JP2021009926A - Interface forming layer, organic electroluminescence element, display device, and lighting device - Google Patents

Abstract

To provide an interface forming layer that is compatible with the materials of an anode and a hole injection layer and has good storage stability in the atmosphere, and further provide an organic EL device using the interface forming layer.SOLUTION: An interface forming layer 10 is laminated between a hole injection layer 9 made of an organic matter and an anode 11 made of metal, the interface forming layer comprising metal oxides in which 50 atomic% or more of metal elements are zinc elements. An organic EL element 1 includes a substrate 2, a cathode 3, a light emitting layer 7, a hole injection layer 9, and an anode 11 in this order, and is provided with the interface forming layer 10 between the hole injection layer 9 and the anode 11.SELECTED DRAWING: Figure 1

Description

The present invention relates to an interface-forming layer, and an organic electroluminescence (hereinafter, electroluminescence (electroluminescence) may be referred to as "EL") element, display device, and lighting device using the interface-forming layer.

The organic EL element has features such as being able to be driven at a low voltage, being thin, lightweight, and being flexible. Therefore, the organic EL element is suitably used for a display device, a lighting device, and the like.
The organic EL 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 (for example, Patent Document 1, Patent Document 2 and See Non-Patent Document 3). Examples of the organic EL element include a forward structure in which an anode is arranged between the substrate and the light emitting layer, and a reverse structure in which a cathode is arranged between the substrate and the light emitting layer. In an organic EL element having an inverted structure, when it is used in a display device or the like, a cathode and a transistor or the like can be easily connected.

Conventionally, a metal oxide electrode such as ITO has been used as a cathode material for an inverted organic EL device.
In recent years, an organic EL device having an inverted structure in which a metal oxide stable in the atmosphere and having a small work function is formed on the surface of a cathode has been proposed (see, for example, Non-Patent Document 1 and Non-Patent Document 2). With this organic EL element, electrons can be efficiently injected into the organic layer. Further, this organic EL element has high operational stability in the atmosphere.

Japanese Unexamined Patent Publication No. 2011-184430 Japanese Unexamined Patent Publication No. 2012-151148

APPLIED PHYSICS LETTERS, Volume89, page183510 (2006) Advanced Materials, Volume23, page1829 (2011) H. Cho et al., Science, vol. 350, p. 1222 (2015)

In the conventional organic EL element, there has been a problem that a non-light emitting portion is formed due to deterioration of the electrode material under the influence of moisture and oxygen in the atmosphere. Therefore, in the conventional organic EL element, the organic EL element is tightly sealed to prevent deterioration of the electrode material.
Further, since the reverse structure organic EL element has significantly higher atmospheric stability than the forward structure organic EL element, although the need for strict sealing is low, a practical metal such as Al, which is easily oxidized, is used for the anode. If so, in an unsealed environment in which no barrier film is used, deterioration of the light emitting surface due to deterioration of the hole injection property is confirmed as the anode / hole injection layer interface deteriorates.
Therefore, in order to popularize flexible displays in which deterioration and destruction of the barrier film due to bending can easily occur, realization of a reverse-structured organic EL element having higher atmospheric stability and suppressing deterioration of the anode / hole injection layer interface is realized. is necessary.
Therefore, in order to improve the stability of the organic EL device in the atmosphere, it is required to form an anode / hole injection layer interface capable of maintaining the hole injection property.

The present invention has been made in view of the above circumstances, and provides an interface cambium that is compatible with the materials of the anode and the hole injection layer and has good storage stability (storage life) in the atmosphere. Make it an issue.
Another object of the present invention is to provide an organic EL element, a display device and a lighting device using the above-mentioned interface cambium having good storage stability in the atmosphere.

As a result of diligent studies in order to solve the above problems, the present inventor has formed a layer made of a metal oxide in which 50 atomic% or more of a metal element is a zinc element, a hole injection layer and an anode. The present invention was conceived by finding that the stability of the organic EL element in the atmosphere is improved by laminating between them.
The gist structure of the present invention for solving the above problems is as follows.

The interface-forming layer of the present invention is characterized in that it is laminated between a hole injection layer made of an organic substance and an anode made of a metal, and 50 atomic% or more of the metal element is made of a metal oxide which is a zinc element. To do.
By laminating the interface forming layer of the present invention between the hole injection layer of the organic EL element and the anode, the storage stability of the organic EL element in the atmosphere can be improved.

In the interface cambium of the present invention, the metal oxide preferably has less than 1 oxygen element with respect to 1 zinc element. In this case, by laminating the interface forming layer between the hole injection layer of the organic EL element and the anode, the storage stability of the organic EL element in the atmosphere can be further improved.

The interface cambium of the present invention preferably has an average thickness of 1 to 30 nm. In this case, the coverage of the cambium is improved, the transparency and conductivity of the cambium are improved, and good hole injection property is obtained.

