TWI692892B - Organic el element - Google Patents

Abstract

The present invention provides an organic EL element capable of further improving driving stability. One embodiment of the organic EL element (1) contains an anode (E1), a cathode (E2) and a light emitting layer provides between the anode and the cathode, and contains a multilayer-type electron transport layer (14) provided between the light emitting layer and the cathode layer. The multilayer-type electron transport layer (14) contains: an electron transport layer (14a) which contains an electron transporting material, and a light-emitting-side mixture layer (14b) which is provided between the electron transport layer and the light emitting layer and contacts with the light emitting layer and is thinner than the electron transport layer. The light-emitting-side mixture layer contains both an electron transporting material and an organic metal chelate compound.

Description

Organic EL element

The present invention relates to an organic EL device.

In organic electroluminescent devices (hereinafter, sometimes referred to as "organic EL devices"), it is required to increase the life of the device, that is, to improve drive stability. For example, the technique described in Patent Document 1 is an organic EL device in which an anode, a light-emitting layer, and a cathode are stacked on a substrate, and a hole blocking layer in contact with the light-emitting layer is provided to improve driving stability.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent No. 4325197

However, in recent years, it has been required to further improve the driving stability of organic EL elements.

Therefore, the object of the present invention is to provide an organic EL device which can further improve the driving stability.

The organic EL device according to one aspect of the present invention has Electrodes, a cathode, and a light-emitting layer disposed between the anode and the cathode, the organic EL element includes a multilayer electron transport layer provided between the light-emitting layer and the cathode, the multilayer electron transport layer having: an electron transport layer, which It contains an electron transport material; and a mixed layer on the light emitting layer side, which is provided between the electron transport layer and the light emitting layer and in contact with the light emitting layer, and is thinner than the electron transport layer; the mixed layer on the light emitting layer side also contains Electron transport materials and organic metal complex compounds.

In the above configuration, it is provided with a multi-layer side electron transport layer having a light emitting layer side mixed layer and an electron transport layer. Furthermore, since the mixed layer on the light emitting layer side provided in contact with the light emitting layer contains an organometallic complex compound in addition to the electron transport material, it is possible to improve driving stability.

In one embodiment, the multi-layer electron transport layer further includes a cathode side mixed layer, which is closer to the cathode side than the electron transport layer and is provided in contact with the electron transport layer. The cathode side mixed layer may also contain an electron transport material And organometallic complex compounds.

The multi-layer electron transport layer of this configuration has a cathode side mixing layer closer to the cathode side than the electron transport layer. Since the cathode-side mixed layer contains an organometallic complex compound in addition to the electron transport material, electron injection from the cathode to the electron transport layer can be made more efficient. As a result, it is possible to reduce the driving voltage.

In one embodiment, the multilayer electron transport layer may further have a metal layer between the light-emitting layer side mixed layer and the electron transport layer. With this, it is possible to reduce the driving voltage.

In one embodiment, the thickness of the mixed layer on the light-emitting layer side may be 2 nm to 20 nm. This is because pinholes are likely to occur when the thickness of the mixed layer on the light emitting layer side is less than 2 nm, and when the thickness of the mixed layer on the light emitting layer side is greater than 20 nm, the thickness of the entire multilayer electron transport layer becomes thicker and the driving voltage becomes higher.

In one embodiment, the organometallic complex compound contained in the mixed layer on the light-emitting layer side may be 8-quinolinol sodium.

According to the present invention, it is possible to provide an organic EL element capable of further improving driving stability.

1, 2‧‧‧ organic EL element

11‧‧‧hole injection layer

12‧‧‧Electric tunnel transmission layer

13‧‧‧luminous layer

14, 14A‧‧‧Multi-layer electron transport layer

14a‧‧‧Electronic transmission layer

14b‧‧‧The first mixed layer (the mixed layer on the light emitting layer side)

14c‧‧‧The second mixed layer (cathode side mixed layer)

14d‧‧‧Metal layer

E1‧‧‧Anode

E2‧‧‧Cathode

P‧‧‧Substrate

FIG. 1 is a diagram schematically showing the structure of an organic EL device according to an embodiment.

FIG. 2 is a diagram schematically showing the structure of an organic EL device of another embodiment.

Hereinafter, the embodiment of the present invention will be described with reference to the drawings. The same symbols are attached to the same elements. Duplicate description is omitted. The size ratio of the drawings may not be consistent with the description.

(First embodiment)

As schematically shown in FIG. 1, the organic EL element 1 of the first embodiment is provided with an anode E1, a hole injection layer 11, a hole transport layer 12, a light emitting layer 13, and a multilayer type on the substrate P in the following order Electron transport layer 14 And cathode E2. The organic EL element 1 can be suitably used in a planar or planar lighting device (for example, a planar light source used as a light source of a scanner) and a display device.

First, the substrate P, anode E1, hole injection layer 11, hole transport layer 12, light emitting layer 13, and cathode E2 will be described.

<substrate>

The substrate P is suitable for a substrate that does not cause chemical changes in the manufacturing process of the organic EL element 1, and may be a rigid substrate such as a glass substrate or a silicon substrate, or a flexible substrate such as a plastic substrate or a polymer film. By using a flexible substrate, the entire organic EL element can be made flexible. An electrode and a driving circuit for driving the organic EL element 1 may be formed in advance on the substrate P.

<anode>

For the anode E1 series, a thin film with low resistance can be suitably used. At least one of the anode E1 and the cathode E2 is transparent. For example, an organic EL element of bottom emission type and an anode E1 disposed on the side of the substrate P can be suitably used for those that are transparent and have a high transmittance of light in the visible light region. As the material of the anode E1, a conductive metal oxide film, a metal thin film, or the like can be used.

Specifically, the anode E1 can be made of indium oxide, zinc oxide, tin oxide, indium tin oxide (Indium Tin Oxide: ITO for short), indium zinc oxide (Indium Zinc Oxide: IZO), etc. Thin films; and alloys containing at least one type of gold, platinum, silver, copper, aluminum, or alloys of these metals.

Among these, as the anode E1, a thin film composed of ITO, IZO, and tin oxide can be suitably used in terms of transmittance and ease of patterning. In addition, when taking out light from the cathode E2 side, as the anode E1, it is preferable to use a material that reflects light from the light-emitting layer 13 to the cathode E2 side. As such a material, a work function of 3.0 eV or more is used. Metals, metal oxides, and metal sulfides are preferred. For example, a metal thin film having a thickness that reflects light can be used.

Examples of the method of forming the anode E1 include a vacuum evaporation method, a sputtering method, an ion spraying method, and a plating method. As the anode E1, a transparent conductive film of an organic substance such as polyaniline or its derivative, polythiophene or its derivative, or the like can also be used.

The thickness of the anode E1 can be appropriately determined in consideration of light transmittance, electrical conductivity, and the like. The thickness of the anode E1 is, for example, 10 nm to 10 μm, preferably 20 nm to 1 μm, and more preferably 50 nm to 500 nm.

<hole injection layer>

The hole injection layer 11 is a functional layer having a function of improving hole injection efficiency from the anode E1. Examples of the hole injection material constituting the hole injection layer 11 include oxides such as vanadium oxide, molybdenum oxide, ruthenium oxide, and alumina, aniline compounds, starburst type amine compounds, and phthalocyanine Green compounds, amorphous carbon, polyaniline, and polythiophene derivatives such as polyethylene dioxythiophene (PEDOT).

The previously known organic materials with charge transport properties can be used as hole injection layer materials by combining them with electron-accepting materials.

As an electron-accepting material, a heteropoly acid compound and arylsulfonic acid can be suitably used.

