Organic electroluminescence device

Abstract

To provide a laminated organic electroluminescent element using an easy-to-handle alkali metal compound and including an intermediate layer having good electron injection properties.SOLUTION: The laminated organic electroluminescent element has two organic electroluminescent layers 10a, 10b with an intermediate layer 20 therebetween between a positive electrode 3 and a negative electrode 4. The organic electroluminescent element contains an intermediate layer 20 made of an alkali metal compound, a reductant made of the alkali metal compound, and a metallic element of group 2 of the periodic table.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an organic electroluminescence element, which is a type of light-emitting element, and to an apparatus and device using the element. [Background technology]

[0002] An organic electroluminescence (EL) element is a light-emitting element that emits light by passing a current through an organic EL layer having a pair of electrodes and a light-emitting layer sandwiched between the pair of electrodes. In recent years, full-color light-emitting arrays that combine white-emitting organic EL elements with red, green, and blue color filters have been developed. White-emitting organic EL elements are broadly classified into single-layer organic EL elements that obtain white light emission by coexisting light-emitting dopants that emit red, green, and blue light in one organic EL layer, and stacked organic EL elements in which organic EL layers that emit red, green, and blue light are stacked. In stacked organic EL elements, a structure in which an intermediate layer called a charge generation layer or intermediate electrode layer is interposed between two organic EL layers to connect multiple organic EL layers in series is known. Since white-emitting organic EL elements are not painted for each pixel, if the intermediate layer has low electrical resistance, adjacent pixels will emit light through the intermediate layer, so development of a high-resistance intermediate layer is underway. Patent Document 1 discloses a structure in which an intermediate layer uses a conductive organic compound or an organic compound doped with an alkali metal, while Patent Document 2 discloses a laminate structure of an organic compound layer doped with an alkali metal compound and an organic compound layer doped with a metal element of Group 2 of the periodic table. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-45676 A [Patent Document 2] Special Publication No. 2015-518287 Summary of the Invention [Problem to be solved by the invention]

[0004] In the organic EL element disclosed in Patent Document 1, an alkali metal is used as the intermediate layer, but there is a problem that the alkali metal is easily reactive with moisture in the air and difficult to handle. In contrast, in the organic EL element disclosed in Patent Document 2, an organic compound layer doped with an alkali metal compound that is easy to handle as the intermediate layer is formed, and then an organic compound layer doped with a Group 2 metal is laminated. In this case, it is considered that the alkali metal compound is reduced by the Group 2 metal, thereby expressing electron injection properties. In addition, by using the Group 2 metal as a dope in the organic compound, the intermediate layer has a higher resistance than when a metal element is used alone. In detail, it is preferable to use an alkali metal to inject electrons into the organic EL layer, but alkali metals are difficult to handle because they easily react with moisture in the air. Therefore, an alkali metal compound layer that is easy to handle, such as lithium fluoride or lithium quinolinol complex, is formed, and then a metal having reducibility, such as aluminum or a group 2 metal, is evaporated, so that a part of the alkali metal compound is reduced by the heat during evaporation, and electron injection properties are expressed. What is important in this method is the adhesion between the alkali metal compound layer and the metal layer having reducibility. Although aluminum has high adhesion to the alkali metal compound layer, it has low electrical resistance and is not preferable as an intermediate layer where high resistance is desired. In addition, when a group 2 metal is evaporated alone, it has low adhesion to the underlayer and is poor in film formability, so when used for a cathode, it is often co-evaporated with silver or the like to increase adhesion to the underlayer. However, a layer co-evaporated with a group 2 metal and silver has low electrical resistance and is not preferable as an intermediate layer where high resistance is desired. In Patent Document 2, the adhesion between organic compound layers is improved by utilizing the high adhesion between the organic compound layers and stacking organic compound layers in which an alkali metal compound and a Group 2 metal are doped into the organic compound. However, the compatibility between the organic compound and the Group 2 metal is low, and even if the organic compound and the Group 2 metal are co-deposited, the Group 2 metal is difficult to incorporate into the organic compound layer. Therefore, the alkali metal compound in the underlying organic compound layer is difficult to reduce, and there is a risk that the electron injection property is not fully expressed. The present invention has been made in view of the above problems, and provides a stacked organic EL device using an alkali metal compound which is easy to handle and which is provided with an intermediate layer having good electron injection properties. [Means for solving the problem]

[0005] A first aspect of the present invention is an organic electroluminescence element having a pair of electrodes and at least two organic electroluminescence layers disposed between the pair of electrodes and overlapping each other via an intermediate layer, The intermediate layer contains an alkali metal compound, a reduced form of the alkali metal compound, and a metal element of Group 2 of the periodic table. death, The intermediate layer is a co-deposited layer of the alkali metal compound and the Group 2 metal element. It is characterized by: The second aspect of the present invention is An organic electroluminescence element having a pair of electrodes and at least two organic electroluminescence layers disposed between the pair of electrodes and overlapping each other via an intermediate layer, the intermediate layer contains an alkali metal compound, a reduced form of the alkali metal compound, and a metal element of Group 2 of the periodic table; The intermediate layer is characterized in that it consists only of the alkali metal compound, a reduced form of the alkali metal compound, and the Group 2 metal element. The present invention three The present invention relates to an exposure light source, a display device, an imaging device, a lighting device, and a mobile object, each of which is characterized by having the organic electroluminescence element of the present invention. Effect of the Invention

[0006] According to the present invention, by using a co-deposition layer of an easily handled alkali metal compound and a Group 2 metal as an intermediate layer, it is possible to provide a stacked organic EL device having sufficient electron injection properties and a high resistance intermediate layer. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view in the thickness direction illustrating the configuration of an organic EL element of the present invention. [Diagram 2] 1 is a schematic cross-sectional view in the thickness direction illustrating a configuration of a preferred embodiment of an organic EL element of the present invention. [Diagram 3] 1 is a schematic diagram showing a configuration of an embodiment of an exposure light source of the present invention. [Figure 4] 1 is a schematic cross-sectional view in a thickness direction showing a pixel configuration of an embodiment of a display device of the present invention. [Diagram 5] 1 is an exploded perspective view showing an overall configuration of an embodiment of a display device of the present invention; [Figure 6] FIG. 11 is a front view illustrating a display device according to another embodiment of the present invention. [Figure 7] 1 is a front view showing an embodiment of an imaging device and electronic device of the present invention; [Figure 8] 1 is an exploded perspective view showing a schematic diagram of an embodiment of a lighting device according to the present invention; [Figure 9] 1 is a perspective view showing a schematic diagram of an embodiment of a moving body of the present invention; [Figure 10] FIG. 1 is a perspective view showing a schematic configuration of glasses using a display device of the present invention. [Figure 11] 1 is a graph showing voltage-current characteristics of the organic EL elements of Examples 1 and 2 of the present invention. [Figure 12] 1 is a graph showing voltage-current characteristics of the organic EL elements of Comparative Examples 1 and 2 of the present invention. [Figure 13] 1 is a graph showing voltage-current characteristics of the organic EL elements of Comparative Example 3 and Comparative Example 4 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The organic electroluminescence element (hereinafter referred to as "organic EL element") of the present invention is a laminated organic EL element having at least two organic electroluminescence layers (hereinafter referred to as "organic EL layers") between a pair of electrodes. An intermediate layer is interposed between the two organic EL layers, and the intermediate layer contains an alkali metal compound, a reduced form of the alkali metal compound, and a metal element of Group 2 of the periodic table (hereinafter referred to as "Group 2 metal").

[0009] The configuration of the EC element of the present invention will be described in detail below by way of preferred embodiments with reference to the drawings. However, the configuration, relative arrangement, and the like described in the embodiments are not intended to limit the scope of the present invention unless otherwise specified.

