KR20170008683A - Organic electroluminescence element - Google Patents

Abstract

The present invention relates to an organic electroluminescent element which comprises a positive electrode, a negative electrode, and a light emitting layer provided between the positive electrode and the negative electrode. The organic electroluminescent element comprises a first layer made of only sodium fluoride in contact with the light emitting layer, between the positive electrode and the negative electrode, a second layer made of only alkali metal or alkaline earth metal in contact with the first layer, and a third layer including an organic electron transporting material in contact with the second layer. The organic electroluminescent element which has excellent stability in a driving voltage and current efficiency at high temperatures can be provided.

Description

[0001] ORGANIC ELECTROLUMINESCENCE ELEMENT [0002]

The present invention relates to an organic electroluminescence element (referred to as " organic EL element " in this specification).

In organic EL devices, stability of the driving voltage and stability of the current efficiency are required. For example, Patent Document 1 discloses an organic EL device having a light emitting layer, a layer formed only of sodium fluoride in contact with the light emitting layer, and an electron injecting layer composed only of basscuproine and barium in contact with the layer made of only sodium fluoride Lt; / RTI >

Japanese Patent Application Laid-Open No. 2013-033872

However, when the organic EL device is stored in a high temperature environment, the stability of the driving voltage and the stability of the current efficiency are not necessarily sufficient.

Accordingly, an object of the present invention is to provide an organic EL device excellent in stability of a driving voltage and stability of a current efficiency when stored under a high-temperature environment.

The present invention provides the following [1] to [4].

[1] An organic EL device having a positive electrode and a negative electrode, and a light emitting layer provided between the positive electrode and the corresponding negative electrode,

A first layer made of only sodium fluoride in contact with the light emitting layer and a second layer made of only an alkali metal or an alkaline earth metal in contact with the first layer and an organic electron transporting material in contact with the second layer, And a third layer.

[2] The organic EL device according to [1], wherein the alkali metal or alkaline earth metal contained in the second layer is barium, sodium or potassium.

[3] The organic EL device according to [1] or [2], wherein the thickness of the second layer is 0.1 nm to 20 nm.

[4] The organic EL device according to [3], wherein the thickness of the first layer is 0.1 nm to 10 nm and the thickness of the third layer is 1 nm to 1000 nm.

The organic EL device of the present invention is excellent in the stability of the driving voltage and the stability of the current efficiency when stored in a high temperature environment.

1 is a schematic diagram showing a configuration of an organic EL device according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Identical elements are numbered the same. Duplicate description will be omitted. The dimensional ratios in the drawings do not necessarily coincide with those described.

1, the organic EL device includes an anode 2, a hole injecting layer 3, a hole transporting layer 4, a light emitting layer 5, a first layer 6a, A second layer 6b, a third layer 6c, an electron injection layer 7, and a cathode 8 are provided in this order. The organic EL element is used, for example, in a curved or planar illumination device (for example, a flat light source used as a light source of a scanner), a display device.

First, the substrate 1, the anode 2, the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the electron injection layer 7, and the cathode 8 will be described.

≪ Substrate (1) >

In the substrate 1, a substrate which does not chemically change in the manufacturing process of an organic EL element is usually used. As the substrate 1, for example, a rigid substrate such as a glass substrate or a silicon substrate; A flexible substrate such as a plastic substrate, a polymer film, and the like. By using the flexible substrate, the flexible organic EL device as a whole can be obtained. In the substrate 1, an electrode and a driver circuit for driving the organic EL element may be formed in advance.

≪ anode (2) >

For the anode 2, a film usually having a low electrical resistance is used. At least one of the anode 2 and the cathode 8 is usually transparent. For example, in the bottom emission organic EL device, the anode 2 disposed on the substrate 1 side is transparent and has a high transmittance to light in the visible light region.

As the material of the anode 2, for example, a metal oxide having conductivity, a metal, a polyaniline or a derivative thereof, a polythiophene or a derivative thereof is used, the transmittance is good and the patterning is easy, Tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO); Gold, platinum, silver, copper, aluminum or alloys containing these metals are preferable, and ITO, IZO and tin oxide are more preferable.

When the light is extracted from the cathode 8 side, the anode 2 is made of a material that reflects light from the light emitting layer 5 toward the cathode 8 (for example, a metal, a metal oxide, a metal Sulfide) is preferable. As the anode 2, for example, a metal film having a thickness capable of reflecting light is used.

