JP2016143797A - Organic EL element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element whose driving stability can be further improved.SOLUTION: An organic EL element 1 includes an anode E1, a cathode E2, a light-emitting layer 13 arranged between the anode and the cathode, and a multilayered electron transport layer 14 provided between the light-emitting layer and the cathode. The multilayered electron transport layer includes an electron transport layer 14a containing an electron transport material and a light-emitting layer side mixed layer 14b provided in contact with the light-emitting layer between the electron transport layer and the light-emitting layer and thinner than the electron transport layer. The light-emitting layer side mixed layer contains an electron transport material and an organometallic complex compound.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic EL element.

  In an organic electroluminescence element (hereinafter sometimes referred to as “organic EL element”), improvement in element life, that is, improvement in driving stability is required. For example, in the technique described in Patent Document 1, driving stability is improved by providing a hole blocking layer in contact with the light emitting layer in an organic EL element in which an anode, a light emitting layer and a cathode are laminated on a substrate. ing.

Japanese Patent No. 4325197

  However, in recent years, further driving stability of organic EL elements has been demanded.

  Accordingly, an object of the present invention is to provide an organic EL element that can further improve driving stability.

  An organic EL device according to one aspect of the present invention is an organic EL device having an anode, a cathode, and a light emitting layer provided between the anode and the cathode, and is a multilayer provided between the light emitting layer and the cathode. The multilayer electron transport layer includes an electron transport layer containing an electron transport material, and a light emitting layer side mixed layer provided in contact with the light emitting layer between the electron transport layer and the light emitting layer. And the light emitting layer side mixed layer contains an organometallic complex compound with an electron transport material.

  In the said structure, the multilayer side electron transport layer which has a light emitting layer side mixed layer and an electron carrying layer is provided. And since the light emitting layer side mixed layer provided in contact with the light emitting layer contains an organometallic complex compound in addition to the electron transporting material, driving stability can be improved.

  In one embodiment, the multilayer electron transport layer further comprises a cathode-side mixed layer provided in contact with the electron transport layer on the cathode side of the electron transport layer, and the cathode-side mixed layer together with the electron transport material is an organometallic complex compound. May be included.

  In this configuration, the multilayer electron transport layer has a cathode-side mixed layer on the cathode side of 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 is made efficient. As a result, the drive voltage can be reduced.

  In one embodiment, the multilayer electron transport layer may further include a metal layer between the light emitting layer side mixed layer and the electron transport layer. Thereby, the drive voltage is reduced.

  In one embodiment, the light emitting layer side mixed layer may have a thickness of 2 nm to 20 nm. This is because if the thickness is smaller than 2 nm, pinholes are likely to occur, and if the thickness is larger than 20 nm, the thickness of the entire multilayer electron transport layer also increases, and the drive voltage increases.

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

  ADVANTAGE OF THE INVENTION According to this invention, the organic EL element which can improve drive stability more can be provided.

FIG. 1 is a drawing schematically showing a configuration of an organic EL element according to an embodiment. FIG. 2 is a drawing schematically showing a configuration of an organic EL element according to another embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same symbols are assigned to the same elements. A duplicate description is omitted. The dimensional ratios in the drawings do not necessarily match those described.

(First embodiment)
As schematically shown in FIG. 1, the organic EL device 1 according to the first embodiment includes an anode E1, a hole injection layer 11, a hole transport layer 12, a light emitting layer 13, and a multilayer electron transport on a substrate P. The layer 14 and the cathode E2 are provided in order. The organic EL element 1 can be suitably used for a curved or flat illumination device, for example, a planar light source used as a light source of a scanner, and a display device.

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

<Board>
As the substrate P, a substrate that is not chemically changed in the manufacturing process of the organic EL element 1 is suitably used. For example, a rigid substrate such as a glass substrate or a silicon substrate is used, but a flexible substrate such as a plastic substrate or a polymer film is used. It may be a substrate. By using a flexible substrate, a flexible organic EL element can be obtained as a whole. On the substrate P, an electrode for driving the organic EL element 1 and a drive circuit may be formed in advance.

<Anode>
A thin film with low electrical resistance is suitably used for the anode E1. At least one of the anode E1 and the cathode E2 is transparent. For example, in a bottom emission type organic EL element, the anode E1 disposed on the substrate P side is transparent, and the light is in the visible light region. Those having high transmittance are preferably used. As the material of the anode E1, a conductive metal oxide film, a metal thin film, or the like is used.

  Specifically, as the anode E1, a thin film made of indium oxide, zinc oxide, tin oxide, indium tin oxide (abbreviated as ITO), indium zinc oxide (abbreviated as IZO), or the like, gold Platinum, silver, copper, aluminum, or an alloy containing at least one of these metals is used.

  Among these, as the anode E1, a thin film made of ITO, IZO, and tin oxide is preferably used because of transmittance and ease of patterning. When light is extracted from the cathode E2 side, the anode E1 is preferably formed of a material that reflects light from the light-emitting layer 13 to the cathode E2 side. A metal, metal oxide or metal sulfide of 0.0 eV or more is preferable. For example, a metal thin film having a thickness that reflects light is used.

  Examples of the method for forming the anode E1 include a vacuum deposition method, a sputtering method, an ion plating method, and a plating method. Further, as the anode E1, an organic transparent conductive film such as polyaniline or a derivative thereof, polythiophene or a derivative thereof may 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 the 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 aluminum oxide, phenylamine compounds, starburst type amine compounds, phthalocyanine compounds, and amorphous carbon. , Polyaniline, and polythiophene derivatives such as polyethylenedioxythiophene (PEDOT).

  A conventionally known organic material having a charge transporting property can be used as a hole injection layer material by combining this with an electron accepting material.

  As the electron-accepting material, a heteropolyacid compound or an aryl sulfonic acid can be suitably used.

  The heteropoly acid compound has a structure in which a hetero atom is located at the center of a molecule, which is represented by a chemical structure of Keggin type or Dawson type, and is an oxygen acid such as vanadium (V), molybdenum (Mo), tungsten (W), etc. This is a polyacid obtained by condensing an isopolyacid and an oxygen acid of a different element. Examples of the oxygen acid of a different element mainly include silicon (Si), phosphorus (P), and arsenic (As) oxygen acids. Specific examples of the heteropolyacid compound include phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, phosphotungstomolybdic acid, and silicotungstic acid.

