JP2022097348A - Manufacturing method for organic electroluminescent element, organic electroluminescent element, display device, and lighting device - Google Patents

Abstract

To provide a flexible organic field emitting element with high performance and lower cost, particularly to provide an organic field emitting element with improved drive life and low voltage drive.SOLUTION: An organic field emitting element has at least a pair of electrodes and an organic layer between the electrodes. The organic field emitting element is configured to include, adjacent to the cathode, a metal electron injection layer and an organic electron injection layer, in this order. The metal electron injection layer includes a coordination-bond-enabled metallic element. The organic electron injection layer includes an organic material.SELECTED DRAWING: Figure 1

Description

The present invention relates to an organic electric field emission (hereinafter, electroluminescence may be referred to as "electroluminescence" or "EL") element, a display device, and a lighting device.

The organic EL element is thin, flexible and flexible. Further, a display device using an organic EL element is capable of high-luminance and high-definition display as compared with the liquid crystal display device and the plasma display device which are currently mainstream. Further, the display device using the organic EL element has a wider viewing angle than the liquid crystal display device. Therefore, it is expected that the display device using the organic EL element will be widely used as a display of a television or a mobile phone in the future. Further, the organic EL element is also expected to be used as a lighting device.

The organic EL element is a stack of a cathode, a light emitting layer, and an anode. In an organic EL element, a hole from the anode is used to excite a luminescent organic compound by using the energy at the time of recombination between a hole injected from the anode and an electron injected from the cathode, and a hole from the anode is used to obtain light emission. Since it is important that both injection and electron injection from the cathode are performed smoothly, various materials for the hole injection layer and electron injection layer have been studied recently so that hole injection and electron injection can be performed more smoothly. As a material for an electron injection layer that can be applied, an organic electroluminescent element having a forward structure using polyethyleneimine or a compound modified with polyethyleneimine has been reported (see Non-Patent Documents 1 to 3).
Similarly, regarding a phenanthroline derivative having a nitrogen atom, it is possible to promote electron emission from the metal atom by its high coordination ability with the metal ion, and to greatly lower the electron injection barrier at the electrode-organic layer interface. It has been reported in No. 6 to that the use of a phenanthroline derivative between the electrode and the organic layer improves the electron injection ability. Further, as the material of the electron injection layer, a compound having a structure in which an amino group containing a nitrogen atom is directly bonded to a group derived from an electron transporting compound or an organic material having an acid dissociation constant pKa of 1 or more is used. The organic EL element used is disclosed (see Patent Documents 1 to 3).
By the way, an organic electroluminescent device in which the layer between the cathode and the anode is entirely made of an organic compound is liable to be deteriorated by oxygen or water in principle, and strict sealing is indispensable to prevent their invasion. This complicates the manufacturing process of the organic electroluminescent device and hinders the way to a flexible device.
On the other hand, an organic-inorganic hybrid electroluminescent device (HOILED device) has been proposed, in which a part of the layer between the cathode and the anode is formed with an inverted structure in which an inorganic oxide is arranged and the cathode is arranged on the substrate side. (See Patent Document 4). In this device, by changing the hole transport layer and the electron transport layer to inorganic oxides, it has become possible to use FTO and ITO, which are conductive oxide electrodes, as a cathode, and gold as an anode. This means that there are no restrictions on the electrodes from the viewpoint of device drive. As a result, it is no longer necessary to use metals with a small work function, such as alkali metals and alkali metal compounds, and it is possible to emit light without strict sealing, which greatly contributes to flexible devices. This HOILED element is expected to develop as a candidate for a reverse-structured organic EL element.

JP-A-2017-157743 Japanese Unexamined Patent Publication No. 2019-176093 Japanese Unexamined Patent Publication No. 2019-179863 Japanese Unexamined Patent Publication No. 2009-70954

3 outside Tao Xiong "Applied Physics Letters" Vol. 93, 2008, pp123310-1 21 people from Yinhua Zhou, "Science" No. 336, 2012, pp327 6 people outside Jianshan Chen "Journal of Materials Chemistry" 2012, Vol. 22, pp5164 Hiroyuki Yoshida "Journal of Physical Chemistry (J. Phys. Chem. C201511943432459-24464)", Vol. 119, 2015, p24459 Zhengyang Bin, 7 outsiders "Nature Communications", Volume 10, 2019, p866 Hirohiko Fukagawa, 8 outsiders, "Nature Communications", Vol. 11, 2020, p1 Herbert B Mickelson, "(J. Appl. Phys.)", Vol. 48, 1977, p4729.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a flexible organic electroluminescent device having higher characteristics and lower cost. In particular, there is a demand for improvement in drive life and driving at a low voltage, which are problems of an organic electroluminescent device, and the invention has been made to solve these problems.

The present inventors have, as a material used for the electron injection layer of an organic electric field light emitting element, an organic material having a coordinating site such as a multi-position coordinating organic material having an electron-donating nitrogen atom in a heterocycle. Is used, and the study focuses on the metal species to which it is coordinated. Further, by using a metal having a large work function as the metal element, consideration is given to atmospheric stability and a flexible element is realized. As a result, it was found that by providing the metal layer for the coordination reaction on the cathode layer, the organic electroluminescent device has a longer life than the existing oxide. The mechanism is considered to be that the metal layer has denser coordination bonds than the oxide layer, so that the injection barrier can be strongly and uniformly reduced, and oxygen and water invading from the outside can be reduced. ..

That is, the cathode of the organic electric field light emitting element in the present invention may be made of any material, that is, a material having a necessary function can be selected, for example, an atmospherically stable and transparent material can be selected, and for electron injection. If a thin metal atom layer (metal electron injection layer) capable of coordinating reaction is prepared on the cathode, and an organic layer (organic electron injection layer) made of an organic substance serving as a opposing ligand is prepared directly above the metal atom layer. good. At this time, the metal electron injection layer does not depend on the work function and is limited only to the coordination ability, so that a metal species stable to the atmosphere can be selected. From this, when the above-mentioned degree of freedom in selecting the cathode material is taken into consideration, it is possible to manufacture the device with the cathode and the electron injection layer, which are most susceptible to deterioration of water and oxygen in the organic electroluminescent device, as a structure stable to the atmosphere.

The present invention has been completed based on the above findings, and the gist thereof is as follows.
[1] An organic electric field light emitting element having at least a pair of electrodes and an organic layer between them, and the metal element and the organic material which can be coordinated and bonded adjacent to the cathode are contained in the metal layer and the organic material layer, respectively. , A metal electron injection layer, and an organic material layer in this order.
[2] The organic electric field light emitting element according to [1], wherein the work function of all the metal species contained in the metal electron injection layer is 4.0 eV or more. [3] The metal electron injection layer is made of zinc. The organic electric field light emitting element according to [1] and [2], which comprises at least one selected from the group consisting of copper and aluminum [4] The thickness of the metal electron injection layer is 5 nm or less. [1] to [3] The organic electric field light emitting element according to [1] to [4] The organic electric field light emitting element according to [1] to [4], wherein the work function of the cathode is 4.0 eV or more. ..
[6] The organic electroluminescent device according to [1] to [5], wherein the cathode is on a substrate.
[7] The organic electroluminescent device according to [1] to [3] and [5], [6], wherein the metal electron injection layer is made by mixing with a cathode constituent material.
[8] A display device including the organic electroluminescent device according to any one of [1] to [7].
[9] A lighting device comprising the organic electroluminescent element according to any one of [1] to [7].
[10] An organic electric field light emitting element having at least a pair of electrodes and an organic layer between them, and a metal element and an organic material that can be coordinated and bonded adjacent to the cathode are contained in the metal electron injection layer and the organic electron injection layer, respectively. A method for manufacturing an organic electric field light emitting element, which comprises a metal electron injection layer and an organic electron injection layer in this order.

Since the organic electroluminescent device of the present invention is excellent in atmospheric stability and drive life, it can be used as a flexible organic electroluminescent device as a display device, lighting, and a light source.

