Organic electroluminescent element, display device, and illumination device

Abstract

To provide an organic electroluminescent element with excellent light-emitting characteristic and atmospheric stability, and a display device and an illumination device having such an organic electroluminescent element.SOLUTION: An organic electroluminescent element 1 includes a substrate 2, a cathode 3, an electron injection layer 4, a light-emitting layer 6, and an anode 9 in this order. The electron injection layer 4 includes an organic material in which a work function of a surface is 0.0 to 4.0 eV, and a metal complex. A display device and an illumination device include this organic electroluminescent element 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Organic EL elements can be fabricated on thin, flexible substrates, and are therefore expected to have a wide range of applications. In particular, displays using organic EL elements have higher contrast and a wider viewing angle than liquid crystal displays, and so their use in large-screen televisions and mobile devices is expanding. Organic EL elements are also expected to be used as lighting devices.

[0003] It is generally known that organic EL elements deteriorate due to moisture in the air. Therefore, in display devices and lighting devices that use organic EL elements, it is necessary to strictly seal the organic EL elements by bonding them with glass that is difficult for moisture to penetrate.

[0004] On the other hand, flexible substrates such as plastic films are prone to moisture permeation because sealing with glass is difficult, as described in Non-Patent Document 1 below. As a result, moisture may reach the organic EL element, causing the element to deteriorate. In particular, parts of the organic EL element that have been deteriorated by water molecules in the air become non-emitting regions, and these non-emitting regions expand over time near the edges of the element and near minute foreign particles on the substrate. As shown in Non-Patent Document 2 below, such deterioration is called shrink and dark spots, respectively, and when it occurs, it can cause serious image quality problems.

[0005] Furthermore, in organic EL elements having a typical conventional structure, metal complexes such as alkali metal compounds are widely used as materials capable of reducing the barrier for electron injection from the cathode. However, these metal complexes are known to be highly reactive to water molecules in the air, and are therefore considered to be unsuitable as materials for organic EL elements that are stable in the air.

[0006] In response to this, Non-Patent Document 3 below reports that the stability of an organic EL element in the atmosphere can be improved by adopting a so-called inverted structure in which the electrode layer structure is reversed from that of an organic EL element having a normal structure, and by using an organic material in the electron injection layer that can reduce the work function of the electrode surface without using a metal complex such as an alkali metal compound. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] MSWeaver et al., “Organic light-emitting devices with extended operating lifetimes on plastic substrates”, Applied Physics Letters, vol. 81, 2929 (2002). [Non-Patent Document 2] T. Okada, A. Yoshida, and T. Tsuji, “Dark spot growth and its acceleration factor in organic light-emitting diodes with single barrier structure”, Japanese Journal of Applied Physics, 56, 060305 (2017). [Non-Patent Document 3] H. Fukagawa et al., “Highly efficient and air-stable inverted organic light-emitting diode composed of inert materials”, Applied Physics Express, vol.7, No.8, (2014). Summary of the Invention [Problem to be solved by the invention]

[0008] As mentioned above, studies have been conducted to improve the atmospheric stability by using an organic material that can reduce the work function of the electrode surface without using a metal complex such as an alkali metal compound in the electron injection layer in an inverted structure organic EL element, but this is not sufficient and further improvement in the atmospheric stability is necessary. In particular, further improvement in the atmospheric stability is essential to realize display devices and lighting devices with simple sealing.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic EL element having better light emitting characteristics and atmospheric stability than conventional organic EL elements. Another object of the present invention is to provide a display device and a lighting device that include such an organic EL element. [Means for solving the problem]

[0010] The inventors have conducted extensive investigations into the layer configuration of an inverted-structure element in which the electrode stacking structure is reversed from that of an organic EL element of a normal structure, and have found that even an element using a metal complex such as an alkali metal compound has a layer configuration that is resistant to deterioration. In particular, they have found that in an organic EL element having a cathode, an electron injection layer, a light-emitting layer, and an anode, in this order, on a substrate, the above-mentioned problems can be successfully solved by using, in the electron injection layer, an organic material that can reduce the work function of the electrode and a metal complex, and have arrived at the present invention. That is, the essential configurations of the organic electroluminescence element, the display device, and the lighting device of the present invention that solve the above problems are as follows.

[0011] [1] A device comprising, in this order, a substrate, a cathode, an electron injection layer, a light emitting layer, and an anode; The organic electroluminescence device, wherein the electron injection layer contains an organic material having a surface work function of 0.0 to 4.0 eV and a metal complex. The organic electroluminescence device of the present invention described in [1] above has superior light-emitting properties and atmospheric stability to conventional organic EL devices. Here, the term "organic material having a surface work function of 0.0 to 4.0 eV" refers to an organic material having a surface work function of 0.0 to 4.0 eV when formed into a film.

[0012] [2] The organic material is represented by the following general formula (1): [ka] (In general formula (1), R 1 represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent linear or cyclic hydrocarbon group, which may have a substituent, 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 is an integer of 1 to 4.) and a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (2): [ka] (In general formula (2), X 1 , X 2 are the same or different and each represents a nitrogen atom, an oxygen atom, a sulfur atom, or a divalent linking group which may have a substituent. L represents a direct bond or a p-valent linking group. 2 represents a number of 0 or 1, and p represents a number of 1 to 4. q represents a number of 0 or 1, and when p is 1, q is 0. R 2 ~R 4 m may be the same or different and represents a monovalent substituent. 1 ~m 3 R may be the same or different and represents a number from 0 to 3. 2 ~R 4 X 1 , X 2 may be bonded to form a ring structure, R 2 If there are multiple R 2 may be bonded to form a ring structure. 3 If there are multiple R 3 may be bonded to form a ring structure. 4 If there are multiple R 4may be bonded to form a ring structure. The organic electroluminescence element described in [2] above has further improved light emitting characteristics and atmospheric stability.

[0013] [3] The organic material is represented by the following general formula (3): [ka] (In general formula (3), R 5 , R 6 are the same or different and each represents a dialkylamino group or an alkoxy group. 4 , m 5 are the same or different and represent the number 1 or 2. 5 If there are multiple R 5 may be bonded to form a ring structure. 6 If there are multiple R 6 may be bonded to form a ring structure. 5 , R 6 The organic electroluminescence device according to [1] or [2], wherein the dialkylamino group is a phenanthroline compound having a structure represented by the following formula: The organic electroluminescence element described in [3] above has further improved light emitting characteristics and atmospheric stability.

[0014] [4] The organic electroluminescence device according to any one of [1] to [3], wherein the metal complex is an alkali metal complex. The organic electroluminescence element described in [4] above has further improved luminous characteristics and atmospheric stability.

[0015] [5] The organic electroluminescence device according to any one of [1] to [4], wherein the metal complex is a lithium complex. The organic electroluminescence element described in [5] above has further improved light emitting characteristics and atmospheric stability.

