JP7197337B2 - organic electroluminescent device - Google Patents

Description

The present invention relates to organic electroluminescent devices. More specifically, the present invention relates to an organic electroluminescence device that can be used as a display device such as a display unit of electronic equipment, a lighting device, or the like.

Organic electroluminescence elements (organic EL elements) are expected as new light-emitting elements that can be applied to thin, flexible display devices and lighting.
An organic electroluminescent device has a structure in which one or more layers including a light-emitting layer containing a light-emitting organic compound are sandwiched between an anode and a cathode, and holes injected from the anode and emitted from the cathode The energy generated when the injected electrons recombine is used to excite a light-emitting organic compound to obtain light emission. An organic electroluminescence device is a current-driven device, and in order to make more efficient use of the flowing current, various studies have been made on the device structure and the materials of the layers that constitute the device (for example, Patent Documents 1 to 3, See Non-Patent Document 1).

JP 2013-239691 A WO2014/133141 JP 2015-65225 A

A. Endo et al. , Appl. Phys. Lett. , 98, 083302 (2011)

Organic electroluminescence elements are said to be suitable for flexible display devices and lighting, but there is a problem that moisture penetrates into the device in general flexible substrates, resulting in rapid attenuation of brightness. On the other hand, strict sealing to prevent moisture intrusion sacrifices flexibility, so there is a demand for an element that suppresses early attenuation of luminance while maintaining flexibility.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic electroluminescence device that is excellent in flexibility and effectively suppresses early decay of device luminance.

In order to solve the above problems, the present inventors have made various studies on the structure and materials of the organic electroluminescent device, and found that a plurality of layers including a light-emitting layer are laminated between the anode and the cathode formed on the substrate. In addition to adopting a so-called reverse structure, when the light-emitting layer is formed of a material that contains a host material and a light-emitting material and the triplet excited state of the host material generated by recombination of charges can transfer energy to the light-emitting material, the light-emitting layer is formed by moisture. It was found that an element having excellent resistance to deterioration can be obtained. This allows for simple or no encapsulation of the device, effectively premature decay of the brightness of the device without sacrificing flexibility. The present inventors have arrived at the present invention by finding that an organic electroluminescence device with a suppressed effect can be obtained.

That is, the present invention provides an organic electroluminescence device having a structure in which a plurality of layers including a light-emitting layer are laminated between an anode and a cathode formed on a substrate, wherein the organic electroluminescence device comprises a light-emitting layer contains a host material and a light-emitting material, the triplet excited state of the host material generated by charge recombination can transfer energy to the light-emitting material, and the water vapor transmission rate is 10 ⁻⁴ g/m ² ·day or more An organic electroluminescence device characterized by being sealed or having no sealing structure.

Preferably, the host material in the light-emitting layer is a thermally activated delayed fluorescent material, and the light-emitting material is a phosphorescent material.

It is preferable that the host material in the light-emitting layer is an exciplex consisting of two kinds of materials, a donor material and an acceptor material, and the light-emitting material is a phosphorescent material.

Preferably, the host material in the light-emitting layer is a fluorescent host capable of triplet-triplet annealing, and the light-emitting material is a fluorescent material.

The host material in the light emitting layer is a combination of a thermally activated delayed fluorescent material and a host material having a higher excited state energy level than the triplet excited state energy level of the thermally activated delayed fluorescent material, and emits light. Preferably, the material is a fluorescent material.

The present invention is also a display device comprising the organic electroluminescence device of the present invention.

The present invention also provides a lighting device comprising the organic electroluminescence device of the present invention.

INDUSTRIAL APPLICABILITY The organic electroluminescence device of the present invention can be suitably used as a material for display devices and lighting devices because it is a device in which early attenuation of device luminance is suppressed while having excellent flexibility.

1 is a diagram showing the structure of an organic electroluminescence device produced in Example 1. FIG. 2 is a graph showing the relationship between the elapsed time from the start of driving at a constant current and the relative luminance using an organic EL lifetime measuring device for the organic electroluminescence devices of Example 1 and Reference Example 1. FIG. . 2 is a graph showing the relationship between the elapsed time from the start of driving at a constant current and the relative luminance using an organic EL lifetime measuring device for the organic electroluminescence devices of Example 2 and Reference Example 2. FIG. . A graph showing the relationship between the elapsed time from the start of driving at a constant current and the relative luminance using an organic EL lifetime measuring device for the organic electroluminescent devices of Comparative Example 1 and Comparative Reference Example 1. be. 10 is a graph showing the relationship between the elapsed time from the start of driving with a constant current and the relative luminance using an organic EL lifetime measuring device for the organic electroluminescence devices of Example 3 and Reference Example 3. FIG. . A graph showing the relationship between the elapsed time from the start of driving at a constant current and the relative luminance using an organic EL lifetime measuring device for the organic electroluminescent devices of Comparative Example 2 and Comparative Reference Example 2. be. 10 is a graph showing the relationship between the elapsed time from the start of driving at a constant current and the relative luminance using an organic EL lifetime measuring device for the organic electroluminescence devices of Example 4 and Reference Example 4. FIG. .

The present invention will be described in detail below.
A combination of two or more of the individual preferred embodiments of the invention described below is also a preferred embodiment of the invention.

The organic electroluminescent device of the present invention has a structure in which a plurality of layers including a light-emitting layer are laminated between an anode and a cathode formed on a substrate, and the light-emitting layer includes a host material and a light-emitting material. , the light-emitting layer is formed of a material in which the triplet excited state of the host material generated by charge recombination can transfer energy to the light-emitting material, and the light-emitting layer is simply sealed or has a sealing structure. It is characterized by three things:
Moisture causes deterioration of the electrodes of the organic electroluminescence element, and the deterioration of the electrodes causes deterioration of the characteristics of the element. In particular, the use of an unstable material such as an alkali metal as an electron injection layer at the cathode interface causes deterioration of the cathode interface. On the other hand, by changing the structure of the device to a so-called reverse structure in which a plurality of layers including a light-emitting layer are laminated between the anode and the cathode formed on the substrate, alkali It becomes possible to use a metal oxide or the like that has a low work function and is stable in the air instead of an unstable material such as a metal, and it is possible to suppress deterioration of the electrode. Adopting such a reverse structure, a host material capable of transferring energy from the triplet excited state of the host material to the singlet excited state to the light emitting material and the light emitting material are used as materials for the light emitting layer, which will be described later. The organic electroluminescence element of the present invention used is an element in which the luminance attenuation of the light-emitting layer is effectively suppressed. Furthermore, the effect of suppressing the reduction of the light emitting area can also be obtained. By configuring these elements, the elements can be driven satisfactorily without strict encapsulation. Therefore, it is possible to create an element that is easy to enclose or does not have an encapsulation structure, and has excellent flexibility. element.