Further, the organic electroluminescence device of the present invention includes a substrate, a cathode, a light emitting layer, a hole injection layer, and an anode in this order.
It is characterized by having the above-mentioned interface forming layer between the hole injection layer and the anode.
The organic electroluminescence element of the present invention has high storage stability in the atmosphere.

Further, the display device of the present invention is characterized by including the above-mentioned organic electroluminescence element. The display device of the present invention has a long storage life and can be used stably for a long period of time.

Further, the lighting device of the present invention is characterized by including the above-mentioned organic electroluminescence element. The lighting device of the present invention has a long shelf life and can be used stably for a long period of time.

According to the present invention, it is possible to provide an interface cambium that is compatible with the materials of the anode and the hole injection layer and has good storage stability (storage life) in the atmosphere.
Further, according to the present invention, it is possible to provide an organic EL element, a display device and a lighting device using an interface cambium having good storage stability in the atmosphere.

It is sectional drawing for demonstrating an example of the organic EL element of this embodiment. It is a luminance-voltage (LV) characteristic of the organic EL element shown in an Example and a comparative example. It is a current density-voltage (JV) characteristic of the organic EL element shown in an Example and a comparative example. It is a light emitting surface image of the organic EL element of an Example and a comparative example photographed after 30 days and 90 days after the start of the storage life test (0 days elapse). In the storage life test, the organic EL element was stored at room temperature and humidity, and was turned on only when the light emitting surface image was acquired for evaluation. For the organic EL devices of Examples and Comparative Examples, it is the ratio of the light emitting area after 30 days and 90 days when the light emitting area after 0 days is 100%.

Hereinafter, the interface cambium, the organic electroluminescence device, the display device, and the lighting device of the present invention will be described in detail based on the embodiments thereof.

<Cambium>
The interface forming layer of the present invention is used for laminating between a hole injection layer made of an organic substance and an electrode made of a metal, and is made of a metal oxide in which 50 atomic% or more of the metal element is a zinc element. It is characterized by that.

The cambium of the present invention is made of a metal oxide containing zinc as a main metal element, and the cambium is made of a metal by laminating it between a hole injection layer made of an organic substance and an anode made of a metal. It is possible to suppress the deterioration of the anode in the atmosphere. Therefore, by laminating the interface forming layer of the present invention between the hole injection layer of the organic EL element and the anode, the storage stability of the organic EL element in the atmosphere is improved, and the hole injection layer and the anode are improved. Oxygen resistance and water resistance are improved, and stable hole injection in the atmosphere becomes possible.
Further, by laminating the interface forming layer of the present invention between the hole injection layer and the anode to form an organic EL element, the need for strictly sealing the organic EL element can be significantly reduced.

In the interface forming layer of the present invention, 50 atomic% or more of the metal element is zinc element, and the ratio of zinc element in the metal element is preferably 60 atomic% or more, more preferably 70 atomic% or more. preferable. If the proportion of zinc element in the metal element of the metal oxide is less than 50 atomic%, the storage stability (storage life) of the interface cambium in the atmosphere cannot be sufficiently improved.
Examples of the metal element in the metal oxide include Al and the like in addition to Zn.

In the interface cambium of the present invention, the metal oxide preferably has less than 1 oxygen element with respect to 1 zinc element. When the number of oxygen elements to 1 zinc element is less than 1 (that is, the oxygen element is deficient as compared with the stable zinc oxide), the deterioration of the metal anode in the atmosphere can be further suppressed. By laminating such an interface forming layer between the hole injection layer of the organic EL element and the anode, the storage stability of the organic EL element in the atmosphere can be further improved. When the metal oxide is zinc oxide, the metal oxide lacking such an oxygen element is represented by ZnO _(1-x) (in the formula, 0 <x <1).
The number of oxygen elements with respect to zinc element 1 is preferably 0.5 or more, more preferably 0.7 or more, and even more preferably 0.8 or more. When the number of oxygen elements with respect to zinc element 1 is 0.5 or more, the transparency of the interface cambium becomes good. The number of oxygen elements with respect to zinc element 1 can be measured by RBS (Rutherford backscattering analysis method).

The interface-forming layer of the present invention has an average thickness of preferably 1 to 30 nm, more preferably 1 to 10 nm, further preferably 1 to 5 nm, and more preferably 2 to 5 nm. More preferred. When the average thickness of the cambium is 1 nm or more, the coverage of the cambium is improved, and when the average thickness is 30 nm or less, the transparency and conductivity of the cambium are good, which is good. Good hole injection property can be obtained. The average thickness of the interface cambium can be measured by a stylus type step meter or spectroscopic ellipsometry.

The metal oxide containing zinc as a main metal element, which is the material of the interface forming layer of the present invention, may be present as a reaction product with a part of the adjacent anode material or the hole injection layer material. By reacting with the material of the adjacent anode and the material of the hole injection layer, the interface between the anode and the hole injection layer becomes stronger, and the stability in the atmosphere becomes even better.

