JP2011204646A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element capable of attaining longer lifetime and improving the light-emitting efficiency and lowering of the driving voltage.SOLUTION: The organic electroluminescent element includes a substrate 10, an anode 1 formed on one surface of the substrate 10, an organic EL layer 8 formed on an opposite side to a substrate 10 side of the anode 1 and containing at least a light-emitting layer 5, and a cathode 2 formed on an opposite side to an anode 1 side of the organic EL layer 8. The cathode 2 is constituted of a laminated film of a first transparent conductive film 2a; a light-transmitting thin film 2b made of a metal thin film; and a second transparent conductive film 2c, which is laminated in the thickness direction of the organic EL layer 8, and the metal thin film is formed with two kinds or more of metals selected from among a group of silver, indium, gold, magnesium, and tin.

Description

  The present invention relates to an organic electroluminescence element that can be used in, for example, an illumination light source, a backlight for a liquid crystal display, a flat panel display, and the like.

  As an organic light-emitting element called an organic electroluminescence element, for example, on one surface side of a transparent substrate, a transparent electrode (transparent conductive film) serving as an anode, a hole transport layer, a light-emitting layer (organic light-emitting layer), electron injection One having a layered structure of a layer and an electrode serving as a cathode is known. In the organic electroluminescence device having such a laminated structure, by applying a voltage between the anode and the cathode, electrons injected into the light emitting layer through the electron injection layer and the light emitting layer through the hole transport layer The holes injected into the light are recombined in the light emitting layer to emit light, and the light emitted from the light emitting layer is extracted through the transparent electrode and the transparent substrate.

  An organic electroluminescence element is a self-luminous light-emitting element, has a relatively high-efficiency light-emitting characteristic, and can emit light in various color tones, such as a display device (for example, It is expected to be applied as a light emitter such as a flat panel display) or a light source (for example, a backlight or an illumination light source for a liquid crystal display device), and has already been put into practical use in part.

  Here, the basic laminated structure of the organic electroluminescence element is an anode / light emitting layer / cathode laminated structure, but in addition, an anode / hole transport layer / light emitting layer / electron transport layer / cathode laminated structure, anode / Laminated structure of hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode, anode / hole injection layer / light emitting layer / electron transport layer / electron injection layer / laminated structure of anode, anode / hole injection layer / light emitting layer Various laminated structures such as a laminated structure of / electron injection layer / cathode have been proposed.

  By the way, in an organic electroluminescence element, a cathode is used as a transparent electrode (transparent cathode), and a top emission type organic electroluminescence element that takes out light emitted from a light emitting layer not from the substrate side but from the cathode side, A double-sided light emitting organic electroluminescence element that uses both as transparent electrodes and extracts light from both sides in the thickness direction has also been researched and developed (Patent Documents 1 and 2). Further, as an application of this double-sided light emitting organic electroluminescence element, a new device is considered in which added value is increased by combining a solar cell, a display, a light source, and the like.

  Patent Document 1 includes an electron injection electrode layer in which an organic layer including an organic light emitting layer is interposed between an anode and a cathode, and the cathode is formed of a metal having a work function of 3.8 eV or less and is in contact with the organic layer; An organic electroluminescence element composed of an amorphous transparent conductive film formed on an injection electrode layer is disclosed.

  In Patent Document 2, a light emitting layer is provided between an anode and a cathode, both the anode and the cathode have translucency, and the cathode is provided with a thickness of 10 nm or less provided on the light emitting layer side. An organic electroluminescence element is disclosed which is composed of a conductor layer made of a metal or alloy having a function of 4 eV or less and a transparent electrode made of an IZO film provided on the side opposite to the light emitting layer side. Here, in Patent Document 2, an alkali metal, aluminum, silver, or the like is exemplified as a metal having a work function of 4 eV or less.