It is the schematic which showed the laminated structure of the organic electroluminescent element of this invention. It is the schematic which showed the laminated structure of the organic electroluminescent element produced in Example 1. FIG. It is a schematic diagram which showed the laminated structure of the organic electroluminescent element produced in Example 5. It is a schematic diagram which showed the laminated structure of the organic electroluminescent element produced in Example 9. It is a schematic diagram which showed the laminated structure of the organic electroluminescent element produced in Example 11. It is a schematic diagram which showed the laminated structure of the organic electroluminescent element produced in Example 12. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Example 1. It is a life characteristic of the organic electroluminescent device produced in Example 1. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Example 2. It is the life characteristic of the organic electroluminescent device produced in Example 2. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Example 3. It is the life characteristic of the organic electroluminescent device produced in Example 3. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Example 4. It is the life characteristic of the organic electroluminescent device produced in Example 4. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Comparative Example 1. This is the life characteristic of the organic electroluminescent device manufactured in Comparative Example 1. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Examples 5 and 6 and Comparative Example 2. It is the life characteristic of the organic electroluminescent device produced in Examples 5 and 6 and Comparative Example 2. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Examples 7 and 8 and Comparative Example 3. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Example 9. It is a current density-efficiency characteristic of the organic electroluminescent device produced in Example 9. It is the life characteristic of the organic electroluminescent device produced in Example 9. It is the result of leaving the organic electroluminescent device produced in Example 9 in the atmosphere without sealing, and observing the state of light emission at the initial stage, 22 hours later, and 90 hours later. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Example 10. It is a current density-efficiency characteristic of the organic electroluminescent device produced in Example 10. It is a life characteristic of the organic electroluminescent device produced in Example 10. It is the result of leaving the organic electroluminescent device produced in Example 10 in the atmosphere without sealing, and observing the state of light emission at the initial stage, 22 hours later, and 90 hours later. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Comparative Example 4. This is the current density-efficiency characteristic of the organic electroluminescent device manufactured in Comparative Example 4. This is the life characteristic of the organic electroluminescent device manufactured in Comparative Example 4. This is the result of observing the state of light emission in the initial stage, 22 hours, and 90 hours after the organic electroluminescent device produced in Comparative Example 4 was left in the atmosphere without sealing. It is a voltage-luminance characteristic of the organic electroluminescent device produced in Example 11. It is a current density-efficiency characteristic of the organic electroluminescent device produced in Example 11. It is a life characteristic of the organic electroluminescent device produced in Example 11. It is the result of leaving the organic electroluminescent device produced in Example 11 in the atmosphere without sealing, and observing the state of light emission at the initial stage, after 22 hours, and after 90 hours. This is the result of evaluating the atmospheric stability of the organic electroluminescent device produced in Example 12 by storing it in an environment of 85 ° C. and 85% humidity. This is the result of evaluating the atmospheric stability of the organic electroluminescent device produced in Comparative Example 5 by storing it in an environment of 85 ° C. and 85% humidity.

The present invention will be described in detail below along with the layers of the organic electroluminescent device.
"Organic EL element"
The present invention has an organic electron injection layer having a light emitting layer between the cathode and the anode, and having a metal electron injection layer which is a metal thin film adjacent to the cathode and an organic material which causes a coordination reaction with a metal element of the metal layer. It is an organic electroluminescence element (organic EL element) including a layer in which layers are laminated.
The organic EL element preferably has an inverted structure in which the cathode is on the substrate, but may have a forward structure in which the anode is arranged on the substrate. Further, it may be a bottom emission that extracts light from the substrate side, or a top emission that extracts light from the upper part of the substrate.

Next, the organic EL device of the present invention will be described in detail with reference to an example.
FIG. 1 is a schematic cross-sectional view for explaining an example of the organic EL device of the present invention. Here, the structure of the reverse structure is shown. The organic EL element 1 of the present embodiment shown in FIG. 1 has a light emitting layer 8 between the cathode 3 and the anode 11. In the organic EL element 1 shown in FIG. 1, the metal electron injection layer 5 and the organic electron injection layer 6, which are the configurations of the present invention, are adjacent to each other between the cathode 3 and the light emitting layer 8. Further, it has an electron transport layer 7 and a hole blocking layer 12 as needed. A hole transport layer 9 and a hole injection layer 10 are provided between the light emitting layer 8 and the anode 11.

In the present embodiment, the organic EL element 1 having the reverse structure will be described as an example, but the organic EL element of the present invention has a forward structure in which an anode is arranged between the substrate and the light emitting layer. May be good. Even when the organic EL device of the present invention has a forward structure, it has a laminated structure in which the organic electron injection layer and the metal electron injection layer are in contact with each other between the cathode and the light emitting layer, as in the case of the reverse structure. As another example of the configuration of the organic EL element of the present invention, the configurations shown in FIGS. 2 to 6 can be mentioned.
The material, thickness, and sealing of each layer constituting the organic EL element 1 described below are the same for the organic EL element having a forward structure, except for the materials of the cathode and the anode, which will be described later. Only the top emission of the reverse structure is not limited in the film thickness of the metal electron injection layer described later, and any thickness may be used.

"substrate"
Examples of the material of the substrate 2 include a resin material and a glass material.
Examples of the resin material used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyether sulfone, polymethylmethacrylate, polycarbonate, polyarylate and the like. When a resin material is used as the material of the substrate 2, the organic EL element 1 having excellent flexibility can be obtained, which is preferable.
Examples of the glass material used for the substrate 2 include quartz glass and soda glass.

When the organic EL element 1 is a bottom emission type, a transparent substrate is used as the material of the substrate 2.
When the organic EL element 1 is 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 the opaque substrate include a substrate made of a ceramic material such as alumina, a substrate having an oxide film (insulating film) formed on the surface of a metal plate such as stainless steel, and a substrate made of a resin material.

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

"cathode"
The cathode 3 is formed in direct contact with the substrate 2.
As the material of the cathode 3, a material having a work function of 4.0 eV or more is preferable, and for example, ITO (indium tin oxide), IZO (zinc indium oxide), FTO (tin fluorine oxide), In ₃ O ₃ , SnO ₂ , Examples thereof include conductive materials of oxides such as Sb-containing SnO ₂ and Al-containing ZnO, and silver or silver alloys. Among these, it is preferable to use ITO, IZO, FTO, and silver as the material of the cathode 3.
The average thickness of the cathode 3 is not particularly limited, but is preferably 10 to 500 nm, more preferably 100 to 200 nm. For silver, it is preferably 5 to 40 nm, more preferably 10 to 20 nm.
The average thickness of the cathode 3 can be measured by a stylus type step meter and spectroscopic ellipsometry.
These materials can be used as the material of the anode when the organic EL element of the present invention has a forward structure in which the anode is arranged between the substrate and the light emitting layer. In that case, the average thickness of the anode is preferably the same as that of the cathode 3.
The work function is based on the value described in Non-Patent Document 7.

"Metal electron injection layer"
Since the metal electron injection layer 5 is a layer composed of a metal element that is positioned as the central metal of the metal complex when the material contained in the organic electron injection layer is used as a ligand, the metal electron injection layer 5 may be a thin film as a function. For bottom emissions, transparency is required, so it is preferably 0.1 to 5 nm, and more preferably 0.5 to 2 nm. For top emissions, transparency is not required and there is no limit to the thickness.
The average thickness of the metal electron injection layer 5 can be measured by a stylus type step meter and spectroscopic ellipsometry.
The material contained in the metal electron injection layer 5 may be a simple substance of a metal species having a coordinating ability, but from the viewpoint of atmospheric stability, a material having a work function of 4.0 eV or more is preferable.
The metal electron injection layer 5 is a metal layer of one type of metal, a layer in which two or more types of metal are mixed, a layer composed of one type of metal, or a layer in which one or both are laminated, or two or more types. It may be any layer in which simple substances of metal are mixed. Further, the present metal electron injection layer may also serve as a cathode.
Metal elements forming the metal electron injection layer 5 include copper, nickel, palladium, platinum, gold, cobalt, zinc, aluminum, chromium, manganese, iron, tin, indium, titanium, zirconium, vanadium, niobium, tantalum, and molybdenum. , Tungsten, indium, gallium, cadmium.
The work function is based on the value described in Non-Patent Document 7.
When the metal electron injection layer 5 includes a layer in which two or more kinds of metal elements are mixed, it is preferable that at least one of the metal elements constituting the metal is a layer of any one of aluminum, zinc, and copper.
When the metal electron injection layer 5 is a layer made of one kind of simple metal, it is preferably a layer made of a metal selected from the group consisting of aluminum, zinc, and copper.

"Organic electron injection layer"
The organic electron injection layer 6 improves electron injection by forming a complex with the metal electron injection layer 5. The organic electron injection layer 6 may be any organic material having a coordination ability. Among them, a compound having a substituent having a nitrogen atom is preferable, and a compound having a condensed ring structure of a heterocycle having a nitrogen atom is more preferable. For example, examples of the organic material contained in the organic electron injection layer of the present invention include compounds having a structure represented by the following general formula (1).