The interface forming layer of the present invention can be formed by, for example, a sputtering method, a vapor deposition method, or the like. Further, the number of oxygen elements to zinc element 1 in the metal oxide constituting the interface forming layer can be determined by controlling the flow rate ratio of the inert gas (argon gas or the like) and the oxygen gas in the reactive sputtering, for example. , Can be adjusted.

The interface forming layer of the present invention is laminated between a hole injection layer made of an organic substance and an anode made of a metal. The hole injection layer and the anode will be described in detail in the section of the organic EL element described later. To do. However, the application of the interface cambium of the present invention is not limited to an organic EL element and a display device or a lighting device equipped with the organic EL element, and can be used, for example, in a thin-film solar cell or the like.

<Organic electroluminescence element>
The organic electroluminescence element of the present invention includes a substrate, a cathode, a light emitting layer, a hole injection layer, and an anode in this order, and is described above between the hole injection layer and the anode. It is characterized by having an interface-forming layer.
Since the organic electroluminescence element of the present invention has the above-mentioned interface forming layer between the hole injection layer and the anode, it has good oxygen resistance and moisture resistance, and has high storage stability in the atmosphere ( Long shelf life).

Next, one aspect of the organic electroluminescence device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining an example of the organic EL element of the present embodiment.

In the organic EL element 1 of the present embodiment shown in FIG. 1, a cathode 3, a light emitting layer 7, and an anode 11 are provided in this order on a substrate 2, and the cathode 3 (electrode) and the anode 11 (electrode) are provided in this order. ), A laminated structure including the light emitting layer 7 is formed.
The laminated structure of the organic EL element 1 of the present embodiment includes an inorganic electron injection layer 4, an organic electron injection layer 5, an electron transport layer 6, a light emitting layer 7, a hole transport layer 8, and a hole injection layer 9. And are formed in this order. The interface forming layer 10 is arranged between the hole injection layer 9 and the anode 11. Here, in the organic EL element 1 shown in FIG. 1, the interface forming layer 10 is made of a metal oxide in which 50 atomic% or more of the metal element is a zinc element.
The organic EL element 1 of the present embodiment has an inverted structure in which the cathode 3 is arranged between the substrate 2 and the light emitting layer 7. The organic EL element 1 shown in FIG. 1 may be a top-emission type that extracts light on the side opposite to the substrate 2, or may be a bottom-emission type that extracts light on the substrate 2 side.

(substrate)
Examples of the material of the substrate 2 include a resin material and a glass material. As the material of the substrate 2, only one kind may be used, or two or more kinds may be used in combination.
Examples of the resin material used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, polyamide, polyether sulfone, polymethylmethacrylate, polycarbonate, polyarylate and the like. When a resin material is used as the material of the substrate 2, the organic EL element 1 having excellent flexibility can be obtained, which is preferable.
On the other hand, examples of the glass material used for the substrate 2 include quartz glass and soda glass.

When the organic EL element 1 is a bottom emission type, a transparent substrate is used as the material of the substrate 2.
On the other hand, when the organic EL element 1 is a top emission type, not only a transparent substrate but also an opaque substrate may be used as the material of the substrate 2. Examples of the opaque substrate include a substrate made of a ceramic material such as alumina, a substrate having an oxide film (insulating film) formed on the surface of a metal plate such as stainless steel, and a substrate made of a resin material.

The average thickness of the substrate 2 is not particularly limited, but is preferably 0.1 to 30 mm, more preferably 0.1 to 10 mm. The average thickness of the substrate 2 can be measured with a digital multimeter and calipers.

(cathode)
As the material of the cathode 3, ITO (tin indium oxide), IZO (zinc oxide), FTO (tin fluorine oxide), InSnZNO (tin zinc oxide, ITZO), In ₃ O ₃ , SnO ₂ , Sb-containing SnO ₂ , Al-containing ZnO and other oxide conductive materials are preferably used. Among these, it is particularly preferable to use ITO, IZO, and FTO as the material of the cathode 3. These conductive materials are preferable as the cathode material for the bottom emission type organic EL element.

On the other hand, in the case of a top-emission type organic EL element, it is preferable to use an electrode having high reflectance such as Ag alloy as the cathode.

The average thickness of the cathode 3 is not particularly limited, but is preferably 10 to 500 nm, and more preferably 100 to 200 nm.

(Inorganic electron injection layer)
As the inorganic electron injection layer 4, for example, oxides of one or more elements selected from zinc, tin, zirconium, silicon, germanium, titanium, and hafnium, which are metal oxides having a low work function, are preferable.

The average thickness of the inorganic electron injection layer 4 is not particularly limited, but is preferably 1 to 1000 nm, more preferably 2 to 100 nm. When the average thickness of the inorganic electron injection layer 4 is 1 nm or more, the effect of having the inorganic electron injection layer 4 can be sufficiently obtained. Further, when the average thickness of the inorganic electron injection layer 4 is 1000 nm or less, the inorganic electron injection layer 4 can be efficiently formed. The average thickness of the inorganic electron injection layer 4 can be measured by a stylus type step meter and spectroscopic ellipsometry.

