Organic electroluminescent element, method for manufacturing an organic electroluminescent element, display device, and lighting device

Abstract

To provide an organic electroluminescent element with a tandem structure including an electric charge generation unit having superior electron / hole injection properties.SOLUTION: An organic electroluminescent element 1 comprises an anode 3, a cathode 6, a plurality of light-emitting units 4-1, 4-2 located between the anode 3 and cathode 6, and an electric charge generation unit 5-1 located between the respective light-emitting units 4-1, 4-2. The light-emitting units 4-1, 4-2 have a light-emitting layer 9 and the electric charge generation unit 5-1 has an organic material layer 12 and a metal layer 13 in order from the side of the anode 3. The organic material layer 12 includes a coordination-bondable organic material and the metal layer 13 includes a metal element.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an organic electroluminescent element (hereinafter, electroluminescence (electric field emission) may be written as "EL"), a method for manufacturing an organic electroluminescent element, a display device, and a lighting device. [Background technology]

[0002] Organic EL elements are thin, flexible, and adaptable. Furthermore, display devices using organic EL elements offer higher brightness and higher resolution compared to currently dominant liquid crystal (LCD) and plasma (plasma) displays. Organic EL displays also have a wider viewing angle than LCDs. For these reasons, the use of organic EL displays in televisions, mobile phones, and other applications is expected to expand in the future. Furthermore, organic EL elements are also expected to be used in lighting devices.

[0003] In recent years, tandem-structured organic EL elements, which have multiple light-emitting layers (light-emitting units) between the cathode and anode, have been investigated as organic EL elements (Patent Documents 1 and 2, and Non-Patent Documents 1 to 5). In this tandem-structured organic EL element, multiple light-emitting units are separated by charge-generating units (charge-generating layers). As a result, when a current of the same current density is applied, higher brightness emission can be obtained compared to organic EL elements with a single layer of light-emitting units. Therefore, it is possible to improve the current efficiency and extend the lifespan of organic EL elements. Furthermore, multiple light-emitting units can be provided with light-emitting layers of different colors. By combining red, green, and blue, or blue and yellow, white light can be obtained.

[0004] In this specification, "light-emitting unit" refers to an element of a conventional organic EL device that has a layer structure including at least one light-emitting layer, excluding the anode electrode and cathode electrode. In addition, the "charge generation unit" in this specification is a layer structure formed between a "light-emitting unit" and another "light-emitting unit", and it plays a role of injecting electrons into the light-emitting unit on the anode side and holes into the light-emitting unit on the cathode side. That is, the "charge generation unit" is formed between the light-emitting layer of the "light-emitting unit" on the anode side and the light-emitting layer of the "light-emitting unit" on the cathode side, or between the electron transport layer of the "light-emitting unit" on the anode side and the hole transport layer of the "light-emitting unit" on the cathode side.

[0005] In order to cause this tandem-structured organic EL device to emit light at a low voltage, it is necessary to efficiently inject electrons and holes from the charge generation unit into the adjacent light-emitting unit. Conventionally, various materials and configurations have been reported as charge generation units to obtain good characteristics. However, as shown in Patent Documents 1 and 2 and Non-Patent Documents 2 to 5, configurations including compounds containing alkali metals such as lithium and cesium are often used. In addition, in order to obtain better characteristics, as shown in Non-Patent Documents 2, 4, and 5, a charge generation unit including a configuration in which a metal layer such as aluminum is laminated adjacent to a compound containing an alkali metal is used.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

[0008] However, alkali metals are highly reactive with the atmosphere and prone to degradation. Furthermore, if alkali metals are used in the charge generation unit between light-emitting units, there is a concern that ionized alkali metals may diffuse to the cathode-side light-emitting unit when voltage is applied, causing the light-emitting unit to degrade. Furthermore, these charge generation layers lack sufficient electron-hole injection capabilities for further lowering the voltage of the tandem structure.

[0009] The present invention has been made in view of the above circumstances, and aims to provide an organic EL element in a tandem structure including a charge generation unit having excellent electron-hole injection properties, a method for manufacturing the same, a display device and a lighting device equipped with such an organic EL element. [Means for solving the problem]

[0010] To solve the above problems, the present inventors focused on the coordinate bonding between an organic material having a site capable of coordinating bonds, such as an organic material having an electron-donating nitrogen atom in a heterocycle, and the metal element to which it is coordinated, as well as the orientation of the coordinate bonding, in a charge generation unit.

[0011] Furthermore, by using a laminated film in which an organic layer (organic material layer) made of an organic material having a portion capable of coordinating and bonding to the anode side is provided as a charge generation unit between the light-emitting units of a tandem organic EL element, and a metal layer which is the destination for coordination is provided directly above it, the driving voltage of the organic EL element can be reduced, and the above problem can be solved, which led to the present invention.

[0012] Although the detailed mechanism is not entirely clear, it is presumed that when coordination bonds are formed between the organic material in the organic material layer and the metal elements in the metal layer, electrons move from the organic material layer to the metal layer, creating an internal electric field that is positive on the organic material layer side and negative on the metal layer side. This is thought to improve electron injection into the anode-side light-emitting unit and hole injection into the cathode-side light-emitting unit.

[0013] This invention was completed based on the above findings, and its gist is as follows.

[0014] [1] An organic electroluminescent element comprising an anode, a cathode, a plurality of light-emitting units located between the anode and the cathode, and a charge-generating unit located between each light-emitting unit, The light-emitting unit has a light-emitting layer, The charge generation unit has, in order from the anode side, an organic material layer and a metal layer. The aforementioned organic material layer includes an organic material capable of coordination bonding, An organic electroluminescent element characterized in that the metal layer contains a metal element.

[0015] [2] The organic electroluminescent element according to [1], wherein the metal layer is made of aluminum.

[0016] [3] The organic electroluminescent element according to [1] or [2], wherein the thickness of the metal layer is 5 nm or less.

[0017] [4] The organic electroluminescence device according to any one of [1] to [3], wherein the organic material layer contains a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1).

Chemical formula

[0018] [5] The organic electroluminescence device according to [4], wherein n 1 in the general formula (1) is 2 or 3.

[0019] [6] The organic electroluminescence device according to any one of [1] to [3], wherein the organic material layer contains a compound having a structure represented by the following general formula (2).

Chemical formula

[0020] [7] The organic electroluminescence device according to [6], wherein n 2 in the general formula (2) is 0.

[0021] A display device characterized by comprising an organic electroluminescent element as described in any of [8] [1] to [7].

[0022] A lighting device characterized by comprising an organic electroluminescent element as described in any of [9] [1] to [7].

[0023]

[10] comprising an anode, a cathode, a plurality of light-emitting units located between the anode and the cathode, and a charge-generating unit located between each light-emitting unit, The light-emitting unit has a light-emitting layer, The method for manufacturing an organic electroluminescent element, wherein the charge generation unit comprises, in order from the anode side, an organic material layer and a metal layer, A step of forming the organic material layer using an organic material capable of coordination bonding, A step of forming the metal layer using a metal element, A method for producing an organic electroluminescent element, characterized by containing the following: [Effects of the Invention]

[0024] The tandem-structured organic EL element of the present invention has a low driving voltage and excellent operating life. Furthermore, because the display device and lighting device of the present invention are equipped with the tandem-structured organic EL elements of the present invention, they have characteristics such as low driving voltage and excellent driving life. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic cross-sectional view illustrating an organic EL element with a tandem structure having n light-emitting units according to the present invention. [Figure 2] This is a schematic cross-sectional view illustrating an example of a tandem structure organic EL element of the present invention. [Figure 3] This graph shows the relationship between applied voltage and brightness for the organic EL elements fabricated in Examples 1-3 and Comparative Example 1. [Figure 4]This graph shows the relationship between the elapsed time from the start of operation and the brightness of the organic EL elements fabricated in Examples 1-3 and Comparative Example 1. [Modes for carrying out the invention]

[0026] The organic EL element, the method for manufacturing the organic EL element, the display device, and the lighting device of the present invention will be described in detail below based on embodiments thereof.