The anode 2 can be formed by, for example, a vacuum evaporation method, a sputtering method, an ion plating method, or a plating method.

The thickness of the anode 2 can be determined in consideration of light transmittance and electrical conductivity, and is usually 10 nm to 10 탆, preferably 20 nm to 1 탆, and more preferably 50 nm to 500 nm.

≪ Hole injection layer (3) >

The hole injection layer (3) is a layer having a function of improving the hole injection efficiency from the anode (2). Examples of the hole injection material constituting the hole injection layer 3 include oxides such as vanadium oxide, molybdenum oxide, ruthenium oxide and aluminum oxide; And polythiophene derivatives such as phenylamine compounds, starburst amine compounds, phthalocyanine compounds, amorphous carbon, polyaniline, and polyethylene dioxythiophene (PEDOT).

As the hole injecting material, a known charge transporting material and an electron-accepting material may be used in combination. The charge transporting material is a hole transporting material and an electron transporting material to be described later.

As the electron-accepting material, a heteropoly acid compound, an arylsulfonic acid, or a combination thereof is preferable.

The heteropoly acid compound refers to a heteropolyacid compound which is represented by a chemical structure of Keggin type or Dawson type and has a structure in which a hetero atom is located at the center of a molecule and an isopoly acid which is an oxygen acid such as vanadium, molybdenum, tungsten, Is a polyacid formed by condensation of an oxygen atom of an element. Examples of the oxygen acid of the hetero-element include oxygen, such as silicon, phosphorus or arsenic.

As the heteropoly acid compound, for example, molybdic acid, silicomolybdic acid, tungstic acid, tungstomolybdic acid, and silicotungstic acid can be given.

Examples of the arylsulfonic acid include benzenesulfonic acid, tosylic acid, p-styrenesulfonic acid, 2-naphthalenesulfonic acid, 4-hydroxybenzenesulfonic acid, 5 -sulfosalicylic acid, p-dodecylbenzenesulfonic acid, Dodecylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dibutylnaphthalenesulfonic acid, dibutylnaphthalenesulfonic acid, 6,7-dibutyl-2-naphthalenesulfonic acid, dodecylnaphthalenesulfonic acid, 3-dodecyl-2-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, Hexyl-2-naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, 2,7-dinonyl-4-naphthalenesulfonic acid, 2-octylnaphthalenesulfonic acid, Naphthalene sulfonic acid, dinonylnaphthalene disulfonic acid and 2,7-dinonyl-4,5-naphthalene disulfonic acid.

The hole injecting layer 3 can be formed by a coating method using a coating liquid containing, for example, a hole injecting material. The solvent used for the coating liquid may be any one which dissolves the hole injecting material, for example, chlorinated solvents such as chloroform, water, methylene chloride, and dichloroethane; Ether solvents such as tetrahydrofuran; Aromatic hydrocarbon solvents such as toluene and xylene; Ketone solvents such as acetone and methyl ethyl ketone; And ester solvents such as ethyl acetate, butyl acetate, and ethyl cellosolve acetate.

Examples of the coating method include a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a dip coating method, a spray coating method, A printing method, an offset printing method, and an inkjet printing method. The hole injection layer 3 can be formed by applying a coating liquid onto the anode 2 using these coating methods.

Further, the hole injection layer 3 may be formed by a vacuum deposition method. The hole injection layer 3 made of only a metal oxide may be formed by a sputtering method or an ion plating method.

The thickness of the hole injection layer 3 is determined in consideration of the desired characteristics, and is usually 1 nm to 1 탆, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm.

≪ Hole transport layer (4) >

The hole transport layer 4 is formed on the side of the hole transport layer 4 which faces the anode 2 side (the hole injection layer 3 in Fig. 1) or the hole transport layer 4 which is closer to the anode 2 Is a layer having a function of improving hole injection from the region to the light emitting layer (5).

Examples of the hole transporting material constituting the hole transporting layer 4 include polyvinylcarbazole and derivatives thereof, polysilane and derivatives thereof, polysiloxane and derivatives thereof having an aromatic amine structure in the side chain or main chain, pyrazoline and derivatives thereof, Polyamines and derivatives thereof, arylamine and derivatives thereof, stilbene and derivatives thereof, triphenyldiamine and derivatives thereof, polyaniline and derivatives thereof, polythiophene and derivatives thereof, polyarylamine and derivatives thereof, polypyrrole and derivatives thereof, And derivatives thereof, poly (2,5-thienylenevinylene) and derivatives thereof; A hole transporting material described in Japanese Patent Application Laid-Open No. 144752/1994, and polyvinylcarbazole and derivatives thereof, polysilane and derivatives thereof, and polysiloxane and derivatives thereof having an aromatic amine in the side chain or main chain are preferable. In the case of a hole transporting material having a low molecular weight, it is preferable that the hole transporting material is dispersed in a polymer binder.

