Organic thin film and method for producing organic thin film, organic electroluminescence element, display device, lighting device, organic thin film solar cell, photoelectric conversion element, thin film transistor, coating composition, and material for organic electroluminescence element

Abstract

The present invention provides an organic thin film which enables the achievement of excellent electron injection properties and electron transport properties if used in an electron injection layer of an organic EL element. The present invention relates to an organic thin film which is characterized by: being a single film containing a first material that is a hexahydropyrimidopyrimidine compound having a structure represented by general formula (1) and a second material that transports electrons; or being a multilayer film comprising a film that contains the first material and a film that contains the second material. (In general formula (1), R1 represents an optionally substituted aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent chain or cyclic hydrocarbon group, a group that is obtained by combining two or more of these groups, or a group that is obtained by combining one or more of these groups and a nitrogen atom; and n represents an integer from 1 to 4.)

Description

[Technical field]

[0001] The present invention relates to an organic thin film and a method for producing an organic thin film, an organic electroluminescence (hereinafter, electroluminescence (field emission) may be abbreviated as "EL") element, a display device, a lighting device, an organic thin film solar cell, a thin film transistor, a photoelectric conversion element, a coating composition, and a material for an organic electroluminescence element. [Background technology]

[0002] Organic EL elements are thin, soft, and flexible. Furthermore, displays using organic EL elements are capable of displaying images with higher brightness and resolution than the currently mainstream liquid crystal display devices and plasma display devices. Furthermore, displays using organic EL elements have a wider viewing angle than liquid crystal display devices. For this reason, it is expected that displays using organic EL elements will be used more widely in the future as displays for televisions, mobile phones, and the like. Organic EL elements are also expected to be used as lighting devices.

[0003] An organic EL element is a laminate of a cathode, a light-emitting layer, and an anode. In an organic EL element, the difference in energy between the work function of the anode and the highest occupied molecular orbital (HOMO) of the light-emitting layer is smaller than the difference in energy between the work function of the cathode and the lowest unoccupied molecular orbital (LUMO) of the light-emitting layer. Therefore, it is more difficult to inject electrons from the cathode into the light-emitting layer than to inject holes from the anode. For this reason, in conventional organic EL elements, an electron injection layer is disposed between the cathode and the light-emitting layer to promote the injection of electrons from the cathode into the light-emitting layer. In addition, efforts have been made to improve electron injection and transport properties by doping a layer disposed between the cathode and the light-emitting layer with a dopant (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

[0004] An example of the electron injection layer of an organic EL element is an inorganic oxide layer (see, for example, Non-Patent Document 3). However, the electron injection property of an inorganic oxide layer is insufficient. There is also a technique for improving the electron injection properties of an organic EL element by forming an electron injection layer on an inorganic oxide layer. For example, Non-Patent Document 4 describes an organic EL element having an electron injection layer made of polyethyleneimine. Non-Patent Document 5 describes that amines are effective in improving the electron injection rate. Non-Patent Documents 6, 7, and 8 describe the effect of amino groups on electron injection at the interface between an electrode and an organic layer. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Karsten Walzer et al., Chemical Review, Vol. 107, 2007, p1233-1271 [Non-Patent Document 2] Peng Wei and 3 others, Journal of the American Chemical Society, Vol. 132, 2010, p. 8852 [Non-Patent Document 3] Jiangshan Chen et al., Journal of Materials Chemistry, Vol. 22, 2012, pp. 5164-5170 [Non-Patent Document 4] Hyosung Choi et al., Advanced Materials, Vol. 23, 2011, p. 2759 [Non-Patent Document 5] Yinhua Zho and 21 others, Science, Vol. 336, 2012, p. 327 [Non-Patent Document 6] Young-Hoon Kim and 5 others, "Advanced Functional Materials", 2014, DOI:10.1002 / adfm.201304163 [Non-Patent Document 7] Stephen Forfl and 4 others, "Advanced Materials", 2014, DOI:10.1002 / adma.201304666 [Non-Patent Document 8] Stephen Forfl and 5 others, "Advanced Materials", Vol. 26, 2014, DOI:10.1002 / adma.201400332 [Non-Patent Document 9] Peng Wei and 3 others, Journal of the American Chemical Society, Vol. 132, 2010, p. 8852 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional organic EL devices including an electron injection layer, there has been a demand for further improvements in the electron injection and electron transport properties.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic thin film that can provide excellent electron injection and electron transport properties when used in an electron injection layer of an organic EL device, a coating composition that can be suitably used in producing the organic thin film, and a material for organic EL devices that serves as a raw material for the organic thin film and coating composition. Another object of the present invention is to provide an organic EL element using the organic thin film of the present invention, a display device and a lighting device including this organic EL element, and an organic thin film solar cell, a photoelectric conversion element, and an organic thin film transistor including the organic thin film of the present invention. [Means for solving the problem]

[0008] The present inventors have focused on basic organic materials as materials for use in the electron injection layer of an organic EL device and have found that an organic thin film containing a hexahydropyrimidopyrimidine compound having a specific structure, which is an organic material having an acid dissociation constant pKa of 1 or more, and a material that transports electrons, can be used as the electron injection layer of an organic EL device.

[0009] In other words, the above organic materials with a pKa of 1 or more can absorb protons (H + Therefore, in an organic EL device having an electron injection layer made of the above organic thin film, the organic material with a pKa of 1 or more can extract protons (H + It is presumed that by extracting the ions, a negative charge is generated, improving the electron injection property.

[0010] The present invention has been completed based on the above findings, and the gist of the present invention is as follows. [1] An organic thin film characterized in that it is a single film containing a first material, which is a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), and a second material that transports electrons, or a laminated film of a film containing the first material and a film containing the second material.

[0011] [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. n is an integer of 1 to 4.

[0012] [2] The organic thin film according to [1], wherein the first material is a hexahydropyrimidopyrimidine compound in which n in general formula (1) is 2 or 3.

[0013] [3] A laminate film comprising an oxide layer and a layer of the organic thin film according to [1] or [2] formed on the oxide layer.

[0014] [4] An organic electroluminescence element having an emitting layer between a cathode and an anode, the organic electroluminescence element comprising the organic thin film according to [1] or [2] or the laminated film according to [3] between the cathode and the emitting layer.

[0015] [5] The organic electroluminescence element according to [4], further comprising an inorganic oxide layer between the cathode and the organic thin film.

[0016] [6] The organic electroluminescent element according to [4] or [5], further comprising a laminated film including a film containing the first material and the second material and a film containing the second material between the cathode and the light-emitting layer.

[0017] [7] The organic electroluminescence element according to [6], further comprising a layer containing the second material between the light-emitting layer and the film containing the first material and the second material.

[0018] [8] The organic electroluminescent element according to [6], further comprising a layer containing the second material between the cathode and the film containing the first material and the second material.

[0019] [9] The organic electroluminescence element according to any one of [4] to [8], further comprising a layer containing the second material between the anode and the light-emitting layer.

[0020]

[10] The organic electroluminescence device according to any one of [4] to [9], wherein the light-emitting layer contains the second material.

[0021]

[11] A material for an organic electroluminescence device, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1):

[0022] [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. n is an integer of 1 to 4.

[0023]

[12] An organic electroluminescence element having an emitting layer between a cathode and an anode, the organic electroluminescence element comprising a layer containing the material for organic electroluminescence elements according to

[11] between the cathode and the anode.

[0024]

[13] The organic electroluminescence device according to

[12] , further comprising a layer containing the material for an organic electroluminescence device according to

[11] between the cathode and the light-emitting layer.

[0025]

[14] The organic electroluminescence device according to

[12] or

[13] , further comprising an inorganic oxide layer between the cathode and the layer containing the material for an organic electroluminescence device according to

[11] .

[0026]

[15] A display device comprising the organic electroluminescence element according to any one of [4] to

[10] and

[12] to

[14] .

[16] A lighting device comprising the organic electroluminescence element according to any one of [4] to

[10] and

[12] to

[14] .

[0027]

[17] A material for an organic thin-film solar cell, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1):

[0028] [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. n is an integer of 1 to 4.

[0029]

[18] An organic thin-film solar cell comprising either the organic thin-film according to [1] or [2], the laminated film according to [3], or a layer containing the material for organic thin-film solar cells according to

[17] .

[0030]

[19] A material for a photoelectric conversion element, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1):

[0031] [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. n is an integer of 1 to 4.

[0032]

[20] A photoelectric conversion element comprising any one of the organic thin film according to [1] or [2], the laminated film according to [3], or a layer containing the material for photoelectric conversion elements according to

[19] .

[0033]

[21] A material for a thin film transistor, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1):

[0034] [ka] (In general formula (1), R1 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. n is an integer of 1 to 4.

[0035]

[22] A thin film transistor comprising any one of the organic thin film according to [1] or [2], the laminated film according to [3], or a layer containing the material for thin film transistors according to

[21] .

[0036]

[23] A coating composition comprising a first material which is a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), and a second material which transports electrons:

[0037] [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. n is an integer of 1 to 4.

[0038]

[24] A coating composition comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1):

[0039] [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. n is an integer of 1 to 4.

[0040]

[25] A method for producing an organic thin film, comprising the steps of: forming, on a surface to be formed, a single film containing a first material, which is a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), and a second material that transports electrons; or forming, in order, a film containing the first material and a film containing the second material on a surface to be formed:

[0041] [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. n is an integer of 1 to 4.

[0042]

[26] A method for producing an organic thin film, comprising the step of forming a film containing a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1) on a surface on which the film is to be formed:

[0043] [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. n is an integer of 1 to 4.

[0044]

[27] The method for producing an organic thin film according to

[26] , wherein the surface to be formed contains a second material. Effect of the Invention

[0045] The organic thin film of the present invention includes at least a first material made of a specific organic material having an acid dissociation constant pKa of at least 1, and a second material that transports electrons. Therefore, when the organic thin film of the present invention is used, for example, as an electron injection layer of an organic EL device, excellent electron injection and electron transport properties are obtained. The organic EL device of the present invention has the organic thin film of the present invention between the cathode and the light-emitting layer, and therefore the organic thin film provides excellent electron injection and transport properties. In addition, the organic thin film of the present invention, which includes a first material made of a specific hexahydropyrimidopyrimidine compound having an acid dissociation constant pKa of 1 or more and a second material that transports electrons, can be formed by either coating or vapor deposition, so there are fewer process restrictions when manufacturing an organic EL device including the organic thin film of the present invention, and it is easy to use as a material for a layer that constitutes an organic EL device. The method for manufacturing an organic thin film of the present invention is a method for manufacturing such an organic thin film of the present invention.

[0046] The coating composition of the present invention contains a first material made of a specific organic material having an acid dissociation constant pKa of 1 or more, and a second material that transports electrons. Therefore, by applying the coating composition of the present invention onto a surface on which an organic thin film is to be formed, an organic thin film suitable for the electron injection layer of an organic EL device can be obtained.

[0047] The material for organic EL devices of the present invention is a useful material used in the organic thin film or coating composition of the present invention used in the production of organic EL devices, etc. In addition, the material is also useful in that it can be used alone as an electron injection layer or electron transport layer.

[0048] The display device and lighting device of the present invention have a low driving voltage and excellent characteristics since they include the organic EL element of the present invention. Moreover, the organic thin-film solar cell, photoelectric conversion element and organic thin-film transistor of the present invention have excellent properties since they contain the organic thin film of the present invention. [Brief description of the drawings]

[0049] [Figure 1]FIG. 1 is a schematic cross-sectional view illustrating an example of an organic EL element of the present invention. [Diagram 2] FIG. 1 is a schematic cross-sectional view illustrating an example of an organic EL element of the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing another example of the laminate structure of the organic EL element of the present invention. [Figure 4] FIG. 2 is a schematic cross-sectional view showing another example of the laminate structure of the organic EL element of the present invention. [Figure 5-1] FIG. 1 is a schematic cross-sectional view showing an example of an organic thin film of the present invention. [Figure 5-2] FIG. 1 is a schematic cross-sectional view showing an example of an organic thin film of the present invention. [Figure 6-1] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 6-2] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 7-1] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 7-2] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 8-1] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 8-2] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 9-1] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 9-2] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 10-1] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 10-2] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 11-1] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 11-2] FIG. 1 is a schematic cross-sectional view showing an example of a laminate structure of an organic thin film of the present invention. [Figure 12]1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Examples 1 and 2 and Comparative Example 1. [Figure 13] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Examples 3 and 4 and Comparative Examples 1 and 2. [Figure 14] FIG. 2 is a diagram showing the light emission behavior of the organic EL elements prepared in Examples 3 and 4 and Comparative Examples 1 and 2. [Figure 15] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Example 5 and Comparative Example 3. [Figure 16] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Examples 5 and 6. [Figure 17] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Examples 7 and 8 and Comparative Example 4. [Figure 18] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Examples 9 and 10. [Figure 19] 1 is a graph showing the change over time in luminance of the organic EL elements prepared in Examples 9 and 10. [Figure 20] FIG. 1 is a cross-sectional view showing the configuration of an organic EL element produced in Example 11. [Figure 21] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Examples 8 and 11. [Figure 22] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Examples 12 to 14 and Comparative Examples 5 and 6. [Diagram 23] 1 is a graph showing the change over time in luminance of the organic EL elements produced in Example 13 and Comparative Example 6. [Figure 24] 1 is a graph showing the change over time in luminance of the organic EL elements prepared in Examples 12 and 14. [Diagram 25] FIG. 15 is a cross-sectional view showing the configuration of an organic EL element prepared in Example 15. [Figure 26] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Example 15 and Comparative Example 7. [Figure 27]1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Example 16 and Comparative Examples 8 and 9. [Figure 28] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Example 17 and Comparative Examples 10 and 11. [Figure 29] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Example 18 and Comparative Examples 12 and 13. [Diagram 30] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Example 19 and Comparative Example 15. [Diagram 31] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Example 20 and Comparative Example 14. [Diagram 32] 1 is a graph showing the change over time in luminance of the organic EL elements produced in Example 20 and Comparative Example 14 in a room temperature environment. [Diagram 33] 1 is a graph showing the change over time in luminance in a high temperature environment (85° C.) of the organic EL elements produced in Example 20 and Comparative Example 14. [Diagram 34] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Examples 21 and 22 and Comparative Example 16. [Diagram 35] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Example 23 and Comparative Example 17. [Diagram 36] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements produced in Example 24 and Comparative Example 18. [Figure 37] 1 is a graph showing the relationship between the applied voltage and the luminance of the organic EL elements prepared in Examples 25 and 26 and Comparative Example 19. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The present invention will be described in detail below. "Materials for organic thin films and organic EL devices" The organic thin film of the present invention comprises a first material which is a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), and a second material which transports electrons. The organic thin film of the present invention may be a single layer film containing the first material and the second material, or may be a laminate film in which a layer containing the first material and a layer containing the second material are laminated.

[0051] [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. n is an integer of 1 to 4.

[0052] The first material constituting the organic thin film of the present invention is the above-mentioned organic material having a pKa of 1 or more, so that protons (H + ) is capable of withdrawing protons. The first material preferably has a pKa of 5 or more, more preferably 11 or more. The higher the pKa of the first material, the higher the ability of the first material to withdraw protons from the second material. As a result, when the organic thin film is used as, for example, an electron injection layer of an organic EL device, excellent electron injection and electron transport properties are obtained. In addition, it has been confirmed that the metal oxide is suitably coordinated to the defective portion of the inorganic compound, thereby preventing reactions at the interface with oxygen or water entering from the outside, and thus improving the atmospheric stability of the device. Furthermore, by interacting with the inorganic compound, the work function of the inorganic compound can be reduced, and as a result, the electron injection property of the metal oxide layer can be improved. Therefore, the organic thin film of the present invention can be used not only in devices composed of only organic compounds, but also in devices composed of organic and inorganic compounds, and can exhibit the effect of improving electron injection properties and atmospheric stability. In addition, the fact that the work function of the inorganic compound can be reduced means that the efficiency of electron extraction from the organic compound used in the active layer that absorbs light and generates electrons in organic thin film solar cells and photoelectric conversion elements can be improved. The organic thin film of the present invention is characterized in that it contains a hexahydropyrimidopyrimidine compound having the structure represented by the above general formula (1) as a first material, and when the organic thin film of the present invention is used in an electron injection layer, excellent electron injection and electron transport properties are obtained. A material for an organic EL device containing a hexahydropyrimidopyrimidine compound having the structure represented by the above general formula (1) that exerts such excellent effects is also one aspect of the present invention, and excellent electron injection and electron transport properties can be obtained even by using this material alone in an electron injection layer or electron transport layer. In the present invention, "pKa" usually means "acid dissociation constant in water", but if it cannot be measured in water, it means "acid dissociation constant in dimethyl sulfoxide (DMSO)", and if it cannot be measured even in DMSO, it means "acid dissociation constant in acetonitrile". Preferably, it means "acid dissociation constant in water".