[0027] <Organic EL element> The organic EL element of the present invention comprises an anode, a cathode, a plurality of light-emitting units located between the anode and the cathode, and a charge-generating unit located between each light-emitting unit. The organic electroluminescent element of the present invention is characterized in that the light-emitting unit has a light-emitting layer, and the charge-generating unit has, in order from the anode side, an organic material layer and a metal layer, the organic material layer contains an organic material capable of coordination bonding, and the metal layer contains a metal element. The organic EL element of the present invention may have a forward structure in which the anode is placed on the substrate, or a reverse structure in which the cathode is placed on the substrate. Furthermore, the organic EL element of the present invention may be a bottom emission type that extracts light from the substrate side, or a top emission type that extracts light from the top of the substrate.

[0028] As described above, although the detailed mechanism is not entirely clear, it is presumed that in the organic EL element of the present invention, when a coordination bond is formed between the organic material of the organic material layer and the metal element of the metal layer, electrons move from the organic material layer to the metal layer, creating an internal electric field where the organic material layer is positive and the metal layer is negative. This improves electron injection into the anode-side light-emitting unit and hole injection into the cathode-side light-emitting unit. Furthermore, the organic EL element of the present invention is equipped with a charge generation unit that has excellent electron-hole injection capabilities, resulting in a low driving voltage and excellent operating life.

[0029] Next, the organic EL element of the present invention will be described in detail with reference to an example. Figure 1 is a schematic cross-sectional view illustrating the tandem organic EL element having n light-emitting units of the present invention. The organic EL element of this embodiment shown in Figure 1 has a plurality (n) of light-emitting units 4-1, 4-2, ..., 4-n and charge-generating units 5-1, 5-2, ..., 5-(n-1) between the anode 3 and the cathode 6. As shown in Figure 1, the elements are stacked in the following order from the substrate 2: anode 3, light-emitting unit 4-1, charge-generating unit 5-1, light-emitting unit 4-2, charge-generating unit 5-2, charge-generating unit 5-(n-1), charge-generating unit 5-(n-1), light-emitting unit 4-n, and cathode 6 (where n is an integer of 2 or more). There is no limit to the number of units, but a tandem organic EL element with a value of n of 2 or 3 is preferred so as not to make the driving voltage too high and the element fabrication too complex. Figure 2 is a schematic cross-sectional view illustrating an example of an organic EL element of the present invention. The organic EL element 1 of this embodiment shown in Figure 2 has a laminated structure in which an anode 3, a hole injection layer 7, a hole transport layer 8, a light-emitting layer 9, an electron transport layer 10, an organic material layer 12, a metal layer 13, a hole injection auxiliary layer 14, a hole transport layer 8, a light-emitting layer 9, an electron transport layer 10, an electron injection layer 11, and a cathode 6 are formed in this order on a substrate 2. As described above, the laminated structure of the organic material layer 12 and the metal layer 13, which are components of the present invention, exists between the two light-emitting layers 9.

[0030] In this embodiment, a forward-structured organic EL element 1 is used as an example for explanation, but the organic EL element of the present invention may also be an inverted structure in which a cathode is placed between the substrate and the light-emitting layer. Even when the organic EL element of the present invention has an inverted structure, it has a laminated structure of the above-mentioned organic material layer and metal layer between the light-emitting units (preferably a laminated structure in which the organic material layer and metal layer are in contact), similar to the forward-structured case. The materials, thicknesses, and encapsulation of each layer constituting the organic EL element 1 described below are the same for the inverted organic EL element, except for the materials of the cathode and anode described later.

[0031] "substrate" Examples of materials for substrate 2 include resin materials and glass materials. Examples of resin materials used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, and polyarylate. Using a resin material for the substrate 2 is preferable because it allows for the production of an organic EL element 1 with excellent flexibility. Examples of glass materials used for substrate 2 include quartz glass and soda glass.

[0032] If the organic EL element 1 is a bottom-emission type, a transparent substrate is used as the material for the substrate 2. If the organic EL element 1 is of the top-emission type, the substrate 2 may be made of an opaque substrate as well as a transparent substrate. Examples of opaque substrates include substrates made of ceramic materials such as alumina, substrates in which an oxide film (insulating film) is formed on the surface of a metal plate such as stainless steel, and substrates made of resin materials.

[0033] The average thickness of substrate 2 can be determined according to the material of substrate 2, and is preferably 0.1 to 30 mm, and more preferably 0.1 to 10 mm. The average thickness of substrate 2 can be measured using a digital multimeter or calipers.

[0034] "anode" The anode 3 is formed in direct contact with the substrate 2. Examples of materials for anode 3 include oxides such as ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorinated tin oxide), In3O3, SnO2, Sb-containing SnO2, and Al-containing ZnO, as well as conductive materials such as Al, Au, Pt, Ag, Cu, or alloys containing these. Among these, it is preferable to use ITO, IZO, or FTO as the material for anode 3. The average thickness of the anode 3 is not particularly limited, but is preferably 10 to 500 nm, and more preferably 100 to 200 nm. The average thickness of anode 3 can be measured using a stylus-type step meter, spectroscopic ellipsometry, or a quartz crystal film thickness meter.

[0035] "cathode" Materials used for cathode 6 include ITO, IZO, Au, Pt, Ag, Cu, Al, or alloys containing these materials. Among these, it is preferable to use ITO, IZO, Au, Ag, or Al as the material for cathode 6. The average thickness of the cathode 6 is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 30 to 150 nm. Furthermore, even when an opaque material is used as the material for the cathode 6, by setting the average thickness to, for example, 10 to 30 nm, it can be used as a transparent cathode in a top-emission type organic EL device. The average thickness of cathode 6 can be measured during film formation using a quartz crystal film thickness gauge.

[0036] (Light-emitting unit) The following describes the layers that make up the light-emitting unit. The light-emitting unit has at least a light-emitting layer 9, and may further have a hole injection layer 7, a hole transport layer 8, an electron transport layer 10, an electron injection layer 11, etc. In Figure 2, the light-emitting unit 4-1 located on the anode side has, in order from the anode side, a hole injection layer 7, a hole transport layer 8, a light-emitting layer 9, and an electron transport layer 10, and the light-emitting unit 4-2 located on the cathode side has, in order from the anode side, a hole transport layer 8, a light-emitting layer 9, an electron transport layer 10, and an electron injection layer 11.

[0037] "Hole injection layer" The hole injection layer 7 may be made of an inorganic material or an organic material. The inorganic material is not particularly limited, but for example, one or more metal oxides such as vanadium oxide (V2O5), molybdenum oxide (MoO3), and ruthenium oxide (RuO2) can be used. As organic materials, low molecular weight materials such as dipyradino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonnitrile (HAT-CN) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), as well as poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS) can be used. Alternatively, the hole injection layer 7 may be a laminated structure consisting of an organic material layer containing a coordination-bondable organic material, followed by a metal layer containing a metal element, in that order from the anode side.

[0038] The average thickness of the hole injection layer 7 is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 5 to 50 nm. The average thickness of the hole injection layer 7 can be measured, for example, by a stylus step meter or spectroscopic ellipsometry.