  As aryl sulfonic acid, benzene sulfonic acid, tosylic acid, p-styrene sulfonic acid, 2-naphthalene sulfonic acid, 4-hydroxybenzene sulfonic acid, 5-sulfosalicylic acid, p-dodecyl benzene sulfonic acid, dihexyl benzene sulfonic 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, dinonylna Tarensuruhon acid, 2,7-dinonyl-4-naphthalenesulfonic acid, dinonyl naphthalene disulfonic acid, 2,7-dinonyl-4,5-naphthalene disulfonic acid, and the like.

  A heteropolyacid compound and an aryl sulfonic acid may be mixed and used.

  The hole injection layer 11 is formed, for example, by a coating method using a coating liquid containing the above-described hole injection material. The solvent of the coating solution is not particularly limited as long as it dissolves the hole injection material. For example, a chlorine-based solvent such as chloroform, water, methylene chloride, and dichloroethane, an ether-based solvent such as tetrahydrofuran, and an aromatic carbonization such as toluene and xylene. Examples thereof include hydrogen solvents, ketone solvents such as acetone and methyl ethyl ketone, and ester solvents such as ethyl acetate, butyl acetate and ethyl cellosolve acetate.

  As the coating method, spin coating method, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, spray coating method, screen printing method, flexographic printing method, An offset printing method, an inkjet printing method, etc. can be mentioned. The hole injection layer 11 can be formed by applying the above-described coating solution onto the substrate P on which the anode E1 is formed using one of these coating methods.

  It is also possible to form the hole injection layer 11 by vacuum evaporation or the like. Furthermore, if the hole injection layer 11 is made of a metal oxide, a sputtering method, an ion plating method, or the like can be used.

  The thickness of the hole injection layer 11 varies depending on the material used, and is appropriately determined in consideration of the required characteristics and the ease of film formation. 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 performs hole injection from the layer (hole injection layer 11 in FIG. 1) in contact with the interface on the anode E1 side of the hole transport layer 12 or the hole transport layer 12 closer to the anode E1. It is a functional layer having a function to improve.

  Examples of the hole transport material constituting the hole transport layer 12 include polyvinyl carbazole or derivatives thereof, polysilane or derivatives thereof, polysiloxane derivatives having aromatic amines in side chains or main chains, pyrazoline derivatives, arylamine derivatives, stilbene derivatives. , Triphenyldiamine derivative, polyaniline or derivative thereof, polythiophene or derivative thereof, polyarylamine or derivative thereof, polypyrrole or derivative thereof, poly (p-phenylene vinylene) or derivative thereof, or poly (2,5-thienylene vinylene) Or the derivative | guide_body etc. can be mentioned. Moreover, the hole transport layer material currently disclosed by Unexamined-Japanese-Patent No. 2012-144722 can also be mentioned.

  Among these, hole transport materials include polyvinyl carbazole or derivatives thereof, polysilane or derivatives thereof, polysiloxane derivatives having aromatic amine compound groups in the side chain or main chain, polyaniline or derivatives thereof, polythiophene or derivatives thereof, poly Polymeric hole transport materials such as arylamine or derivatives thereof, poly (p-phenylene vinylene) or derivatives thereof, or poly (2,5-thienylene vinylene) or derivatives thereof are preferred, and polyvinylcarbazole or derivatives thereof are more preferred. , Polysilane or a derivative thereof, and a polysiloxane derivative having an aromatic amine in the side chain or main chain. In the case of a low-molecular hole transport material, it is preferably used by being dispersed in a polymer binder.

  Examples of the method for forming the hole transport layer 12 include a method of forming a film from a mixed solution with a polymer binder in a low molecular hole transport material, and a method of forming a hole transport layer from a solution in a polymer hole transport material. There can be mentioned a method by film formation.

  As a solvent used for film formation from a solution, any solvent capable of dissolving a hole transport material may be used. Chlorine solvents such as chloroform, methylene chloride and dichloroethane, ether solvents such as tetrahydrofuran, aromatics such as toluene and xylene. Examples thereof include hydrocarbon solvents, ketone solvents such as acetone and methyl ethyl ketone, and ester solvents such as ethyl acetate, butyl acetate, and ethyl cellosolve acetate.

  As a film forming method from a solution, the same coating method as the method mentioned as the method of forming a hole injection layer can be mentioned.

  As the polymer binder to be mixed, those not extremely disturbing charge transport are preferable, and those having low absorption of visible light are suitably used. Examples of the polymer binder include polycarbonate, polyacrylate, polymethyl acrylate, polymethyl methacrylate, polystyrene, polyvinyl chloride, and polysiloxane.

  The film thickness of the hole transport layer 12 varies depending on the material used, is appropriately set so that the drive voltage and the light emission efficiency are appropriate, and needs to have a thickness that does not generate pinholes at least. If the thickness is too thick, the driving voltage of the element increases, which is not preferable. 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.

<Light emitting layer>
The light emitting layer 13 usually includes an organic substance that mainly emits fluorescence and / or phosphorescence, or an organic substance and a dopant that assists the organic substance. The dopant is added, for example, to improve the luminous efficiency or change the emission wavelength. The organic substance is preferably a polymer compound from the viewpoint of solubility. It is preferable that the light emitting layer 13 contains the high molecular compound whose number average molecular weight of polystyrene conversion is 10 < ³ > -10 < ⁸ >. Examples of the light-emitting material constituting the light-emitting layer 13 include the following dye-based light-emitting materials, metal complex-based light-emitting materials, and polymer-based light-emitting materials.

  Examples of dye-based luminescent materials include cyclopentamine derivatives, tetraphenylbutadiene derivatives, triphenylamine derivatives, oxadiazole derivatives, pyrazoloquinoline derivatives, distyrylbenzene derivatives, distyrylarylene derivatives, pyrrole derivatives, thiophene ring compounds Pyridine ring compounds, perinone derivatives, perylene derivatives, oligothiophene derivatives, oxadiazole dimers, pyrazoline dimers, quinacridone derivatives, coumarin derivatives, and the like.