(Organic electron injection layer)
Examples of the material of the organic electron injection layer 5 include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), and poly (alkyl, phenylacetylene) (PAPA); poly (para). -Fenbinylene) (PPV), poly (2,5-dialkoxy-para-phenylene vinylene) (RO-PPV), cyano-substituted-poly (para-phenylene) (CN-PPV), poly (2-dimethyl) Polyparaphenylene vinylene compounds such as octylsilyl-para-phenylene vinylene) (DMOS-PPV), poly (2-methoxy, 5- (2'-ethylhexoxy) -para-phenylene vinylene) (MEH-PPV); poly (poly ( Polythiophene compounds such as 3-alkylthiophene (PAT), poly (oxypropylene) triol (POPT); poly (9,9-dialkylfluorene) such as poly (9,9-dioctylfluorene) (PDAF), poly ( Dioctylfluorene-alto-benzothiazol) (F8BT), α, ω-bis [N, N'-di (methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2,7- Polyfluorene compounds such as Jill] (PF2 / 6am4), poly (9,9-dioctyl-2,7-dibinylene fluorenyl-altoco (anthracene-9,10-diyl); poly (para-phenylene). ) (PPP), poly (1,5-dialkoxy-para-phenylene) (RO-PPP) and other polyparaphenylene compounds; poly (N-vinylcarbazole) (PVK) and other polycarbazole compounds; Examples thereof include polysilane compounds such as methylphenylsilane (PMPS), poly (naphthylphenylsilane) (PNPS), and poly (biphenylylphenylsilane) (PBPS). One of these may be used. More than a seed may be used.

The average thickness of the organic electron injection layer 5 is not particularly limited, but is preferably 5 to 100 nm, and more preferably 10 to 60 nm. The average thickness of the organic electron injection layer 5 can be measured by a stylus type step meter and spectroscopic ellipsometry. Alternatively, it can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Electronic transport layer)
As the material of the electron transport layer 6, any material that can be usually used as the material of the electron transport layer 6 can be used, and these may be mixed and used.
Examples of low molecular weight compounds that can be used as materials for the electron transport layer 6 include bis [2- (o-hydroxyphenylbenzothiazole] zinc (II) (Zn (BTZ) ₂ )) and tris (8-hydroxyquinolinato). ) Various metal complexes typified by aluminum (Alq ₃ ), boron-containing compounds, pyridine derivatives such as tris-1,3,5- (3'-(pyridine-3 "-yl) phenyl) benzene (TmPyPhB), Kinolin derivatives such as 2- (3- (9-carbazolyl) phenyl) quinoline (mCQ), pyrimidine derivatives such as 2-phenyl-4,6-bis (3,5-dipyridylphenyl) pyrimidine (BPyPPM), pyrazine derivatives, Phenantroline derivatives such as bassofenantroline (BPhen), 2,4-bis (4-biphenyl) -6- (4'-(2-pyridinyl) -4-biphenyl)-[1,3,5] triazine (MPT), etc. Triazine derivatives, triazole derivatives such as 3-phenyl-4- (1'-naphthyl) -5-phenyl-1,2,4-triazole (TAZ), oxazole derivatives, 2- (4-biphenylyl) -5-( Oxaziazole derivatives such as 4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), 2,2', 2 "-(1,3,5-ventryyl) -tris (1-phenyl) Imidazole derivatives such as -1-H-benzimidazole (TPBI), aromatic ring tetracarboxylic acid anhydrides such as naphthalene and perylene, 2,5-bis (6'-(2', 2 "-bipyridyl))-1 , 1-Dimethyl-3,4-Diphenylcyclol (PyPySPyPy) and other syrol derivatives are examples of organic silane derivatives, and one or more of these can be used. BTZ) ₂ is preferable.

The average thickness of the electron transport layer 6 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 40 to 100 nm. The average thickness of the electron transport layer 6 can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Light emitting layer)
The material forming the light emitting layer 7 may be a low molecular weight compound, a high molecular weight compound, or a mixture thereof.

Examples of the polymer compound forming the light emitting layer 7 include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), and poly (alkylphenylacetylene) (PAPA); Para-phenylene) (PPV), poly (2,5-dialkoxy-para-phenylene vinylene) (RO-PPV), cyano-substituted-poly (para-phenylene) (CN-PPV), poly (2- Polyparaphenylene vinylene compounds such as dimethyloctylsilyl-para-phenylene vinylene) (DMOS-PPV), poly (2-methoxy, 5- (2'-ethylhexoxy) -para-phenylene vinylene) (MEH-PPV); poly Polythiophene compounds such as (3-alkylthiophene) (PAT), poly (oxypropylene) triol (POPT); poly (9,9-dialkylfluorene) (PDAF), poly (dioctylfluorene-alto-benzothiazol) (F8BT) ), Α, ω-bis [N, N'-di (methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2,7-zyl] (PF2 / 6am4), poly ( Polyfluorene compounds such as 9,9-dioctyl-2,7-divinylenefluorenyl-altoco (anthracene-9,10-diyl); poly (para-phenylene) (PPP), poly (1,5) Polyparaphenylene compounds such as −dialkoxy-para-phenylene) (RO-PPP); polycarbazole compounds such as poly (N-vinylcarbazole) (PVK); poly (methylphenylsilane) (PMPS), poly ( Polysilane compounds such as naphthylphenylsilane (PNPS) and poly (biphenylylphenylsilane) (PBPS); further, boron compound-based polymer compounds described in JP2011-184430A and JP2012-151148A. And so on.