(In the general formula (1), X ¹ and X ² represent a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have the same or different substituents, and L represents a direct bond. Or, it represents a linking group of p-value. N ¹ represents a number of 0 or 1, p represents a number of 1 to 4. q represents a number of 0 or 1, and when p is 1, q represents. Is 0. R ¹ to R ³ represent the same or different monovalent substituents. M ¹ to m ³ represent the same or different numbers 0 to 3. R ¹ to R ³ May be bonded to X ¹ and X ² to form a ring structure. When there are a plurality of R ^{1, a plurality of R 1 may} be bonded to form a ring structure. R ² , R. The same applies to ^3. )

X ¹ and X ² in the above general formula (1) represent a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have the same or different substituents.
Examples of the divalent linking group include a divalent hydrocarbon group and a group in which a part of the carbon atom of the hydrocarbon group is replaced with a hetero atom of any one of a nitrogen atom, an oxygen atom and a sulfur atom.
The hydrocarbon group preferably has 1 to 6 carbon atoms, and more preferably 1, 2, or 6 carbon atoms.
The hydrocarbon group may be linear, branched, cyclic or a combination thereof.
The divalent hydrocarbon group may be an alkylene group which is a saturated hydrocarbon group, or an unsaturated hydrocarbon group such as an alkenylene group or an alkynylene group.
As the divalent hydrocarbon group, specifically, those represented by the following formulas (2-1) to (2-4) are preferable. R in (2-1) to (2-4) in the following formula represents a substituent. Specific examples of the substituents in X ¹ and X ² , including R in (2-1) to (2-4), include the same groups as the monovalent substituents in R ¹ to R ³ described later. ..

L in the above general formula (1) represents a direct bond or a linking group having a p-value. It should be noted that L is a direct bond only when p is 2.
The p-valent linking group includes a nitrogen atom, an oxygen atom, a sulfur atom, and a carbon atom, as well as a hydrocarbon group and a part of the carbon atom of the hydrocarbon group is a hetero atom of either a nitrogen atom, an oxygen atom, or a sulfur atom. Examples thereof include groups formed by removing p hydrogen atoms from the groups substituted with.
When the p-valent linking group has a carbon atom, one having 1 to 30 carbon atoms is preferable. More preferably, it has 1 to 20 carbon atoms.
The hydrocarbon group may be linear, branched, cyclic or a combination thereof.
The hydrocarbon group may be any of a saturated hydrocarbon group, an unsaturated hydrocarbon group and an aromatic hydrocarbon group.
Examples of the aromatic hydrocarbon group include groups formed by removing a hydrogen atom from aromatic compounds such as a benzene ring, a naphthalene ring, an anthracene ring, a tetracene ring, a pentacene ring, a triphenylene ring, a pyrene ring, a fluorene ring, and an inden ring. ..

R ¹ to R ³ in the above general formula (1) represent the same or different monovalent substituents.
The monovalent substituent includes a fluorine atom; a haloalkyl group such as a fluoromethyl group, a difluoromethyl group and a trifluoromethyl group; a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group and a tert-butyl group. Linear or branched alkyl group having 1 to 20 carbon atoms; cyclic alkyl group having 5 to 7 carbon atoms such as cyclopentyl group, cyclohexyl group, cycloheptyl group; methoxy group, ethoxy group, propoxy group, isopropoxy. A linear or branched alkoxy group having 1 to 20 carbon atoms such as a group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group; a nitro group; a cyano group; Group; Alkylamino group having an alkyl group having 1 to 10 carbon atoms such as methylamino group, ethylamino group, dimethylamino group and diethylamino group; cyclic amino group such as pyrrolidino group, piperidino group and morpholino group; diphenylamino group, Diarylamino group such as carbazolyl group; acyl group such as acetyl group, propionyl group, butyryl group; alkenyl group having 2 to 30 carbon atoms such as styryl group; halogen atom such as fluorine atom or alkyl group having 1 to 20 carbon atoms, An aryl group having 5 to 20 carbon atoms which may be substituted with an alkoxy group, an amino group or the like (specific examples of the aryl group are the same as the above aromatic hydrocarbon group); a halogen atom such as a fluorine atom or 1 to 1 carbon atoms. A heterocyclic group containing any one or more of a nitrogen atom, a sulfur atom and an oxygen atom having 4 to 40 carbon atoms which may be substituted with 20 alkyl groups, alkoxy groups, amino groups and the like (the heterocyclic group is 1). It may be composed of only one ring, a compound composed of only one aromatic heterocycle may be a compound in which a plurality of carbon atoms are directly bonded to each other, or may be a fused heterocyclic group. Specific examples of the heterocyclic group include a thiophene ring, a furan ring, a pyrrole ring, a benzothiophene ring, a benzofuran ring, an indol ring, a dibenzothiophene ring, a dibenzofuran ring, a carbazole ring, a thiazole ring, a benzothiazole ring, an oxazole ring and a benzoxazole ring. Specific examples of aromatic heterocyclic groups such as a ring, an imidazole ring, a benzoimidazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxalin ring, a benzothiasiazol ring, and a phenanthridine ring. Examples are included.); Examples include an ester group, a thioether group, and a group formed by combining these. These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring or the like.

The compound represented by the general formula (1) includes a compound having only one phenanthroline skeleton and having a structure represented by the following general formula (3), and this compound is also the organic electron injection layer of the present invention. Suitable as a material.

(In the general formula (3), R ⁴ and R ⁵ are the same or different and represent a dialkylamino group or an alkoxy group. M ⁴ and m ⁵ are the same or different and represent a number of 1 or ² . When there are a plurality of R4s, a plurality of ^R4s may be combined to form a ring structure. The ^same applies to R5.)

R ⁴ and R ⁵ in the above general (3) represent the same or different dialkylamino group or alkoxy group.
The dialkylamino group preferably has an alkyl group having 1 to 20 carbon atoms such as a methyl group and an ethyl group. More preferably, it has an alkyl group having 1 to 10 carbon atoms. Further, the two alkyl groups of the dialkylamino group may have the same carbon number or different carbon atoms. Further, an amino group in which two alkyl groups are linked, for example, a cyclic amino group such as a piperidino group, a pyrrolidine group, or a morpholino group is also preferable.
Examples of the alkoxy group include the same as in the case where R ¹ to R ³ in the above general formula (1) are alkoxy groups.

In addition to the compound having only one phenanthroline skeleton, the compounds having a plurality of phenanthroline skeletons as shown in the following formulas (4-1) to (4-4) are also considered to be effective in generating a negative charge.

Further, p in the general formula (1) represents a number of 1 to 4, but is preferably a number of 1 to 3. Specific examples of the compound in which p of the general formula (1) is 1 include compounds represented by the following formulas (5-1) to (5-9).

Although n ¹ in the general formula (1) represents 0 or a number of 1, it is a preferred embodiment of the present invention that the compound represented by the general formula (1) is a compound in which n ¹ is 0. It is one of. Specific examples of the compound in which n ¹ of the general formula (1) is 0 include compounds represented by the above formulas (5-1) to (5-6).

Further, compounds represented by the following formulas (5-10) to (5-65), which are included in the general formula (1) and have a structure similar to the above, are also suitable.

Further, as the material of the organic electron injection layer 6, it is sufficient that a nitrogen atom that can be coordinated is used, and various compounds having a structure represented by the following formulas (5-66) to (5-68) as a skeletal structure can also be used. can. These compounds include compounds having a structure represented by the following formulas (5-66) to (5-68) and substituents having a structure represented by the following formulas (5-66) to (5-68). Contains compounds having. Examples of the substituent include those similar to those of R ¹ to R ³ in the above-mentioned general formula (1), and the number of the substituents may be one or a plurality. In the case of a plurality of substituents, the substituents may be bonded to each other to form a ring structure.

Further, a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (6) can also be used as a material for the organic electron injection layer 6.

(In the general formula (6), R ⁶ is an aromatic hydrocarbon group which may have a substituent, an aromatic heterocyclic group, an arylalkylene group, a 2- to 4-valent chain or cyclic hydrocarbon group, and the like. Alternatively, it represents a group formed by combining two or more of these groups, or a group formed by combining one or two or more of these groups with a nitrogen atom. N ² is an integer of 1 to 4).

The hexahydropyrimidopyrimidine compound having the structure represented by the general formula (6) can be coordinated to the metal species contained in the metal electron injection layer 5, and is at the interface with oxygen or water that invades from the outside. It has been confirmed that it has the effect of hindering the reaction of the element and increasing the atmospheric stability of the element. Further, the dipole generated by interacting with the metal species contained in the metal electron injection layer 5 can improve the electron injection property of the metal electron injection layer 5 as a result.