[0053] 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.

[0054] 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 linear or branched alkoxy group having 1 to 20 carbon atoms, such as 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 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; aryl groups having 5 to 20 carbon atoms, 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, etc. (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group described above); heterocyclic groups containing one or more of a nitrogen atom, a sulfur atom, and an oxygen atom having 4 to 20 carbon atoms, 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, etc. (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 heterocyclic ring are directly bonded to each other at one carbon atom, or may be a condensed heterocyclic group. Specific examples of the heterocyclic group include the specific examples of the aromatic heterocyclic group described above); ester groups, thioether groups, etc. These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, etc.

[0055] In the above general formula (1), n ​​is an integer of 1 to 4, with 2 or 3 being preferred. Specific examples of the hexahydropyrimidopyrimidine compound having the structure represented by the above general formula (1) include the compounds represented by the following formulas (2-1) to (2-34).

[0056] [ka] [ka] [ka] [ka] [ka]

[0057] The compound represented by the above general formula (1) can be synthesized by using a halogen compound having iodine, bromine, chlorine or fluorine and hexahydropyrimidopyrimidine as raw materials through Ullmann coupling reaction, Buchwald-Hartwig amination reaction, nucleophilic substitution reaction, or the like, as shown in the following formula (3).

[0058] [ka]

[0059] The second material may be any material capable of transporting electrons, and is preferably an organic material. More preferably, the second material is an organic material having a lowest unoccupied molecular orbital (LUMO) level of 2.0 eV to 4.0 eV, and among these, it is an n-type organic semiconductor material having a LUMO level of 2.5 eV to 3.5 eV. For example, any of the conventionally known materials shown below may be used as the material for the electron transport layer of an organic EL device, and among these, a material that satisfies the above LUMO level requirement is preferred. Specifically, the second material is phenyl-dipyrenylphosphine oxide (POPy 2), pyridine derivatives such as tris-1,3,5-(3'-(pyridin-3''-yl)phenyl)benzene (TmPhPyB), 1,3,5-tris(6-(3-(pyridin-3-yl)phenyl)pyridin-2-yl)benzene, and 8,9-diphenyl-7,10-(3-(pyridin-3-yl))fluoranthene, quinoline derivatives such as (2-(3-(9-carbazolyl)phenyl)quinoline (mCQ), and 2-phenyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine (BP pyrimidine derivatives such as yPPM, 2-methyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine, 9-(4-(4,6-diphenylpyrimidin-2-yl)phenyl)-9H-carbazole, pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT), tris-1,3, 5-(3'-(pyridin-3''-yl)phenyl)triazine (TmPhPyTz), tris-1,3,5-([1,1'-biphenyl]-3-yl)triazine, 2-(3-(4,6-di(pyridin-3-yl)-1,3,5-triazin-2-yl)phenyl)-1-phenyl-1H-benzo[d]imidazole, 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9H-3,9'-bicarbazole, 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9H- triazine derivatives such as 11-(4,6-diphenyl-1,3,5-triazin-2-yl)-12-phenyl-11,12-dihydroindolo[2,3-a]carbazole, 12-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-12H-benzofuro[2,3,a]carbazole, 9-((4-(4,6-dipyridin-3-yl)-1,3,5-triazin-2-yl)phenyl)-9H-carbazole, 3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,triazole derivatives such as 4-triazole (TAZ), oxazole derivatives, oxadiazole derivatives such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), imidazole derivatives such as 2,2',2''-(1,3,5-benzotriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic tetracarboxylic anhydrides such as naphthalene and perylene, compounds having a heterocycle containing a carbonyl group such as the compound represented by formula (24) described later, bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ), 2 ), tris(8-hydroxyquinolinato)aluminum (Alq 3 ), organic silane derivatives such as silole derivatives such as 2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), and boron-containing compounds described in Japanese Patent Application No. 2012-228460, Japanese Patent Application No. 2015-503053, Japanese Patent Application No. 2015-053872, Japanese Patent Application No. 2015-081108, and Japanese Patent Application No. 2015-081109. One or more of these may be used. Moreover, the material of the light-emitting layer described later can also be used as the second material.

[0060] Among these second materials, POPy 2 phosphine oxide derivatives such as those represented by the following formulas (4) to (7), boron-containing compounds such as those represented by the following formulas (4) to (7), Alq 3 It is more preferable to use a metal complex such as TmPhPyB, a pyridine derivative such as TmPhPyTz, or a triazine derivative such as TmPhPyTz. Among these second materials, it is particularly preferable that the second material is a boron-containing compound or a triazine derivative. 1 represents an integer of 1 or greater.

[0061] [ka]

[0062] When a boron-containing compound is used as the second material having electron transport properties, a uniform organic thin film can be easily obtained by applying a coating composition containing a first material and a second material. Such a coating composition containing the first material represented by the above general formula (1) and the second material transporting electrons is also one aspect of the present invention. In addition, since the hexahydropyrimidopyrimidine compound, which is the first material represented by the above general formula (1), has extremely excellent electron injection properties, a coating composition containing the first material and not the second material is also useful. Such a coating composition containing the hexahydropyrimidopyrimidine compound, which is the first material represented by the above general formula (1), is also one aspect of the present invention. In addition, boron-containing compounds and triazine derivatives have deep lowest unoccupied molecular orbital (LUMO) energies, making them suitable materials for the electron injection layer of organic electroluminescence devices. Therefore, organic thin films containing boron-containing compounds as the second material are particularly suitable for the electron injection layer of organic electroluminescence devices.

[0063] The ratio of the first material and the second material contained in the organic thin film of the present invention is not particularly limited, and can be appropriately determined according to the type of compound used for each of the first material and the second material. The ratio of the first material and the second material is preferably 0.1:99.9 to 20:1 in mass ratio (first material:second material). More preferably, it is 0.5:99 to 10:1. For example, even when the compound of (2-2) above is used as the first material and the boron-containing compound represented by the formula (4) above is used as the second material, the ratio of the first material and the second material is preferably such a mass ratio. In the above ratio, the organic thin film contains the first material and the second material, and thus the effect of improving the electron transport property and the electron injection property becomes significant.

[0064] The organic thin film in the present invention may be a single film containing the first material and the second material, or may be a laminated film of a film containing at least the first material and a film containing at least the second material. In the case of a laminated film, it may be a laminated film of a film containing only the first material and a film containing only the second material, or a laminated film of a film containing the first material and the second material and a film containing only one of the first material and the second material. In the case of a laminated film of a film containing the first material and the second material and a film containing only one of the first material and the second material, the film containing only one of the first material and the second material may contain either the first material or the second material, but it is preferable that it contains the second material. Furthermore, when such an organic thin film is used as a layer constituting an organic electroluminescence element, either the film containing the first material and the second material or the film containing only one of the first material and the second material may be on the cathode side, but it is preferable that the film containing only one of the first material and the second material is on the cathode side.

[0065] When the organic thin film in the present invention is a laminated film of a film containing a first material and a second material and a film containing only the first material, both of the two laminated films contain the first material, and the first materials contained in the two films may be the same or different. Similarly, when the organic thin film in the present invention is a laminated film of a film containing a first material and a second material and a film containing only the second material, the second material is contained in both of the two laminated films, and the second materials contained in the two films may be the same or different.

[0066] "Method of manufacturing organic thin films" Next, the method for producing an organic thin film of the present invention will be described with reference to examples. The organic thin film of the present invention includes a first material made of a hexahydropyrimidopyrimidine compound having a structure represented by the above general formula (1) and having an acid dissociation constant pKa of 1 or more, and a second material that transports electrons. Both the first material and the second material have relatively large molecular weights, so that the organic thin film of the present invention can be formed not only by coating but also by vapor deposition. Therefore, there are few process restrictions when manufacturing an organic EL device including the organic thin film of the present invention, and it is easy to use it as a material for a layer constituting an organic EL device. When the organic thin film is produced by deposition, it can be produced by the same method as when other layers constituting the organic EL element are produced by deposition, and the first material and the second material may be simultaneously deposited or sequentially deposited. When deposited sequentially, either the first material or the second material may be deposited first. In addition, either one may be deposited first and then both may be co-deposited, or both may be co-deposited and then either one may be deposited. Such a method for producing an organic thin film including a step of simultaneously depositing a first material, which is a hexahydropyrimidopyrimidine compound having a structure represented by the above general formula (1), and a second material that transports electrons on a surface on which the organic thin film is to be formed is one of the preferred embodiments of the method for producing an organic thin film of the present invention. In addition, a method for producing an organic thin film comprising a step of first depositing either a first material or a second material onto a surface on which an organic thin film is to be formed, and then depositing the other material or both of the materials, or a method for producing an organic thin film comprising a step of simultaneously depositing a first material and a second material onto a surface on which an organic thin film is to be formed, and then depositing either the first material or the second material onto the surface on which an organic thin film is to be formed, is also one of suitable embodiments of the method for producing an organic thin film of the present invention.

[0067] The organic thin film of the present invention can also be produced by coating. In this case, a coating composition containing a first material and a second material that transports electrons is prepared and the coating composition is applied, or a coating composition containing a first material and a coating composition containing a second material are prepared and applied in order to produce an organic thin film. When coating in order, either the coating composition containing the first material or the coating composition containing the second material may be applied first. Also, a coating composition containing only one of the materials may be applied, and then a coating composition containing both of these materials may be applied, or a coating composition containing only one of the materials may be applied, and then a coating composition containing both of these materials may be applied. Such a method for producing an organic thin film that includes a step of coating a coating composition containing a first material, which is a hexahydropyrimidopyrimidine compound having a structure represented by the above general formula (1), and a second material that transports electrons on a surface on which the organic thin film is to be formed is one of the preferred embodiments of the method for producing an organic thin film of the present invention. Furthermore, a method for producing an organic thin film comprising a step of first applying either a coating composition containing only the first material or a coating composition containing only the second material onto a surface on which an organic thin film is to be formed, and a step of applying a coating composition containing the other or both of the materials onto the coating film formed by the step, or a method for producing an organic thin film comprising a step of applying a coating composition containing both the first material and the second material, and a step of applying a coating composition containing only either the first material or the second material onto the coating film formed by the step, is also one of the preferred embodiments of the method for producing an organic thin film of the present invention. In the following, a method for producing an organic thin film by preparing a coating composition containing a first material consisting of a hexahydropyrimidopyrimidine compound having a structure represented by a specific general formula (1) with a pKa of 1 or more and a second material that transports electrons, and applying the coating composition will be described.

[0068] The coating composition can be obtained, for example, by supplying a predetermined amount of each of the first material and the second material into a solvent contained in a container, or by supplying a solvent to the first material and the second material contained in a container and stirring them to dissolve them. The solvent used to dissolve the first material and the second material may be, for example, an inorganic solvent, an organic solvent, or a mixed solvent containing these. Examples of inorganic solvents include nitric acid, sulfuric acid, ammonia, hydrogen peroxide, water, phosphoric acid, and hydrochloric acid.

[0069] Examples of organic solvents include ketone-based solvents such as methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), diisobutyl ketone, 3,5,5-trimethylcyclohexanone, diacetone alcohol, cyclopentanone, and cyclohexanone; alcohol-based solvents such as methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol (DEG), and glycerin; diethyl ether, diisopropyl ether, and 1,2-dimethoxyethane. Ether solvents such as diethyl ether (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), diethylene glycol ethyl ether (carbitol), etc.; cellosolve solvents such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, etc.; aliphatic hydrocarbon solvents such as hexane, pentane, heptane, cyclohexane, etc.; aromatic hydrocarbon solvents such as toluene, xylene, benzene, etc.; pyridine, pyrazine, furan, pyrrole, thiophene, etc. aromatic heterocyclic compound solvents such as methylpyrrolidone; amide solvents such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA); halogen compound solvents such as chlorobenzene, dichloromethane, chloroform, and 1,2-dichloroethane; ester solvents such as ethyl acetate, methyl acetate, and ethyl formate; sulfur compound solvents such as dimethyl sulfoxide (DMSO) and sulfolane; nitrile solvents such as acetonitrile, propionitrile, and acrylonitrile; formic acid, acetic acid, trichloroacetic acid, and trifluoroacetic acid. Examples of the organic solvent include various organic solvents such as organic acid solvents such as those mentioned above, organic amine solvents such as triethylamine and pyridine, and carbonate solvents such as diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, and propylene carbonate. Among these, ketone solvents such as methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), diisobutyl ketone, 3,5,5-trimethylcyclohexanone, diacetone alcohol, and cyclopentanone are preferred.

[0070] Examples of methods that can be used for applying the coating composition containing the first material and the second material include various application methods such as spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, flexographic printing, offset printing, and inkjet printing.

[0071] After the coating composition is applied in this manner, it is preferable to carry out an annealing treatment. The annealing treatment is preferably carried out at 70 to 200°C for 0.1 to 5 hours in a nitrogen atmosphere or in the air. By carrying out such an annealing treatment, the solvent can be evaporated to form an organic thin film.

[0072] In addition, since the hexahydropyrimidopyrimidine compound, which is the first material represented by the above general formula (1), has extremely excellent electron injection properties, an organic thin film containing the first material but not the second material is also useful as a material for an organic EL device, etc. A method for producing an organic thin film including a step of forming a film containing a hexahydropyrimidopyrimidine compound having a structure represented by general formula (1) on a surface to be formed is also one aspect of the present invention, and including a step of forming a film containing a hexahydropyrimidopyrimidine compound having a structure represented by general formula (1) on a surface to be formed that contains a second material is one of the preferred embodiments of the method for producing an organic thin film.

[0073] "Organic EL element" The present invention also relates to an organic electroluminescence (EL) device having a light-emitting layer between a cathode and an anode, and further comprising any one of a layer of the organic thin film of the present invention, a layer of a laminate film of the organic thin film layer and a metal oxide layer, or a layer containing the material for organic electroluminescence devices of the present invention. The organic thin film layer, the laminated film layer of the organic thin film layer and a metal oxide layer, and the layer containing the material for an organic electroluminescence device of the present invention may be located between the cathode and the light-emitting layer or between the anode and the light-emitting layer in the organic EL device of the present invention, but is preferably located between the cathode and the light-emitting layer. In addition, the layer containing the material for organic electroluminescence devices of the present invention may contain other components as long as it contains a hexahydropyrimidopyrimidine compound having a structure represented by the above-mentioned general formula (1), but it is preferable that the layer is composed only of a hexahydropyrimidopyrimidine compound.

[0074] The present invention also relates to an organic electroluminescence (EL) element having a light-emitting layer between a cathode and an anode, which includes a layer of the organic thin film of the present invention or a layer of a laminate film of the organic thin film and a metal oxide layer between the cathode and the anode, and the light-emitting layer includes a second material.The present invention also relates to an organic electroluminescence (EL) element including a layer of the organic thin film of the present invention or a layer of a laminate film of the organic thin film and a metal oxide layer between the cathode and the anode, in which the organic thin film or the laminate film is adjacent to the light-emitting layer and includes a material used in the light-emitting layer as the second material, or the film including the second material among the organic thin film or the laminate film is the light-emitting layer. The hexahydropyrimidopyrimidine compound, which is the first material of the present invention, has extremely excellent electron injection properties, and is therefore capable of directly injecting electrons into the light-emitting material and host material used in the light-emitting layer. Therefore, by using the first material of the present invention in the electron injection layer, it is possible to reduce the number of materials used and the number of layers to be laminated, thereby making it possible to provide an organic EL device with a simpler structure. That is, when the element using the organic thin film or laminated film of the present invention is an element in which a layer containing a first material, a layer containing a second material, and a light-emitting layer are adjacent to each other, and even when the light-emitting material or host material used in the light-emitting layer is used as the material of the layer containing the second material, it is possible to inject electrons from the layer containing the first material, and in this way, the layer containing the second material and the light-emitting layer can be formed using a common material, so that the number of materials used can be reduced. In this case, the second material may be either a light-emitting material or a host material of the light-emitting layer. In addition, when the layer containing the second material is formed using a light-emitting material or a host material of the light-emitting layer and used as the light-emitting layer, it becomes unnecessary to provide a separate light-emitting layer, so that it is possible to reduce the number of layers to be laminated and to obtain an organic EL element with a simpler structure. Furthermore, if the second material is used as the material of the layer adjacent to the anode side of the light-emitting layer, it is possible to further reduce the number of layers to be laminated and to obtain an organic EL element with a simpler structure. Therefore, the light-emitting layer containing the second material and the layer containing the second material between the anode and the light-emitting layer are both preferred embodiments of the organic electroluminescence (EL) element of the present invention.