The hole transporting layer 4 can be formed from, for example, a mixed solution with a polymer binder in a hole transporting material having a low molecular weight, and from a solution in a hole transporting material having a high molecular weight.

The solvent used when the hole transport layer 4 is formed from a solution is not particularly limited as long as it dissolves the hole transport material, and examples thereof include chlorinated solvents such as chloroform, methylene chloride, and dichloroethane; Ether solvents such as tetrahydrofuran; Aromatic hydrocarbon solvents such as toluene and xylene; Ketone solvents such as acetone and methyl ethyl ketone; And ester solvents such as ethyl acetate, butyl acetate, and ethyl cellosolve acetate.

When the hole transport layer 4 is formed from a solution, the same coating method as that for forming the hole injection layer can be used.

The polymer binder includes, for example, a compound which does not extremely inhibit charge transport and is weakly absorbed by visible light, and examples thereof include polycarbonate, polyacrylate, polymethyl acrylate, polymethyl methacrylate, polystyrene, Polyvinyl chloride, and polysiloxane are preferable.

The thickness of the hole transport layer 4 is determined in consideration of the driving voltage and the light emitting efficiency, and is usually 1 nm to 1 탆, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm.

≪ Light-emitting layer (5) >

The light-emitting layer 5 usually includes an organic compound that emits fluorescence and / or phosphorescence, or a corresponding organic compound and a dopant that assists the organic compound. The dopant is added, for example, in order to improve the luminous efficiency or change the emission wavelength. Since the organic compound is excellent in solubility, it is preferably a polymer compound and more preferably a polymer compound having a number average molecular weight of 10 ³ to 10 ⁸ in terms of polystyrene. Examples of the light-emitting material constituting the light-emitting layer 5 include a dye-based light-emitting material, a metal complex-based light-emitting material, and a polymer-based light-emitting material.

Examples of the dye-based light emitting material include cyclopentamine and derivatives thereof, tetraphenylbutadiene and derivatives thereof, triphenylamine and derivatives thereof, oxadiazole and derivatives thereof, pyrazoloquinoline and derivatives thereof, distyrylbenzene and derivatives thereof , Distyrylarylene and derivatives thereof, pyrrole and derivatives thereof, thiophene compounds, pyridine compounds, perinone and derivatives thereof, perylene and derivatives thereof, oligothiophene and derivatives thereof, oxadiazole dimer, pyrazoline dimer , Quinacridone and its derivatives, coumarin and its derivatives.

Examples of the metal complex-based light emitting material include a rare-earth metal such as Tb, Eu, and Dy or a metal such as Al, Zn, Be, Pt, and Ir in a central metal, and also oxadiazole, thiadiazole, phenylpyridine, phenyl A benzimidazole, a quinoline structure, and the like can be given, and metal complexes having luminescence from triplet excited states such as iridium complexes and platinum complexes; An aluminum quinolinol complex, a benzoquinolinol beryllium complex, a benzoxazolyl zinc complex, a benzothiazole zinc complex, an azomethyl zinc complex, a porphyrin zinc complex, and a phenanthroline euram complex are preferable.

Examples of the polymeric light emitting material include polyparaphenylenevinylene and derivatives thereof, polythiophene and derivatives thereof, polyparaphenylene and derivatives thereof, polysilane and derivatives thereof, polyacetylene and derivatives thereof, polyfluorene and derivatives thereof, Derivatives thereof, polyvinylcarbazole and derivatives thereof; A dye-based light-emitting material or a material obtained by polymerizing a metal complex-based light-emitting material.

Examples of the dopant include rubrene and its derivatives, squarylium and its derivatives, tetracene and its derivatives, pyrazolone and its derivatives, decacyclene, and phenoxazone.