R ⁶ in the above general formula (6) is an aromatic hydrocarbon group, an aromatic heterocyclic group, an arylalkylene group, a 2- to 4-valent chain or cyclic hydrocarbon group which may have a substituent, or a cyclic hydrocarbon group. , A group formed by combining two or more of these groups, and a group formed by combining one or more of these groups with a nitrogen atom.
As the aromatic hydrocarbon group and the aromatic heterocyclic group, those having 3 to 30 carbon atoms are preferable, those having 4 to 24 carbon atoms are more preferable, and those having 5 to 20 carbon atoms are further preferable.
As the aromatic hydrocarbon group, a compound consisting of only one aromatic ring such as benzene; a compound in which a plurality of aromatic rings such as biphenyl and diphenylbenzene are directly bonded to each other by one carbon atom; naphthalene, anthracene, phenanthrene, pyrene and the like. Examples thereof include a group formed by removing 1 to 4 hydrogen atoms from any of the aromatic rings of the fused ring-type aromatic hydrocarbon compound.
As the aromatic heterocyclic group, a compound consisting of only one aromatic heterocycle such as thiophene, furan, pyrrol, oxazole, oxadiazole, thiazole, thiadiazol, imidazole, pyridine, pyrimidine, pyrazine, and triazine; one of these. Compounds in which a compound consisting only of an aromatic heterocycle is directly bonded to one carbon atom (bipyridine, etc.); quinoline, quinoxalin, benzothiophene, benzothiazole, benzoimidazole, benzoxazole, indol, carbazole, dibenzofuran, dibenzothiophene, Examples thereof include a group formed by removing 1 to 4 hydrogen atoms from any of the aromatic heterocycles of fused ring-type heteroaromatic hydrocarbon compounds such as acrydin and phenanthroline.
Examples of the arylalkylene group include a group in which the above aromatic hydrocarbon group and an alkylene group having 1 to 3 carbon atoms are combined.
As the 2- to 4-valent chain or cyclic hydrocarbon group, those having 1 to 12 carbon atoms are preferable, those having 1 to 6 carbon atoms are more preferable, and those having 1 to 4 carbon atoms are further preferable. The chain hydrocarbon group may be linear or branched.
Further, R ⁶ may be a group formed by combining two or more of the above aromatic hydrocarbon group, aromatic heterocyclic group, arylalkylene group and 2- to tetravalent chain hydrocarbon group.
Further, R ⁶ is a group formed by combining one or more of the above aromatic hydrocarbon group, aromatic heterocyclic group, arylalkylene group and 2- to tetravalent chain hydrocarbon group with a nitrogen atom. May be. Examples of such a group include a trialkylamine such as trimethylamine and a group obtained by removing 1 to 4 hydrogen atoms from triphenylamine.

The aromatic hydrocarbon group, aromatic heterocyclic group, or arylalkylene group may have one or more monovalent substituents.
Examples of the monovalent substituent include those similar to the specific examples of the monovalent substituents of R ¹ to R ³ in the above-mentioned general formula (1).

Although n ² in the above general formula (6) is an integer of 1 to 4, it is preferably 2 or 3.
Specific examples of the hexahydropyrimidopyrimidine compound having the structure represented by the general formula (6) include compounds represented by the following formulas (7-1) to (7-34).

As shown in the following formula (8), the compound represented by the above general formula (6) uses a halogen compound having iodine, bromine, chlorine and fluorine as a raw material and a hexahydropyrimidopyrimidine as a raw material, and a Ullmann coupling reaction. , Buchwald-Hartwig amination reaction, nucleophilic substitution reaction and the like.

In addition to this, as long as it can be used as a ligand, not only a nitrogen atom but also an acetylacetonato derivative in which an oxygen atom is a coordinating element can be mentioned.
The average thickness of the organic electron injection layer 6 is preferably 0.5 to 10 nm, more preferably 1 to 5 nm, and even more preferably 1 to 5 nm.
The average thickness of the organic electron injection layer 6 can be measured by, for example, a stylus type step meter or spectroscopic ellipsometry.
Further, the organic electron injection layer may be mixed with the next layer, the electron transport layer 7.

"Electron transport material"
As the electron transport layer 7, any material that can be usually used as the material of the electron transport layer may be used, and can be used as needed.
Specifically, as the material of the electron transport layer 7, a phosphine oxide derivative such as phenyl-dipyrenylphosphinoxide (POPy ₂ ), Tris-1,3,5- (3'-(pyridine-3''-)- Il) phenyl) pyridine derivatives such as benzene (TmPhPyB), quinoline derivatives such as (2- (3- (9-carbazolyl) phenyl) quinoline (mCQ)), 2-phenyl-4,6-bis (3,) 5-Dipyridylphenyl) Pyrimidine derivatives such as pyrimidine (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as bassofenantroline (BPhen), 2,4-bis (4-biphenyl) -6- (4'-(2-pyridinyl) ) -4-Biphenyl)-[1,3,5] Triazine derivatives such as triazine (MPT), 3-phenyl-4- (1'-naphthyl) -5-phenyl-1,2,4-triazole (TAZ) ), Oxazole derivatives, 2- (4-biphenylyl) -5- (4-tert-butylphenyl-1,3,4-oxadiazol) (PBD) and other oxadiazole derivatives, 2 , 2', 2''-(1,3,5-benzenetriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBI) imidazole derivatives, naphthalene-1,4,5,5 Arocyclic carboxylic acid anhydrides such as 8-tetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, N, N'-dimethyl-3,4,9,10-perylenetetra It has an aromatic ring imide compound such as carboxylic sandiimide, an isoindigo derivative, a 2,5-dihydropyrrolo [3,4-c] pyrrol-1,4-dione derivative (diketopyrrolopyrrole), and a carbonyl group such as tolucsenone. Compounds, 1,2,5-thiaidazole derivatives such as naphtho [1,2-c: 5,6-c'] bis [1,2,5] thiazazole, benzo [c] [1,2,5] thiaxazole. , Bis [2- (2-hydroxyphenyl) benzothiazolato] Zinc (Zn (BTZ) ₂ ), Tris (8-hydroxyquinolinato) Aluminum (Alq ₃ ), etc. Various metal complexes, 2,5-bis ( Tris (2,4,6), an organic silane derivative typified by a syrol derivative such as 6'-(2', 2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilol (PyPySPyPy) -Trimethyl-3- ( Pyridine-3-yl) phenyl) borane (3TPYMB), boron-containing compounds according to Japanese Patent Application No. 2012-228460, Japanese Patent Application 2015-503053, Japanese Patent Application 2015-053872, Japanese Patent Application 2015-0811108 and Japanese Patent Application 2015-0811109. These can be mentioned, and one or more of these can be used.
In addition to the above materials, a π-electron excess system containing an aromatic hydrocarbon compound which is various hydrocarbon compounds having an aromatic ring, a compound having a nitrogen-boron bond, and an aromatic ring such as a pyrrole ring, a furan ring, and a thiophene ring. Heteroaromatic compounds and compounds containing a silol ring can also be used.
Among these materials for the electron transport layer 7, it is particularly preferable to use a phosphine oxide derivative such as POPy ₂ , a metal complex such as Alq ₃ , and a pyridine derivative such as TmPhPyB.

When the material of the organic electron injecting layer 6 of the organic EL element of the present invention and the electron transporting material are mixed and used, the electron transporting layer 7 may not be present. Further, a part of these may be used as a hole blocking material to form a hole blocking layer. Separately, as the material of the hole blocking layer, any material that can be usually used may be used, and can be used as needed.
The average thickness of the electron transport layer 7 is not particularly limited, but is preferably 10 to 150 nm, more preferably 20 to 100 nm.
The average thickness of the electron transport layer 7 can be measured by a stylus type step meter and spectroscopic ellipsometry.

"Light emitting layer"
As the material for forming the light emitting layer 8, any material that can be usually used as the material for the light emitting layer 8 may be used, or these may be mixed and used. For example, as the light emitting layer 8, bis [2- (2-benzothiazolyl) phenolato] zinc (II) (Zn (BTZ) ₂ ) and tris [1-phenylisoquinoline] iridium (III) (Ir (piq) ₃ ) are used. Can be included.
For example, a tri-coordinated iridium complex having 2,2'-bipyridine-4,4'-dicarboxylic acid as a ligand, factories (2-phenylpyridine) iridium (Ir (ppy) ₃ ), 8-hydroxy. Quinoline Aluminum (Alq ₃ ), Tris (4-Methyl-8 Kinolinolate) Aluminum (III) (Almq ₃ ), 8-Hydroxyquinoline Zinc (Znq ₂ ), (1,10-Phenanthrolin) -Tris- (4,4) 4-Trifluoro-1- (2-thienyl) -butane-1,3-geonate) europium (III) (Eu (TTA) ₃ (phen)), 2,3,7,8,12,13,17, Various metal complexes such as 18-octaethyl-21H, 23H-porfin platinum (II); benzene compounds such as distyrylbenzene (DSB), diaminodistyrylbenzene (DADSB); naphthalenes such as naphthalene and nile red. Compounds; phenanthren-based compounds such as phenanthrene; chrysene, chrysene-based compounds such as 6-nitrochrysene; perylene, N, N'-bis (2,5-di-t-butylphenyl) -3,4,9, Perylene-based compounds such as 10-perylene-di-carboxyimide (BPPC); coronene-based compounds such as coronen; anthracene-based compounds such as anthracene, bisstyrylanthracene; pyrene-based compounds such as pyrene; 4- (di) -Pyranone compounds such as -cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM); aclysine compounds such as aclydin; stelvene compounds such as stilben; 2, 5-Dibenzoxazole A thiophene-based compound such as thiophene; a benzoxazole-based compound such as benzoxazole; a benzoimidazole-based compound such as benzoimidazole; Benzene-based compounds; butadiene-based compounds such as bistylyl (1,4-diphenyl-1,3-butadiene), tetraphenylbutadiene; naphthalimide-based compounds such as naphthalimide; quinoline-based compounds such as quinoline; perinone Perinone-based compounds such as; oxadiazole-based compounds such as oxadiazole; aldazine-based compounds; 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP) Cyclopentadiene compounds such as; quinacridone compounds such as quinacridone, quinacridone red; pyridine compounds such as spirolopyridine and thiadiazolopyridine; 2,2', 7,7'-tetraphenyl-9,9'- Spiro compounds such as spirobifluorene; metallic or non-metal phthalocyanine compounds such as phthalocyanine (H ₂ Pc), copper phthalocyanine; and further, JP-A-2009-155325, JP-A-2011-184430 and Japanese Patent Application Laid-Open No. 2009-155325 Examples thereof include the boron compound material described in 2011-6458.