[0075] Next, the organic EL device of the present invention will be described in detail with reference to examples. Fig. 1 is a schematic cross-sectional view for explaining one example of the organic EL element of the present invention. The organic EL element 1 of the present invention shown in Fig. 1 has an emitting layer 6 between a cathode 3 and an anode 9. The organic EL element 1 shown in Fig. 1 has an electron injection layer 5 made of the organic thin film of the present invention or the material for organic electroluminescence devices of the present invention between the cathode 3 and the emitting layer 6. In addition, an oxide layer 4 is provided between the cathode 3 and the electron injection layer 5 made of the organic thin film of the present invention or the material for organic electroluminescence devices of the present invention, and the oxide layer 4 is adjacent to the electron injection layer 5. All of these are suitable embodiments of the organic EL element of the present invention. The organic EL device 1 of the present invention has a laminated structure in which a cathode 3, an inorganic oxide layer 4, an electron injection layer 5, an electron transport layer 10, 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. In this manner, having an inorganic oxide layer between the cathode and the layer of the organic thin film or the layer of the material for organic electroluminescence devices of the present invention is one of the preferred embodiments of the organic EL device of the present invention.

[0076] The organic EL element 1 shown in Fig. 1 is an organic EL element having an inverted structure in which a cathode 3 is disposed between a substrate 2 and a light-emitting layer 6. The organic EL element 1 shown in Fig. 1 is an organic-inorganic hybrid organic electroluminescent element (HOILED element) in which a part of the layers constituting the organic EL element (at least the inorganic oxide layer 4) is formed using an inorganic compound. The organic EL element 1 shown in FIG. 1 may be of a top emission type in which light is extracted from the side opposite to the substrate 2, or of a bottom emission type in which light is extracted from the substrate 2 side.

[0077] FIG. 2 is a diagram showing an example of the device configuration when the organic EL device of the present invention is an organic EL device having a forward structure in which a light-emitting layer 6 is disposed between a substrate 2 and a cathode 3. In FIG. As described above, the hexahydropyrimidopyrimidine compound of the present invention has an extremely excellent electron injection property, and therefore can directly inject electrons into the material used in the light-emitting layer. Therefore, when using a material for an organic EL device containing the hexahydropyrimidopyrimidine compound of the present invention, even when an organic EL device having a simple structure is formed by forming an electron transport layer 10 from a material used in the light-emitting layer and using the same material for the light-emitting layer 6 and the electron transport layer 10 as shown in FIG. 3, it is possible to operate at a low driving voltage by using the hexahydropyrimidopyrimidine compound in the electron injection layer 5. In this case, it is possible to reduce the number of materials used compared to a typical organic EL device. Here, if the electron transport layer 10 contains the second material of the present invention, it can be said that the organic EL device uses the organic thin film of the present invention. Furthermore, since holes can be relatively easily injected from the hole injection layer 8 into the material used in the light emitting layer, when the material for an organic EL device containing the hexahydropyrimidopyrimidine compound of the present invention is used in the electron injection layer 5, the device can operate at a low driving voltage even if the material used in the light emitting layer is used in the hole transport layer 7, as shown in FIG. 4. In this case, it is possible to reduce the number of materials used by at least two compared to a typical organic EL device. Here, if the electron transport layer 10 contains the second material of the present invention, it can be said that the organic EL device uses the organic thin film of the present invention. Although the organic EL element having a forward structure has been described here, the organic EL element of the present invention in which the light-emitting layer contains the second material is not limited to the forward structure, and may have an inverted structure.

[0078] In the following embodiment, an organic EL element having an inverted structure will be described as an example, but the organic EL element of the present invention may have a forward structure in which an anode is disposed between a substrate and an emitting layer. When the organic EL element of the present invention has a forward structure, the organic thin film is disposed between a cathode and an emitting layer, as in the case of an inverted structure. In the case of an inverted structure, the electron injection layer is sometimes called an organic buffer layer. All of the contents described below can be applied to an organic EL element having a forward structure.

[0079] "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 the glass material used for the substrate 2 include quartz glass and soda glass.

[0080] 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.

[0081] 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.

[0082] "cathode" The cathode 3 is formed on and in direct contact with the substrate 2 . The material of the cathode 3 is ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), In 3 O 3 , SnO 2 , Sb-containing SnO 2 Examples of the conductive material include oxides such as Al-containing ZnO, and conductive materials such as Al, Au, Pt, Ag, Cu, and alloys containing these. 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, spectroscopic ellipsometry, or a quartz crystal film thickness gauge.

[0083] "Oxide layer" The inorganic oxide layer 4 functions as an electron injection layer and / or a cathode. The oxide layer 4 is a semiconductor or insulator laminated thin film layer. Specifically, the oxide layer 4 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. Metal elements constituting the metal oxide that forms the oxide layer 4 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.

[0084] When the oxide layer 4 includes a layer containing a mixture of two or more types of metal oxides, it is preferable that at least one of the metal elements constituting the metal oxide is magnesium, aluminum, calcium, zirconium, hafnium, silicon, titanium, or zinc. When the oxide layer 4 is a layer made of a simple metal oxide, it is preferably a layer 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.

[0085] When the oxide layer 4 is a layer obtained by laminating either or both of a layer 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 laminating two or more kinds of metal oxides, examples of the oxide layer 4 include a layer obtained by laminating and / or mixing a combination 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 obtained by laminating and / or mixing a combination 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.

[0086] The oxide layer 4 is made of IGZO (indium gallium zinc oxide), an oxide semiconductor that exhibits excellent properties due to its special composition, and / or 12CaO 7Al 2 O 3 It may include. The average thickness of the oxide layer 4 is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 2 to 100 nm. The average thickness of the oxide layer 4 can be measured by a stylus step gauge or spectroscopic ellipsometry.

[0087] "Electron injection layer" The electron injection layer 5 serves to improve the speed and electron transport properties of the electron injection from the cathode to the light emitting layer 6. The electron injection layer 5 is made of the above-mentioned organic thin film. The average thickness of the electron injection layer 5 is preferably 0.5 to 100 nm, more preferably 1 to 100 nm, even more preferably 5 to 100 nm, and particularly preferably 10 to 50 nm. When the average thickness of the electron injection layer 5 is 0.5 nm or more, the electron injection layer 5 can be formed by using any of the following methods: a method of applying a coating composition containing the first material and the second material; a method of applying a coating composition containing the first material and a coating composition containing the second material in sequence; or a method of forming a laminate film of the first material and the second material, respectively. This allows the electron injection layer 5 to have a smooth surface, and leakage during the manufacture of the organic EL element 1 to be sufficiently prevented. In addition, when the average thickness of the electron injection layer 5 is 100 nm or less, the increase in the driving voltage of the organic EL element 1 due to the provision of the electron injection layer 5 can be sufficiently suppressed. In addition, the electron injection layer 5 may be formed by vapor deposition. A method of simultaneously vapor depositing the first material and the second material, or a method of vapor depositing one of the first material and the second material and then vapor depositing the other can be used. In addition, when forming a film containing the first material and the second material, any of the structures shown in Figures 5-1 to 11-1 (Figures 5-2 to 11-2 in the case of a normal structure) may be used. For example, the film may be made of one layer, and the entire film may constitute the electron injection layer (Figures 5-1 and 5-2), or one of the film made of only the first material and the film made of only the second material may be formed adjacent to the cathode or oxide, and the other film may be formed adjacent to that film (Figures 6-1, 6-2, Figures 7-1 and 7-2). In addition, a film containing the first material and the second material may be formed adjacent to the cathode or oxide, and a film made of only the second material may be formed adjacent to that film (Figures 8-1 and 8-2), or a film made of only the second material, not including the first material, may be formed adjacent to the cathode or oxide, and a film containing the first material and the second material may be formed adjacent to that film (Figures 9-1 and 9-2). Furthermore, a film consisting of only the first material or a film containing the first material and the second material may be formed into a three-layer structure (FIGS. 10-1, 10-2, 11-1, 11-2) in which the film is sandwiched between films consisting of only the second material. Any of the structures shown in FIGS. 5-1 to 11-1 and 5-2 to 11-2 is included in the present invention. In addition, as shown in FIGS. 8-1 to 11-1 and 8-2 to 11-2, when the second material is contained in both of two adjacent films or in two or more films of a three-layer structure film, the second materials contained in these two or more films may be the same or different. In addition, for the structures of FIGS. 6-1, 6-2, 7-1, 7-2, and 10-1, 10-2, which include a layer consisting of only the first material, the layer consisting of only the first material can also be considered as a layer formed from the organic thin film of the present invention (an organic thin film containing only the first material and not containing the second material). The average thickness of the electron injection layer 5 can be measured by, for example, a stylus step gauge or spectroscopic ellipsometry.

[0088] As described above, the first material, which is an organic material with a pKa of 1 or more, receives protons (H +), when the organic thin film of the present invention is formed adjacent to the oxide layer 4, it is preferable that the first material is present in a larger amount on the oxide layer 4 side in order to sufficiently promote electron injection from the oxide layer 4. Therefore, it is preferable that the electron injection layer 5 has a concentration distribution in which the concentration of the first material decreases from the oxide layer 4 side toward the electron transport layer 10 side. In an organic electroluminescent device having an inverted structure, a method for forming an electron injection layer having such a concentration distribution includes a method in which a solution containing a first material is applied onto the oxide layer 4 to form a coating film, and then a solution containing a second material is applied onto the coating film of the first material. However, the method is not limited to this process as long as the concentration distribution can be formed. Similarly, when the organic thin film of the present invention is formed adjacent to the cathode 3, it is preferable that the first material is present in a larger amount on the cathode 3 side in order to sufficiently promote electron injection from the cathode 3. Therefore, it is preferable that the electron injection layer 5 has a concentration distribution in which the concentration of the first material decreases from the cathode 3 side toward the electron transport layer 10 side. In a forward-structure organic EL element, a method for forming an electron injection layer having such a concentration distribution can be mentioned, for example, by applying a solution containing the second material onto the electron transport layer 10 to form a coating film, and then applying a solution containing the first material onto the coating film of the second material. However, the method is not limited to this process as long as the concentration distribution can be formed. The concentration distribution can be measured by TOF-SIMS (time-of-flight secondary ion mass spectrometry) or the like.

[0089] In addition to forming an electron injection layer having the above-mentioned concentration distribution, in the case of an organic EL element having an inverted structure, a layer of the first material may be formed on the oxide layer 4, and a layer containing the first material and the second material may be formed thereon. In the case of an organic EL element having a normal structure, a layer of the second material may be formed on the electron transport layer 10, and a layer containing the first material and the second material may be formed thereon. In this case, these layers can be formed by either coating or vapor deposition.

[0090] As described above, the first material, which is an organic material with a pKa of 1 or more, receives protons (H + ), and it is a material that has the ability to extract oxygen and water, which are suitably coordinated to the defective sites of an inorganic compound (oxide) and prevent reactions at the interface with oxygen and water that enter from the outside. The organic thin film of the present invention can be effective even if it is not formed adjacent to the cathode or the oxide layer, but in order to fully exert the effect of the organic thin film of the present invention, it is preferable that the organic thin film of the present invention forms a layer adjacent to the cathode or the oxide layer. The laminated structure film thus obtained, i.e., a laminated film consisting of an oxide layer and a layer of the organic thin film of the present invention formed adjacent to the oxide layer, and a laminated film consisting of a cathode and a layer of the organic thin film of the present invention formed adjacent to the cathode, are also one aspect of the present invention. When an organic EL element includes an oxide layer and a layer of the organic thin film of the present invention formed adjacent to the oxide layer between a cathode and a light-emitting layer in a laminate structure, or when an organic EL element includes a cathode and a layer of the organic thin film of the present invention formed adjacent to the cathode, the organic EL element can be said to be configured to include the organic thin film of the present invention, or to be configured to include the laminate film of the present invention. An organic EL element including the organic thin film or laminate film of the present invention between such a cathode and a light-emitting layer is also one aspect of the present invention. Furthermore, an organic EL element including the organic thin film of the present invention, or a laminate film including a cathode and a layer of the organic thin film of the present invention formed adjacent to the cathode is also one aspect of the present invention.

[0091] The organic EL element of the present invention may have a laminated film as shown in Figures 8-1, 8-2, 9-1, 9-2, or 11-1, 11-2 as an electron injection layer. That is, having a laminated film of a film containing the first material and the second material and a film containing the second material between the cathode and the light-emitting layer is one of the preferred embodiments of the organic EL element of the present invention. In this case, either an organic EL element having a layer containing the second material between the light-emitting layer and the film containing the first material and the second material, or an organic EL element having a layer containing the second material between the cathode and the film containing the first material and the second material, is one of the preferred embodiments of the organic EL element of the present invention.

[0092] "Electron transport material" The electron transport layer 10 may be made of any material that can be commonly used as a material for an electron transport layer. Specifically, the material of the electron transport layer 10 is phenyl-dipyrenylphosphine oxide (POPy 2 ), 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, phenanthroline derivatives such as bathophenanthroline (BPhen), and 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT). triazine derivatives, 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), imidazole derivatives such as 2,2',2''-(1,3,5-benzotriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic ring tetracarboxylic anhydrides such as naphthalene and perylene, bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ) 2 ), various metal complexes represented by tris(8-hydroxyquinolinato)aluminum (Alq3), and the like; organic silane derivatives represented by silole derivatives such as 2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy); and boron-containing compounds described in Japanese Patent Application No. 2012-228460, Japanese Patent Application No. 2015-503053, Japanese Patent Application No. 2015-053872, Japanese Patent Application No. 2015-081108, and Japanese Patent Application No. 2015-081109, and the like. One or more of these can be used. Among these materials for the electron transport layer 10, POPy2 Phosphine oxide derivatives such as Alq 3 It is preferable to use a metal complex such as the following, or a pyridine derivative such as TmPhPyB. As in the case of an organic EL element in which a layer containing the above-mentioned second material is formed using the light-emitting material or host material used in the light-emitting layer, the organic EL element of the present invention does not need to have an electron-transport layer using the above-mentioned electron-transport material in the laminate structure as long as the organic EL element exhibits its function.

[0093] The average thickness of the electron transport layer 10 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 10 can be measured by a stylus step gauge or spectroscopic ellipsometry.

[0094] "Light-emitting layer" The material for forming the light-emitting layer 6 may be any material that can be commonly 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 be made of bis[2-(2-benzothiazolyl)phenolato]zinc(II) (Zn(BTZ) 2 ) and tris[1-phenylisoquinoline]iridium(III) (Ir(piq) 3 ) may be included. 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.

[0095] Examples of the polymeric material for forming the light-emitting layer 6 include polyacetylene 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-dimethylphenylacetylene) (PDPA), poly(di ... poly(p-phenylene vinylene)-based compounds such as poly(2-methoxy,5-(2'-ethylhexoxy)-p-phenylene vinylene) (MEH-PPV); polythiophene-based compounds such as poly(3-alkylthiophene) (PAT) and poly(oxypropylene) triol (POPT); poly(9,9-dialkylfluorene) (PDAF), poly(dioctylfluorene) -alto-benzothiadiazole) (F8BT), 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- ... Examples of such compounds include polyparaphenylene compounds such as poly(paraphenylene) (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-based polymer materials described in Japanese Patent Application Nos. 2010-230995 and 2011-6457.