The organic electroluminescence device of the present invention has one or more organic compound layers between an anode and a cathode formed on a substrate. Here, the organic compound layer is a layer including a light-emitting layer and, if necessary, an electron-transporting layer, a hole-transporting layer, and the like.
As long as the organic electroluminescent device of the present invention has a structure in which a plurality of layers including a light-emitting layer are laminated between an anode and a cathode formed on a substrate, the structure of the laminated layers is particularly Although not limited, it is preferable to be an element in which each layer of a cathode, an electron injection layer and/or an electron transport layer, a light emitting layer, a hole transport layer and/or a hole injection layer, and an anode are laminated adjacent to each other in this order. In addition, each of these layers may consist of one layer, and may consist of two or more layers.
In the organic electric field element having the above structure, when the element has only one of the electron transport layer and the electron injection layer, the one layer is laminated adjacent to the cathode and the light emitting layer, and the element has both a hole-transporting layer and a hole-injecting layer, these layers are stacked adjacently in the order cathode, electron-injecting layer, electron-transporting layer, and light-emitting layer. In addition, when the device has only one of the hole transport layer and the hole injection layer, the one layer is laminated adjacent to the light emitting layer and the anode, so that the device has a hole transport layer. In the case of having both a layer and a hole injection layer, these layers are laminated adjacent to each other in the order of light emitting layer, hole transport layer, hole injection layer and anode.

The organic electroluminescent device of the present invention is preferably an organic-inorganic hybrid type organic electroluminescent device further having a metal oxide layer between the cathode and the anode. By using a metal oxide as the element material, an organic electroluminescence element having higher resistance to oxygen and water can be obtained.
The organic electroluminescent device of the present invention is an organic-inorganic hybrid type organic electroluminescent device having a cathode formed adjacent to a substrate and a metal oxide layer between the anode and the cathode, wherein the cathode and the light-emitting layer It is preferable that the device has an electron injection layer and, if necessary, an electron transport layer between and a hole transport layer and/or a hole injection layer between the anode and the light emitting layer. . Although the organic electroluminescence device in the present invention may have other layers between these layers, it is preferably a device composed only of these layers. That is, it is preferable that the device is a device in which each layer of a cathode, an electron injection layer, optionally an electron transport layer, a light-emitting layer, a hole transport layer and/or a hole injection layer, and an anode are laminated adjacently in this order. In addition, each of these layers may consist of one layer, and may consist of two or more layers.

In the organic electroluminescent device of the present invention, the light-emitting layer includes a host material capable of transferring energy from the triplet excited state of the host material to the light-emitting material and a light-emitting material.
There are two types of energy transfer from the excited state of the host material to the excited state of the light-emitting material (guest material): the Forster mechanism and the Dexter mechanism. Transfer from singlet excited state (S1) of material to singlet excited state (S1) of guest material, (b) transfer from T1 of host material to T1 of guest material, (c) transfer from S1 of host material to guest material (d) migration of the host material from T1 to S1 of the guest material. Of these, (a), (c), and (d) are movements by the Forster mechanism, and (b) is movement by the Dexter mechanism.
Of these, the movement of the host material from T1 to T1 of the guest material by the Dexter mechanism is slow, so the time in which the host material is in an excited state that is unstable and easily interacts with moisture is long, and the light-emitting layer lead to deterioration of On the other hand, the lifetime of the excited state of the host material is generally about 1,000,000 times shorter than that of T1. Deterioration can be effectively suppressed. Furthermore, since the rate of energy transfer by the Forster mechanism is inversely proportional to the lifetime of the host material in the excited state, when the host material is in the singlet excited state (S1), it is The rate of energy transfer to the light-emitting material is very high and the energy transfer occurs very efficiently.
In the organic electroluminescent device of the present invention, electrons are transitioned from the triplet excited state of the host material to the singlet excited state, and the energy transfer from the singlet excited state of the host material to the light-emitting material is performed by the Forster mechanism. A host material capable of transferring energy and a light-emitting material are used as materials for the light-emitting layer. It suppresses deterioration due to action, and suppresses attenuation of the luminance of the organic electroluminescence device even in the presence of moisture.

A host material capable of causing electrons to transition from the triplet excited state of the host material to a singlet excited state and transferring energy from the singlet excited state of the host material to the light-emitting material by the Forster mechanism, and light emission Combinations with materials include the following, all of which are preferred embodiments of the present invention.
(I) The host material in the light-emitting layer is a thermally activated delayed fluorescence (TADF) material, and the light-emitting material is a phosphorescent material. (II) The host material in the light-emitting layer is a donor material and an acceptor material. wherein the light-emitting material is a phosphorescent material, (III) the host material in the light-emitting layer is a fluorescent host capable of triplet triplet annealing, and the light-emitting material is a fluorescent material, (IV) The host material in the light emitting layer is a combination of a thermally activated delayed fluorescent material and a host material having a higher excited state energy level than the triplet excited state energy level of the thermally activated delayed fluorescent material, and a light emitting material is a fluorescent material.
These four forms will be described in order below.

Since the thermally activated delayed fluorescent material used in the above form (I) has a small energy level difference between the triplet excited state and the singlet excited state, the triplet excited state can be easily changed to the singlet excited state by thermal energy. , and by observing the time-resolved luminescence phenomenon, delayed fluorescence caused by thermal transition from the triplet excited state to the singlet excited state can be observed. By using a thermally activated delayed fluorescence material as the host material, fast energy transfer from the triplet excited state to the luminescent material via the singlet excited state becomes possible.
Furthermore, by using a phosphorescent material with high internal quantum efficiency as a light-emitting material, an element with high light-emitting efficiency can be obtained.

Examples of the thermally activated delayed fluorescence material include those containing a donor-type substituent and an acceptor-type substituent in a single molecule.
Acceptor-type substituents include pyridine derivatives, quinoline derivatives, pyrimidine derivatives, pyrazine derivatives, phenanthroline derivatives, triazine derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, naphthalene, aromatic ring tetracarboxylic acid anhydrides, siloles. derivatives.
Donor-type substituents include arylcycloalkane-based compounds, arylamine-based compounds, phenylenediamine-based compounds, carbazole-based compounds, stilbene-based compounds, oxazole-based compounds, triphenylmethane, triphenylmethane-based compounds, pyrazoline-based compounds, and benzine. (cyclohexadiene)-based compounds, anthracene-based compounds, fluorenone-based compounds, aniline-based compounds, silane-based compounds, pibenzidine-based compounds, and the like.

Specific examples of the luminescent compound containing a donor-type substituent and an acceptor-type substituent in a single molecule include compounds described in Non-Patent Document 1 and 12,12′-(6-phenyl-1,3 ,5-triazine-2,4-diyl)bis(11-phenyl-11,12-dihydroindolo[2,3-a]carbazole) (BPICbPTRZ), 2-biphenyl-4,6-bis(12-phenylindolo[2 ,3-a]carbazole-11-yl)-1,3,5-triazine (PIC-TRZ) and the like are preferably used.
The difference between the energy of S1 and the energy of T1 is 0.14 eV for BPICbPTRZ and 0.11 eV for PIC-TRZ.

In the above form (II), an exciplex in which these excited states are hybridized by charge transfer from the donor material to the acceptor material is utilized. When a triplet excited state and a singlet excited state with a small energy level difference are formed in the exciplex, the triplet excited state passes through the singlet excited state to the light-emitting material, as in the above form (I). fast energy transfer is possible.
Furthermore, by using a phosphorescent material as a light-emitting material, an element with high light-emitting efficiency can be obtained.