[0039] "Hole transport layer" Any material that can be commonly used as a material for the hole transport layer 8 can be used, and these materials may also be used in mixture form. Specifically, as materials for the hole transport layer 8, for example, arylcycloalkane compounds such as N4,N4'-bis(dibenzo[b,d]thiophen-4-yl)-N4,N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), 1,1-bis(4-di-para-triaminophenyl)cyclohexane, 1,1'-bis(4-di-para-tolylaminophenyl)-4-phenyl-cyclohexane, 4,4',4''-trimethyltriphenylamine, N,N,N',N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, N,N' -Diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1), N,N'-diphenyl-N,N'-bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD2), N,N,N',N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD3), N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), TPTE, N3,N3'''-bis(dibenzo[b,d]thiophene Arylamine compounds such as N-4-yl)-N3,N3'''-diphenyl-[1,1':2',1'':2'',1'''-quaterphenyl]-3,3'''-diamine (4DBTP3Q) and N-([1,1'-biphenyl]-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-fluoren-2-amine (HT-01), phenylenediamine compounds such as N,N,N',N'-tetra(meth-tolyl)-meth-phenylenediamine (PDA), carbazole, N-isopropyl Carbazole compounds such as lucarbazole and N-phenylcarbazole, stilbene compounds such as stilbene and 4-di-p-tolylaminostilbene, oxazole compounds such as OxZ, triphenylmethane compounds such as triphenylmethane and m-MTDATA, pyrazoline compounds such as 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline, benzine (cyclohexadiene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, 1,3,4-oxadiazole, 2,Oxadiazole compounds such as 5-di(4-dimethylaminophenyl)-1,3,4-oxadiazole, anthracene compounds such as anthracene, 9-(4-diethylaminostyryl)anthracene, fluorenone compounds such as fluorenone, 2,4,7-trinitro-9-fluorenone, 2,7-bis(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone, aniline compounds such as polyaniline, silane compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo-(3,4-c)pyrrolopyrrole, fluorene compounds such as fluorene, porphyry Examples include phosphorus, porphyrin compounds such as metallic tetraphenylporphyrin, quinacridone compounds such as quinacridone, metallic or metal-free phthalocyanine compounds such as phthalocyanine, copper phthalocyanine, tetra(t-butyl)copper phthalocyanine, and iron phthalocyanine, metallic or metal-free naphthalocyanine compounds such as copper naphthalocyanine, vanadyl naphthalocyanine, and monochlorogallium naphthalocyanine, and benzidine compounds such as N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine and N,N,N',N'-tetraphenylbenzidine. One or more of these can be used. These hole transport layer 8 materials can also be used as mixtures with other compounds.

[0040] The average thickness of the hole transport layer 8 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 20 to 100 nm. The average thickness of the hole transport layer 8 can be measured, for example, by a stylus step meter or spectroscopic ellipsometry.

[0041] "Luminous layer" Any material that can be commonly used as a material for the light-emitting layer 9 may be used to form the light-emitting layer 9, or these may be used in mixture form. Specifically, for example, the light-emitting layer 9 may contain bis[2-(2-benzothiazolyl)phenolate]zinc(II) (Zn(BTZ)2) and tris[1-phenylisoquinoline]iridium(III) (Ir(piq)3). Furthermore, the material forming the light-emitting layer 9 may be a low-molecular-weight compound or a high-molecular-weight compound. In this invention, a low-molecular-weight material means a material that is not a high-molecular-weight material (polymer), and does not necessarily mean an organic compound with a low molecular weight.

[0042] Examples of polymer materials that form the light-emitting layer 9 include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly(di-phenylacetylene) (PDPA), poly(alkylphenylacetylene) (PAPA); poly(para-phenylene vinylene) (PPV), poly(2,5-dialkoxy-para-phenylene vinylene) (RO-PPV), cyano-substituted-poly(para-phenylene vinylene) (CN-PPV), and poly(2-di Poly(p-phenylenevinylene) compounds such as methyloctylsilyl-p-phenylenevinylene (DMOS-PPV) and poly(2-methoxy,5-(2'-ethylhexoxy)-p-phenylenevinylene) (MEH-PPV); polythiophene compounds such as poly(3-alkylthiophene) (PAT) and poly(oxypropylene)triol (POPT); poly(9,9-dialkylfluorene) (PDAF), poly(dioctylfluorene-a Polyfluorene compounds such as poly(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl)(PF2 / 6am4), poly(9,9-dioctyl-2,7-divinylenefluorenyl-ortho-co(anthracene-9,10-diyl)), poly(para-phenylene)(PPP), poly(1,5-dialkoxy-para-phenylene) Examples include poly(p-phenylene) compounds such as (RO-PPP); polycarbazole compounds such as poly(N-vinylcarbazole) (PVK); polysilane compounds such as poly(methylphenylsilane) (PMPS), poly(naphthylphenylsilane) (PNPS), and poly(biphenylylphenylsilane) (PBPS); and boron compound polymer materials described in Japanese Patent Publication No. 2011-184430 and Japanese Patent Publication No. 2012-151148.

[0043] Examples of low molecular weight materials that form the light-emitting layer 9 include three-coordinate iridium complexes having 2,2'-bipyridine-4,4'-dicarboxylic acid as a ligand, such as Factlis(2-phenylpyridine)iridium(Ir(ppy)3), fac-tris(3-methyl-2-phenylpyridinato-N,C2'-)iridium(III)(Ir(mppy)3), 8-hydroxyquinolinealuminum(Alq3), tris(4-methyl-8-quinolinoleate)aluminum(III)(Almq3), 8-hydroxyquinolinezinc(Znq2), and (1,10-phenantrolyl Various metal complexes such as (n)-tris-(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dionete)europium(III)(Eu(TTA)3(phen)), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II); benzene compounds such as distyrylbenzene (DSB) and diaminodistyrylbenzene (DADSB); naphthalene compounds such as naphthalene and Nile Red; phenanthrene compounds such as phenanthrene; and compounds such as chrysene and 6-nitrochrysene. Chrycene compounds; perylene, perylene compounds such as N,N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-di-carboximide (BPPC); coronene compounds such as coronene; anthracene compounds such as anthracene, bis-styrylanthracene, (9,10-bis(4-(9Hcarbazole-9-yl)-2,6-dimethylphenyl)-9,10-diboranthracene (CzDBA); pyrene compounds such as pyrene; 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminostyryl) Pyran compounds such as -4H-pyran (DCM); acridine compounds such as acridine; stilbene compounds such as stilbene; thiophene compounds such as 2,5-dibenzoxazolethiophene; benzoxazole compounds such as benzoxazole; benzimidazole compounds such as benzimidazole; benzothiazole compounds such as 2,2'-(para-phenylenedivinylene)-bisbenzothiazole; butadiene compounds such as bistyryl(1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene;Naphthalimide compounds such as naphthalimide; coumarin compounds such as coumarin; perinone compounds such as perinone; oxadiazole compounds such as oxadiazole; aldazine compounds; cyclopentadiene compounds such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP); quinacridone compounds such as quinacridone and quinacridone red; pyridine compounds such as pyrrolopyridine and thiadiazolopyridine; 2,4-diphenyl-6-bis(12- Examples include triazine compounds such as phenylindoro)[2,3-a]carbazole-11-yl)-1,3,5-triazine (DIC-TRZ); spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene; metallic or metal-free phthalocyanine compounds such as phthalocyanine (H2Pc) and copper phthalocyanine; and boron compound materials described in Japanese Patent Publication No. 2009-155325, Japanese Patent Publication No. 2011-184430, and Japanese Patent Publication No. 2012-151149. Furthermore, examples of host materials for the light-emitting layer include carbazole compounds such as 4,4'-bis(9H-carbazole-9-yl)biphenyl (CPB), silicon compounds, phenanthroline compounds, and triphenylene compounds.

[0044] The average thickness of the light-emitting layer 9 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 20 to 100 nm. The average thickness of the light-emitting layer 9 may be measured using a stylus-type step meter, or it may be measured using a quartz crystal thickness meter during the deposition of the light-emitting layer 9.