  Examples of the metal complex-based light emitting material include rare earth metals such as Tb, Eu, and Dy, or Al, Zn, Be, Pt, Ir, and the like as a central metal, and oxadiazole, thiadiazole, phenylpyridine, and phenylbenzimidazole. And a metal complex having a quinoline structure as a ligand. Examples of metal complexes include metal complexes having light emission from triplet excited states such as iridium complexes and platinum complexes, aluminum quinolinol complexes, benzoquinolinol beryllium complexes, benzoxazolyl zinc complexes, benzothiazole zinc complexes, azomethyl zinc complexes, A porphyrin zinc complex, a phenanthroline europium complex, etc. can be mentioned.

  Examples of polymer light-emitting materials include polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, the above dye materials, and metal complex materials. Materials etc. can be mentioned.

  Among the above light-emitting materials, examples of materials that emit blue light include distyrylarylene derivatives, oxadiazole derivatives, and polymers thereof, polyvinylcarbazole derivatives, polyparaphenylene derivatives, and polyfluorene derivatives. Of these, polymer materials such as polyvinyl carbazole derivatives, polyparaphenylene derivatives, and polyfluorene derivatives are preferred. Examples of the material that emits blue light include materials disclosed in Japanese Patent Application Laid-Open No. 2012-144722.

  Examples of materials that emit green light include quinacridone derivatives, coumarin derivatives, and polymers thereof, polyparaphenylene vinylene derivatives, polyfluorene derivatives, and the like. Of these, polymer materials such as polyparaphenylene vinylene derivatives and polyfluorene derivatives are preferred. Examples of the material that emits green light include materials disclosed in Japanese Patent Application Laid-Open No. 2012-036388.

  Examples of the material that emits red light include a coumarin derivative, a thiophene ring compound, and a polymer thereof, a polyparaphenylene vinylene derivative, a polythiophene derivative, and a polyfluorene derivative. Among these, polymer materials such as polyparaphenylene vinylene derivatives, polythiophene derivatives, and polyfluorene derivatives are preferable. Examples of the material that emits red light include materials disclosed in JP 2011-105701 A.

  Examples of the dopant material include perylene derivatives, coumarin derivatives, rubrene derivatives, quinacridone derivatives, squalium derivatives, porphyrin derivatives, styryl dyes, tetracene derivatives, pyrazolone derivatives, decacyclene, and phenoxazone.

  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 onto the hole transport layer 12, a vacuum deposition method, a transfer method, and the like. Among these, it is preferable to form the light emitting layer by a coating method because of the ease of the manufacturing process. As the solvent of the solution containing the light emitting material, for example, the solvents mentioned as the solvent of the coating solution for forming the hole injection layer 11 described above can be used.

  As a method for applying a solution containing a light emitting material, 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 slit coating method, a capillary Coating methods such as a coating method, a spray coating method, a nozzle coating method, a gravure printing method, a screen printing method, a flexographic printing method, an offset printing method, a reverse printing method, and an inkjet printing method can be used. The gravure printing method, the screen printing method, the flexographic printing method, the offset printing method, the reverse printing method, and the ink jet printing method are preferable in that pattern formation and multicolor coating are easy. In the case of a low molecular compound exhibiting sublimability, a vacuum deposition method can be used. Furthermore, the light emitting layer 13 can also be formed only at a desired place by a method such as laser or friction transfer or thermal transfer.

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

<Cathode>
The material of the cathode E2 is preferably a material having a small work function, easy electron injection into the multilayer electron transport layer 14, and high electrical conductivity. When light is extracted from the anode E1 side, the material from the light emitting layer 13 is reflected by the cathode E2 to the anode E1 side. Therefore, a material having a high visible light reflectance is preferable as the material of the cathode E2.

  For the cathode E2, for example, an alkali metal, an alkaline earth metal, a transition metal, a group 13 metal of the periodic table, or the like can be used. Examples of the material of the cathode E2 include lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, aluminum, scandium, vanadium, zinc, yttrium, indium, cerium, samarium, eurobium, terbium, ytterbium. Metals such as, alloys of two or more of the metals, alloys of one or more of the metals and one of gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, tungsten Or graphite or a graphite intercalation compound. In this specification, magnesium is included in the alkaline earth metal. The same applies to the following description.

  Examples of alloys 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, etc. Can do.

  In the case of configuring an element that extracts light from the cathode E2 side, a transparent conductive electrode can be used as the cathode E2, for example, from a conductive metal oxide such as indium oxide, zinc oxide, tin oxide, ITO, and IZO. Or a thin film made of a conductive organic material such as polyaniline or a derivative thereof, polythiophene or a derivative thereof can be used. Note that the cathode may have a laminated structure of two or more layers.

  The thickness of the cathode E2 is appropriately set in consideration of electric 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.

  Examples of the method for forming the cathode E2 include a vacuum deposition method, a sputtering method, and a laminating method in which a metal thin film is thermocompression bonded.

  Next, the multilayer electron transport layer 14 will be described. As shown in FIG. 1, the multilayer 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. Is a laminated body.

<Electron transport layer>
The electron transport layer 14 a corresponds to the main body portion in the multilayer electron transport layer 14. While the electron transport layer 14a contains an electron transport material, it does not contain the organometallic complex compound contained in the first mixed layer 14b and the second mixed layer 14c described later.

  As the electron transport material, known materials generally used as an electron transport layer can be used. For example, compounds having condensed aryl rings such as naphthalene and anthracene and derivatives thereof, styryl aromatic ring derivatives represented by 4,4-bis (diphenylethenyl) biphenyl, perylene derivatives, perinone derivatives, coumarin derivatives, naphthalimide derivatives Quinolinol complexes such as quinone derivatives such as anthraquinone, naphthoquinone, diphenoquinone, anthraquinodimethane, tetracyanoanthraquinodimethane, phosphorus oxide derivatives, carbazole derivatives, indole derivatives, tris (8-quinolinolato), aluminum (III) And hydroxyazole complexes such as hydroxyphenyloxazole complexes, azomethine complexes, tropolone metal complexes and flavonol metal complexes, compounds having heteroaryl rings with electron-accepting nitrogen Examples include compounds.

  The electron-accepting nitrogen represents a nitrogen atom that forms a multiple bond with an adjacent atom. Since the nitrogen atom has a high electronegativity, the multiple bond also has an electron accepting property. Therefore, a heteroaryl ring having an electron-accepting nitrogen has a high electron affinity. Examples of these compounds having a heteroaryl ring structure having an electron-accepting nitrogen include benzimidazole derivatives, benzthiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyridine derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline. Preferred examples include derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives, naphthyridine derivatives, and phenanthroline derivatives.