[0010] [Organic EL element] Fig. 1 is a cross-sectional schematic diagram in the thickness direction (lamination direction) showing the configuration of the organic EL element of the present invention. In the figure, 1 is the organic EL element, 2 is the substrate, 3 is the anode, 4 is the organic compound layer, 5 is the cathode, 10 is the organic EL layer, and 20 is the intermediate layer. Note that the organic compound layer 4 according to the present invention also includes layers that do not contain an organic compound, such as the intermediate layer 20, but in this specification, the laminate interposed between the anode 3 and the cathode 5 is referred to as the "organic compound layer" for convenience.

[0011] As shown in FIG. 1, the organic EL element 1 of the present invention includes an organic compound layer 4 in which a plurality of organic EL layers 10 are laminated with an intermediate layer 20 interposed therebetween. In the organic EL element 1 of the present invention, the organic EL layers 10 may be three layers, each of which emits red, green, or blue light, emitting white light as a whole, or the organic EL layers 10 may be two layers, one of which emits red and green light and the other emits blue light as a whole, emitting white light as a whole. In addition, it is also possible to make the emission colors of the plurality of organic EL layers 10 the same color, thereby obtaining multiple times the emission and achieving high brightness. For example, when the organic EL layer 10 is two layers, twice the emission can be obtained as when it is one layer.

[0012] In the present invention, the organic EL layer 10 can be three or more layers, but two layers are preferable because the voltage applied between the electrodes becomes high and the heat generation of the element increases. FIG. 2 is a cross-sectional view in the thickness direction showing the configuration of an embodiment in which the organic EL layer 10 is two-layered. In the following description, for convenience, the organic EL layer 10a on the anode side is referred to as the first organic EL layer, and the organic EL layer 10b on the cathode side is referred to as the second organic EL layer. The positions of the anode 3 and the cathode 5 may be reversed, but as described later, when the electron injection layers 15a and 15b are composed of an alkali metal compound, they may be formed in order from the anode 3 toward the cathode 5, with the anode 3 on the substrate 2 side.

[0013] The intermediate layer 20 according to the present invention is a codeposition layer formed by codepositing an alkali metal compound and a Group 2 metal. The alkali metal compound used in the intermediate layer 20 of the present invention is a substance in which an alkali metal becomes a cation and is bonded to an anion, such as a halide, an oxide, a carbonate, or an organic coordination compound. Unlike an alkali metal, an alkali metal compound does not react violently with moisture in the air, is stable in the air, and is easy to handle. In addition, since it is an ionic substance, it is an insulating substance in nature and does not have electron injection properties as it is. When such an alkali metal compound is formed into a film and a metal having a reducing property, such as aluminum (Al) or a Group 2 metal, is deposited thereon, a part of the alkali metal compound is reduced and electron injection properties are expressed. However, since Al has low electrical resistance, there is a problem that adjacent pixels emit light through the intermediate layer. In addition, when a Group 2 metal is deposited alone, it has low adhesion to the underlayer and is difficult to form a film, so it is necessary to codeposit it with silver (Ag) or the like, which has high adhesion to the underlayer. However, since Ag has low electrical resistance like Al, there is a problem that adjacent pixels emit light through the intermediate layer. The resistivity of Al at 0°C is 2.50×10 -8 Ωm, Ag is 1.47×10 -8 For example, magnesium (Mg), which is classified as a group 2 metal, has a resistance of 3.94 × 10 -8 It tends to have a lower resistance than Ωm.

[0014] In the present invention, in order to reduce the alkali metal compound without using Al or Ag, it is preferable to codeposit the alkali metal compound with a Group 2 metal and reduce the alkali metal compound during deposition. When the alkali metal compound is codeposited with a Group 2 metal, a part of the alkali metal compound is reduced by the Group 2 metal, and electron injection properties are developed. In addition, the intermediate layer 20 according to the present invention is a layer in which an alkali metal compound, which is an insulating material, a reduced form of the alkali metal compound, and a Group 2 metal, which has high resistance as a metal, are mixed, and therefore has high electrical resistance. When the intermediate layer 20 is formed by codepositing an alkali metal compound and a Group 2 metal, an intermediate layer 20 consisting of only the alkali metal compound, the reduced form of the alkali metal compound, and the Group 2 metal is obtained.

[0015] In the present invention, the organic EL layers 10a and 10b each include at least a light-emitting layer 13a or 13b. The light-emitting layers 13a and 13b may each have a structure in which a plurality of light-emitting layers are laminated, or a single layer structure, and may be a two-color light-emitting layer containing two-color light-emitting dopants or a white light-emitting layer containing three-color light-emitting dopants, as described above.

[0016] 2, the organic EL layers 10a and 10b may include hole injection layers 11a and 11b and hole transport layers 12a and 12b on the anode 3 side of the light-emitting layers 13a and 13b, and electron transport layers 14a and 14b and electron injection layers 15a and 15b on the cathode 5 side. Furthermore, each of the organic EL layers 10a and 10b may have an electron blocking layer and a hole blocking layer as necessary.

[0017] In the present invention, the Group 2 metal contained in the intermediate layer 20 is preferably 75% by volume or less. If the content of the Group 2 metal exceeds 75% by volume, the resistance of the intermediate layer 20 decreases, which is undesirable as it is likely to cause a problem of adjacent pixels emitting light through the intermediate layer 20. Furthermore, in order to reduce the alkali metal compound, the Group 2 metal is preferably contained in an amount of 30% by volume or more. The content of the Group 2 metal can be controlled by the deposition rate when the alkali metal compound and the Group 2 metal are deposited.

[0018] In the present invention, the alkali metal compound forming the intermediate layer 20 is an ionic compound of lithium (Li), potassium (K), sodium (Na), rubidium (Rb), or cesium (Cs). Among them, Li has the smallest atomic weight, and thus Li compounds tend to have the smallest substance amount and the lowest deposition temperature, and are therefore preferred, and lithium halide or lithium quinolinol complex (Liq) is preferred. Alkaline metal halides and Liq are preferred because they have a low deposition temperature. As the lithium halide, lithium fluoride (LiF) is preferred. Potassium fluoride (KF) is also preferably used. Among halides, fluorides are preferred because they have a small substance amount and a low deposition temperature, and LiF is the most preferred alkali metal compound used in the present invention.

[0019] In addition, Cs compounds tend to require a higher deposition temperature than Li compounds, but are preferred because of their high electron injection properties. Cesium carbonate (Cs2Co3) is preferred as a deposition material because it has a lower deposition temperature than other cesium compounds, is less deliquescent, and is less likely to contain moisture.

[0020] In the present invention, the Group 2 metal forming the intermediate layer 20 refers to any one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). It is believed that any of these Group 2 metals has the property of being able to reduce an alkali metal compound when vapor-deposited on the alkali metal compound. However, the electron injection property of the intermediate layer 20 differs depending on the combination of the alkali metal compound and the Group 2 metal, and Mg, Ca, and Sr provide good electron injection property. Among these, Mg is the most preferable because it has the lowest melting point, is inexpensive, is non-toxic, and is stable in the air.

[0021] In the present invention, it is preferable that the first organic EL layer 10a located closer to the anode 3 than the intermediate layer 20 has an electron injection layer 15a in contact with the intermediate layer 20, and that the electron injection layer 15a is a layer formed by single deposition of an alkali metal compound constituting the intermediate layer 20. By forming the electron injection layer 15a from an alkali metal compound and then co-depositing the alkali metal compound and a Group 2 metal to form the intermediate layer 20, a part of the alkali metal compound in the electron injection layer 15a is reduced during deposition of the intermediate layer 20, and the electron injection property of the electron injection layer 15a is expressed. That is, the electron injection layer 15a is a layer containing an alkali metal compound and a reduced form of the alkali metal compound.