[0016] [6] The organic electroluminescence device according to any one of [1] to [5], wherein the electron injection layer is made of a single layer containing the organic material and the metal complex. The organic electroluminescence element described in [6] above has further improved luminescence characteristics and atmospheric stability.

[0017] [7] The electron injection layer is formed by stacking a layer containing the organic material and a layer containing the metal complex, The organic electroluminescence element according to any one of [1] to [5], comprising, in order from the cathode side, a layer containing the organic material and a layer containing the metal complex. The organic electroluminescence element described in [7] above has further improved luminous characteristics and atmospheric stability.

[0018] [8] The electron injection layer is formed by stacking a layer containing the organic material and a layer containing the metal complex, The organic electroluminescence element according to any one of [1] to [5], comprising, in order from the cathode side, a layer containing the metal complex and a layer containing the organic material. The organic electroluminescence element described in [8] above has further improved luminescence characteristics and atmospheric stability.

[0019] [9] A display device comprising the organic electroluminescence element according to any one of [1] to [8]. The display device of the present invention described in [9] above emits light at a low applied voltage and has high atmospheric stability.

[0020]

[10] A lighting device comprising the organic electroluminescence element according to any one of [1] to [8]. The lighting device of the present invention described in

[10] above emits light at a low applied voltage and has high atmospheric stability. Effect of the Invention

[0021] According to the present invention, it is possible to provide an organic EL element having superior light emitting characteristics and atmospheric stability to conventional organic EL elements. Furthermore, according to the present invention, it is possible to provide a display device and a lighting device that include such an organic EL element. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram showing an example of the structure of an organic EL element of the present invention. [Diagram 2] 1 is a graph showing the results of measuring the luminance-voltage characteristics of various organic EL elements produced in the examples and comparative examples. [Diagram 3] 1 shows images of the light-emitting surfaces of various organic EL elements produced in Examples and Comparative Examples at the start of measurement. [Figure 4] 1 shows images of the light-emitting surfaces of various organic EL elements produced in Examples and Comparative Examples after 100 hours. [Diagram 5] 1 is a graph showing the results of measuring the change over time in the deterioration width from the end of the light-emitting surface of various organic EL elements produced in Examples and Comparative Examples. [Figure 6] 1 is a graph showing the results of measuring humidity changes during measurement of degradation of the light-emitting surface of various organic EL elements manufactured in Examples and Comparative Examples. [Figure 7] 1 is a graph showing the relationship between the voltage value at 1000 cd / m2 and the shrink coefficient of various organic EL elements produced in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the organic electroluminescence element, the display device, and the lighting device of the present invention will be described in detail with reference to their embodiments.

[0024] <Organic electroluminescence element> The organic electroluminescent element of the present embodiment includes a substrate, a cathode, an electron injection layer, a light emitting layer, and an anode, in this order. The electron injection layer of the organic electroluminescent element of the present embodiment is characterized in that it contains an organic material having a surface work function of 0.0 to 4.0 eV and a metal complex.

[0025] When the organic material having a work function of 0.0 to 4.0 eV and the metal complex are used alone in the electron injection layer, there are problems in that the stability in the atmosphere is deteriorated and the driving voltage is increased, resulting in a deterioration in the light-emitting properties. In contrast, in the organic EL element of the present embodiment, both the atmospheric stability and the luminescence characteristics can be improved by using an organic material having a surface work function of 0.0 to 4.0 eV in combination with a metal complex in the electron injection layer. Although the reason is not necessarily clear, by using an organic material having a surface work function of 0.0 to 4.0 eV in the electron injection layer, the work function of the cathode surface is reduced, and the electron injection barrier from the cathode is reduced, so that the driving voltage is lowered and the luminescence characteristics are improved, while the metal complex has better atmospheric stability than an organic material having a surface work function of 0.0 to 4.0 eV, and it is considered that the atmospheric stability is improved by combining the metal complex with an organic material having a surface work function of 0.0 to 4.0 eV.

[0026] Next, one embodiment of the organic EL element of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic diagram showing an example of the structure of the organic EL element of the present invention. The organic EL element 1 shown in Fig. 1 has a laminated structure in which a cathode 3, an electron injection layer 4, an electron transport layer 5, a light-emitting layer 6, a hole transport layer 7, a hole injection layer 8, and an anode 9 are formed in this order on a substrate 2.

[0027] "substrate" The material of the substrate 2 may be a resin material, a glass material, or the like. Examples of the resin material used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, polyarylate, etc. When a resin material is used as the material for the substrate 2, it is preferable because an organic EL element 1 having excellent flexibility can be obtained. Examples of glass materials used for the substrate 2 include quartz glass and soda glass.

[0028] When the organic EL element 1 is of a bottom emission type, the material of the substrate 2 is a transparent substrate. When the organic EL element 1 is of a top emission type, not only a transparent substrate but also an opaque substrate may be used as the material of the substrate 2. Examples of opaque substrates include a substrate made of a ceramic material such as alumina, a substrate in which an oxide film (insulating film) is formed on the surface of a metal plate such as stainless steel, and a substrate made of a resin material.

[0029] The average thickness of the substrate 2 can be determined depending on the material of the substrate 2, and is preferably 0.1 to 30 mm, and more preferably 0.1 to 10 mm. The average thickness of the substrate 2 can be measured with a digital multimeter and a vernier caliper.

[0030] "cathode" Although the cathode 3 shown in FIG. 1 is formed on and in direct contact with the substrate 2, the cathode 3 does not necessarily have to be formed on and in direct contact with the substrate 2. Examples of materials for the cathode 3 include conductive oxide materials such as ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), In2O3, SnO2, Sb-containing SnO2, and Al-containing ZnO. Among these, it is preferable to use ITO, IZO, or FTO as the material for the cathode 3. The average thickness of the cathode 3 is not particularly limited, but is preferably from 10 to 500 nm, and more preferably from 100 to 200 nm. The average thickness of the cathode 3 can be measured by a stylus step gauge or spectroscopic ellipsometry.

[0031] In the organic EL element of this embodiment, the layer made of an inorganic oxide formed on the cathode 3 is also treated as a part of the cathode. The oxide used in this case is a semiconductor or insulator laminated thin film layer. Specifically, it may be any of a layer made of a single metal oxide, a layer made of a mixture of two or more metal oxides and a layer made of a single metal oxide, or a layer made of a mixture of two or more metal oxides.

[0032] Metal elements constituting metal oxides that form inorganic oxides include magnesium, calcium, strontium, barium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, indium, gallium, iron, cobalt, nickel, copper, zinc, cadmium, aluminum, and silicon.