  Examples of the method for forming the electron transport layer 14a include a vacuum vapor deposition method, film formation from a solution or a molten state when a low molecular electron transport material is used, and a case where a polymer electron transport material is used. And film formation from a solution or a molten state. When forming a film from a solution or a molten state, a polymer binder may be used in combination.

<First mixed layer>
The first mixed layer 14b is provided in contact with the light emitting layer 13 on the light emitting layer 13 side of the electron transport layer 14a. The first mixed layer 14b is also in contact with the electron transport layer 14a. The first mixed layer 14b is a layer containing an organometallic complex compound together with the electron transporting material included in the electron transporting layer 14a, and the first mixed layer 14b is a mixture of the organometallic complex compound in the composition of the electron transporting layer 14a. Layer. The electron transport material included in the first mixed layer 14b may be the same as the electron transport material exemplified for the electron transport layer 14a.

  The metal ion contained in the organometallic complex compound is preferably one containing at least one of alkali metal ions, alkaline earth metal ions, and rare earth metal ions. In addition, quinolinol, benzoquinolinol, acridinol, phenanthridinol, hydroxyphenyloxazole, hydroxyphenylthiol, hydroxydiaryloxadiazole, hydroxydiarylthiadiazole, hydroxyphenylpyridine, hydroxy are included in the organometallic complex compound. Phenylbenzimidazole, hydroxybenzotriazole, hydroxyfulborane, bipyridyl, phenanthroline, phthalocyanine, porphyrin, cyclopentadiene, β-diketones, azomethines, and derivatives thereof are preferable.

Examples of the organometallic complex compound include any one of the following formulas (1) to (16).

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

  In each organometallic complex compound represented by formula (1) to formula (16), at least one hydrogen atom bonded to the carbon atom constituting the five-membered ring or the six-membered ring is an alkyl group having 1 to 12 carbon atoms. May be substituted. The alkyl group having 1 to 12 carbon atoms is preferably a methyl group, an ethyl group, a propyl group, or a t-butyl group.

  In formulas (1) to (16), the organometallic complex compound is preferably formula (1), formula (2), formula (4), formula (6), formula (7), or formula (9). Formula (1), formula (2) or formula (4) is more preferable.

  Specific examples of the organometallic complex compound include 8-quinolinol lithium, 8-quinolinol sodium, 8-quinolinol potassium, 8-quinolinol rubidium, 8-quinolinol cesium, benzo-8-quinolinol lithium, benzo-8-quinolinol sodium, benzo-8- Quinolinol potassium, benzo-8-quinolinol rubidium, benzo-8-quinolinol cesium, 2-methyl-8-quinolinol lithium, 2-methyl-8-quinolinol sodium, 2-methyl-8-quinolinol potassium, 2-methyl-8-quinolinol rubidium and 2-methyl- An example is 8-quinolinol cesium.

  Among these, as the organometallic complex compound, 8-quinolinol lithium and 8-quinolinol sodium are preferable, and 8-quinolinol sodium is more preferable.

  An example of the mixing ratio of the electron transport material and the organometallic complex compound is as follows. When the mass of the electron transport material is V1, and the mass of the organometallic complex compound is V2, V1: V2 is 1:99 to 99: 1. Yes, preferably 5:95 to 70:30.

  Examples of the method for forming the first mixed layer 14b include a vacuum deposition method, a film formation from a solution or a molten state when a low molecular electron transport material is used, and a high molecular electron transport material is used. In some cases, film formation from a solution or a molten state can be mentioned. When forming a film from a solution or a molten state, a polymer binder may be used in combination. For example, in the vacuum deposition method, the electron transport material and the organometallic complex compound constituting the first mixed layer 14b may be co-deposited.

<Second mixed layer>
Similar to the first mixed layer 14b, the second mixed layer 14c is a layer including an electron transport material and an organometallic complex compound. The second mixed layer 14c may be a layer in which an organometallic complex compound is mixed with the composition of the electron transport layer 14a. The second mixed layer 14c is a layer for improving the electron injection efficiency from the cathode E2, and functions as an electron injection layer.

  The electron transport material contained in the second mixed layer 14c can be the electron transport material exemplified in the description of the electron transport layer 14a. Examples of the organometallic complex compound included in the second mixed layer 14c include the organometallic complex compounds exemplified in the description of the first mixed layer 14b. The electron transport material and the organometallic complex compound included in the second mixed layer 14c may be the same as the electron transport material and the organometallic complex compound included in the first mixed layer 14b.

  The second mixed layer 14c is formed in the same manner as the first mixed layer 14b. In the second mixed layer 14c, the mixing ratio of the electron transport material and the organometallic complex compound is 5 when the mass of the electron transport material is V3 and the mass of the organometallic complex compound is V4. : 95-50: 50.

  The thickness of the multilayer electron transport layer 14 has an optimum value depending on the layer structure of the multilayer electron transport layer 14 and the material used, and may be selected so that the driving voltage and the light emission efficiency are appropriate values. It is necessary to have such a thickness that does not occur. If the thickness is too large, the driving voltage of the element becomes high, which is not preferable. 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 electron transport layer 14 a has a film thickness of, for example, 3 nm to 1 μm, and the first mixed layer 14 b has a film thickness of, for example, 2 nm to 20 nm. The film thickness of the mixed layer 14c is, for example, 2 nm to 20 nm. The first and second mixed layers 14b and 14c are thinner than the electron transport layer 14a. When the first and second mixed layers 14b and 14c are thinner than 2 nm, pin poles tend to be generated. When the thickness is larger than 20 nm, the entire multilayer electron transport layer 14 tends to be thicker. The voltage increases.

  The multilayer electron transport layer 14 can be formed by sequentially forming the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c on the light emitting layer 13. The first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c are preferably formed by the same film forming method from the viewpoint of improving manufacturing efficiency.

  The first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c included in the multilayer electron transport layer 14 all include an electron transport material. Therefore, the multilayer electron transport layer 14 is, for example, an electron transport layer in which the entire multilayer electron transport layer is made of an electron transport material, and an organic metal complex compound is locally applied to the light emitting layer side interface and the cathode layer side interface. Corresponds to the doped configuration. Here, “dope” means intentionally mixing two or more different materials.