As the donor material, N4,N4'-bis(dibenzo[b,d]thiophen-4-yl)-N4,N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), 1,1-bis Arylcycloalkane compounds such as (4-di-para-triaminophenyl)cyclohexane, 1,1′-bis(4-di-para-tolylaminophenyl)-4-phenyl-cyclohexane, 4,4 ',4''-trimethyltriphenylamine, N,N,N',N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'- Bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1), N,N'-diphenyl-N,N'-bis(4-methoxyphenyl)-1,1'- Biphenyl-4,4'-diamine (TPD2), N,N,N',N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD3), N,N '-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), arylamine compounds such as TPTE, N,N,N' ,N'-tetraphenyl-para-phenylenediamine, N,N,N',N'-tetra(para-tolyl)-para-phenylenediamine, N,N,N',N'-tetra(meth-tolyl) - phenylenediamine compounds such as meta-phenylenediamine (PDA), carbazole compounds such as carbazole, N-isopropylcarbazole and N-phenylcarbazole, stilbene compounds such as stilbene and 4-di-para-tolylaminostilbene compounds, oxazole compounds such as OxZ, triphenylmethane, triphenylmethane compounds such as m-MTDATA, pyrazoline compounds such as 1-phenyl-3-(para-dimethylaminophenyl)pyrazoline, benzine (cyclo hexadiene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, 1,3,4-oxadiazole, 2,5-di(4-dimethylaminophenyl)-1,3,4, -oxadiazole compounds such as oxadiazole, anthracene, anthracene compounds such as 9-(4-diethylaminostyryl)anthracene, fluorenone, 2,4,7,-trinitro-9-fluorenone, 2,7- screw (2- Fluorenone compounds such as hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone, aniline compounds such as polyaniline, silane compounds, 1,4-dithioketo-3,6-diphenyl-pyrrolo-( 3,4-c) Pyrrole compounds such as pyrrolopyrrole, fluorene compounds such as fluorene, porphyrins, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, phthalocyanine, copper phthalocyanine, tetra (t-butyl) copper phthalocyanine, metal or metal-free phthalocyanine compounds such as iron phthalocyanine, metal or metal-free naphthalocyanine compounds such as copper naphthalocyanine, vanadyl naphthalocyanine, monochlorogallium naphthalocyanine, N, N Benzidine compounds such as '-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine and N,N,N',N'-tetraphenylbenzidine can be used.

Examples of the acceptor material include bis[2-(o-hydroxyphenylbenzothiazole]zinc(II) (ZnBTZ2), boron-containing compounds, tris-1,3,5-(3′-(pyridine-3″- pyridine derivatives such as yl)phenyl)benzene (TmPyPhB), quinoline derivatives such as (2-(3-(9-carbazolyl)phenyl)quinoline (mCQ)), 2-phenyl-4,6-bis(3, pyrimidine derivatives such as 5-dipyridylphenyl)pyrimidine (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), 2,4-bis(4-biphenyl)-6-(4′-(2-pyridinyl) )-4-biphenyl)-[1,3,5]triazine (MPT), 3-phenyl-4-(1′-naphthyl)-5-phenyl-1,2,4-triazole (TAZ ), oxazole derivatives, oxadiazole derivatives such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), 2 ,2′,2″-(1,3,5-Bentriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic ring tetracarboxylic acids such as naphthalene and perylene various metal complexes represented by anhydrides, bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ)2), tris(8-hydroxyquinolinato)aluminum (Alq3), 2,5-bis (6′-(2′,2″-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) and other organosilane derivatives, such as silole derivatives, The boron-containing compounds described in 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 can be used.

In the above form (III), a material capable of triplet-triplet annealing (TTA) is used as the host material. In a material capable of TTA, collision between material molecules in a triplet excited state causes TTA, resulting in a high-energy singlet excited state. When the singlet excited state is formed, fast energy transfer from the triplet excited state to the singlet excited state to the light-emitting material becomes possible, as in the case of the above form (I).
By using a combination of such a host material and a fluorescent material as a light-emitting material, an element with high light-emitting efficiency can be obtained.

Materials capable of the above TTA include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)- Phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10- Phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1 ,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene (abbreviation: FLPPA), 9- [4-(7-benzo[a]anthracene)phenyl]-9H-carbazole (abbreviation: 7CzPaBA) and the like. Alternatively, 5,12-diphenyltetracene, 5,12-bis(biphenyl-2-yl)tetracene and the like can be used.

In the above form (IV), a thermally activated delayed fluorescent material and a host material whose excited state energy level is higher than the triplet excited state energy level of the thermally activated delayed fluorescent material are used in combination.
In this form, by using the thermally activated delayed fluorescence material, as in the form (I), fast energy transfer from the triplet excited state to the singlet excited state to the light-emitting material becomes possible. Furthermore, by combining a host material whose excited state energy level is higher than the energy level of the triplet excited state of the thermally activated delayed fluorescent material, the triplet excited state of the host material is converted into the thermally activated delayed fluorescent material. Since energy transfer to the triplet excited state occurs, more energy can be transferred from the host material to the light-emitting material.
By using a combination of such a host material and a fluorescent material as a light-emitting material, an element with high light-emitting efficiency can be obtained.

As the host material whose excited state energy level is higher than that of the triplet excited state of the thermally activated delayed fluorescence material, 8-hydroxyquinoline aluminum (Alq3), tris[1-phenylisoquinoline-C2,N ] iridium (III) (Ir(piq)3), bis[2-(o-hydroxyphenylbenzothiazole]zinc(II) (ZnBTZ2) tris(4-methyl-8quinolinoleate) aluminum (III) (Almq3), 8 - hydroxyquinoline zinc (Znq2), (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-porphineplatinum(II); distyrylbenzene (DSB), Benzene compounds such as diaminodistyrylbenzene (DADSB), naphthalene, naphthalene compounds such as Nile Red, phenanthrene compounds such as phenanthrene, chrysene compounds such as chrysene and 6-nitrochrysene, perylene, N, Perylene compounds such as N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-di-carboximide (BPPC), coronene compounds such as coronene, anthracene , anthracene compounds such as bisstyryl anthracene, pyrene compounds such as pyrene, 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM) pyran-based compounds, acridine-based compounds such as acridine, stilbene-based compounds such as stilbene, 4,4'-bis[9-dicarbazolyl]-2,2'-biphenyl (CBP), 4,4'-bis ( Carbazole compounds such as 9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi), thiophene compounds such as 2,5-dibenzoxazolethiophene, benzoxazole compounds such as benzoxazole, benzimidazole Benzimidazole compounds such as, benzothiazole compounds such as 2,2'-(para-phenylenedivinylene)-bisbenzothiazole, bistyryl (1,4-diphenyl-1,3-butadiene), tetraphenylbutadiene of butadiene compounds such as naphthalimide, coumarin compounds such as coumarin, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, 1, cyclopentadiene compounds such as 2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP), quinacridone compounds such as quinacridone and quinacridone red, pyridines such as pyrrolopyridine and thiadiazolopyridine -based compounds, spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene, phthalocyanine (H2Pc), metal or metal-free phthalocyanine compounds such as copper phthalocyanine, etc. can be used.

As the phosphorescent material used as the light-emitting material in the above forms (I) and (II), a compound represented by the following formula (1) or a compound represented by the following formula (2) is preferable.

In formula (1), the dotted arc represents that a ring structure is formed together with a part of the skeleton portion composed of an oxygen atom and three carbon atoms, and a ring structure formed containing a nitrogen atom is a heterocyclic ring structure.
X ^' and X ^'' each represent a hydrogen atom or a monovalent substituent that serves as a substituent of the ring structure, and may be bonded to the ring structure forming the dotted circular arc portion. X ^' , X ^'' may combine to form a new ring structure together with a portion of the two ring structures represented by the dotted arcs. X ^' and X ^'' may be the same or different.
In formula (1), a dotted line in a skeleton portion composed of a nitrogen atom and three carbon atoms indicates that two atoms connected by the dotted line are bonded with a single bond or a double bond.
In Formula (1), M' represents a metal atom. An arrow from a nitrogen atom to M' indicates that the nitrogen atom is coordinated to the M' atom. n represents the valence of the metal atom M'.