Heteropoly acid compounds are homopolymeric acids represented by Keggin-type or Dawson-type chemical structures that have heteroatoms at the center of the molecule and are oxygen-containing acids such as vanadium (V), molybdenum (Mo), and tungsten (W). (isopolyacid), polyacid formed by condensation of oxoacids of different elements. As the oxo acid of the different element, oxo acid of silicon (Si), phosphorus (P), arsenic (As) is mainly mentioned. Specific examples of the heteropoly acid compound include phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, phosphotungstic molybdic acid, and silicotungstic acid.

Examples of the arylsulfonic acid include benzenesulfonic acid, p-toluenesulfonic acid (tosic acid), p-styrenesulfonic acid, 2-naphthalenesulfonic acid, 4-hydroxybenzenesulfonic acid, 5-sulfosalicylic acid, and p-decanesulfonic acid. Diylbenzenesulfonic acid, dihexylbenzenesulfonic acid, 2,5-dihexylbenzenesulfonic acid, dibutylnaphthalenesulfonic acid, 6,7-dibutyl-2-naphthalenesulfonic acid, dodecylnaphthalenesulfonic acid, 3-dodecyl-2-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, 4-hexyl-1-naphthalenesulfonic acid, octylnaphthalenesulfonic acid, 2-octyl-1-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, 7 -Hexyl-1-naphthalenesulfonic acid, 6-hexyl-2-naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, 2,7-dinonyl-4-naphthalenesulfonic acid, dinonylnaphthalene disulfonic acid, 2, 7-Dinonyl-4,5-naphthalene disulfonic acid, etc.

The heteropoly acid compound and the aryl sulfonic acid may be mixed and used.

The hole injection layer 11 is formed by, for example, a coating method using a coating solution containing the hole injection material. The solvent of the coating liquid may be one in which the hole injection material is dissolved, and examples thereof include chloroform, water, methylene chloride, dichloroethane and other chlorine-based solvents, tetrahydrofuran and other ether-based solvents, toluene and dichloromethane. Aromatic hydrocarbon-based solvents such as toluene, ketone-based solvents such as acetone and methyl ethyl ketone, ethyl acetate, butyl acetate, ethyl celulose acetic acid Ester-based solvents such as esters.

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, and a spray Coating method, screen printing method, flexographic printing method, lithographic printing method, inkjet printing method, etc. The hole injection layer 11 can be formed by applying one of these coating methods to the aforementioned coating liquid on the substrate P on which the anode E1 is formed.

The hole injection layer 11 can also be formed by vacuum deposition or the like. Furthermore, when the hole injection layer 11 is made of a metal oxide, a sputtering method, an ion sputtering method, or the like can also be used.

The optimal value of the thickness of the hole injection layer 11 differs depending on the material used, and can be appropriately determined in consideration of required characteristics, ease of film formation, and the like. The thickness of the hole injection layer 11 is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm.

<hole transport layer>

The hole transport layer 12 has a layer for improving contact with the interface with the anode E1 side of the hole transport layer 12 (hole injection layer 11 in FIG. 1) or a hole transport layer closer to the anode E1 12 The functional layer of the hole injection function.

Examples of the hole transporting material constituting the hole transport layer 12 include polyvinylcarbazole or its derivatives, polysilane or its derivatives, and polysiloxane having aromatic amines in the side chain or main chain Alkane derivatives, pyrazoline derivatives, aromatic amine derivatives, stilbene derivatives, triphenyldiamine derivatives, polyaniline or its derivatives, polythiophene or its derivatives, polyarylamine or Its derivatives, polypyrrole or its derivatives, poly(p-phenylene vinylene) or its derivatives, or poly(2,5-thienylethylene) or its derivatives, etc. As the hole transport material constituting the hole transport layer 12, the hole transport layer material disclosed in Japanese Patent Laid-Open No. 2012-144722 can also be mentioned.

Among these, as the hole transport material, polyvinyl carbazole or its derivative, polysilane or its derivative, side chain or polysiloxane having aromatic amine compound group in the main chain Derivatives, polyaniline or its derivatives, polythiophene or its derivatives, polyarylamine or its derivatives, poly(p-phenylene vinylene) or its derivatives, or poly(2,5-extended (Thienylethene) or its derivatives, such as polymer hole transport materials, preferably polyvinylcarbazole or its derivatives, polysilane or its derivatives, side chains or in the main chain Polysiloxane derivatives of aromatic amines. When transporting materials with low-molecular holes, it is better to disperse the polymer binder and use it.

As a method of forming the hole transport layer 12, a method for forming a film from a mixed solution of a low molecular hole transport material and a polymer binder, and a method of forming a hole transport material in a polymer can be cited from a solution The method of film formation.

The solvent used to form the film from the solution may be any one that dissolves the hole transport material, and examples thereof include chlorine-based solvents such as chloroform, methylene chloride, and dichloroethane, ether-based solvents such as tetrahydrofuran, toluene, and dichloromethane. Aromatic hydrocarbon-based solvents such as toluene, ketone-based solvents such as acetone and methyl ethyl ketone, and ester-based solvents such as ethyl acetate, butyl acetate, and ethyl celulose acetate.

As a method of forming a film from a solution, a coating method similar to the method already mentioned as a method of forming a hole injection layer by film formation can be mentioned.

As a mixed polymer binder, it is better not to extremely hinder charge transport, but also to use a weaker absorption of visible light. Examples of the polymer binder include polycarbonate, polyacrylate, polymethyl acrylate, polymethyl methacrylate, polystyrene, polyvinylidene chloride, and polysiloxane.

The optimal value of the film thickness of the hole transport layer 12 differs depending on the material used, and is appropriately set so that the driving voltage and the luminous efficiency are appropriate values. The film thickness of the hole transport layer 12 must be at least a thickness that does not generate pinholes. On the other hand, when the thickness is too thick, the driving voltage of the element is too high to be good. Therefore, the film thickness of the hole transport layer 12 is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm.

<luminescent layer>

The light-emitting layer 13 usually contains mainly organic substances emitting fluorescence and/or phosphorescence, or dopants containing the organic substances and auxiliary substances. The dopant is added, for example, to improve luminous efficiency or to change the luminous wavelength. From the viewpoint of solubility, the organic compound is preferably a polymer compound. Based light emitting layer 13 to contain a number average molecular weight in terms of polystyrene of 10 ³ to 10 ⁸ preferably of a polymer compound. Examples of the light-emitting material constituting the light-emitting layer 13 include the following pigment-based light-emitting materials, metal complex-based light-emitting materials, and polymer-based light-emitting materials.

二唑衍生物、吡唑喹啉衍生物、二苯乙烯基苯衍生物、二苯乙烯基伸芳基衍生物、吡咯衍生物、噻 吩環化合物、吡啶環化合物、紫環酮衍生物、苝衍生物、寡聚噻吩衍生物、

二唑二聚物、吡唑啉二聚物、喹吖酮衍生物、香豆素衍生物等。 Examples of the pigment-based light-emitting material include cyclopentamine derivatives, tetraphenylbutadiene derivatives, and triphenylamine derivatives.

Diazole derivatives, pyrazololine derivatives, distyrylbenzene derivatives, distyryl aryl derivatives, pyrrole derivatives, thiophene ring compounds, pyridine ring compounds, violagen derivatives, perylene derivatives , Oligothiophene derivatives,

Diazole dimer, pyrazoline dimer, quinacridone derivative, coumarin derivative, etc.