  The electron transport material included in the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c may be the same material, but the electron transport material included in the first mixed layer 14b, the electron transport layer 14a, and the second mixed layer 14c. May be different. In that case, the electron transport material which each of the 1st mixed layer 14b, the electron transport layer 14a, and the 2nd mixed layer 14c has can use the electron transport material illustrated in description of the electron transport layer 14a, for example. The first mixed layer 14b and the second mixed layer 14c may not be made of the same material.

  The organic EL element 1 is manufactured by sequentially 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 a substrate P. Since the formation method of each component on the board | substrate P is as having mentioned above, description is abbreviate | omitted.

  In the organic EL element 1, by providing the multilayer electron transport layer 14, the first mixed layer 14b is provided between the light emitting layer 13 and the electron transport layer 14a. Since the 1st mixed layer 14b has an organometallic complex compound in addition to an electron transport material, the element lifetime of the organic EL element 1 becomes long, and drive stability improves. This is because, for example, it is considered that the deterioration of the electron transport layer due to the accumulated charge is suppressed by the organometallic complex compound.

  Since the multilayer electron transport layer 14 includes the second mixed layer 14c and the second mixed layer 14c includes the organometallic complex compound, the electron injection efficiency from the cathode E2 to the electron transport layer 14a is improved. As a result, the drive voltage can be further reduced.

(Second Embodiment)
The organic EL element 2 according to the second embodiment shown in FIG. 2 includes a multilayer electron transport layer 14 </ b> A instead of the multilayer electron transport layer 14. The configuration of the organic EL element 2 is the same as that 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 a metal layer 14d is provided between the first mixed layer 14b and the electron transport layer 14a.

  The metal layer 14d is stacked 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 as the metal layer 14d are lithium, sodium, potassium, rubidium, cesium, and chromium, and examples of the alkaline earth metal are magnesium, calcium, strontium, barium, and radium. Among these, magnesium is preferable. An example of the thickness of the metal layer 14d is 0.5 nm to 10 nm. The metal layer 14d can be formed by, for example, a vacuum evaporation method.

  Since the organic EL element 2 is the same as the configuration of the organic EL element 1 except that the organic EL element 2 includes the metal layer 14d, the organic EL element 2 has at least the same effects as the organic EL element 1. And by having the metal layer 14d, the drive voltage is lowered and the device life is further improved. As a result, the driving stability of the organic EL element 2 is further improved.

  Although various embodiments of the present invention have been described above, the present invention is not limited to the illustrated various embodiments, but is shown by the scope of the claims and all within the scope and meaning equivalent to the scope of the claims. Is intended to be included.

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

The organic EL element should just have a multilayer type electron carrying layer between the light emitting layer 13 and the cathode E2. The example of the layer structure which an organic EL element can take is shown. In the following description, the configurations of the first and second embodiments may be included.
a) Anode / hole injection layer / light emitting layer / multilayer type electron transport layer / cathode b) Anode / hole injection layer / hole transport layer / light emitting layer / multilayer type electron transport layer / cathode c) Anode / light emitting layer / Multi-layer type electron transport layer / cathode The symbol “/” means that the layers on both sides of the symbol “/” are joined to each other.

In a) to c), the “multilayer electron transport layer” means
(i) First laminated structure: first mixed layer / electron transport layer,
(ii) Second laminated structure: first mixed layer / electron transport layer / second mixed layer,
(iii) Third laminated structure: first mixed layer / metal layer / electron transport layer, and
(iv) Fourth laminated structure: first mixed layer / metal layer / electron transport layer / second mixed layer,
Means either.

  In the case of an organic EL element in which the second mixed layer is included in the multilayer electron transport layer as in the second stacked structure and the fourth stacked structure, the organic EL element has an electron injection layer. To do.

  When at least one of the layers constituting the multilayer electron transport layer is a layer having a function of blocking hole transport, the layer having a function of blocking hole transport is a hole blocking layer and Sometimes called.

  The fact that the hole blocking layer has a function of blocking hole transport can produce, for example, an organic EL element that allows only hole current to flow, and can confirm the blocking effect by reducing the current value.

  In addition, in a) and b), when the hole injection layer and / or the hole transport layer have a function of blocking electron transport, these layers may be referred to as an electron block layer. The fact that the electron blocking layer has a function of blocking electron transportation can be confirmed, for example, by producing an organic EL element that allows only electron current to flow, and confirming the effect of blocking electron transportation by reducing the measured current value. . In addition to the hole injection layer and / or the hole transport layer, an electron blocking layer may be provided between the anode and the light emitting layer.

Furthermore, the organic EL element may have a single light emitting layer or two or more light emitting layers. In any one of the layer configurations of a) to c) above, when the laminate disposed between the anode and the cathode is “structural unit A”, the organic EL element having two light emitting layers is provided. Examples of the structure include the layer structure shown in the following d). The two (structural unit A) layer structures may be the same or different.
d) Anode / (structural unit A) / charge generation layer / (structural unit A) / cathode

  Here, the charge generation layer is a layer that generates holes and electrons by applying an electric field. Examples of the charge generation layer include a thin film made of vanadium oxide, indium tin oxide (abbreviated as ITO), molybdenum oxide, or the like.

Assuming that “(structural unit A) / charge generation layer” is “structural unit B”, examples of the configuration of the organic EL element having three or more light-emitting layers 13 include the layer configuration shown in e) below.
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” has (structural unit B) stacked in x stages. Represents a laminated body. Further, a plurality of (structural unit B) layer structures may be the same or different.

  An organic EL element may be configured by directly laminating a plurality of light emitting layers without providing a charge generation layer.

  In the description so far, the example in which the anode is disposed on the substrate side has been described, but the cathode may be disposed on the substrate side. In this case, for example, when each of the organic EL elements a) to e) is produced on the substrate, the layers may be laminated on the substrate in order from the right side of the cathode (each configuration a) to e).

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Example 1]
As shown in FIG. 1 as Example 1, 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 are sequentially stacked on a substrate. An organic EL device was manufactured. The organic EL element of Example 1 is referred to as organic EL element A1. In Example 1, the organic EL element A1 is sealed with glass. Hereinafter, the manufacturing method of organic EL element A1 is demonstrated concretely.