[0022] In the present invention, the intermediate layer 20 has the ability to inject electrons into the first organic EL layer 10a, and therefore the electron injection layer 15a is not necessarily required. However, it is a preferred embodiment that the electron injection layer 15a is provided in contact with the intermediate layer 20, and that the intermediate layer 20 and the electron injection layer 15a are formed using the same alkali metal compound. In this case, the adhesion between the intermediate layer 20 and the electron injection layer 15a is high, and in addition to the electron injection ability of the intermediate layer 20, the reduced form of the alkali metal compound contained in the electron injection layer 15a can further enhance the electron injection ability into the electron transport layer 14a and the light-emitting layer 13a.

[0023] Furthermore, in the present invention, it has been found that even when the electron injection layer 15a is present, the combination of an alkali metal compound and a Group 2 metal in the intermediate layer 20 is more likely to exhibit electron injection properties than the combination of an organic compound and a Group 2 metal. This is believed to be because the combination of an alkali metal compound and a Group 2 metal has higher compatibility than the combination of an organic compound and a Group 2 metal, and is more likely to be formed as a mixed film when co-deposited.

[0024] In the present invention, it is preferable that the second organic EL layer 10b located closer to the cathode 5 than the intermediate layer 20 has a hole injection layer 11b in contact with the intermediate layer 20. The intermediate layer 20 contains a reduced form of an alkali metal compound and a Group 2 metal, so that the ionization potential is small, and the metal with a small ionization potential has low hole injection properties into the hole transport layer 12b and the light emitting layer 13b. Therefore, it is preferable to have the hole injection layer 11b in contact with the intermediate layer 20. As a material for forming the hole injection layer 11b, a conventionally known material for injecting holes from the anode to the hole transport layer is used, and organic compounds having a cyano group, such as those shown in H16 to H19 described later, molybdenum oxide, and phthalocyanines are used.

[0025] As shown in Fig. 1 and Fig. 2, the organic EL element 1 of the present invention is formed on a substrate 2, and the substrate 2 may be any of quartz, glass, silicon wafer, resin, metal, etc. In addition, a switching element such as a transistor and wiring may be provided on the substrate 2, and an insulating layer may be provided thereon. As the insulating layer, any material may be used as long as it can form a contact hole to ensure electrical continuity between the anode 3 and the wiring and can ensure insulation from unconnected wiring. For example, a resin such as polyimide, silicon oxide, silicon nitride, etc. may be used.

[0026] The material constituting the anode 3 should preferably have a work function as large as possible. For example, metals such as gold, platinum, silver, copper, nickel, palladium, titanium, cobalt, selenium, vanadium, tungsten, etc., mixtures containing these metals, alloys combining these metals, metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide, etc. Also usable are conductive polymers such as polyaniline, polypyrrole, polythiophene, etc.

[0027] These electrode materials may be used alone or in combination of two or more. The anode 3 may be composed of one layer or multiple layers. When used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, or alloys, oxides, nitrides, and laminates thereof may be used. When used as a transparent electrode, a transparent conductive layer of oxide such as indium tin oxide (ITO) or indium zinc oxide may be used, but is not limited to these. The electrodes can be formed by photolithography.

[0028] The organic EL element 1 of the present invention has at least a first organic EL layer 10a and a second organic EL layer 10b sandwiching an intermediate layer 20. The first organic EL layer 10a and the second organic EL layer 10b may be formed using the same material. It is also possible to laminate three or more layers, such as by laminating a third organic EL layer. The materials for forming these layers will be described below.

[0029] In the first organic EL layer 10a on the anode 3 side, the hole injection layer 11a provided in contact with the anode 3 is preferably made of a material that can facilitate the injection of holes from the anode 3, and may be made of the same material as the hole injection layer 11b in contact with the intermediate layer 20 described above. That is, organic compounds having a cyano group, molybdenum oxide, phthalocyanines, etc., as shown in H16 to H19 described later, are used.

[0030] Moreover, for the hole transport layers 12a and 12b, a material having high hole mobility is preferable so that the injected holes can be transported to the light emitting layers 13a and 13b. Furthermore, in order to suppress deterioration of the film quality such as crystallization in the organic EL element 1, a material having a high glass transition temperature is preferable. Examples of low molecular weight and high molecular weight materials having high hole mobility include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene), and other conductive polymers. Also, the same materials as those for the hole injection layers 11a and 11b can be used.

[0031] Specific examples HT1 to HT19 of materials used for the hole injection layers 11a and 11b and the hole transport layers 12a and 12b are shown below, but the present invention is not limited to these.

[0032] In addition, an electron blocking layer (not shown) may be provided between the hole transport layers 12a, 12b and the light emitting layers 13a, 13b, and the same material can be used when forming the electron blocking layer. As the electron blocking material, HT7, HT8 to HT12 containing a carbazole group are preferable. By containing a carbazole group, the HOMO becomes deeper, and a level where the HOMO becomes deeper in the order of the hole transport material, the hole blocking material, and the light emitting layer can be created, and holes can be injected into the light emitting layers 13a, 13b at a low voltage.

[0033] [ka]

[0034] The light-emitting layers 13a and 13b preferably have a structure in which a light-emitting dopant is contained in a host material. Specific examples of the host material, EM1 to EM40, are shown below.

[0035] [ka]

[0036] Specific examples of red light-emitting dopant materials RD1 to RD10 are shown below. The doping concentration of the red light-emitting dopant material is preferably 0.1% by mass or more and less than 5% by mass, and more preferably 0.1% by mass or more and less than 0.5% by mass. If the concentration is too low, it will lead to a decrease in the red light emission intensity, and conversely, if the concentration is too high, it will cause concentration quenching, which is not preferable.

[0037] [ka]

[0038] Specific examples GD1 to GD15 of the green light-emitting dopant material are shown below: The doping concentration of the green light-emitting dopant material is preferably 0.1 mass % or more and less than 10 mass %, and more preferably 1 mass % or more and less than 5 mass %.

[0039] [ka]

[0040] Specific examples of blue light-emitting dopant materials BD1 to BD31 are shown below. The doping concentration of the blue light-emitting dopant material is preferably 0.1 mass % or more and less than 5 mass %, and more preferably 0.3 mass % or more and less than 3 mass %.

[0041] [ka]

[0042] In the present invention, a host material may contain dopants of a plurality of luminescent colors or may be laminated, and the luminescent layers 13a and 13b may be the same or different colors.

[0043] The electron transport layers 14a and 14b can be arbitrarily selected from those capable of transporting electrons to the light-emitting layers 13a and 13b, and are selected in consideration of the balance with the hole mobility of the hole transport material. Materials having electron transport properties include oxadiazole derivatives, oxazole derivatives, pyridine derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organic aluminum complexes, and condensed ring compounds (e.g., fluorene derivatives, naphthalene derivatives, chrysene derivatives, anthracene derivatives, and fluoranthene derivatives). Specific examples ET1 to ET23 of materials used for the electron transport layers 14a and 14b are shown below, but are not limited thereto.

[0044] [ka]

[0045] In the present invention, a hole blocking layer (not shown) may be provided between the light emitting layers 13a, 13b and the electron transport layers 14a, 14b, and the above-mentioned electron transporting materials are also preferably used for the hole blocking layer. Among the electron transporting materials given as examples, the hole blocking material is preferably a compound consisting of only a hydrocarbon from the viewpoint of bond stability. As the electron transport layers 14a, 14b, materials having a pyridyl group or a phenanthryl group as a substituent, such as ET1 to ET8, are preferred. This is because they interact with electron injection materials such as alkali metal compounds and electrode materials, and have the effect of lowering the electron injection barrier.

