following chemical formula 15 (Chemical Formula 15)) 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 15 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 16 (Chemical formula 16)), Tris [1-phenylisoquinoline-C2, N] iridium (III) (Ir (piq) 3, Chemical formula 17 (Chemical formula 17)), N, N′-di (1) -Naphtyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD, Chemical Formula 18), N4, N4'-bis (dibenzo [b, d] Thiophen-4-yl) -N4, N4′-diphenylbiphenyl-4,4′-diamine (DBTPB, chemical formula 19 (chemical formula 19)), 1,4,5,8,9,12-hexaazatriphenylene-2, 3,6,7,10,11-Hexacarbonitrile (HATCN, Chemical Formula 20 (Chemical Formula 20)) and Al were placed in a crucible and set in a vapor deposition source. The inside of the vacuum evaporation apparatus was depressurized to about 1 × 10 ⁻⁵ Pa, and ZnBTZ 2 was formed to a thickness of 10 nm to form an electron transport layer 6. Furthermore, ZnBTZ2 was used as a host and (Ir (piq) 3) was used as a dopant to co-evaporate at 25 nm to form a light emitting layer. At this time, the doping concentration (Ir (piq) 3) was set to 6% with respect to the entire light emitting layer. Next, 10 nm of DBTPB and 30 nm of α-NPD were deposited to form a hole transport layer. Next, HATCN was deposited to a thickness of 10 nm. Finally, Al (anode) was vapor-deposited so as to have a film thickness of 100 nm, and the organic electroluminescent element 3 was produced. When the second electrode was deposited, a deposition mask made of stainless steel was used so that the deposition surface was a strip having a width of 3 mm. 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 Ga ₂ O ₃ film. An ITO film was formed in the same manner as in Example [1]. 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 applied voltage-current density characteristics of the organic electroluminescent elements prepared in Examples and Comparative Examples. Both devices have similar characteristics, but paying attention to the low voltage region below 5V,
Compared with the comparative example in which ZnO is formed as the electron injection layer, the example in which the electron injection layer is formed of Ga ₂ O ₃ has a lower current density at the same driving voltage. On the other hand, FIG. 3 shows applied voltage-luminance characteristics. In the example, higher luminance is obtained with a lower applied voltage. That is, it can be said that the high current value observed in the comparative example of FIG. 2 is due to the leakage current observed when holes injected from the anode escape to the cathode side. As shown in FIG. 4, Ga ₂ O ₃ has a valence band energy larger than that of ZnO and has a high hole blocking property. Therefore, as shown in FIG. 5, the leakage current is suppressed in the embodiment.

FIG. 6 shows the current density-external quantum efficiency characteristics of the device. Also in this case, it is clear that the example using Ga ₂ O ₃ in the injection layer has a high external quantum efficiency particularly in a low current density region. In a hybrid organic EL device in which electron injection is difficult, the hole blocking property of the oxide layer greatly affects the light emission efficiency in the low current density region. Although ZnO has the effect of assisting electron injection from the ITO cathode, Ga ₂ O ₃ has high electron mobility and high hole blocking property, whereas the valence band energy is not so large and hole blocking property is poor. Both can be satisfied. Therefore, it is clear that the Ga ₂ O ₃ film is a useful material that can be suitably used as the electron injection layer of the organic electroluminescence device.

1 Transparent substrate 2 Electrode film (cathode, ITO film)
3 Electron injection layer (first metal oxide layer, Ga ₂ O ₃ 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, at least a plurality of layers including an electron injection layer having an electron injection function and a light emitting layer are laminated,
The organic electroluminescence device, wherein the electron injection layer is a layer containing Ga ₂ O ₃ .   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 electroluminescence device according to claim 1, wherein the organic electroluminescence device 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. 1. An organic electroluminescent element comprising a plurality of layers including at least an electron injection layer made of Ga ₂ O ₃ having an electron injection function and a light emitting layer disposed in order from one electrode film side Manufacturing method.

Images