<Substrate and anode>
A glass substrate was prepared as a substrate for the organic EL element A1. An ITO thin film was formed in a predetermined pattern as an anode on a glass substrate. The ITO thin film is formed by a sputtering method, and the film thickness is 45 nm. The glass substrate on which the ITO thin film was formed was ultrasonically cleaned with an organic solvent, an alkaline detergent and ultrapure water, then boiled with an organic solvent for 10 minutes and dried. Next, ultraviolet ozone treatment was performed for about 15 minutes on the surface on which the ITO thin film was formed using an ultraviolet ozone (UV-O3) apparatus.

<Hole injection layer>
A hole injection material combined with an organic material having a charge transporting property and an electron accepting material was applied onto the ITO thin film by a spin coating method to form a coating film having a thickness of 35 nm. Hereinafter, the hole injection material used in Example 1 is referred to as a hole injection material α1. In the air, the coating film was dried on a hot plate to form a hole injection layer. In the drying using a hot plate, the film was first dried at 50 ° C. for 4 minutes, and further dried at 230 ° C. for 15 minutes.

<Hole transport layer>
A hole transport material, which is a polymer material, and xylene were mixed to obtain a composition for forming a hole transport layer having a solid (hole transport material) concentration of 0.6% by weight. Hereinafter, the hole transport material used in Example 1 is referred to as a hole transport material α2. The obtained composition for forming a hole transport layer was applied onto the hole injection layer by a spin coating method to obtain a coating film having a thickness of 20 nm. The glass substrate provided with this coating film was heated at 180 ° C. for 60 minutes in a nitrogen atmosphere (inert atmosphere) using a hot plate to evaporate the solvent, and then naturally cooled to room temperature. A transport layer was obtained.

<Light emitting layer>
The light-emitting conjugated polymer material and xylene were mixed to obtain a composition for forming a light-emitting layer in which the concentration of the light-emitting conjugated polymer material was 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 α3. The obtained composition for forming a light emitting layer was applied onto the hole transport layer by a spin coating method to obtain a coating film having a film thickness of 65 nm. The glass substrate provided with this coating film was heated at 150 ° C. for 10 minutes in a nitrogen atmosphere (inert atmosphere) using a hot plate to evaporate the solvent, and then naturally cooled to room temperature. Got.

<First mixed layer>
The glass substrate on which the light emitting layer was formed was transferred to a vapor deposition chamber, and a first mixed layer was formed on the light emitting layer. Specifically, the vacuum in the vapor deposition chamber is evacuated until the vacuum level becomes 1.0 × 10 ⁻⁵ Pa or less, and the electron transport material and the organometallic complex compound are co-deposited on the light emitting layer by a vacuum vapor deposition method. A first mixed layer in which the thickness was 5 nm and the electron transport material and the organometallic complex compound were mixed was formed. Hereinafter, the electron transport material and the organometallic complex compound used in Example 1 are referred to as an electron transport material α4 and an organometallic complex compound α. The electron transport material α4 is TR-E314 manufactured by Toray Industries, Inc. The organometallic complex compound α5 is 8-quinolinol sodium (Naq). The deposition rates of the electron transport material α4 and the organometallic complex compound α5 were each 0.3 Å / s. That is, the mass ratio of the electron transport material α4 and the organometallic complex compound α5 in the first mixed layer is 50:50.

<Electron transport layer>
After forming the first mixed layer, an electron transport layer was formed on the first mixed layer in the same vapor deposition chamber. Specifically, the electron transport material α4 was deposited on the first mixed layer by a vacuum deposition method to form an electron transport layer having a thickness of 60 nm. The vapor deposition rate of the electron transport material α4 was 0.5 Å / s.

<Second mixed layer>
After forming the electron transport layer, a second mixed layer was formed on the electron transport layer in the same vapor deposition chamber. Specifically, the electron transport material α4 and the organometallic complex compound α5 are co-deposited on the electron transport layer by a vacuum deposition method, the film thickness is 5 nm, and the electron transport material α4 and the organometallic complex compound α5 are mixed. A second mixed layer was formed. The deposition rates of the electron transport material α4 and the organometallic complex compound α5 were each 0.3 Å / s. That is, the mass ratio of the electron transport material α4 and the organometallic complex compound α5 in the second mixed layer is 50:50.

<Cathode>
After forming the second mixed layer, the cathode was formed in the same deposition chamber. Specifically, magnesium and silver are co-evaporated on the second mixed layer by a vacuum deposition method to form a cathode a having a thickness of 20 nm, and then aluminum is deposited on the cathode a by a vacuum deposition method. A cathode b having a thickness of 100 nm was 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 were stacked on the second mixed layer was formed.

<Glass sealing>
After forming the cathode, the glass substrate after forming the cathode is transferred from the vapor deposition chamber to the sealing treatment chamber without being exposed to the atmosphere, and sealed by applying a UV curable resin around it in a nitrogen atmosphere (inert atmosphere). The glass and the glass substrate conveyed from the vapor deposition chamber were bonded together and irradiated with UV light to cure the UV curable resin, and the organic EL element A1 was sealed with glass.

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

The element lifetime was evaluated based on LT80 expressed by the time from the start of driving until the luminance decreased to 80, assuming that the luminance at the start of driving was 100. The element lifetime was measured by driving the organic EL element A1 with a constant current of 10 mA / cm ² . The drive voltage is a voltage when driving the organic EL element A1 with a constant current of 10 mA / cm ² . The current efficiency is a value when the luminance is 1000 cd / m ² (that is, 1000 nit).

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

[Comparative Example 1]
As Comparative Example 1, an organic EL element of Comparative Example 1 was produced in which an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode were sequentially laminated on a substrate. It is called organic EL element B1. The configuration of the organic EL element B1 has the same configuration as that of the organic EL element A1 of Example 1 except that the first and second mixed layers are not included and the film thickness of the electron transport layer is 70 nm. That is, in Comparative Example 1, the materials and thicknesses of the substrate, the anode, the hole injection layer, the hole transport layer, the light emitting layer, and the cathode, and the formation methods thereof are the same as those in Example 1. Therefore, a method for 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 forming the light emitting layer, the glass substrate (substrate) on which the light emitting layer was formed was transferred to the vapor deposition chamber. Then, the vacuum in the vapor deposition chamber is evacuated until the vacuum level becomes 1.0 × 10 ⁻⁵ Pa or less, and the electron transport material α4 is vapor-deposited on the light emitting layer by a vacuum vapor deposition method to form an electron transport layer having a thickness of 70 nm. did. The vapor deposition rate of the electron transport material α4 was 0.5 Å / s.