[0046] In the present invention, the organic EL layer 10b on the cathode 5 side may have an electron injection layer 15b on the cathode 5 side of the light emitting layer 13b. The electron injection layer 15 is preferably made of an alkali metal compound such as LiF or Cs2CO3 used in the intermediate layer 20, and the alkali metal compound is reduced during deposition of the cathode 5 to exhibit electron injection properties.

[0047] The cathode 5 should have a small work function. However, alkali metals such as Li are not preferred because they are unstable in the air. Group 2 metals such as Ca and Mg, and mixtures and alloys of Group 2 metals with Al, titanium (Ti), manganese (Mn), Ag, lead (Pb), chromium (Cr), etc. can also be used. For example, Mg-Ag, Mg-Al, etc. can be used. Metal oxides such as ITO can also be used. These electrode materials may be used alone or in combination of two or more types. The cathode 5 may have a single layer structure or a multi-layer structure.

[0048] The cathode 5 is also preferably a top emission element using a thin film of Ag, an Ag alloy, or an oxide conductive layer such as ITO. The method for forming the cathode 5 is not particularly limited, but examples thereof include DC and AC sputtering methods and vapor deposition methods.

[0049] After the cathode 5 is formed, a sealing member (not shown) may be provided. For example, by adhering glass provided with a moisture absorbent onto the cathode 5, it is possible to prevent the intrusion of water and the like into the organic EL layers 10a and 10b and prevent the occurrence of display defects. In addition, a passivation film such as aluminum oxide or silicon nitride may be provided on the cathode 5 to prevent the intrusion of water and the like into the organic EL layers 10a and 10b. For example, after the cathode 5 is formed, the device may be transported to another chamber without breaking the vacuum, and a silicon nitride film having a thickness of 2 μm may be formed by a CVD method to serve as a sealing film.

[0050] A color filter may be provided for each pixel. For example, a color filter that matches the size of the pixel may be provided on a separate substrate and then bonded to the substrate on which the organic EL element is provided, or a color filter may be patterned on a sealing film such as silicon nitride by using a photolithography technique.

[0051] Among the layers included in the organic compound layer 4 constituting the organic EL element 1 of the present invention, the layers other than the intermediate layer 20 are formed by the following methods. For example, they can be formed by dry processes such as vacuum deposition, ionization deposition, sputtering, plasma, etc. In addition, instead of the dry process, a wet process can be used in which the layer is formed by dissolving in an appropriate solvent and forming a layer by a known coating method (for example, spin coating, dipping, casting, LB method, inkjet method, etc.). Here, when the layer is formed by the vacuum deposition method or solution coating method, crystallization is unlikely to occur and the layer has excellent stability over time. In addition, when forming a film by the coating method, a film can be formed by combining with an appropriate binder resin. Since the intermediate layer 20 has an alkali metal as a reductant, it is preferable to form it by deposition. Even if a method other than deposition is used, it is not limited to deposition as long as the intermediate layer 20 can be formed in the state of the alkali metal as a reductant.

[0052] Examples of the binder resin include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

[0053] These binder resins may be used alone or in combination as homopolymers or copolymers, and may further include known additives such as plasticizers, antioxidants, and ultraviolet absorbers, if necessary.

[0054] [Device using organic EL elements] The organic EL element of the present invention can be used as a component of a display device, a lighting device, etc. Other applications include an exposure light source for an electrophotographic image forming apparatus, a backlight for a liquid crystal display device, and a light-emitting device having a white light source and a color filter. The display device may be an image information processing device having an image input unit that inputs image information from an area CCD, a linear CCD, a memory card, etc., an information processing unit that processes the input information, and displays the input image on a display unit.

[0055] The display unit of the imaging device or inkjet printer may have a touch panel function. The driving method of this touch panel function may be any of an infrared type, a capacitive type, a resistive film type, and an electromagnetic induction type, and is not particularly limited. The display device may be used in the display unit of a multifunction printer. Various devices and apparatuses using the organic EL element of the present invention will be described below with reference to embodiments.

[0056] (Image forming device) 3(a) is a schematic diagram showing the configuration of an embodiment of an image forming apparatus equipped with an exposure device of the present invention. The image forming apparatus of this embodiment is an electrophotographic image forming apparatus having a photoconductor 27, an exposure light source 28, a developing unit 21, a charging unit 26, a transfer unit 22, a transport unit 23, and a fixing unit 25.

[0057] Light 29 is irradiated from an exposure light source 28, and an electrostatic latent image is formed on the surface of the photoconductor 27. This exposure light source 28 has the organic EL element of the present invention. The developing unit 21 has toner and the like, and the charging unit 26 charges the photoconductor 27. The transfer device 22 transfers the developed image to a recording medium 24 such as paper, and the conveying unit 23 conveys the recording medium 24. The fixing unit 25 fixes the image formed on the recording medium 24.

[0058] 3(b) and 3(c) are diagrams showing the configuration of an exposure light source 28 in which a plurality of organic EL elements 1 of the present invention are arranged on a long substrate as light-emitting sections. The arrows in the figures are parallel to the axis of the photoconductor 27 and represent the row direction in which the organic EL elements 1 are arranged. This row direction is the same as the direction of the axis about which the photoconductor 27 rotates, and can also be called the long axis direction of the photoconductor 27.

[0059] FIG. 3(b) shows a configuration in which the organic EL elements 1 are arranged along the long axis direction of the photoconductor. FIG. 3(c) shows a configuration different from (b), in which the organic EL elements 1 are arranged alternately in the column direction in the first column and the second column. The first column and the second column are arranged at different positions in the row direction. In the first column, a plurality of organic EL elements 1 are arranged at intervals. In the second column, the organic EL elements 1 are arranged at positions corresponding to the intervals between the organic EL elements 1 in the first column. That is, a plurality of organic EL elements 1 are also arranged at intervals in the row direction. The arrangement in FIG. 3(c) can be rephrased as a state in which the organic EL elements 1 are arranged in a lattice pattern, a state in which they are arranged in a staggered pattern, or a checkerboard pattern.

[0060] (display device) 4 is a schematic cross-sectional view in the thickness direction of one embodiment of a display device of the present invention. The display device of the present invention has a plurality of pixels, at least one of which is the organic EL element of the present invention.

[0061] FIG. 4(a) is a cross-sectional schematic diagram showing the configuration of one pixel of one embodiment of a display device using an organic EL element of the present invention. In this embodiment, one pixel has three sub-pixels 35, which are divided into 35R (red light emission), 35G (green light emission), and 35B (blue light emission) according to their light emission. In this embodiment, the organic EL element 1 emits white light, and the white light emitted from the organic EL element 1 is passed through color filters 34R (red), 34G (green), and 34B (blue) to obtain the respective emitted colors. The sub-pixels 35R, 35G, and 35B have the organic EL element 1 thereon, with the interlayer insulating layer 31 serving as a substrate. In this embodiment, an anode 3 is formed for each sub-pixel 35, and the individual anodes 3 are electrically insulated by the insulating layer 32.

[0062] In this embodiment, since light is emitted from the side where the color filters 34R, 34G, and 34B are provided, the cathode 5 is a transparent electrode and the anode 3 is a reflective electrode. The organic compound layer 4 and the cathode 5 are common to a plurality of pixels. Either the anode 3 or the cathode 5 of the organic EL element 1 may be disposed on the interlayer insulating layer 31 side. When the electron injection layer contained in the organic compound layer 4 is formed of an alkali metal compound, the anode 3 may be formed on the interlayer insulating layer 31 side, and the anodes 3 and the cathodes 5 may be formed in sequence in order to reduce the alkali metal compound.