The light emitting layer 5 can be formed by a coating method, a vacuum evaporation method, a transfer method, etc. in which a solution containing a light emitting material is applied on the hole transport layer 4. Among these, since it is easy to manufacture the organic EL device, the light emitting layer 5 is preferably formed by a coating method. As the solvent used for the solution containing the light emitting material, for example, the solvent exemplified as the solvent used in the coating liquid for forming the hole injection layer 3 can be mentioned.

For forming the light emitting layer by the coating method, the same coating method as the formation of the hole injection layer can be used. In the case of a low-molecular compound in which the luminescent material exhibits sublimation properties, besides the vacuum evaporation method, laser or friction transfer or thermal transfer can be used.

The thickness of the light emitting layer 5 is usually 2 nm to 200 nm.

≪ Electron injection layer 7 >

The electron injection layer 7 is a layer having a function of lowering the energy barrier of electron injection at the interface with the cathode.

Examples of the electron injecting material used for the electron injecting layer 7 include organic electron injecting materials and inorganic electron donating materials.

The organic electron injecting material includes, for example, an organic metal complex. The organometallic complex contains, for example, at least one of an alkali metal ion, an alkaline earth metal ion and a rare earth metal ion as a metal ion, and also includes, as ligands, quinolinol, benzoquinolinol, But are not limited to, dicumyl peroxide, dicumyl peroxide, dicumyl peroxide, dicumyl peroxide, dicumyl peroxide, dicumyl peroxide, dicumyl peroxide, dicyclohexylcarbodiimide, dicumyl peroxide, Fluoroborane, bipyridyl, phenanthroline, phthalocyanine, porphyrin, cyclopentadiene,? -Diketone, azomethine and derivatives thereof.

Examples of inorganic electron donating materials include metals such as Ba, Li, Na, K, Rb, Cs, Fr, Mg, Ca, Sr, Ra and Be, metal salts thereof, , And a metal is preferable, and Ba, Li, Cs, Mg, and Ca are more preferable.

The electron injection layer 7 can be formed by the same method as that of the hole injection layer 3.

The thickness of the electron injection layer 7 is determined in consideration of the driving voltage and the luminous efficiency, and is usually 0.01 nm to 1 탆, preferably 0.02 nm to 500 nm, and more preferably 0.05 nm to 100 nm.

<Cathode>

It is preferable that the material of the cathode 8 is a material having a small work function and easy injection of electrons into the first layer 6a, the second layer 6b and the third layer 6c and also having a high electric conductivity. It is preferable that the material of the cathode 8 is a material having high visible light reflectivity so as to reflect light from the light emitting layer 5 from the cathode 8 to the anode 2 side in the case of taking out light from the anode 2 side .

Examples of the material of the cathode 8 include an alkali metal, an alkaline earth metal, a transition metal and a Group 13 metal of the periodic table. Examples of the material of the cathode 8 include lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, At least one metal selected from the group consisting of gold, silver, platinum, copper, manganese, and gold; at least one metal selected from the group consisting of gold, silver, scandium, vanadium, zinc, yttrium, indium, cerium, samarium, europium, terbium, Titanium, cobalt, nickel, and tungsten, or a graphite or graphite intercalation compound. In this specification, magnesium is contained in an alkaline earth metal.

Examples of the alloys include magnesium-silver alloys, magnesium-indium alloys, magnesium-aluminum alloys, indium-silver alloys, lithium-aluminum alloys, lithium-magnesium alloys, lithium-indium alloys and calcium-aluminum alloys.

As the element for taking out light from the cathode 8 side, a transparent conductive electrode can be used as the cathode 8. Examples of the material of the transparent conductive electrode include conductive metal oxides such as indium oxide, zinc oxide, tin oxide, ITO and IZO; Polyaniline and derivatives thereof, polythiophene and derivatives thereof, and the like.

The cathode 8 can be formed by, for example, a vacuum deposition method, a sputtering method, and a lamination method in which a metal thin film is thermally bonded.

The thickness of the cathode 8 is determined in consideration of electrical conductivity and durability, and is usually 10 nm to 10 탆, preferably 20 nm to 1 탆, and more preferably 50 nm to 500 nm.

Next, the first layer 6a, the second layer 6b and the third layer 6c will be described.

&Lt; First Layer (6a) >

The first layer 6a is a layer formed only of sodium fluoride in contact with the light emitting layer 5 and a layer between the cathode 8 and the light emitting layer 5. [ The purity of sodium fluoride is preferably 95% by weight or more, more preferably 98% by weight or more, further preferably 99% by weight or more, and particularly preferably 99.9% by weight or more.