[0033] When the layer made of an inorganic oxide includes a layer containing a mixture of two or more kinds of metal oxides, it is preferable that at least one of the metal elements constituting the metal oxide is a layer made of magnesium, aluminum, calcium, zirconium, hafnium, silicon, titanium, or zinc. When the layer made of an inorganic oxide is a layer made of a simple metal oxide, it is preferable that the layer is made of a metal oxide selected from the group consisting of magnesium oxide, aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide, titanium oxide, and zinc oxide.

[0034] When the layer made of an inorganic oxide is a layer obtained by laminating either or both of a layer made of a mixture of two or more kinds of metal oxides and a layer made of a single metal oxide, or a layer obtained by mixing two or more kinds of metal oxides, examples of the layer made of an inorganic oxide include a layer made of a mixture of two kinds of metal oxides selected from titanium oxide / zinc oxide, titanium oxide / magnesium oxide, titanium oxide / zirconium oxide, titanium oxide / aluminum oxide, titanium oxide / hafnium oxide, titanium oxide / silicon oxide, zinc oxide / magnesium oxide, zinc oxide / zirconium oxide, zinc oxide / hafnium oxide, zinc oxide / silicon oxide, and calcium oxide / aluminum oxide, a layer made of a mixture of three kinds of metal oxides selected from titanium oxide / zinc oxide / magnesium oxide, titanium oxide / zinc oxide / zirconium oxide, titanium oxide / zinc oxide / aluminum oxide, titanium oxide / zinc oxide / hafnium oxide, titanium oxide / zinc oxide / silicon oxide, and indium oxide / gallium oxide / zinc oxide.

[0035] The inorganic oxide may include IGZO (indium gallium zinc oxide), which is an oxide semiconductor that exhibits favorable characteristics as a special composition, and / or 12CaO·7Al2O3, which is an electride. When an inorganic oxide film is formed, the average thickness is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 2 to 100 nm. The average thickness of the layer made of an inorganic oxide can be measured by a stylus step gauge or spectroscopic ellipsometry.

[0036] "Electron injection layer" The electron injection layer 4 contains an organic material with a low surface work function and a metal complex. Here, the electron injection layer 4 may be composed of (1) a single layer containing the organic material and the metal complex (i.e., a mixture of the organic material and the metal complex), or (2) a laminate of a layer containing the organic material and a layer containing the metal complex. Whether the electron injection layer 4 is composed of (1) a mixture or (2) a laminate, the luminescence characteristics and atmospheric stability can be improved. Furthermore, when the electron injection layer 4 is made of a laminated layer, one of the layers may be a mixed film of an organic material having a small surface work function and a metal complex.

[0037] Furthermore, when the electron injection layer 4 is formed by laminating a layer containing the organic material and a layer containing the metal complex, the arrangement of the layer containing the organic material and the layer containing the metal complex is not particularly limited, and may include (i) a layer containing the organic material and a layer containing the metal complex in this order from the cathode 3 side, or (ii) a layer containing the metal complex and a layer containing the organic material in this order from the cathode 3 side. Regardless of whether the electron injection layer 4 is arranged in (i) or (ii), the light-emitting properties and atmospheric stability can be improved.

[0038] - Organic materials with low surface work functions - The organic material has a surface work function of 0.0 to 4.0 eV, preferably 0.0 to 3.0 eV. When the surface work function of the organic material is 4.0 eV or less, the work function of the surface of the cathode 3 can be reduced, the driving voltage of the organic EL element 1 can be reduced, and the light-emitting characteristics can be improved. When the surface work function of the organic material is 3.0 eV or less, the work function of the surface of the cathode 3 can be further reduced, and the driving voltage of the organic EL element 1 can be further reduced, and the light-emitting characteristics can be further improved. In this specification, the work function of the organic material used in the electron injection layer 4 refers to the work function of the surface of the organic material when the organic material is formed on the electrode. The work function of the surface of the organic material when the organic material is formed on the electrode is measured by ultraviolet photoelectron spectroscopy (UPS). For the ultraviolet photoelectron spectroscopy, a measuring device (VersaProbe) manufactured by PHI is used, He I line (21.22 eV) is used as the ultraviolet light, and the Fermi level is based on gold.

[0039] The organic material having a small surface work function is preferably a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1) or a compound having a structure represented by the following general formula (2): By using the hexahydropyrimidopyrimidine compound of the following general formula (1) or the compound of the following general formula (2) as the organic material, the light emitting characteristics and atmospheric stability of the organic EL element 1 can be further improved.

[0040] [ka] (In general formula (1), R 1 represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent linear or cyclic hydrocarbon group, which may have a substituent, 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 is an integer from 1 to 4.

[0041] [ka] (In general formula (2), X 1 , X 2 are the same or different and each represents a nitrogen atom, an oxygen atom, a sulfur atom, or a divalent linking group which may have a substituent. L represents a direct bond or a p-valent linking group. 2 represents a number of 0 or 1, and p represents a number of 1 to 4. q represents a number of 0 or 1, and when p is 1, q is 0. R 2 ~R 4 m may be the same or different and represents a monovalent substituent. 1 ~m 3 R may be the same or different and represents a number from 0 to 3. 2 ~R 4 X 1 , X 2 may be bonded to form a ring structure, R 2 If there are multiple R 2 may be bonded to form a ring structure. 3 If there are multiple R 3may be bonded to form a ring structure. 4 If there are multiple R 4 may be bonded to form a ring structure.

[0042] R in the above general formula (1) 1 represents an aromatic hydrocarbon group which may have a substituent, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent chain or cyclic hydrocarbon group, 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 preferably have 3 to 30 carbon atoms, more preferably have 4 to 24 carbon atoms, and further preferably have 5 to 20 carbon atoms. Examples of aromatic hydrocarbon groups include compounds consisting of only one aromatic ring, such as benzene; compounds in which multiple aromatic rings, such as biphenyl and diphenylbenzene, are directly bonded to each other via one carbon atom; and groups formed by removing one to four hydrogen atoms from any of the aromatic rings of condensed ring aromatic hydrocarbon compounds, such as naphthalene, anthracene, phenanthrene, and pyrene. Examples of the aromatic heterocyclic group include compounds consisting of only one aromatic heterocycle, such as thiophene, furan, pyrrole, oxazole, oxadiazole, thiazole, thiadiazole, imidazole, pyridine, pyrimidine, pyrazine, and triazine; compounds in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded to each other via one carbon atom (such as bipyridine); and groups obtained by removing 1 to 4 hydrogen atoms from any of the aromatic heterocycles of condensed ring heteroaromatic hydrocarbon compounds, such as quinoline, quinoxaline, benzothiophene, benzothiazole, benzimidazole, benzoxazole, indole, carbazole, dibenzofuran, dibenzothiophene, acridine, and phenanthroline. The arylalkylene group includes a group formed by combining the above aromatic hydrocarbon group with an alkylene group having 1 to 3 carbon atoms. The divalent to tetravalent chain or cyclic hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably has 1 to 6 carbon atoms, and further preferably has 1 to 4 carbon atoms. The chain hydrocarbon group may be either linear or branched. Also, R 1 may be a group formed by combining two or more of the above-mentioned aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups. Furthermore, R 1 may be a group formed by combining one or more of the above aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups with a nitrogen atom. Examples of such groups include groups formed by removing 1 to 4 hydrogen atoms from trialkylamines such as trimethylamine or triphenylamine.