[0063] In FIG. 4(a), 33 is a protective layer. The insulating layer 32 is also called a bank or a pixel separation film, and the area of ​​the anode 3 that is not covered with the insulating layer 32 contacts the organic compound layer 4 and becomes a light-emitting area. The protective layer 33 reduces the penetration of moisture into the organic compound layer 4. The protective layer 33 may be a single layer or multiple layers. In the case of multiple layers, each layer may have an inorganic compound layer and an organic compound layer.

[0064] The color filters 34R, 34G, and 34B may be formed on a planarization film (not shown). Also, a resin protective layer (not shown) may be provided on the color filters 34R, 34G, and 34B. The color filters 34R, 34G, and 34B may be provided on an opposing substrate such as a glass substrate and then bonded thereto.

[0065] The size of the light-emitting region surrounded by the insulating layer 32 is preferably 5 μm or more and 15 μm or less, and more specifically, may be 11 μm, 9.5 μm, 7.4 μm, 6.4 μm, etc. The interval between the subpixels may be 10 μm or less, and more specifically, may be 8 μm, 7.4 μm, or 6.4 μm.

[0066] The pixels may have a known arrangement in plan view. For example, they may be a stripe arrangement, a delta arrangement, a pentile arrangement, or a Bayer arrangement. The shape of the subpixels in plan view may be any known shape. For example, they may be a rectangle, a quadrangle such as a diamond, or a hexagon. Of course, if the shape is not an exact shape but is close to a rectangle, it is included in the rectangle. The shape of the subpixels and the pixel arrangement may be used in combination.

[0067] Fig. 4(b) is a cross-sectional schematic diagram showing the configuration of a pixel of another embodiment of a display device using the organic EL element of the present invention. In this embodiment, a transistor 48 is connected to the organic EL element 1. The transistor 48 in Fig. 4(b) is a thin film transistor (TFT), but may be a transistor other than a TFT or an active element other than a transistor.

[0068] In this embodiment, a substrate 41 such as glass or silicon is provided with an insulating layer 42 on its upper portion, and a transistor 48 is disposed on the insulating layer 42. The transistor 48 is composed of a gate electrode 43, a gate insulating film 44, a semiconductor layer 45, a drain electrode 46, and a source electrode 47. An insulating film 49 is provided on the upper portion of the transistor 48, and the anode 3 of the organic EL element 1 and the source electrode 47 of the transistor 48 are connected via a contact hole 50 provided in the insulating film 49.

[0069] The electrical connection between the electrodes (anode 3, cathode 5) included in the organic EL element 1 and the electrodes (source electrode 47, drain electrode 46) included in the transistor 48 is not limited to the embodiment shown in FIG. 4(b). In other words, it is sufficient that either the anode 3 or the cathode 5 is electrically connected to either the source electrode 47 or the drain electrode 46 of the TFT. Either the anode 3 or the cathode 5 of the organic EL element 1 may be disposed on the transistor 48 side. When the electron injection layer included in the organic compound layer 4 is formed of an alkali metal compound, the anode 3 may be formed on the substrate 41 side, and the electrodes may be formed in sequence from the anode 3 to the cathode 5 in order to reduce the alkali metal compound. In FIG. 4(b), reference numerals 51 and 52 denote protective layers for reducing deterioration of the organic EL element 1.

[0070] The transistor 48 is not limited to a TFT having an active layer (semiconductor layer 45) on the insulating surface of the substrate 41, but may be a transistor using a single crystal silicon wafer. Examples of the active layer include non-single crystal silicon such as single crystal silicon, amorphous silicon, and microcrystalline silicon, and non-single crystal oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide. Therefore, in this embodiment, the transistor 48 may be formed in the substrate 41 such as a Si substrate. Here, "formed in the substrate 41" means that the substrate 41 such as a Si substrate itself is processed to produce a transistor. In other words, having a transistor in the substrate 41 can be seen as the substrate 41 and the transistor 48 being integrally formed. Whether to provide a transistor in the substrate 41 or to use a TFT on the substrate 41 is selected depending on the size of the display unit. For example, if the size is about 0.5 inches, it is preferable to provide the organic EL element 1 on the Si substrate.

[0071] The organic EL element 1 according to this embodiment has its emission brightness controlled by a transistor 48, which is an example of a switching element. By providing a plurality of organic EL elements 1 on a plane, an image can be displayed based on the emission brightness of each element.

[0072] In this embodiment, the organic EL element 1 may be incorporated in a pixel circuit. The pixel circuit may be an active matrix type that controls the emission of the organic EL element 1 independently. The active matrix type circuit may be voltage programming or current programming. The drive circuit has a pixel circuit for each pixel. The pixel circuit may have a transistor that controls the emission luminance of the organic EL element 1, a transistor that controls the emission timing, a capacitance that holds the gate voltage of the transistor that controls the emission luminance, and a transistor for connecting to GND without going through the organic EL element 1.

[0073] The display device has a display region and a peripheral region disposed around the display region. The display region has pixel circuits, and the peripheral region has a display control circuit. The mobility of a transistor constituting the pixel circuit may be smaller than the mobility of a transistor constituting the display control circuit. The slope of the current-voltage characteristic of the transistor that constitutes the pixel circuit may be smaller than the slope of the current-voltage characteristic of the transistor that constitutes the display control circuit. The slope of the current-voltage characteristic can be measured by the so-called Vg-Ig characteristic.

[0074] 5 is an exploded perspective view showing the overall configuration of one embodiment of a display device of the present invention. A display device 60 has a touch panel 63, a display panel 65, a frame 66, a circuit board 67, and a battery 68 between an upper cover 61 and a lower cover 69. Flexible printed circuits (FPCs) 62 and 64 are connected to the touch panel 63 and the display panel 65. A transistor is printed on the circuit board 67. The battery 68 may not be provided if the display device is not a portable device, and may be provided in a different position even if the display device is a portable device.

[0075] Fig. 6 is a front view showing a schematic diagram of another embodiment of the display device of the present invention. Fig. 6(a) shows a display device such as a television monitor or a PC monitor. The display device 70 has a frame 71 and a display unit 72. The organic EL element of the present invention is used in the display unit 72. Moreover, the display device 70 has a frame 71 and a base 73 that supports the display unit 72. The base 73 is not limited to the form shown in Fig. 6(a), and the lower side of the frame 71 may also serve as the base. Moreover, the frame 71 and the display unit 72 may be curved, and the radius of curvature is preferably 5000 mm or more and 6000 mm or less.

[0076] The display device 80 in FIG. 6(b) is a so-called foldable display device that is configured to be bendable. The display device 80 has a first display unit 81, a second display unit 82, a housing 83, and a bending point 84. The first display unit 81 and the second display unit 82 are configured using the organic EL element of the present invention. The first display unit 81 and the second display unit 82 may be a single display unit without a joint. The first display unit 81 and the second display unit 82 can be separated by the bending point 84. The first display unit 81 and the second display unit 82 may each display different images, or the first and second display units may display a single image.

[0077] (Imaging device) The organic EL element of the present invention is used in a display section of an imaging device having an optical section with a plurality of lenses and an imaging element that receives light that has passed through the optical section. The imaging device has a display section that displays information acquired by the imaging element. The display section may be a display section exposed to the outside of the imaging device or a display section disposed within a viewfinder. Examples of imaging devices include digital cameras and digital video cameras.