[0096] 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, and factorys(2-phenylpyridine)iridium (Ir(ppy) 3), fac-tris(3-methyl-2-phenylpyridinato-N,C2'-)iridium(III) (Ir(mppy) 3 ), 8-hydroxyquinoline aluminum (Alq 3 ), tris(4-methyl-8-quinolinolato)aluminum(III) (Almq 3 ), 8-hydroxyquinoline zinc (Znq 2 ), (1,10-phenanthroline)-tris-(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dionate) europium(III) (Eu(TTA) 3(phen)), various metal complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II); 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-based compounds such as chrysene and 6-nitrochrysene; perylene, N,N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-dicarboximide ( perylene compounds such as BPPC; coronene compounds such as coronene; anthracene compounds such as anthracene, bisstyrylanthracene, and (9,10-bis(4-(9H-carbazol-9-yl)-2,6-dimethylphenyl))-9,10-diboraanthracene (CzDBA) represented by formula (27) below; pyrene compounds such as pyrene; pyran compounds such as 4-(dicyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM); acridine compounds such as acridine; stilbe thiophene compounds such as 2,5-dibenzoxazolethiophene;benzoxazole compounds such as benzoxazole;benzoimidazole compounds such as benzimidazole;benzothiazole compounds such as 2,2'-(para-phenylenedivinylene)-bisbenzothiazole;butadiene compounds such as bistyryl(1,4-diphenyl-1,3-butadiene), tetraphenylbutadiene;naphthalimide compounds such as naphthalimide;coumarin compounds such as coumarin;perinones perinone compounds such as 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; triazine compounds such as 2,4-diphenyl-6-bis((12-phenylindolo)[2,3-a]carbazol-11-yl)-1,3,5-triazine (DIC-TRZ);Spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene; phthalocyanine (H; 2 Pc), metallic or non-metallic phthalocyanine compounds such as copper phthalocyanine; and further boron compound materials described in JP-A-2009-155325, JP-A-2011-184430 and Japanese Patent Application No. 2011-6458. Examples of the host material for the light-emitting layer include carbazole compounds such as 4,4'-bis(9H-carbazol-9-yl)biphenyl (CPB); silicon compounds; phenanthroline compounds; and triphenylene compounds.

[0097] 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.

[0098] "Hole transport layer" As the hole transporting organic material used in the hole transport layer 7, various p-type polymeric materials (organic polymers) and various p-type low molecular weight materials can be used alone or in combination. Specifically, examples of the material for the hole transport layer 7 include N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), N4,N4'-bis(dibenzo[b,d]thiophen-4-yl)-N4,N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), N3,N3'''-bis(dibenzo[b,d]thiophen-4-yl)-N3,N3'''-diphenyl-[1,1':2',1'':2'',1'''-quaternary Examples of the material for the hole transport layer 7 include poly(phenyl)-3,3'''-diamine (4DBTP3Q), polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly(N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly(p-phenylenevinylene), polytinylenevinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin or derivatives thereof. These materials for the hole transport layer 7 can also be used as a mixture with other compounds. As an example, a mixture containing polythiophene used as a material for the hole transport layer 7 includes poly(3,4-ethylenedioxythiophene / styrenesulfonic acid) (PEDOT / PSS), etc. As described above, since holes can be relatively easily injected from the hole injection layer into the material used in the light emitting layer, the organic EL device of the present invention can operate at a low driving voltage even if the material used in the light emitting layer is used in the hole transport layer. Therefore, the organic EL device of the present invention does not need to have a hole transport layer using the hole transport material as described above.

[0099] 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.

[0100] "Hole injection layer" The positive hole injection layer 8 may be made of an inorganic material or an organic material. Since inorganic materials are more stable than organic materials, high resistance to oxygen and water is more easily obtained compared to the case where an organic material is used. The inorganic material is not particularly limited. For example, vanadium(V) oxide 2 O 5 ), molybdenum(VI) oxide (MoO 3 ), ruthenium(IV) oxide (RuO 2 ), or the like, and one or more metal oxides can be used. As the organic material, 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), fullerene, the positive hole injection material "Clevios HIL1.3N" manufactured by Heraeus, or the like can be used.

[0101] The average thickness of the positive 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 positive hole injection layer 8 can be measured during film formation using a quartz crystal oscillator thickness meter or a stylus type step meter.

[0102] "Anode" Examples of the material used for the anode 9 include ITO, IZO, Au, Pt, Ag, Cu, Al, or an alloy 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. Further, even when a material that is impermeable as the material for the anode 9 is used, for example, by setting the average thickness to about 10 to 30 nm, it can be used as a transparent anode in a top emission type organic EL element. The average thickness of the anode 9 can be measured during film formation of the anode 9 using a quartz crystal oscillator thickness meter.

[0103] "Sealing" The organic EL element 1 shown in FIG. 1 may be sealed, if necessary. For example, the organic EL element 1 shown in Fig. 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. Alternatively, for example, the organic EL element 1 shown in Fig. 1 may be sealed by using a sealing member made of a plate member (not shown) arranged on the anode 9 and a frame member (not shown) arranged along the edge of the plate member on the side facing the anode 9, and an adhesive for bonding between the plate member and the frame member and between the frame member and the substrate 2.

[0104] 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.

[0105] A resin material, a glass material, etc. can be used as a material for a sealing container or a sealing member used to seal the organic EL element 1 shown in Fig. 1. Examples of the resin material and the glass material used for the sealing container or the sealing member include the same materials as those used for the substrate 2.

[0106] In the organic EL device 1 of this embodiment, when an electron injection layer is formed using an organic thin film made of a first material made of a hexahydropyrimidopyrimidine compound having a structure represented by the above general formula (1) and a second material made of a boron-containing compound represented by the above general formula (4), excellent durability can be obtained compared to, for example, a case in which an alkali metal, which is an unstable material in the atmosphere, is used as the electron injection layer. Therefore, when the water vapor transmission rate of the sealing container or sealing member is 10 -4 ~10 -3 Order (g / m 2 / day), deterioration of the organic EL element 1 can be sufficiently suppressed. -3 Order (g / m 2 It is possible to use a resin material with a thermal expansion coefficient of about 100 / day or less, and thus it is possible to realize an organic EL element 1 with excellent flexibility.

[0107] "Manufacturing method for organic EL elements" Next, as an example of a method for producing the organic EL element of the present invention, a method for producing the organic EL element 1 shown in FIG. 1 will be described. To manufacture the organic EL element 1 shown in FIG. 1, first, a cathode 3 is formed on a 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.

[0108] Next, an inorganic oxide layer 4 is formed on the cathode 3 . The oxide layer 4 is formed by using, for example, a spray pyrolysis method, a sol-gel method, a sputtering method, a vacuum deposition method, etc. The surface of the oxide layer 4 thus formed may not be smooth but may have projections and recesses.

[0109] Next, the electron injection layer 5 is formed on the oxide layer 4 . The electron injection layer 5 can be formed by the above-mentioned method for producing an organic thin film.

[0110] Next, on the electron injection layer 5, the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7 are formed in this order. The methods for forming the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7 are not particularly limited, and various conventionally known formation methods can be used appropriately in accordance with the characteristics of the materials used for the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7, respectively.

[0111] Specifically, methods for forming the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7 include a coating method for coating an organic compound solution containing an organic compound that will become the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7, a vacuum deposition method, and an ESDUS (Evaporative Spray Deposition from Ultra-dilute Solution) method. Among these methods for forming the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7, it is particularly preferable to use the coating method. Note that when the organic compounds that will become the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7 have low solvent solubility, it is preferable to use the vacuum deposition method or the ESDUS method.

[0112] When forming the electron transport layer 10, the light-emitting layer 6, and the hole transport layer 7 using a coating method, the organic compounds that will become the electron transport layer 10, the light-emitting layer 6, and the hole transport layer 7 are dissolved in a solvent, respectively, to form organic compound solutions containing the organic compounds that will become the electron transport layer 10, the light-emitting layer 6, and the hole transport layer 7, respectively.

[0113] As the solvent used for dissolving the organic compounds to be the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7, for example, aromatic hydrocarbon solvents such as xylene, toluene, cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene, and tetramethylbenzene; aromatic heterocyclic compound solvents such as pyridine, pyrazine, furan, pyrrole, thiophene, and methylpyrrolidone; and aliphatic hydrocarbon solvents such as hexane, pentane, heptane, and cyclohexane are preferable, and these can be used alone or in combination.

[0114] As a method for applying an organic compound solution containing an organic compound that will become the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7, various application methods can be used, such as spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, flexographic printing, offset printing, and inkjet printing. Among these application methods, it is preferable to use spin coating or slit coating, since it is easier to control the film thickness.

[0115] Next, the hole injection layer 8 and the anode 9 are formed in this order on the hole transport layer 7. When the hole injection layer 8 is made of an inorganic material, the hole injection layer 8 can be formed in the same manner as the oxide layer 4, for example. When the hole transport layer 9 is made of an organic material, the hole injection layer 8 can be formed in the same manner as the electron transport layer 10, the light emitting layer 6, and the hole transport layer 7, for example. The anode 9 can be formed, for example, in the same manner as the cathode 3 . By the above steps, the organic EL element 1 shown in FIG. 1 is obtained.

[0116] "Sealing method" When sealing the organic EL element 1 shown in FIG. 1, it can be sealed by using a method commonly used for sealing organic EL elements.

[0117] The organic EL device 1 of the present embodiment has an electron injection layer 5 made of an organic thin film containing the first material, which is an organic material having a pKa of 1 or more, and the second material that transports electrons. Therefore, the first material transports protons (H + ) is extracted, a negative charge is generated, and excellent electron injection properties are obtained. Therefore, the speed of electron injection and electron transport from the cathode 3 to the light-emitting layer 6 is high, and the organic EL device 1 has a low driving voltage. As described above, an organic EL element 1 in which an organic thin film containing a first material, which is an organic material having a pKa of 1 or more, and a second material that transports electrons is a laminated film, and the layer formed of the second material is a layer different from the electron injection layer formed of the first material, is also another embodiment of the organic EL element of the present invention. In the organic EL element of such an embodiment, the speed of electron injection and electron transport from the cathode 3 to the light-emitting layer 6 is high, and the organic EL element 1 has a low driving voltage.

[0118] "Other examples" The organic EL element of the present invention is not limited to the organic EL element described in the above-mentioned embodiment. Specifically, in the above-mentioned embodiment, the organic thin film functions as an electron injection layer, but the organic EL element of the present invention may have an organic thin film between the cathode and the light-emitting layer. Therefore, the organic thin film is not limited to the electron injection layer, and may be provided as a layer that functions both as the electron injection layer and the electron transport layer, or may be provided as the electron transport layer.

[0119] In the organic EL element 1 shown in FIG. 1, the inorganic oxide layer 4, the electron transport layer 10, the hole transport layer 7, and the hole injection layer 8 may be formed as necessary, and may not be provided. In addition, each of the cathode 3, the oxide layer 4, the electron injection layer 5, the electron transport layer 10, the light emitting layer 6, the hole transport layer 7, the hole injection layer 8, and the anode 9 may be formed as a single layer or may be formed as two or more layers.

[0120] In addition, the organic EL element 1 shown in Fig. 1 may have other layers between the layers shown in Fig. 1. Specifically, for the purpose of further improving the characteristics of the organic EL element, an electron blocking layer or the like may be provided as necessary.

[0121] In addition, in the above-described embodiment, an organic EL element having an inverted structure in which the cathode 3 is disposed between the substrate 2 and the light-emitting layer 6 has been described as an example, but the organic EL element may have a normal structure in which an anode is disposed between the substrate and the light-emitting layer.

[0122] "Display devices, lighting devices, organic thin-film solar cells, photoelectric conversion elements, thin-film transistors" 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, it can be suitably used as a light-emitting portion of a display device or a lighting device.

[0123] The display device of the present invention includes the organic EL element of the present invention, which has an organic thin film between the cathode and the light-emitting layer, has excellent productivity, and has a low driving voltage, and is therefore preferable as a display device. Furthermore, the lighting device of the present invention has excellent productivity and includes the organic EL element of the present invention, which has a low driving voltage, and is therefore preferable as a lighting device.

[0124] The present invention is not limited to the above-described embodiment, and the organic thin film of the present invention can be used in devices such as organic thin film solar cells, photoelectric conversion elements, and thin film transistors. The organic thin-film solar cell and photoelectric conversion element of the present invention include an organic thin-film. For example, when the organic thin-film is used as an electron injection layer of an organic thin-film solar cell or a photoelectric conversion element, the first material of the organic thin-film absorbs protons (H + ) is extracted, a negative charge is generated, so that the electron transport speed is fast and high power generation efficiency can be obtained. Therefore, an organic thin-film solar cell or a photoelectric conversion element including the organic thin-film of the present invention is preferable as an organic thin-film solar cell or a photoelectric conversion element. The thin film transistor of the present invention also includes an organic thin film. For example, when the channel layer of the thin film transistor is formed of an organic thin film, a channel layer with high electron mobility can be obtained. Furthermore, when the organic thin film is formed on an electrode, a reduction in contact resistance can be expected. Thus, the organic thin film of the present invention is suitable as a material for organic thin film solar cells, photoelectric conversion elements, and thin film transistors, and therefore the hexahydropyrimidopyrimidine compound having the structure represented by the above general formula (1) constituting the organic thin film is also suitable as a material for these. Such a material for organic thin film solar cells, a material for photoelectric conversion elements, and a material for thin film transistors, which contains the hexahydropyrimidopyrimidine compound having the structure represented by the above general formula (1), also constitutes one aspect of the present invention. EXAMPLES

[0125] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, "parts" means "parts by weight" and "%" means "mol %".

[0126] Synthesis Example 1 The compound of the following formula (2-9) was synthesized by the method described in Macromolecules, 45(5), p.2249-2256, 2012.

[0127] [ka]

[0128] Synthesis Example 2 In a 200mL three-neck flask, rac-BINAP (747mg) and toluene (67mL) were placed and heated to 90℃ under a nitrogen atmosphere to dissolve. After cooling to room temperature, palladium acetate (180mg) was added and stirred at room temperature for 1 hour. 2,6-dibromopyridine (4.74g), 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (6.13g), and KOtBu (6.28g) were added and heated and stirred at 90℃ overnight. 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 of the following formula (2-2) (3.7g, 52.5%).

[0129] [ka]

[0130] Synthesis Example 3 In a 300 mL three-neck flask, rac-BINAP (369 mg) was added to toluene (100 mL) at room temperature under a nitrogen stream, and the mixture was heated and stirred in an oil bath at 60°C until the solid was dissolved. 2(98 mg), 6-bromo-2,2'-bipyridine (5.00 g) were added and stirred again at 60 ° C oil bath for 20 minutes. 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (3.26 g) and KOtBu (5.97 g) were added to the mixture, which was returned to room temperature, and stirred at 90 ° C oil bath for 3 hours. Diethyl ether was added to the mixture, which was returned to room temperature, and insoluble matter was filtered off. The filtrate was concentrated under reduced pressure, and ethyl acetate (15 mL) was added to the residue. The mixture was ultrasonically treated to obtain a solid, which was filtered and dried under reduced pressure overnight. The obtained solid was recrystallized in ethyl acetate and then distilled to obtain the compound of the following formula (2-3) (1.20 g, 19.2%) as a white solid.

[0131] [ka]

[0132] Synthesis Example 4 In a three-neck flask, rac-BINAP (357 mg) was added to toluene (97 mL) at room temperature under a nitrogen stream, and the mixture was heated and stirred in an oil bath at 60°C until the solid was dissolved. Palladium acetate (86 mg) and 2-bromo-1,10-phenanthroline (4.40 g) were added to the mixture, which was returned to room temperature, and the mixture was stirred again in an oil bath at 60°C for 30 minutes. 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (2.64 g) and KOtBu (4.72 g) were added to the mixture, which was returned to room temperature, and the mixture was stirred in an oil bath at 90°C for 4 hours. Diethyl ether (150 mL) was added to the mixture, which was returned to room temperature, and the insoluble matter was filtered off. The filtrate was concentrated under reduced pressure, and ethyl acetate (20 mL) was added to the residue. The precipitate was collected by filtration and dried under reduced pressure. Acetone (100 mL) was added to the solid, which was washed by heating, and the solid was collected by filtration. The obtained solid was purified by sublimation to obtain a compound of the following formula (2-4) (2.21 g, 25.6%) as a white solid.