Examples of the low molecular weight compound forming the light emitting layer 7 include a phosphorus light emitting material, 8-hydroxyquinolin aluminum (Alq ₃ ), tris [1-phenylisoquinolin-C2, N] iridium (III) (Ir (piq) ₃ ). ), Bis [2- (o-hydroxyphenylbenzothiazole] zinc (II) (Zn (BTZ) ₂ ) tris (4-methyl-8-quinolinolate) aluminum (III) (Almq ₃ ), 8-hydroxyquinolin zinc ( Znq ₂ ), (1,10-phenanthroline) -Tris- (4,4,4-trifluoro-1- (2-thienyl) -butane-1,3-geonate) Europium (III) (Eu (TTA) ₃ (Phen)), various metal compounds such as 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphin platinum (II); distyrylbenzene (DSB), diaminodistyrylbenzene ( Benzene compounds such as DADSB), naphthalene compounds such as naphthalene and Nile Red, phenanthrene compounds such as phenanthrene, chrysen compounds such as chrysen and 6-nitrochrycene, perylene, N, N'-bis (2,5-) Di-t-butylphenyl) -3,4,9,10-perylene-di-carboxyimide (BPPC) and other perylene-based compounds, coronen and other coronene-based compounds, anthracene, bisstyrylanthracene and other anthracene-based compounds, pyrene Pyrene compounds such as 4- (di-cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM) and other pyran compounds, acrydin compounds such as acrydin, stillben and the like. Stilben compound, 4,4'-bis [9-dicarbazolyl] -2,2'-biphenyl (CBP), 4,4'-bis (9-ethyl-3-carbazovinylene) -1,1'-biphenyl ( Carbazole compounds such as BCzVBi), thiophene compounds such as 2,5-dibenzoxazolethiophene, benzoxazole compounds such as benzoxazole, benzoimidazole compounds such as benzoimidazole, 2,2'-(para-phenylenedivinylene). ) -Benzothiazole compounds such as bisbenzothiazole, butadiene compounds such as bistilyl (1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene, naphthalimide compounds such as naphthalimide, and coumarin compounds such as coumarin. Compound Products, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, cyclopentadiene such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP) Systems compounds, quinacridone compounds such as quinacridone and quinacridone red, pyridine compounds such as pyrolopyridine and thiadiazolopyridine, and spiros such as 2,2', 7,7'-tetraphenyl-9,9'-spirobifluorene. Examples thereof include compounds, metal or non-metal phthalocyanine compounds such as phthalocyanine (H ₂ Pc) and copper phthalocyanine, and one or more of these can be used.

As the light emitting layer 7, for example, an organic material that emits infrared light can be used in addition to the material that emits visible light. Further, as the material of the light emitting layer 7, other than the organic material, for example, a material having a perovskite structure represented by quantum dots or CH ₃ NH ₃ PbBr ₃ (see, for example, Non-Patent Document 3) may be used. As the material of the light emitting layer 7, a thermally activated delayed fluorescent material may be used in addition to the fluorescent material and the phosphorescent material.

The average thickness of the light emitting layer 7 is not particularly limited, but is preferably 10 to 150 nm, more preferably 20 to 100 nm. The average thickness of the light emitting layer 7 can be measured by a crystal oscillator film thickness meter when the material of the light emitting layer 7 is a low molecular compound, and when the material of the light emitting layer 7 is a high molecular compound, contact is made. It can be measured with a type step meter.