Further, the material forming the light emitting layer 8 may be a low molecular weight compound or a high molecular weight compound. In the present invention, the small molecule material means a material that is not a polymer material (polymer), and does not necessarily mean an organic compound having a low molecular weight.
The average thickness of the light emitting layer 8 is not particularly limited, but is preferably 10 to 150 nm, more preferably 20 to 100 nm.
The average thickness of the light emitting layer 8 may be measured by a stylus type step meter or may be measured by a crystal oscillator film thickness meter at the time of film formation of the light emitting layer 8.

"Hole transport layer"
As the hole-transporting organic material used for the hole-transporting layer 9, various p-type polymer materials (organic polymers) and various p-type small molecule materials can be used alone or in combination.

Specifically, as the material of the hole transport layer 9, for example, N, N'-di (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α). -NPD), N4, N4'-bis (dibenzo [b, d] thiophene-4-yl) -N4, N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), polyarylamine, fluorene-arylamine Copolymers, Fluorene-Bithiophene Copolymers, Poly (N-vinylcarbazole), Polyvinylpyrene, Polyvinylanthracene, Polythiophene, Polyalkylthiophene, Polyhexylthiophene, Poly (p-phenylenebinylene), Polythienylenebinylene, Pyreneformaldehyde Examples thereof include resins, ethylcarbazole formaldehyde resins or derivatives thereof. The material of these hole transport layers 9 can also be used as a mixture with other compounds. As an example, as a mixture containing polythiophene used as a material for the hole transport layer 9, poly (3,4-ethylenedioxythiophene / styrene sulfonic acid) (PEDOT / PSS) and the like can be mentioned.

The average thickness of the hole transport layer 9 is not particularly limited, but is preferably 10 to 150 nm, more preferably 20 to 100 nm.
The average thickness of the hole transport layer 9 can be measured by, for example, a stylus type step meter or spectroscopic ellipsometry.

"Hole injection layer"
The hole injection layer 10 may be made of an inorganic material or an organic material. Since the inorganic material is more stable than the organic material, it is easy to obtain high resistance to oxygen and water as compared with the case where the organic material is used.

The inorganic material is not particularly limited, and for example, one or more metal oxides such as vanadium oxide (V2 O ₅ ), molybdenum oxide (MoO ₃ ), and ruthenium oxide _{(RuO 2 )} may be used. can.

Organic materials include dipyrazino [2,3-f: 2', 3'-h] quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) and 2,3,5. Use low molecular weight materials such as 6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT: PSS), etc. be able to.

The average thickness of the hole injection layer 10 is not particularly limited, but is preferably 1 to 1000 nm, more preferably 5 to 50 nm.
The average thickness of the hole injection layer 10 can be measured at the time of film formation by a crystal oscillator film thickness meter, a stylus type step meter, and spectroscopic ellipsometry.

"anode"
Examples of the material used for the anode 11 include ITO, IZO, Au, Pt, Ag, Cu, Al, and alloys containing these. Among these, it is preferable to use ITO, IZO, Au, Ag, and Al as the material of the anode 11.

The average thickness of the anode 11 is not particularly limited, but is preferably 10 to 1000 nm, more preferably 30 to 150 nm. Even when an impermeable material is used as the material of the anode 11, 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 11 can be measured by a crystal oscillator film thickness meter at the time of film formation of the anode 11.
When Mg is added to these materials, the organic EL device of the present invention can be used as a cathode material when it has a forward structure. In that case, the average thickness of the cathode is preferably the same as that of the anode 11.

"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 is provided by a sealing container (not shown) having a concave space for accommodating the organic EL element 1 and an adhesive that adheres the edge of the sealing container to the substrate 2. It may be sealed. Further, the organic EL element 1 may be housed in a sealing container and sealed by filling with a sealing material made of an ultraviolet (UV) curable resin or the like. Further, for example, the organic EL element 1 shown in FIG. 1 includes a plate member (not shown) arranged on the anode 11 and a frame member (not shown) arranged along the edge of the plate member on the side facing the anode 11. The sealing member (not shown) may be sealed with an adhesive that adheres between the plate member and the frame member and between the frame member and the substrate 2.

When the organic EL element 1 is sealed using the sealing container or the sealing member, a desiccant that absorbs moisture may be arranged in the sealing container or inside the sealing member. Further, a material that absorbs moisture may be used as the sealing container or the sealing member. Further, a space may be formed in the sealed container or inside the sealing member.

As the material of the sealing container or the sealing member used when sealing the organic EL element 1 shown in FIG. 1, a resin material, a glass material, or the like can be used. 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.

In the organic EL element 1 of the present embodiment, ITO is used as a cathode, a metal thin film having a work function of 4.0 eV or more is used as the metal electron injection layer 5, and the organic electron injection layer 6 is represented by the above general formula (1). When formed using an organic material having the coordinating ability, excellent durability is obtained as compared with the case where, for example, an alkali metal which is an unstable material in the atmosphere is used as the electron injection layer. Be done. Therefore, if the water vapor permeability of the sealing container or the sealing member is on the order of 10 ^-4 to 10 ^-3 (g / m ² / day), the deterioration of the organic EL element 1 can be sufficiently suppressed. Therefore, as a material for the sealing container or the sealing member, it is possible to use a resin material having a water vapor transmittance of about 10 ^-3 order (g / m ² / day) or less, and an organic EL element having excellent flexibility. 1 can be realized.

"Manufacturing method of organic EL element"
Next, as an example of the method for manufacturing the organic EL device of the present invention, the method for manufacturing the organic EL device 1 having the reverse structure shown in FIG. 1 will be described. However, the organic EL device of the present invention may have a conventional forward structure. In that case, for example, it is only necessary to stack the anode and the hole injection layer so that their configurations are reversed, and the film forming method is not particularly limited.
In order to manufacture the organic EL element 1 shown in FIG. 1, first, a cathode 3 is formed on the substrate 2.
The cathode 3 can be formed by a sputtering method, a vacuum vapor deposition method, a sol-gel method, a spray pyrolysis (SPD) method, an atomic layer deposition (ALD) method, a gas phase film formation method, a liquid phase film formation method, or the like. A method of joining metal foils may be used for forming the cathode 3.
Next, the metal electron injection layer 5 is formed on the cathode 3. The metal electron injection layer 5 is formed by using, for example, a vacuum vapor deposition method or the like.
Next, the organic electron injection layer 6 is formed on the metal electron injection layer 5.
The organic electron injection layer 6 is formed by using, for example, a vacuum vapor deposition method or the like.
Next, the electron transport layer 7, the light emitting layer 8, and the hole transport layer 9 are formed on the organic electron injection layer 5 in this order.
The method for forming the electron transport layer 7, the light emitting layer 8, and the hole transport layer 9 is not particularly limited, and conventionally, the method is matched to the characteristics of the materials used for each of the electron transport layer 7, the light emitting layer 8, and the hole transport layer 9. Various known forming methods can be appropriately used.
Next, the hole injection layer 10 and the anode 11 are formed on the hole transport layer 9 in this order. For these layers as well, various conventionally known forming methods can be appropriately used according to the characteristics of the materials used for each.
By the above steps, the organic EL element 1 shown in FIG. 1 is obtained.

"Sealing method"
The organic EL element 1 shown in FIG. 1 can be sealed by using a usual method used for sealing the organic EL element.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" shall mean "mol%".

(Synthesis Example 1)
The compound represented by the following formula (9) was synthesized by the method shown below.