[0078] 7(a) is a front view showing a schematic diagram of an embodiment of the imaging device of the present invention. The imaging device 90 of this embodiment has a viewfinder 91, a rear display 92, an operation unit 93, and a housing 94, and the viewfinder 91 is a display unit having the organic EL element of the present invention. The viewfinder 91 may display not only an image to be captured, but also environmental information, imaging instructions, and the like. The environmental information may include the intensity of external light, the direction of external light, the moving speed of the subject, the possibility that the subject will be blocked by an obstruction, and the like.

[0079] Since the optimal timing for imaging is very short, it is better to display information as soon as possible. Since organic EL elements have a fast response speed, the organic EL element of the present invention can realize a fast display, and is more preferably used than a liquid crystal display device when a high display speed is required.

[0080] The imaging device 90 has an optical section (not shown). The optical section has a plurality of lenses, which form an image on an imaging element housed in a housing 94. The focus of the plurality of lenses can be adjusted by adjusting their relative positions. This operation can also be performed automatically. The imaging device may be called a photoelectric conversion device. The photoelectric conversion device can include an imaging method that does not capture images sequentially, but detects the difference from the previous image, cuts out an image from an image that is constantly recorded, and the like.

[0081] (electronic equipment) The organic EL element of the present invention may be used in the display section of a mobile terminal. In this case, it may have both a display function and an operation function. Examples of the mobile terminal include mobile phones such as smartphones, tablets, and head-mounted displays.

[0082] FIG. 7(b) is a perspective view showing a schematic diagram of an embodiment of the electronic device of the present invention. The electronic device 100 has a display unit 101, an operation unit 102, and a housing 103. The housing 103 has a circuit, a printed circuit board having the circuit, a battery, and a communication unit, and the operation unit 102 may be a button or a touch panel type reaction unit. The operation unit 102 may be a biometric recognition unit that recognizes a fingerprint and performs unlocking or the like. An electronic device having a communication unit can also be called a communication device. The electronic device may further have a camera function by being provided with a lens and an imaging element. An image captured by the camera function is displayed on the display unit. Examples of the electronic device include a smartphone and a notebook computer.

[0083] (Lighting equipment) FIG. 8 is an exploded perspective view showing an embodiment of the lighting device of the present invention. The lighting device 110 of this embodiment has a housing 111, a light source 112, a circuit board 113, an optical filter 114 that transmits light from the light source 112, and a light diffusion unit 115. The light source 112 is configured using an organic EL element of the present invention and a power supply circuit connected to the organic EL element. The power supply circuit is a circuit that converts AC voltage to DC voltage. The optical filter 114 may be a filter that improves the color rendering of the light source 112. The light diffusion unit 115 can effectively diffuse the light of the light source 112, such as for lighting up, and deliver the light to a wide range. The optical filter 114 and the light diffusion unit 115 are provided on the light emission side of the lighting. If necessary, a cover may be provided on the outermost part.

[0084] The lighting device 110 is, for example, a device that illuminates a room. The lighting device 110 may emit white light, neutral white light, or any other color from blue to red, and may have a dimming circuit for adjusting the light intensity. White light has a color temperature of 4200K, and neutral white light has a color temperature of 5000K. The lighting device 110 may have a color filter.

[0085] Furthermore, the lighting device 110 may have a heat dissipation section. The heat dissipation section dissipates heat inside the device to the outside, and examples of the heat dissipation section include metals with high specific heat, liquid silicon, and the like.

[0086] (Mobile) The moving body of the present invention may be a ship, an aircraft, a drone, etc. The moving body has a body and a lamp provided on the body, and the lamp has the organic EL element of the present invention and is responsible for emitting light to notify the position of the body.

[0087] 9 is a perspective view that shows a model of an automobile as an embodiment of the moving body of the present invention. The automobile 120 of this embodiment has a tail lamp 121 that is a lamp, and turns on the tail lamp 121 when the brakes are applied or the like. The automobile 120 has a vehicle body 123 and a window 122 attached to the vehicle body 123. In this embodiment, at least one of the tail lamp 121 and the window 122 has an organic EL element of the present invention.

[0088] Furthermore, the tail lamp 121 may have a protective member for protecting the organic EL element. The protective member may be made of any material as long as it has a certain degree of strength and is transparent, but it is preferable that the protective member is made of polycarbonate or the like. Polycarbonate may be mixed with a furandicarboxylic acid derivative, an acrylonitrile derivative, or the like.

[0089] The window 122 may be a transparent display unless it is a window for checking the front and rear of the vehicle. When the transparent display has the organic EL element of the present invention, the constituent materials of the electrodes and the like of the organic EL element are made of transparent members.

[0090] (Image capture and display device) The imaging and display device having the organic EL element of the present invention can be applied to a system that can be attached as a wearable device such as glasses (smart glasses), HMD, smart contacts, etc. The imaging and display device used in such application examples has an imaging device capable of photoelectrically converting visible light, and a display device capable of emitting visible light.

[0091] 10(a) illustrates glasses 140, which is an application example of an imaging and display device. An imaging device 142, such as a CMOS sensor or a SPAD, is provided on the front side of a lens 141 of the glasses 140. In addition, a display device (not shown) having an organic EL element of the present invention is provided on the back side of the lens 141.

[0092] The glasses 140 further include a control device 143. The control device 143 functions as a power source that supplies power to the imaging device 142 and the display device according to each embodiment. The control device 143 also controls the operations of the imaging device 142 and the display device. The lens 141 is formed with an optical system for focusing light on the imaging device 142.

[0093] FIG. 10(b) also shows glasses, but the configuration is slightly different from FIG. 10(a). The glasses 150 in FIG. 10(b) have a control device 152, which is equipped with an imaging device corresponding to the imaging device 142 in FIG. 10(a) and a display device having an organic EL element of the present invention. The lens 151 is formed with an imaging device in the control device 152 and an optical system for projecting light emitted from the display device, and an image is projected onto the lens 151. The control device 152 functions as a power source that supplies power to the imaging device and the display device, and controls the operation of the imaging device and the display device. The control device 152 may have a line-of-sight detection unit that detects the line of sight of the wearer. The line of sight may be detected using infrared light. The infrared light emission unit emits infrared light to the eyeball of the user gazing at the displayed image. The imaging unit having a light receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an image of the eyeball. The reduction means for reducing the light from the infrared light emission unit to the display unit in a planar view reduces the deterioration of image quality.

[0094] The gaze of the user with respect to the displayed image is detected from an image of the eyeball obtained by capturing infrared light. Any known method can be applied to gaze detection using the image of the eyeball. As an example, a gaze detection method based on a Purkinje image formed by reflection of irradiated light on the cornea can be used. More specifically, the gaze detection process is performed based on the pupil-corneal reflex method. Using the pupil-corneal reflex method, a gaze vector that indicates the direction (rotation angle) of the eyeball is calculated based on the pupil image and the Purkinje image included in the captured image of the eyeball, thereby detecting the user's gaze.

[0095] The imaging display device of this embodiment may have an imaging device having a light receiving element, and may control the display image of the display device based on the user's line of sight information from the imaging device. Specifically, the display device determines a first field of view area to which the user gazes and a second field of view area other than the first field of view area based on the line of sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than the first field of view area.

[0096] The display area includes a first display area and a second display area different from the first display area, and an area having a high priority is determined from the first display area and the second display area based on line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be determined by an external control device and received. The resolution of the area having a high priority may be controlled to be higher than the resolution of areas other than the area having a high priority. In other words, the resolution of an area having a relatively low priority may be lowered.

[0097] AI may be used to determine the first field of view area and areas with high priority. The AI ​​may be a model configured to estimate the angle of the line of sight and the distance to an object in the line of sight from an image of the eyeball, using an image of the eyeball and the direction in which the eyeball in the image was actually looking as teacher data. The AI ​​program may be included in the display device, the imaging device, or an external device. If included in the external device, it is transmitted to the display device via communication.