(Hole transport layer)
As the material of the hole transport layer 8, any material that can be usually used as the material of the hole transport layer 8 can be used, and these may be mixed and used.
Materials for the hole transport layer 8 include N4, N4'-bis (dibenzo [b, d] thiophen-4-yl) -N4, N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), 1, Arylcycloalkane compounds such as 1-bis (4-di-para-triaminophenyl) cyclohexane, 1,1'-bis (4-di-para-trilaminophenyl) -4-phenyl-cyclohexane, 4 , 4', 4 "-trimethyltriphenylamine, N, N, N', N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, N, N'-diphenyl-N, N' -Bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (TPD1), N, N'-diphenyl-N, N'-bis (4-methoxyphenyl) -1,1'-Biphenyl-4,4'-diamine (TPD2), N, N, N', N'-tetrakis (4-methoxyphenyl) -1,1'-biphenyl-4,4'-diamine (TPD3), N, Arylamine compounds such as N'-di (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), triphenylaminetetramer (TPTE), N, N, N', N'-tetraphenyl-para-phenylenediamine, N, N, N', N'-tetra (para-tolyl) -para-phenylenediamine, N, N, N', N'- Phenylene diamine compounds such as tetra (meth-tolyl) -meth-phenylenediamine (PDA), carbazole compounds such as carbazole, N-isopropylcarbazole, N-phenylcarbazole, stelvene, 4-di-para-tolylaminostylben, etc. Stilben compounds, oxazole compounds such as OxZ, triphenylmethane compounds such as triphenylmethane and m-MTDATA, pyrazoline compounds such as 1-phenyl-3- (para-dimethylaminophenyl) pyrazoline, benzine (cyclo) Hexadien) -based compounds, triazole-based compounds such as triazole, imidazole-based compounds such as imidazole, 1,3,4-oxadiazol, 2,5-di (4-dimethylaminophenyl) -1,3,4-oxa Oxaziazole compounds such as diazole, 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) Fluolenone compounds such as fluorenone, aniline compounds such as polyaniline, silane compounds, 1,4-dithioketo-3,6-diphenyl-pyrrolo- (3,4-c) Pyrrole compounds such as pyrolopyrrole, fluorene compounds such as fluorene, porphyrin, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, phthalocyanines, copper phthalocyanines, tetra (t-butyl) copper phthalocyanines, iron phthalocyanines. Metallic or metal-free phthalocyanine compounds such as copper naphthalocyanine, vanadyl naphthalocyanine, monochlorogallium naphthalocyanine and other metal or metal-free phthalocyanine compounds, N, N'-di (naphthalen-1-yl) -N , N'-diphenyl-benzidine, N, N, N', N'-tetraphenylbenzidine and the like, and examples thereof include one or more of these compounds.
Among these, arylamine compounds such as DBTPB, α-NPD, and TPTE are preferable.

The average thickness of the hole transport layer 8 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 40 to 100 nm. The average thickness of the hole transport layer 8 can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Hole injection layer)
The hole injection layer 9 may be made of an inorganic material or an organic material, but an organic material is preferable.

When the hole injection layer 9 is an inorganic material, the hole injection layer 9 may be made of vanadium oxide (V ₂ O ₅ ), molybdenum trioxide (molybdenum oxide: MoO ₃ ), ruthenium oxide (RuO ₂ ), or the like. It is preferable to use one kind or two or more kinds of oxides.

On the other hand, when the hole injection layer 9 is an organic material, as the material of the hole injection layer 9, for example, tetrafluorotetracyanoquinodimethane (F4TCNQ) and / or 1,4,5,8,9,12- Hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) and the like can be used. Among these, HAT-CN is particularly preferable.

The average thickness of the hole injection layer 9 is not particularly limited, but is preferably 1 to 1000 nm, more preferably 5 to 50 nm. The average thickness of the hole injection layer 9 can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Cambium)
As described above, the interface cambium 10 is made of a metal oxide in which 50 atomic% or more of the metal element is a zinc element. Zinc oxide is preferable as the material of the interface forming layer 10, but a composite oxide containing zinc oxide as a main component such as Al-containing ZnO (AZO) may be used.

(anode)
Examples of the material of the anode 11 include Au, Pt, Ag, Cu, Al, Mo, Ni, Mg, Bi, and alloys containing these. Among these, it is preferable to use any one of Au, Ag, Al, and Mg as the material of the anode 11.

The average thickness of the anode 11 is not particularly limited, but is preferably, for example, 10 to 1000 nm, and more preferably 30 to 150 nm.
When the organic EL element 1 is a top emission type, it is preferable to use a transparent material as the material of the anode 11. When the organic EL element 1 is a top emission type and an opaque material for irradiation light is used as the material of the anode 11, it can be used as the transparent anode 11 by setting the average thickness to about 10 to 30 nm.
The average thickness of the anode 11 can be measured at the time of film formation with a crystal oscillator film thickness meter.

(Formation method)
In the organic EL element 1 shown in FIG. 1, the method for forming all the layers is not particularly limited, and is a vapor deposition method such as plasma CVD, thermal CVD, laser CVD or other chemical vapor deposition (CVD), or vacuum vapor deposition. , Dry plating method such as sputtering and ion plating, thermal spraying method, and wet plating method such as electrolytic plating, dip plating, and electroless plating, which are liquid phase deposition methods, sol gel method, MOD method, and spray thermal decomposition method. , A printing technique such as a doctor blade method using a fine particle dispersion, a spin coating method, an inkjet method, or a screen printing method can be used, and an appropriate method according to the material can be selected and used.
These methods are preferably selected according to the characteristics of the material of each layer, and the production method may be different for each layer.

<Display device>
The display device of the present invention is characterized by including the above-mentioned organic electroluminescence element. Since the display device of the present invention includes the above-mentioned organic EL element having good storage stability (storage life) in the atmosphere, it has a long storage life and can be used stably for a long period of time. In addition to the organic EL element described above, the display device of the present invention can include other parts generally used in the display device.