The first layer 6a can be formed by, for example, vacuum deposition, coating, or transfer.

The thickness of the first layer 6a is preferably from 0.1 nm to 10 nm, more preferably from 2.0 nm to 8.0 nm, and still more preferably from 3.0 nm to 6.0 nm because the lifetime and drive voltage of the organic EL device are excellent. Nm.

&Lt; Second Layer (6b) >

The second layer 6b is a layer made of only alkali metal or alkaline earth metal in contact with the first layer 6a. The purity of the alkali metal or alkaline earth metal is preferably 95% by mass or more, more preferably 98% by mass or more, further preferably 99% by mass or more, and particularly preferably 99.9% by mass or more.

The alkali metal or alkaline earth metal contained in the second layer 6b is preferably barium, sodium or potassium, more preferably barium, from the viewpoint of reducibility.

The alkali metal or alkaline earth metal contained in the second layer 6b is preferably a metal having a work function lower than 2.8 eV and more preferably a metal having a work function of 2.2 eV to 2.6 eV to be.

The work function of the alkali metal is 2.93 eV for lithium, 2.36 eV for sodium, 2.28 eV for potassium, 2.16 eV for rubidium and 1.95 eV for cesium. The work function of the alkaline earth metal is 3.70 eV for magnesium, 2.9 eV for calcium, and 2.0 eV to 2.5 eV for strontium.

The thickness of the second layer 6b is usually 0.1 to 20 nm, preferably 0.5 to 10 nm, and more preferably 1 to 8 nm.

&Lt; Third Layer (6c) >

The third layer 6c is a layer containing an organic electron transporting material in contact with the second layer 6b.

As the organic electron transporting material, an organic compound of a known electron transporting material can be used, and for example, a compound having a condensed aryl ring such as naphthalene or anthracene and derivatives thereof; Styryl-based aromatic ring derivatives such as 4,4-bis (diphenylethenyl) biphenyl; There may be mentioned perylene and its derivatives, perinone and its derivatives, coumarin and its derivatives, naphthalimide and its derivatives, anthraquinone, naphthoquinone, diphenoquinone, anthraquinodimethane and tetracyanoanthraquinodimethane. Quinone derivatives; Oxides and derivatives thereof, carbazole and derivatives thereof, and indole and derivatives thereof; Quinolinol complexes such as tris (8-quinolinolate) and aluminum (III); A hydroxyazole complex such as a hydroxyphenyloxazole complex; Azomethine complexes, tropolone metal complexes and flavonol metal complexes; A compound containing a heteroaryl ring having electron-accepting nitrogen.

The electron-accepting nitrogen means a nitrogen atom forming a multiple bond with adjacent atoms.

Examples of the compound containing a heteroaryl ring having electron-accepting nitrogen include benzimidazole and its derivatives, benzothiazole and its derivatives, oxadiazole and its derivatives, thiadiazole and its derivatives, triazole and its derivatives , Pyridine and derivatives thereof, pyrazine and derivatives thereof, phenanthroline and derivatives thereof, quinoxaline and derivatives thereof, quinoline and derivatives thereof, benzoquinoline and derivatives thereof, oligopyridines and derivatives thereof such as bipyridines and terpyridines, And derivatives thereof, and naphthyridine and derivatives thereof, phenanthroline and derivatives thereof.

As the organic electron transporting material, a material having a lowest through-orbit (LUMO) of 3.0 eV or less is preferable, and a material having 2.0 eV to 2.8 eV is more preferable.

The third layer 6c may comprise only an organic electron transporting material, but may include a material other than the organic electron transporting material. When the third layer 6c includes a material other than the organic electron transporting material, the content of the other material may be 0.1 to 100 parts by volume, preferably 0.1 to 30 parts by volume, for 100 parts by volume of the organic electron transporting material , And 0.1 to 10 parts by volume. For example, the organic electron transporting material may be used in combination with the inorganic electron donating material. When the third layer 6c comprises an inorganic electron donor, the content of the inorganic electron donor is preferably 0.1 to 100 parts by volume, more preferably 0.1 to 30 parts by volume, per 100 parts by volume of the organic electron transporting material, 0.1 to 10 parts by volume is more preferable.

When a low molecular weight organic electron transporting material is used, the third layer 6c can be formed from a vacuum deposition method, a solution, or a molten state. When a high molecular weight organic electron transporting material is used, can do. When the third layer 6c is formed from a solution or a molten state, a polymer binder may be used in combination.