  Also in the comparative example 1, the organic EL element B1 manufactured similarly to Example 1 was glass-sealed.

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

  As a result, in Comparative Example 1, the element lifetime (LT80) was 0.1 hour, the current efficiency was 1.0 cd / A, and the drive voltage was 6.1V.

[Comparative Example 2]
As Comparative Example 2, an organic EL device in which an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, a second mixed layer, and a cathode were sequentially laminated on a substrate was manufactured. The organic EL element is referred to as organic EL element B2. The structure of the organic EL element B2 is the same as that of the organic EL element A1 of Example 1 except that the first mixed layer is not provided and the film thickness of the electron transport layer is 65 nm. In Comparative Example 2, the materials and thicknesses of the substrate, the anode, the hole injection layer, the hole transport layer, the light emitting layer, the second mixed layer, and the cathode, and the formation methods thereof are the same as those in Example 1. And the formation method of the electron carrying layer of the comparative example 2 is the same as that of the case of the comparative example 1 except the point which sets a film thickness to 65 nm.

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

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

[Comparison of Example 1 and Comparative Examples 1 and 2]
Table 1 shows the measurement results of the element lifetime, current efficiency, and drive voltage of the organic EL elements A1, B1, and B2 of Example 1 and Comparative Examples 1 and 2 described above.

  As can be seen from Table 1, in Example 1 in which the first mixed layer was provided, a longer element lifetime could be obtained at substantially the same current efficiency and driving voltage as compared with Comparative Examples 1 and 2. It can be understood that In particular, by comparing Example 1 and Comparative Example 2, it is understood that such a difference in element lifetime occurs due to the influence of the first mixed layer. Therefore, it is understood that the driving stability of the organic EL element is improved by providing the first mixed layer containing the electron transport material and the organometallic complex compound.

  Next, as shown in FIG. 2, the verification result of the function and 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, an anode, a hole injection layer, a hole transport layer, a light emitting layer, a first mixed layer, a metal layer, an electron transport layer, a second mixed layer, and a cathode are formed on a substrate. Were manufactured in order. The organic EL element of Example 2 is referred to as organic EL element A2. In Example 2, the organic EL element A2 is sealed with glass in the same manner as in Example 1. The manufacturing method of organic EL element A2 is demonstrated concretely.

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

<Hole injection layer>
A hole injection layer was formed in the same manner as in Example 1 except that the thickness of the coating film formed by applying the ink containing the hole injection material α1 on the ITO thin film by spin coating was set to 80 nm. .

<Hole transport layer>
In the same manner as in Example 1, a hole transport layer was formed on the hole injection layer.

<Light emitting layer>
A red light-emitting conjugated polymer material and xylene were mixed to obtain a composition for forming a light-emitting layer in which the concentration of the red light-emitting conjugated polymer material was 2.8%. Hereinafter, the red light-emitting conjugated polymer material used in Example 2 is referred to as a red light-emitting conjugated polymer material α6. The obtained composition for forming a light emitting layer was applied onto the hole transport layer by a spin coating method to obtain a coating film having a thickness of 160 nm. The glass substrate provided with this coating film was heated at 150 ° C. for 10 minutes in a nitrogen atmosphere (inert atmosphere) using a hot plate to evaporate the solvent, and then naturally cooled to room temperature. Got.

<First mixed layer>
In the same manner as in Example 1, a first mixed layer was formed on the light emitting layer.

<Metal layer>
After forming the first mixed layer, magnesium was deposited on the first mixed layer by a vacuum deposition method in a deposition chamber in which the first mixed layer was formed, thereby forming a metal layer having a thickness of 2 nm. The deposition rate of magnesium was 0.5 Å / s.

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

<Second mixed layer>
After the formation of the electron transport layer, the electron transport was carried out in the same manner as in Example 1 except that the vapor deposition rates of the electron transport material α4 and the organometallic complex compound α5 were 0.1 Å / s and 0.9 Å / s, respectively. A second mixed layer was formed on the layer. That is, the mass ratio of the electron transport material α4 and the organometallic complex compound α5 in the second mixed layer is 10:90.

<Cathode>
After forming the second mixed layer, the cathode was formed in the same deposition chamber. Specifically, magnesium is deposited on the second mixed layer by a vacuum deposition method to form a cathode a having a thickness of 2 nm, and then silver is deposited on the cathode a by a vacuum deposition method to obtain a thickness of 18 nm. The cathode b was formed. Subsequently, aluminum was deposited on the cathode b by a vacuum deposition method to form a cathode c having a thickness of 100 nm. That is, as the cathode of the organic EL element A2, a cathode having a three-layer structure in which a cathode a having a thickness of 2 nm, a cathode b having a thickness of 18 nm, and a cathode c having a thickness of 100 nm are stacked on the second mixed layer. Formed.

<Glass sealing>
After forming the cathode, the organic EL element A2 was sealed with glass in the same manner as in Example 1.

  Since the organic EL element A2 includes the red light emitting conjugated polymer material α6 in the light emitting layer, the organic EL element A2 is a red light emitting element.

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

  In the measurement result of the organic EL element A2, the element lifetime (LT80) was 156.1 hours, the current efficiency was 8.2 cd / A, and the drive voltage was 6.8V.

(Example 3)
As Example 3, an organic EL element was produced and sealed with glass in the same manner as in Example 2 except that the metal layer was not provided. The organic EL element of Example 3 is referred to as organic EL element A3.
Similarly to the organic EL element A2, the organic EL element A3 is also a red light emitting element.

  With respect to the manufactured organic EL element A3, the element life, current efficiency, and driving voltage were measured under the same conditions as in Example 2. In Example 3, the element lifetime (LT80) was 52.0 hours, the current efficiency was 6.4 cd / A, and the drive voltage was 11.5V.

[Comparison of Example 2 and Example 3]
Table 2 shows the measurement results of the element lifetime, current efficiency, and drive voltage in Examples 2 and 3 described above.

  As can be understood from Table 2, Example 2 provided with the metal layer can be driven at a lower driving voltage and can realize a longer device life as compared with Example 3 without the metal layer. Is understood.

Example 4
In Example 4, an organic EL element having the same configuration as in Example 2 was produced except that the configurations of the hole injection layer and the light emitting layer were different, and sealed with glass as in Example 2. . The organic EL element of Example 4 is referred to as organic EL element A4. A method for forming the hole injection layer and the light emitting layer in the organic EL element A4 will be described.