In formula (2), the dotted arc represents that a ring structure is formed together with a part of the skeleton portion composed of a nitrogen atom and three carbon atoms, and a ring structure formed containing a nitrogen atom is a heterocyclic ring structure.
X ^' and X ^'' each represent a hydrogen atom or a monovalent substituent that serves as a substituent of the ring structure, and may be bonded to the ring structure forming the dotted circular arc portion. X ^' , X ^'' may combine to form a new ring structure together with a portion of the two ring structures represented by the dotted arcs. X ^' and X ^'' may be the same or different.

In formula (2), a dotted line in a skeleton portion composed of a nitrogen atom and three carbon atoms indicates that two atoms connected by the dotted line are bonded with a single bond or a double bond.
In Formula (2), M' represents a metal atom. An arrow from a nitrogen atom to M' indicates that the nitrogen atom is coordinated to the M' atom. n represents the valence of the metal atom M'.
In formula (2), the solid arc connecting ^Xa and ^Xb represents that ^Xa and ^Xb are bonded via at least one other atom, and together with ^Xa and ^Xb It may form a structure. Xa and ^Xb each represent an oxygen atom, ^a nitrogen atom, or a carbon atom. X ^a and X ^b may be the same or different. An arrow from ^Xb to M' indicates that ^Xb is coordinated to the M' atom. m' is a number from 1 to 3;

Examples of the ring structure represented by the dotted circular arc in the above formulas (1) and (2) include aromatic rings and heterocyclic rings having 2 to 20 carbon atoms. Specifically, aromatic hydrocarbon rings such as benzene ring, naphthalene ring, and anthracene ring; pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, benzothiazole ring, benzothiol ring, benzoxazole ring, benzoxole ring, Heterocyclic rings such as benzimidazole ring, quinoline ring, isoquinoline ring, quinoxaline ring, and phenanthridine ring, thiophene ring, furan ring, benzothiophene ring, and benzofuran ring are included.

In the above formulas (1) and (2), the substituents of the ring structures represented by X ^′ and X ^″ include halogen atoms, alkyl groups having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, aralkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, alkenyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, aryl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms , arylamino group, cyano group, amino group, acyl group, alkoxycarbonyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, carboxyl group, alkoxy having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms an alkylamino group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, a dialkylamino group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, 1 to 20 carbon atoms, preferably 1 to 1 carbon atoms 10 aralkylamino groups, haloalkyl groups having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, hydroxyl groups, aryloxy groups, carbazole groups and the like.

In the above formulas (1) and (2), when X ^′ and X ^″ are combined to form a new ring structure together with part of the two ring structures represented by the dotted arcs, Examples of ring structures obtained by combining two ring structures represented by circular arcs and a new ring structure include structures shown in (3-1) and (3-2) below.

In the compounds represented by formulas (1) and (2) above, metal atoms represented by M' include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold.

The compound represented by the above formula (2) preferably has a structure represented by the following formula (4-1) or (4-2).

In formulas (4-1) and (4-2), R ¹ to R ³ each represent a hydrogen atom or a monovalent substituent. R ¹ to R ³ may be the same or different.
In formula (4-2), when R ¹ to R ³ are monovalent substituents, the ring structure may have a plurality of monovalent substituents.
In formulas (4-1) and (4-2), the arrow from the nitrogen atom to M' indicates that the nitrogen atom is coordinated to the M' atom. In formula (4-1), the arrow from the oxygen atom to M' indicates that the oxygen atom is coordinated to the M' atom.

Specific examples of the compound represented by the above formula (1) or formula (2) include the following formulas (5-1) to (5-13), (6-1) to (6-8), (7- 1) to compounds represented by (7-8).

As the phosphorescent material used as the light-emitting material in the above modes (I) and (II), one or more of the above-mentioned materials can be used. Among these, iridium tris(2-phenylpyridine) (Ir(ppy) ₃ ) represented by the above formula (5-1), iridium tris(1-phenylisoquinoline) represented by the above formula (6-6) (Ir(piq) ₃ ), iridium bis(2-methyldibenzo-[f,h]quinoxaline)(acetylacetonate) represented by the above formula (7-6) (Ir(MDQ) ₂ (acac)), It is preferable to use iridium tris[3-methyl-2-phenylpyridine](Ir(mppy) ₃ ) represented by the above formula (7-7).
As the phosphorescent material used as the light emitting material in this embodiment, TLEC025 represented by the above formula (7-8), which is a Pt complex, may be used.
Further, the phosphorescent material used as the light-emitting material in this embodiment is preferably a material that emits phosphorescence at room temperature.

Fluorescent materials used as light-emitting materials in the above modes (III) and (IV) include 8-hydroxyquinoline aluminum (Alq3) and bis[2-(o-hydroxyphenylbenzothiazole]zinc(II) (ZnBTZ2). Various metal complexes such as tris(4-methyl-8quinolinolate) aluminum (III) (Almq3), 8-hydroxyquinoline zinc (Znq2); benzenes such as distyrylbenzene (DSB), diaminodistyrylbenzene (DADSB) naphthalene, naphthalene compounds such as Nile Red, phenanthrene compounds such as phenanthrene, chrysene, chrysene compounds such as 6-nitrochrysene, perylene, N,N'-bis(2,5-di- perylene compounds such as t-butylphenyl)-3,4,9,10-perylene-di-carboximide (BPPC); coronene compounds such as coronene; anthracene compounds such as anthracene and bisstyrylanthracene; pyrene compounds such as pyrene, pyran compounds such as 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM), acridine compounds such as acridine compounds, stilbene compounds such as stilbene, 4,4'-bis[9-dicarbazolyl]-2,2'-biphenyl (CBP), 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1 carbazole-based compounds such as '-biphenyl (BCzVBi), thiophene-based compounds such as 2,5-dibenzoxazolethiophene, benzoxazole-based compounds such as benzoxazole, benzimidazole-based compounds such as benzimidazole, 2,2 benzothiazole-based compounds such as '-(para-phenylenedivinylene)-bisbenzothiazole, bistyryl (1,4-diphenyl-1,3-butadiene), butadiene-based compounds such as tetraphenylbutadiene, and naphthalimide. naphthalimide compounds, coumarin compounds such as coumarin, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, 1,2,3,4,5-pentaphenyl -cyclopentadiene compounds such as 1,3-cyclopentadiene (PPCP), quinacridone compounds such as quinacridone and quinacridone red, pyrrolopyryl pyridine compounds such as thiadiazolopyridine, spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene, phthalocyanine (H2Pc), such as copper phthalocyanine A metal or metal-free phthalocyanine compound and the like are included.

The luminescent layer preferably contains 1 to 10% by mass of the luminescent material with respect to 100% by mass of the host material. By including such a ratio, it is possible to obtain a device that emits light with high external quantum efficiency while suppressing manufacturing costs. The ratio of the luminescent material to 100% by mass of the host material is more preferably 1 to 8% by mass, and still more preferably 1 to 6% by mass.