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

(Synthesis Example 2)
The compound represented by the following formula (7-2) was synthesized by the method shown below.

Rac-BINAP (747 mg) and toluene (67 mL) were placed in a 200 mL three-necked flask and heated to 90 ° C. under a nitrogen atmosphere to dissolve them. After allowing to cool to room temperature, palladium acetate (180 mg) was added, and the mixture was stirred at room temperature for 1 hour. To this, 2,6-dibromopyridine (4.74 g), 1,3,4,6,7,8-hexahydro-2H-pyrimid [1,2-a] pyrimidine (6.13 g), KOtBu (6.28 g). ) Was added, and the mixture was heated and stirred at 90 ° C. overnight. After allowing to cool to room temperature, diethyl ether was added, the precipitated solid was filtered off, and the filtrate was concentrated. Acetone was added to the obtained residue, and the precipitated solid was collected by filtration to obtain a compound of the above formula (7-2) (3.7 g, 52.5%).

(Manufacturing of organic electroluminescent device)
(Example 1)
[Step 1] A glass substrate 2 (thickness 0.7 mm) with an ITO electrode layer (cathode 3) was prepared. This substrate was washed with UV ozone for 20 minutes.
[Step 2] Next, in order to form 10 nm of silver as the second cathode layer 3 and 1 nm of zinc as the metal electron injection layer 5, the substrate treated with [Step 1] is introduced into a vacuum apparatus and 5 ×. The pressure was reduced to ^10-5 Pa or less, and a film was formed by a vacuum vapor deposition method.
[Step 3] Next, as the organic electron injection layer 6, a material of the above formula (9), which is a material for an organic electron injection layer, and KHLHEI-02 manufactured by Chemipro Chemical Co., Ltd., which is an electron transport material, are co-deposited to a hole blocking layer at 15 nm. As 12, KHLHS-04 manufactured by Chemipro Chemical Co., Ltd. is 10 nm, KHLHS-03, KHLHS-04 and KHLDG-01 manufactured by Chemipro Chemical Co., Ltd. are co-deposited at 25 nm as the light emitting layer 8, and KHLHS-03 manufactured by Chemipro Chemical Co., Ltd. is 40 nm as the hole transport layer 9. The layers were laminated by a vacuum vapor deposition method so as to have a film thickness.
[Step 4] Next, the hole injection layer 10 was formed on the hole transport layer 9. Here, molybdenum oxide was formed by a vacuum vapor deposition method, which is a vapor deposition method, so as to have a film thickness of 10 nm.
[Step 5] Next, as a final step, the anode 11 was formed on the hole injection layer 10. Here, aluminum was formed by a vacuum vapor deposition method so as to have a film thickness of 100 nm.
By the above steps [step 1] to [step 5], an organic electroluminescent device having the configuration shown in FIG. 2 was manufactured.
[Step 6] The characteristics (voltage-luminance characteristics and lifetime characteristics) of the organic electroluminescent device were evaluated by the following measurement of the light emitting characteristics of the organic electroluminescent device. The results are shown in FIGS. 7 and 8, respectively.

<Measurement of light emission characteristics of organic electroluminescent device>
A voltage was applied to the element and a current was measured by a "2400 type source meter" manufactured by Keithley. The emission brightness was measured by "BM-7" manufactured by Topcon. The measurement was performed under nitrogen.

<Measurement of device life of organic electroluminescent device>
Luminance deterioration was measured under a constant current in a nitrogen atmosphere.

(Example 2)
An organic electroluminescent device was produced in the same manner as in Example 1 except that zinc in [Step 2] of Example 1 was replaced with copper of 1 nm. As [Step 6], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 1 are shown in FIGS. 9 and 10, respectively.

(Example 3)
An organic electroluminescent device was produced in the same manner as in Example 1 except that zinc in [Step 2] of Example 1 was replaced with aluminum of 1 nm. As [Step 6], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 1 are shown in FIGS. 11 and 12, respectively.

(Example 4)
An organic electroluminescent device was produced in the same manner as in Example 1 except that [Step 2] of Example 1 was replaced with the following [Step 2-5]. As [Step 6], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 1 are shown in FIGS. 13 and 14, respectively.
[Step 2-5] Next, in order to form a silver-zinc co-deposited film of 11 nm as the metal electron injection layer 4 in which silver and zinc, which are the second cathode materials, are mixed, the substrate subjected to the treatment of [Step 1] was performed. Was introduced into a vacuum apparatus, the pressure was reduced to 5 × 10 ^-5 Pa or less, and a film was formed by a vacuum vapor deposition method.

(Comparative Example 1)
An organic electroluminescent device was produced in the same manner as in Example 1 except that [Step 2] of Example 1 was replaced with the following [Step 2-51]. As [Step 6], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 1 are shown in FIGS. 15 and 16, respectively.
[Step 2-51] This substrate was fixed to a substrate holder of a Miratron sputtering apparatus having a zinc metal target. After reducing the pressure to about 5 × 10 ^-5 Pa, sputtering was performed with argon and oxygen introduced to prepare a zinc oxide layer having a film thickness of about 2 nm, which is a metal oxide, as a substitute for the metal electron injection layer 5.
Examples 1 to 4 have higher brightness and longer life at the same voltage than Comparative Example 1 having the metal oxide layer 4 without the metal electron injection layer 5, and are effective. Is recognized.

(Example 5)
[Step 1] As the substrate 2, a commercially available transparent glass substrate having an average thickness of 0.7 mm and having an electrode (cathode 3) patterned with a width of 3 mm made of ITO having a thickness of 150 nm was prepared. Then, the substrate 2 having the cathode 3 was ultrasonically washed in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. Then, the substrate 2 having the cathode 3 was taken out from the isopropanol, dried by a nitrogen blow, and washed with UV ozone for 20 minutes.
[Step 2] The substrate 2 on which the cathode 3 washed in [Step 1] was formed was fixed to a substrate holder of a Miratron sputtering apparatus having a zinc metal target. After reducing the pressure in the chamber of the sputtering apparatus to a pressure of about 1 × 10 ^-4 Pa, sputtering is performed with argon and oxygen introduced, and a zinc oxide layer having a film thickness of about 3 nm is placed on the cathode 3 of the substrate 2. A metal oxide layer 4) was prepared. When the zinc oxide layer was produced, zinc oxide was prevented from being formed on a part of the ITO electrode (cathode 3) in order to take out the electrode. The substrate 2 on which the metal oxide layer 4 was formed was annealed at 400 ° C. for 1 hour in the atmosphere.
[Step 3] Aluminum was formed into a 2 nm film as the metal electron injection layer 5 by a vacuum thin-film deposition method using resistance heating.
[Step 4] After forming the metal electron injection layer 5, an organic electron injection layer 6 having a thickness of 1 nm made of the compound of the formula (7-2) was formed by a vacuum vapor deposition method.
[Step 5] Subsequently, an electron transport layer having a thickness of 10 nm made of bis [2- (2-benzothiazolyl) phenolato] zinc (II) (Zn (BTZ) ₂ ) represented by the following formula (10) by a vacuum vapor deposition method. 7 was formed. Subsequently, a light emitting layer 8 is formed by co-depositing 20 nm using Zn (BTZ) ₂ as a host and tris [1-phenylisoquinoline] iridium (III) (Ir (piq) ₃ ) represented by the following formula (11) as a dopant. Filmed. At this time, the doping concentration was such that Ir (piq) ₃ was 6% by mass with respect to the entire light emitting layer 8. Next, on the substrate 2 formed up to the light emitting layer 8, N, N'-di (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4, represented by the following formula (12), A 50 nm film of 4'-diamine (α-NPD) was formed to form a hole transport layer 9. Further, a 10 nm film of 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) represented by the following formula (13) is formed. Then, the hole injection layer 10 was formed. Next, an anode 11 having a film thickness of 100 nm made of aluminum was formed by a vacuum vapor deposition method on the substrate 2 on which the hole injection layer 10 was formed.
The anode 11 was formed by using a stainless steel vapor deposition mask so that the vapor deposition surface had a band shape with a width of 3 mm, and the light emitting area of the produced organic EL element was 9 mm ² .
[Step 6] Next, the substrate 2 on which each layer up to the anode 11 is formed is housed in a glass cap (sealing container) having a concave space, and is filled with a sealing material made of an ultraviolet (UV) curable resin. It was sealed to produce an organic electroluminescent device having the configuration shown in FIG.
[Step 7] The characteristics (voltage-luminance characteristics and lifetime characteristics) of the organic electroluminescent device were evaluated by the following measurement of the light emitting characteristics of the organic electroluminescent device. The results are shown in FIGS. 17 and 18, respectively.