二唑、噻二唑、苯基吡啶、苯基苯并咪唑、喹啉結構等之金屬錯合物。作為金屬錯合物，例如可舉出銥錯合物、具有來自鉑錯合物等的三重態激發狀態的發光之金屬錯合物、鋁喹啉酚錯合物、苯并喹啉酚鈹錯合物、苯并

唑基鋅錯合物、苯并噻唑基鋅錯合物、偶氮甲基鋅錯合物、卟啉鋅錯合物、啡啉銪錯合物等。 Examples of the metal complex-based light-emitting material include rare earth metals such as Tb, Eu, and Dy in the center metal, or Al, Zn, Be, Pt, Ir, and the like in the ligand.

Metal complexes of diazole, thiadiazole, phenylpyridine, phenylbenzimidazole, quinoline structure, etc. Examples of metal complexes include iridium complexes, luminescent metal complexes having a triplet excited state derived from platinum complexes, aluminum quinolinephenol complexes, and benzoquinoline beryllium complexes. Compound, benzo

Zolyl zinc complex, benzothiazolyl zinc complex, azomethyl zinc complex, porphyrin zinc complex, morpholine europium complex, etc.

Examples of the polymer-based light-emitting material include polyparaphenylene vinyl derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyfusel derivatives, and polyvinyl groups. Carbazole derivatives, materials obtained by polymerizing the above pigment materials or metal complex materials, etc.

二唑衍生物、及該等的聚合物、聚乙烯基咔唑衍生物、聚對苯衍生物、聚茀衍生物等。尤其是高分子材料的聚乙烯基咔唑衍生物、聚對苯衍生物、聚茀衍生物等為佳。作為發出藍色光的材料，亦可舉出在特開2012-144722號公報所揭示之材料。 Among the above-mentioned luminescent materials, as the material that emits blue light, a distyryl arylene derivative,

Diazole derivatives, and such polymers, polyvinylcarbazole derivatives, poly-p-phenylene derivatives, polystilbene derivatives, etc. In particular, polymer materials such as polyvinylcarbazole derivatives, polyparaphenylene derivatives, and polystilbene derivatives are preferred. As the material that emits blue light, the material disclosed in Japanese Patent Laid-Open No. 2012-144722 can also be mentioned.

As a material that emits green light, quinacridone can be cited (quinacridone) derivatives, coumarin derivatives, and their polymers, poly-p-phenylene vinyl derivatives, poly-fusel derivatives, etc. In particular, it is preferably a polyparaphenylene vinylene derivative, a polyfluorene derivative, etc. of a polymer material. As the material that emits green light, the material disclosed in Japanese Patent Laid-Open No. 2012-036388 can also be mentioned.

Examples of the material that emits red light include coumarin derivatives, thiophene ring compounds, and polymers of these, polyparaphenylene vinylene derivatives, polythiophene derivatives, and polystilbene derivatives. In particular, polymer materials such as poly-p-phenylene vinyl derivatives, polythiophene derivatives, and polyfusel derivatives are preferred. As a material that emits red light, the materials disclosed in Japanese Patent Laid-Open No. 2011-105701 can also be mentioned.

酮(phenoxazone)等。 Examples of the dopant material include perylene derivatives, coumarin derivatives, rubrene derivatives, quinacridone derivatives, squalium derivatives, porphyrin derivatives, Styrene-based pigments, thick tetraphenyl derivatives, pyrazolone derivatives, decacycloene, phen

Ketone (phenoxazone) and so on.

Examples of the method for forming the light-emitting layer 13 include a coating method in which a solution containing a light-emitting material is applied to the hole transport layer 12, a vacuum evaporation method, and a transfer method. Among these, from the ease of manufacturing steps, it is preferable to form the light-emitting layer using a coating method. As the solvent of the solution containing the light-emitting material, for example, the solvents mentioned above as the solvent of the coating liquid for forming the aforementioned hole injection layer 11 can be used.

As a method of applying a solution containing a light-emitting material, a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, Bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method, spray coating method, nozzle coating method, gravure printing method, screen printing Method, flexographic printing method, lithographic printing method, reverse printing method, inkjet printing method, etc. From the perspective of pattern formation and easy application of multiple colors, the gravure printing method, screen printing method, flexographic printing method, lithographic printing method, reverse printing method, or inkjet printing method is preferred. For low-molecular compounds showing sublimation, vacuum evaporation method can be used. In addition, by using methods such as laser and friction transfer, thermal transfer, and the like, the light-emitting layer 13 can also be formed only at desired positions.

The thickness of the light-emitting layer 13 is usually about 2 nm to 200 nm.

<cathode>

As the material of the cathode E2, since the work function is small and electrons are easily injected into the multi-layer type electron transport layer 14, a material with high conductivity is preferable. When the light is taken out from the anode E1 side, in order to reflect the light from the light-emitting layer 13 to the anode E1 side through the cathode E2, the material of the cathode E2 is preferably a material having a high visible light reflectivity.

For the cathode E2, for example, alkali metals, alkaline earth metals, transition metals, Group 13 metals of the periodic table, and the like can be used. As the material of the cathode E2, for example, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, aluminum, scandium, vanadium, zinc, yttrium, indium, cerium, samarium, europium, ytterbium, ytterbium Metals; alloys of two or more of the foregoing metals; alloys of one or more of the foregoing metals and one of gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, and tungsten; Or use graphite or graphite interlayer compounds. In this specification, the magnesium series is included in alkaline earth metals. The following description is the same.

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

When forming an element that extracts light from the cathode E2 side, a transparent conductive electrode can be used as the cathode E2, for example, a thin film composed of conductive metal oxides such as indium oxide, zinc oxide, tin oxide, ITO, and IZO can be used ; And thin films composed of conductive organic materials such as polyaniline or its derivatives, polythiophene or its derivatives. The cathode system may have a laminated structure of two or more layers.

The thickness of the cathode E2 can be appropriately set in consideration of conductivity and durability. The thickness of the cathode E2 is, for example, 10 nm to 10 μm, preferably 20 nm to 1 μm, and more preferably 50 nm to 500 nm.

As a method of forming the cathode E2, for example, a vacuum evaporation method, a sputtering method, and a lamination method of thermocompression bonding a metal thin film, etc. can be mentioned.

Next, the multilayer electron transport layer 14 will be described. As shown in FIG. 1, the multi-layer electron transport layer 14 is provided with a first mixed layer (light emitting layer side mixed layer) 14b and a second mixed layer (cathode side mixed layer) 14c on both sides of the electron transport layer 14a. Layered body.

<electron transport layer>

The electron transport layer 14a corresponds to the body of the multilayer electron transport layer 14. The electron transport layer 14a contains an electron transport material. On the other hand, it does not contain the organometallic complex compound contained in the first mixed layer 14b and the second mixed layer 14c described later.

唑錯合物等的羥基唑錯合物、甲亞胺錯合物、環庚三烯酚酮(tropolone)金屬錯合物及黃酮醇金屬錯合物、具有電子接受性氮之雜芳基環之化合物等。 As the electron transport material, a well-known one which is generally used as an electron transport layer can be used. For example, examples of the electron transport material include compounds having condensed aryl rings such as naphthalene and anthracene and their derivatives, and styryl aromatics represented by 4,4-bis(diphenylvinyl)biphenyl. Cyclic derivatives, perylene derivatives, perinone derivatives, coumarin derivatives, naphthalene derivatives, anthraquinone, naphthoquinone, diphenoquinone, anthraquinone dimethane , Quinoline derivatives such as tetracyanoanthraquinone dimethane, phosphorus oxide derivatives, carbazole derivatives, and indole derivatives, quinoline (8-quinolinate), aluminum (III), etc. Phenol complex and hydroxyphenyl

Hydroxazole complexes such as azole complexes, methylimine complexes, tropolone metal complexes and flavonol metal complexes, heteroaryl rings with electron-accepting nitrogen Of compounds.