[0045] "Electron transport layer" Any material that can be commonly used as an electron transport layer material may be used for the electron transport layer 10. Specifically, the materials for the electron transport layer 10 include phosphine oxide derivatives such as phenyl-dipyrenylphosphine oxide (POPy2), pyridine derivatives such as tris-1,3,5-(3'-(pyridin-3''-yl)phenyl)benzene (TmPhPyB), quinoline derivatives such as 2-(3-(9-carbazolyl)phenyl)quinoline (mCQ), and pyrimidines such as 2-phenyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine (BPyPPM). Derivatives, pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), triazine derivatives such as 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT), triazole derivatives such as 3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), oxazole derivatives, 2-(4-biphenylyl)-5-(4-tert-butylphenyl Oxadiazole derivatives such as -1,3,4-oxadiazole (PBD), imidazole derivatives such as 2,2',2''-(1,3,5-bentriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic ring tetracarboxylic anhydrides such as naphthalene and perylene, and various metals such as bis[2-(2-hydroxyphenyl)benzothiazolat]zinc (Zn(BTZ)2) and tris(8-hydroxyquinolinato)aluminum (Alq3). Examples include complexes, organosilane derivatives such as silole derivatives like 2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), and boron-containing compounds described in Japanese Patent Publication No. 2013-239691, International Publication No. 2014 / 133141, Japanese Patent Publication No. 2016-172728, Japanese Patent Publication No. 2016-199507, and Japanese Patent Publication No. 2016-199508. One or more of these can be used. Among these electron transport layer 10 materials, it is particularly preferable to use phosphine oxide derivatives such as POPy2, metal complexes such as Alq3, and pyridine derivatives such as TmPhPyB. In addition to the materials mentioned above, various hydrocarbon compounds having aromatic rings, such as aromatic hydrocarbon compounds, compounds having nitrogen-boron bonds, π-electron-rich heteroaromatic compounds containing aromatic rings such as pyrrole rings, furan rings, and thiophene rings, and compounds containing silole rings can also be used.

[0046] The average thickness of the electron transport layer 10 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 20 to 100 nm. The average thickness of the electron transport layer 10 can be measured by a stylus-type step meter and spectroscopic ellipsometry.

[0047] "Electron injection layer" The material used for the electron injection layer 11 may be either an organic or inorganic compound. If the electron injection layer 11 is made of an inorganic compound, for example, alkali metals, alkaline earth metals, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, cesium carbonate, etc., can be used. If the electron injection layer 11 is made of an organic compound, for example, 8-quinolinolatritium (Liq) can be used. The electron injection layer 11 can be made of a compound having the structure represented by the general formula (1) or a compound having the structure represented by the general formula (2), and the compound having the structure represented by the general formula (1) or the compound having the structure represented by the general formula (2) is a suitable material for the electron injection layer 11.

[0048] The electron injection layer 11 may be a single film made of one of these materials, or it may be a mixed film with the material used in the electron transport layer 10. If a mixed film is used as the electron transport layer 10, it also serves the role of the electron injection layer, and there is no need to form the electron injection layer 11.

[0049] The average thickness of the electron injection layer 11 can range from 0.5 nm to several μm, but is preferably 0.5 to 10 nm, and more preferably 1 to 5 nm, in order to create an organic EL element that can be driven at a low voltage. The average thickness of the electron injection layer 11 can be measured by a stylus step meter or spectroscopic ellipsometry.

[0050] (Charge generation unit) The layers that make up the charge generation unit are described below. The charge generation unit has an organic material layer and a metal layer, and may have other layers as well. In Figure 2, the charge generation unit 5-1 has, in order from the anode side, an organic material layer 12, a metal layer 13, and a hole injection auxiliary layer 14.

[0051] "Organic material layer" The organic material layer 12 improves hole injection by forming a complex with the metal layer 13. The organic material layer 12 contains an organic material capable of coordination bonding. Among the organic materials capable of coordination bonding, an organic material having substituents containing nitrogen atoms is preferred, and an organic material having a heterocyclic fused ring structure containing nitrogen atoms is even more preferred.

[0052] For example, the organic material layer 12 preferably contains a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1) as an organic material capable of coordination bonding.

[0053] [ka] (In general formula (1), R 1 n represents an aromatic hydrocarbon group which may have substituents, an aromatic heterocyclic group, an arylalkylene group, a 2- to 4-valent linear or cyclic hydrocarbon group, or a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. 1 (This is an integer between 1 and 4.)

[0054] In the above general formula (1), R 1This represents an aromatic hydrocarbon group which may have substituents, an aromatic heterocyclic group, an arylalkylene group, a 2- to 4-valent linear or cyclic hydrocarbon group, or a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. The aromatic hydrocarbon group and aromatic heterocyclic group are preferably those having 3 to 30 carbon atoms, more preferably those having 4 to 24 carbon atoms, and even more preferably those having 5 to 20 carbon atoms. Aromatic hydrocarbon groups include compounds consisting of only one aromatic ring, such as benzene; compounds in which multiple aromatic rings are directly bonded to one carbon atom, such as biphenyl and diphenylbenzene; and groups formed by removing one to four hydrogen atoms from any of the aromatic rings of fused ring aromatic hydrocarbon compounds, such as naphthalene, anthracene, phenanthrene, and pyrene. Aromatic heterocyclic groups include compounds consisting of only one aromatic heterocyclic ring, such as thiophene, furan, pyrrole, oxazole, oxadiazole, thiazole, thiadiazole, imidazole, pyridine, pyrimidine, pyrazine, and triazine; compounds in which multiple of these compounds consisting of only one aromatic heterocyclic ring are directly bonded to each other by a single carbon atom (such as bipyridine); and groups formed by removing 1 to 4 hydrogen atoms from any aromatic heterocyclic ring of fused cyclic heteroaromatic hydrocarbon compounds such as quinoline, quinoxaline, benzothiophene, benzothiazole, benzimidazole, benzoxazole, indole, carbazole, dibenzofuran, dibenzothiophene, acridine, and phenanthroline. Examples of arylalkylene groups include groups that combine the above-mentioned aromatic hydrocarbon group with an alkylene group having 1 to 3 carbon atoms. The 2-4 valent linear or cyclic hydrocarbon group is preferably one with 1 to 12 carbon atoms, more preferably one with 1 to 6 carbon atoms, and even more preferably one with 1 to 4 carbon atoms. The linear hydrocarbon group may be linear or branched. Also, R 1 This may also be a group formed by combining two or more of the above-mentioned aromatic hydrocarbon groups, aromatic heterocyclic groups, arylalkylene groups, or divalent to tetravalent chain hydrocarbon groups. Furthermore, R1 The group may be formed by combining one or more of the above-mentioned aromatic hydrocarbon groups, aromatic heterocyclic groups, arylalkylene groups, or 2- to 4-valent linear hydrocarbon groups with a nitrogen atom. Examples of such groups include trialkylamines such as trimethylamine and groups formed by removing 1 to 4 hydrogen atoms from triphenylamine.