[0098] When display control is performed based on visual recognition detection, the present invention is preferably applicable to smart glasses that further include an imaging device for capturing images of the outside world. The smart glasses can display captured outside information in real time. EXAMPLES

[0099] Example 1 In this example, a top-emission organic EL element was fabricated in which the organic EL layers 10a and 10b each had an electron blocking layer and a hole blocking layer in addition to the layer structure shown in Fig. 2. The first organic EL layer 10a and the second organic EL layer 10b each had a blue light-emitting layer.

[0100] A 40 nm thick Ti film was formed on a silicon substrate as the anode 3 by sputtering, and then patterned using photolithography to form a regular hexagonal Ti pixel array and wiring so that the pixel pitch was 4.2 μm. Furthermore, a silicon nitride (SiN) insulating layer was formed on the Ti, and photolithography was used to pattern the pixel array with exposed Ti and the SiN insulating layer that separates it so that the width was 1 μm.

[0101] Next, the substrate and material with the insulating layer formed after washing with water were placed in a vacuum deposition apparatus, and 1.0 × 10 -4 Pa(1×10 -6 Torr), and then UV / ozone cleaning was performed. Then, films were formed up to the first organic EL layer 10a with the layer configuration shown in Table 1 below.

[0102] Next, LiF and Mg were co-deposited from a molybdenum deposition boat at a deposition rate of 0.1 Å / s each to form an intermediate layer 20 with a volume ratio of LiF:Mg=50:50 and a thickness of 2 μm.

[0103] Next, the second organic EL layer 10b and the cathode 5 were formed in the layer configuration shown in Table 1, and then the substrate was transferred to a glove box and sealed with a glass cap containing a desiccant in a nitrogen atmosphere to obtain an organic EL element.

[0104] [Table 1]

[0105] Next, a voltage application device was connected and the characteristics were evaluated. When a voltage was applied to all pixels and the light emission state was observed under a microscope, no light emission was confirmed on the insulating layer, and the organic EL element was in good condition with no uneven light emission.

[0106] The voltage-current characteristics of the obtained organic EL element were measured using a Hewlett-Packard microammeter "4140B," and the emission spectrum and emission luminance were obtained using a Topcon "SR-3." The current efficiency calculated from the applied current value and emission luminance was 2.2 cd / A, and the CIE chromaticity was x=0.14, y=0.10. Figure 11(a) shows the voltage-current characteristics. For comparison, an organic EL element with a single organic EL layer, excluding the intermediate layer 20 and the second organic EL layer 10b, was also produced, and the voltage-current characteristics were measured.

[0107] As a result, the organic EL element of this example required about 2.5 times the voltage to be applied to obtain the same current density as the single-layer organic EL element, and the current efficiency was about twice as high. Therefore, it is presumed that both the first organic EL layer 10a and the second organic EL layer 10b emit light, and the electron injection property of the intermediate layer 20 functions, so that the organic EL element is a stacked organic EL element having an intermediate layer 20 with high resistance.

[0108] Example 2 A stacked organic EL element was produced in the same manner as in Example 1, except that the electron injection layer 15a of the first organic EL layer 10a was not formed. The current efficiency of the obtained organic EL element was 2.3 cd / A, and the CIE chromaticity was x = 0.14, y = 0.10. Figure 11(b) shows the voltage-current characteristics.

[0109] In the organic EL element of this embodiment, the voltage required to obtain the same current density was slightly lower than that of Example 1, but when the light emission state was observed under a microscope, no light emission was observed on the insulating layer, and the organic EL element was excellent with no uneven light emission. In addition, the light emission efficiency was equivalent to that of Example 1.

[0110] Comparative Example 1 A stacked organic EL element was produced in the same manner as in Example 1, except that intermediate layer 20 was formed by co-evaporating Ag and Mg from a tungsten boat at a deposition rate of 0.1 Å / s each to form intermediate layer 20 with a volume ratio of Ag:Mg=50:50 and a thickness of 2 μm. The current efficiency of the obtained organic EL element was 2.5 cd / A, and the CIE chromaticity was x = 0.14, y = 0.11. Figure 12(a) shows the voltage-current characteristics.

[0111] In the organic EL element of this comparative example, the voltage required to obtain the same current density was significantly lower than that of Example 1, and when the light emission state was confirmed under a microscope, light was also emitted from the insulating layer. Furthermore, when a voltage was applied to only some of the pixels, light was also emitted from the adjacent pixels, and it is considered that the resistance of the intermediate layer 20 was low because the intermediate layer 20 was formed only from the metals Ag and Mg, and a current flowed in the surface direction of the intermediate layer 20, resulting in an element in which light was emitted from the insulating layer and adjacent pixels.

[0112] Comparative Example 2 A stacked organic EL element was produced in the same manner as in Example 1, except that the intermediate layer 20 was formed by co-evaporating the organic compound ET2 used in the electron transport layer 14a and Mg at a deposition rate of 0.1 Å / s, respectively, to form an intermediate layer 20 with a volume ratio of ET2:Mg=50:50 and a thickness of 2 μm. The current efficiency of the obtained organic EL element was 1.2 cd / A, and the CIE chromaticity was x = 0.14, y = 0.09. Figure 12(b) shows the voltage-current characteristics.

[0113] In the organic EL element of this comparative example, the voltage required to obtain the same current density was almost the same as that of Example 1, but the current efficiency was reduced by half compared to Example 1. This is believed to be because the electron injection layer 15a of the first organic EL layer 10a and the intermediate layer 20 do not exhibit electron injection properties, and it is believed to indicate that holes pass through the first organic EL layer 10a and the intermediate layer 20, and recombination of holes and electrons occurs only in the second organic EL layer 10b. The reason why the intermediate layer 20 does not exhibit electron injection properties is assumed to be that the LiF used in the electron injection layer 15a cannot be reduced. The reason why Mg cannot be reduced even though it is vapor-deposited on LiF is assumed to be that the compatibility between the organic compound ET2 and Mg is low when the intermediate layer 20 is formed, and Mg does not form a film.

[0114] Comparative Example 3 A laminated organic EL element was produced in the same manner as in Comparative Example 1, except that the electron injection layer 15a of the first organic EL layer 10a was not formed. The current efficiency of the obtained organic EL element was 1.2 cd / A, and the CIE chromaticity was x = 0.14, y = 0.10. Figure 13(a) shows the voltage-current characteristics.

[0115] The characteristics of the organic EL element of this comparative example were almost the same as those of Comparative Example 2, and the organic EL element did not exhibit the electron injection property of the intermediate layer 20. When the electron injection layer 15a was not present, the electron injection property was not exhibited by only Ag and Mg used in the intermediate layer 20, indicating that an alkali metal compound was necessary.

[0116] Comparative Example 4 A multilayer organic EL element was produced in the same manner as in Comparative Example 2, except that the electron injection layer 15a of the first organic EL layer 10a was not formed. The current efficiency of the obtained organic EL element was 1.3 cd / A, and the CIE chromaticity was x = 0.14, y = 0.09. Figure 13(b) shows the voltage-current characteristics.

[0117] The characteristics of the organic EL element of this comparative example were almost the same as those of Comparative Example 2 and Comparative Example 3, and the intermediate layer 20 did not exhibit the electron injection property. It is considered that, without the electron injection layer 15a, the organic compound ET2 and Mg used in the intermediate layer 20 alone do not exhibit the electron injection property, and an alkali metal compound is required. However, since the same result was obtained in Comparative Example 2 in which LiF was used in the electron injection layer 15a, it can be inferred that it is more likely that the organic compound ET2 and Mg have low compatibility and Mg does not form a film.