Japanese Patent Laid-Open No. 10-162959 JP-A-10-125469

  By the way, when an organic electroluminescence element having a transparent cathode on the side far from the substrate is used as a large area planar light-emitting device for illumination, it is necessary to flow a larger current in order to light it with high luminance. However, in such an organic electroluminescence element, it is necessary to form a cathode on the organic layer, and it is necessary to lower the temperature of the substrate at the time of film formation as compared with the case of forming the cathode on a glass substrate. The sheet resistance of the transparent cathode is larger than the sheet resistance of the anode and the cathode sheet resistance using a metal film, the potential gradient at the cathode is increased, and the distance from the power supply terminal connected to the cathode is increased. As the distance increases, the voltage applied between the anode and the cathode increases, and the in-plane variation in luminance increases.

  On the other hand, in the organic electroluminescence elements disclosed in Patent Document 1 and Patent Document 2, the sheet resistance of the cathode can be reduced.

  However, in the organic electroluminescence element of Patent Document 1, since the cathode includes an electron injection electrode layer in contact with the organic layer (organic EL layer), the metal of the electron injection electrode layer diffuses into the light emitting layer and emits light. The layer may be damaged, resulting in a decrease in luminous efficiency and a shortened lifetime.

  Further, in the organic electroluminescence element of Patent Document 2, since the cathode includes a conductor layer in contact with the light emitting layer, the metal of the conductor layer diffuses to the inside of the light emitting layer, and the light emitting layer is damaged. There is a possibility that the luminous efficiency is lowered and the lifetime is shortened.

  In addition, when an alkali metal is employed as the metal of the electron injection electrode layer in the organic electroluminescence element of Patent Document 1, depending on the method for forming the amorphous transparent conductive film, the constituent elements of the amorphous transparent conductive film There is a concern that one of oxygen and the metal of the electron injection electrode layer reacts and the electron injection property of the electron injection electrode layer is lowered.

  In addition, when an alkali metal is used as the metal of the conductor layer in the organic electroluminescence element of Patent Document 2, oxygen that is one of the constituent elements of the IZO film and the conductor layer may be used depending on the method of forming the IZO film. There is a concern that this metal reacts and the electron injection property of the conductor layer is lowered.

  In addition, as in Patent Documents 1 and 2, when the layer in contact with the organic layer in the cathode is formed of an alkali metal, the electron injection performance is not always sufficient, and further improvement in luminous efficiency and low driving voltage are achieved. Is desired.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide an organic electroluminescence element capable of extending the lifetime, improving the light emission efficiency and reducing the drive voltage. Is.

  The organic electroluminescence element of the present invention includes a substrate, an anode formed on one surface side of the substrate, an organic EL layer formed on the anode opposite to the substrate side and including at least a light emitting layer, and the organic A light-transmitting thin film comprising a first transparent conductive film and a metal thin film laminated in the thickness direction of the organic EL layer. And the second transparent conductive film, wherein the metal thin film is made of two or more kinds of metals selected from the group consisting of silver, indium, gold, magnesium, and tin.

  In this organic electroluminescence element, it is preferable that the metal thin film contains a constituent element made of a metal of the first transparent conductive film.

  In the organic electroluminescence device of the present invention, the lifetime can be extended, the luminous efficiency can be improved, and the driving voltage can be lowered.

It is a schematic sectional drawing of the organic electroluminescent element of embodiment.

  As shown in FIG. 1, the organic electroluminescence device of this embodiment is arranged between an anode 1 and a cathode 2 in order from the anode 1 side, a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, and an electron transport layer. 6. An electron injection layer 7 is provided. Here, in this organic electroluminescence element, the anode 1 is laminated on one surface side of the substrate 10, and the cathode 2 faces the anode 1 on the side opposite to the substrate 10 side in the anode 1. In this organic electroluminescence element, the substrate 10 is configured by a transparent substrate (translucent substrate), the anode 1 is configured by a transparent electrode, and the cathode 2 is configured to be transparent to the light from the light emitting layer 5, The other surface of the substrate 10 and the surface opposite to the light emitting layer 5 side of the cathode 2 are used as the light emitting surface.