[0133] [ka]

[0134] Synthesis Example 5 In a flask, rac-BINAP (301 mg) was added to toluene (80 mL) at room temperature under a nitrogen stream, and the mixture was heated and stirred in an oil bath at 60°C until the solid was dissolved. Palladium acetate (78 mg) and 6,6'-dibromo-2,2'-bipyridine (5.00 g) were added to the mixture, which was returned to room temperature, and the mixture was stirred again in an oil bath at 60°C for 20 minutes. 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (4.90 g) and KOtBu (8.95 g) were added to the mixture, which was returned to room temperature, and the mixture was stirred in an oil bath at 110°C for 6 hours. Diethyl ether was added to the mixture, which was returned to room temperature, and the insoluble matter was filtered off. The insoluble matter was rinsed with a chloroform-ethyl acetate mixed solvent, and the combined filtrate was concentrated under reduced pressure. Methanol was added to the residue, and the precipitate was collected by filtration. The solid (3.60 g) was washed with methanol (50 mL) and cooled to room temperature, and the precipitated solid was collected by filtration again. The solid (2.20 g) was purified by sublimation to obtain the compound of the following formula (2-5) (1.45 g, 21.0%) as a white solid.

[0135] [ka]

[0136] Synthesis Example 6 In a recovery flask, 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (5.72g) was added to a mixture of 2-chloro-4,6-diphenyl-1,3,5-triazine (5.00g) and toluene (95mL) at room temperature, and the mixture was stirred in an oil bath at 100°C for 3 hours. Insoluble matter was filtered off from the mixture, which had been returned to room temperature, and the filtrate was concentrated under reduced pressure. Chloroform (25mL) was added to the residue, and the mixture was subjected to ultrasonic treatment to precipitate a solid, which was then filtered and dried under reduced pressure to obtain the compound of the following formula (2-6) (5.90g, 85.2%) as a white solid.

[0137] [ka]

[0138] Synthesis Example 7 In a 100mL reaction vessel, rac-BINAP (0.213g, 0.342mmol) and toluene (20mL) were placed, heated to 70℃, and completely dissolved. Palladium acetate (51mg, 0.228mmol) was added, and the mixture was stirred while cooling to room temperature. 2,4,6-tribromopyridine (1.2g, 3.8mmol), KOtBu (1.8g, 16.0mmol), and 1,3,4,6,7,8-hexahydro2H-pyrimido[1,2-a]pyrimidine (1.9g, 13.7mmol) were added, and the mixture was heated and stirred at 100℃ for 14 hours. After cooling to room temperature, the reaction solution was filtered through Celite, and the filtrate was concentrated to obtain 2.2g of the compound of the following formula (2-11).

[0139] [ka]

[0140] Synthesis Example 8 In a 200 mL eggplant flask, rac-BINAP (0.238 g, 0.383 mmol) and dehydrated toluene (55 mL) were placed and dissolved by heating at 90 ° C. This was cooled to room temperature, palladium acetate (0.054 g, 0.24 mmol) was added, and the inside of the reaction vessel was replaced with argon. After 1 hour, 2-bromo-9,9'-spirobi[9H-fluorene] (2.18 g, 5.52 mmol), 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (0.957 g, 6.88 mmol), and potassium tert-butoxide (0.936 g, 8.35 mmol) were added, and the inside of the reaction vessel was replaced with argon again, and then the reaction vessel was heated and stirred in an oil bath at 90 ° C. After 2.25 hours, the mixture was cooled to room temperature, diethyl ether (220 mL) was added, and the mixture was stirred for a while. The precipitated solid was then suction filtered and washed with diethyl ether. The diethyl ether in the filtrate was distilled off under reduced pressure, and the remaining toluene layer was washed with water (55 mL). The organic layer was distilled off under reduced pressure, and the residue was purified by silica gel column chromatography to obtain 2.13 g (4.69 mmol, yield 85%) of the compound of the following formula (2-30). 2.31 g of the compound of the following formula (2-30), which was combined with one that had been synthesized separately, was dissolved in chloroform, and the solvent was removed under reduced pressure. The residue was then suspended in hexane (50 mL) and stirred for 30 minutes. The solid was then suction filtered and washed with hexane to obtain 1.78 g of the compound of the following formula (2-30) with a purity of 99.2%. The obtained compound 1 The H-NMR measurement results are as follows: 1 H-NMR (500 MHz CDCl 3 ):δ7.81(d,2H,J=7.5Hz),7.74(t,2H,J=8.0Hz),7.41(dd,1H,J=1.5,8.5Hz),7.36-7.29 (m,3H),7.09(t,2H,J=8.0Hz),7.03(t,1H,J=7.5Hz),6.76(d,1H,J=7.5Hz),6.66(d,1H, J=1.5Hz),6.44(d,1H,J=1.5Hz),3.32(t,2H,J=5.5Hz),3.26(t,2H,J=5.5Hz),3.14(t,2 H,J=6.0Hz),3.11(t,2H,J=6.5Hz),1.92(quin,2H,J=6.0Hz),1.80(quin,2H,J=6.0Hz).

[0141] [ka]

[0142] Synthesis Example 9 In a 100 mL eggplant flask, rac-BINAP (0.138 g, 0.221 mmol) and dehydrated toluene (35 mL) were placed and dissolved by heating at 90 ° C. This was cooled to room temperature, palladium acetate (0.0331, 0.148 mmol) was added, and the inside of the reaction vessel was replaced with argon. After 1 hour, 2,7-dibromo-9,9'-spirobi[9H-fluorene] (0.7 g, 1.48 mmol), 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (0.452 g, 3.25 mmol), and potassium tert-butoxide (0.431 g, 3.84 mmol) were added, and the inside of the reaction vessel was again replaced with an argon atmosphere, and then the reaction vessel was heated and stirred in an oil bath at 90 ° C. After 3.25 hours, the mixture was cooled to room temperature, diethyl ether (100 mL) was added, and the mixture was stirred for a while, after which the precipitated solid was suction filtered and washed with diethyl ether. The filtrate was back-extracted with water (35 mL), and the aqueous layer was distilled off under reduced pressure to obtain 1.09 g of a solid. This was suspended in acetone and stirred at room temperature for 2 hours, after which the solid was suction filtered and washed with acetone. This operation was repeated twice to obtain 0.520 g (0.88 mmol, 60% yield) of the compound of the following formula (2-31) as a pale yellow solid. The obtained compound 1 The H-NMR measurement results are as follows: 1 H-NMR (500 MHz CDCl 3 ):δ7.80(d,2H,J=8.0Hz),7.70(d,2H,J=8.0Hz),7.44(d,2H,J=6.5Hz),7.34(t,2H,J=7.5Hz),7.10(t,2H,J=7.5Hz),6.80(d,2H, J=7.5Hz),6.39(d,2H,J=1.5Hz),3.38-3.33(m,4H),3.28-3.25(m,4H),3.23-3.14(m,8H),1.98-1.93(m,4H),1.87-1.81(m,4H).

[0143] [ka]

[0144] Synthesis Example 10 In a 500 mL eggplant flask, rac-BINAP (1.21 g, 1.95 mmol) and dehydrated toluene (350 mL) were placed and heated to 90 ° C to dissolve. This was cooled to room temperature, palladium acetate (0.345, 1.54 mmol) was added, and the inside of the reaction vessel was replaced with argon. After 55 minutes, 9,10-dibromoanthracene (5.01 g, 14.9 mmol), 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (4.45 g, 32.0 mmol), and potassium tert-butoxide (4.26 g, 37.9 mmol) were added, and the inside of the reaction vessel was again placed under an argon atmosphere, and then heated and stirred in an oil bath at 90 ° C. After 140 minutes, the mixture was cooled to room temperature, diethyl ether (1 L) was added, and after stirring for a while, the precipitated solid was suction filtered and washed with diethyl ether. The diethyl ether in the filtrate was distilled off under reduced pressure, the toluene layer was back-extracted with water (150 mL), and the aqueous layer was distilled off under reduced pressure to obtain 3.77 g of an orange solid. This was suspended in acetone (50 mL) and stirred at room temperature overnight, after which the solid was suction filtered and washed with acetone to obtain 1.0 g of a yellow solid. This yellow solid was further dissolved in chloroform (41 mL) at 60° C., and then hexane (48 mL) was gradually added. After confirming the precipitation of a solid, the mixture was cooled overnight in a freezer, and the solid was suction filtered and washed with hexane to obtain 0.657 g (1.45 mmol, 10% yield) of the compound of the following formula (2-32) as a yellow solid. The obtained compound 1 The H-NMR measurement results are as follows: 1 H-NMR (500 MHz CDCl 3 ):δ8.03(q,4H,J=3.0Hz),7.43(q,4H,J=3.0Hz),3.59(t,4H,J=5.5Hz),3.48(t,4H,J=5.5Hz),3 .36(t,4H,J=5.5Hz),3.16(t,4H,J=5.5Hz),2.29(quin,4H,J=6.0Hz),1.86(quin,4H,J=6.0Hz).

[0145] [ka]

[0146] Synthesis Example 11 In a 100 mL eggplant flask, rac-BINAP (0.407 g, 0.653 mmol) and dehydrated toluene (60 mL) were placed and dissolved by heating at 90 ° C. This was cooled to room temperature, palladium acetate (0.124, 0.551 mmol) was added, and the inside of the reaction vessel was replaced with argon. After 30 minutes, 2,2'-dibromo-9,9'-spirobi[9H-fluorene] (2.32 g, 4.90 mmol), 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (1.47 g, 10.6 mmol), and potassium tert-butoxide (1.38 g, 12.3 mmol) were added, and the inside of the reaction vessel was again replaced with an argon atmosphere, and then heated and stirred in an oil bath at 90 ° C. After 21.25 hours, the mixture was cooled to room temperature, diethyl ether (300 mL) was added, and the mixture was stirred for a while. The precipitated solid was then suction filtered and washed with diethyl ether. The filtrate was back-extracted with water (60 mL), and the aqueous layer was distilled off under reduced pressure. The residue was purified by column chromatography to obtain 1.54 g (2.61 mmol, 53% yield) of the yellow amorphous compound of formula (2-33). The obtained compound 1 The H-NMR measurement results are as follows: 1 H NMR (500 MHz CDCl 3 ):δ7.70(dd,4H,J=8.0,14.0Hz),7.37(dd,2H,J=2.0,8.0Hz),7.29(t,2H, J=7.5Hz),7.01(dd,2H,J=1.0,7.5Hz),6.69(d,2H,J=8.0Hz),6.47(d,2H,J =2.0Hz),3.37-3.28(m,4H),3.24(t,4H,J=5.5Hz),3.13(t,4H,J=6.0Hz),3.09(t,4H,J=6.5Hz),1.91(quin,4H,J=6.0Hz),1.78(quin,4H,J=6.0Hz).

[0147] [ka]

[0148] Synthesis Example 12 In a 500 mL eggplant flask, rac-BINAP (1.60 g, 2.57 mmol) and dehydrated toluene (350 mL) were placed and dissolved by heating at 90 ° C. This was cooled to room temperature, palladium acetate (0.395 g, 1.76 mmol) was added, and the atmosphere in the reaction vessel was replaced with argon. After 30 minutes, 2,2',7,7'-dibromo-9,9'-spirobi[9H-fluorene] (4.43 g, 7.00 mmol), 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (4.06 g, 29.1 mmol), and potassium tert-butoxide (4.08 g, 36.3 mmol) were added, and the reaction vessel was again placed under an argon atmosphere, and then heated and stirred in an oil bath at 90 ° C. After 22.75 hours, the mixture was cooled to room temperature, diethyl ether (1.05 L) was added, and the mixture was stirred for a while, after which the precipitated solid was suction filtered and washed with diethyl ether. The filtered solid was dissolved in chloroform (100 mL), back-extracted with water (150 mL), and the aqueous layer was washed with chloroform (200 mL), and then the aqueous layer was distilled under reduced pressure to obtain 3.29 g of a brownish green amorphous substance as a crude product. This was suspended in acetone, and the solid was filtered off with suction and washed with acetone. The filtrate was evaporated under reduced pressure to obtain 2.32 g (2.68 mmol, 38% yield) of the compound of the following formula (2-34) as a yellow amorphous substance. Combined with the separately synthesized product, a total of 2.45 g was suspended in a diethyl ether / toluene / acetone mixed solvent (3 / 1 / 1.25 mL), and the solid was suction filtered and washed with a diethyl ether / toluene / acetone mixed solvent (3 / 1 / 1) to obtain 2.24 g of a pale yellow solid of the compound of the following formula (2-34) (purity 74.7%). The obtained compound 1 The H-NMR measurement results are as follows: 1 H NMR (500 MHz CDCl 3 ):δ7.66-7.55(m,4H),7.32-7.24(m,4H),6.55-6.40(m,4H),3.35(t,8H,J=5.5Hz),3.26-3.06(m,24H),1.96-1.88(m,8H),1.88-1.74(m,8H).

[0149] [ka]

[0150] Synthesis Example 13 A boron-containing compound represented by the following formula (4) was synthesized by the same method as in Synthesis Examples 1 to 3 of WO 2016 / 181705.

[0151] [ka]

[0152] Synthesis Example 14 <Synthesis of Monomers for Boron-Containing Polymers> A 300 mL reaction vessel was charged with the compound represented by the following formula (8) (3.96 g), 4-pyridineboronic acid (1.03 g), Pd(PPh 3 ) 4 (0.24 g), sodium carbonate (2.24 g), toluene (40 mL), distilled water (40 mL), and ethanol (20 mL) were added. The resulting suspension was stirred for 10 minutes while bubbling with argon, then heated to 95°C in an oil bath and stirred for 18 hours at the same temperature. Water (100 mL) and toluene (100 mL) were added to the resulting yellow solution to separate it into two layers. The organic layer was washed with water and saturated saline solution in that order, and then concentrated. The resulting residue was purified by column chromatography and preparative GPC to obtain a colorless solid. This was recrystallized from ethanol / hexane to obtain a compound (0.69 g) represented by the following formula (9).

[0153] [ka]

[0154] <Synthesis of boron-containing polymers> In an argon atmosphere, a compound represented by the above formula (9) (0.5 g), a compound represented by the following formula (10) (0.57 g), Pd(PPh 3 )4 (0.1g), sodium carbonate (0.472g), Aliquat336 (0.2g), toluene (10mL), and distilled water (10mL) were added. After bubbling with argon for about 15 minutes, the suspension was stirred for 24 hours while heating at 100 ° C in an oil bath. Iodobenzene (0.181g) was added to the suspension and stirred at the same temperature for 18 hours, after which phenylboronic acid (0.217g) was added and stirred for 18 hours. The organic layer of the resulting black-brown suspension was filtered through Celite, and the filtrate was concentrated. The resulting residue was purified by column purification to obtain a light brown powder. Heptane and ethanol were added to the suspension, and the mixture was heated and dispersed and washed. After cooling, the solid was filtered and washed with ethanol, obtaining 0.61g of boron-containing polymer (7).