The ratio of the donor material and the acceptor material in the form (II) is preferably 10 to 1000% by mass of the acceptor material with respect to 100% by mass of the donor material. By containing the donor material and the acceptor material in such a ratio, an exciplex is efficiently generated, and energy transfer from the host material to the light emitting material is performed more efficiently. More preferably, the acceptor material accounts for 25 to 400% by mass, more preferably 50 to 200% by mass, based on 100% by mass of the donor material.

Although the average thickness of the light-emitting layer is not particularly limited, it is preferably 10 to 150 nm. It is more preferably 20 to 100 nm, still more preferably 40 to 100 nm.
The average thickness of the light-emitting layer can be measured with a crystal oscillator film thickness meter in the case of a low-molecular-weight compound, and with a contact-type profilometer in the case of a high-molecular-weight compound.

When the organic electroluminescence device has an electron transport layer, any compound that can be usually used as a material for the electron transport layer can be used as the material thereof, and a mixture of these can be used.
Examples of compounds that can be used as materials for the electron transport layer include pyridine derivatives such as tris-1,3,5-(3′-(pyridin-3″-yl)phenyl)benzene (TmPyPhB), ( 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), 2,4-bis(4-biphenyl)-6-(4′-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT), triazole derivatives such as 3-phenyl-4-(1′-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), oxazole derivatives, 2-(4- oxadiazole derivatives such as biphenylyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), 2,2′,2″-(1,3,5- imidazole derivatives such as benzoyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic ring tetracarboxylic acid anhydrides such as naphthalene and perylene, bis[2-(2-hydroxyphenyl)benzothiazolato] Various metal complexes represented by zinc (Zn(BTZ) ₂ ), tris(8-hydroxyquinolinato)aluminum (Alq3), 2,5-bis(6′-(2′,2″-bipyridyl)) -1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) and other silole derivatives, and organic silane derivatives and the like, and one or more of these can be used.
Among these, metal complexes such as Alq3 and pyridine derivatives such as _TmPyPhB are preferred.

When the organic electroluminescent device has a hole-transporting layer, the hole-transporting organic material used as the hole-transporting layer includes various p-type polymer materials and various p-type low-molecular-weight materials alone or in combination. can be used
Examples of p-type polymer materials (organic polymers) include polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly(N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, Polyalkylthiophene, polyhexylthiophene, poly(p-phenylene vinylene), polytinylene vinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin or derivatives thereof, and the like.
These compounds can also be used as mixtures with other compounds. As an example, mixtures containing polythiophenes include poly(3,4-ethylenedioxythiophene/styrenesulfonic acid) (PEDOT/PSS) and the like.

Examples of the p-type low molecular weight materials include 1,1-bis(4-di-para-triaminophenyl)cyclohexane, 1,1′-bis(4-di-para-tolylaminophenyl)- Arylcycloalkane compounds such as 4-phenyl-cyclohexane, 4,4′,4″-trimethyltriphenylamine, N,N,N′,N′-tetraphenyl-1,1′-biphenyl-4, 4'-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1), N,N'-diphenyl-N , N′-bis(4-methoxyphenyl)-1,1′-biphenyl-4,4′-diamine (TPD2), N,N,N′,N′-tetrakis(4-methoxyphenyl)-1,1 '-biphenyl-4,4'-diamine (TPD3), N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD ), arylamine compounds such as TPTE, N,N,N',N'-tetraphenyl-para-phenylenediamine, N,N,N',N'-tetra(para-tolyl)-para-phenylenediamine , N,N,N',N'-tetra(meta-tolyl)-meta-phenylenediamine (PDA) and other phenylenediamine compounds, carbazole, N-isopropylcarbazole, N-phenylcarbazole and other carbazole compounds , stilbene, 4-di-para-tolylaminostilbene, stilbene-based compounds, oxazole-based compounds, such as O _x Z, triphenylmethane, triphenylmethane-based compounds, such as m-MTDATA, 1-phenyl-3 -(para-dimethylaminophenyl)pyrazoline, pyrazoline-based compounds, benzine (cyclohexadiene)-based compounds, triazole-based compounds, such as triazole, imidazole-based compounds, such as imidazole, 1,3,4-oxadiazole, Oxadiazole compounds such as 2,5-di(4-dimethylaminophenyl)-1,3,4-oxadiazole, anthracene, anthracene compounds such as 9-(4-diethylaminostyryl)anthracene, fluorenone , 2,4,7-trinitro-9-fluorenone, 2,7-bis(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo) fluorenone, fluorenone compounds such as polyani aniline-based compounds such as phosphorus, silane-based compounds, pyrrole-based compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo-(3,4-c)pyrrolopyrrole, florene-based compounds such as florene, Porphyrins, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, phthalocyanine, copper phthalocyanine, tetra(t-butyl)copper phthalocyanine, metal or metal-free phthalocyanine compounds such as iron phthalocyanine, copper Metal or metal-free naphthalocyanine compounds such as naphthalocyanine, vanadyl naphthalocyanine, monochlorogallium naphthalocyanine, N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine, N,N , N', N'-tetraphenylbenzidine, and the like.

When the organic electroluminescence device has an electron transport layer and a hole transport layer, the average thickness of these layers is not particularly limited, but is preferably 10 to 150 nm. It is more preferably 20 to 100 nm, still more preferably 40 to 100 nm.
The average thickness of the electron-transporting layer and the hole-transporting layer can be measured with a crystal oscillator film thickness meter in the case of a low-molecular-weight compound, and with a contact-type profilometer in the case of a high-molecular-weight compound.

When the organic electroluminescent device has an electron injection layer made of an organic compound other than the metal oxide layer, examples of the material of the organic electron injection layer include polyamines and triazine ring-containing compounds. A high electron injection property can be obtained.
As the polyamines, those capable of forming a layer by coating are preferable, and they may be low-molecular compounds or high-molecular compounds. Polyalkylenepolyamines such as diethylenetriamine are preferably used as low-molecular-weight compounds, and polymers having a polyalkyleneimine structure are preferably used as high-molecular-weight compounds. Polyethyleneimine is particularly preferred.
As the triazine ring-containing compound, in addition to melamine and guanamines such as benzoguanamine/acetoguanamine, one or more compounds having a melamine/guanamine skeleton such as methylolated melamine and guanamines, and melamine/guanamine resins may be used. Among these, melamine is preferred, although it can be used.

Further, the organic electron injection layer may be a layer containing a heterocyclic compound having an amidine structure such as a diazabicyclononene derivative or a diazabicycloundecene derivative and an electron-transporting material.
Examples of diazabicyclononene derivatives include 1,5-diazabicyclo[4.3.0]nonene-5 (DBN).
Examples of diazabicycloundecene derivatives include 1,8-diazabicyclo[5.4.0]undecene-7 (DBU).
As the electron-transporting material, the above materials for the electron-transporting layer can be used.

When the organic electroluminescent device has an organic electron injection layer, the average thickness of the organic electron injection layer is not particularly limited, but is preferably 0.1 to 150 nm. It is more preferably 5 to 100 nm, still more preferably 10 to 100 nm.
The average thickness of the organic electron injection layer can be measured by a crystal oscillator film thickness meter when it is composed of a low-molecular compound, and by a contact-type profilometer when it contains a polymer compound.