二唑衍生物、噻二唑衍生物、三唑衍生物、吡啶衍生物、吡

衍生物、啡啉衍生物、喹

啉衍生物、喹啉衍生物、苯并喹啉衍生物、聯吡啶、聯三吡啶等的寡聚吡啶衍生物、喹

啉衍生物、萘啶衍生物、啡啉衍生物等。 The so-called electron-accepting nitrogen refers to a nitrogen atom in which multiple bonds are formed with adjacent atoms. Because the nitrogen atom system has a high electronegativity, multiple bonds also have the property of accepting electrons. Therefore, the heteroaryl ring with an electron-accepting nitrogen has a high electron affinity. As the compound having a heteroaryl ring structure containing such electron-accepting nitrogen, for example, preferred compounds include benzimidazole derivatives, benzthiazole derivatives,

Diazole derivatives, thiadiazole derivatives, triazole derivatives, pyridine derivatives, pyridine

Derivatives, morpholine derivatives, quino

Oligopyridine derivatives, quinoline derivatives, quinoline derivatives, benzoquinoline derivatives, bipyridine, bipyridine, etc.

Porphyrin derivatives, naphthyridine derivatives, morpholine derivatives, etc.

The method for forming the electron transport layer 14a can be a vacuum evaporation method or a film formation from a solution or a molten state when a low-molecular electron transport material is used. When using polymer electron transport materials, it can be cited Film formation from solution or molten state. When performing film formation from a solution or a molten state, a polymer binder may be used together.

<1st mixed layer>

The first mixed layer 14b is provided closer to the light-emitting layer 13 than the electron transport layer 14a and is provided in contact with the light-emitting layer 13. The first mixed layer 14b is also in contact with the electron transport layer 14a. The first mixed layer 14b is a layer containing both the electron transport material and the organometallic complex compound contained in the electron transport layer 14a. The first mixed layer 14b can be a mixture of organometallic complexes in the composition of the electron transport layer 14a Layer of chemical compounds. The electron transport material included in the first mixed layer 14b can be the same as the electron transport material exemplified in the electron transport layer 14a.

唑、羥苯基硫醛、羥基二芳基

二唑、羥基二芳基噻二唑、羥苯基吡啶、羥苯基苯并咪唑、羥基苯并三唑、羥基氟硼烷、聯砒啶(Bipyridyl)、啡啉、酞花青、卟啉、環戊二烯、β-二酮類、甲亞胺類、及該等的衍生物等為佳。 The metal ion contained in the organometallic complex compound preferably contains at least one of alkali metal ions, alkaline earth metal ions, and rare earth metal ions. The coordination system contained in the organometallic complex compound is quinoline phenol, benzoquinoline phenol, acridinol, phenanthridine diol, hydroxyphenyl

Azole, hydroxyphenylthioaldehyde, hydroxydiaryl

Diazole, hydroxydiarylthiadiazole, hydroxyphenylpyridine, hydroxyphenylbenzimidazole, hydroxybenzotriazole, hydroxyfluoroborane, bipyridyl, morpholine, phthalocyanine, porphyrin , Cyclopentadiene, β-diketones, methylimines, and derivatives of these are preferred.

As the organometallic complex compound, for example, any compound of the following formula (1) to formula (16) may be mentioned.

[Chemical 1]

[Chemical 4]

In formula (1) to formula (16), M series represents an alkali metal. Examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium. Among these, lithium, sodium, or cesium is preferred, and lithium or sodium is more preferred.

Each organometallic complex compound represented by formula (1) to formula (16) is bonded to at least one hydrogen atom of carbon atoms constituting a five-membered ring or a six-membered ring, and may also be Alkyl substitution. The alkyl group having 1 to 12 carbon atoms is preferably methyl, ethyl, propyl, or tertiary butyl.

In formulae (1) to (16), as the organometallic complex compound, formula (1), formula (2), formula (4), formula (6), formula (7), or formula (9) Preferably, formula (1), formula (2) or formula (4) is more preferable.

Specific examples of the organometallic complex compound include lithium 8-quinoline phenol, sodium 8-quinoline phenol, potassium 8-quinoline phenol, rubidium 8-quinoline phenol, cesium 8-quinoline phenol, benzene Lithium-8-quinoline phenol lithium, sodium benzo-8-quinoline phenol, potassium benzo-8-quinoline phenol, rubidium benzo-8-quinoline phenol, cesium benzo-8-quinoline phenol, 2 -Methyl-8-quinolinol lithium, 2-methyl-8-quinolinol sodium, 2-methyl-8-quinolinol potassium, 2-methyl-8-quinolinol rubidium and 2-methyl Base-8-quinolinol cesium.

Among the above, as the organometallic complex compound, lithium 8-quinolinol or sodium 8-quinolinol is preferred, and sodium 8-quinolinol is more preferred.

Mixture of electron transport materials and organometallic complex compounds In a proportional example, when the mass of the electron transport material is V1 and the mass of the organometallic complex compound is V2, V1:V2 is preferably 1:99 to 99:1, preferably 5:95 Until 70:30.

An example of the method for forming the first mixed layer 14b is when a low-molecular electron transport material is used, such as vacuum deposition or film formation from a solution or molten state, and when a polymer electron transport material is used, Film formation from solution or molten state. When performing film formation from a solution or a molten state, a polymer binder may be used together. For example, in the vacuum evaporation method, the electron transport material and the organometallic complex compound constituting the first mixed layer 14b may be co-evaporated.

<2nd mixed layer>

Like the first mixed layer 14b, the second mixed layer 14c is a layer containing an electron transport material and an organometallic complex compound. The second mixed layer 14c can be a layer obtained by mixing an organometallic complex compound with the composition of the electron transport layer 14a. The second mixed layer 14c is a layer for improving the efficiency of electron injection from the cathode E2 and functions as an electron injection layer.

The electron transport material contained in the second mixed layer 14c can be provided as the electron transport material exemplified in the description of the electron transport layer 14a. The organometallic complex compound contained in the second mixed layer 14c includes the organometallic complex compound exemplified in the description of the first mixed layer 14b. The electron transport material and the organometallic complex compound contained in the second mixed layer 14c can be the same as the electron transport material and the organometallic complex compound contained in the first mixed layer 14b.

The second mixed layer 14c is the same as the first mixed layer 14b Way. In the second mixed layer 14c, when the mixing ratio of the electron transport material and the organometallic complex compound is set to V3, and the mass of the organometallic complex compound is V4, V3: V4 Examples are 5:95 to 50:50.

The optimal value of the thickness of the multi-layer electron transport layer 14 depends on the layer structure of the multi-layer electron transport layer 14 and the materials used, and the driving voltage and the luminous efficiency may be selected so as to have appropriate values. The thickness of the multi-layer type electron transport layer 14 must be at least a thickness that does not generate pinholes. On the other hand, when it is too thick, the driving voltage of the element is too high to be good. Therefore, the film thickness of the multilayer electron transport layer 14 is, for example, 7 nm to 1 μm.

In such a multilayer electron transport layer 14, the film thickness of the electron transport layer 14a is, for example, 3 nm to 1 μm, the film thickness of the first mixed layer 14 b is, for example, 2 nm to 20 nm, and the film thickness of the second mixed layer 14 c is, for example, 2nm to 20nm. The thickness of the first and second mixed layers 14b and 14c is thinner than the thickness of the electron transport layer 14a. When the first and second mixed layers 14b and 14c are thinner than 2nm, pinholes tend to occur, and when they are thicker than 20nm, the overall thickness of the multilayer electron transport layer 14 tends to become thicker as a result. The driving voltage becomes high.