  The light-transmitting substrate constituting the substrate 10 is not limited to a colorless and transparent substrate, and may be a substrate that is slightly colored. Here, a glass substrate such as a soda lime glass substrate or a non-alkali glass substrate is used as the translucent substrate constituting the substrate 10, but is not limited to a glass substrate, for example, polyester, polyolefin, polyamide resin, epoxy A plastic film or a plastic substrate formed of a resin, a fluorine-based resin, or the like may be used. Here, the glass substrate may be ground glass. Further, the substrate 10 may be provided with light diffusibility by containing particles, powder, bubbles, or the like having a refractive index different from that of the base material of the substrate 10 in the substrate 10. Further, when light is emitted without passing through the substrate 10, the substrate 10 does not necessarily have optical transparency, and any light-emitting characteristics, life characteristics, etc. of the organic electroluminescence element are not impaired. What was formed with the material can be used. In particular, in order to reduce the temperature rise due to heat generation of the organic electroluminescence element during energization, the substrate 10 is formed of a material having higher thermal conductivity than glass or plastic (for example, a metal substrate, enamel substrate, If an aluminum nitride substrate or the like is used, high brightness and long life can be achieved by improving heat dissipation.

  Here, the anode 1 is an electrode for injecting holes into the light emitting layer 5, and it is preferable to use an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function. (Highest Occupied Molecular Orbital) It is preferable to use a work function of 4 eV or more and 6 eV or less so that the difference from the level does not become too large. Examples of the electrode material of the anode 1 include copper iodide, ITO, tin oxide, zinc oxide, and IZO, conductive polymers such as PEDOT and polyaniline, and conductive polymers doped with any acceptor. A conductive light-transmitting material such as carbon nanotube can be given. Here, the anode 1 may be formed as a thin film on the one surface side of the substrate 10 by vacuum deposition, sputtering, coating, or the like. Further, if a light-transmitting substrate having conductivity such as an ITO substrate is used as the anode 1, the above-described substrate 10 is not particularly required.

  In order to transmit the light emitted from the light emitting layer 5 through the anode 1 and radiate the light to the outside, the light transmittance of the anode 1 is preferably set to 70% or more. Further, the sheet resistance of the anode 1 is preferably several hundred Ω / □ or less, and particularly preferably 100 Ω / □ or less. Here, the film thickness of the anode 1 varies depending on the material in order to control the characteristics such as light transmittance and sheet resistance of the anode 1 as described above, but is set within a range of 500 nm or less, preferably 10 to 200 nm. Is good.

  The material used for the hole injection layer 3 can be formed using a hole injection organic material, a metal oxide, a so-called acceptor organic material or inorganic material, a p-doped layer, or the like. Examples of the hole-injecting organic material include a material having a hole transport property, a work function of about 5.0 to 6.0 eV, and a strong adhesiveness with the anode 1. Examples thereof include CuPc and starburst amine. The hole-injecting metal oxide is a metal oxide containing any of molybdenum, rhenium, tungsten, vanadium, zinc, indium, tin, gallium, titanium, and aluminum, for example. In addition, an oxide of a plurality of metals containing any one of the above metals, such as indium and tin, indium and zinc, aluminum and gallium, gallium and zinc, and titanium and niobium, instead of an oxide of only one kind of metal It may be. In this case, the oxidation number of each metal and the mixing ratio of a plurality of metals can be arbitrarily set so that the film quality, thermal stability, and electrical characteristics of the metal oxide are within preferable ranges. The hole injection layer made of these materials may be formed by a dry process such as vapor deposition or transfer, or by a wet process such as spin coating, spray coating, die coating, or gravure printing. It may be a film.

An acceptor-based organic material or inorganic material is an electron-accepting substance, for example, an organic substance having fluorine, a cyano group, or boron in the molecule, a Lewis acid in the molecule, a Lewis acid, Substances forming a complex with an acid, for example, F ₄ TCNQ (tetrafluorotetracyanoquinodimethane), TCNQ (tetracyanoquinodimethane), TTN (tetrathianaphthacene), HAT-CN ₆ ( Hexaazatriphenylene hexacarboxylic nitrile), DDQ (dichlorodicyanoquinone), CF ₂ TCNQ (difluoromethyltetracyanoquinodimethane), TBPAH (tris (4-bromophenyl) aluminum hexachloroantimonysan), and some fluorescent dyes And so on. Some of these materials are generally known up to abbreviated names, but other materials can be suitably used without particular limitation as long as they have equivalent properties. In addition, the above-described metal oxides, so-called Lewis acids such as iron chloride, iron bromide, copper iodide, and other acids, and phosphoric acid can be used.