When the organic electroluminescent element has a metal oxide layer, it has a metal oxide layer between the cathode and the light-emitting layer, between the anode and the light-emitting layer, or both. It is preferred to have a metal oxide layer both between the light-emitting layer and the anode. The organic electroluminescence device of the present invention, wherein the metal oxide layer between the cathode and the light-emitting layer is defined as the first metal oxide layer, and the metal oxide layer between the anode and the light-emitting layer is defined as the second metal oxide layer. An example of the configuration of a preferable element is that a cathode, a first metal oxide layer, an organic electron injection layer, a light emitting layer, a hole transport layer, a second metal oxide layer, and an anode are laminated in this order adjacent to each other. configuration. An electron transport layer may be provided between the organic electron injection layer and the light emitting layer, if necessary. The importance of the metal oxide layer is higher for the first metal oxide layer, and the second metal oxide layer can also be replaced by organic materials with extremely deep lowest unoccupied molecular orbitals, such as HATCN. .

The first metal oxide layer is a layer consisting of a single metal oxide film, or a semiconductor or insulator laminated thin film that is a layer in which single metal oxides or two or more kinds of metal oxides are laminated and/or mixed. layer. Metal elements constituting metal oxides include magnesium, calcium, strontium, barium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, indium, gallium, iron, cobalt, nickel, and copper. , zinc, cadmium, aluminum and silicon. Among these, at least one of the metal elements constituting the laminated or mixed metal oxide layer is preferably a layer composed of magnesium, aluminum, calcium, zirconium, hafnium, silicon, titanium, and zinc. If it is an oxide, it preferably contains a metal oxide selected from the group consisting of magnesium oxide, aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide, titanium oxide and zinc oxide.

Examples of the layer obtained by laminating and/or mixing single or two or more kinds of metal oxides include titanium oxide/zinc oxide, titanium oxide/magnesium oxide, titanium oxide/zirconium oxide, titanium oxide/aluminum oxide, titanium oxide/ Laminates and/or metal oxide combinations such as hafnium oxide, titanium oxide/silicon oxide, zinc oxide/magnesium oxide, zinc oxide/zirconium oxide, zinc oxide/hafnium oxide, zinc oxide/silicon oxide, calcium oxide/aluminum oxide 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, Laminated and/or mixed combinations of three kinds of metal oxides such as indium oxide/gallium oxide/zinc oxide can be used. Among these, IGZO, which is an oxide semiconductor exhibiting good characteristics as a special composition, and 12CaO.7Al ₂ O ₃ , which is an electride, are also included.
These first metal oxide layers can be called an electron injection layer and can also be called an electrode (cathode).
In the present invention, a material with a sheet resistance lower than 100Ω/□ is classified as a conductor, and a material with a sheet resistance higher than 100Ω/□ is classified as a semiconductor or an insulator. Therefore, ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped indium oxide), etc., known as transparent electrodes Since the thin film has high conductivity and is not included in the category of semiconductors or insulators, it does not correspond to one layer constituting the first metal oxide layer.

Metal oxides forming the second metal oxide layer are not particularly limited, but vanadium oxide (V ₂ O ₅ ), molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), ruthenium oxide (RuO ₂ ), etc., or two or more thereof can be used. Among these, those containing vanadium oxide or molybdenum oxide as a main component are preferable. When the second metal oxide layer is composed of vanadium oxide or molybdenum oxide as a main component, the second metal oxide layer injects holes from the anode and transports them to the light emitting layer or the hole transport layer. It is excellent because of its function as a hole injection layer. In addition, since vanadium oxide or molybdenum oxide itself has a high hole-transporting property, it has the advantage of being able to suitably prevent the efficiency of hole injection from the anode to the light-emitting layer or the hole-transporting layer from decreasing. There is More preferably, it is composed of vanadium oxide and/or molybdenum oxide.

The average thickness of the first metal oxide layer is allowable from about 1 nm to several μm, but is preferably 1 to 1000 nm from the viewpoint of making the organic electroluminescence device capable of being driven at a low voltage. More preferably, it is 2 to 100 nm.
Although the average thickness of the second metal oxide layer is not particularly limited, it is preferably 1 to 1000 nm. More preferably, it is 5 to 50 nm.
The average thickness of the first metal oxide layer can be measured by a stylus profilometer and spectroscopic ellipsometry.
The average thickness of the second metal oxide layer can be measured during film formation with a crystal oscillator film thickness meter.

The organic electroluminescence device of the present invention may have a hole injection layer made of a material other than metal oxide. Materials other than metal oxides for the hole injection layer include, for example, HAT-CN (dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11- LUMO deep, strong acceptor materials such as Hex).
The average thickness of the hole injection layer made of a material other than metal oxide is preferably the same as the average thickness of the second metal oxide layer.

In the organic electroluminescence device, known conductive materials can be appropriately used for the anode and the cathode, but at least one of them is preferably transparent for light extraction. Examples of known transparent conductive materials include ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped indium oxide), and the like. is raised. Examples of opaque conductive materials include calcium, magnesium, aluminum, tin, indium, copper, silver, gold, platinum and alloys thereof.
Among these, ITO, IZO and FTO are preferable as the cathode.
Among these, Au, Ag, and Al are preferable as the anode.
As described above, metals that are generally used for anodes can be used for the cathode and anode, so that light extraction from the upper electrode (in the case of a top emission structure) can be easily realized, and the above electrodes can be used. Various materials can be selected and used for each electrode. For example, Al is used for the lower electrode, and ITO is used for the upper electrode.

Although the average thickness of the cathode is not particularly limited, it is preferably 10 to 500 nm. More preferably, it is 100 to 200 nm. The average thickness of the cathode can be measured by a stylus profilometer and spectroscopic ellipsometry.
Although the average thickness of the anode is not particularly limited, it is preferably 10 to 1000 nm. More preferably, it is 30 to 150 nm. Even when an opaque material is used, it can be used as a top-emission type and transparent type anode, for example, by setting the average thickness to about 10 to 30 nm.
The average thickness of the anode can be measured during film formation with a crystal oscillator film thickness gauge.

In the organic electroluminescence device of the present invention, the method for forming the layer formed from the organic compound is not particularly limited, and various methods can be appropriately used according to the properties of the material. Spin coating method, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, slit coating method, dip coating method, spray coating method, screen printing method, flexographic printing method, offset A film can be formed using various coating methods such as a printing method and an inkjet printing method. Among these methods, the spin coating method and the slit coating method are preferable because the film thickness can be more easily controlled. Vacuum deposition, CVD (Chemical Vapor Deposition), ESDUS (Evaporative Spray Deposition from Ultra-dilute Solution) and the like are suitable examples when coating is not applied or solvent solubility is low.