The multilayer electron transport layer 14 can be obtained by forming the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c on the light-emitting layer 13 in the following order. From the viewpoint of improving manufacturing efficiency, the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c are preferably formed using the same film forming method.

The first mixed layer of the multilayer electron transport layer 14 14b. The electron transport layer 14a and the second mixed layer 14c each have an electron transport material. Therefore, for example, in the electron transport layer composed of the electron transport material and the multilayer electron transport layer, the multilayer electron transport layer 14 corresponds to the interface between the light emitting layer side and the cathode layer side, and is partially doped with organic metal The composition of the compound. Here, "doping" means intentionally mixing two or more different materials.

The electron transport materials of the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c can be the same material, but the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c Electronic transport materials can also be different. At this time, as the electron transport material included in each of the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c, for example, the electron transport material exemplified in the description of the electron transport layer 14a can be used. The first mixed layer 14b and the second mixed layer 14c may not be made of the same material.

The organic EL device 1 is manufactured by forming an anode E1, a hole injection layer 11, a hole transport layer 12, a light-emitting layer 13, a multilayer electron transport layer 14, and a cathode E2 on the substrate P in the following order. The method of forming each component on the substrate P is as described above, and therefore its description is omitted.

The organic EL element 1 includes the multi-layer electron transport layer 14 and the first mixed layer 14b between the light-emitting layer 13 and the electron transport layer 14a. Since the first mixed layer 14b has an organometallic complex compound in addition to the electron transport material, the device life of the organic EL device 1 becomes longer and the drive stability is improved. Xian believes that this is through organometallic complex compounds, which can suppress, for example, the charge caused by the charge The transport layer is deteriorated.

The multilayer electron transport layer 14 has the second mixed layer 14c. Since the second mixed layer 14c has the organometallic complex compound, the electron injection efficiency from the cathode E2 to the electron transport layer 14a can be improved. As a result, the driving voltage can be reduced.

(Second embodiment)

The organic EL element 2 of the second embodiment shown in FIG. 2 includes a multilayer electron transport layer 14A instead of the multilayer electron transport layer 14. The structure of the organic EL element 2 is the same as the structure of the organic EL element 1 except that the multilayer electron transport layer 14A is provided.

The multilayer electron transport layer 14A included in the organic EL element 2 is different from the multilayer electron transport layer 14 in that the metal layer 14d is provided between the first mixed layer 14b and the electron transport layer 14a.

The metal layer 14d is laminated on the first mixed layer 14b so as to be in contact with the first mixed layer 14b. The metal layer 14d is also in contact with the electron transport layer 14a.

Examples of the material of the metal layer 14d include alkali metals and alkaline earth metals. Examples of the alkali metal of the metal layer 14d are lithium, sodium, potassium, rubidium, cesium, and platinum. Examples of alkaline earth metals are magnesium, calcium, strontium, barium, and radium. Among them, magnesium is preferred. An example of the thickness of the metal layer 14d is 0.5 nm to 10 nm. The metal layer 14d can be formed using, for example, a vacuum evaporation method.

The organic EL element 2 has the same structure as the organic EL element 1 except for the point of having the metal layer 14d, and therefore has at least the same effect as the organic EL element 1. Moreover, by having the metal layer 14d, It is possible to reduce the driving voltage and further improve the device life. As a result, the driving stability of the organic EL element 2 is further improved.

The various embodiments of the present invention have been described above, but are not limited to the illustrated various embodiments, but are intended to include all changes within the scope of patent application and the equivalent meaning and scope in accordance with the scope of patent application.

For example, the structure of the organic EL element is not limited to the structure illustrated in FIGS. 1 and 2.

The organic EL element only needs to have a multilayer electron transport layer between the light-emitting layer 13 and the cathode E2. An example of the layer structure that an organic EL element can adopt is shown. The following description also includes the configuration of the first and second embodiments.

a) Anode/hole injection layer/light emitting layer/multilayer electron transport layer/cathode

b) Anode/hole injection layer/hole transport layer/light emitting layer/multilayer electron transport layer/cathode

c) Anode/luminescent layer/multilayer electron transport layer/cathode

The symbol "/" means that the layers on both sides of the symbol "/" are joined.

In a) to c), the so-called "multilayer electron transport layer" means any one of the following: (i) the first layered structure: the first mixed layer/electron transport layer, (ii) the second layered structure: The first mixed layer/electron transport layer/second mixed layer, (iii) the third layered structure: first mixed layer/metal layer/electron transport layer, And (iv) 4th laminated structure: 1st mixed layer/metal layer/electron transport layer/2nd mixed layer.

As described above in the second layered structure and the fourth layered structure, when the multilayer type electron transport layer includes the organic EL element of the second mixed layer, the organic EL element correspondingly has an electron injection layer.

When at least one of the layers constituting the multi-layer electron transport layer is a layer having a function of blocking the transport of holes, such a layer having a function of blocking the transport of holes is sometimes called a hole blocking layer.

The so-called hole blocking layer has a function of blocking the transport of holes, and for example, it is possible to manufacture an organic EL element in which only the hole current flows, and the blocking effect can be confirmed by the reduction of its current value.

In the layer structures of a) and b) above, when the hole injection layer and/or the hole transport layer have a function of blocking the transport of electrons, these layers are sometimes referred to as electron blocking layers. The electron blocking layer has a function of blocking the transport of electrons. For example, an organic EL element that can flow only an electron current can be manufactured, and the effect of blocking the transport of electrons can be confirmed by the decrease in the measured current value. An electron blocking layer different from the hole injection layer and/or the hole transport layer may also be provided between the anode and the light emitting layer.

Furthermore, the organic EL element may have a single light-emitting layer, or may have two or more light-emitting layers. In any of the layer structures of a) to c) above, when the layered body disposed between the anode and the cathode is referred to as "structural unit A", it is an organic EL element having two light-emitting layers The structure can be exemplified by the layer structure shown in d) below. 2 (Structural unit A) The layer structure can be the same as or different from each other.

d) anode/(structural unit A)/charge generation layer/(structural unit A)/cathode

The charge generation layer here refers to a layer that generates holes and electrons by applying an electric field. As the charge generation layer, for example, a thin film composed of vanadium oxide, indium tin oxide (Indium Tin Oxide: ITO for short), molybdenum oxide, or the like can be mentioned.

When "(structural unit A)/charge generation layer" is set as "structural unit B", as the structure of an organic EL element having three or more light-emitting layers 13, the layer structure shown in e) below can be mentioned.

e) anode/(structural unit B) x/(structural unit A)/cathode

The symbol "x" represents an integer of 2 or more, and "(structural unit B)x" represents a laminate formed by stacking (structural unit B) x segments. Moreover, the structure of a plurality of (structural unit B) layers may be the same or different.

Instead of providing a charge generation layer, a plurality of light-emitting layers may be directly stacked to constitute an organic EL element.

The description so far is an example in which the anode is arranged on the substrate side, but the cathode may be arranged on the substrate side. At this time, for example, when manufacturing each organic EL element of the layer structure of a) to e) on the substrate, the layers may be stacked in order from the cathode (to the right of each configuration) to e) on the substrate.

[Example]

Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to any of the following examples.

[Example 1]

As Example 1, as shown in Figure 1, manufactured on a substrate An organic EL device formed by laminating an anode, a hole injection layer, a hole transport layer, a light emitting layer, a first mixed layer, an electron transport layer, a second mixed layer, and a cathode in the following order. The organic EL element of Example 1 is referred to as an organic EL element A1. In Example 1, the organic EL element A1 was sealed using glass. Hereinafter, a method of manufacturing the organic EL element A1 will be specifically described.