  The p-doped layer refers to hole injection or other organic materials such as triarylamine derivatives (NPD, TPD, 2-TANTA, etc.), biphenyl derivatives, anthracene derivatives, naphthalene derivatives, and other aromatic derivatives, aniline. A derivative, a thiophene derivative, or the like mixed with the above-described acceptor-based material that accepts electrons from the material, or partially contained. The mixing ratio of the material that accepts electrons from the organic material to the organic material is appropriately set according to the type of the material, but is preferably in the range of 0.1 to 80 mol%, and more preferably 1 to 50 mol%. The thickness of the hole injection layer 3 is not particularly limited, but is preferably set in the range of about 1 to 100 nm.

  Moreover, the material used for the hole transport layer 4 can be selected from the group of compounds having hole transport properties, for example. Examples of this type of compound include 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD), N, N′-bis (3-methylphenyl)-(1 , 1′-biphenyl) -4,4′-diamine (TPD), 2-TNATA, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (MTDATA) 4,4′-N, N′-dicarbazole biphenyl (CBP), spiro-NPD, spiro-TPD, spiro-TAD, TNB, and the like, arylamine compounds, amine compounds containing a carbazole group, An amine compound containing a fluorene derivative can be exemplified, and any generally known hole transporting material can be used.

  As a material of the light emitting layer 5, any material known as a material for an organic electroluminescence element can be used. For example, anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyxyl) Norinato) aluminum complex, tris (4-methyl-8-quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl- 4-yl) amine, 1-aryl-2,5-di (2-thienyl) pyrrole derivative, pyran, quinacridone, rubrene, distyrylbenzene derivative, distyrylarylene derivative, distili And amine derivatives, and various fluorescent dyes, but include those including a material system and its derivatives described above, not limited to these. In addition, it is also preferable to use a mixture of light emitting materials selected from these compounds as appropriate. Further, not only compounds that emit fluorescence, typified by the above-mentioned compounds, but also material systems that emit light from a spin multiplet, for example, phosphorescent materials that emit phosphorescence, and parts made of these are part of the molecule. The compound which has can also be used suitably. The light emitting layer made of these materials may be formed by a dry process such as vapor deposition or transfer, or by a wet process such as spin coating, spray coating, die coating, or gravure printing. You may do.

The material used for the electron transport layer 6 can be selected from the group of compounds having electron transport properties. Examples of such compounds, and metal complexes known as electron-transporting material such as Alq _3, phenanthroline derivatives, pyridine derivatives, tetrazine derivatives, and compounds having a hetero ring such as oxadiazole derivatives, this shall Instead, any generally known electron transport material can be used.

  The material of the electron injection layer 7 is, for example, a metal fluoride such as lithium fluoride or magnesium fluoride, a metal halide such as sodium chloride or magnesium chloride, aluminum, cobalt, or zirconium. Titanium, vanadium, niobium, chromium, tantalum, tungsten, manganese, molybdenum, ruthenium, iron, nickel, copper, gallium, zinc, silicon oxides, nitrides, carbides, oxynitrides, etc. Arbitrary selection from insulators such as aluminum oxide, magnesium oxide, iron oxide, aluminum nitride, silicon nitride, silicon carbide, silicon oxynitride, boron nitride, silicon compounds such as silicon oxide, carbon compounds, etc. Can be used. These materials can be formed into a thin film by being formed by a vacuum deposition method or a sputtering method.

  The electron injection layer 7 can be formed using a material made of at least one kind of organic material. As this organic material, any material known as a material for an organic electroluminescence element can be used, and a material capable of injecting electrons from the cathode 7 to the electron injection layer 5 and having an electron transporting property. Is preferred.