[0155] [ka]

[0156] Example 1 An organic EL element having an inverted structure of the laminated structure shown in FIG. 1 was fabricated as follows. [1] A commercially available transparent glass substrate with an average thickness of 0.7 mm and a patterned electrode (cathode 3) made of ITO with a thickness of 150 nm and a width of 3 mm was prepared as the substrate 2. The substrate 2 with the cathode 3 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. The substrate 2 with the cathode 3 was then removed from the isopropanol, dried by nitrogen blowing, and UV ozone cleaned for 20 minutes. [2] The substrate 2 on which the cathode 3 was formed, which had been cleaned in [1], was fixed to the substrate holder of a Miratron sputtering device having a zinc metal target. The chamber of the sputtering device was filled with approximately 1×10 -4 After reducing the pressure to 100 Pa, sputtering was performed while introducing argon and oxygen, to form a zinc oxide layer (oxide layer 4) with a thickness of about 3 nm on the cathode 3 of the substrate 2. When forming the zinc oxide layer, care was taken to prevent the formation of a zinc oxide film on a portion of the ITO electrode (cathode 3) in order to allow for electrode extraction. The substrate 2 on which the oxide layer 4 had been formed was annealed in air at 400°C for 1 hour. [3] Next, an organic thin film containing a first material and a second material was formed as an electron injection layer 5 on the oxide layer 4 by the method described below. First, the boron-containing compound represented by formula (4) and the compound represented by formula (2-2) (weight ratio 1:0.05) were dissolved in cyclopentanone (concentration 0.5% by weight) to obtain a coating composition. Next, the cathode 3 prepared in [2] and the substrate 2 on which the oxide layer 4 was formed were placed on a spin coater. Then, while dropping the coating composition onto the oxide layer 4, the substrate 2 was rotated at 3000 rpm for 30 seconds to form a coating film. After that, an annealing treatment was performed at 150° C. for 1 hour using a hot plate in a nitrogen atmosphere to form an electron injection layer 5. The average thickness of the obtained electron injection layer 5 was 15 nm. [4] Next, the substrate 2 on which each layer up to the electron injection layer 5 had been formed was fixed to a substrate holder of a vacuum deposition apparatus. In addition, bis[2-(2-benzothiazolyl)phenolato]zinc(II) (Zn(BTZ) 2 ) and tris[1-phenylisoquinoline]iridium(III) (Ir(piq) 3 ), N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) represented by the following formula (13), 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) represented by the following formula (14), and Al were each placed in an alumina crucible and set as a deposition source.

[0157] [ka]

[0158] Then, the inside of the chamber of the vacuum deposition device was 1×10 -5 The pressure was reduced to 100 Pa, and an electron transport layer 10, a light emitting layer 6, a hole transport layer 7, a hole injection layer 8, and an anode 9 were successively formed by a vacuum deposition method using resistance heating. First, Zn(BTZ) 2Then, the electron transport layer 10 having a thickness of 10 nm was formed. 2 Host, Ir(piq) 3 was co-evaporated as a dopant to a thickness of 20 nm to form the light-emitting layer 6. At this time, the doping concentration was Ir(piq) 3 was 6 mass % with respect to the entire light emitting layer 6. Next, a 50 nm film of α-NPD was formed on the substrate 2 on which the light emitting layer 6 had been formed, to form a hole transport layer 7. Furthermore, a 10 nm film of HAT-CN was formed to form a hole injection layer 8. Next, a 100 nm thick anode 9 made of aluminum 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 with a width of 3 mm, and the light-emitting area of ​​the fabricated organic EL element was 9 mm 2 It was decided. [5] Next, the substrate 2 on which each layer up to the anode 9 was formed was placed in a glass cap (sealing container) having a concave space, and sealed by filling it with a sealant made of an ultraviolet (UV) curable resin, thereby obtaining the organic EL element of Example 1.

[0159] Example 2 An organic EL device of Example 2 was obtained in the same manner as in Example 1, except that in the step [3] of Example 1, the compound of formula (2-4) was used instead of the compound of formula (2-2).

[0160] Comparative Example 1 An organic EL element of Comparative Example 1 was obtained in the same manner as in Example 1, except that in step [3] of Example 1, the compound of Formula (2-2) was not used, and a coating composition in which only the boron-containing compound represented by Formula (4) was dissolved in cyclopentanone (concentration: 0.5 wt %) was used.

[0161] A voltage was applied to the organic EL elements prepared in Examples 1 and 2 and Comparative Example 1 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. The results are shown in FIG.

[0162] Example 3 An organic EL device of Example 3 was obtained in the same manner as in Example 1, except that in step [3] of Example 1, a coating composition was used in which a boron-containing compound represented by formula (4) and a compound represented by formula (2-2) (weight ratio 1:2) were dissolved in cyclopentanone (concentration: 0.5 wt %).

[0163] Example 4 An organic EL device of Example 4 was obtained in the same manner as in Example 1, except that in step [3] of Example 1, a coating composition was used in which a boron-containing compound represented by formula (4) and a compound represented by formula (2-9) (weight ratio 1:2) were dissolved in cyclopentanone (concentration: 0.5 wt %).

[0164] Comparative Example 2 An organic EL element of Comparative Example 2 was obtained in the same manner as in Example 1, except that in step [3] of Example 1, a coating composition was used in which a boron-containing compound represented by formula (4) and MTBD represented by the following formula (15) were dissolved in cyclopentanone (concentration: 0.5 wt %) (weight ratio: 1:2).

[0165] [ka]

[0166] A voltage was applied to the organic EL elements produced in Examples 3 and 4 and Comparative Examples 1 and 2 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. The results are shown in FIG. 13. The light emission of these elements is shown in FIG. 14.

[0167] Example 5 An organic EL device of Example 5 was obtained in the same manner as in Example 1, except that the step [3] of Example 1 was changed to the following [3-1]. [3-1] Using a vacuum deposition apparatus, a boron-containing compound represented by formula (4) was co-deposited as a host and a compound represented by formula (2-2) as a dopant to a thickness of 10 nm to form an electron injection layer 5. At this time, the doping concentration of the compound represented by formula (2-2) was set to 5 mass % relative to the entire electron injection layer 5.

[0168] Comparative Example 3 An organic EL device of Comparative Example 3 was obtained in the same manner as in Example 5, except that in the step [3-1] of Example 5, only the boron-containing compound represented by formula (4) was deposited to a thickness of 10 nm.

[0169] A voltage was applied to the organic EL elements prepared in Example 5 and Comparative Example 3 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. The results are shown in FIG.

[0170] Example 6 An organic EL device of Example 6 was obtained in the same manner as in Example 1, except that the step [2] in Example 1 was not carried out and the step [3] was carried out as described above in [3-1].

[0171] Voltage was applied to the organic EL elements prepared in Examples 5 and 6 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. The results are shown in FIG.

[0172] Example 7 An organic EL device of Example 7 was obtained in the same manner as in Example 5, except that in step [3-1] of Example 5, a triazine compound represented by the following formula (16) described in JP 2018-206889 A was used instead of the compound of formula (4), and the doping concentration of formula (2-2) was 10 mass%.

[0173] [ka]

[0174] Example 8 An organic EL device of Example 8 was obtained in the same manner as in Example 1, except that the step [3] of Example 1 was changed to the following [3-2]. [3-2] Using a vacuum deposition apparatus, the compound of formula (2-2) was deposited to a thickness of 1 nm, and then the compound of formula (16) was deposited to a thickness of 10 nm, to form an electron injection layer 5 in which the compound of formula (2-2) and the compound of formula (16) were laminated.

[0175] Comparative Example 4 An organic EL device of Comparative Example 4 was obtained in the same manner as in Example 7, except that in the step [3-1] of Example 7, only the triazine compound represented by the formula (16) was formed into a film having a thickness of 10 nm.

[0176] A voltage was applied to the organic EL elements prepared in Examples 7 and 8 and Comparative Example 4 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. The results are shown in FIG.

[0177] Example 9 An organic EL device of Example 9 was obtained in the same manner as in Example 5, except that in step [3-1] of Example 5, a boron compound represented by the following formula (17) was used instead of the compound of formula (4), and the doping concentration of formula (2-2) was 5 mass %.

[0178] [ka]

[0179] Example 10 An organic EL device of Example 10 was obtained in the same manner as in Example 1, except that the step [3] of Example 1 was changed to the following [3-3]. [3-3] First, the boron-containing polymer represented by the following formula (7) was dissolved in dimethylacetamide (concentration: 0.1% by weight) to obtain a coating composition. Next, the cathode 3 and the substrate 2 on which the oxide layer 4 was formed, which were prepared in [2], were placed on a spin coater. Then, while dropping the coating composition onto the oxide layer 4, the substrate 2 was rotated at 3000 rpm for 30 seconds to form a coating film. After that, an annealing treatment was performed at 120°C for 2 hours using a hot plate in a nitrogen atmosphere to form a layer of the second material composed of the compound of formula (7). The average thickness of the obtained layer was 15 nm. Next, the substrate 2 was fixed to a substrate holder of a vacuum deposition device, and a 10 nm thick co-deposition was performed using the boron-containing compound represented by formula (16) as a host and the compound of formula (2-2) as a dopant, and an electron injection layer 5 in which a mixed film of the compound of formula (17) and the compound of formula (2-2) was laminated on the upper layer of the compound of formula (7) was formed. At this time, in the mixed film of the compound of formula (17) and the compound of formula (2-2), the compound of formula (2-2) was set to 5 mass % relative to the boron compound of formula (17).

[0180] [ka]

[0181] Voltage was applied to the organic EL elements prepared in Examples 9 and 10 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, and the change in luminance over time. The results are shown in Figures 18 and 19.

[0182] Example 11 An organic EL element 11 having a stacked structure shown in FIG. 20 was manufactured by the method described below. [1] A commercially available transparent glass substrate 2 (hereinafter simply referred to as substrate) having an average thickness of 0.7 mm and having an anode 9 made of an ITO film (patterned to a thickness of 100 nm and a width of 3 mm) was prepared. [2] Next, the substrate 2 having the anode 9 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and then boiled in isopropanol for 5 minutes. The substrate was then removed from the isopropanol, dried by nitrogen blowing, and subjected to UV ozone cleaning for 20 minutes. [3] Next, a hole injection layer 8 made of PEDOT (Clevios HIL1.3N) was formed to a thickness of 30 nm. [4] Next, the substrate on which PEDOT was formed was fixed to a substrate holder in the chamber of a vacuum deposition device, and the chamber of the vacuum deposition device was filled with 1×10 -5 The pressure was reduced to 100 MPa (120 MPa), and a hole transport layer 7, an emitting layer 6, an electron transport layer 10, an electron injection layer 5, a cathode 1 (cathode 3′ in FIG. 20), and a cathode 2 (cathode 3 in FIG. 20) were successively formed by a vacuum deposition method using resistance heating. First, a hole transport layer having a thickness of 30 nm was formed from α-NPD represented by the above formula (13). Then, Zn(BTZ) represented by the above formula (11) was 2 is the host, and Ir(piq) represented by the above formula (12) 3 The light-emitting layer was formed by co-evaporation of 30 nm of Ir(piq) as a dopant. 3 was 6 mass % relative to the entire light emitting layer. Next, a 40 nm film of TmPPyTz represented by the following formula (18) was formed on the substrate on which the light emitting layer had been formed to form an electron transport layer. Furthermore, a 1 nm film of the compound represented by the above formula (2-2) was formed to form an electron injection layer. Next, a 25 nm film of cathode 1 (cathode 3' in FIG. 20) was formed by co-evaporating silver and magnesium at a mass ratio of 9:1 on the substrate on which the electron injection layer had been formed, and then a 100 nm thick cathode 2 (cathode 3 in FIG. 20) made only of silver was formed. The cathodes 1 and 2 were formed using a stainless steel deposition mask so that the deposition surface would be a strip with a width of 3 mm, and the light-emitting area of ​​the fabricated organic EL element was 9 mm 2 It was decided. [5] Next, the substrate on which each layer up to the cathode was formed was placed in a glass cap (sealing container) having a concave space, and sealed by filling it with a sealant made of an ultraviolet (UV) curable resin, thereby obtaining the organic EL element of Example 11.

[0183] [ka]

[0184] A voltage was applied to the organic EL element prepared in Example 11 and the organic EL element prepared in Example 8 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. The results are shown in FIG.

[0185] Example 12 An element of Example 12 was produced in the same manner as in Example 11, except that the step [4] in Example 11 was changed to [4-1]. [4-1] Next, the substrate on which PEDOT was formed was fixed to a substrate holder in the chamber of a vacuum deposition device, and the chamber of the vacuum deposition device was filled with 1×10 -5 The pressure was reduced to 100 MPa, and a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode were successively formed by a vacuum deposition method using resistance heating. First, a hole transport layer having a thickness of 40 nm was formed from α-NPD represented by the above formula (13). Then, Zn(BTZ) represented by the above formula (11) was 2 is the host, and Ir(piq) represented by the above formula (12) 3 The light-emitting layer was formed by co-evaporation of 30 nm of Ir(piq) as a dopant. 3 was 6 mass % relative to the entire light emitting layer. Next, a 10 nm film of the boron-containing compound represented by formula (4) was formed on the substrate on which the light emitting layer had been formed to form an electron transport layer. Furthermore, the boron-containing compound represented by formula (4) was co-deposited as a host and the compound represented by formula (2-2) as a dopant to form an electron injection layer having a thickness of 35 nm, with the doping concentration of the compound represented by formula (2-2) being 5 mass% relative to the entire electron injection layer. Next, a cathode made of aluminum and having a thickness of 100 nm was formed on the substrate on which the electron injection layer had been formed. The cathode was formed using a stainless steel deposition mask so that the deposition surface would be a strip with a width of 3 mm, and the light-emitting area of ​​the fabricated organic EL element was 9 mm 2 It was decided.

[0186] Example 13 A device of Example 13 was produced in the same manner as in Example 12, except that the doping concentration of the compound (2-2) in the electron injection layer was changed to 20% by mass.

[0187] Comparative Example 5 A device of Comparative Example 5 was produced in the same manner as in Example 12, except that the material used in the electron injection layer was the boron-containing compound of formula (4) alone.

[0188] Comparative Example 6 A device of Comparative Example 6 was prepared in the same manner as in Example 12, except that the thickness of the boron compound (4) in the electron transport layer was 45 nm and the material used in the electron injection layer was lithium fluoride formed into a film of 0.8 nm.

[0189] Example 14 An element of Example 14 was produced in the same manner as in Example 12, except that the step [4-1] in Example 12 was changed to [4-2]. [4-2] Next, the substrate on which PEDOT was formed was fixed to a substrate holder in the chamber of a vacuum deposition device, and the chamber of the vacuum deposition device was filled with 1×10 -5 The pressure was reduced to 100 Pa, and a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode were successively formed by a vacuum deposition method using resistance heating. First, a hole transport layer having a thickness of 40 nm was formed from α-NPD represented by the above formula (13). Then, Zn(BTZ) represented by the above formula (11) was 2 is the host, and Ir(piq) represented by the above formula (12) 3 The light-emitting layer was formed by co-evaporation of 30 nm of Ir(piq) as a dopant. 3was 6 mass % relative to the entire light emitting layer. Next, a 10 nm film of the boron-containing compound represented by formula (4) was formed on the substrate on which the light emitting layer had been formed to form an electron transport layer. Furthermore, the boron-containing compound represented by formula (4) was co-deposited as a host and the compound represented by formula (2-2) as a dopant to a thickness of 35 nm, with the doping concentration of the compound represented by formula (2-2) being 5 mass % relative to the entire electron injection layer 1. Furthermore, a boron-containing compound represented by formula (4) was deposited to a thickness of 5 nm to form an electron injection layer which was a laminate film of a film containing the first material and the second material and a film containing only the second material. Next, a cathode made of aluminum and having a thickness of 100 nm was formed on the substrate on which the electron injection layer had been formed. The cathode was formed using a stainless steel deposition mask so that the deposition surface would be a strip with a width of 3 mm, and the light-emitting area of ​​the fabricated organic EL element was 9 mm 2 It was decided.

[0190] A voltage was applied to the organic EL elements produced in Examples 12 to 14 and Comparative Examples 5 and 6 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. The results are shown in FIG. 22. In addition, the changes in luminance over time of the organic EL elements of Example 13 and Comparative Example 6, and the changes in luminance over time of the organic EL elements of Examples 12 and 14 were examined. The results are shown in FIG. 23 and FIG. 24.