<Measurement of light emission characteristics of organic electroluminescent device>
A voltage was applied using a "2400 type source meter" manufactured by Keithley, and the brightness was measured using a "LS-100" manufactured by Konica Minolta, and the relationship between the applied voltage and the brightness was investigated.

<Measurement of device life of organic electroluminescent device>
The relationship between the elapsed time from the start of driving at a constant current and the relative brightness was investigated by an "organic EL life measuring device" manufactured by EHC. Specifically, the voltage is automatically adjusted so that a constant current flows through the organic electroluminescent element, and the relative brightness is measured with respect to the elapsed time from the start of driving at a constant current (luminance meter manufactured by Konica Minolta). (According to (LS-110)) was performed. The current value was set for each organic electroluminescent element so that the brightness at the start of measurement was 1000 cd / m ² .

(Example 6)
An organic electroluminescent device of Example 6 was obtained in the same manner as in Example 5 except that the metal oxide layer 4 was not formed except for [Step 2] of Example 5. As [Step 7], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 5 are shown in FIGS. 17 and 18, respectively.

(Comparative Example 2)
An organic electroluminescent device of Comparative Example 2 was obtained in the same manner as in Example 5 except that the metal electron injection layer 5 was not formed except in [Step 3] of Example 5. As [Step 7], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 5 are shown in FIGS. 17 and 18, respectively.

As can be seen from FIG. 17, Examples 5 and 6 exhibit higher luminance at the same voltage as compared with Comparative Example 2 having no metal electron injection layer. In addition, as can be seen from FIG. 18, the life characteristics are also better than those of the comparative example. From these results, the effect of the present invention is clear even when a hexahydropyrimidopyrimidine compound such as the compound of the above formula (7-2) is used for the organic electron injection layer. It was shown that the metal electron injection layer 5 is effective both on the ITO of the cathode as in Examples 5 and 6 and on the metal oxide layer such as zinc oxide.

(Example 7)
Except for [Step 2] of Example 5, the metal oxide layer 4 was not formed, and the compound of formula (7-2) was not used in [Step 4] of Example 5, and the above formula (9) was used. The organic electroluminescent device of Example 7 was obtained in the same manner as in Example 5 except that the organic electron injection layer 5 was formed using the material. As [Step 7], FIG. 19 shows the results of evaluating the voltage-luminance characteristics of the organic electroluminescent device by the same method as in Example 5.

(Example 8)
Except for [Step 2] of Example 5, the metal oxide layer 4 was not formed, and in [Step 3] of Example 5, the metal electron injection layer 5 was formed using silver instead of aluminum. Further, the same as in Example 5 except that the compound of the formula (7-2) was not used in [Step 4] of Example 5 and the organic electron injection layer 6 was formed by using the material of the above formula (9). The organic electroluminescent element of Example 8 was obtained. As [Step 7], FIG. 19 shows the results of evaluating the voltage-luminance characteristics of the organic electroluminescent device by the same method as in Example 5.

(Comparative Example 3)
The metal electron injection layer 5 was not formed except in [Step 3] of Example 5, and the compound of formula (7-2) was not used in [Step 4] of Example 5, and the material of the above formula (9) was not used. The organic electroluminescent device of Comparative Example 3 was obtained in the same manner as in Example 5 except that the organic electron injection layer 6 was formed. As [Step 7], FIG. 19 shows the results of evaluating the voltage-luminance characteristics of the organic electroluminescent device by the same method as in Example 5.

Examples 7 and 8 show higher luminance at the same voltage as compared with Comparative Example 3 having only ITO as a cathode, indicating that the metal electron injection layer 5 is also effective on ITO.

(Example 9)
[Step 1] A substrate 2 (thickness 0.7 mm) with an ITO electrode layer (anode 11) was prepared. This substrate was washed with UV ozone for 20 minutes.
[Step 2] The substrate subjected to the treatment of [Step 1] was introduced into a vacuum apparatus, and the pressure was reduced to 5 × 10 ^-5 Pa or less.
[Step 3] Next, the hole injection layer 10 was formed. Here, molybdenum oxide was formed by a vacuum vapor deposition method, which is a vapor deposition method, so as to have a film thickness of 10 nm.
[Step 4] Next, as the hole transport layer 9, KHLHS-03 manufactured by Chemipro Kasei was 25 nm, and as the light emitting layer 8, KHLHS-03, KHLHS-04 and KHLDG-01 manufactured by Chemipro Kasei were co-deposited at 35 nm, and the hole blocking layer 12 was used. KHLHS-04 manufactured by Chemipro Kasei was laminated with a film thickness of 15 nm, and KHLHEI-02 manufactured by Chemipro Kasei as an electron transport layer 7 was laminated by a vacuum vapor deposition method so as to have a film thickness of 15 nm.
[Step 5] Next, the material of the above formula (9) was formed into a film as the organic electron injection layer 6 by a 1.5 nm vacuum vapor deposition method. The cathode 3 was formed as the final step. Here, aluminum was formed by a vacuum vapor deposition method so as to have a film thickness of 100 nm.
By the above steps [step 1] to [step 5], an organic electroluminescent device having the configuration shown in FIG. 4 was manufactured.
[Step 6] The characteristics (voltage-luminance characteristic, current density-efficiency characteristic and life characteristic) of the organic electroluminescent element were evaluated by the following measurement of the emission characteristics of the organic electroluminescent element and the device life measurement of the organic electroluminescent element. The results are shown in FIGS. 20 to 22, respectively. Further, in order to investigate the atmospheric stability, the cells were left in the atmosphere without being sealed, and the state of luminescence was observed at the initial stage, after 22 hours, and after 90 hours. The observation results are shown in FIG. The numerical values described in the observation results after 90 hours in FIG. 23 indicate the distance at which erosion from the end is confirmed after 90 hours with respect to the end of the light emitting surface at 0 hour.

<Measurement of light emission characteristics of organic electroluminescent device>
A voltage was applied to the element and a current was measured by a "2400 type source meter" manufactured by Keithley. The emission brightness was measured by "BM-7" manufactured by Topcon. The measurement was performed under nitrogen.

<Measurement of device life of organic electroluminescent device>
Luminance deterioration was measured under a constant current in a nitrogen atmosphere.

(Example 10)
An organic electroluminescent device was produced in the same manner as in Example 9 except that [Step 5] of Example 9 was replaced with the following [Step 5-A2]. As [Step 6], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 9 are shown in FIGS. 24 to 26, respectively. Further, in order to investigate the atmospheric stability, the cells were left in the atmosphere without being sealed, and the state of luminescence was observed at the initial stage, after 22 hours, and after 90 hours. The observation results are shown in FIG. 27. The numerical values described in the observation results after 90 hours in FIG. 27 indicate the distance at which erosion from the end is confirmed after 90 hours with respect to the end of the light emitting surface at 0 hour.
[Step 5-A2] Next, the material of the above formula (9) was formed into a film thickness of 1.5 nm as the organic electron injection layer 6 and zinc of 1 nm as the metal electron injection layer 5 by a vacuum vapor deposition method. The cathode 3 was formed as the final step. Here, aluminum was formed by a vacuum vapor deposition method so as to have a film thickness of 100 nm.

(Comparative Example 4)
An organic electroluminescent device was produced in the same manner as in Example 9 except that [Step 5] of Example 9 was replaced with the following [Step 5-A3]. As [Step 6], the results of evaluating the characteristics of the organic electroluminescent device by the same method as in Example 9 are shown in FIGS. 28 to 30, respectively. Further, in order to investigate the atmospheric stability, the cells were left in the atmosphere without being sealed, and the state of luminescence was observed at the initial stage, after 22 hours, and after 90 hours. The observation results are shown in FIG. The numerical values shown in the observation results after 90 hours in FIG. 31 indicate the distance at which erosion from the end is confirmed after 90 hours with respect to the end of the light emitting surface at 0 hour.
[Step 5-A3] Next, instead of the organic electron injection layer 6, LiF was formed by a vacuum vapor deposition method so as to have a film thickness of 1 nm. The cathode 3 was formed as the final step. Here, aluminum was formed by a vacuum vapor deposition method so as to have a film thickness of 100 nm.