  Further, the electron injection layer 7 is not limited to a layer formed of one kind of organic material, and for example, cesium, lithium, sodium, magnesium, potassium, rubidium, samarium, yttrium can be used for one kind of organic material. A layer formed by mixing an alkali metal, alkaline earth metal, rare earth metal oxide, fluoride, chloride, halide, or the like having a low work function.

  The electron injection layer 7 is made of various materials such as aluminum, cobalt, zirconium, titanium, vanadium, niobium, chromium, tantalum, tungsten, manganese, molybdenum, ruthenium, iron, nickel, copper, gallium, and zinc as organic materials. Oxides, nitrides, carbides, oxynitrides, etc., such as aluminum oxide, magnesium oxide, iron oxide, aluminum nitride, silicon nitride, carbon nitride, silicon oxynitride, boron nitride, silicon oxide and other silicon The layer formed by mixing a compound, a carbon compound, etc. may be sufficient.

  In this embodiment, the organic EL layer 8 is composed of the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the electron transport layer 6, and the electron injection layer 7 interposed between the anode 1 and the cathode 2. However, the organic EL layer 8 only needs to include at least the light emitting layer 5.

  The cathode 2 is an electrode for injecting electrons into the light emitting layer 5 and is a material having a work function of 1.9 eV or more and 5 eV or less so that the difference from the LUMO (Lowest Unoccupied Molecular Orbital) level does not become too large. Is preferably used. In this embodiment, the cathode 2 is used as a transparent electrode, and light is extracted from the cathode 2 side (including the case where light is extracted from both the anode 1 and the cathode 2), so that the light transmittance of the cathode 2 is set to 70% or more. Is preferred.

  By the way, since the cathode 2 is formed after the organic EL layer 8 is formed, an increase in the film formation temperature is restricted due to the heat-resistant temperature of the organic EL layer 8 and the like. In the case of using only a conductive film, the sheet resistance of the cathode 2 is increased. In contrast, the cathode 2 in the present embodiment includes a first transparent conductive film 2a, a translucent thin film 2b made of a metal thin film, and a second transparent conductive film 2c, which are stacked in the thickness direction of the organic EL layer 8. It is comprised by the laminated film of.

Here, as a material of the first transparent conductive film 2a and the second transparent conductive film 2c, a known transparent electrode material can be employed. For example, indium oxide-based materials such as ITO and IZO (those based on indium), zinc oxide-based materials such as AZO and GZO (those based on zinc), and oxidations such as FTO and ATO Examples thereof include tin-based materials (thin based on tin). In addition, a transparent electrode material having a property of transmitting light such as molybdenum oxide or titanium oxide and having a specific resistance of about 10 ⁵ Ωcm can be used. Although the thickness of the 1st transparent conductive film 2a and the 2nd transparent conductive film 2c changes with materials, 100 nm or less is desirable respectively. In particular, when the specific resistance is 10 ⁻¹ Ωcm or more, it is more preferably 50 nm or less.

  As a method for forming the second transparent conductive film 2c, a sputtering method, a resistance heating vapor deposition method, an electron beam vapor deposition method, an ion plating method, or the like can be appropriately employed.

  On the other hand, when a parallel plate type direct current or high frequency magnetron sputtering method or ion plating method is adopted as a method of forming the first transparent conductive film 2a, the organic EL layer 8 is caused by plasma or a sputtering phenomenon. There is a concern that the characteristics of the organic electroluminescence element may be deteriorated due to damage.

  Therefore, as a method for forming the first transparent conductive film 2a, in order to reduce damage to the organic EL layer 8 as a base during film formation, a parallel plate type direct current or high frequency magnetron sputtering method or ion plating method is used. A film forming method having a low film forming energy is preferable, and for example, a resistance heating evaporation method, an electron beam evaporation method, a laser heating evaporation method, or an opposed target sputtering method is preferably employed.