[0043] The aromatic hydrocarbon group, aromatic heterocyclic group, or arylalkylene group may have one or more monovalent substituents. Examples of the monovalent substituent include a fluorine atom; a haloalkyl group such as a fluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, or a cycloheptyl group; a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, or a methyloxy group. linear or branched alkoxy groups having 1 to 20 carbon atoms, such as a silyl group or an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms, such as a methylamino group, an ethylamino group, a dimethylamino group or a diethylamino group; a cyclic amino group, such as a pyrrolidino group, a piperidino group or a morpholino group; a diarylamino group, such as a diphenylamino group or a carbazolyl group; an acyl group, such as an acetyl group, a propionyl group or a butyryl group; an alkenyl group having 2 to 30 carbon atoms, such as a styryl group; a halogen atom, such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a cyclic amino group having 1 to 10 carbon atoms, such as ... an aryl group having 5 to 20 carbon atoms which may be substituted with a silyl group, an amino group, or the like (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group described above); a heterocyclic group containing one or more of a nitrogen atom, a sulfur atom, and an oxygen atom which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (the heterocyclic group may be one consisting of only one ring, or may be a compound in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded to each other at one carbon atom, or may be a condensed heterocyclic group. Specific examples of the heterocyclic group include Specific examples of aromatic heterocyclic groups include a thiophene ring, a furan ring, a pyrrole ring, a benzothiophene ring, a benzofuran ring, an indole ring, a dibenzothiophene ring, a dibenzofuran ring, a carbazole ring, a thiazole ring, a benzothiazole ring, an oxazole ring, a benzoxazole ring, an imidazole ring, a benzimidazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a benzothiadiazole ring, a phenanthridine ring, etc.); an ester group, a thioether group, etc.These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, or the like.

[0044] In the above general formula (1), n 1 is an integer of 1 to 4, preferably 2 or 3.

[0045] X in the above general formula (2) 1 , X 2 are the same or different and represent a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have a substituent. Examples of the divalent linking group include divalent hydrocarbon groups and groups in which some of the carbon atoms of a hydrocarbon group have been substituted with a heteroatom such as a nitrogen atom, an oxygen atom or a sulfur atom. The hydrocarbon group preferably has 1 to 6 carbon atoms, and more preferably has 1, 2 or 6 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination thereof. 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 alkynylene group.

[0046] In the above general formula (2), L represents a direct bond or a p-valent linking group. Note that L becomes a direct bond only when p is 2. Examples of the p-valent linking group include a nitrogen atom, an oxygen atom, a sulfur atom, a carbon atom, and also a group obtained by removing p hydrogen atoms from a hydrocarbon group or a group in which some of the carbon atoms of a hydrocarbon group have been substituted with a hetero atom such as a nitrogen atom, an oxygen atom, or a sulfur atom. When the p-valent linking group has a carbon atom, it preferably has 1 to 30 carbon atoms, and more preferably has 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination thereof. The hydrocarbon group may be any of a saturated hydrocarbon group, an unsaturated hydrocarbon group, and an aromatic hydrocarbon group. Examples of aromatic hydrocarbon groups include groups formed by removing a hydrogen atom from an aromatic compound such as a benzene ring, a naphthalene ring, an anthracene ring, a tetracene ring, a pentacene ring, a triphenylene ring, a pyrene ring, a fluorene ring, or an indene ring.

[0047] R in the above general formula (2) 2 ~R 4 are the same or different and each represents a monovalent substituent. 1 ~m 3 are the same or different and represent a number from 0 to 3. Examples of the monovalent substituent include a fluorine atom; a haloalkyl group such as a fluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, or a cycloheptyl group; a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, or a methyloxy group. linear or branched alkoxy groups having 1 to 20 carbon atoms, such as a silyl group or an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms, such as a methylamino group, an ethylamino group, a dimethylamino group or a diethylamino group; a cyclic amino group, such as a pyrrolidino group, a piperidino group or a morpholino group; a diarylamino group, such as a diphenylamino group or a carbazolyl group; an acyl group, such as an acetyl group, a propionyl group or a butyryl group; an alkenyl group having 2 to 30 carbon atoms, such as a styryl group; a halogen atom, such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a cyclic amino group having 1 to 10 carbon atoms, such as ... an aryl group having 5 to 20 carbon atoms which may be substituted with a silyl group, an amino group, or the like (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group described above); a heterocyclic group containing one or more of a nitrogen atom, a sulfur atom, and an oxygen atom which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (the heterocyclic group may be one consisting of only one ring, or may be a compound in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded to each other at one carbon atom, or may be a condensed heterocyclic group. Specific examples of the heterocyclic group include Specific examples of aromatic heterocyclic groups include a thiophene ring, a furan ring, a pyrrole ring, a benzothiophene ring, a benzofuran ring, an indole ring, a dibenzothiophene ring, a dibenzofuran ring, a carbazole ring, a thiazole ring, a benzothiazole ring, an oxazole ring, a benzoxazole ring, an imidazole ring, a benzimidazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a benzothiadiazole ring, a phenanthridine ring, etc.); an ester group, a thioether group, etc.These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, or the like.

[0048] In addition, p in the above general formula (2) represents a number of 1 to 4, and is preferably a number of 1 to 3.

[0049] In the above general formula (2), n 2 represents the number 0 or 1, with 0 being preferred.

[0050] The compound represented by the above general formula (2) includes a phenanthroline compound having a structure represented by the following general formula (3) which has only one phenanthroline skeleton, and the phenanthroline compound is particularly suitable as the organic material having a small surface work function. By using the phenanthroline compound represented by the following general formula (3) as the organic material, the light emitting characteristics and atmospheric stability of the organic EL element 1 can be further improved.

[0051] [ka] (In general formula (3), R 5 , R 6 m may be the same or different and represents a dialkylamino group or an alkoxy group. 4 , m 5 are the same or different and represent the number 1 or 2. 5 If there are multiple R 5 may be bonded to form a ring structure. 6 If there are multiple R 6 may be bonded to form a ring structure. 5 , R 6 The two alkyl groups in the dialkylamino group may be bonded to form a ring structure.