(Example 11)
[Step 1] A substrate 2 (thickness 0.7 mm) with an ITO electrode layer (cathode 3) was prepared. This substrate was washed with UV ozone for 20 minutes.
[Step 2] Next, in order to form a layer having a total film thickness of 14.85 nm containing silver and zinc in a volume ratio of 10: 1 as the second cathode 3 and metal electron injection layer 5, the process of [Step 1] is performed. The substrate was introduced into a vacuum apparatus, the pressure was reduced to 5 × 10 ^-5 Pa or less, and a film was formed by a vacuum vapor deposition method.
[Step 3] Next, as the organic electron injection layer 6, the material of the above formula (9), which is a material for an organic electron injection layer, is 3 nm, and as the electron transport layer 7, Chemipro Kasei KHLHEI-02, which is an electron transport material, is 15 nm. KHLHS-04 manufactured by Chemipro Chemical Co., Ltd. was used as the hole blocking layer 12 at 15 nm, KHLHS-03, KHLHS-04 and KHLDG-01 manufactured by Chemipro Chemical Co., Ltd. were co-deposited as the light emitting layer 8 at 35 nm, and KHLHS- was used as the hole transport layer 9. 03 was laminated by a vacuum vapor deposition method so as to have a film thickness of 25 nm.
[Step 4] Next, the hole injection layer 10 was formed on the hole transport layer 9. Here, molybdenum oxide was formed by a vacuum vapor deposition method, which is a vapor deposition method, so as to have a film thickness of 10 nm.
[Step 5] Next, as a final step, the anode 11 was formed on the hole injection layer 10. Here, aluminum was formed by a vacuum vapor deposition method so as to have a film thickness of 100 nm.
By the above steps [step 1] to [step 5], an organic electroluminescent device having the configuration shown in FIG. 5 was produced.
[Step 6] The characteristics (voltage-luminance characteristic, current density-efficiency characteristic and life characteristic) of the organic electroluminescent device were evaluated by the same method as in Example 9. The results are shown in FIGS. 32 to 34, respectively. Further, in order to investigate the atmospheric stability, the cells were left in the atmosphere without being sealed, and the state of luminescence was observed at the initial stage, after 22 hours, and after 90 hours. The observation results are shown in FIG. The numerical values described in the observation results after 90 hours in FIG. 35 indicate the distance at which erosion from the end is confirmed after 90 hours with respect to the end of the light emitting surface at 0 hour.

From the results of Examples 9 to 11 and Comparative Example 4, the following can be seen.
Comparative Example 4 is a forward structure element having a normal structure using the same light emitting material or the like. On the other hand, in Examples 9 and 10, the electron injection layer having a forward structure is changed to the present material, and the metal electron injection layer is made of Al and Zn. Further, Example 11 is a case where Ag and Zn are used for the cathode and metal electron injection layer in the reverse structure. The efficiency is not significantly different although the reverse structure of Example 11 is slightly higher, but the time for which the brightness is reduced by, for example, 10% in the drive life is longer than that of Comparative Example 4 <Example 10 <Example. 9 <The order is longer in the order of Example 11, and in particular, in Example 11, it is 3 to 4 times longer than that of the comparative example. Further, also in terms of atmospheric stability, it can be seen that the area where the non-light emitting portion is generated (eroded portion) is smaller in the order of Comparative Example 4 <Example 10 <Example 9 <Example 11 and is stable in the atmosphere.

(Example 12)
[Step 1] A resist material is applied on a barrier film manufactured by Oike Kogyo (PT7 / 25GT3: thickness 25 μm, WVTR: 4 × 10 ^-3 g / m ² / day) to form a film, and zinc oxide is coated at 24 nm using a sputtering device. A film was formed to form the metal oxide layer 4.
[Step 2] Next, in order to form a layer having a total thickness of 14.85 nm containing silver and zinc in a volume ratio of 10: 1 as the cathode 3 and the metal electron injection layer 5, the treatment of [Step 1] was performed. The substrate was introduced into a vacuum apparatus, the pressure was reduced to 5 × 10 ^-5 Pa or less, and a film was formed by a vacuum vapor deposition method.
[Step 3] Next, as the organic electron injection layer 6, the material of the above formula (9), which is a material for an organic electron injection layer, is 3 nm, and as the electron transport layer 7, Chemipro Kasei KHLHEI-02, which is an electron transport material, is 15 nm. KHLHS-04 manufactured by Chemipro Chemical Co., Ltd. was used as the hole blocking layer 12 at 15 nm, KHLHS-03, KHLHS-04 and KHLDG-01 manufactured by Chemipro Chemical Co., Ltd. were co-deposited as the light emitting layer 8 at 35 nm, and KHLHS- was used as the hole transport layer 9. 03 was laminated by a vacuum vapor deposition method so as to have a film thickness of 25 nm.
[Step 4] Next, the hole injection layer 10 was formed on the hole transport layer 9. Here, molybdenum oxide was formed by a vacuum vapor deposition method, which is a vapor deposition method, so as to have a film thickness of 10 nm.
[Step 5] Next, as a final step, the anode 11 was formed on the hole injection layer 10. Here, aluminum was formed by a vacuum vapor deposition method so as to have a film thickness of 200 nm. Further, a barrier film manufactured by Oike Kogyo (thickness 25 μm, WVTR: 4X10 ^-3 g / m ² / day) was used to seal the film.
By the above steps [step 1] to [step 5], a film organic electroluminescent device having the configuration shown in FIG. 6 was produced. The thickness was about 98 μm.
[Step 6] The atmospheric stability of the produced organic electroluminescent device was evaluated by storing it in an environment of 85 ° C. and 85% humidity. The results are shown in FIG. No dark spots were observed even after 100 days of storage, and there was no erosion of the non-light emitting part from the edge of the light emitting surface.

(Comparative Example 5)
The same as in Example 12 except that [Step 2] of Example 12 is replaced with the following [Step 2-C2] and [Step 3] is replaced with the following [Step 3-C2] is performed in the same manner as in Example 12, and an organic electric field having the same element thickness is used. A light emitting device was manufactured. As [Step 6], the atmospheric stability of the produced organic electroluminescent device was evaluated by storing it in an environment of 85 ° C. and 85% humidity. The results are shown in FIG. 37. Dark spots were observed 100 days after storage, and erosion of the non-light emitting part from the edge of the light emitting surface was also observed.
[Step 2-C2] Next, in order to form a silver layer having a film thickness of 10 nm as a cathode, the substrate treated with [Step 1] is introduced into a vacuum apparatus, and the pressure is reduced to 5 × ^10-5 Pa or less to create a vacuum. A film was formed by a vapor deposition method. Further, sputtering was performed with argon and oxygen introduced to prepare a zinc oxide layer having a film thickness of about 2 nm, which is a metal oxide.
[Step 3-C2] Next, as the organic buffer layer 13, polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., Epomin P1000, molecular weight 70000) diluted to 0.05% by weight with ethanol was used, and spin-coated to 1 to 2 nm. The film was formed to a film thickness. After that, it was introduced into the vacuum device again, and the pressure was reduced to 5 × 10 ^-5 Pa or less. 04 was formed by laminating KHLHS-03, KHLHS-04 and KHLDG-01 as a light emitting layer 8 at 35 nm, and KHLHS-03 manufactured by Chemipro Kasei as a hole transport layer 9 by co-evaporation.

From Example 12, it was clarified that the atmospheric stability proved by glass also holds for the film device. In addition, comparison with Comparative Example 5 showed that there was almost no growth of dark spots in Example 12, which also proved to be highly resistant to the atmosphere.

1: Organic EL element, 2: Substrate, 3: Cathode, 4: Metal oxide layer, 5: Metal electron injection layer, 6: Organic electron injection layer, 7: Electron transport layer, 8: Light emitting layer, 9: Hole Transport layer, 10: hole injection layer, 11: anode, 12: hole blocking layer, 13: organic buffer layer

Claims (10)

An organic electric field light emitting element having at least a pair of electrodes and an organic layer between them, and a metal element and an organic material that can be coordinated and bonded adjacent to the cathode are contained in the metal electron injection layer and the organic electron injection layer, respectively. , A metal electron injection layer, and an organic electron injection layer in this order. The organic electroluminescent device according to claim 1, wherein the work function of all the metal species contained in the metal electron injection layer is 4.0 eV or more. The organic electroluminescent device according to claim 1 and 2, wherein the metal electron injection layer contains at least one selected from the group consisting of zinc, copper, and aluminum. The organic electroluminescent device according to claim 1 to 3, wherein the metal electron injection layer has a film thickness of 5 nm or less. The organic electroluminescent device according to any one of claims 1 to 4, wherein the work function of the cathode is 4.0 eV or more. The organic electroluminescent device according to claim 1 to 5, wherein the cathode is on a substrate. The organic electroluminescent device according to any one of claims 1 to 3, 5 and 6, wherein the metal electron injection layer is made by mixing with a cathode constituent material. A display device comprising the organic electroluminescent device according to any one of claims 1 to 7. A lighting device comprising the organic electroluminescent element according to any one of claims 1 to 7. An organic electric field light emitting element having at least a pair of electrodes and an organic layer between them, and a metal element and an organic material that can be coordinated and bonded adjacent to the cathode are contained in the metal electron injection layer and the organic electron injection layer, respectively. , A method for manufacturing an organic electric field light emitting element, characterized in that it is configured in the order of a metal electron injection layer and an organic electron injection layer.

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