[0055] The above-mentioned aromatic hydrocarbon group, aromatic heterocyclic group, or arylalkylene group may have one or more monovalent substituents. Monovalent substituents include fluorine atoms; haloalkyl groups such as fluoromethyl, difluoromethyl, and trifluoromethyl groups; linear or branched alkyl groups with 1 to 20 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert-butyl groups; cyclic alkyl groups with 5 to 7 carbon atoms such as cyclopentyl, cyclohexyl, and cycloheptyl groups; methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentyloxy, hexyloxy, and heptyloxy groups. Linear or branched alkoxy groups with 1 to 20 carbon atoms, such as oxy groups and octyloxy groups; nitro groups; cyano groups; alkylamino groups with alkyl groups with 1 to 10 carbon atoms, such as methylamino groups, ethylamino groups, dimethylamino groups, and diethylamino groups; cyclic amino groups such as pyrrolidino groups, piperidino groups, and morpholino groups; diarylamino groups such as diphenylamino groups and carbazolyl groups; acyl groups such as acetyl groups, propionyl groups, and butyryl groups; alkenyl groups with 2 to 30 carbon atoms, such as styryl groups; halogen atoms such as fluorine atoms, and alkyl groups with 1 to 20 carbon atoms, alkoxy groups A C5-C20 aryl group (specific examples of aryl groups are the same as those for aromatic hydrocarbon groups above) which may be substituted with a C1 group, an amino group, etc.; a C4-C40 heterocyclic group containing one or more C1-C4 nitrogen, sulfur, or oxygen atoms which may be substituted with a halogen atom such as a fluorine atom, or a C1-C20 alkyl group, an alkoxy group, an amino group, etc. (The heterocyclic group may consist of only one ring, or may be a compound in which multiple compounds consisting of only one aromatic heterocyclic ring are directly bonded to each other by a single carbon atom, or may be a fused heterocyclic group. Specific examples of heterocyclic groups are as follows: This includes specific examples of aromatic heterocyclic groups such as thiophene rings, furan rings, pyrrole rings, benzothiophene rings, benzofuran rings, indole rings, dibenzothiophene rings, dibenzofuran rings, carbazole rings, thiazole rings, benzothiazole rings, oxazole rings, benzoxazole rings, imidazole rings, benzimidazole rings, pyridine rings, pyrimidine rings, pyrazine rings, pyridazine rings, triazine rings, quinoline rings, isoquinoline rings, quinoxaline rings, benzothiadiazole rings, and phenanthridine rings. Examples include ester groups and thioether groups.These groups may also be substituted with halogen atoms, heteroatoms, alkyl groups, aromatic rings, etc.

[0056] n in the general formula (1) above 1 This is an integer from 1 to 4, but is preferably 2 or 3.

[0057] Specific examples of hexahydropyrimidopyrimidine compounds having the structure represented by the general formula (1) above include, for example, the compounds represented by the following structural formulas (3-1) to (3-34). [ka] [ka] [ka] [ka] [ka]

[0058] The compound represented by the above general formula (1) can be synthesized using a halogen compound containing iodine, bromine, chlorine, and fluorine, and hexahydropyrimidopyrimidine as starting materials, as shown in the reaction formula (4) below, by a Ullmann coupling reaction, a Buchwald-Hartwig amination reaction, or a nucleophilic substitution reaction. [ka]

[0059] Furthermore, it is preferable that the organic material layer 12 includes a compound having a structure represented by the following general formula (2) as an organic material capable of coordination bonding.

[0060] [ka] (In general formula (2), X1 , X 2 represents a nitrogen atom, oxygen atom, sulfur atom, or divalent linking group, which may have substituents, either identical or different. L represents a direct bond or a p-valent linking group. 2 'p' represents a number that is either 0 or 1, and 'p' represents a number from 1 to 4. 'q' represents a number that is either 0 or 1, and when 'p' is 1, 'q' is 0. R 2 ~R 4 m represents a monovalent substituent that is identical or different. 1 ~m 3 These represent numbers from 0 to 3, which are either the same or different. 2 ~R 4 X 1 , X 2 It may bond with R to form a ring structure. 2 If there are multiple R 2 They may be bonded together to form a ring structure. Also, R 3 If there are multiple R 3 They may be bonded together to form a ring structure. Also, R 4 If there are multiple R 4 They may be bonded together to form a ring structure.

[0061] X in the above general formula (2) 1 , X 2 This represents a nitrogen atom, oxygen atom, sulfur atom, or divalent linking group, which may have substituents, and are identical or different. Examples of divalent linking groups include divalent hydrocarbon groups and groups in which some of the carbon atoms of a hydrocarbon group are replaced by heteroatoms of nitrogen, oxygen, or sulfur. The hydrocarbon group is preferably one having 1 to 6 carbon atoms, and more preferably one having 1, 2, or 6 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination of these. The divalent hydrocarbon group may be an alkylene group, which is a saturated hydrocarbon group, or an unsaturated hydrocarbon group such as an alkenylene group or an alkylylene group. Specifically, divalent hydrocarbon groups represented by the following formulas (5-1) to (5-4) are preferred. In the following formulas (5-1) to (5-4), R represents a substituent. Including R in the following formulas (5-1) to (5-4), X 1 , X 2 Specific examples of substituents in this context include R, which will be discussed later. 2 ~R 4 Examples of monovalent substituents include groups similar to those shown.

[0062] [ka]

[0063] In the general formula (2) above, L represents either a direct bond or a p-valent linking group. Note that L is a direct bond only when p is 2. Examples of p-valent linking groups include nitrogen atoms, oxygen atoms, sulfur atoms, and carbon atoms, as well as groups formed by removing p hydrogen atoms from hydrocarbon groups or groups in which some of the carbon atoms of a hydrocarbon group are replaced by heteroatoms of nitrogen, oxygen, or sulfur atoms. When the p-valent linking group has a carbon atom, it is preferable that it has 1 to 30 carbon atoms. More preferably, it has 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination of these. The hydrocarbon group may be a saturated hydrocarbon group, an unsaturated hydrocarbon group, or an aromatic hydrocarbon group. Aromatic hydrocarbon groups include those formed by removing hydrogen atoms from aromatic compounds such as benzene rings, naphthalene rings, anthracene rings, tetracene rings, pentacene rings, triphenylene rings, pyrene rings, fluorene rings, and indene rings.

[0064] In the above general formula (2), R 2 ~R 4 represents a monovalent substituent that is identical or different. Also, m 1 ~m 3 These represent numbers from 0 to 3, which are either the same or different. Monovalent substituents include fluorine atoms; haloalkyl groups such as fluoromethyl, difluoromethyl, and trifluoromethyl groups; linear or branched alkyl groups with 1 to 20 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert-butyl groups; cyclic alkyl groups with 5 to 7 carbon atoms such as cyclopentyl, cyclohexyl, and cycloheptyl groups; methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentyloxy, hexyloxy, and heptyloxy groups. Linear or branched alkoxy groups with 1 to 20 carbon atoms, such as oxy groups and octyloxy groups; nitro groups; cyano groups; alkylamino groups with alkyl groups with 1 to 10 carbon atoms, such as methylamino groups, ethylamino groups, dimethylamino groups, and diethylamino groups; cyclic amino groups such as pyrrolidino groups, piperidino groups, and morpholino groups; diarylamino groups such as diphenylamino groups and carbazolyl groups; acyl groups such as acetyl groups, propionyl groups, and butyryl groups; alkenyl groups with 2 to 30 carbon atoms, such as styryl groups; halogen atoms such as fluorine atoms, and alkyl groups with 1 to 20 carbon atoms, alkoxy groups A C5-C20 aryl group (specific examples of aryl groups are the same as those for aromatic hydrocarbon groups above) which may be substituted with a C1 group, an amino group, etc.; a C4-C40 heterocyclic group containing one or more C1-C4 nitrogen, sulfur, or oxygen atoms which may be substituted with a halogen atom such as a fluorine atom, or a C1-C20 alkyl group, an alkoxy group, an amino group, etc. (The heterocyclic group may consist of only one ring, or may be a compound in which multiple compounds consisting of only one aromatic heterocyclic ring are directly bonded to each other by a single carbon atom, or may be a fused heterocyclic group. Specific examples of heterocyclic groups are as follows: This includes specific examples of aromatic heterocyclic groups such as thiophene rings, furan rings, pyrrole rings, benzothiophene rings, benzofuran rings, indole rings, dibenzothiophene rings, dibenzofuran rings, carbazole rings, thiazole rings, benzothiazole rings, oxazole rings, benzoxazole rings, imidazole rings, benzimidazole rings, pyridine rings, pyrimidine rings, pyrazine rings, pyridazine rings, triazine rings, quinoline rings, isoquinoline rings, quinoxaline rings, benzothiadiazole rings, and phenanthridine rings. Examples include ester groups and thioether groups.These groups may also be substituted with halogen atoms, heteroatoms, alkyl groups, aromatic rings, etc.