When the layer formed from the above organic compound is formed by applying an organic compound solution, examples of the solvent used for dissolving the organic compound include nitric acid, sulfuric acid, ammonia, hydrogen peroxide, water, and carbon disulfide. , inorganic solvents such as carbon tetrachloride and ethylene carbonate, ketone solvents such as methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), cyclohexanone, methanol, ethanol, isopropanol, Alcohol solvents such as ethylene glycol, diethylene glycol (DEG) and glycerin, diethyl ether, diisopropyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, Ether solvents such as diethylene glycol dimethyl ether (diglyme) and diethylene glycol ethyl ether (carbitol); cellosolve solvents such as methyl cellosolve, ethyl cellosolve, and phenyl cellosolve; aliphatic hydrocarbon solvents such as hexane, pentane, heptane, and cyclohexane; , xylene, benzene and other aromatic hydrocarbon solvents, pyridine, pyrazine, furan, pyrrole, thiophene, methylpyrrolidone and other aromatic heterocyclic compound solvents, N,N-dimethylformamide (DMF), N,N-dimethyl Amide solvents such as acetamide (DMA), halogen compound solvents such as chlorobenzene, dichloromethane, chloroform, 1,2-dichloroethane, ester solvents such as ethyl acetate, methyl acetate, ethyl formate, dimethyl sulfoxide (DMSO), sulfolane, etc. sulfur compound solvents, acetonitrile, propionitrile, nitrile solvents such as acrylonitrile, various organic solvents such as organic acid solvents such as formic acid, acetic acid, trichloroacetic acid, trifluoroacetic acid, or mixed solvents containing these is mentioned.
Among these, nonpolar solvents are suitable as the solvent. Examples include aromatic heterocyclic compound solvents such as pyrrole, thiophene and methylpyrrolidone, and aliphatic hydrocarbon solvents such as hexane, pentane, heptane and cyclohexane, and these can be used alone or in combination.

The cathode, anode, and oxide layer can be formed by sputtering method, vacuum deposition method, sol-gel method, spray pyrolysis (SPD) method, atomic layer deposition (ALD) method, vapor deposition method, liquid deposition method, etc. can be formed by Bonding of metal foils can also be used to form the anode and cathode. These methods are preferably selected according to the characteristics of the material of each layer, and the manufacturing method may be different for each layer. Among these, the second metal oxide layer is more preferably formed using a vapor deposition method. According to the vapor-phase film-forming method, the organic compound layer can be formed cleanly and in good contact with the anode without damaging the surface of the layer. becomes more prominent.

For the purpose of further improving the characteristics of the organic electroluminescence device, for example, it may have a hole blocking layer, an electron blocking layer, or the like, if necessary. Materials commonly used for forming these layers can be used as materials for forming these layers, and the layers can be formed by methods commonly used for forming these layers.

As described above, the organic electroluminescent device of the present invention can be a simple ^sealed device or a device that does not have a ^sealed structure.・Day (1×10 ⁻⁴ g/m ² ·day) or more may be sealed, but it is easier to seal by taking advantage of the strong resistance to deterioration due to oxygen and moisture of the organic electroluminescent element of the present invention. Simple sealing with a water vapor transmission rate of 10 ⁻³ g/m ² ·day (1×10 ⁻³ g/m ² ·day) or more, and simpler sealing with a water vapor transmission rate of 10 ⁻ Sealing at ² g/m ² ·day (1×10 ⁻² g/m ² ·day) or more is a preferred embodiment of the organic electroluminescence device of the present invention.
A simple sealing method with a water vapor transmission rate of 10 ⁻⁴ g/m ² ·day or more for an organic electroluminescent element is not particularly limited, and for example, a method using a sealing film having such a water vapor transmission rate. etc. can be used.
The water vapor transmission rate of the organic electroluminescence element can be measured by the Ca corrosion method.

The organic electroluminescence device of the present invention adopts a reverse structure that is resistant to deterioration due to oxygen and moisture, and furthermore, by forming a light-emitting layer with a specific material, it is a device that is simple to seal or does not have a sealing structure. Therefore, it can be suitably used for display devices such as displays of televisions and mobile phones, and lighting devices. A display device and a lighting device comprising such an organic electroluminescent element of the present invention are also one aspect of the present invention.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited only to these examples. Unless otherwise specified, "part" means "part by weight" and "%" means "% by mass".

EXAMPLES Examples and comparative examples of the present invention will be described below, but the present invention is not limited to the examples shown below.
In the following, the organic electroluminescent device of the present invention is referred to as "Example", the organic electroluminescent device of the present invention that differs from the organic electroluminescent device of the present invention in sealing is referred to as "Reference Example", and the host material that differs from the organic electroluminescent device of the present invention is referred to as "Comparative Example". , and those that are different in terms of both encapsulation and host materials are described as "comparative reference examples."

<Example 1>
An organic electroluminescence device having the reverse structure shown in FIG. 1 was manufactured by the method described below.
[1] A commercially available glass transparent substrate (hereinafter simply referred to as a substrate) having an average thickness of 0.7 mm and having a cathode made of an ITO film (thickness: 150 nm, width: 3 mm) was prepared.
[2] Next, the substrate with the cathode was ultrasonically cleaned in acetone and isopropanol for 10 minutes each, and then boiled in isopropanol for 5 minutes. Thereafter, the substrate was taken out of the isopropanol, dried by blowing nitrogen, and subjected to UV ozone cleaning for 20 minutes.
[3] Next, the substrate having the cathode was fixed to a substrate holder in a chamber of a magnetron sputtering apparatus having a metallic zinc target. After reducing the pressure in the chamber to about 1×10 ⁻⁴ Pa, ZnO was sputtered while argon and oxygen were introduced. Thus, a zinc oxide film (electron injection layer) having a thickness of 3 nm was formed on the cathode.
[4] Next, a 1.0% by weight ethanol solution of magnesium acetate was prepared. The substrate on which the zinc oxide layer was formed was set on a spin coater, a magnesium acetate solution was dropped on the substrate, and the substrate was rotated at 1300 rpm for 60 seconds. After that, the substrate was annealed at 400° C. for 1 hour in the atmosphere to form a magnesium oxide film with a thickness of 3 nm. Through steps [3] and [4], a substrate having a first metal oxide layer laminated with a zinc oxide layer and a magnesium oxide layer was obtained.
[5] Next, a 1.0% by weight toluene solution of 2FlCz-TRZ represented by the following formula (a) and a 2.0% by weight toluene solution of DBN represented by the following formula (b) were prepared. Each solution was mixed in equal proportions to prepare a mixed solution.
After that, the substrate on which the first metal oxide layer was laminated was set on a spin coater, the mixed solution was dropped, and the substrate was rotated at 3000 rpm for 30 seconds. Further, the substrate coated with the mixed solution was annealed at 150° C. for 1 hour in a nitrogen atmosphere using a hot plate. Thus, an organic electron injection layer having an average thickness of 20 nm was formed.
[6] Next, the substrate formed up to the organic electron injection layer was fixed to a substrate holder in a chamber of a vacuum deposition apparatus. FuCz-TRZ shown in the following formula (c), Ir(mppy)3 shown in the following formula (d), HTM-081 which is a hole transport material manufactured by Chemipro Kasei Co., Ltd., HAT-CN and Al shown in the following formula (e) were placed in crucibles and set in the vapor deposition source.
[7] The pressure inside the vacuum deposition apparatus was reduced to about 1×10 ⁻⁵ Pa, and FuCz-TRZ was deposited to a thickness of 5 nm to form an electron transport layer.
[8] Thereafter, Ir(mppy)3 as a guest material and FuCz-TRZ as a host material were co-deposited to a thickness of 25 nm to form a light-emitting layer. At this time, the doping concentration of Ir(mppy)3 was set to 3% by weight with respect to the entire light emitting layer.
[9] After that, a hole transport layer was formed by forming a film of HTM-081 to a thickness of 40 nm.
Next, HAT-CN was deposited to a thickness of 10 nm to form a hole injection layer.
[10] As an upper electrode, Al was deposited to a thickness of 100 nm to form an anode.
When depositing the anode, a stainless deposition mask was used so that the deposition surface was strip-shaped with a width of 3 mm. As a result, the light emitting area of the organic EL element was set to 9 mm ² .
[11] The substrate manufactured up to [10] above was transferred to a sputtering apparatus, and SiNx having a water vapor transmission rate of 2×10 ⁻² g/m ² ·day was deposited as a sealing film to a thickness of 90 nm.
[12] A sealing film manufactured by Oike Kogyo Co., Ltd. (water vapor transmission rate: 3 × 10 ^-4 g/m ² ·day) is attached to the substrate formed up to SiNx using a thermosetting adhesive, and the organic electroluminescent device is obtained. was sealed.