<substrate and anode>

A glass substrate is prepared as a substrate of the organic EL element A1. On the glass substrate, an ITO thin film is formed as an anode in a predetermined pattern. The ITO thin film is formed using a sputtering method, and its film thickness is 45 nm. The glass substrate with the ITO thin film formed on the surface was washed with an organic solvent, an alkaline detergent and ultrapure water, and then boiled with an organic solvent for 10 minutes and dried. Next, using an ultraviolet ozone (UV-O3) device, the surface on which the ITO film is formed is subjected to ultraviolet ozone treatment for about 15 minutes.

<hole injection layer>

A hole injection material composed of an organic material having charge transport properties and an electron-accepting material is applied on the ITO thin film by a spin coating method to form a coating film with a thickness of 35 nm. Hereinafter, the hole injection material used in Example 1 is referred to as a hole injection material α 1. In the atmosphere, the coating film was dried on a hot plate to form a hole injection layer. In the drying using a hot plate, the coating film was first dried at 50°C for 4 minutes, and then further dried at 230°C for 15 minutes.

<hole transport layer>

A hole transport layer formed by mixing a hole transport material of a polymer material with xylene to obtain a solid (hole transport material) concentration of 0.6% by weight Composition. Hereinafter, the hole transport material used in Example 1 is referred to as hole transport material α 2. The obtained composition for forming a hole transport layer was applied on the hole injection layer using a spin coating method to obtain a coating film with a thickness of 20 nm. Under a nitrogen environment (inert environment), the glass substrate provided with the coating film was heated at 180° C. for 60 minutes by a hot plate to evaporate the solvent, and then naturally cooled to room temperature to obtain a hole transport layer.

<luminescent layer>

The light-emitting conjugated polymer material and xylene were mixed to obtain a composition for forming a light-emitting layer having a concentration of the light-emitting conjugated polymer material of 1.3%. In Example 1, a blue light-emitting conjugated polymer material was used as the light-emitting conjugated polymer material. Hereinafter, the blue light-emitting conjugated polymer material used in Example 1 is referred to as blue light-emitting conjugated polymer material α 3. The obtained composition for forming a light-emitting layer was applied on the hole transport layer using a spin coating method to obtain a coating film with a thickness of 65 nm. Under a nitrogen atmosphere (inert environment), the glass substrate provided with the coating film was heated at 150° C. for 10 minutes using a hot plate to evaporate the solvent, and then naturally cooled to room temperature to obtain a light-emitting layer.

<1st mixed layer>

The glass substrate on which the light-emitting layer was formed was moved to a vapor deposition processing chamber, and a first mixed layer was formed on the light-emitting layer. Specifically, the system is exhausted until the vacuum degree in the vapor deposition processing chamber becomes 1.0×10 ^-5 Pa or less, and the electron transport material and the organometallic complex compound are co-evaporated on the light-emitting layer using a vacuum vapor deposition method. To form a first mixed layer with a film thickness of 5 nm, an electron transport material and an organometallic complex compound are mixed. Hereinafter, the electron transport material and the organometallic complex compound used in Example 1 are referred to as the electron transport material α 4 and the organometallic complex compound α 5. The electron transport material α 4 is TR-E314 manufactured by TORAY Corporation. The organometallic complex compound α 5 is 8-quinolinol sodium (Naq). The vapor deposition rates of the electron transport material α 4 and the organometallic complex compound α 5 were each set to 0.3Å/s. That is, the mass ratio of the electron transport material α 4 to the organometallic complex compound α 5 in the first mixed layer is 50:50.

<electron transport layer>

After the first mixed layer is formed, the electron transport layer is formed on the first mixed layer in the same vapor deposition chamber. Specifically, the electron transport material α 4 is vapor-deposited on the first mixed layer using a vacuum vapor deposition method to form an electron transport layer with a film thickness of 60 nm. The vapor deposition rate of the electron transport material α 4 is set to 0.5Å/s.

<2nd mixed layer>

The electron transport layer is formed, and the second mixed layer is formed on the electron transport layer in the same vapor deposition chamber. Specifically, the electron transport material α 4 and the organometallic complex compound α 5 are co-evaporated on the electron transport layer using a vacuum evaporation method to form the electron transport material α 4 and the organic metal with a thickness of 5 nm The second mixed layer formed by mixing the complex compound α 5. The vapor deposition rates of the electron transport material α 4 and the organometallic complex compound α 5 are each set to 0.3Å/s. That is, the mass ratio of the electron transport material α 4 and the organometallic complex compound α 5 in the second mixed layer is 50:50.

<cathode>

After the second mixed layer is formed, the negative electrode is formed in the same vapor deposition chamber pole. Specifically, magnesium and silver are co-evaporated on the second mixed layer using a vacuum evaporation method to form a cathode a with a thickness of 20 nm, and then aluminum is deposited on the cathode a using a vacuum evaporation method, and A cathode b with a film thickness of 100 nm is formed. That is, as the cathode of the organic EL element A1, a cathode having a two-layer structure in which a cathode a having a thickness of 20 nm and a cathode b having a thickness of 100 nm is formed on the second mixed layer is formed.

<glass seal>

After the cathode is formed, the glass substrate after the cathode is formed is transported from the vapor deposition chamber to the sealed processing chamber without being exposed to the atmosphere. Next, in a nitrogen atmosphere (inert environment), after sealing glass coated with UV hardening resin around it and bonding to the glass substrate transported from the vapor deposition chamber, the UV hardening resin is cured by irradiating UV light to use glass The organic EL element A1 is sealed.

The organic EL element A1 produced as described above was driven, and the element life, current efficiency, and driving voltage were measured.

When the brightness at the start of driving is set to 100, the device life is evaluated using LT80, which is the time from the start of driving until the brightness decreases to 80. The measurement of the device life was performed by driving the organic EL device A1 at a constant current of 10 mA/cm ² . The driving voltage is a voltage when the organic EL element A1 is driven with a constant current of 10 mA/cm ² . The current efficiency is the value when the brightness is 1000 cd/m ² (that is, 1000 nit).

In the measurement results of the organic EL device A1, the device lifetime (LT80) was 15.1 hours, the current efficiency was 1.0 cd/A, and the driving voltage was 6.0V.

[Comparative Example 1]

As Comparative Example 1, it was fabricated on a substrate in the following order An organic EL device formed by laminating an electrode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode. The organic EL element of Comparative Example 1 is referred to as organic EL element B1. The structure of the organic EL element B1 has the same structure as the organic EL element A1 of Example 1 except that the first and second mixed layers and the film thickness of the electron transport layer are 70 nm. That is, in Comparative Example 1, the materials, thicknesses, and forming methods of the substrate, anode, hole injection layer, hole transport layer, light emitting layer, and cathode are the same as in Example 1. Therefore, the method of forming the electron transport layer will be described, and other description will be omitted.

In Comparative Example 1, the electron transport layer was formed as follows. That is, after the light-emitting layer is formed, the glass substrate (substrate) on which the light-emitting layer is formed is moved to the vapor deposition processing chamber. Then, exhaust was performed until the degree of vacuum in the vapor deposition processing chamber became 1.0×10 ^-5 Pa or less, and the electron transport material α 4 was vapor-deposited on the light-emitting layer using a vacuum vapor deposition method to form electron transport with a film thickness of 70 nm Floor. The vapor deposition rate of the electron transport material α 4 is set to 0.5Å/s.

In Comparative Example 1, the produced organic EL element B1 was glass-sealed in the same manner as in Example 1.