The thickness of the third layer 6c is usually 1 nm to 1000 nm, preferably 2 nm to 500 nm, and more preferably 3 nm to 200 nm.

&Lt; Relation between the first layer 6a, the second layer 6b and the third layer 6c >

In the organic EL device of the present invention, the thicknesses of the first layer 6a, the second layer 6b and the third layer 6c are set so that when the thickness of the first layer 6a is 1, 6b is preferably 0.1 to 5.0, more preferably 0.2 to 2.0, and the thickness of the third layer 6c is preferably 0.1 to 100, more preferably 0.5 to 50. [

The organic EL device of the present invention is characterized in that the anode 2, the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the first layer 6a, the second layer 6b ), A third layer 6c, an electron injection layer 7, and a cathode 8 in this order.

<Others>

The constitution of the organic EL device of the present invention is not limited to the constitution shown in Fig. 1, but may be constituted of the following a) to f), for example. Here, for convenience, the first layer, the second layer and the third layer are all referred to as multi-layered electron-transporting layers.

a) anode / hole injecting layer / light emitting layer / multilayer electron transporting layer / cathode

b) anode / hole injecting layer / hole transporting layer / light emitting layer / multilayer electron transporting layer / cathode

c) anode / light emitting layer / multilayer electron transport layer / cathode

d) anode / hole injecting layer / light emitting layer / multilayer electron transporting layer / electron injecting layer / cathode

e) anode / hole injecting layer / hole transporting layer / light emitting layer / multilayer electron transporting layer / electron injecting layer / cathode

f) anode / light emitting layer / multilayer electron transport layer / electron injection layer / cathode

(The symbol &quot; / &quot; means that the layers on both sides of the symbol &quot; / &quot;

When any one of the first to third layers has a function of blocking the transport of holes, the layer may be referred to as a hole blocking layer. This function can be confirmed by, for example, fabricating an organic EL element in which only a hole current flows and reducing the measured current value.

In addition, when the hole injecting layer and / or the hole transporting layer have a function of blocking electrons from being transported in a) and b), these layers may be referred to as an electron blocking layer. The function can be confirmed from a decrease in the measured current value by manufacturing an organic EL element in which only an electron current flows, for example. In addition to the hole injection layer and / or the hole transport layer, an electronic block layer may be provided between the anode and the light emitting layer.

In any one of the structures a) to f), when the laminate disposed between the anode and the cathode is referred to as a &quot; laminated structure A &quot;, the organic EL device of the present invention has the layer structure 2 Layer light-emitting organic EL element). The constitution of the two laminated structures A may be the same or different.

g) anode / laminated structure A / charge generation layer / laminated structure A / cathode

Here, the charge generation layer is a layer that generates holes and electrons by applying an electric field. Examples of the material used for the charge generation layer include vanadium oxide, ITO, and molybdenum oxide.

The layered structure A / charge generation layer &quot; is referred to as a &quot; layered structure B &quot;, the organic EL element of the present invention may be a layer structure (three or more layered organic EL elements)

h) anode / laminated structure B / laminated structure A / cathode

Here, the laminated structure B may have a plurality of laminated structures which are the same or different.

Alternatively, a plurality of light emitting layers may be directly laminated without providing a charge generating layer.

In the organic EL device of the present invention, the materials used for the respective layers described above may be used singly or two or more of them may be used in combination. In the organic EL device of the present invention, the anode, the hole injecting layer, the hole transporting layer, the light emitting layer, the electron injecting layer, and the cathode may be a single layer or a plurality of layers.

In the organic EL device of the present invention, not only the above-described anode may be disposed on the substrate side, but also the cathode may be disposed on the substrate side. In this case, for example, when the organic EL devices having the layer structures a) to h) are formed on a substrate, the respective layers may be laminated on the substrate in order from the cathode.

[Example]

Hereinafter, the present invention will be described in detail based on examples and comparative examples, but the present invention is not limited to the following examples.

&Lt; Example 1 >

1, the anode 2, the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the first layer 6a, the second layer 6b, A third layer 6c, an electron injecting layer 7 and a cathode 8 are laminated in this order to form an organic EL device and sealed with glass to form a glass sealing organic EL element Device 1 &quot;).