<Reference example 1>
An organic electroluminescence device was produced in the same manner as in Example 1, except that can sealing was performed using counterbore glass instead of sealing using the sealing film in step [12].

<Example 2>
An organic electroluminescence device was produced in the same manner as in Example 1, except that DIC-TRZ represented by the following formula (f) was used as the host material in the formation of the light-emitting layer in step [8].

<Reference example 2>
An organic electroluminescence device was produced in the same manner as in Example 2, except that can sealing was performed using counterbore glass instead of sealing using the sealing film in step [12].

<Comparative Example 1>
An organic electroluminescence device was produced in the same manner as in Example 1, except that CBP represented by the following formula (g) was used as the host material in the formation of the light-emitting layer in step [8].

<Comparative reference example 1>
An organic electroluminescence device was produced in the same manner as in Comparative Example 1, except that can sealing was performed using counterbore glass instead of sealing using the sealing film in step [12].

<Example 3>
The step [5] of Example 1 was changed to the step [5-1], and o-PhFuCz-TRZ represented by the following formula (h) was used as the host material in the formation of the light-emitting layer in the step [8]. An organic electroluminescence device was produced in the same manner as in Example 1, except that the sealing steps [11] to [12] were not performed.
[5-1] Next, a 1.0% by weight cyclopentanone solution of 2b represented by the following formula (i) and a 1.0% by weight cyclopentanone solution of N-DMBI represented by the following formula (j) were mixed. made respectively. Each solution was mixed at a mass ratio of 9:1 to prepare a mixed solution.
After that, the substrate on which the first metal oxide layer was laminated was set on a spin coater, the mixed solution was dropped, and the substrate was rotated at 3000 rpm for 30 seconds. Further, the substrate coated with the mixed solution was annealed at 150° C. for 1 hour in a nitrogen atmosphere using a hot plate. Thus, an organic electron injection layer having an average thickness of 20 nm was formed.

<Reference example 3>
An organic electroluminescence device was produced in the same manner as in Example 3, except that can sealing was performed using counterbore glass after the step [10].

<Comparative Example 2>
An organic electroluminescence device was produced in the same manner as in Example 3, except that CBP represented by the following formula (g) was used as the host material in the formation of the light-emitting layer in step [8].

<Comparative reference example 2>
An organic electroluminescence device was produced in the same manner as in Comparative Example 2, except that can sealing was performed using counterbore glass after the step [10].

<Example 4>
An organic electroluminescence device was produced in the same manner as in Example 1, except that the step [12] was not performed.

<Reference example 4>
The same organic electroluminescence device as in Reference Example 1 was produced.

(Measurement of lifetime characteristics of organic electroluminescent device)
The organic electroluminescence devices of Examples 1 to 4, Reference Examples 1 to 4, Comparative Examples 1 and 2, and Comparative Reference Examples 1 and 2 were each driven at a constant current by an "organic EL lifetime measuring device" manufactured by EHC. The relationship between the elapsed time from the start of the and the relative luminance was investigated. Specifically, the voltage is automatically adjusted so that a constant current flows through the organic electroluminescence element, and the relative luminance is measured with respect to the elapsed time after starting driving with the constant current (luminance meter manufactured by Konica Minolta, Inc.). (LS-110)) was performed. In Examples 1, 2, and 4, Reference Examples 1, 2, and 4, Comparative Example 1, and Comparative Reference Example 1, the current value was adjusted so that the luminance at the start of measurement was 600 cd/m ² . In Reference Example 3, Comparative Example 2, and Comparative Reference Example 2, each organic electroluminescence device was set so that the luminance at the start of measurement was 1000 cd/m ² . The results are shown in FIGS.

As shown in FIGS. 2 and 3, the present invention uses FuCz-TRZ and DIC-TRZ, which are TADF materials, as hosts, respectively, and has a simple film sealing with a water vapor transmission rate of 10 ⁻⁴ g/m ² ·day or more. In the elements of Examples 1 and 2, which are organic electroluminescent elements, the decrease in luminance with elapsed time is almost the same as that of the elements of Reference Examples 1 and 2, which are glass-sealed without being affected by moisture. , and it was confirmed that the use of a TADF material as a host more effectively suppresses deterioration of luminance due to moisture in the atmosphere.
Furthermore, as shown in FIG. 5, in the element of Example 3, which used o-PhFuCz-TRZ, which is a TADF material, as a host and was not sealed, the element of Reference Example 3 with glass sealing and the elapsed time The associated decrease in brightness was almost the same. From this result, it was confirmed that the organic electroluminescence device using the TADF material as a host effectively suppresses deterioration of luminance due to moisture and the like even when it does not have a sealing structure.
Furthermore, as shown in FIG. 7, the organic material of Example 4 was sealed with SiNx having a water vapor transmission rate of 2×10 ⁻² g/m ² ·day using FuCz-TRZ, which is a TADF material, as a host. Even in the electroluminescence device, although there is a slight difference in the decrease in luminance over time from the glass-sealed device of Reference Example 4, it does not increase over time, and low-barrier sealing Also, it was confirmed that an element with little deterioration could be realized.
On the other hand, as shown in FIG. 4, the element of Comparative Example 1 using a general host material that does not correspond to the host material of the present invention is the same as the element of Comparative Reference Example 1, which is glass-sealed using the same host material. As a result, the rate of luminance deterioration was significantly different. This is significantly different from the relationship between Example 1 and Reference Example 1 and the relationship between Example 2 and Reference Example 2.
In addition, as shown in FIG. 6, in the device of Comparative Example 2 using a general host material that does not correspond to the host material of the present invention, the degradation rate of luminance was already high after a short period of time. The result was different from that of the element of Comparative Reference Example 2 which was stopped. This is different from the relationship in Example 3 and Reference Example 3.
From these results, it was confirmed that the organic electroluminescence device of the present invention is a device in which early attenuation of luminance is effectively suppressed while having excellent flexibility.

Claims (4)

An organic electroluminescence device having a structure in which a plurality of layers including a light-emitting layer are laminated between an anode and a cathode formed adjacently on a substrate,
The organic electroluminescent device has a light-emitting layer containing a host material and a light-emitting material,
The host material is a thermally activated delayed fluorescence material, has a triazine structure as an acceptor-type substituent, and has one of the following structures as a donor-type structure,

The triplet excited state of the host material generated by charge recombination can transfer energy to the light-emitting material,
An organic electroluminescence device characterized by being sealed with a water vapor transmission rate of 10 ⁻⁴ g/m ² ·day or more, or having no sealing structure. 2. The organic electroluminescence device according to claim 1, wherein the luminescent material in said luminescent layer is a phosphorescent material. A display device comprising the organic electroluminescence device according to claim 1 . A lighting device comprising the organic electroluminescence device according to claim 1 .

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