[0052] R in the above general formula (3) 5 , R 6 are the same or different and represent a dialkylamino group or an alkoxy group. The dialkylamino group is preferably one having an alkyl group having 1 to 20 carbon atoms, such as a methyl group or an ethyl group. More preferably, it is one having an alkyl group having 1 to 10 carbon atoms. The two alkyl groups in the dialkylamino group may have the same or different carbon numbers. Also preferred is an amino group in which two alkyl groups are linked, such as a cyclic amino group, for example, a pyrrolidino group (1-azacyclopentyl group (five-membered ring) or a piperidino group (1-azacyclohexyl group (six-membered ring)). The alkoxy group is R 2 ~R 4 is an alkoxy group.

[0053] -Metal complexes- The metal complex may be an alkali metal complex, an alkaline earth metal complex, an aluminum complex, a gallium complex, etc., and among these, an alkali metal complex is preferred. When the metal complex is an alkali metal complex, the light-emitting properties and atmospheric stability of the organic EL element are further improved. The metal complex may be 8-hydroxyquinolinolato-lithium (Liq), tris(8-hydroxyquinolinato)aluminum, tris(2-methyl-8-hydroxyquinolinato)aluminum, tris(8-hydroxyquinolinato)gallium, bis(10-hydroxybenzo[h]quinolinato)beryllium, bis(2-methyl-8-quinolinato)chlorogallium, bis(2-methyl-8-quinolinato)(o-cresolato)gallium, bis(2-methyl-8-quinolinato)-1-naphtholatoaluminum, bis(2-methyl-8-quinolinato)-2-naphtholatogallium, etc.

[0054] The alkali metal complex is preferably a lithium complex. When the metal complex is a lithium complex, the light-emitting properties and atmospheric stability of the organic EL device are further improved. Specific examples of the lithium complex include 8-hydroxyquinolinolato-lithium (Liq).

[0055] -Average thickness etc.- The average thickness of the electron injection layer 4 is preferably 0.5 to 100 nm, and more preferably 1 to 20 nm. The electron injection layer 4 can be formed by co-deposition using a vacuum deposition method. When stacked, the organic material with a small surface work function and the metal complex, or the mixed film thereof, may be formed in any order, and the average thickness of the first and second layers is preferably 0.5 to 50 nm, and more preferably 1 to 10 nm. When the electron injection layer 4 includes a mixed film of an organic material having a small surface work function and a metal complex, the mixing ratio of the alkali metal compound to the organic material having a small surface work function is preferably 10 to 90 mass %, more preferably 30 to 70 mass %. The average thickness of the electron injection layer 4 can be measured by, for example, a stylus step gauge or spectroscopic ellipsometry.

[0056] "Electron transport layer" The electron transport layer 5 may be made of any material that can be commonly used as a material for an electron transport layer. Specifically, examples of materials for the electron transport layer 5 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), pyrimidine derivatives such as 2-phenyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine (BPyPPM), pyrazine derivatives, 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, oxadiazole derivatives such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), 2,2',2"-(1,3,5-benzo[ imidazole derivatives such as 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) and other silole derivatives; aromatic tetracarboxylic anhydrides such as naphthalene and perylene; various metal complexes such as bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ)2) and tris(8-hydroxyquinolinato)aluminum (Alq3); and silole derivatives such as 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy). Examples of the material include organic silane derivatives, anthracene derivatives such as 9-(1-naphthyl)-10-(2-naphthyl)anthracene (1,2-ADN), and boron-containing compounds described in JP 2013-239691 A, WO 2014 / 133141 A, JP 2016-172728 A, JP 2016-199507 A, and JP 2016-199508 A, and one or more of these can be used. Among these, it is particularly preferable to use an anthracene derivative as the material of the electron transport layer 5.

[0057] The average thickness of the electron transport layer 5 is not particularly limited, but is preferably from 10 to 150 nm, and more preferably from 20 to 100 nm. The average thickness of the electron transport layer 5 can be measured by, for example, a stylus step gauge or spectroscopic ellipsometry.

[0058] "Light-emitting layer" The material for forming the light-emitting layer 6 may be any material that can be normally used as the material for the light-emitting layer 6, or a mixture of these materials may be used. Specifically, for example, the light-emitting layer 6 may contain bis[2-(2-benzothiazolyl)phenolato]zinc(II) (Zn(BTZ)2) and tris[1-phenylisoquinoline]iridium(III) (Ir(piq)3).

[0059] The material forming the light-emitting layer 6 may be a low molecular weight compound or a high molecular weight compound. In the present invention, the 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.

[0060] The light-emitting layer 6 may be composed of a host material and a guest material (e.g., a dopant), or may contain an exciplex formed of two types of organic compounds as a host. The mixing ratio of the guest material (e.g., a dopant) to the host material (e.g., an exciplex) is preferably 20% by mass or less, more preferably 10% by mass or less.

[0061] Examples of the polymeric material for forming the light-emitting layer 6 include polyacetylene-based compounds such as trans-polyacetylene, cis-polyacetylene, poly(di-phenylacetylene) (PDPA), and poly(alkylphenylacetylene) (PAPA); poly(para-phenylenevinylene) (PPV), poly(2,5-dialkoxy-para-phenylenevinylene) (RO-PPV), cyano-substituted-poly(para-phenylenevinylene) (CN-PPV), poly(2- Polyparaphenylenevinylene compounds such as dimethyloctylsilyl-paraphenylenevinylene) (DMOS-PPV) and poly(2-methoxy,5-(2'-ethylhexoxy)-paraphenylenevinylene) (MEH-PPV); polythiophene compounds such as poly(3-alkylthiophene) (PAT) and poly(oxypropylene)triol (POPT); poly(9,9-dialkylfluorene) (PDAF), poly(dioctylfluorene- Polyfluorene compounds such as α,ω-bis[N,N'-di(methylphenyl)aminophenyl]-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 of suitable polymeric materials include polyparaphenylene-based compounds such as poly(paraphenylene) (RO-PPP) and the like; polycarbazole-based compounds such as poly(N-vinylcarbazole) (PVK) and the like; polysilane-based compounds such as poly(methylphenylsilane) (PMPS), poly(naphthylphenylsilane) (PNPS) and poly(biphenylylphenylsilane) (PBPS) and the like; and further examples of suitable polymeric materials include boron compound-based polymeric materials described in JP-A-2011-184430 and JP-A-2012-151148.