[0065] Furthermore, in the general formula (2) above, p represents a number from 1 to 4, but it is preferably a number from 1 to 3. Specific examples of compounds in which p in general formula (2) is 1 include, for example, the compounds represented by the following structural formulas (6-1) to (6-9). [ka]

[0066] n in the general formula (2) above 2 n represents a number of 0 or 1, but the compound represented by the above general formula (2) is n 2 One preferred embodiment of the present invention is a compound in which n of general formula (2) is 0. 2 Specific examples of compounds with a ratio of 0 include, for example, the compounds represented by the above structural formulas (6-1) to (6-6).

[0067] The compounds represented by the above general formula (2) include compounds having a structure represented by the following general formula (7) which has only one phenanthroline skeleton, and these compounds are also suitable as materials for the organic material layer 12.

[0068] [ka]

[0069] (In general formula (7), R 5 , R 6 These are identical or distinct, representing a dialkylamino group or an alkoxy group. 4 , m 5 R represents the number 1 or 2, which is either the same or different. 5 If there are multiple R 5 They may bond to form a ring structure. Also, R 6 If there are multiple R 6 They may combine to form a ring structure.

[0070] R in the above general (7) 5 , R 6 These represent a dialkylamino group or an alkoxy group, either identical or distinct. The dialkylamino group is preferably one having an alkyl group with 1 to 20 carbon atoms, such as a methyl group or an ethyl group. More preferably, it is a dialkylamino group having an alkyl group with 1 to 10 carbon atoms. The two alkyl groups of the dialkylamino group may have the same number of carbon atoms or different numbers of carbon atoms. Also preferred are amino groups formed by linking two alkyl groups, such as cyclic amino groups like a piperidino group, a pyrrolidino group, or a morpholino group. As an alkoxy group, R in the above general formula (2) is 2 ~R 4 Examples include those similar to those where the group is an alkoxy group.

[0071] In addition to compounds having only one phenanthroline skeleton, compounds having multiple phenanthroline skeletons, as shown in the following structural formulas (8-1) to (8-4), are also considered suitable. [ka]

[0072] Furthermore, compounds represented by the following structural formulas (9-1) to (9-56), which are included in the above general formula (2) and have a structure similar to the above, are also suitable. [ka] [ka] [ka] [ka] [ka]

[0073] Furthermore, the material for the organic material layer 12 is preferably an organic material having nitrogen atoms capable of coordination bonding, and various compounds having the structure represented by the following formulas (9-57) to (9-59) as a skeletal structure can also be used. These compounds include not only compounds with the structure represented by the following formulas (9-57) to (9-59), but also compounds having substituents on the structure represented by the following formulas (9-57) to (9-59). Substituents include R in the general formula (2) described above. 2 ~R 4 Similar examples include those with one substituent or multiple substituents. If there are multiple substituents, they may bond to each other to form a ring structure. [ka]

[0074] In addition, the organic material used in the organic material layer 12 only needs to be able to be used as a ligand (i.e., it just needs to be capable of coordinating bonds). Therefore, the organic material used in the organic material layer 12 can include not only nitrogen atoms, but also acetylacetonate derivatives in which oxygen atoms act as coordinating elements.

[0075] The organic material layer 12 only needs to contain one type of organic material that has coordinating ability, and may also be a mixed film of two or more types of organic materials or a mixed film with organic materials that do not have coordinating ability.

[0076] The average thickness of the organic material layer 12 is preferably 0.5 to 10 nm, more preferably 1 to 5 nm, and most preferably 1 to 5 nm. The average thickness of the organic material layer 12 can be measured, for example, by a stylus step meter or spectroscopic ellipsometry.

[0077] "Metal layer" The metal layer 13 contains metal elements. Since the metal layer 13 is composed of metal elements that act as the central metal in a metal complex when the organic material layer 12 is used as a ligand, it can function as a thin film. For bottom-emission types, transparency is required, so its thickness is preferably 0.1 to 5 nm, and more preferably 0.5 to 2 nm. For top-emission types, transparency is not required, and there are no thickness restrictions. The average thickness of the metal layer 13 can be measured by a stylus step meter or spectroscopic ellipsometry.

[0078] The metal layer 13 can be any metal that has coordinating ability, and may be a single metal layer, a layer made by laminating one or both of the following: a layer made by mixing two or more metals and a layer made by a single metal, or a layer made by mixing two or more metals. The metallic elements that form the metallic layer 13 are not particularly limited, but include copper, nickel, palladium, platinum, gold, cobalt, zinc, aluminum, silver, chromium, manganese, iron, tin, indium, titanium, zirconium, vanadium, niobium, tantalum, molybdenum, tungsten, indium, gallium, cadmium, lithium, cesium, ytterbium, etc. The metal elements of organometallic complexes such as metal phthalocyanines, which have been reported, are thought to trigger the coordination reaction of the present invention and are suitable as metal elements for forming the metal layer 13.

[0079] If the metal layer 13 includes a layer made up of two or more metal elements, it is preferable that at least one of the metal elements constituting the metal is made up of aluminum, silver, zinc, or gold. If the metal layer 13 is a layer made of an elemental metal, it is preferable that the layer is made of a metal selected from the group consisting of aluminum, silver, zinc, and gold.

[0080] "Hole injection auxiliary layer" The hole injection auxiliary layer 14 can be formed as needed and is not necessarily required. The second hole injection auxiliary layer 14 can use a conventional hole injection material as described below, and good hole injection performance can be obtained by using it in combination with the lamination of the organic material layer 12 and the metal layer 13 described above. The hole injection auxiliary layer 14 may be made of an inorganic material or an organic material. Since inorganic materials are more stable than organic materials, it is easier to obtain higher resistance to oxygen and water compared to when organic materials are used. The inorganic material is not particularly limited, but for example, one or more metal oxides such as vanadium oxide (V2O5), molybdenum oxide (MoO3), and ruthenium oxide (RuO2) can be used. Organic materials that can be used include dipyradino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonnitrile (HAT-CN), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), and fullerenes.

[0081] The average thickness of the hole injection auxiliary layer 14 is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 1 to 50 nm. The average thickness of the hole injection auxiliary layer 14 can be measured during film formation using a quartz crystal thickness meter or a stylus-type step meter.

[0082] "Sealing" The organic EL element 1 shown in Figures 1 and 2 may be sealed if necessary. For example, the organic EL element 1 shown in Figures 1 and 2 may be sealed by a sealing container (not shown) having a concave space for housing the organic EL element 1, and by an adhesive that bonds the edge of the sealing container to the substrate 2. Alternatively, the organic EL element 1 may be housed in the sealing container and then sealed by filling it with a sealing material made of ultraviolet (UV) curing resin or the like. Furthermore, for example, the organic EL element 1 shown in Figures 1 and 2 may be sealed using a sealing member consisting of a plate member (not shown) placed on the cathode 6 and a frame member (not shown) placed along the edge of the plate member facing the cathode 6, and an adhesive that bonds the space between the plate member and the frame member and the space between the frame member and the substrate 2.

[0083] When sealing the organic EL element 1 using a sealing container or sealing member, a desiccant that absorbs moisture may be placed inside the sealing container or on the inside of the sealing member. Alternatively, a material that absorbs moisture may be used as the sealing container or sealing member. Furthermore, a space may be formed inside the sealed sealing container or on the inside of the sealing member.

[0084] When sealing the organic EL element 1 shown in Figures 1 and 2, resin materials, glass materials, etc., can be used as the material for the sealing container or sealing member. Examples of resin materials and glass materials used for the sealing container or sealing member are the same as those used for the substrate 2.