The organic EL device B1 of Comparative Example 1 was driven and the device life, current efficiency, and driving voltage were measured under the same conditions as in Example 1.

As a result, in Comparative Example 1, the device life (LT80) was 0.1 hours, the current efficiency was 1.0 cd/A, and the driving voltage was 6.1V.

[Comparative Example 2]

As Comparative Example 2, the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer, the first 2 Organic EL device formed by mixing layers and cathodes. The organic EL element of Comparative Example 2 is referred to as organic EL element B2. The structure of the organic EL element B2 is the same as the organic EL element A1 of Example 1 except that it does not have the first point and the point that the film thickness of the electron transport layer is 65 nm. In Comparative Example 2, the materials, thicknesses, and formation methods of the substrate, anode, hole injection layer, hole transport layer, light emitting layer, and second mixed layer cathode are the same as in Example 1. In addition, the method of forming the hole transport layer of Comparative Example 2 is the same as that of Comparative Example 1 except that the film thickness is 65 nm.

In Comparative Example 2, as in Example 1, the organic EL element B2 was glass-sealed.

The organic EL device B2 of Comparative Example 2 was driven and the device life, current efficiency, and driving voltage were measured under the same conditions as in Example 1. As a result, in Comparative Example 2, the device life (LT80) was 2.3 hours, the current efficiency was 1.0 cd/A, and the driving voltage was 5.5V.

[Comparison of Example 1 and Comparative Examples 1 and 2]

Table 1 shows the measurement results of the device life, current efficiency, and driving voltage of the organic EL devices A1, B1, and B2 of the aforementioned Example 1, Comparative Examples 1, and 2.

It can be understood from Table 1 that Example 1 provided with the first mixed layer compared to Comparative Examples 1 and 2 can understand that when the current efficiency and the driving voltage are substantially the same, a long device life can be obtained. In particular, by comparing Example 1 with Comparative Example 2, it can be understood that such a difference in device life due to the influence of the first mixed layer. Therefore, it can be understood that by providing the first mixed layer containing the electron transport material and the organometallic complex compound, the driving stability of the organic EL element is improved.

Next, as shown in FIG. 2, the verification results of the effect when the multilayer electron transport layer further includes a metal layer will be described.

(Example 2)

As Example 2, as shown in FIG. 2, the anode, the hole injection layer, the hole transport layer, the light emitting layer, the first mixed layer, the metal layer, the electron transport layer, the second An organic EL device formed by laminating a mixed layer and a cathode. The organic EL element of Example 2 is referred to as organic EL element A2. In Example 2, the organic EL element A2 was sealed with glass in the same manner as in Example 1. Specifically, the organic EL element A2 Of manufacturing methods.

<substrate and anode>

A glass substrate is prepared as the substrate of the organic EL element A2. On the prepared glass substrate, an ITO thin film is formed as an anode in a predetermined pattern. The ITO thin film is formed using a sputtering method, and its film thickness is 45 nm. The glass substrate with the ITO thin film formed on the surface was washed with an organic solvent, an alkaline detergent and ultrapure water, and then boiled with an organic solvent for 10 minutes and dried. Next, using an ultraviolet ozone (UV-O3) device, the surface on which the ITO film is formed is subjected to ultraviolet ozone treatment for about 15 minutes.

<hole injection layer>

The hole injection layer was formed in the same manner as in Example 1, except that the ink containing the hole injection material α 1 was applied on the ITO film by spin coating to form a coating film with a thickness of 80 nm.

<hole transport layer>

The hole transport layer was formed on the hole injection layer in the same manner as in Example 1.

<luminescent layer>

The red light-emitting conjugated polymer material and xylene were mixed to obtain a composition for forming a light-emitting layer having a red light-emitting conjugated polymer material concentration of 2.8%. Hereinafter, the red light-emitting conjugated polymer material used in Example 2 is referred to as red light-emitting conjugated polymer material α 6. The obtained composition for forming a light-emitting layer was applied on the hole transport layer using a spin coating method to obtain a coating film with a thickness of 160 nm. Under a nitrogen atmosphere (inert environment), the glass substrate provided with the coating film is After heating at 150°C for 10 minutes to evaporate the solvent, it was naturally cooled to room temperature to obtain a light-emitting layer.

<1st mixed layer>

The first mixed layer was formed on the light-emitting layer in the same manner as in Example 1.

<metal layer>

After the first mixed layer is formed, magnesium is vapor-deposited on the first mixed layer using a vacuum deposition method in the vapor deposition processing chamber after the first mixed layer is formed to form a metal layer with a thickness of 2 nm. The evaporation rate of magnesium is set to 0.5Å/s.

<electron transport layer>

After the metal layer was formed, the electron transport layer was formed in the same vapor deposition chamber as in Example 1.

<2nd mixed layer>

After the electron transport layer was formed, it was performed in the same manner as in Example 1, except that the deposition rates of the electron transport material α 4 and the organometallic complex compound α 5 were each set to 0.1Å/s and 0.9Å/s. On the other hand, a second mixed layer is formed on the electron transport layer. That is, the mass ratio of the electron transport material α 4 and the organometallic complex compound α 5 in the second mixed layer is 10:90.

<cathode>

After the second mixed layer is formed, the cathode is formed in the same vapor deposition chamber. Specifically, magnesium is vapor-deposited on the second mixed layer using the vacuum vapor deposition method to form the cathode a with a film thickness of 2 nm, and silver is vapor-deposited on the cathode a using the vacuum vapor deposition method to form a film thickness It is 18nm cathode b. Next, aluminum was vapor-deposited on the cathode b using a vacuum evaporation method to form a cathode c with a film thickness of 100 nm. That is, the cathode of the organic EL element A2 is On the mixed layer, a cathode having a three-layer structure is formed by laminating a cathode a with a thickness of 2 nm, a cathode b with a thickness of 18 nm, and a cathode c with a thickness of 100 nm.

<glass seal>

After the cathode was formed, the organic EL element A2 was sealed with glass in the same manner as in Example 1.

Since the organic EL element A2 contains a red light-emitting conjugated polymer material α 6 in the light-emitting layer, the organic EL element A2 is a red light-emitting element.

The organic EL device A2 produced as described above was driven, and the device life, current efficiency, and drive voltage were measured. The device life was evaluated by LT80 in the same manner as in Example 1. The life of the device is measured in a state where the device is driven at a constant current of 80 mA/cm ² . The current efficiency is the value when the brightness is 100 cd/m ² (that is, 100 nit). The driving voltage is the value when the current density is 10 mA/cm ² .

In the measurement results of the organic EL device A2, the device life (LT80) was 156.1 hours, the current efficiency was 8.2 cd/A, and the driving voltage was 6.8 V.

(Example 3)

As Example 3, an organic EL element was produced in the same manner as in Example 2 except that the metal layer was not provided, and glass sealing was used. The organic EL element of Example 3 is referred to as organic EL element A3. Like the organic EL element A2, the organic EL element A3 is a red light-emitting element.

The produced organic EL device A3 was measured under the same conditions as in Example 2 for the device life, current efficiency, and driving voltage. in In Example 3, the element life (LT80) was 52.0 hours, the current efficiency was 6.4 cd/A, and the driving voltage was 11.5V.

[Comparison of Example 2 and Example 3]

Table 2 shows the measurement results of the element lifetime, current efficiency, and driving voltage of the foregoing Examples 2 and 3.

It can be understood from Table 2 that, compared to Example 3 without a metal layer, Example 2 with a metal layer can be driven at a lower driving voltage and can achieve a longer device life.