[0062] Examples of low molecular weight materials for forming the light emitting layer 6 include a three-coordinate iridium complex having 2,2'-bipyridine-4,4'-dicarboxylic acid as a ligand, factolis(2-phenylpyridine)iridium (Ir(ppy)3), tris(8-hydroxyquinolinato)aluminum (Alq3), tris(2-methyl-8-hydroxyquinolinato)aluminum (Almq3), bis-(8-hydroxyquinolinato)zinc (Znq2), (1,10-phenanthroline)-tris-(4,4,4-trifluoro-1-(2-thienyl)-butane-1-yl)-1,2-difluorophenyl ... ,3-dionato) europium(III) (Eu(TTA)3(phen)), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II), and other metal complexes; distyrylbenzene (DSB), diaminodistyrylbenzene (DADSB), and other benzene-based compounds; naphthalene, Nile Red, and other naphthalene-based compounds; phenanthrene, and other phenanthrene-based compounds; chrysene, 6-nitrochrysene, and other chrysene-based compounds; perylene, N,N'-bis(2,5-di-t-butylphenyl)-3,4, Perylene compounds such as 9,10-perylene-dicarboximide (BPPC); coronene compounds such as coronene; anthracene compounds such as anthracene, bisstyrylanthracene, and 9-(1-naphthyl)-10-(2-naphthyl)anthracene (1,2-ADN); pyrene compounds such as pyrene; pyran compounds such as 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM); acridine compounds such as acridine; stilbene compounds such as stilbene; 2,5-dibenzoxazolethiol Thiophene compounds such as phene; 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;Examples of suitable compounds include 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; spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene; metal or metal-free phthalocyanine compounds such as phthalocyanine (H2Pc) and copper phthalocyanine; and boron compound materials described in JP-A-2009-155325, JP-A-2011-184430, and JP-A-2012-151149.

[0063] In one embodiment, the light-emitting layer 6 includes a phosphorescent material. As the phosphorescent material, a metal complex including a metal such as Ir or Pt can be used. As an iridium complex, factris(2-phenylpyridine)iridium (Ir(ppy)3), fac-tris(3-methyl-2-phenylpyridinato-N,C2'-)iridium(III) (Ir(mppy)3), tris[1-phenylisoquinoline]iridium(III) (Ir(piq)3), etc. As a platinum complex, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II) and the like can be used.

[0064] In another embodiment, the light-emitting layer 6 contains a fluorescent material. Examples of the fluorescent material include various metal complexes such as tris(8-hydroxyquinolinato)aluminum (Alq3), tris(2-methyl-8-hydroxyquinolinato)aluminum (Almq3), and bis-(8-hydroxyquinolinato)zinc (Znq2); benzene-based compounds such as distyrylbenzene (DSB) and diaminodistyrylbenzene (DADSB); naphthalene-based compounds such as naphthalene and Nile Red; phenanthrene-based compounds such as phenanthrene; chrysene and 6-nitrochrysene. chrysene compounds such as perylene, N,N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-dicarboximide (BPPC), and other perylene compounds; coronene compounds such as coronene; anthracene compounds such as anthracene and bisstyryl anthracene; pyrene compounds such as pyrene and BD-1; pyran compounds such as 4-(dicyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM), and other acridine compounds compounds; 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; Examples of such compounds include coumarin-based compounds such as malin; perinone-based compounds such as perinone; oxadiazole-based compounds such as oxadiazole; aldazine-based compounds; cyclopentadiene-based compounds such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP); quinacridone-based compounds such as quinacridone and quinacridone red; pyridine-based compounds such as pyrrolopyridine and thiadiazolopyridine; and spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene.

[0065] In yet another embodiment, the light-emitting layer 6 comprises a thermally activated delayed fluorescent material. Examples of the thermally activated delayed fluorescent material include 2,4,5,6-tetra(9-carbazole)-isophthalonitrile (4CzIPN), 4,5-di(9-carbazole)-phthalonitrile (2CzPN), 3,4,5,6-tetra(9-carbazole)-phthalonitrile (4CzPN), 2,3,5,6-tetra(9-carbazole)-terephthalonitrile (4CzTPN), 2,3,5,6-tetra(3,6-dimethyl-9-carbazole)-terephthalonitrile (4CzTPN-Me), 2,3,5,6-tetra(3,6-diphenyl-9-carbazole)-terephthalonitrile (4CzTPN-Ph), and further include compounds described in JP2012-193352A and WO2011 / 070963A.

[0066] The average thickness of the light-emitting layer 6 is not particularly limited, but is preferably from 10 to 150 nm, and more preferably from 20 to 100 nm. The average thickness of the light-emitting layer 6 may be measured by a stylus-type step gauge, or may be measured by a quartz crystal thickness gauge during the deposition of the light-emitting layer 6.

[0067] "Hole transport layer" As the organic material having hole transport properties used in the hole transport layer 7, any material that can be normally used as a material for the hole transport layer 7 may be used, and these may be mixed and used. Specifically, materials having a molecular structure with high donor properties, such as triarylamine, carbazole, phenoxazine, phenazine, acridine, azadibenzopyrene, and julolidine skeleton, are preferred. More specifically, the following m-MTDATA, TPT-1, TAPC, TPDI, HN-D1, HN-D2, N-TPA, EH44, PHZ-2Naph, TBDI, HT-01, N-DPA, spiro-MeO-TAD, Tris-PCz, α-NPD, TcTa, 2-SF-DMAC, 2-SF-PHX, SF-BCz, FATPA, and the like are preferred.

[0068] [ka] [ka] [ka]

[0069] The average thickness of the hole transport layer 7 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 7 can be measured by, for example, a stylus step gauge or spectroscopic ellipsometry.

[0070] "Hole injection layer" The hole injection material used for the hole injection layer 8 may be any material that can be normally used as the material for the hole injection layer 8, or a mixture of these materials may be used. Specifically, dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), 2,2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ), etc. may be used.

[0071] The average thickness of the hole injection layer 8 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 8 can be measured during deposition using a quartz crystal thickness gauge.

[0072] "anode" Examples of materials used for the anode 9 include ITO, IZO, Au, Pt, Ag, Cu, Al, and alloys containing these. Among these, it is preferable to use ITO, IZO, Au, Ag, or Al as the material for the anode 9. The average thickness of the anode 9 is not particularly limited, but is preferably 10 to 1000 nm, and more preferably 30 to 150 nm. Even when an opaque material is used as the material for the anode 9, by setting the average thickness to, for example, about 10 to 30 nm, the anode can be used as a transparent cathode in a top-emission organic EL device. The average thickness of the anode 9 can be measured by a quartz crystal film thickness meter during the deposition of the anode 9 .

[0073] "Sealing" The organic EL element 1 may be sealed, if necessary. For example, the organic EL element 1 may be sealed by a sealing container (not shown) having a concave space for accommodating the organic EL element 1, and an adhesive for bonding the edge of the sealing container to the substrate 2. Alternatively, the organic EL element 1 may be accommodated in a sealing container and sealed by filling it with a sealant made of an ultraviolet (UV) curable resin or the like.

[0074] When the organic EL element 1 is sealed using a sealing container or a sealing member, a desiccant that absorbs moisture may be placed inside the sealing container or the sealing member. A material that absorbs moisture may be used as the sealing container or the sealing member. A space may be formed inside the sealed sealing container or the sealing member.

[0075] Resin materials, glass materials, etc. can be used as the material of the sealing container or sealing member used to seal the organic EL element 1. Examples of the resin materials and glass materials used for the sealing container or sealing member include the same materials as those used for the substrate 2.