[0085] "Manufacturing method for organic EL elements" Next, as an example of a method for manufacturing an organic EL element of the present invention, a method for manufacturing the organic EL element 1 with the forward structure shown in Figure 2 will be described, but a reverse structure is also acceptable. In that case, for example, it is sufficient to simply stack the elements so that the cathode and electron injection layer are reversed, and there are no particular limitations on the film deposition method.

[0086] To manufacture the organic EL element 1 shown in Figure 2, first, an anode 3 is formed on the substrate 2. Anode 3 can be formed by sputtering, vacuum deposition, sol-gel method, spray pyrolysis (SPD), atomic layer deposition (ALD), vapor deposition, liquid deposition, etc. A method of joining metal foils may also be used to form anode 3.

[0087] Next, a hole injection layer 7, a hole transport layer 8, a light-emitting layer 9, an electron transport layer 10, an organic material layer 12, a metal layer 13, a hole injection auxiliary layer 14, a hole transport layer 8, a light-emitting layer 9, an electron transport layer 10, an electron injection layer 11, and a cathode 6 are formed on the anode 3 in this order. Here, the organic material layer 12 is formed using the above-mentioned organic material capable of coordination bonding. The metal layer 13 is formed using the above-mentioned metal element.

[0088] The method for forming the hole injection layer 7, hole transport layer 8, light-emitting layer 9, electron transport layer 10, organic material layer 12, metal layer 13, hole injection auxiliary layer 14, hole transport layer 8, light-emitting layer 9, electron transport layer 10, electron injection layer 11, and cathode 6 is not particularly limited, and various conventionally known formation methods can be used as appropriate in accordance with the characteristics of the materials used for each layer. As methods for forming each layer, chemical vapor deposition (CVD) methods such as plasma CVD, thermal CVD, and laser CVD, dry plating methods such as vacuum deposition, sputtering, and ion plating, thermal spraying, and wet plating methods such as electrolytic plating, immersion plating, and electroless plating, as well as printing technologies such as sol-gel method, MOD method, spray pyrolysis method, doctor blade method using fine particle dispersion, spin coating method, inkjet method, and screen printing method can be used. These methods are preferably selected according to the characteristics of the material of each layer, and the manufacturing method may differ for each layer. Through the above process, the organic EL element 1 shown in Figure 2 is obtained.

[0089] "Sealing method" When encapsulating the organic EL element 1 shown in Figures 1 and 2, it can be encapsulated using a standard method used for encapsulating organic EL elements.

[0090] <Display device, lighting device> The organic EL element of the present invention can change the emission color by appropriately selecting materials such as the light-emitting layer, and a desired emission color can also be obtained by using a color filter or the like in combination. Therefore, the organic EL element of the present invention can be suitably used as a light-emitting part of a display device or as an illumination device.

[0091] The display device of the present invention has a charge generation unit including an organic material layer and a metal layer between each light-emitting unit (including the light-emitting layer), and comprises an organic EL element of the present invention that is highly productive and has a low driving voltage. For this reason, it is a desirable display device.

[0092] Furthermore, the lighting device of the present invention incorporates the organic EL element of the present invention, which offers excellent productivity and low driving voltage. For this reason, it is a desirable lighting device. [Examples]

[0093] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "moles%".

[0094] (Synthesis Example 1) The compound represented by the structural formula (3-2) below was synthesized by the method described below. [ka]

[0095] In a 200 mL three-necked flask, rac-BINAP (747 mg) and toluene (67 mL) were placed and heated to 90°C under a nitrogen atmosphere to dissolve. After cooling to room temperature, palladium acetate (180 mg) was added and the mixture was stirred at room temperature for 1 hour. 2,6-dibromopyridine (4.74 g), 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (6.13 g), and KOtBu (6.28 g) were added and the mixture was heated and stirred overnight at 90°C. After cooling to room temperature, diethyl ether was added, the precipitated solid was filtered off, and the filtrate was concentrated. Acetone was added to the resulting residue, and the precipitated solid was filtered off to obtain the compound represented by structural formula (3-2) (3.7 g, 52.5%).

[0096] (Synthesis Example 2) The compound represented by the following structural formula (9-5) was synthesized by the method described below. [ka]

[0097] A mixture of 4,7-dichloro-1,10-phenanthroline (3.00 g) and pyrrolidine (19.5 mL) in a 100 mL eggplant flask was heated under reflux in an oil bath at 100°C for 1 hour. The mixture was allowed to return to room temperature, concentrated under reduced pressure, water was added, and the precipitated solid was collected by sonication. The obtained solid was dried under reduced pressure and dissolved in methanol (100 mL). Activated carbon was added to the mixture and stirred at room temperature for 1 hour, after which insoluble matter was filtered off. The filtrate was concentrated under reduced pressure, and the obtained solid was recrystallized with methanol (9 mL). The obtained solid was washed with a small amount of methanol and dried under reduced pressure to obtain the compound represented by structural formula (9-5) (1.69 g, 44%) as a white solid.

[0098] (Example 1) The organic EL element 1 shown in Figure 2 was manufactured and evaluated using the method described below.

[0099] [Process 1] As substrate 2, a commercially available transparent glass substrate with an average thickness of 0.7 mm was prepared, which had an electrode (anode 3) made of 100 nm thick ITO patterned to a width of 3 mm. Then, the substrate 2 having anode 3 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and then boiled in isopropanol for 5 minutes. After that, the substrate 2 having anode 3 was removed from the isopropanol, dried by nitrogen blowing, and then UV ozone cleaning was performed for 20 minutes.

[0100] [Process 2] In [Step 1], the substrate 2 on which the cleaned anode 3 is formed is introduced into the vacuum apparatus, and the inside of the vacuum deposition apparatus chamber is 1 × 10 -5 The pressure was reduced to Pa, and a 1 nm layer of the compound with structural formula (3-2) was formed by vacuum deposition using resistance heating. Subsequently, a 2 nm layer of aluminum was formed to create the hole injection layer 7.

[0101] [Process 3] Next, as the hole transport layer 8, N-([1,1'-biphenyl]-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-fluoren-2-amine (HT-01), shown in the following structural formula (10), was co-deposited at 60 nm. Subsequently, using HT-01 and 2,4-diphenyl-6-bis(12-phenylindoro)[2,3-a]carbazole-11-yl)-1,3,5-triazine (DIC-TRZ), shown in the following structural formula (11), fac-tris(3-methyl-2-phenylpyridinato-N,C2'-)iridium(III) (Ir(mppy)3), shown in the following structural formula (12), was co-deposited at 30 nm to form the light-emitting layer 9. At this time, the mass ratio of HT-01 and DIC-TRZ was set to 3:7, and the doping concentration of the dopant Ir(mppy)3 was set to 5% by mass relative to the entire luminescent layer 9. Subsequently, a 40nm film of DIC-TRZ was deposited as the electron transport layer 10.

[0102] [Step 4] After forming the electron transport layer 10, a 1 nm layer of the compound represented by the above structural formula (3-2) was formed as an organic material layer 12 by vacuum deposition.

[0103] [Step 5] Next, a 2 nm layer of aluminum was formed as a metal layer 13 using a vacuum deposition method.

[0104] [Step 6] Next, dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonnitrile (HAT-CN), represented by the following structural formula (13), was formed as a hole injection auxiliary layer 14 by 5 nm vacuum deposition.

[0105] [Step 7] Next, as the hole transport layer 8, N-([1,1'-biphenyl]-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-fluoren-2-amine (HT-01), shown in the following structural formula (10), was co-deposited at 60 nm. Subsequently, using HT-01 and 2,4-diphenyl-6-bis(12-phenylindoro)[2,3-a]carbazole-11-yl)-1,3,5-triazine (DIC-TRZ), shown in the following structural formula (11), fac-tris(3-methyl-2-phenylpyridinato-N,C2'-)iridium(III) (Ir(mppy)3), shown in the following structural formula (12), was co-deposited at 30 nm to form the light-emitting layer 9. At this time, the mass ratio of HT-01 and DIC-TRZ was set to 3:7, and the doping concentration of the dopant Ir(mppy)3 was set to 5% by mass relative to the entire luminescent layer 9. Subsequently, a 40nm film of DIC-TRZ was deposited as the electron transport layer 10.