(Example 4)

In Example 4, an organic EL device having the same configuration as in Example 2 was manufactured except that the structures of the hole injection layer and the light-emitting layer were different, and glass sealing was used in the same manner as in Example 2. The organic EL element of Example 4 is referred to as organic EL element A4. The method of forming the hole injection layer and the light-emitting layer in the organic EL element A4 will be described.

<hole injection layer>

The hole injection layer was formed in the same manner as in Example 2 except that the thickness of the coating film formed by applying the ink containing the hole injection material α 1 on the ITO thin film was 85 nm.

<luminescent layer>

The green light-emitting conjugated polymer material and xylene were mixed to obtain a composition for forming a light-emitting layer having a concentration of 2.2% of the green light-emitting conjugated polymer material. Hereinafter, the green light-emitting conjugated polymer material used in Example 4 is referred to as green light-emitting conjugated polymer material α 7. The obtained composition for forming a light-emitting layer was applied on the hole transport layer using a spin coating method to obtain a coating film with a thickness of 85 nm. Under a nitrogen atmosphere (inert environment), the glass substrate provided with the coating film was heated at 150° C. for 10 minutes using a hot plate to evaporate the solvent, and then naturally cooled to room temperature to obtain a light-emitting layer.

As described above, since the light-emitting layer contains the green light-emitting conjugated polymer material α 7, the organic EL element A4 is a green light-emitting element.

The manufactured organic EL element A4 was driven, and the element life, current efficiency, and driving voltage were measured. The device life was evaluated by LT80 in the same manner as in Example 1. The life of the device is measured in a state where the device is driven with a constant current of 25 mA/cm ² . The current efficiency is the value when the brightness is 100 cd/m ² (that is, 100 nit). The driving voltage is the value when the current density is 10 mA/cm ² .

In the organic EL device A3, the device lifetime (LT80) was 12.4 hours, the current efficiency was 6.1 cd/A, and the driving voltage was 6.2V.

(Example 5)

As Example 5, an organic EL element was manufactured in the same manner as in Example 4 except that the metal layer was not provided, and glass sealing was used. The organic EL element of Example 5 is referred to as organic EL element A5. Like the organic EL element A4, the organic EL element A5 is a green light-emitting element.

The produced organic EL device A5 was measured under the same conditions as in Example 4 for the device life, current efficiency, and driving voltage. In Example 5, the device life (LT80) was 1.7 hours, the current efficiency was 12.9 cd/A, and the driving voltage was 8.9V.

[Comparison of Example 4 and Example 5]

Table 3 shows the measurement results of the device life, current efficiency, and driving voltage in the foregoing Examples 4 and 5.

It can be understood from Table 3 that, compared to Example 5 without the metal layer, Example 4 with the metal layer can be understood, although the current efficiency is reduced, but it can be driven at a lower driving voltage and can achieve a longer Component life.

(Example 6)

In Example 6, except that the structures of the hole injection layer and the light-emitting layer are different, an organic EL element having the same configuration as in the case of Example 2 was manufactured and sealed with glass. The organic EL element of Example 6 is referred to as organic EL element A6. For the hole injection layer in the organic EL element A6 And the formation method of the light emitting layer will be described.

<hole injection layer>

The hole injection layer was formed in the same manner as in Example 2 except that the thickness of the coating film formed by applying the ink containing the hole injection material α 1 on the ITO thin film was 35 nm.

<luminescent layer>

The blue light-emitting conjugated polymer material α 3 and xylene were mixed to obtain a light-emitting layer forming composition having a blue light-emitting conjugated polymer material α 3 concentration of 1.3%. Hereinafter, the blue light-emitting conjugated polymer material used in Example 4 is referred to as blue light-emitting conjugated polymer material α 7. The obtained composition for forming a light-emitting layer was applied on the hole transport layer using a spin coating method to obtain a coating film with a thickness of 65 nm. Under a nitrogen atmosphere (inert environment), the glass substrate provided with the coating film was heated at 150° C. for 10 minutes using a hot plate to evaporate the solvent, and then naturally cooled to room temperature to obtain a light-emitting layer.

As described above, since the blue light-emitting conjugated polymer material α 3 is contained in the light-emitting layer, the organic EL element A6 is a blue light-emitting element.

The manufactured organic EL element A6 was driven, and the element life, current efficiency, and driving voltage were measured. The device life was evaluated by LT80 in the same manner as in Example 1. The life of the device is measured in a state where the device is driven at a constant current of 80 mA/cm ² . The current efficiency is the value when the brightness is 100 cd/m ² (that is, 100 nit). The driving voltage is the value when the current density is 10 mA/cm ² .

In the organic EL element A6, the element life (LT80) is 11.8 Hours, the current efficiency is 1.7cd/A, and the driving voltage is 4.9V.

(Example 7)

As Example 7, an organic EL element was produced in the same manner as in Example 6 except that the metal layer was not provided, and glass sealing was used. The organic EL element of Example 7 is referred to as organic EL element A7. Like the organic EL element A6, the organic EL element A7 is a blue light-emitting element.

The produced organic EL device A7 was driven, and the device life, current efficiency, and drive voltage were measured under the same conditions as in Example 6. In Example 7, the device life (LT80) was 8.0 hours, the current efficiency was 1.7 cd/A, and the driving voltage was 5.1V.

[Comparison of Example 6 and Example 7]

Table 4 shows the measurement results of the device life, current efficiency, and driving voltage in the foregoing Examples 6 and 7.

It can be understood from Table 4 that, compared to Example 7 without a metal layer, Example 6 with a metal layer can be understood, which can be driven with a lower driving voltage and can achieve a longer device life.

From the results of Table 2 to Table 4, it can be confirmed that any of the red light-emitting element, the green light-emitting element, and the blue light-emitting element By further providing a metal layer, the life of the device can be increased, and the metal layer system contributes to improving the driving stability.

1‧‧‧ organic EL element

11‧‧‧hole injection layer

12‧‧‧Electric tunnel transmission layer

13‧‧‧luminous layer

14‧‧‧Multi-layer electron transport layer

14a‧‧‧Electronic transmission layer

14b‧‧‧The first mixed layer (the mixed layer on the light emitting layer side)

14c‧‧‧The second mixed layer (cathode side mixed layer)

E1‧‧‧Anode

E2‧‧‧Cathode

P‧‧‧Substrate

Claims (5)

An organic EL element includes an anode, a cathode, and a light-emitting layer disposed between the anode and the cathode. The organic EL element includes a multilayer electron transport layer provided between the light-emitting layer and the cathode. The multi-layer type electron transport layer has: an electron transport layer containing an electron transport material; a light emitting layer side mixing layer provided between the electron transport layer and the light emitting layer in contact with the light emitting layer; and a cathode side mixing The layer is closer to the cathode side than the electron transport layer and is provided in contact with the electron transport layer; the multilayer electron transport layer further includes a metal layer between the light-emitting layer side mixed layer and the electron transport layer The light emitting layer side mixed layer system contains both the electron transport material and the organometallic complex compound; the cathode side mixed layer system contains both the electron transport material and the organometallic complex compound. The organic EL device according to item 1 of the patent application range, wherein the thickness of the mixed layer on the light-emitting layer side is 2 nm to 20 nm. The organic EL device according to item 1 of the patent application range, wherein the organic metal complex compound contained in the mixed layer on the light-emitting layer side is 8-quinolinol sodium. The organic EL device according to item 2 of the patent application range, wherein the organic metal complex compound contained in the mixed layer on the light-emitting layer side is 8-quinolinol sodium. The organic EL device according to any one of claims 1 to 4, wherein the metal layer contains an alkali metal or an alkaline earth metal.

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