An ITO thin film was formed as a positive electrode on a glass substrate in a predetermined pattern. The ITO thin film was formed so as to have a thickness of 45 nm by a sputtering method. The glass substrate on which the ITO thin film was formed was ultrasonically cleaned with an organic solvent, an alkaline detergent and ultrapure water, and was then brazed with an organic solvent for 10 minutes and dried. Subsequently, ultraviolet ozone treatment was performed for about 15 minutes on the surface of the ITO thin film formed using the ultraviolet ozone (UV-O ₃ ) apparatus.

A hole injection material in combination with a charge transporting material and an electron-accepting material was applied to the ITO thin film by a spin coating method to form a film having a thickness of 35 nm. This film was heated in the air and on a hot plate at 80 DEG C for 4 minutes and further heated at 230 DEG C for 15 minutes to dry to form a hole injection layer.

A high molecular weight hole transporting material and xylene were mixed to obtain a composition for forming a hole transporting layer having a hole transporting material concentration of 0.6 wt%. A composition for forming a hole transport layer was applied on the hole injection layer by a spin coating method to form a film having a thickness of 20 nm. The glass substrate on which the film was formed was heated on a hot plate at 180 캜 for 60 minutes in a nitrogen atmosphere to evaporate the solvent and then naturally cooled to room temperature to form a hole transporting layer.

A fluorene-amine copolymer (polymeric light-emitting material (blue)) and xylene were mixed to obtain a composition for forming a light-emitting layer having a fluorene-amine copolymer concentration of 1.3 wt%. The composition for forming a light emitting layer was applied on the hole transporting layer by spin coating to form a film having a thickness of 50 nm. The glass substrate on which the film was formed was heated on a hot plate at 150 캜 for 10 minutes in a nitrogen atmosphere to evaporate the solvent and then naturally cooled to room temperature to obtain a light emitting layer.

The glass substrate on which the light emitting layer was formed was transferred to the deposition chamber and exhausted until the degree of vacuum in the deposition chamber was 1.0 x 10 &lt; ^-5 &gt; Pa or less. Subsequently, a first layer made of only sodium fluoride was formed by depositing sodium fluoride at a deposition rate of 0.3 Å / s to a thickness of 3 nm on the light emitting layer by a vacuum deposition method.

Next, in the deposition chamber, barium was deposited on the first layer by vacuum evaporation to form a second layer at a deposition rate of 0.5 ANGSTROM / s to a thickness of 2 nm.

Then, in the deposition chamber, an organic electron transporting material was deposited on the second layer by a vacuum deposition method, and a film was formed at a deposition rate of 0.6 ANGSTROM / s so as to have a thickness of 10 nm, thereby forming a third layer.

Next, in the deposition chamber, lithium fluoride was vapor deposited on the third layer by a vacuum deposition method to form a film with a deposition rate of 0.2 ANGSTROM / s so as to have a thickness of 0.5 nm, thereby forming an electron injection layer.

Next, in the metal-only deposition chamber, aluminum was deposited on the electron injecting layer by a vacuum evaporation method to form a film having a thickness of 100 nm, thereby forming a cathode.

Thereafter, the glass substrate on which the negative electrode is formed is transported from the evaporation chamber to the sealing treatment chamber without being exposed to the atmosphere, and the glass substrate is bonded to the sealing glass coated with the ultraviolet ray hardening resin under nitrogen atmosphere, By curing the resin, the organic EL device 1 was produced.

The stability of the driving voltage and current efficiency was evaluated using the organic EL device 1. [

The driving voltage is a voltage when the organic EL element 1 is driven with a constant current of 10 mA / cm 2. The current efficiency is a value when the luminance of the organic EL element 1 is 1000 cd / m &lt; 2 &gt;. For stability, the organic EL device 1 was stored in a storage tank capable of being kept at 80 캜, and the driving voltage and current efficiency after 0 hours, 24 hours, 48 hours, and 168 hours of storage were measured.

The current efficiency (storage time 0 hours) of the organic EL device 1 was 9.9 cd / A, and the driving voltage (storage time 0 hours) was 3.4 V. The current efficiency of the organic EL device 1 was 10.1 cd / A at a storage time of 24 hours, 10.1 cd / A at 48 hours, 10.2 cd / A at 168 hours, and a driving voltage of 3.4 V , 3.4 V at 48 hours, and 3.4 V at 168 hours. The obtained results are shown in Table 1.