[0106] [Step 8] A mixed film of the compound represented by the above structural formula (3-2) and the compound represented by the following structural formula (14) was deposited at a mass ratio of 4:6 by co-evaporation to form a 5 nm film, thereby creating an electron injection layer 11.

[0107] [Step 9] Next, a cathode 6 made of aluminum with a thickness of 100 nm was deposited on the substrate 2, which had the electron injection layer 11 formed on it, by vacuum deposition. Furthermore, the cathode 6 was formed using a stainless steel deposition mask so that the deposition surface was in the shape of a 3 mm wide strip, and the light-emitting area of ​​the fabricated organic EL element was 9 mm². 2 That's what I decided.

[0108] [Step 10] Next, the substrate 2, on which each layer up to the cathode 6 was formed, was placed in a glass cap (sealing container) having a concave space, and sealed by filling it with a sealing material made of ultraviolet (UV) curing resin to obtain the organic EL element of Example 1.

[0109] (Example 2) An organic EL element of Example 2 was obtained in the same manner as in Example 1, except that [Step 4] of Example 1 was replaced with [Step 4-1] below.

[0110] [Step 4-1] After forming the electron transport layer 10, a mixed film of the compound represented by the above structural formula (3-2) and the compound represented by the following structural formula (14) was co-deposited at a mass ratio of 4:6 by vacuum deposition to form an organic material layer 12 with a thickness of 5 nm.

[0111] (Example 3) An organic EL element of Example 3 was obtained in the same manner as in Example 1, except that in [Step 4] of Example 1, the compound of structural formula (9-5) was used as the organic material layer 12 instead of the compound of structural formula (3-2).

[0112] (Comparative Example 1) The organic EL element of Comparative Example 1 was obtained in the same manner as in Example 1, except that in [Step 4] of Example 1, 8-quinolinolatritium (Liq) shown in the following structural formula (15) was used as the organic material layer 12 instead of the compound of structural formula (3-2).

[0113] [ka]

[0114] (Measurement of brightness voltage characteristics of organic EL elements) For the organic EL elements fabricated in Examples 1-3 and Comparative Example 1, a voltage was applied using a Keithley "2400 type source meter," and the brightness was measured using a Konica Minolta "LS-100" to investigate the relationship between applied voltage and brightness. The results are shown in Figure 3.

[0115] As shown in Figure 3, Examples 1 to 3, in which the organic material having coordinating moieties of the present invention is used in the organic material layer 12 and laminated with the metal layer 13, are driven at a lower voltage than Comparative Example 1, in which the organic material layer 12 uses Liq containing an alkali metal, which is a conventional material. From these results, it is clear that the effects of the present invention are evident, as a coordination reaction occurs when the organic material layer 12 containing the organic material having coordinating moieties and the metal layer 13 are laminated together, resulting in excellent electron injection from the charge generation unit to the anode-side light-emitting unit and excellent hole injection to the cathode-side light-emitting unit. Furthermore, since both Example 1 and Example 2 were driven at similarly low voltages, it can be seen that either a single layer or a mixed layer is acceptable as long as it contains an organic material having a site capable of coordinating with the organic material layer 12. Also, since Example 3 was driven at a significantly lower voltage than Comparative Example 1, similar to Examples 1 and 2, it can be seen that the effects of the present invention can be obtained not only with hexahydropyrimidopyrimidine compounds but also with phenanthroline compounds, indicating that similar effects can be obtained with any organic material capable of coordination bonding.

[0116] (Measurement of lifespan characteristics of organic EL elements) For the organic EL elements fabricated in Examples 1-3 and Comparative Example 1, the relationship between the elapsed time since the start of operation at a constant current and the relative brightness was investigated using an "Organic EL Lifetime Measurement Device" manufactured by EHC Corporation. Specifically, the voltage was automatically adjusted so that a constant current flowed through the organic EL element, and the relative brightness with respect to the elapsed time since the start of operation at a constant current was measured (using a luminance meter (LS-110) manufactured by Konica Minolta Corporation). The current value was calculated assuming a brightness of 10,000 cd / m² at the start of measurement. 2 The settings were adjusted for each organic EL element to achieve the desired result. The results are shown in Figure 4.

[0117] Figure 4 is a graph showing the relationship between the elapsed time since the start of operation at a constant current and the brightness, as measured using an organic EL lifetime measurement device. As shown in Figure 4, the brightness decreases with elapsed time in all organic EL elements of Examples 1-3 and Comparative Example 1. However, the decrease in brightness is suppressed in Examples 1-3 compared to Comparative Example 1. For example, at an elapsed time of 1 hour, Comparative Example 1 had a brightness of 3500 cd / m².2 The brightness has decreased to some extent. In contrast, in Example 1, the brightness was 100 cd / m². 2 For example, in Example 2, the density was 95 cd / m². 2 For example, in Example 3, the density was 120 cd / m². 2 It has only decreased to a certain extent. These results indicate that the tandem-structured organic EL element of the present invention exhibits minimal brightness degradation during continuous operation and has a long lifespan. This is thought to be due to the good luminescence characteristics and the absence of degradation caused by alkali metal diffusion in the tandem-structured organic EL element of the present invention. [Explanation of Symbols]

[0118] 1: Organic EL element, 2: Substrate, 3: Anode, 4-1, 4-2, 4-n: Light-emitting unit, 5-1, 5-2, 5-(n-1): Charge generation unit, 6: Cathode, 7: Hole injection layer, 8: Hole transport layer, 9: Light-emitting layer, 10: Electron transport layer, 11: Electron injection layer, 12: Organic material layer, 13: Metal layer, 14: Hole injection auxiliary layer

Claims

1. An organic electroluminescent element comprising an anode, a cathode, a plurality of light-emitting units located between the anode and the cathode, and a charge-generating unit located between each light-emitting unit, The light-emitting unit has a light-emitting layer, The charge generation unit has, in order from the anode side, an organic material layer and a metal layer. The aforementioned organic material layer contains a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1) as a coordinating organic material, An organic electroluminescent element characterized in that the metal layer contains a metal element. 【Chemistry 1】 (In general formula (1), R １ n represents an aromatic hydrocarbon group which may have substituents, an aromatic heterocyclic group, an arylalkylene group, a 2- to 4-valent linear or cyclic hydrocarbon group, or a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. １ (This is an integer between 1 and 4.)

2. The organic electroluminescent element according to claim 1, wherein the metal layer is made of aluminum.

3. The organic electroluminescent element according to claim 1 or 2, wherein the thickness of the metal layer is 5 nm or less.

4. n in the general formula (1) １ The organic electroluminescent element according to claim 1, wherein the element is 2 or 3.

5. A display device comprising an organic electroluminescent element according to any one of Claims 1 to 4.

6. A lighting device characterized by comprising an organic electroluminescent element according to any one of claims 1 to 4.

7. It comprises an anode, a cathode, a plurality of light-emitting units located between the anode and the cathode, and a charge-generating unit located between each light-emitting unit, The light-emitting unit has a light-emitting layer, The method for manufacturing an organic electroluminescent element, wherein the charge generation unit comprises, in order from the anode side, an organic material layer and a metal layer, The process involves forming the organic material layer using a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1) as a coordinating organic material, A step of forming the metal layer using a metal element, A method for producing an organic electroluminescent element, characterized by containing the following: 【Chemistry 2】 (In general formula (1), R １ n represents an aromatic hydrocarbon group which may have substituents, an aromatic heterocyclic group, an arylalkylene group, a 2- to 4-valent linear or cyclic hydrocarbon group, or a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. １ (This is an integer between 1 and 4.)

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