  The film formation energy is not limited to the type of film formation method, but varies depending on the structure of the film formation apparatus, the material of the first transparent conductive film 2a, the specific resistance, light transmittance, and other characteristics. The film formation energy of molybdenum oxide by the sputtering method is about 0.001 eV, and the film formation energy of titanium oxide by the electron beam evaporation method is about 0.02 eV, whereas the molybdenum oxide by the parallel plate type direct current or high frequency magnetron sputtering method. The film-forming energy is about 300 eV, and the film-forming energy of titanium oxide by a parallel plate direct current or high-frequency magnetron sputtering method is about 400 eV, so that the film-forming energy can be sufficiently reduced.

  The value of the film formation energy described above is a value derived by analyzing the kinetic energy of gas molecules (particles of the film formation material) in the atmosphere at the time of film formation using an energy analyzer of model number PPM442 manufactured by Pfeiffer. is there. Here, when molecules other than the film forming material (film forming material) such as argon and oxygen coexist in the atmosphere during film formation as in the sputtering method, the highest of the molecules in the atmosphere. The energy of molecules having energy is used as film formation energy.

  The first transparent conductive film 2a is preferably formed by a vapor phase method having a film formation energy of 10 eV or less, and the above-described resistance heating evaporation method, electron beam evaporation method, laser heating evaporation method, and magnetron sputtering method are used. If so, this condition can be satisfied. Even in the parallel plate type DC sputtering method, a gas other than argon gas (for example, krypton gas, xenon gas, etc.) is used as the sputtering gas, the pressure during film formation is increased, the target and the substrate By setting the distance to 10 to 100 mm or more, it is also possible to perform film formation by controlling the film formation energy to 10 eV or less. Further, from the viewpoint of reducing the film formation energy and reducing the damage to the organic EL layer 8, the resistance heating vapor deposition method, the electron beam vapor deposition method, and the laser heating vapor deposition method are preferable to the counter target sputtering method. From the viewpoint of improving the characteristics (conductivity and transmittance) of the transparent conductive film 2a, the opposed target sputtering method is preferable to the resistance heating evaporation method, the electron beam evaporation method, and the laser heating evaporation method. Depending on the film formation method, for the electrons and ultraviolet rays generated during the film formation, a filter, a metal mesh, a reflection plate for reflecting, etc. are suitably provided in the film formation apparatus. It is preferable to dispose them so as not to reach the organic EL layer 8.

  The first transparent conductive film 2a and the second transparent conductive film 2c described above may employ the same material or different materials. Further, the first transparent conductive film 2a and the second transparent conductive film 2c may be formed to have the same thickness or different thicknesses.

  Moreover, the metal thin film which comprises the translucent thin film 2b should just be formed with 2 or more types of metals selected from the group of silver, indium, gold | metal | money, magnesium, and tin, for example, if silver and magnesium are employ | adopted. Good. The translucent thin film 2b made of a metal thin film is formed by sputtering, but is not limited to sputtering, and may be formed by, for example, co-evaporation. However, when the film is formed by the sputtering method, the adhesion between the translucent thin film 2b and the first transparent conductive film 2a as the base is improved, and the reliability is improved.

  Here, it is preferable to set the film thickness of the metal thin film which comprises the translucent thin film 2b in the range of 1-10 nm. Although depending on the flat area of the cathode 2, the material of the metal thin film, the film forming method, etc., if the metal thin film is made thinner than 1 nm, the metal thin film tends to be island-like and the resistance value of the metal thin film is reduced. Is too big. Moreover, when the film thickness of the metal thin film is thicker than 10 nm, the light transmittance becomes too low.

  Moreover, it is desirable that the material of the metal thin film constituting the translucent thin film 2b contains a constituent element made of the metal of the first transparent conductive film 2a as a base. For example, when the material of the first transparent conductive film 2a is an indium oxide-based material such as ITO, it is desirable to contain indium as the material of the metal thin film, and the material of the first transparent conductive film 2a is FTO. In the case of a tin oxide-based material such as the above, it is desirable to contain tin as a material for the metal thin film.