[0191] Example 15 An organic EL element having a stacked structure shown in FIG. 25 was fabricated by the method described below. [1] A commercially available transparent glass substrate 2 with an ITO electrode layer having an average thickness of 0.7 mm was prepared. In this case, the ITO electrode (anode 9) of the substrate was patterned to a width of 2 mm. After ultrasonic cleaning with Clean Ace and pure water, the substrate was steam-cleaned in isopropanol for 5 minutes. The substrate was dried with nitrogen blowing and then subjected to UV ozone cleaning for 10 minutes. [2] This substrate was set on a spin coater, poly(3,4-ethylenedioxythiophene / styrenesulfonic acid) (PEDOT / PSS) (Clevios CH8000) was dropped onto it, and it was rotated at 2000 rpm for 60 seconds, and then dried on a hot plate at 130°C for 10 minutes to form a hole injection layer 8 made of PEDOT / PSS on the anode. The average thickness of the hole injection layer was 50 nm. The average thickness of the hole injection layer was measured using a stylus step gauge. [3] A 2% xylene solution of poly(dioctylfluorene-alt-benzothiadiazole) (F8BT) was prepared. The substrate prepared in the above step [2] was set on a spin coater. The F8BT-xylene solution was dropped onto the hole injection layer formed in the above step [2], and the substrate was rotated at 2,000 revolutions per minute for 60 seconds to form an emitting layer 6 made of F8BT. The average thickness of the emitting layer was 20 nm. The average thickness of the emitting layer was measured using a stylus step gauge. [4] The substrate prepared in the above step [3] was set on a spin coater. A 1-propanol solution (1 wt%) of the compound of formula (2-2) was dropped onto the light-emitting layer formed in the above step [3], and the substrate was rotated at 2000 rpm for 60 seconds to form an electron injection layer 5 on the light-emitting layer. The average thickness of the electron injection layer was below the measurement limit of the stylus step-difference spectrometry. [5] The substrate prepared in step [4] above was fixed to the substrate holder of a vacuum deposition apparatus. An aluminum wire (Al) was placed in an alumina crucible and set as the deposition source. The inside of the vacuum deposition apparatus was filled with approximately 1×10 -4 The pressure in the vacuum chamber was reduced to 1 Pa, and Al (cathode 3) was deposited on the electron injection layer to an average thickness of 100 nm to produce an organic electroluminescence device. The average thickness of the cathode was measured during film formation using a quartz crystal thickness gauge.

[0192] Comparative Example 7 An organic EL device was prepared by carrying out the same steps [1] to [3] as in Example 15, and then carrying out the following step [4-1]. [4-1] The substrate prepared in the above step [3] was fixed to the substrate holder of a vacuum deposition apparatus. Lithium fluoride (LiF) and aluminum wire (Al) were placed in a pot and set in the deposition source. The inside of the vacuum deposition apparatus was filled with approximately 1×10-4 The pressure was reduced to 1 Pa, LiF (electron injection layer 5) was deposited to an average thickness of 1 nm, and then Al (cathode 3) was deposited to an average thickness of 100 nm to prepare an organic electroluminescent device.

[0193] A voltage was applied to the organic EL elements prepared in Example 15 and Comparative Example 7 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. The results are shown in FIG.

[0194] Examples 16 to 20 and Comparative Examples 8 to 15 Organic EL devices having a normal structure were manufactured by the following method. The devices of Examples 16 to 20 and Comparative Examples 8, 10, 12, and 14 had the layered structure shown in Fig. 2, and the devices of Comparative Examples 9, 11, 13, and 15 had the layered structure shown in Fig. 2 without the electron injection layer 5. [1] As the substrate 2, a commercially available transparent glass substrate 2 having an average thickness of 0.7 mm and a patterned electrode (anode 9) made of ITO with a thickness of 100 nm and a width of 3 mm was prepared. Then, the substrate 2 having the anode 9 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. Thereafter, the substrate 2 having the anode 9 was taken out of the isopropanol, dried by nitrogen blowing, and subjected to UV ozone cleaning for 20 minutes.

[0195] [2] The substrate 2 on which the anode 9 was formed and cleaned in [1] was set on a spin coater, and a hole injection layer 8 was formed to a thickness of 10 nm using a hole injection material "Clevios HIL1.3N" manufactured by Heraeus AG. It was then heated on a hot plate heated to 180°C for 1 hour.

[0196] [3] Next, the substrate 2 on which the hole injection layer 8 had been formed was fixed to a substrate holder of a vacuum deposition apparatus. In addition, 2,4-diphenyl-6-bis((12-phenylindolo)[2,3-a]carbazol-11-yl)-1,3,5-triazine (DIC-TRZ) represented by the following formula (19) and fac-tris(3-methyl-2-phenylpyridinato-N,C2'-)iridium(III) (Ir(mppy) 3 ), α-NPD represented by the above formula (13), N3,N3'''-bis(dibenzo[b,d]thiophen-4-yl)-N3,N3'''-diphenyl-[1,1':2',1'':2'',1'''-quaterphenyl]-3,3'''-diamine (4DBTP3Q) represented by the following formula (21), a compound of formula (2-2) as the first material, various materials as the second material (electron transport material) shown below, and Al were each placed in an alumina crucible and set as a deposition source.

[0197] [ka]

[0198] For the second material, the compound represented by the following formula (22) was used as an example of a pyridine-containing compound, the compound represented by the following formula (23) and the compound represented by the following formula (26) were used as examples of a triazine derivative, the compound having a heterocycle containing a carbonyl group was the following formula (24) (commercially available product), and the compound represented by the following formula (25) was used as an example of a phenanthroline derivative.

[0199] [ka]

[0200] Then, the inside of the chamber of the vacuum deposition device was 1×10 -5 The pressure was reduced to 100 Pa, and a hole transport layer 7, a light emitting layer 6, an electron transport layer 10, an electron injection layer 5, and a cathode 3 were successively formed by a vacuum deposition method using resistance heating. Specifically, a hole transport layer 7 having a thickness of 30 nm was formed by using α-NPD of 20 nm and 4DBTP3Q of 10 nm. 3 was co-evaporated as a dopant to a thickness of 25 nm to form the light-emitting layer 6. At this time, the doping concentration was Ir(mppy) 3 was 3 mass % relative to the entire light emitting layer 6. Next, a 40 nm electron transport layer 10 and a 1 nm electron injection layer 5 were formed on the substrate 2 on which the light emitting layer 6 had been formed. Next, a cathode 3 made of aluminum and having a thickness of 100 nm was formed by vacuum deposition on the substrate 2 on which the electron injection layer 5 had been formed. The cathode 3 was formed using a stainless steel deposition mask so that the deposition surface would be in the shape of a strip with a width of 3 mm, and the light emitting area of ​​the produced organic EL element was set to 9 mm 2 It was decided.

[0201] In each example, the compounds used as the second material (electron transport layer) and the first material (electron injection layer) are as follows. Example 16: The compound of formula (22) was used as the second material, and the compound of formula (2-2) was used as the first material. Example 17: The compound of formula (23) was used as the second material, and the compound of formula (2-2) was used as the first material. Example 18: The compound of formula (24) was used as the second material, and the compound of formula (2-2) was used as the first material. Example 19: The compound of formula (25) was used as the second material, and the compound of formula (2-2) was used as the first material. Example 20: The compound of formula (26) was used as the second material, and the compound of formula (2-2) was used as the first material.

[0202] In Comparative Examples 8, 10, 12, and 14, the compounds used as the second material (electron transport layer) and the first material (electron injection layer) are as follows. Comparative Example 8: The compound of formula (22) was used as the second material, and lithium fluoride was used as the first material. Comparative Example 10: The compound of formula (23) was used as the second material, and lithium fluoride was used as the first material. Comparative Example 12: The compound of formula (24) was used as the second material, and lithium fluoride was used as the first material. Comparative Example 14: The compound of formula (26) was used as the second material, and lithium fluoride was used as the first material.

[0203] Furthermore, in Comparative Examples 9, 11, 13, and 15, the compounds used as the second material (electron transport layer) were as follows: A cathode was produced without forming an electron injection layer (first material). Comparative Example 9: The compound of formula (22) was used as the second material. Comparative Example 11: The compound of formula (23) was used as the second material. Comparative Example 13: The compound of formula (24) was used as the second material. Comparative Example 15: The compound of formula (25) was used as the second material.

[0204] [4] Next, the substrate 2 on which each layer up to the cathode 3 was formed was placed in a glass cap (sealing container) having a concave space, and sealed by filling it with a sealant made of an ultraviolet (UV) curing resin to obtain each organic EL element.

[0205] A voltage was applied to the organic EL elements produced in Examples 16 to 20 and Comparative Examples 8 to 15 using a Keithley 2400-type source meter, and the luminance was measured using a Konica Minolta LS-100 to examine the relationship between the applied voltage and the luminance. The results are shown in Figures 27 to 31. Figure 32 shows the results of the change in luminance over time in a room temperature environment for the organic EL elements of Example 20 and Comparative Example 15, and Figure 33 shows the results of the change in luminance over time in an 85°C environment for the organic EL elements of Example 20 and Comparative Example 15.

[0206] Examples 21 and 22, Comparative Example 16 Organic EL devices having a normal structure were prepared and evaluated by the following method. The devices of Example 21 and Comparative Example 16 are organic EL devices having the layered structure shown in Fig. 3, and the device of Example 22 is an organic EL device having the layered structure shown in Fig. 4. [1] As the substrate 2, a commercially available transparent glass substrate 2 having an average thickness of 0.7 mm and a patterned electrode (anode 9) made of ITO with a thickness of 100 nm and a width of 3 mm was prepared. Then, the substrate 2 having the anode 9 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. Thereafter, the substrate 2 having the anode 9 was taken out of the isopropanol, dried by nitrogen blowing, and subjected to UV ozone cleaning for 20 minutes.

[0207] [2] The substrate 2 on which the anode 9 was formed and cleaned in [1] was set on a spin coater, and a hole injection layer 8 was formed to a thickness of 10 nm using a hole injection material "Clevios HIL1.3N" manufactured by Heraeus AG. It was then heated on a hot plate heated to 180°C for one hour.

[0208] [3] Next, the substrate 2 on which the hole injection layer 8 had been formed was fixed to a substrate holder of a vacuum deposition apparatus. 3 The α-NPD, 4DBTP3Q, the compound represented by formula (2-2) as the first material, lithium fluoride, and Al were each placed in an alumina crucible and set as a deposition source. Then, the inside of the chamber of the vacuum deposition device was 1×10 -5 The pressure was reduced to 100 Pa, and a hole transport layer 7, a light emitting layer 6, an electron injection layer 5, and a cathode 3 were successively formed by a vacuum deposition method using resistance heating. Specifically, a hole transport layer 7 having a thickness of 30 nm was formed by using α-NPD of 20 nm and 4DBTP3Q of 10 nm. 3 was co-evaporated as a dopant to a thickness of 25 nm to form the light-emitting layer 6. At this time, the doping concentration was Ir(mppy) 3 was 3 mass % relative to the entire light emitting layer 6. Next, on the substrate 2 on which the light emitting layer 6 had been formed, an electron transport layer 10 made of DIC-TRZ having a thickness of 40 nm and an electron injection layer 5 having a thickness of 1 nm were formed. In Example 21, the compound represented by formula (2-2) was used for the electron injection layer 5, and in Comparative Example 16, lithium fluoride, which is a general electron injection material, was used for the electron injection layer 5. In Example 22, DIC-TRZ was used for the hole transport layer 7 having a thickness of 30 nm, and the other layers were the same as those in Example 21.

[0209] The luminance-voltage characteristics of the elements of Examples 21 and 22 and Comparative Example 16 were measured in the same manner as in the other Examples and Comparative Example, and the results are shown in FIG.

[0210] Example 23, Comparative Example 17 In Examples 21 and 22, the emitting layer was composed of two types of materials, a host and a dopant. In order to demonstrate that the simple structure shown in FIG. 4 can be realized in an organic EL element having an emitting layer composed of a single type of material, the elements of Example 23 and Comparative Example 17 were prepared as follows.

[0211] [1] As the substrate 2, a commercially available transparent glass substrate 2 having an average thickness of 0.7 mm and a patterned electrode (anode 9) made of ITO with a thickness of 100 nm and a width of 3 mm was prepared. Then, the substrate 2 having the anode 9 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. Thereafter, the substrate 2 having the anode 9 was taken out of the isopropanol, dried by nitrogen blowing, and subjected to UV ozone cleaning for 20 minutes.

[0212] [2] Next, the substrate 2 was fixed to a substrate holder of a vacuum deposition apparatus. In addition, fullerene used for the hole injection layer 8, (9,10-bis(4-(9H-carbazol-9-yl)-2,6-dimethylphenyl)-9,10-diboraanthracene (CzDBA) represented by the following formula (27), a compound represented by the formula (2-2) as the first material, lithium quinoline, and Al were each placed in an alumina crucible and set as a deposition source. In addition, molybdenum trioxide used for the hole injection layer 8 was placed in a tungsten board and set.

[0213] [ka]

[0214] Then, the inside of the chamber of the vacuum deposition device was 1×10 -5 The pressure was reduced to 100 Pa, and each layer was deposited by vacuum deposition using resistance heating. Molybdenum trioxide and fullerene were deposited to a thickness of 5 nm as the hole injection layer 8, and only CzDBA was deposited to a thickness of 75 nm as the combined layer of the hole transport layer 7, the light emitting layer 6, and the electron transport layer 10. Thereafter, an electron injection layer 5 having a thickness of 1 nm and a cathode 3 were formed in succession to prepare an organic EL device. In Example 23, the compound represented by formula (2-2) was used for the electron injection layer 5, and in Comparative Example 17, lithium quinoline, a common electron injection material, was used for the electron injection layer 5.

[0215] The luminance-voltage characteristics of the elements of Example 23 and Comparative Example 17 were measured in the same manner as in the other Examples and Comparative Examples, and the results are shown in FIG.

[0216] Example 24, Comparative Example 18 In Example 24, an organic EL device was produced in the same manner as in Example 21, except that the compound represented by formula (2-11) was used as the first material (electron injection layer 5). In Comparative Example 18, an organic EL element was produced in the same manner as in Example 21, except that the first material (electron injection layer 5) was not used.

[0217] The luminance-voltage characteristics of the elements of Example 24 and Comparative Example 18 were measured in the same manner as in the other Examples and Comparative Examples, and the results are shown in FIG.

[0218] Example 25 An organic EL element having an inverted structure of the laminated structure shown in FIG. 1 was fabricated as follows. [1] A commercially available transparent glass substrate 2 having an average thickness of 0.7 mm and a patterned electrode (cathode 3) made of ITO having a thickness of 150 nm and a width of 3 mm was prepared as the substrate 2. The substrate 2 having the cathode 3 was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. The substrate 2 having the cathode 3 was then removed from the isopropanol, dried by nitrogen blowing, and subjected to UV ozone cleaning for 20 minutes. [2] The substrate 2 on which the cathode 3 was formed, which had been cleaned in [1], was fixed to the substrate holder of a Miratron sputtering device having a zinc metal target. The chamber of the sputtering device was filled with approximately 1×10 -4 After the pressure was reduced to 100 Pa, sputtering was carried out while introducing argon and oxygen, to form a zinc oxide layer with a thickness of about 3 nm on the cathode 3 of the substrate 2. [3] Next, a 1.0 wt% solution of magnesium acetate in ethanol was prepared. The substrate on which the zinc oxide layer was prepared was set on a spin coater, the magnesium acetate solution was dropped onto it, and the substrate was rotated at 1300 rpm for 60 seconds. The substrate was then annealed in air at 400°C for 1 hour to form a magnesium oxide film with a thickness of 3 nm. Through steps [2] and [3], a substrate was obtained on which oxide layer 4 was formed, in which a zinc oxide layer and a magnesium oxide layer were laminated. [4] Next, an organic thin film containing a first material and a second material was formed as an electron injection layer 5 on the oxide layer 4 by the method described below. First, the boron-containing compound represented by formula (4) and the compound represented by formula (2-30) (weight ratio 1:0.4) were dissolved in cyclopentanone (concentration 1.0 wt%) to obtain a coating composition. Next, the cathode 3 prepared in [2] and the substrate 2 on which the oxide layer 4 was formed were placed on a spin coater. Then, while dropping the coating composition onto the oxide layer 4, the substrate 2 was rotated at 3000 rpm for 30 seconds to form a coating film. After that, an annealing treatment was performed at 150° C. for 1 hour using a hot plate in a nitrogen atmosphere to form an electron injection layer 5. The average thickness of the obtained electron injection layer 5 was 20 nm. [5] Next, the substrate 2 on which each layer up to the electron injection layer 5 had been formed was fixed to a substrate holder of a vacuum deposition apparatus. In addition, bis[2-(2-benzothiazolyl)phenolato]zinc(II) (Zn(BTZ) 2 ) and tris[1-phenylisoquinoline]iridium(III) (Ir(piq) 3 ), N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) represented by formula (13), 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) represented by formula (14), and Al were each placed in an alumina crucible and set as a deposition source.