[0076] "Manufacturing method for organic EL elements" Next, a method for producing the organic EL element 1 will be described as an example of a method for producing the organic EL element of the present invention.

[0077] To manufacture the organic EL element 1, first, the cathode 3 is formed on the substrate 2. The cathode 3 can be formed by a sputtering method, a vacuum deposition method, a sol-gel method, a spray pyrolysis (SPD) method, an atomic layer deposition (ALD) method, a vapor phase deposition method, a liquid phase deposition method, etc. The cathode 3 may be formed by bonding a metal foil.

[0078] Next, on the cathode 3, an electron injection layer 4, an electron transport layer 5, a light emitting layer 6, a hole transport layer 7, and a hole injection layer 8 are formed in this order. The method for forming the electron injection layer 4, the electron transport layer 5, the light emitting layer 6, the hole transport layer 7, and the hole injection layer 8 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. Specifically, methods for forming the electron injection layer 4, the electron transport layer 5, the light-emitting layer 6, the hole transport layer 7, and the hole injection layer 8 include a coating method for coating an organic compound solution containing an organic compound that will become the electron injection layer 4, the electron transport layer 5, the light-emitting layer 6, the hole transport layer 7, and the hole injection layer 8, a vacuum deposition method, and an ESDUS (Evaporative Spray Deposition from Ultra-dilute Solution) method.

[0079] Next, an anode 9 is formed on the hole injection layer 8. The anode 9 can be formed, for example, in the same manner as the cathode 3. When a layer made of an inorganic oxide is formed on the cathode 3, the oxide is formed by, for example, a spray pyrolysis method, a sol-gel method, a sputtering method, a vacuum deposition method, or the like. Through the above steps, the organic EL element 1 is obtained.

[0080] "Sealing method" When sealing the organic EL element 1, it can be sealed by using a method commonly used for sealing an organic EL element.

[0081] <Display device, lighting device> In the organic EL element 1 of this embodiment, the electron injection barrier can be kept small while deterioration caused by water molecules can be reduced by using an organic material having a surface work function of 0.0 to 4.0 eV and a metal complex in the electron injection layer 4. Therefore, the organic EL element 1 has a low driving voltage and high atmospheric stability.

[0082] The organic EL element of the present invention can change the emission color by appropriately selecting the materials for the light-emitting layer, etc., and can also obtain a desired emission color by using a color filter, etc. Therefore, the organic EL element of the present invention can be suitably used as a light-emitting portion of a display device or a lighting device.

[0083] The display device of the present invention includes the organic EL element of the present invention, which has excellent productivity due to its simple element structure, a low driving voltage, and high atmospheric stability. For this reason, the display device of the present invention is preferable as a display device. The display device of the present invention emits light at a low applied voltage and has high atmospheric stability.

[0084] In addition, the lighting device of the present invention includes the organic EL element of the present invention, which has excellent productivity due to its simple element structure, a low driving voltage, and high atmospheric stability, and is therefore preferable as a lighting device. The lighting device of the present invention emits light at a low applied voltage and has high atmospheric stability. EXAMPLES

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0086] "Example 1" (Fabrication of organic EL elements) An organic EL device 1 having the structure shown in FIG. 1 was produced by the method described below and evaluated.

[0087] [Process 1] As the substrate 2, a commercially available transparent glass substrate having an average thickness of 0.7 mm and having an electrode (cathode 3) patterned to a width of 3 mm and made of ITO was prepared. Then, the surface of the substrate 2 having the cathode 3 was thoroughly washed with an organic solvent, and then subjected to UV ozone cleaning for 20 minutes.

[0088] Next, the substrate 2 on which the cathode 3 was formed was fixed to a substrate holder of a vacuum deposition apparatus. The inside of the chamber of the vacuum deposition apparatus was filled with 1×10 -5The pressure was reduced to 100 Pa.

[0089] [Process 2] First, 1 nm of Al is deposited on the cathode 3, and then a layer made of an organic material of the electron injection layer 4 is formed by deposition of a compound having the following structural formula (3-1): [ka] A film having a thickness of 3 nm was formed by vapor deposition of a phenanthroline compound represented by the structural formula (3-1). The phenanthroline compound of the structural formula (3-1) had a surface work function of 2.43 eV when formed on an electrode by ultraviolet photoelectron spectroscopy (UPS).

[0090] Furthermore, as the electron injection layer 4 made of a metal complex, a compound represented by the following structural formula: [ka] Then, a 3 nm thick film of 8-hydroxyquinolinolato-lithium (Liq) represented by the following structural formula: [ka] A 30 nm thick film of 1,2-ADN represented by the following formula was formed by vapor deposition.

[0091] Then, as the light-emitting layer 6, 1,2-ADN (host material) represented by the above structural formula and a dopant material represented by the following structural formula: [ka] A film of 25 nm was formed by vapor deposition of BD-1 represented by the formula: and BD-1 represented by the formula: in a mass ratio (1,2-ADN:BD-1) of 19:1.

[0092] After the light-emitting layer 6 is deposited, a hole-transporting layer 7 having the following structural formula: [ka] A 25 nm thick film of Tris-PCz represented by the following structural formula: was deposited thereon as a hole injection layer 8. [ka] A 5 nm thick film of HAT-CN represented by the formula (1) was formed by vapor deposition.

[0093] [Process 3] Next, an anode 9 made of aluminum and having a thickness of 120 nm was formed by vacuum deposition on the substrate 2 on which the hole injection layer 8 had been formed. The anode 9 was formed using a stainless steel deposition mask so that the deposition surface would be in the shape of a strip having a width of 3 mm, thereby obtaining the organic EL element of Example 1.

[0094] "Example 2" An organic EL element of Example 2 was obtained in the same manner as in Example 1, except that in forming the electron injection layer 4, the order of film formation of the organic material (the phenanthroline compound represented by structural formula (3-1)) and the metal complex (Liq) was reversed.

[0095] "Comparative Example 1" An organic EL device of Comparative Example 1 was obtained in the same manner as in Example 1, except that in forming the electron injection layer 4, only the organic material (the phenanthroline compound represented by the structural formula (3-1)) was deposited.

[0096] "Comparative Example 2" In forming the electron injection layer 4, an organic EL device of Comparative Example 2 was obtained in the same manner as in Example 1, except that only the metal complex (Liq) was deposited.

[0097] (Evaluation of organic EL element characteristics) Voltage was applied to the thus obtained elements of the examples and comparative examples using a Keithley 2400 Source Meter, and the luminance was measured using a Konica Minolta LS-100 to examine the relationship between the applied voltage and the luminance. These results are shown in Figure 2.

[0098] From FIG. 2, it was observed that in Comparative Example 1 and Example 2 in which the organic material of the electron injection layer 4 was adjacent to the electron transport layer 5, the device could be driven at a low voltage.