  In the organic electroluminescence element of the present embodiment, the substrate 10, the anode 1 formed on the one surface side of the substrate 10, and the organic including at least the light emitting layer 5 formed on the opposite side of the anode 1 from the substrate 10 side. A first transparent conductive film 2 a having an EL layer 8 and a cathode 2 formed on the side opposite to the anode 1 side of the organic EL layer 8, the cathode 2 being laminated in the thickness direction of the organic EL layer 8. And a transparent film 2b made of a metal thin film and a second transparent conductive film 2c, and the metal thin film is selected from the group consisting of silver, indium, gold, magnesium and tin. Since it is made of metal, it is possible to suppress the diffusion of metal from the cathode 2 to the light emitting layer 5 side while reducing the resistance of the cathode 2, to extend the life, and to improve the luminous efficiency. Low power drive voltage It attained the reduction. Therefore, it is possible to reduce luminance unevenness while increasing the luminance of the organic electroluminescence element.

  Moreover, in the organic electroluminescent element of this embodiment, if the metal thin film which comprises the translucent thin film 2b in the cathode 2 contains the structural element which consists of the metal of the 1st transparent conductive film 2a, The diffusion of the metal during energization is further suppressed, and the long-term reliability of the cathode 2 is improved, resulting in a highly reliable organic electroluminescence element.

  Moreover, in the organic electroluminescent element of this embodiment, the resistance heating vapor deposition method, the electron beam vapor deposition method, the laser heating vapor deposition method, and the counter target type sputtering method are used as the film formation method of the first transparent conductive film 2a of the cathode 2. By adopting it, it is possible to reduce damage to the organic EL layer 8 which is the base during the film formation of the first transparent conductive film 2a, and to form a good interface between the first transparent conductive film 2a and the organic EL layer 8. Therefore, it is possible to suppress the formation of traps in the vicinity of the interface, and it is possible to suppress a decrease in electron injection performance, and as a result, it is possible to improve the light emission efficiency.

  By the way, the laminated structure of the organic electroluminescence element of the present invention can be appropriately changed unless it is contrary to the technical idea of the present invention. For example, a plurality of light emitting layers 5 are provided between the anode 1 and the cathode 2. Thus, white light may be obtained. In this case, for example, the plurality of light emitting layers 5 may include a laminated structure of a blue hole transporting light emitting layer, a green electron transporting light emitting layer, and a red electron transporting light emitting layer, or a blue electron transporting property. A light emitting layer, a green electron transporting light emitting layer and a red electron transporting light emitting layer may be provided, or an organic EL layer 8 having a function of emitting light when a voltage is applied between the anode 1 and the cathode 2. As a single light-emitting unit, a multi-unit structure in which a plurality of light-emitting units are stacked via an optically transparent and conductive intermediate layer and electrically connected in series (that is, one anode 1 and one cathode 2 In the meantime, a structure including a plurality of light emitting units overlapping in the thickness direction may be employed. Further, in a single-layer type organic electroluminescence element having only one light emitting layer 5, the light emitting layer 5 may contain a plurality of light emitting materials to obtain mixed light such as white light.

  The laminated structure of the cathode 2 described above may also be applied to the anode 1. However, in the case where the substrate 10 is a substrate having higher heat resistance than a plastic such as a glass substrate, there is less restriction on the substrate temperature at the time of film formation. Therefore, by increasing the film formation temperature of the transparent conductive film, the cathode The resistance can be reduced more easily than 2.

DESCRIPTION OF SYMBOLS 1 Anode 2 Cathode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Electron injection layer 8 Organic EL layer 10 Substrate

Claims (2)

  A substrate, an anode formed on one surface side of the substrate, an organic EL layer including at least a light emitting layer formed on the opposite side of the anode to the substrate side, and the anode side of the organic EL layer opposite to the anode side A cathode formed on the side of the organic EL layer, the cathode comprising a first transparent conductive film, a translucent thin film made of a metal thin film, and a second transparent conductive film laminated in the thickness direction of the organic EL layer An organic electroluminescence element comprising a laminated film, wherein the metal thin film is made of two or more metals selected from the group consisting of silver, indium, gold, magnesium and tin.   The organic electroluminescence element according to claim 1, wherein the metal thin film contains a constituent element made of a metal of the first transparent conductive film.

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