[0219] Then, the inside of the chamber of the vacuum deposition device was 1×10 -5 The pressure was reduced to 100 Pa, and an electron transport layer 10, a light emitting layer 6, a hole transport layer 7, a hole injection layer 8, and an anode 9 were successively formed by a vacuum deposition method using resistance heating. First, Zn(BTZ) 2 Then, the electron transport layer 10 having a thickness of 10 nm was formed. 2 host, Ir(piq) 3 was co-evaporated as a dopant to a thickness of 20 nm to form the light-emitting layer 6. At this time, the doping concentration was Ir(piq) 3 was 6 mass % with respect to the entire light emitting layer 6. Next, a 50 nm film of α-NPD was formed on the substrate 2 on which the light emitting layer 6 had been formed, to form a hole transport layer 7. Furthermore, a 10 nm film of HAT-CN was formed to form a hole injection layer 8. Next, a 100 nm thick anode 9 made of aluminum 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 with a width of 3 mm, and the light-emitting area of ​​the fabricated organic EL element was 9 mm 2 It was decided. [6] Next, the substrate 2 on which each layer up to the anode 9 was formed was placed in a glass cap (sealing container) having a concave space, and sealed by filling it with a sealant made of an ultraviolet (UV) curable resin, thereby obtaining the organic EL element of Example 25.

[0220] Example 26 An organic EL device of Example 26 was obtained in the same manner as in Example 25, except that in the step [4] of Example 25, the compound of formula (2-31) was used instead of the compound of formula (2-30).

[0221] Comparative Example 19 An organic EL element of Comparative Example 19 was obtained in the same manner as in Example 25, except that in step [4] of Example 25, the compound of formula (2-30) was not used, and a coating composition in which only the boron-containing compound represented by formula (4) was dissolved in cyclopentanone (concentration: 1.0 wt %) was used.

[0222] For the elements of Examples 25 and 26 and Comparative Example 19, the luminance-voltage characteristics were measured in the same manner as in the other Examples and Comparative Examples, and the results are shown in FIG.

[0223] In Fig. 12, the devices of Examples 1 and 2 using the compounds (2-2) and (2-4) emit light at a lower voltage than the device of Comparative Example 1 using only the boron-containing compound represented by formula (4) as the material for the electron injection layer. Also, as shown in Fig. 13, the devices of Examples 3 and 4 using the compounds (2-2) and (2-4) emit light at a lower voltage than the device using the boron-containing compound represented by formula (4) and MTBD. From these results, it was confirmed that the device can be driven at a lower voltage by using the hexahydropyrimidopyrimidine compound represented by general formula (1) of the present invention in combination with an electron transport material. Furthermore, as shown in FIG. 14, when the hexahydropyrimidopyrimidine compound represented by the general formula (1) of the present invention was used in combination with an electron transporting material, a clean light-emitting surface was obtained without any chipping, unlike the case where MTBD was used. Furthermore, from the results shown in FIG. 15, it was confirmed that a device that operates at a low voltage can be obtained even when the hexahydropyrimidopyrimidine compound represented by the general formula (1) of the present invention is used in combination with an electron transporting material to form a layer by vapor deposition, and it was confirmed that a device exhibiting excellent characteristics can be fabricated by forming a film by either coating or vapor deposition using a material in which this hexahydropyrimidopyrimidine compound is used in combination with an electron transporting material, without being restricted by the manufacturing process.

[0224] Furthermore, from the results shown in FIG. 16, it was confirmed that when the hexahydropyrimidopyrimidine compound represented by the general formula (1) of the present invention is used in combination with an electron transporting material, the same characteristics as those obtained when a metal oxide layer is not formed between the electron injection layer formed by this material and the cathode can be obtained, and thus it is possible to simplify the configuration of the element. 17, the effect of doping a hexahydropyrimidopyrimidine compound other than the compound of formula (4) can be seen from Example 7 and Comparative Example 4. Also, Example 8 shows that the effect is obtained even when the electron injection layer is a laminated film rather than a mixed film of the first material and the second material. Furthermore, from the results of FIG. 18, it can be seen that in Example 9 (although there is no comparative example), the element in which the compound of formula (17) is doped with a hexahydropyrimidopyrimidine compound exhibits good characteristics at a level equivalent to that of Example 5. Also, from Example 10, it can be seen that, as a constituent of the electron injection layer, a different material (for example, a 2x material) is inserted between the layer that is a mixed film of the first material + the second material and the metal oxide layer 4, and the element exhibits good characteristics similar to those of Example 9. Furthermore, it has been confirmed from the results of FIG. 19 that this configuration extends the lifespan. It is presumed that this is because the first material is prevented from deteriorating due to interaction with the metal oxide layer. 21, the device of Example 11, which is a forward-structure organic EL device, has good characteristics by using the compound of formula (2-2) alone as the electron injection layer, and the device of Example 11, which uses the compound of formula (2-2) as a single layer electron injection layer, has characteristics at the same level as the device of Example 8, which is an inverted-structure organic EL device using the same hole transport material and light-emitting material. Therefore, it was demonstrated that the electron injection layer of the present invention functions well even in a forward-structure organic EL device.

[0225] The results in FIG. 22 show that the devices of Examples 12 and 13 emit light at a lower voltage than the device of Comparative Example 5 in which only the boron compound (4) was used in the electron injection layer. This confirms the effect of using a hexahydropyrimidopyrimidine compound in combination with an electron transport material in a forward structure organic EL device. 23, it was confirmed that the device of Example 13 had a long life while having the same level of device characteristics as the device of Comparative Example 6, which used lithium fluoride, which is often commonly used in normal-structure organic EL devices, as the electron injection layer. Although alkali metals such as lithium fluoride have excellent electron injection properties, they are well known to diffuse into the device as, for example, Li ions, and this diffusion reduces the stability of the organic EL device. Therefore, it is understood that the organic thin film and the material for an organic EL device of the present invention are materials that are free from such problems. 24, it was confirmed that the element in Example 14, in which the second material is inserted between the layer that is a mixed film of the first material + the second material and the metal electrode, like the element in Example 10, has a longer life than the element in Example 12 in which the second material is not inserted. This is believed to be because deterioration due to the interaction between the first material and the inorganic material is prevented even in an element with a normal structure. Furthermore, from the results of FIG. 26, it was confirmed that even in a normal-structure organic EL device using a polymer light-emitting material as the material of the light-emitting layer, the compound (2-2) exhibits characteristics equal to or better than LiF, which is generally used as a material of the electron injection layer.

[0226] As an example of using a pyridine-containing compound as the second material, Example 16, which is the result of using the compound of formula (22), is shown in FIG. 27. It can be seen that light is emitted at a lower voltage than Comparative Example 9, which does not use the compound of formula (2-2), and the luminance-voltage characteristics are equivalent to those of Comparative Example 8, which uses lithium fluoride. From this result, it was confirmed that even when a pyridine-containing compound is used as the second material, by using the hexahydropyrimidopyrimidine compound represented by general formula (1) of the present invention, an element can be driven at a low voltage. Therefore, it is possible to realize an organic EL element that can operate at a low drive voltage without using an alkali metal.

[0227] As an example of using a triazine derivative as the second material, Example 17, which is the result of using the compound of formula (23), emits light at a lower voltage than Comparative Example 10, which uses lithium fluoride, and Comparative Example 11, which does not use the compound of formula (2-2). From this result, it was confirmed that even when a triazine derivative is used as the second material, a device that operates at a low voltage can be obtained by using the hexahydropyrimidopyrimidine compound represented by general formula (1) of the present invention. It is also found that the hexahydropyrimidopyrimidine compound has superior electron injection properties compared to lithium fluoride.

[0228] As an example of using a compound having a heterocycle containing a carbonyl group as the second material, Example 18, which is the result of using the compound of formula (24), emits light at a lower voltage than Comparative Example 12, which uses lithium fluoride, and Comparative Example 13, which does not use the compound of formula (2-2). From this result, it was confirmed that even when a compound having a heterocycle containing a carbonyl group is used as the second material, a device that operates at a low voltage can be obtained by using the hexahydropyrimidopyrimidine compound represented by general formula (1) of the present invention. It is also found that the hexahydropyrimidopyrimidine compound has superior electron injection properties compared to lithium fluoride.

[0229] As an example of using a phenanthroline derivative as the second material, Example 19, which shows the results of using the compound of formula (25), emits light at a lower voltage than Comparative Example 15, which does not use the compound of formula (2-2), as shown in Figure 30. This result confirms that even when a phenanthroline derivative is used as the second material, a device that operates at a low voltage can be obtained by using the hexahydropyrimidopyrimidine compound represented by general formula (1) of the present invention.

[0230] As for Example 20, which is a result of using the compound of formula (26) as the second material, the results of FIG. 31 and FIG. 32 confirmed that the device of Example 20 has a long life while having the same level of device characteristics as the device of Comparative Example 14, which uses lithium fluoride, which is often commonly used in organic EL devices with a normal structure, as the electron injection layer. Furthermore, the results of FIG. 33 confirm that the life is significantly different at high temperatures (85°C). From these results, it is well known that although alkali metals such as lithium fluoride have excellent electron injection properties, they diffuse into the device as Li ions, for example, and this diffusion reduces the stability of the organic EL device. Therefore, it can be seen that the organic thin film and the material for organic EL devices of the present invention are materials that are free from such problems. Furthermore, it is thought that the diffusion of Li ions is strong at high temperatures, and it can be seen that the organic thin film and the material for organic EL devices of the present invention have high resistance at high temperatures.

[0231] As shown in FIG. 34, which shows the luminance-voltage characteristics of the elements of Examples 21 and 22 and Comparative Example 16, the driving voltage is high in Comparative Example 16 because it is difficult to inject electrons from lithium fluoride into DIC-TRZ, whereas in Example 21, electrons are efficiently injected and operation is possible at a low driving voltage. Furthermore, it is also seen that in Example 22, in which the hole transport layer is DIC-TRZ, which is the emitting layer host, operation is possible at a driving voltage equivalent to that of Example 21. In this way, by using a material with excellent electron injection properties, it is possible to simplify the structure of the organic EL element and reduce the number of necessary materials.

[0232] As shown in Figure 35, which shows the luminance-voltage characteristics of Example 23 and Comparative Example 17, which are organic EL elements whose light-emitting layers are composed of one type of material, it is understood that in Comparative Example 17, the driving voltage is high because it is difficult to inject electrons from lithium quinoline to CzDBA, whereas in Example 23, electrons are efficiently injected and operation is possible at a low driving voltage. In this way, by using a material with excellent electron injection properties, it is possible to simplify the structure of the organic EL element and reduce the number of necessary materials.

[0233] 36 shows the results of measuring the luminance-voltage characteristics of the organic EL element of Example 24, which uses the compound represented by formula (2-11) as the first material (electron injection layer 5), and the organic EL element of Comparative Example 18, which does not use the first material (electron injection layer 5), and the element of Example 24, which uses the compound of formula (2-11) as the material of the electron injection layer (first material), emits light at a lower voltage than the element of Comparative Example 18, which does not use the first material. From this result, it was confirmed that the use of the compound of formula (2-11) results in an element that operates at a lower voltage.

[0234] 37, which shows the results of measuring the luminance-voltage characteristics of the devices of Examples 25 and 26 and Comparative Example 19, the devices of Examples 25 and 26, which used the compounds of Formula (2-30) and Formula (2-31) as the material (first material) of the electron injection layer, emit light at a lower voltage than the device of Comparative Example 19, which used only the boron-containing compound represented by Formula (4). From this result, it was confirmed that the use of the compounds of Formula (2-30) and Formula (2-31) results in devices that can be driven at a lower voltage. [Explanation of symbols]

[0235] 1: organic EL element, 2: substrate, 3: cathode (cathode 2), 3': cathode 1, 4: oxide layer, 5: electron injection layer, 6: light-emitting layer, 7: hole transport layer, 8: hole injection layer, 9: anode, 10: electron transport layer.

Claims

1. An organic thin film characterized in that it is a single film containing a first material, which is a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), and a second material that transports electrons, or a laminated film of a film containing the first material and a film containing the second material. 【Chemistry 1】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring, and n is an integer of 2 or 3.

2. The organic thin film according to claim 1 , wherein the first material is a hexahydropyrimidopyrimidine compound represented by general formula (1) in which n is 2 or 3.

3. A laminated film comprising an oxide layer and a layer of the organic thin film according to claim 1 or 2 formed on the oxide layer.

4. 13. An organic electroluminescence element having a light-emitting layer between a cathode and an anode, the organic thin film according to claim 1 or 2 or the laminated film according to claim 3 being disposed between the cathode and the light-emitting layer.

5. 5. The organic electroluminescence device according to claim 4, further comprising an inorganic oxide layer between the cathode and the organic thin film.

6. 6. The organic electroluminescence element according to claim 4, further comprising a laminated film including a film containing the first material and the second material and a film containing the second material, between the cathode and the light-emitting layer.

7. 7. The organic electroluminescence element according to claim 6, further comprising a layer containing the second material between the light-emitting layer and the film containing the first material and the second material.

8. 7. The organic electroluminescence element according to claim 6, further comprising a layer containing the second material between the cathode and the film containing the first material and the second material.

9. 9. The organic electroluminescence element according to claim 4, further comprising a layer containing the second material between the anode and the light-emitting layer.

10. 10. The organic electroluminescence device according to claim 4, wherein the light-emitting layer contains the second material.

11. A material for an organic electroluminescence device, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1): 【Chemistry 2】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring and n is 3.

12. 12. An organic electroluminescence element having a light-emitting layer between a cathode and an anode, the organic electroluminescence element comprising a layer containing the material for organic electroluminescence elements according to claim 11 between the cathode and the anode.

13. 13. The organic electroluminescence device according to claim 12, further comprising a layer containing the material for an organic electroluminescence device according to claim 11 between the cathode and the light-emitting layer.

14. 14. The organic electroluminescence device according to claim 12, further comprising an inorganic oxide layer between the cathode and the layer containing the material for an organic electroluminescence device according to claim 11.

15. A display device comprising the organic electroluminescence element according to any one of claims 4 to 10 and 12 to 14.

16. A lighting device comprising the organic electroluminescence element according to any one of claims 4 to 10 and 12 to 14.

17. A material for an organic thin-film solar cell, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1): 【Chemistry 3】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring and n is 3.

18. 18. An organic thin-film solar cell comprising any one of the organic thin-film according to claim 1 or 2, the laminated film according to claim 3, or a layer containing the material for organic thin-film solar cells according to claim 17.

19. A material for a photoelectric conversion element, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1): 【Chemistry 4】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring and n is 3.

20. A photoelectric conversion element comprising any one of the organic thin film according to claim 1 or 2, the laminated film according to claim 3, and a layer containing the material for photoelectric conversion elements according to claim 19.

21. A material for a thin film transistor, comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1): 【Chemistry 5】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring and n is 3.

22. A thin film transistor comprising any one of the organic thin film according to claim 1 or 2, the laminated film according to claim 3, and a layer containing the material for thin film transistors according to claim 21.

23. A coating composition comprising a first material which is a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), and a second material which transports electrons. 【Chemistry 6】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring and n is 3.

24. A coating composition comprising a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1): 【Chemistry 7】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring and n is 3.

25. A method for producing an organic thin film, comprising the steps of: forming, on a surface to be formed, a single film containing a first material, which is a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1), and a second material that transports electrons; or forming, in order, a film containing the first material and a film containing the second material on a surface to be formed. 【Chemistry 8】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring, and n is an integer of 2 or 3.

26. A method for producing an organic thin film, comprising the step of forming a film containing a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (1) on a surface containing a second material that transports electrons: 【Chemistry 9】 (In general formula (1), R １ , n is R １ is an aromatic hydrocarbon group, an aromatic heterocyclic group (excluding a pyridine ring), an aryl alkylene group, or a group formed by combining two or more aromatic hydrocarbon groups, aromatic heterocyclic groups, or aryl alkylene groups, and n is an integer of 1 to 4, or R １ is a pyridine ring, and n is an integer of 2 or 3.

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