<Lighting device>
The lighting device of the present invention is characterized by including the above-mentioned organic electroluminescence element. Since the lighting device of the present invention includes the above-mentioned organic EL element having good storage stability (storage life) in the atmosphere, it has a long storage life and can be used stably for a long period of time. In addition to the organic EL element described above, the lighting device of the present invention can include other parts generally used in the lighting device.

Hereinafter, examples and comparative examples of the present invention will be described. The present invention is not limited to the examples shown below.

(Example 1)
[1] A commercially available transparent glass substrate (hereinafter, also simply referred to as a substrate) 2 having an average thickness of 0.7 mm and having a cathode 3 made of an ITO film (patterned to a film thickness of 150 nm and a width of 3 mm) was prepared. ..

[2] Next, the substrate 2 having the cathode 3 is scrubbed with an alkaline cleaning agent and a PVA sponge, ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and further washed in isopropanol steam for 5 minutes. went. Then, the substrate 2 was taken out from isopropanol, dried by a nitrogen blow, and UV ozone washed for 20 minutes.

[3] Next, the substrate was set in a substrate holder in a mirrortron sputtering apparatus (manufactured by Choshu Industry Co., Ltd.), and a zinc oxide film of 3 nm was formed by reactive sputtering by mirrortron sputtering using a Zn target. Next, the substrate 2 having a zinc oxide film formed on the cathode 3 was heat-treated in the air at 400 ° C. for 1 hour using a hot plate. As a result, the inorganic electron injection layer 4 was formed.

[4] Next, the following structural formula (1):
A 1.0 mass% cyclopentanone solution of the boron-containing compound represented by (1) was prepared. The boron-containing compound was synthesized according to the method described in Synthesis Example 4 of JP-A-2016-54173. The substrate 2 formed up to the inorganic electron injection layer 4 was set on a spin coater, a cyclopentanone solution of the above boron-containing compound was added dropwise, and the mixture was rotated at 3000 rpm for 30 seconds for coating. Further, the substrate 2 coated with the cyclopentanone solution of the boron-containing compound was annealed for 1 hour using a hot plate set at 150 ° C. in a nitrogen atmosphere. As a result, the organic electron injection layer 5 made of a boron-containing compound having an average film thickness of 30 nm was formed.

[5] Next, the substrate 2 formed up to the organic electron injection layer 5 was fixed to the substrate holder in the chamber of the vacuum vapor deposition apparatus. Bis [2- (o-hydroxyphenylbenzothiazole] zinc (II) (Zn (BTZ) ₂ ) represented by the following structural formula ( ₂ ), tris [1-phenylisoquinolin-C2] represented by the following structural formula (3). , N] Iridium (III) (Ir (piq) ₃ ), N, N'-di (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-represented by the following structural formula (4) 4,4'-diamine (α-NPD), N4, N4'-bis (dibenzo [b, d] thiophen-4-yl) -N4, N4'-diphenylbiphenyl-4 represented by the following structural formula (5). , 4'-diamine (DBTPB), 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile represented by the following structural formula (6) ( HAT-CN) and Al were placed in the rutsubo and set in the vapor deposition source.

[6] The inside of the vacuum vapor deposition apparatus was depressurized to about 1 × 10 ^-5 Pa, and Zn (BTZ) ₂ was formed into a 10 nm film to form an electron transport layer 6.
Further, Zn (BTZ) ₂ was used as a host and Ir (piq) ₃ was used as a dopant for co-evaporation at 20 nm to form a light emitting layer 7. At this time, the doping concentration of Ir (piq) _{3 was} adjusted to be 6% by mass with respect to the entire light emitting layer 7.
Next, the hole transport layer 8 was formed by forming a 10 nm film of DBTPB and further forming a 40 nm film of α-NPD.
Next, HAT-CN was deposited with a film thickness of 10 nm to form a hole injection layer 9.

[7] After forming the hole injection layer 9, the substrate is transferred to a mirrortron sputtering device manufactured by Choshu Industry Co., Ltd. without breaking the vacuum, and then the argon gas flow rate is 36 sccm, the oxygen gas flow rate is 4 sccm, and the process gas pressure is 0.26 Pa. Then, a ZnO _0.8 film was formed into a 4 nm film by reactive sputtering to form an interface forming layer 10. The oxidation number of the ZnO _0.8 film was measured by RBS (Rutherford Backscattering Analysis).

[8] Finally, the substrate was transferred to the vacuum vapor deposition apparatus again, and Al was vapor-deposited to a film thickness of 100 nm to form the anode 11. Through the above steps, the organic EL element 1 of Example 1 was obtained.
When the anode 11 was vapor-deposited, a stainless steel vapor deposition mask was used so that the vapor deposition surface had a strip shape with a width of 3 mm. As a result, the light emitting area of the organic EL element 1 was set to 9 mm ² .