[0099] (Evaluation of the light-emitting surface of organic EL elements) The organic EL device thus fabricated was not sealed, and the change in the light-emitting surface was evaluated while the device was exposed to the atmosphere. Images of the light-emitting surface were periodically taken using a measuring device, and the time-dependent change in the deterioration width from the edge of the element was examined. Initial brightness 100cd / m 2 A constant current of 1000 mA was applied only during imaging, and images were taken every 5 minutes for 24 hours after the element was fabricated, and every 30 minutes thereafter. FIG. 3 shows an image of the light-emitting surface at the start of the measurement, and FIG. 4 shows an image of the light-emitting surface after 100 hours.

[0100] -Changes in the degree of deterioration over time- The edge of the light-emitting surface at the start of the measurement was considered to be in the initial state, and the extent of deterioration from this point was calculated from the image. Although dark spots were confirmed on each light-emitting surface, the change in the light-emitting area due to the dark spots was not included in this evaluation because it was not possible to evaluate the effect of the size of the foreign matter thought to be the cause. The change over time in the deterioration width from the edge of the light-emitting surface of each element is shown in Figure 5. In Figure 5, the horizontal axis shows the elapsed time of measurement, and the vertical axis shows the deterioration width from the edge of the light-emitting surface.

[0101] As a result of comparing the deterioration extent of each element, the result was obtained that the deterioration extent of Example 1 was smaller than that of Comparative Examples 1 and 2 and Example 2. Moreover, the deterioration extent of Example 2 and Comparative Example 2 was equivalent, and the deterioration extent of Comparative Example 1 was the largest. Regarding the difference between Comparative Example 1 and Comparative Example 2, it is shown that in an inverted structure organic EL element, the metal complex (Liq) has better atmospheric stability than the organic material (phenanthroline compound of structural formula (3-1)) used to form the electron injection layer 4. On the other hand, between Example 1 and Example 2, which are laminated structures, Example 1 has better atmospheric stability. This is thought to be because when a film of the metal complex (Liq) is formed on an electrode, water molecules are attracted to the electrode interface due to the weak interaction with lithium, accelerating the deterioration of the electrode interface. In addition, in a comparison between Comparative Example 1 and Example 1, Example 1 in which the metal complex (Liq) is laminated is superior in atmospheric stability. This result suggests that laminating the metal complex (Liq) has the effect of suppressing deterioration of the light-emitting surface.

[0102] -Changes in humidity over time- The humidity in the measurement environment for each element was also measured, and the change in humidity over time is shown in Figure 6.

[0103] For all elements, the humidity remained stable at 50-55%rh during the measurement period, and it can be said that the amount of water molecules in the air was about the same for each measurement. Therefore, in this comparison, the difference in the measurement environment was small, and it is believed that the difference in the atmospheric stability of organic EL elements using each material was fully evaluated.

[0104] - Comparison of deterioration range - In order to compare the degree of deterioration of various organic EL elements, the square of the deterioration degree was linearly approximated as follows, and the shrink coefficient α was calculated as the slope of the straight line. w 2 =αt+β Here, w is the deterioration width from the end, and t is the elapsed time. 1000cd / m for various organic EL elements 2 The relationship between the voltage value and the shrink factor is shown in Figure 7.

[0105] From FIG. 7, it can be seen that Comparative Example 1, which contains only an organic material (the phenanthroline compound of structural formula (3-1)), can be driven at a low voltage but has poor atmospheric stability, while Comparative Example 2, which contains only a metal complex (Liq), has excellent atmospheric stability but requires an increased driving voltage. Therefore, in order to achieve both low-voltage operation and atmospheric stability, it can be said that the layer structures of Examples 1 and 2, in which an organic material (the phenanthroline compound of structural formula (3-1)) and a metal complex (Liq) are laminated, are suitable. [Explanation of symbols]

[0106] 1: Organic EL (electroluminescence) element 2: Substrate 3: Cathode 4:Electron injection layer 5:Electron transport layer 6: Light-emitting layer 7: Hole transport layer 8: Hole injection layer 9: Anode

Claims

1. A device comprising, in this order, a substrate, a cathode, an electron injection layer, a light emitting layer, and an anode; The organic electroluminescence device, wherein the electron injection layer contains an organic material having a surface work function of 0.0 to 4.0 eV and a metal complex.

2. The organic material is represented by the following general formula (1): 【Chemistry 1】 (In general formula (1), R 1 represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent linear or cyclic hydrocarbon group which may have a substituent, 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 is an integer of 1 to 4.) and a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (2): 【Chemistry 2】 (In general formula (2), X 1 , X 2 are the same or different and each represents a nitrogen atom, an oxygen atom, a sulfur atom, or a divalent linking group which may have a substituent. L represents a direct bond or a p-valent linking group. 2 represents a number of 0 or 1, and p represents a number of 1 to 4. q represents a number of 0 or 1, and when p is 1, q is 0. R 2 ~R 4 m may be the same or different and represents a monovalent substituent. 1 ~m 3 are the same or different and represent a number from 0 to 3. 2 ~R 4 , X 1 , X 2 may be bonded to form a ring structure, R 2 If there are multiple R 2 may be bonded to form a ring structure. 3 If there are multiple R 3 may be bonded to form a ring structure. 4 If there are multiple R 4 The organic electroluminescence device according to claim 1 , wherein the compound is at least one selected from the group consisting of compounds having a structure represented by the following formula:

3. The organic material is represented by the following general formula (3): 【Chemistry 3】 (In general formula (3), R 5 , R 6 are the same or different and each represents a dialkylamino group or an alkoxy group. 4 , m 5 are the same or different and represent the number 1 or 2. 5 If there are multiple R 5 may be bonded to form a ring structure. 6 If there are multiple R 6 may be bonded to form a ring structure. 5 , R 6 The organic electroluminescence device according to claim 1 , wherein the dialkylamino group is a phenanthroline compound having a structure represented by the following formula:

4. The organic electroluminescence device according to claim 1 , wherein the metal complex is an alkali metal complex.

5. The organic electroluminescence device according to claim 1 , wherein the metal complex is a lithium complex.

6. The organic electroluminescence device according to claim 1 , wherein the electron injection layer is composed of a single layer containing the organic material and the metal complex.

7. the electron injection layer is formed by stacking a layer containing the organic material and a layer containing the metal complex, The organic electroluminescence device according to claim 1 , comprising, in order from the cathode side, a layer containing the organic material and a layer containing the metal complex.

8. the electron injection layer is formed by stacking a layer containing the organic material and a layer containing the metal complex, The organic electroluminescence device according to claim 1 , comprising, in order from the cathode side, a layer containing the metal complex and a layer containing the organic material.

9. A display device comprising the organic electroluminescence element according to claim 1.

10. A lighting device comprising the organic electroluminescence element according to claim 1.

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