<Hole injection layer>
A 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 α1 on the ITO thin film was 85 nm.

<Light emitting layer>
A green light-emitting conjugated polymer material and xylene were mixed to obtain a light emitting layer forming composition having a green light-emitting conjugated polymer material concentration of 2.2%. Hereinafter, the green light-emitting conjugated polymer material used in Example 4 is referred to as green light-emitting conjugated polymer material α7. The obtained composition for forming a light emitting layer was applied onto the hole transport layer by a spin coating method to obtain a coating film having a film thickness of 85 nm. The glass substrate provided with this coating film was heated at 150 ° C. for 10 minutes in a nitrogen atmosphere (inert atmosphere) using a hot plate to evaporate the solvent, and then naturally cooled to room temperature. Got.

  As described above, since the light emitting layer includes the green light emitting conjugated polymer material α7, 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 lifetime was evaluated by LT80 as in Example 1. The element lifetime was measured with the element driven at a constant current of 25 mA / cm ² . The current efficiency is a value when the luminance is 100 cd / m ² (that is, 100 nit). The driving voltage is a value when the current density is 10 mA / cm ² .

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

(Example 5)
As Example 5, an organic EL element was produced and sealed with glass in the same manner as in Example 4 except that the metal layer was not provided. The organic EL element of Example 5 is referred to as organic EL element A5.
The organic EL element A5 is also a green light emitting element like the organic EL element A4.

  With respect to the manufactured organic EL element A5, the element life, current efficiency, and drive voltage were measured under the same conditions as in Example 4. In Example 5, the element lifetime (LT80) was 1.7 hours, the current efficiency was 12.9 cd / A, and the drive voltage was 8.9V.

[Comparison of Example 4 and Example 5]
Table 3 shows the measurement results of element lifetime, current efficiency, and drive voltage in Examples 4 and 5 described above.

  As can be seen from Table 3, Example 4 provided with the metal layer has a lower current efficiency than Example 5 without the metal layer, but can be driven at a lower drive voltage. It will be appreciated that longer device lifetimes can be achieved.

(Example 6)
In Example 6, an organic EL element having the same configuration as in Example 2 was manufactured except that the configurations of the hole injection layer and the light emitting layer were different, and sealed with glass. The organic EL element of Example 6 is referred to as organic EL element A6. A method for forming the hole injection layer and the light emitting layer in the organic EL element A6 will be described.

<Hole injection layer>
A 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 α1 on the ITO thin film was 35 nm.

<Light emitting layer>
The blue light-emitting conjugated polymer material α3 and xylene were mixed to obtain a composition for forming a light-emitting layer in which the concentration of the blue light-emitting conjugated polymer material α3 was 1.3%. The obtained composition for forming a light emitting layer was applied onto the hole transport layer by a spin coating method to obtain a coating film having a film thickness of 65 nm. The glass substrate provided with this coating film was heated at 150 ° C. for 10 minutes in a nitrogen atmosphere (inert atmosphere) using a hot plate to evaporate the solvent, and then naturally cooled to room temperature. Got.

  As described above, since the light emitting layer contains the blue light emitting conjugated polymer material α3, 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 lifetime was evaluated by LT80 as in Example 1. The element lifetime was measured in a state where the element was driven at a constant current of 80 mA / cm ² . The current efficiency is a value when the luminance is 100 cd / m ² (that is, 100 nit). The driving voltage is a value when the current density is 10 mA / cm ² .

  In the organic EL element A6, the element lifetime (LT80) was 11.8 hours, the current efficiency was 1.7 cd / A, and the drive voltage was 4.9 V.

(Example 7)
As Example 7, an organic EL element was produced and sealed with glass in the same manner as in Example 6 except that the metal layer was not provided. The organic EL element of Example 7 is referred to as organic EL element A7.
The organic EL element A7 is also a blue light emitting element like the organic EL element A6.

  With respect to the manufactured organic EL element A7, the element life, current efficiency, and driving voltage were measured under the same conditions as in Example 6. In Example 7, the element lifetime (LT80) was 8.0 hours, the current efficiency was 1.7 cd / A, and the drive voltage was 5.1V.

[Comparison of Example 6 and Example 7]
Table 4 shows the measurement results of the element lifetime, current efficiency, and drive voltage in Examples 6 and 7 described above.

  As can be understood from Table 4, Example 6 provided with the metal layer can be driven at a lower driving voltage and can realize a longer element lifetime as compared with Example 7 without the metal layer. Is understood.

  From the results of Tables 2 to 4, it is possible to extend the life of the element by further providing a metal layer in any of the red light emitting element, the green light emitting element and the blue light emitting element, and the metal layer improves driving stability. It was confirmed that it contributed to

  DESCRIPTION OF SYMBOLS 1, 2 ... Organic EL element, 13 ... Light emitting layer, 14, 14A ... Multilayer type electron transport layer, 14a ... Electron transport layer, 14b ... 1st mixed layer (light emitting layer side mixed layer), 14c ... 2nd mixed layer ( Cathode side mixed layer), 14d ... metal layer, E1 ... anode, E2 ... cathode.

Claims (5)

An organic EL device having an anode, a cathode, and a light emitting layer provided between the anode and the cathode,
A multilayer electron transport layer provided between the light emitting layer and the cathode;
The multilayer electron transport layer is
An electron transport layer comprising an electron transport material;
A light emitting layer side mixed layer provided between and in contact with the light emitting layer between the electron transport layer and the light emitting layer;
Have
The light emitting layer side mixed layer contains an organometallic complex compound together with an electron transport material,
Organic EL element. The multilayer electron transport layer is
A cathode-side mixed layer provided in contact with the electron-transporting layer on the cathode side from the electron-transporting layer;
The cathode-side mixed layer contains an organometallic complex compound together with an electron transport material.
The organic EL element according to claim 1. The multilayer electron transport layer further includes a metal layer between the light emitting layer side mixed layer and the electron transport layer,
The organic EL element according to claim 1 or 2. The light emitting layer side mixed layer has a thickness of 2 nm to 20 nm.
The organic EL element as described in any one of Claims 1-3. The organometallic complex compound contained in the light emitting layer-side mixed layer is 8-quinolinol sodium.
The organic EL element as described in any one of Claims 1-4.

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