(Example 2)
As the interface forming layer 10, a ZnO _1.0 film was formed by reactive sputtering at an argon gas flow rate of 13 sccm, an oxygen gas flow rate of 13 sccm, and a process gas pressure of 0.2 Pa using a mirrortron sputtering device manufactured by Choshu Industry Co., Ltd. Made the organic EL element 1 of Example 2 in the same manner as in Example 1. The oxidation number of the ZnO _1.0 film was measured by RBS (Rutherford Backscattering Analysis).

(Comparative Example 1)
The organic EL element 1 of Comparative Example 1 was produced in the same manner as in Example 1 except that the interface forming layer 10 was not formed.

(Comparative Example 2)
The organic EL element 1 of Comparative Example 2 was produced in the same manner as in Example 1 except that a MoO ₃ film was formed into a 4 nm film by vacuum vapor deposition as the interface forming layer 10. The oxidation number of MoO ₃ was measured by RBS (Rutherford Backscattering Analysis).

(Comparative Example 3)
As the interface forming layer 10, a mirrortron sputtering apparatus manufactured by Choshu Industry Co., Ltd. was used, except that an IZO (Zn ratio in metal element: 20 atomic%, In ratio: 80 atomic%) film was formed at 4 nm. The organic EL element 1 of Comparative Example 3 was produced in the same manner as in Example 1.

<Measurement of light emission characteristics>
A voltage is applied to the organic EL elements of Examples and Comparative Examples using a "2400 type source meter" manufactured by Caseley Co., Ltd. to measure the current density, and "LS-100" manufactured by Konica Minolta Co., Ltd. The brightness was measured using. The result of the luminance-voltage (LV) characteristic is shown in FIG. 2, and the result of the current density-voltage (JV) characteristic is shown in FIG.

As shown in the luminance-voltage characteristics and current density-voltage characteristics of each element shown in FIGS. 2 and 3, even when zinc oxide (interfacing layer 10) is inserted between the hole injection layer 9 and the anode 11. It can be seen that there is almost no change in the characteristics.
On the other hand, in Comparative Example 3 in which IZO was formed by mirrortron sputtering, damage to the organic layer due to sputtering was unavoidably increased.

<Storage life test>
The organic EL elements of Examples and Comparative Examples were stored at room temperature and humidity, and 30 days and 90 days after the storage life test was started (0 days passed), light emitting surface images of the organic EL elements were taken. .. In this test, the evaluation was performed by turning on the organic EL element only when the light emitting surface image was acquired. The light emitting surface image is shown in FIG. Further, FIG. 5 shows the ratio of the light emitting area after 30 days and 90 days when the light emitting area after 0 days is 100%.

As shown in FIGS. 4 and 5, in both Examples and Comparative Examples, the non-light emitting portion increases from the lateral direction of the drawing in which the interface between the Al electrode as the anode and the organic layer is exposed, and the light emitting surface deteriorates. In the case of an unsealed and atmospheric environment, in the case of an inverted organic EL element, oxygen and moisture invade from the interface between the Al electrode and the hole injection layer, and the Al interface is oxidized, so that holes cannot be injected. Because.

In Comparative Example 1 in which the interface-forming layer was not formed, the deterioration of the light emitting surface was large, whereas in Examples 1 and 2 in which the interface-forming layer containing zinc oxide as a main component was formed, the deterioration of the light emitting surface was large. It is suppressed. It is considered that this is because the ZnO ultrathin film suppresses the oxidation of the Al interface by improving the adhesion between the organic layer and the Al interface.

Further, Comparative Example 3 in which IZO, which is an oxide containing zinc, was formed, and Comparative Example 2 in which MoO ₃ was formed were deteriorated more than Comparative Example 1 in which the interface forming layer was not formed. It is presumed that the interface-forming layer containing zinc oxide as a main component is effective in improving the adhesion.

The cambium of the present invention is used for laminating between a hole injection layer made of an organic substance and an anode made of a metal, and can be used for an organic EL device or the like.

1: Organic EL (electroluminescence) element 2: Substrate 3: Anode 4: Inorganic electron injection layer 5: Organic electron injection layer 6: Electron transport layer 7: Light emitting layer 8: Hole transport layer 9: Hole injection layer 10: Interface forming layer 11: Anode

Claims (6)

An interface-forming layer laminated between a hole injection layer made of an organic substance and an anode made of a metal, wherein 50 atomic% or more of the metal element is made of a metal oxide which is a zinc element. The interface cambium according to claim 1, wherein the metal oxide has less than 1 oxygen element with respect to 1 zinc element. The cambium according to claim 1 or 2, wherein the average thickness is 1 to 30 nm. A substrate, a cathode, a light emitting layer, a hole injection layer, and an anode are provided in this order.
An organic electroluminescence device, which comprises the interface-forming layer according to any one of claims 1 to 3 between the hole injection layer and the anode. A display device comprising the organic electroluminescence device according to claim 4. A lighting device comprising the organic electroluminescence device according to claim 4.