&Lt; Comparative Example 1 &

A glass sealing organosilicate glass was produced in the same manner as in Example 1 except that a layer obtained by mixing barium and an organic electron transporting material (the same material as in Example 1) was provided instead of the second and third layers in Example 1, (Hereinafter referred to as &quot; organic EL element C1 &quot;) was fabricated, and the stability of the driving voltage and current efficiency was evaluated.

Specifically, a layer in which barium and an organic electron transporting material are mixed is formed in the same manner as in Example 1 except that barium and an organic electron transporting material Deposited at a deposition rate of 0.05 Å / s and 0.45 Å / s so as to have a thickness of 10 nm by vacuum evaporation at a deposition rate of 10:90 (volume ratio). Otherwise, the same procedure as in Example 1 was carried out.

The current efficiency (storage time 0 hours) of the organic EL element C1 was 9.0 cd / A, and the driving voltage (storage time 0 hours) was 4.2 V. The current efficiency of the organic EL device C1 was 7.3 cd / A at a storage time of 24 hours, 7.1 cd / A at 48 hours, 6.9 cd / A at 168 hours, and 4.9 V 5.0 V at 48 hours, and 5.0 V at 168 hours. The obtained results are shown in Table 1.

&Lt; Comparative Example 2 &

A glass-sealed organic EL element (hereinafter referred to as &quot; organic EL element C2 &quot;) was produced in the same manner as in Example 1 except that the first layer and the second layer were not provided in Example 1, And stability of current efficiency were evaluated.

The current efficiency (storage time 0 hours) of the organic EL device C2 was 8.5 cd / A, and the driving voltage (storage time 0 hours) was 3.7 V. The current efficiency of the organic EL device C1 was 3.8 cd / A at a storage time of 24 hours, 2.4 cd / A at a time of 48 hours, 1.5 cd / A at a time of 168 hours, and 4.0 volts at a storage time of 24 hours , 4.0 V at 48 hours, and 4.2 V at 168 hours. The obtained results are shown in Table 1.

&Lt; Comparative Example 3 &

A glass-sealed organic EL element (hereinafter referred to as &quot; organic EL element C3 &quot;) was fabricated in the same manner as in Example 1 except that the second layer was not provided in Example 1, The stability was evaluated.

The current efficiency (storage time 0 hours) of the organic EL element C3 was 6.6 cd / A, and the driving voltage (storage time 0 hours) was 4.7 V. The current efficiency of the organic EL device C1 was 5.6 cd / A at the storage time of 24 hours, 5.7 cd / A at the storage time of 48 hours, 5.9 cd / A at the storage time of 168 hours, , 5.3 V at 48 hours, and 5.5 V at 168 hours. The obtained results are shown in Table 1.

&Lt; Comparative Example 4 &

A glass-sealed organic EL element (hereinafter referred to as &quot; organic EL element C4 &quot;) was fabricated in the same manner as in Example 1 except that the first layer was not provided in Example 1, The stability was evaluated.

The current efficiency (storage time 0 hour) of the organic EL device C4 was 1.1 cd / A, and the driving voltage (storage time 0 hour) was 5.9 V. The current efficiency of the organic EL device C1 was 0.5 cd / A at the storage time of 24 hours, 0.5 cd / A at the 48 hours, 0.5 cd / A at the 168 hours, and 6.0 volts at the storage time of 24 hours 6.0 V at 48 hours, and 6.1 V at 168 hours. The obtained results are shown in Table 1.

1: substrate
2: anode
3: Hole injection layer
4: hole transport layer
5: light emitting layer
6a: First layer
6b: Second layer
6c: Third floor
7: electron injection layer
8: cathode

Claims (4)

An organic electroluminescent device having a positive electrode and a negative electrode, and a light emitting layer provided between the positive electrode and the negative electrode,
A first layer made of only sodium fluoride in contact with the light emitting layer and a second layer made of only an alkali metal or an alkaline earth metal in contact with the first layer and an organic electron transporting material in contact with the second layer, And a third layer on the organic electroluminescent device. The organic electro luminescence device according to claim 1, wherein the alkali metal or alkaline earth metal contained in the second layer is barium, sodium or potassium. The organic electro-luminescence device according to claim 1 or 2, wherein the thickness of the second layer is 0.1 nm to 20 nm. The organic electro-luminescence device according to claim 3, wherein the thickness of the first layer is 0.1 nm to 10 nm and the thickness of the third layer is 1 nm to 1000 nm.

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