[0118] Example 3 The electron injection layer 15a of the first organic EL layer 10a was formed from KF, and KF was also used as the alkali metal compound used in the intermediate layer 20. ET5 was used for the electron transport layers 14a and 14b, and the film thickness was set to 10 nm. A stacked organic EL element was fabricated in the same manner as in Example 1 except for the above. The light-emitting state of the obtained organic EL element was observed under a microscope, and no light emission was observed on the insulating layer, showing that the organic EL element was excellent with no uneven light emission. The current efficiency was the same as that of Example 1.

[0119] Example 4 The intermediate layer 20 was made of Group 2 metal Ca, and the hole transport layers 12a and 12b were made of HT19 with a thickness of 3 nm. A stacked organic EL element was fabricated in the same manner as in Example 1 except that the deposition temperature of Ca was higher and the input power was higher. There was no significant difference from Example 1. The light-emitting state of the obtained organic EL element was observed under a microscope, and no light emission was observed on the insulating layer, showing that the organic EL element was excellent with no uneven light emission. The current efficiency was the same as that of Example 1.

[0120] Example 5 A stacked organic EL element was produced in the same manner as in Example 1, except that intermediate layer 20 having a thickness of 2 μm was formed by co-evaporating LiF at a deposition rate of 0.05 Å / s and Mg at a deposition rate of 0.20 Å / s in a volume ratio of LiF:Mg=5:20. When the light-emitting state of the obtained organic EL element was observed under a microscope, light emission was confirmed on the insulating layer, but when a voltage was applied to only some pixels, no light emission was observed in the adjacent pixels, indicating that the organic EL element was excellent. In addition, the current efficiency was equivalent to that of Example 1.

[0121] Example 6 The electron injection layer 15a of the first organic EL layer 10a was formed from Liq, and Liq was also used as the alkali metal compound used in the intermediate layer 20. In addition, HT19 was used for the hole transport layers 12a and 12b, and the film thickness was set to 3 nm. A stacked organic EL element was fabricated in the same manner as in Example 1 except for the above. No light emission was observed on the insulating layer, and the layered organic EL element had no uneven light emission and was in good condition. The current efficiency was the same as that of Example 1.

[0122] Example 7 The light-emitting layer 13a of the first organic EL layer 10a emits red and green light, and the light-emitting layer 13b of the second organic EL layer 10b emits blue light, producing a layered organic EL element that emits white light as a whole. The layer structure is shown in Table 2.

[0123] [Table 2]

[0124] In the organic EL element of this embodiment, light emission from the three dopants of red, green, and blue was confirmed, and it was found that the electron injection property of the intermediate layer 20 was functioning, and both the first organic EL layer 10a and the second organic EL layer 10b were emitting light. When the light-emitting state of the obtained organic EL element was observed under a microscope, no light emission was observed on the insulating layer, and the organic EL element was in good condition with no uneven light emission.

[0125] Example 8 A laminated organic EL element was fabricated in the same manner as in Example 7, except that the electron injection layer 15a of the first organic EL layer 10a was formed from Cs2CO3, and Cs2CO3 was also used as the alkali metal compound for the intermediate layer 20. Cs2CO3 was packed in a platinum cell, and the cell was placed on a tungsten boat and heated for deposition. No decomposition such as blackening was observed after deposition.

[0126] In the organic EL element of this embodiment, as in Example 7, light emission from the three dopants of red, green, and blue was confirmed, and it was found that the electron injection property of the intermediate layer 20 was functioning, and both the first organic EL layer 10a and the second organic EL layer 10b were emitting light. When the light-emitting state of the obtained organic EL element was observed under a microscope, no light emission was observed on the insulating layer, and the organic EL element was in good condition with no uneven light emission. [Explanation of symbols]

[0127] 10, 10a, 10b: organic EL layer, 20: intermediate layer, 15a, 15b: electron injection layer, 12a, 12b: hole injection layer, 48: transistor, 90: imaging device, 100: electronic device, 01: display unit, 103: housing, 110: lighting device, 112: light source, 114: optical filter, 115: light diffusion unit

Claims

1. An organic electroluminescence element having a pair of electrodes and at least two organic electroluminescence layers disposed between the pair of electrodes and overlapping each other via an intermediate layer, the intermediate layer contains an alkali metal compound, a reduced form of the alkali metal compound, and a metal element of Group 2 of the periodic table; 2. An organic electroluminescence device, wherein the intermediate layer is a co-deposition layer of the alkali metal compound and the Group 2 metal element.

2. An organic electroluminescence element having a pair of electrodes and at least two organic electroluminescence layers overlapping each other via an intermediate layer, the organic electroluminescence layer being disposed between the pair of electrodes, the intermediate layer contains an alkali metal compound, a reduced form of the alkali metal compound, and a metal element of Group 2 of the periodic table; an organic electroluminescence device, wherein the intermediate layer is made of only the alkali metal compound, a reduced form of the alkali metal compound, and the Group 2 metal element;

3. 3. The organic electroluminescence device according to claim 2, wherein the intermediate layer is a co-deposition layer of the alkali metal compound and the Group 2 metal element.

4. 2. The organic electroluminescence device according to claim 1, wherein the intermediate layer is made of only the alkali metal compound, a reduced form of the alkali metal compound, and the Group 2 metal element.

5. 5. The organic electroluminescent element according to claim 1, wherein the organic electroluminescent layer located closer to the anode than the intermediate layer has an electron injection layer in contact with the intermediate layer, and the electron injection layer contains the alkali metal compound contained in the intermediate layer and a reduced form of the alkali metal compound.

6. 6. The organic electroluminescence device according to claim 5, wherein the electron injection layer is a single vapor-deposited layer of the alkali metal compound.

7. 7. The organic electroluminescence device according to claim 1, wherein the intermediate layer contains the Group 2 metal element in an amount of 75% by volume or less.

8. 8. The organic electroluminescence device according to claim 1, wherein the alkali metal compound is any one of a lithium halide and a lithium quinolinol complex.

9. 8. The organic electroluminescence device according to claim 1, wherein the alkali metal compound is either lithium fluoride or potassium fluoride.

10. 8. The organic electroluminescence device according to claim 1, wherein the alkali metal compound is cesium carbonate.

11. 11. The organic electroluminescence device according to claim 1, wherein the Group 2 metal element is any one of magnesium, calcium, and strontium.

12. 11. The organic electroluminescence device according to claim 1, wherein the Group 2 metal element is magnesium.

13. 13. The organic electroluminescence element according to claim 1, wherein the organic electroluminescence layer located closer to the cathode than the intermediate layer has a hole injection layer in contact with the intermediate layer.

14. An exposure light source for an electrophotographic image forming apparatus, comprising the organic electroluminescence element according to claim 1 .

15. A display device comprising a plurality of pixels, at least one of the plurality of pixels being the organic electroluminescence element according to claim 1 .

16. 16. The display device according to claim 15, further comprising a transistor connected to the organic electroluminescence element.

17. an optical unit having a plurality of lenses, an image sensor that receives light that has passed through the optical unit, and a display unit that displays an image captured by the image sensor; An imaging device, wherein the display section comprises the organic electroluminescence element according to claim 1 .

18. 14. An electronic device comprising: a display unit having the organic electroluminescence element according to claim 1; a housing in which the display unit is provided; and a communication unit provided in the housing and configured to communicate with an external device.

19. 14. An illumination device comprising: a light source having the organic electroluminescence element according to claim 1; and at least one of a light diffusion section and an optical filter that transmits light emitted by the light source.

20. A moving body comprising: a lamp having the organic electroluminescence element according to claim 1 ; and a body on which the lamp is provided.

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